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SPARK Examiner User Manual – Release 7.3 [NT]

1. M 2 1 1 2 2 oss SPARK Examiner EXM UM User Manual Release 7 3 Issue 7 3 Alternatively it is also possible to provide an index file See section 4 2 which associates SPARK compilation units with the files which contain them If an index file is supplied the Examiner can use it to find compilation units it requires but whose locations file names have not been specified in the command line The index file is a text file that can be generated either directly by the user or by a user Supplied program It could for example be produced by the build mechanism of a configuration management tool Facilities are provided for inheriting other index information through a superindex and for subdividing index information into separate files using auxiliary indexes The Examiner checks conformance of the contents of the specified files to the rules of SPARK performing all the tests that the visibility of the text allows This analysis is performed in several passes First lexical and syntax analysis of a compilation unit is carried out allowing the Examiner to identify what other units are required to carry out the complete analysis of this compilation unit The Examiner then reads all other required units if they have not already been read When all the required units of a compilation unit have been read the Examiner performs static semantic analysis and if this is successful it goes on to perform data
2. M 8 1 8 2 8 2 1 oss SPARK Examiner EXM UM User Manual Release 7 3 Issue 7 3 Data and information flow analysis General description The data flow and information flow relations on which this analysis is based have been defined recursively in such a way that they can be computed directly in the course of a traversal of the abstract syntax tree of a SPARK text The principles of the method are described in the paper given in Appendix A though the recurrence relations used to compute the flow relations of SPARK loop structures are rather more complex Data flow and information flow errors are detected by mechanical inspection of these relations Optional information flow analysis Description This feature can be used for analysis of SPARK 95 programs where global modes have been provided The syntax for moded global annotations is described in the SPARK Definition For example procedure P X in y Yos out T global in A in out B C out D Provided global modes are present and the Examiner is operating in SPARK 95 mode data flow analysis can be selected using the flow_analysis data command line option described in Section 3 1 3 When selected the Examiner will ignore any derives annotations it encounters A note to this effect is generated but it can be suppressed if desired by using the warning file mechanism described in Section 4 3 Instead of using the derives annotation the E
3. Semantic Error 416 Type may not have an empty range Semantic Error 417 String subtypes must have a lower index bound of 1 Semantic Error 418 Index upper and or lower bounds do not match those expected Issued where assignment association or type conversion is attempted between two different constrained subtypes of the same unconstrained array type and where the index bounds do not match Semantic Error 420 Array index es not convertible Issued when an attempt is made to convert between two arrays whose indexes are neither of the same type nor numeric Semantic Error 421 Array components are not of the expected type Issued when a type conversion attempts to convert between two array types whose components are of different types Semantic Error 422 Array component constraints do not match those expected Issued when a type conversion attempts to convert between two array types whose components are of the same type but do not have constraints which can be statically determined to be identical Semantic Error 423 Array has different number of dimensions from that expected Issued when attempting to convert between two array types which have different numbers of dimensions Semantic Error 425 String literals may not be converted Issued if the argument of a type conversion is a string literal Acommon cause is an attempt to type qualify a string and accidentally omitting the tick character Semantic Error 500 Mode
4. Reserved words In addition to the reserved words of Ada certain additional words listed below are reserved words of SPARK These additional reserved words are associated with SPARK s core annotations and proof contexts assert check derives from global hide hold inherit initializes invariant main_program own post pre some In addition to these reserved words users may not use certain other identifiers which are reserved for use in FDL Functional Description Language which is the underlying logic in which theorems about SPARK programs are expressed Use of these identifiers as Ada identifiers would lead to ambiguous and badly typed VCs The predefined FDL identifiers involved are listed below A complete list of the reserved words of SPARK and FDL is also given in the SPARK Definition Note that this restriction can be avoided by use of the nofdl_identifier command line switch see Section 3 1 although doing so will prevent use of the Examiner s VC PFS and RTC generation capabilities are_interchangeable abstract as assume const div element finish first for_all for_some goal last may_be_deduced may_be_deduced_from may_be_replaced_by nonfirst nonlast not_in odd pending pred proof requires save sequence set sqr start strict_subset_of subset_of succ update var where Page 38 of 95 a SPARK Examiner EXM UM User Manual Release 7 3 Issue 7 3 M For backward compatibility with earlier definitions of the SPARK l
5. Warning 307 Completeness checking incomplete index type s undefined or not discrete Issued where the array index sub type is inappropriate this is probably because there is an error in its definition which will have been indicated by a previous error message Warning 308 Use of equality operator with floating point type The use of this operator is discouraged in SPARK because of the difficulty in determining exactly what it means to say that two instances of a floating point number are equal Warning 309 Unnecessary type conversion to own type Issued where a type conversion is either converting from a sub type to the same sub type or is converting between two subtypes of the same type In the former case the type conversion may be safely removed because no constraint check is required in the latter case the type conversion may be safely replaced by a type qualification which preserves the constraint check warning control file keyword type_conversions Warning 310 Use of obsolescent Ada 83 language feature Issued when a language feature defined by Ada 95 to be obsolescent is used Use of such features is not recommended because compiler support for them cannot be guaranteed Warning 3114 Priority pragma for XXX is unavailable and has not been considered in the ceiling priority check Page 78 of 95 SPARK Examiner EXM UM User Manual Release 7 3 Issue 7 3 Warning 312 Replacement rules cannot be built for multi
6. Flow Error 4 The dependency of the exported value of XXX on the imported value of YYY has not been previously stated A refined dependency relation states a dependency of XXX or a constituent of XXX on YYY or a constituent of YYY but in the earlier relation no dependency of XXX on YYY is stated Flow Error 5 The possibly implicit dependency of the exported value of XXX on its imported value has not been previously stated Either a dependency of a constituent of XXX on at least one constituent of XXX occurs in the refined dependency relation or not all the constituents of XXX occur as exports in the refined dependency relation However the dependency of XXX on itself does not occur in the earlier dependency relation Page 91 of 95 Dj y Ti SPARK Examiner EXM UM User Manual Release 7 3 Issue 7 3 9 Verification condition generation 9 1 General description VC generation is the generation of formulae whose proof demonstrates some property of the associated code Certain additional errors can be detected during VC generation and these are described below 9 2 Error messages The following error messages may be issued during VC generation the first one is displayed on the screen and one of the following acts as a further explanation which is placed in the VCG file WN Error s detected by VC Generator This message is echoed to the screen if an unrecoverable error occurs which makes the generation of VCs for the curre
7. Semantic Error 829 Illegal re declaration this subprogram shares the same name as the inheritable root operation XXX but does not override it To avoid overloading SPARK prohibits more than one potentially visible subprogram having the same name Semantic Error 830 A private type may not be implemented as a tagged type or an extension of a tagged type This rule means that a private type can only be implemented as a tagged type if the private type itself is tagged Semantic Error 7831 Extended tagged types may only be converted in the direction of their root type This is an Ada rule type conversions simply omit unused fields of the extended type It follows that conversions must be in the direction of the root type Semantic Error 832 Only tagged objects not expressions may be converted For flow analysis purposes the Examiner needs to know what subset of the information in the unconverted view is available in the converted view Since information can only flow through objects it follows that only objects can be converted Semantic Error 833 Invalid record aggregate type XXX has a private ancestor If an extended type has a private ancestor then an extension aggregate must be used rather than a normal aggregate Semantic Error 834 Null records are only permitted if they are tagged An empty record can have no use in a SPARK program others than as a root type from which other types can be derived and extended For this re
8. fp_literal lt a valid SPARK floating point literal gt u be Although the format of the target configuration file resembles a SPARK source file that it is not and that only items from the above grammar are allowed in particula EXM UM Issue 7 3 un yn t_expr int_expr it is important to note r the range of acceptable expressions is much more limited Standard Ada comments may also be used 4 6 2 Example The following is an example target configuration file for GNAT Pro 3 14a1 under W package Standard is in32 type Integer is range 2 31 ZENS type Short_Short_Integer is range 2 7 RER as type Short_Integer is range 2 15 2A 5H13 type Long_Integer is range 2 31 Z2 31 gt 1 type Long_Long_Integer is range 2 63 ZERO 314 type Short_Float is digits 6 range 3 40282E 38 3 40282E 38 type Float is digits 6 range 3 40282E 38 3 40282E 38 type Long_Float is digits 15 range 1 79769313486232E 308 1 79769313486232E 308 type Long_Long_Float is digits 18 range 1 18973149535723177E 4932 end Standard package System is type Address is private constant constant Storage_Unit 8 Word_Size Max_Int constant in_Int constant ax_Binary_Modulus B25 2 63 1 2 63 constant a M 2 64 ax_Base_Digits constant 18 constant 18 ax_Digits a aa 1 0842 63 constant constant Fine Delta Max_Mantissa 19 subty
9. if this does not exist the current working directory Users should ensure that they have write privileges for this location and that there is sufficient space for the temporary files to be created If desired the location where temporary files are created can be changed by changing the value of environment variable TMP HTML Output The Examiner can produce browsable HTML output files that make inspection of the Examination results much easier The output is compliant with the transitional HTML 4 0 specification and can be viewed in any HTML 4 0 browser HTML generation is invoked using the html switch described in the table at section 3 1 2 HTML generation is not an option on the VAX Files Generated In addition to the usual output the Examiner produces the following files during HTML generation spark htm This is the starting point for viewing the HTML output Page 30 of 95 M 4 8 2 SPARK Examiner EXM UM User Manual Release 7 3 Issue 7 3 spark_rep htm The HTML version of the Examiner s report file The file s name is based on the name of the report file and will change if a different report file name is used lt file gt _Ist htm For each file specified on the command line or in a meta file for Examination a listing file is produced The Examiner produces an HTML version of the listing file also The name of the HTML listing file is based on the name of the plain text listing file therefore using the listing_ex
10. 2 1 2 2 2 oss SPARK Examiner EXM UM User Manual Release 7 3 Issue 7 3 flow errors from code before generating VCs such errors should of course be considered for significance and acceptability Output files When VC generation is selected for each subprogram in the files specified on the Examiner command line the following additional output files are generated They contain the FDL type declarations needed if the SAS or Proof Checker are to be used the results of the selected analysis and associated proof rules The file extensions of these output files are as follows File Extension FDL Declarations fdl Analysis cg Rules ls The naming of these output files is covered in more detail in section 4 7 Relationship with the SPADE tools The verification condition VC files produced by the Examiner can be manipulated by the SPADE tools VCs can be simplified by the SPADE Automatic Simplifier and the proof of VCs too complex for automatic proof by the Simplifier can be attempted using the SPADE Proof Checker The POGS tool provides a summary of VCs indicating their source and current proof status Fig 1 overleaf gives an overview of the relationship between these four tools and the input and output files used to connect them Page 9 of 95 TH SPARK Examiner EXM UM User Manual Release 7 3 Issue 7 3 SPARKSource SPARKMake Code Files SPARKFormat WarningFile wrn Switch File sw TargetConfiguration File
11. 399 Range error in annotation expression Issued if a proof annotation contains an expression that would cause a constraint error if it were in an executable Ada statement For example post X T Succ T Last VCs generated from such malformed predicates would always be unprovable Semantic Error 400 Expression contains division by zero Issued when a static expression evaluated using perfect arithmetic is found to contain a division by zero Semantic Error 401 Illegal numeric literal Issued when a numeric literal is illegal because it contains for example digits not compatible with its number base Semantic Error 402 Constraint_Error will be raised here Issued whenever a static expression would cause a constraint error e g assigning a value to a constant outside the constant s type range In SPARK a static expression may not yield a value which violates a range constraint Semantic Error 403 Argument value is inconsistent with the number of dimensions of array type XXX Issued when an array attribute containing an argument is found and the value of the argument is inconsistent with the number of dimensions of the array type to which it is being applied Semantic Error 406 Only scalar or non tagged record subtypes may be declared without a constraint Issued if a subtype declaration of the form subtype S is T is used where T is not a scalar or non tagged record type Secondly T must not be private at the point
12. Error 38 Expression is not of the expected type Semantic Error 39 Illegal use of unconstrained type Page 42 of 95 KKK KKK KKK KKK KKK KKK KKK KKK KKK KKK KKK KKK KKK KKK KKK KKK KKK KKK SPARK Examiner EXM UM User Manual Release 7 3 Issue 7 3 An unconstrained array type or variable of such a type is illegally used Use of unconstrained arrays in SPARK is limited to passing them as parameters indexing into them and taking attributes of them This message also arises if a string literal is used as an actual parameter where the formal parameter is a string subtype In this case the error can be removed by qualifying the string literal with the subtype name Semantic Error 40 Numeric or Time_Span type required This operator is only defined for numeric types and if the Ravenscar Profile is selected for type Ada Real_Time Time_Span Semantic Error 41 Array type required Issued if a subtype declaration taking the form of a constrained subtype of an unconstrained array type is encountered but with a type mark which does not represent an array Semantic Error 42 Incompatible types Issued when a name represents an object which is not of the required type Semantic Error 43 Range is not constant Semantic Error 44 Scalar type required The bounds of an explicit range must be scalar types Semantic Error 45 Range is not static Semantic Error 46 Discrete type required Sem
13. SPARK Examiner EXM UM User Manual Release 7 3 8 3 5 8 3 6 Issue 7 3 The variable XXX which appears in the dependency relation of a procedure subprogram as an import from which the export YYY is derived is not used in the code for that purpose YYY may be a function return value This version of the message has been retained for backward compatibility The following kinds of messages are used to report dependencies found in the code of a subprogram which do not appear in its specified dependency relation These are conditional errors only the dependencies found in the code may be attributable to paths that are not executable Warning 601 YYY may be derived from the imported value s of XXX Here the item on the left of may be derived from is an exported variable and the item s on the right are imports of a procedure subprogram The message reports a possible dependency found in the code which does not appear in the specified dependency relation derives annotation The discrepancy could be caused by an error in the subprogram code which implements an unintended dependency It could also be in an error in the subprogram derives annotation which omits a necessary and intended dependency Finally the Examiner may be reporting a false coupling between two items resulting from a non executable code path or the sharing of disjoint parts of structured or abstract data e g one variable writing to one element of an array and
14. a default switch file as an alternative to placing the above switches on the Examiner s command line each time it is invoked When run the Examiner checks for the presence of a file called Spark sw in the current working directory If a file of this name is found its contents are Page 16 of 95 ss SPARK Examiner EXM UM User Manual Release 7 3 Issue 7 3 M interpreted exactly as if they had been typed at the start of the command line Switches in the default switch file may be entered in free format and the file may include Ada style comments For example Default switch file for backward compatibility with a Standard SPARK 83 Examiner ada83 select SPARK 83 nofdl ignore use of FDL identifiers end of fil When the Examiner finds and uses a default switch file it reports this in both its screen echo messages and in the report file For convenience when working in a mixed platform environment the Solaris switch character may be used in default switch files for any platform The Examiner will not allow you to specify duplicate or contradictory options e g both statistics and nostatistics This holds true whether the options are both specified on the command line or the switch file or a combination of the two The one exception to this rule is the combination of warn and nowarn which can be used to override each other The Examiner will process whichever one is specified
15. an instantiation of Unchecked_Conversion returning a type for which run time checks are not generated Users must take steps to ensure the validity of the returned value See ALRM 13 9 The use of Unchecked_Conversion can result in invalid values being returned The function should be used with great care especially as in this case where the type returned does not generate Ada run time checks nor SPARK run time verification conditions For such types this warning is the ONLY reminder the Examiner generates that the generated value may have an invalid representation For this reason the warning is NOT supressed by the warning control file keyword unchecked_conversion The principal use of Unchecked_Conversion is SPARK programs is the for the reading of external ports prior to performing a validity check here the suppression of contraint checking prior to validation is useful Warning 169 Direct update of own variable of a non enclosing package With the publication of Edition 3 1 of the SPARK Definition the previous restriction prohibiting the direct updating of own variables of non enclosing packages was removed however the preferred use of packages as abstract state machines is compromised by such action which is therefore discouraged warning control file keyword direct_updates Warning 200 This static expression cannot be evaluated by the Examiner Issued if a static expression exceeds the internal limits of the Examiner because its
16. and information flow analyses Output files The Examiner produces a listing file for each source file specified on the command line This listing file has the same name as the source file but with the default file type Ist It contains messages indicating the success of the analysis of each subprogram or if an analysis is unsuccessful indications of the errors found A single analysis report file is also produced This lists the source files read the compilation units contained within those source files and all errors found during the analysis The report file and each listing file are terminated with a line reading End of fil Asimilar line terminates the screen echo The Examiner can optionally produce report and listing files in HTML allowing them to be browsed using any Web Browser see Section 4 8 Verification Conditions and Run time Checks If any of the Verification Condition VC options have been selected by the user the Examiner will after performing the analyses described in the previous section produce VCs for each well formed subprogram in the files specified for analysis It is recommended that VC generation is not attempted until the source text is free of SPARK semantic errors this is because their generation takes additional time and the contents of the output files produced are unlikely to be valid unless the source is legal SPARK It is not necessary to eliminate all Page 8 of 95 M 2
17. and the ceiling priorities of all protected objects that it is executing The active priority at the point of a call to a protected operation must not exceed the ceiling priority of the callee Semantic Error 935 The own variable XXX must have the interrupt property An own variable has been declared using a protected type with a pragma attach handler Such objects are used in interrupt processing and must have the interrupt property specified in their own variable declaration Semantic Error 936 The interrupt property is not allowed for XXX The interrupt property can only be applied to protected own variables that are type announced If the type is declared then it must be a protected type that contains an attach handler Semantic Error 937 The protects property is not allowed for XXX The protects property can only be applied to protected own variables that are type announced If the type is declared then it must be a protected type Semantic Error 938 The unprotected variable XXX is shared by YYY and ZZZ XXX is an unprotected variable that appears in the global list of the threads YYY and ZZZ Unprotected variables cannot be shared between threads in SPARK A thread is one of the main program a task an interrupt handler Semantic Error 939 The suspendable item XXX is referenced by YYY and ZZZ XXX is an own variable with the suspends property that appears in the suspends list of the threads YYY and ZZZ SPARK prohibits this t
18. could be used in a manner that changes the meaning of a program in ways that the Examiner could not detect For example representation clauses could be used to cause two variables to overlap so that changing one also changed the other The warnings generated are listed in sections Error Reference source not found and Error Reference source not found The warning control file which is a text file whose default extension is wrn provides a flexible means of selecting how these warnings will be displayed By default they are indicated in exactly the same way as errors with a message and location pointer appearing in both report and listing file Entries in the warning control file allow individual categories of warnings including pragmas selected by name to be reported instead in a summary form where just the number of each found is appended to the report and listing file The mechanism allows for example innocuous pragmas such as Page to be ignored while continuing to flag more serious ones Comments can be included in the warning control file using the normal Ada syntax File format Warning control file Warning entry Warning entry Keyword Pragma selection Pragma selection pragma all pragma pragma identifier The keywords to be used to suppress the individual warnings are given with the corresponding warning messages in sections Error Reference source not found and Error Reference source not found Sh
19. described in section 4 6 noconfig_file noc v Suppresses the use of the target configuration file Page 12 of 95 a SPARK Examiner EXM UM User Manual Release 7 3 Issue 7 3 M 3 1 2 Output File Options Ist listing_extension l file type Allows the user to specify a default extension for listing files The _ character may be used as a wild card in the listing extension specified by this switch This character has the effect of preserving a character from the original source file extension For example given source files p ads and p adb with listing_extension 1s_ we would generate listing files p 1ss and p lsb report_file rep file spec spark rep This specifies the report file name The format of the report file is described in section 4 1 The default extension rep is applied if no extension is given noreport_file Suppresses the production of the report file ht dirname Enables generation of HTML output files in addition to plain text output HTML is the default directory name if none is given This option cannot be used with the noreport_file option Coes NT and Sun Causes VC files to be produced in the directory tree structure described in section 4 7 1 concatenate conc VAX Causes VC files to be produced in the flat file structure described in section 4 7 2 plain_output pl Causes report and listing files to be produced without line numbers error numbers cross reference
20. dimensional array constant XXX Issued when a VC or PF references a multi dimensional array constant Can be worked round by using arrays of arrays Warning 313 The constant XXX has semantic errors in its initializing expression or has a hidden completion which prevent generation of a replacement rule Issued when replacement rules are requested for a composite constant which had semantic errors in its initializing expression or is a deferred constant whose completion is hidden from the Examiner Semantic errors must be eliminated before replacement rules can be generated Warning 314 The constant XXX has semantic errors in its type which prevent generation of rules Issued when an attempt is made to generate type deduction rules for a constant which has semantic errors in its type These semantic errors must be eliminated before type deduction rules can be generated Warning 350 Unexpected pragma Import Variable XXX is not identified as an external stream variable The presence of a pragma Import makes it possible that the variable is connected to some external device The behaviour of such variables is best captured by making them moded own variables or stream variables If variables connected to the external environment are treated as if they are normal program variables then misleading analysis results are inevitable The use of pragma Import on local variables of subprograms is particularly deprecated The warning may safely be
21. disregarded if the variable is not associated with memory mapped input output or if the variable concerned is an own variable and the operations on it are suitably annotated to indicate volatile stream like behaviour Where pragma Import is used it is essential that the variable is properly initialized at the point from which it is imported warning control file keyword imported_objects Warning 351 Unexpected address clause XXX is a constant Great care is needed when attaching an address clause to a constant The use of such a clause is safe if and only if the address supplied provides a valid value for the constant which does not vary during the execution life of the program for example mapping the constant to PROM data If the address clause causes the constant to have a value which may alter or worse change dynamically under the influence of some device external to the program then misleading or incorrect analysis is certain to result If the intention is to create an input port of some kind then a constant should not be used Instead a moded own variable or stream variables should be used warning control file keyword address_clauses Warning 390 This generic subprogram has semantic errors in its declaration which prevent instantiations of it Issued to inform the user that a generic subprogram instantiation cannot be completed because of earlier errors in the generic declaration Warning 391 If the identifier XXX ep
22. extension per package but not both This rule prevents the declaration of illegal operations with more than one controlling parameter Page 65 of 95 KKK KKK KKK KKK KKK KKK KKK KKK KKK KKK KKK KKK KKK KKK SPARK Examiner EXM UM User Manual Release 7 3 Issue 7 3 Semantic Error 840 A tagged or extended type may not appear here SPARK does not permit the declaration of primitive functions with controlling results A primitive function controlled by its return result would be almost unusable in SPARK because a data flow error would occur wherever it was used Semantic Error 841 The return type in the declaration of this function contained an error It is not possible to check the validity of this return type Issued when there is an error in the return type on a function s initial declaration In this situation we cannot be sure what return type is expected in the function s body It would be misleading to simply report a type mismatch since the types might match perfectly and both be wrong Instead the Examiner reports the above error and refuses to analyse the function body until its specification is corrected Semantic Error 842 Pragma Atomic_Components is not permitted in SPARK when the Ravenscar profile is selected Semantic Error 843 Pragma Volatile_Components is not permitted in SPARK when the Ravenscar profile is selected Semantic Error 850 This construct may only be used when the Rave
23. file Argument list Argument list Argument Argument Argument File spec Argument option Meta file spec Argument option listing_file file spec nolisting_file Meta file spec file spec Note that the format for the arguments is exactly as on the command line except that here they may be separated by line breaks Note also that meta files can be nested For convenience in multi platform environments argument options may optionally be introduced with the Solaris switch character on all platforms Example of using a meta file A meta file could be used as an alternative to an index file to specify common sets of files to be analysed The following hypothetical example would cause the Examiner to process the files specified in common smf followed by those in myunit smf and then main_ ada and main ada again note that file names are case sensitive on Unix systems It would not produce listing files for any of the files specified in common smf but would produce listings with the extension Ist for all the other files spark common smf myunit smf main_ ada main ada common smf constants_ ada nolisting io_ ada nolisting library_ ada nolisting myunit smf stack_ ada queue_ ada The target compiler data file This file allows various implementation dependent values to be supplied to the Examiner The availability of these makes significant improvements to the generation and discharge
24. has been refined and may not appear here Page 50 of 95 KKK KKK KKK KKK KKK KKK KKK KKK KKK KKK KKK SPARK Examiner EXM UM User Manual Release 7 3 Issue 7 3 Issued if an attempt is made to use in a second annotation an own variable which has been refined Second annotations should use the appropriate refinement constituents of the own variable Semantic Error 31 5 Unsupported proof context Certain proof contexts have been included in the syntax of SPARK but are not yet supported this error message results if one is found Semantic Error 317 Tilde in a function return annotation may only be applied to an external variable of mode IN The tilde decoration indicates the initial value of a variable or parameter which is both imported and exported A function may not have an explicit side effect on a program variable and so cannot be regarded as exporting suhc a variable For modelling purposes a read of an external stream variable is regarded as having a side effect outside the SPARK boundary Since it may be necessary to refer to the initial value of the external variable before this implicit side effect occurs the use of tilde is allowed only for external variables of mode IN which are globally referenced by function Semantic Error 318 Tilde or Percent may only be applied to variables The tilde decoration indicates the initial value of a variable or parameter which is both imported and
25. hence must appear in a declare annotation for the enclosing unit Semantic Error 914 The name XXX specified in the suspends list can never be called You have specified the name of a protected or suspension object in the suspends list that can never be called by this procedure or task Semantic Error 915 Procedure XXX has a delay property but cannot delay You have specified a delay property for this procedure but delay until can never be called from it Page 70 of 95 KKK KKK KKK KKK KKK KKK KKK KKK KKK KKK KKK KKK KKK KKK KKK SPARK Examiner EXM UM User Manual Release 7 3 Issue 7 3 Semantic Error 1916 Protected object XXX has a circular dependency in subprogram YYY The type of the protected object mentions the protected object name in the derives list for the given subprogram Semantic Error 917 Procedure XXX cannot be called from a protected action The procedure being called may block and hence cannot be called from a protected action Semantic Error 918 The delay property is not allowed for XXX The delay property may only be applied to a procedure Semantic Error 919 The priority property is not allowed for XXX The priority property can only be applied to protected own variables which are type announced If the type has been declared it must be a protected type Semantic Error 920 The suspends property is not allowed for XXX The suspends property may only be applied to t
26. identifier does not match the name or label originally given Page 43 of 95 KKK KKK KKK KKK KKK KKK KKK KKK KKK KKK KKK KKK KKK KKK KKK KKK KKK SPARK Examiner EXM UM User Manual Release 7 3 Issue 7 3 Semantic Error 59 Composite subtype definition may not have associated range constraint A subtype of the form applicable to a subrange of a scalar type has been encountered but the type provided is not a scalar type Semantic Error 60 Illegal choice in record aggregate In SPARK record aggregates may not contain multiple choices each field must be assigned a value individually Semantic Error 61 Illegal occurrence of body stub a body stub may only occur in a compilation unit Semantic Error 62 A body for the embedded package XXX is required Issued if an embedded package declares subprograms or own variables and no body is provided Semantic Error 63 XXX is not a type mark Semantic Error 64 Parameters of function subprograms must be of mode in Semantic Error 65 Formal parameters of renamed operators may not be renamed The names of the parameters used in renaming declarations may not be altered from Left Right for binary operators and Right for unary operators These are the names given for the parameters in the ARM and the SPARK Definition requires that parameter names are not changed Semantic Error 66 Unexpected package initialization no own variables of packa
27. initialised is non deterministic under a concurrent elaboration policy In this case SPARK forces the task to perform the initialisation and as such the own variable must not appear in an initializes clause Semantic Error 960 The function Ada Real_Time Clock can only be used directly 1 in an assignment or return statement or 2 to initialise a library a level constant e To avoid ordering effects functions which globally access own variables which have modes indicating that they are connected to the external environment may only appear directly in assignment or return statements They may not appear as actual parameters or in any other form of expression e SPARK relaxes the illegal use of function calls in elaboration code in the case of the function Ada Real_Time Clock However the function can only be used to directly initialise a constant value Semantic Error 961 This property value is of an incorrect format Please check the user manual for valid property value formats Semantic Error 986 A protected function may not call a locally declared protected procedure See LRM 9 5 1 2 A protected function has read access to the protected elements of the type whereas the called procedure has read write access There is no way in which an Ada compiler can determine whether the procedure will illegally update the protected state or not so the call is prohibited by the rules of Ada Of course in SPARK we know there is no function si
28. invalid representation and is of a type for which run time checks are not generated Users must take steps to ensure the validity of the assigned or returned value Where values are read from external variables i e variables connected to the external environment there is no guarantee that the bit pattern read will be a valid representation for the type of the external variable Unexpected behaviour may result if invalid values are used in expressions Where as in this case the type is one for which neither Ada run time checks nor SPARK run time verification conditions are generated extra care is required For such types this warning is the ONLY reminder the Examiner generates that the external value may have an invalid representation For this reason the warning is NOT supressed by the warning control file keyword external_assignment For SPARK 95 the use of attribute Valid is strongly recommended see ALRM 13 9 2 For SPARK 83 external variables should always be read into variables of a type for which any bit pattern would be a valid representation e g a word and then range checked before conversion to the actual type desired Note that when the Examiner is used to generate run time checks it will not be possible to discharge those involving external variables unless these steps are taken Boolean external variables require special care since the Examiner does not generate run time checks for Boolean variables use of Valid is essential w
29. may used explicitly provided package System has been defined in the configuration file Semantic Error 877 Priority values require an argument which is an expression of type integer Semantic Error 878 This protected type declaration contains a pragma Attach_Handler and must therefore also include a pragma Interrupt_Priority To allow the static detetion of certain bounded errors defined by the Ravenscar profile SPARK requires an explicitly set priority for each protected type or object The System Default_Priority may used explicitly provided package System has been defined in the configuration file Semantic Error 879 Unexpected pragma XXX this pragma may not appear here pragma Interrupt_Priority must be the first item in a protected type declaration or task type declaration pragma Priority must be the first item in a protected type declaration task type declaration or the main program Semantic Error 880 Pragma Priority or Interrupt_Priority expected here Issued when a pragma other than Priority or Interrupt_Priority appears as the first item in a protected type or task type declaration Semantic Error 881 The priority of XXX must be in the range YYY See LRM D 1 17 Semantic Error 882 Integrity property requires an argument which is an expression of type Natural Semantic Error 883 Pragma Interrupt_Handler may not be used SPARK does not support the dynamic attachment of interrupt handlers LRM C3 1 9 Interr
30. of the Examiner with larger internal tables Monitoring this statistics list may help to predict when this is about to occur information from this list may be requested by Praxis High Integrity Systems if we need to tailor an Examiner with especially large tables for a particular customer This information is only produced if the statistics option is selected The tables are the relation table which is used to construct the flow relations for each subprogram e the string table which is used to store the identifiers and strings found in the source text e the symbol table which stores the information about each object declared by the program e the syntax tree which stores a symbolic representation of each unit which is examined e the VCG heap which is used in the generation of Verification Conditions e the Record components table which is used to perform flow analysis of record fields e the Record errors table which is used in reporting and merging flow errors associated with record fields References Where the messages produced by the Examiner refer to external documentation this section gives a list of the abbreviations used The index file The index file associates compilation units with the files that contain them The index file is a text file whose default extension is idx Index file Superindex Index entry Super index superindex is in file spec Page 19 of 95 TH SPARK Examiner E
31. only rename subprograms in package XXX A renaming declaration may be placed immediately after the declaration of an embedded package in this case it may only rename subprograms declared in that package Semantic Error 302 The subprogram specification in this renaming declaration is not consistent with the declaration of subprogram XXX Issued in a subprogram renaming declaration if it contains parameter names numbers or types which differ from those originally declared Semantic Error 303 An operator can only be renamed by the same operator Issued if a renaming declaration has a different operator on each side of the reserved word RENAMES Semantic Error 304 A renaming declaration for operator XXX is not allowed Semantic Error 305 The specification in this renaming declaration is not consistent with the implicit declaration of operator XXX Issued in an operator renaming declaration if it contains types which differ from those applicable to the operator being renamed Semantic Error 306 Operator XXX is already visible Occurs in an operator renaming declaration if an attempt is made to rename an operator which is already visible The message will also appear as a secondary consequence of trying to rename an operator between undeclared types Semantic Error 307 The implicit declaration of this operator does not occur in package XXX Semantic Error 308 Type is limited Issued if an attempt is made to assign a vari
32. package in the target configuration file is not allowed in SPARK83 mode In SPARK83 mode only package Standard may be specified in the target configuration file Semantic Error 780 Type XXX must be private This type may only be declared as private in the target configuration file Semantic Error 781 The lower bound of a signed integer type declaration must be greater than or equal to System Min_lInt This error can only be generated in SPARK95 mode when the configuration file specifies a value for System Min_Int Semantic Error 782 The upper bound of a signed integer type declaration must be less than or equal to System Max_Int This error can only be generated in SPARK95 mode when the configuration file specifies a value for System Max_Int Page 62 of 95 KKK KKK KKK KKK KKK KKK KKK KKK KKK KKK KKK KKK KKK KKK KKK KKK KKK KKK KKK SPARK Examiner EXM UM User Manual Release 7 3 Issue 7 3 Semantic Error 783 Modulus must be less than or equal to System Max_Binary_Modulus This error can only be generated in SPARK95 mode when the configuration file specifies a value for System Max_Binary_Modulus Semantic Error 784 System Max_Binary_Modulus must be a positive power of 2 Semantic Error 785 The number of digits specified exceeds the value defined for System Max_Digits The maximum decimal precision for a floating point type where a range specification has not been included is defi
33. refinement constituent that announced it would exist Semantic Error 704 Own variable XXX may not have a mode because one was not present in its earlier announcement Issued if an own variable of an embedded package is given a mode when the earlier refinement constituent that announced it would exist did not have one Page 58 of 95 KKK KKK KKK KKK KKK KKK KKK KKK KKK KKK KKK SPARK Examiner EXM UM User Manual Release 7 3 Issue 7 3 Semantic Error 705 Refinement constituent XXX must be given the mode in to match the child package own variable with which it is being associated If a refinement constituent is an own variable of a private package then the constituent must have the same mode as the own variable to which it refers Semantic Error 706 Refinement constituent XXX must be given the mode out to match the child package own variable with which it is being associated If a refinement constituent is an own variable of a private package then the constituent must have the same mode as the own variable to which it refers Semantic Error 707 Refinement constituent XXX may not have a mode because one was not present on the child package own variable with which it is being associated If a refinement constituent is an own variable of a private package then the constituent can only be given a mode if the own variable to which it refers has one Semantic Error 708 Own variable XXX has a mode and may no
34. stream variable The presence of an address clause makes it possible that the variable is connected to some external device The behaviour of such variables is best captured by making them moded own variables or stream variables If variables connected to the external environment are treated as if they are normal program variables then misleading analysis results are inevitable The use of address clauses on local variables of subprograms is particularly deprecated The warning may safely be disregarded if the variable is not associated with memory mapped input output or if the variable concerned is an own variable and the operations on it are suitably annotated to indicate volatile stream like behaviour warning control file keyword address_clauses Page 80 of 95 SPARK Examiner EXM UM User Manual Release 7 3 Issue 7 3 Warning 397 Variables of type XXX can never be initialized before use A variable of a private type can only be used without generating a data flow error if there is some way of giving it an initial value For a limited private type only a procedure that has an export of that type and no imports of that type is suitable For a private type either a procedure function or deferred constant is required Warning 398 The own variable XXX can never be initialized before use The own variable can only be used without generating a data flow error if there is some way of giving it an initial value If it is initial
35. 5 M 4 2 1 4 2 2 ss SPARK Examiner EXM UM User Manual Release 7 3 Issue 7 3 SPARK 95 child components The description above covers aspects of the index file mechanism applicable to both SPARK 83 and SPARK 95 The introduction of child packages in SPARK 95 requires certain extensions to the contents of index files Unit names that represent children are expressed in the normal way for example Autopilot Altitude specification is in altitude_ states that the specification of package Altitude a child of package Autopilot is in the file named altitude_ ada The model of private child packages in SPARK is that they behave rather like embedded packages and so their own variables must appear as refinement constituents in the parent body Private children are thus regarded as components of their parent In the general case this rule also extends to the public descendants of private children Therefore before any package body is examined the specifications of any private children of the package and any public descendants of those children must first be examined So that the Examiner can locate these other packages without the user providing them explicitly on the command line a new form of index file entry has been introduced which states the names of the components of a given package This new form of entry is described as a Component entry in the earlier grammar For example Autopilot components are Auto
36. 5 49 35 L inese are links to Tiles default switek tile used Thank nen linda tn ftlan index 21 les TEST I marnirg 24 19 AL0 ORN is file i a This file is on a Latget compi ler dava C ATEST TD Link uneveliable source extension ADA iisting_extension LST nedictionarcr Tepere _TilewSPAaRe PEF besi BOESCTALI3TtICS fdl identifiers flov _analysis iofocmation mias pragma sil cr Figure 3 File links different device and is marked as unavailable ay Lend wtearal aire EXM UM Issue 7 3 The Selected Files Index Filename s and Meta Files sections of the report file contain links to the files that are referenced The Source Filename s section also contains links to the source files that are referenced Alongside there are links to the analysis sections of the report file Clicking on View analysis will take you to the report of the analysis of that file See figure 3 Page 33 of 95 TH SPARK Examiner EXM UM User Manual Release 7 3 4 8 2 3 4 8 2 4 Issue 7 3 SPARE HTML Dutput Micsosot Inteimut Exphora ga agy Hasso Ades E H OAH TL snak nin Source Filenane s vaad were This link takes you to the ETAL EXAMPLES EXOSO6E A View anal yeis HS ETAL AMPLE EXOSO6E ADA View analy report of the analysis Source Filename H HTML EXAMPLE i Listing Filename HTML EXAMPLE O6E L5T view Arm Unit seme P Unit
37. 83 programs NC rt flow_analysis This option is no longer supported for further assistance please contact Praxis High Integrity Systems Causes the Examiner to produce VCs to show that each well formed subprogram meets its postcondition and VCs associated with the Ada checks index check range check and division check Causes the Examiner to produce run time checks for real numbers float and fixed Note that this option is not enabled by default Please contact Praxis High eo oF ae realrtcs rea Integrity Systems if you wish to make use of this feature rules tu policy none The policies are none lazy keen and all and may be abbreviated to n T K and a respectively This option defines the policy applied by the Examiner to replacement rule generation for composite constants noduration nodu Causes the Examiner to not know anything about the predefined type Standard Duration This allow programs to use duration as an identifier Page 14 of 95 TH SPARK Examiner EXM UM User Manual Release 7 3 Issue 7 3 exp_checks Causes the Examiner to produce all the VCs produced by the rtc switch and VCs associated with the Ada overflow check Causes the Examiner to generate an obsolescent form of semantic analysis output called path functions Path function generation is described in the manual Generation of path functions for SPARK programs profile pr
38. Figure 1 CFR 992 Issue 2 12 19th March 2002 Added Help command line option Issue 2 13 15th May 2002 Modular subtypes are allowed do remove error 802 Issue 3 0 3rd July 2002 Updated after review for Release 6 1 Issue 3 1 30th September 2002 Updated semantic error message list and minor details to match 6 2 Examiner changed document title to 6 2 Examiner Page 94 of 95 Dj y TH SPARK Examiner EXM UM User Manual Release 7 3 Issue 7 3 Issue 3 2 19th November 2002 Update title for Examiner 6 3 No other changes Issue 4 0 15th April 2003 Updated to new template format Issue 5 0 5th June 2003 Changes to new template final format Issue 5 1 17th February 2004 Add brief command line switch Issue 5 2 17th May 2004 Allow record subtypes Issue 5 3 24th August 2004 Update documentation of html switch Issue 5 4 2nd November 2004 Add rules command line switch and changed company name Issue 5 5 6th December 2004 Change to error messages 50 and 601 addition of original_flow_errors switch Issue 5 6 9th December 2004 Removed vcg switch from options Issue 5 7 17th December 2004 Regenerated error messages Issue 5 8 4th January 2005 Definitive issue following review S PO468 79 88 Issue 5 9 5th July 2005 New warning 9 for hidden exception handlers Issue 6 0 LOth August 2005 Include warning control keyword for semantic notes 3 and 4 Issue 6 1 14th November 2005 Updated foll
39. KKK KKK KKK KKK KKK KKK KKK KKK KKK SPARK Examiner EXM UM User Manual Release 7 3 Issue 7 3 Semantic Error 1 The identifier YYY XXX is either undeclared or not visible at this point Semantic Error 2 XXX does not denote a formal parameter for YYY Semantic Error 3 Incorrect number of actual parameters for call of subprogram XXX Semantic Error 4 More than one parameter association is given for formal parameter XXX Semantic Error 5 Illegal use of identifier XXX Usually associated with the use of an identifier other than a package name as a prefix in a selected component Semantic Error 6 Identifier XXX is not the name of a variable Semantic Error 7 Identifier XXX is not the name of a procedure Semantic Error 8 There is no field named XXX in this entity Issued when the selector in a selected component of a record references a non existent field Semantic Error 9 Selected components are not allowed for XXX Occurs if the prefix to a selected component representing a procedure in a procedure call statement or a type mark is not a package Also occurs if a selector is applied in an expression to an object which is not a record variable Semantic Error 10 Illegal redeclaration of identifier XXX Semantic Error 11 There is no package declaration for XXX Issued if a package body is encountered for which there is no package specification Semantic Error 13 A body for subprogram XXX has already been d
40. KKK KKK KKK KKK KKK KKK KKK KKK KKK KKK KKK KKK SPARK Examiner EXM UM User Manual Release 7 3 Issue 7 3 Issued if an Ada declaration is given for an own variable which has been refined or in a refinement clause if an own variable is refined more than once Semantic Error 74 XXX does not occur in the package own variable list A subject of a refinement definition of a package must be an own variable of that package Semantic Error 75 Illegal use of inherited package Issued if an attempt is made to refine an own variable onto an own variable of a non embedded package Semantic Error 76 Identifier XXX is already declared and cannot be the name of an embedded package Issued when a refinement clause in a package body attempts to name an embedded package own variable as a refinement constituent and the name given for the embedded package is already in use Semantic Error 77 Variable XXX should occur in this own variable clause Occurs in the own variable clause of a package embedded in another package if an own variable which is a refinement constituent of an own variable of the enclosing package is omitted Semantic Error 78 Initialization of own variable XXX is ineffective Issued if an own variable occurs in the initialization clause of an embedded package and the own variable concerned is a refinement constituent of another own variable which is not listed in the initialization specification of its pa
41. M 13 3 48 Semantic Error 255 The Address attribute can only be specified for a variable a constant or a program unit Ada95 LRM Annex N 31 defines a program unit to be either a package a task unit a protected unit a protected entry a generic unit or an explicitly declared subprogram other than an enumeration literal Semantic Error 273 Own variable XXX may not be refined because it was declared with a type mark which has not subsequently been declared as an abstract proof type Where a type mark is included in an own variable declaration it indicates that the own variable will either be of a concrete type of that name which may be either already declared or be declared later in the package or of an abstract proof type declared in the package specification In the former case the refinement is illegal because own variables of concrete Ada types may not be refined In the latter case it is legal however no suitable proof type declaration has been found in this case Semantic Error 300 Renaming declarations are not allowed here A renaming declaration must be the first declarative item of a package body or main program or it must be placed immediately after the declaration of an embedded package Page 49 of 95 KKK KKK KKK KKK KKK KKK KKK KKK KKK KKK KKK KKK KKK KKK SPARK Examiner EXM UM User Manual Release 7 3 Issue 7 3 Semantic Error 7301 Renaming or use type declarations here can
42. Ravenscar profile SPARK requires every visible operation of protected type to globally reference the abstract state of the type Semantic Error 874 Protected state XXX must be initialized at declaration Because there is no guarantee that a concurrent thread that initializes a protected object will be executed before one that reads it the only way we can be sure that a protected object is properly initialized is to do so at the point of declaration You have either declared some protected state and not included an initialisation or you have tried to initialise some protected state in package body elaboration Semantic Error 875 Protected type expected access discriminants may only refer to protected types in SPARK Page 67 of 95 KKK KKK KKK KKK KKK KKK KKK KKK KKK KKK KKK KKK KKK SPARK Examiner EXM UM User Manual Release 7 3 Issue 7 3 Access discriminants have been allowed in SPARK solely to allow devices made up of co operating Ravenscar compliant units to be constructed For this reason only protected types may appear in access discriminants Semantic Error 876 This protected type or task declaration must include either a pragma Priority or pragma Interrupt_Priority To allow the static detection of certain bounded errors defined by the Ravenscar profile SPARK requires an explicitly set priority for each protected type task type or object of those types The System Default_Priority
43. XM UM User Manual Release 7 3 Issue 7 3 Index entry File entry Component entry File entry Unit name Entry Type is in file spec Entry type auxindex main_program specification body subunit Unit name Ada unit name Component entry Unit name components are Unit name Unit name Tokens i e Ada unit names file specs the words superindex auxindex main_program specification body subunit is and in may not contain spaces or line breaks Tokens may be separated by any number of spaces tabs and or line breaks This means that an index entry may be broken over any number of lines and blank lines are ignored Comments begin with and are terminated by a line break A comment is treated as though it were a line break Hence comments may be placed anywhere in the index file that a line break is allowed except that there must be at least one space or line break separating the end of a file spec from the start of acomment To include external index information in an index file a super index can be used which must be the first entry in the file and to subdivide index information an auxiliary index can be employed An auxiliary index may only contain references to a single unit and its descendants this includes both the specification and body of the unit and any units descended from it The mechanism whic
44. a aaa aaa hatau 8 Heihei _ewsmgie HTML amet tem Source Falename s used werer juj rossi neml exanplefexO30seads View analy Source Filename u ross htm examplesexOsGbe ada O Listing Pilename u fross hemil exavyple exO30Ge lar iew ETEL Dnit name P Onit pype paciage specification Unit bez been aenalyecd soy etrore sce liates beloo Unit oane DyDidse Unit type paciage specification Dhit hao becn anelysed sey errots wee listed belou PORTA T EES ETOP T TES ETOP TEE TES ET OPT ITT TES ET eee TTT TE re Lasting of SPARK Text SPAPXSS Exewiner with Vo and RTS Generator Release 4 02023 04 00 Praxis Critical Systems Hath Engiand DATE 19 APR 2000 09 37 36 158 ef OO glee ore Figure 2 Option links The report file contains links to any files specified on the command line Figure 2 shows the links that are available in this section of the report file Figure 2 also shows that links across physical devices are marked as unavailable This is because the links can not be guaranteed to be available when browsing In figure 2 the warning control file link has been selected and is displayed in the bottom frame Page 32 of 95 4 8 2 2 SPARK Examiner User Manual Release 7 3 SPARK HTML Dutput Micsoselt Internat Euphaea Ble 3 934 Go sultan ES Views Go Fwi Hale Addons 18 H hini ranga HTML park tem rep dire with E Optrzcus DATE 19 APR 2O00 10 4
45. a bounded error SPARK requires each task to end with a non terminating loop The environment task or main program does not need to end in a plain loop provided the program closure includes at least one other task If there are no other tasks then the environment task must be made non terminating with a plain loop Semantic Error 990 Unexpected annotation a task body may have only global and derives annotations Issued if a pre post or declare annotation is attached to a task body Semantic Error 991 Unexpected task body XXX is not the name of a task declared in this package specification Issued if task body is encountered for which there is no preceding declaration Semantic Error 1992 A body for task type XXX has already been declared Issued if a duplicate body or body stub is encountered for a task Semantic Error 993 There is no protected type declaration for XXX Issued if a body is found for a protected types for which there is no preceding declaration Semantic Error 1994 Invalid guard XXX is not a Boolean protected element of this protected type The SPARK Ravenscar rules require a simple Boolean guard which must be one of the protected elements of the type declaring the entry Semantic Error 995 Unexpected entry body XXX is not the name of an entry declared in this protected type Local entries are not permitted so a protected body can declare at most one entry body and that must have declared in the protect
46. a reference to the required unit or the index file associated the unit with a file which did not exist or the unit was not found in the file associated with it by the index file Source file entries A list of entries one for each source file used The entry contains the name of the source file the name of the listing file if any a list of the units found or expected in that source file and finally a list of errors found in that file if any If a source file could not be opened this is indicated For each entry in the list of units the Examiner reports whether Page 18 of 95 4 2 TH SPARK Examiner EXM UM User Manual Release 7 3 Issue 7 3 e the unit was expected but could not be found for example if the indication of its presence ina particular file by the index was erroneous e only lexical and syntax analysis was attempted on the unit which occurs for example if a required unit is preceded in its file by a unit which is not required e acomplete analysis including static semantic and flow analysis has been attempted e awarning summary summarising the suppressed warnings if any and noting with an asterisk those which have the potential to invalidate the analysis Resource statistics A list summarising the size and usage of the Examiner s internal tables If a run of the Examiner exhausts any one of these tables it will produce an error message and stop at which point it is necessary to switch to using a version
47. able of a type which is limited or which contains a limited type Semantic Error 309 Operator not visible for these types This message means that the operator exists between the types on each side of it but that it is not visible The most likely cause is that the types concerned are defined in another package and that renaming is required to make the operator visible Semantic Error 310 The operator may only appear in an assert or check statement in a for loop The operator is used to indicate the value of a variable on entry to a for loop This is because the variable may be used in the exit expression of the loop and may also be modified in the body of the loop Since the semantics of Ada require the exit expression to be fixed after evaluation we require a way of reasoning about the original value of a variable prior to any alteration in the loop body No other situation requires this value so may not be used anywhere else Semantic Error 3141 Announced own variable types may not be implemented as unconstrained arrays Where an an own variable is announced as being of some type SPARK requires that type to be declared the declaration cannot be in the form of an unconstrained array because SPARK prohibits unconstrained variables Semantic Error 1312 A subprogram can only be renamed to the same name with the package prefix removed Semantic Error 313 Only one main program is permitted Semantic Error 314 Own variable XXX
48. ackage K will appear in k___p vcg while those for subprogram Q embedded directly within P will appear in k___ p__ q vcg The example given in section 4 7 1 would produce the following files if VCs are generated Analysis of subprogram Sum in p___double__sum fd l p___ double__sum rls p__ _ double ___sum vcg and Double in p__ _double fdl p__ _double rls and p__ _double vcg For the child package examples in section 4 7 1 the analysis of procedure Inc would appear in the files parent__child__ _inc fdl parent__child__ _inc rls and parent__child__ _inc vcg The use of 3 underbars in file names associated with library packages and two for those associated with child package is to ensure that embedded and child packages never generate the same file name If the length of the concatenated file name exceeds the maximum length permitted by the operating system the file name will be truncated Note that this could lead to ambiguous file names in some cases causing the output from more than one subprogram to be written to files of the same name A warning message is displayed if file name truncation occurs see section Error Reference source not found Temporary files The Examiner makes use of temporary files for the merging of error messages into report and listing files By default these temporary files are created in one of the following locations the directory indicated by the TMP environment variable or if this is not set C TEMP or
49. ady appears in the suspends list Items may not appear more than once in an a suspends list Semantic Error 891 Task type or protected type required Issued in a subtype declaration where the constraint is a discriminant constraint Only task and protected types may take a discriminant constraint as part of a subtype declaration Semantic Error 892 Array type task type or protected type required Issued in a subtype declaration where the constraint is a either a discriminant constraint or an index constraint these two forms cannot always be distinguished syntactically Only task and protected types may take a discriminant constraint and only array types may take an index constraint as part of a subtype declaration Semantic Error 893 Number of discriminant constraints differs from number of known discriminants of type XXX Issued in a subtype declaration if too many or two few discriminant constraints are supplied Semantic Error 894 Only variables of a protected type may be aliased SPARK supports the keyword aliased in variable declarations only so that protected and task types can support access discriminants Since it has no other purpose it may not be used except in a protected object declaration Semantic Error 7895 Attribute Access may only be applied to variables which are declared as aliased variable XXX is not aliased This is a slightly annoying Ada issue Marking a variable as aliased prevents it being placed in a regi
50. aminer has seen the owner package body before processing the child and has not found the required refinement constituent then this message results on processing the child Semantic Error 621 Own variable XXX expected as a refinement constituent in this package Own variables of private child packages must appear as refinement constituents of the package which owns the child If the Examiner has seen a child package which declares an own variable before examining its owner amp 146 s body then this message is issued if the owner lacks the required refinement constituent declaration Semantic Error 622 Own variable XXX did not occur in an initialization specification Issued if an own variable appears in an initialization clause and is also a refinement constituent of an own variable which is not marked as initialized Semantic Error 623 Own variable XXX occurred in an initialization specification Issued if an own variable does not appear in an initialization clause and is also a refinement constituent of an own variable that is marked as initialized Semantic Error 624 All operators from ancestor package XXX are already visible A package must appear in a with clause before types declared in it can be specified in a use type clause Semantic Error 630 XXX is not the name of generic Subprogram Only generic subprogram can be instantiated Semantic Error 631 Generic function found where a generic procedure was expected Subprogram k
51. anguage the reserved word some is controlled by the command line option fdl_identifiers If nofdl_identifiers is selected then some may be used as a normal identifier abstract is a reserved word of SPARK 95 For SPARK 83 it is predefined FDL identifier which can be controlled by the fdl_identifiers command line option In addition identifiers beginning with the character sequences fld_ or upf_ are also regarded as predefined FDL identifiers Page 39 of 95 Dj y Ti SPARK Examiner EXM UM User Manual Release 7 3 Issue 7 3 6 Static semantic analysis 6 1 General description This analysis involves checking that a text obeys the static semantic rules of SPARK other than rules relating to control data and information flow which are discussed in chapters 7 and 8 Where error messages contain references to other documents such as the SPARK report the full title of the references used will appear in the report file 6 2 Error messages The following section explains error messages specifically relating to SPARK restrictions the incorrect use of annotations or inconsistencies between annotations and executable code A numeric error code is given in the message the error messages are presented in numerical order An explanation for each error message is given except where the message text is self explanatory Page 40 of 95 KKK KKK KKK KKK KKK KKK KKK KKK KKK KKK KKK KKK KKK KKK
52. annotation all annotations required for procedure or task body XXX have already occurred Semantic Error 156 Entire variable expected Issued when an identifier which SPARK requires to be an entire variable represents something other than this Most commonly this message occurs when a component of a structured variable appears in a core annotation Semantic Error 157 The name XXX already appears in the global variable list Page 47 of 95 KKK KKK KKK KKK KKK KKK KKK KKK KKK KKK KKK KKK KKK KKK KKK KKK SPARK Examiner EXM UM User Manual Release 7 3 Issue 7 3 Semantic Error 158 XXX is a formal parameter of this subprogram Issued ina global annotation if it names a formal parameter of the subprogram Semantic Error 159 The name XXX has already appeared as an exported variable Semantic Error 160 The name XXX already appears in the list of imported variables Semantic Error 161 Exportation of XXX is incompatible with its parameter mode Issued if a parameter appears as an export to a procedure when it is of parameter mode in Semantic Error 162 Importation of XXX is incompatible with its parameter mode Issued if a parameter appears as an import to a procedure when it is of parameter mode out Semantic Error 163 Subprogram XXX cannot be called from here SPARK contains rules to prevent construction of programs containing recursive subprogram calls this error message occurs if a pr
53. another variable reading back a different element Unexpected dependencies should be investigated carefully and only accepted without modfiication of either code or annotation if it is certain they are of false coupling kind Warning 601 The imported value of XXX may be used in the derivation of YYY Here first item is an import and the second is an export of a procedure subprogram The message reports a possible dependency found in the code which does not appear in the specified dependency relation This version of the message has been retained for backward compatibility Warning 602 The undefined initial value of XXX may be used in the derivation of YYY Here XXX is a non imported variable and YYY is an export of a procedure subprogram There are two formats for messages 50 and 601 In the first format presented here if there is more than one variable XXX which affects YYY and does not conform to the specified dependency relation they will appear on the same error message Setting the switch original_flow_errors brings up a Separate message for each variable in the second original format Violation of restriction on imported only variables WY Flow Error 34 The imported non exported variable XXX may be redefined The updating of imported only variables is forbidden under all circumstances Supplementary error messages The following supplementary messages are issued to assist error diagnosis The meanings of these
54. ant considerations for VAX users before they adopt the tree output form VAX VMS prior to version 6 0 imposes a limit of 8 on directory nesting depth If the creation of subdirectories for semantic output files causes this limit to be exceeded the output files will not be written this will be indicated by the error message Unable to create output files for semantic analysis being displayed for those subprograms affected This VMS limitation has been removed with version 6 0 Use of the directory tree structure option is not recommended for users with earlier versions of VMS Tree structure A tree of subdirectories is created beneath the current directory with one level for each level of embedding of scopes present in the code from which VCs or PFs are being generated Within these directories the output files take their name from the name of the subprogram from which they were generated Thus VCs for subprogram P within package K will appear in k p vcg while those for subprogram Q embedded directly within P will appear in k p q vcg Page 28 of 95 M 4 7 2 ss SPARK Examiner EXM UM User Manual Release 7 3 Issue 7 3 The following short example illustrates the process package body P is procedure Double X in out Integer derives X from X post X X 2 is function Sum A B Integer return Integer return A B is begin return A B end Sum begin Double X Sum X X end D
55. antic Error 47 Definition is not static Issued if an array type definition is encountered where one or more of the index types used in the definition is not static Semantic Error 48 Subtypes of private types are not permitted Issued if an attempt is made to declare a subtype of a private type in a location where the full view of the type is not visible Semantic Error 49 Attribute XXX takes only one argument Only SPARK 95 attributes Min and Max require two arguments Semantic Error 51 Arrays may not be ordered Issued if an ordering operator such as amp lt is encountered between objects of an array type other than string or a constrained subtype of string Semantic Error 52 Only Scalar String and Time types may be ordered Ordering operators are only defined for scalar types and type String plus if the Ravenscar Profile is selected types Time and Time_Span in package Ada Real_Time Semantic Error 53 Illegal others clause In SPARK record aggregates may not contain an others clause Semantic Error 54 Illegal attribute XXX Issued when an attribute not supported by SPARK is used Semantic Error 55 Attribute XXX takes no argument Semantic Error 56 Argument expected Semantic Error 57 Fixed type definition must have associated range constraint Semantic Error 58 XXX expected to repeat initial identifier Occurs at the end of a package subprogram protected type task type or loop if the terminal
56. ask type specifications and procedures Semantic Error 1921 The identifier XXX is not recognised as a component of a property list The property list can only specify the reserved word delay suspends or priority Semantic Error 922 The own variable XXX must have the priority property In order to perform the ceiling priority checks the priority property must be given to all own variables of protected type Semantic Error 1923 The procedure XXX cannot be called from a function as it has a blocking side effect Blocking is seen as a side effect and hence procedures that potentially block cannot be called from functions Semantic Error 1924 The suspendable property is not allowed for XXX Objects that suspend must be declared as own protected variables Semantic Error 925 The own variable or task XXX must have a type announcement Own variables of protected type and own tasks must have a type announcement Semantic Error 1926 Illegal declaration of task XXX Task objects must be declared at library level Task objects must be declared in library level package specifications or bodies Semantic Error 1927 The own task annotation for this task is missing the name XXX in its suspends list The task type declaration has name XXX in its list and this must appear in the own task annotation Semantic Error 1928 Private elements are not allowed for protected type XXX Protected type XXX has been used to declare a protected moded ow
57. ason null records are only allowed if they are tagged Semantic Error 1835 XXX is not an extended tagged record type An extension aggregate is only appropriate if the record type it is defining is an extended record A normal aggregate should be used for other record and array types Semantic Error 836 This expression does not represent a valid ancestor type of the aggregate XXX The expression before the reserved word with must be of an ancestor type of the overall aggregate type In SPARK the ancestor expression may not be a subtype mark Semantic Error 837 Invalid record aggregate there is a private ancestor between the type of this expression and the type of the aggregate XXX The ancestor type can be an tagged type with a private extension however there must be no private extensions between the ancestor type and the type of the aggregate Semantic Error 838 Incomplete aggregate null record cannot be used here because fields in XXX require values The aggregate form with null record can only be used f the type of the aggregate is a null record extension of the ancestor type If any fields are added between the ancestor type and the aggregate type then values need to be supplied for them so null record is inappropriate Semantic Error 839 This package already contains a root tagged type or tagged type extension Only one such declaration per package is permitted SPARK permits one root tagged type or one tagged type
58. at procedure must be visible at the point of call This error message indicates that the global variable concerned is not visible It may be that it needs to be added to the global annotation of the procedure containing the call or some further enclosing subprogram or it may be that an inherit clause is missing from the package containing the call Semantic Error 25 The identifier XXX imported by called subprogram is not visible at this point When a procedure is called any global variables imported by that procedure must be visible at the point of call This error message indicates that the global variable concerned is not visible It may be that it needs to be added to the global annotation of the subprogram containing the call or some further enclosing subprogram or it may be that an inherit clause is missing from the package containing the call Semantic Error 26 The deferred constant XXX does not have an associated full definition Issued at the end of a package specification if no full declaration has been supplied for a deferred constant declared in the package specification Semantic Error 27 The private type XXX does not have an associated full definition Issued at the end of a package specification if no full declaration has been supplied for a private type declared in the package specification Semantic Error 28 The own variable XXX does not have a definition Issued at the end of a package body if an own variable announ
59. bject of the assertion is not a derived type i e it is its own base type then this error is raised Semantic Error 797 The base type in a floating point base type assertion must have a defined accuracy Semantic Error 798 The accuracy of the base type in a base type assertion must be at least that of the type which is the subject of the assertion Semantic Error 800 Modulus must be a positive power of 2 In SPARK modular types must have a modulus which is a positive power of 2 Semantic Error 801 Modular types may only be used in SPARK95 Ada83 and hence SPARK83 does not include modular types Semantic Error 803 Unary arithmetic operators are not permitted for modular types Page 63 of 95 KKK KKK KKK KKK KKK KKK KKK KKK KKK KKK KKK KKK SPARK Examiner EXM UM User Manual Release 7 3 Issue 7 3 Unary arithmetic operators are of little value The abs and operators have no effect for modular types and so are not required The unary minus operator is a source of potential confusion and so is not permitted in SPARK Semantic Error 804 Universal expression may not be implicitly converted to a modular type here Left hand operand requires qualification to type XXX A universal expression cannot be used as the left hand operand of a binary operator if the right hand operand is of a modular type Qualification of the left hand expression is required in this case Semantic Error 805 U
60. call depending on the actual parameter passed Warning 407 This package requires a body Care should be taken to provide one because an Ada compiler will not detect its omission Issued where SPARK own variable and initialization annotations make it clear that a package requires a body but where no Ada requirement for a body exists Warning 408 VCs could not be generated for this subprogram due to errors in its abstract specification Unprovable False VC generated Because there are errors in the abstract specification of the subprogram proofs of refinement consistency would be invalid and so VCs have not been generated Correct the first annotations for this subprogram in its package specification Warning 409 RTCs have not been generated for expressions of type Time or Time_Span Types Time and Time_Span are private types which are implemented as an implementation defined integer type see ALRM 9 6 and D 8 Since there is no way of knowing the range of values that are valid for these types the Examiner cannot generate checks to ensure that constraint is error is not raised in their use This warning serves as a reminder that the validity of expressions involving Time and Time_Span must be checked by other means Warning 410 Task or interrupt handler XXX is either unavailable hidden or has semantic errors in its specification which prevent partition wide flow analysis being carried out Partition wide flow analysis is performed by c
61. ced in the package specification has neither been given an Ada declaration nor refined Semantic Error 29 The subprogram XXX declared in the package specification does not have an associated body Semantic Error 30 Attribute XXX is not yet implemented in the Examiner The attribute is identified in Annex K of the SPARK 95 report as a valid SPARK 95 attribute but the Examiner does not currently support it Please contact Praxis High Integrity Systems if use of this attribute is important to your project It is possible to work round the omission by putting the use of the attribute inside a suitable function which is hidden from the Examiner Semantic Error 31 The prefix of this attribute is not an object or type Semantic Error 32 Illegal type conversion Likely causes are type conversions involving record types or non convertible arrays Semantic Error 33 Illegal aggregate Issued if the prefix of an aggregate is not a composite type Semantic Error 34 Illegal procedure call Issued if a call is made to a userdefined subprogram in a package initialization part Semantic Error 35 Operator is not declared for these types Indicates use of an undeclared operator this message means that the type on each side of the operator cannot appear with the operator used e g attempting to add an integer to an enumeration literal Semantic Error 36 Expression is not static Semantic Error 37 Expression is not constant Semantic
62. cfg IndexFile idx SPARK MetaFile smf Examiner ReportFile spark rep HTMLBrowsable foreachsubprogram Output htm ListingFiles Ist Verification FDL Conditions Declarations Rules rls vcg fdl SPARKSimp invokesforeach VC file Simplified UserDefined SimplifierLog VCs siv ee slg ProofChecker ProofReview Files prv SummaryFile ProofLog Command sum plg Log cmd Figure 1 Relationship of SPARK and SPADE Tools Page 10 of 95 a SPARK Examiner EXM UM User Manual Release 7 3 Issue 7 3 M Operating the Examiner The Examiner is a Windows NT console application which is command line driven The command line syntax is given below Command line SPARK Command option Argumentist Argument list Argument Argument Argument File spec Argument option Meta file spec Argument option listing_file file spec nolisting_file Meta file spec File spec Argument option gives the name of the listing file for that argument If an extension is not included in the supplied file spec the default listing extension is used The option nolisting_file suppresses the generation of a listing file for the source file to which the option is applied global suppression of listing files can be achieved by specifying the nolistings command option see section 3 1 2 The results are always Summarised in the report file The defaul
63. ckage Semantic Error 79 Variable XXX should occur in this initialization specification Occurs in the initialization clause of a package embedded in another package if an own variable which is a refinement constituent of an initialized own variable of the enclosing package is omitted Semantic Error 80 Unexpected own variable clause no variable in this clause is a refinement constituent Semantic Error 81 Own variable clause expected own variables of this package occur as refinement constituents Semantic Error 82 Unexpected initialization specification no own variables of this package require initialization An own variable initialization clause and that of its refinement constituents must be consistent Semantic Error 83 Initialization specification expected own variables of this package require initialization Issued if an own variable does not occur in the initialization clause of an embedded package and the own variable concerned is a refinement constituent of another own variable which is listed in the initialization clause of its package Semantic Error 84 The refinement constituent XXX does not have a declaration Issued at the end of a package if a refinement constituent of a refined own variable has not been given an Ada declaration or further refined Semantic Error 85 XXX is not a constituent of any abstract own variable appearing in the earlier global definition for this subprogram A variable XXX whic
64. clared as an abstract proof type Occurs when an own variable clause announces more than one own variable as being of a type XXX and XXX is later declared as being of an abstract proof type Each abstract own variable must be of a unique type Semantic Error 150 Entire variable expected The names of constants never appear in mandatory annotations Issued when a the name of a constant is found in a mandatory annotation such as a global or derives annotation Constants should not appear in such annotations Semantic Error 151 The variable XXX does not occur either in the package own variable list or as a refinement constituent A variable declared in a package must have been previously announced as either an own variable or as a concrete refinement constituent of an own variable Semantic Error 152 The number of formal parameters is not consistent with the previous declaration of XXX Semantic Error 153 The declaration of formal parameter XXX is not consistent with the subprogram s previous declaration Issued if the name type or parameter mode of a parameter is different in the subprogram body declaration from that declared originally Semantic Error 154 The subprogram or task body XXX does not have an annotation A subprogram or task body must have a global annotation if it references global variables a procedure or task body must have a dependency relation to perform information flow analysis Semantic Error 155 Unexpected
65. de effect but the rules of Ada must prevail nonetheless Semantic Error 987 Task types and protected types may only be declared in package specifications The Examiner performs certain important checks at the whole program level such as detection of illegal sharing of unprotected state and partition level information flow analysis These checks require visibility of task types and protected types especially those containing interrupt handlers SPARK therefore requires these types to be declare in package specifications Subtypes and objects of task types protected types and their subtypes may be declared in package bodies Semantic Error 1988 Illegal re use of identifier XXX this identifier is used in a directly visible protected type Page 74 of 95 KKK KKK KKK KKK KKK KKK KKK KKK KKK KKK KKK SPARK Examiner EXM UM User Manual Release 7 3 Issue 7 3 SPARK does not allow the re use of operation names which are already in use in a directly visible protected type The restriction is necessary to avoid overload resolution issues in the protected body For example type PT in package P declares operation K Package P also declares an operation K From inside the body of PT a call to K could refer to either of the two Ks since both are directly visible Semantic Error 989 The last statement of a task body must be a plain loop with no exits To prevent any possibility of a task terminating which can lead to
66. dy in use within the scope of the package Semantic Error 1955 XXX can only appear in the partition wide flow annotation Page 73 of 95 KKK KKK KKK KKK KKK KKK KKK KKK KKK SPARK Examiner EXM UM User Manual Release 7 3 Issue 7 3 Interrupt stream variables are used only to enhance the partition wide flow annotation and must not be used elsewhere Semantic Error 1956 XXX already appears in as an interrupt handler in the interrupt mappings An interrupt handler can be mapped onto exactly one interrupt stream variable An interrupt stream variable may be mapped onto many interrupt handlers Semantic Error 957 Unconditional update of protected variable XXX not allowed here You may only wholly update a protected variable once within a sequence of unprotected statements As the protected state may be updated by another thread between two successive unconditional updates it would be impossible to reason about information flow for the state Semantic Error 958 A task may not import the unprotected state XXX A task may not imoprt unprotected state unless it is mode in This is because under the concurrent elaboration policy the task cannot rely on the state being initialised before it is run Semantic Error 959 Unprotected state XXX is exported by a task and hence must not appear in an initializes clause Own variable XXX is being accessed by a task The order in which the task is run and the own variable
67. eclared Semantic Error 14 Illegal parent unit name Issued if the name is a separate clause of a subunit does not correctly identify a compilation unit A common cause of this error is a syntax error in the parent unit Semantic Error 15 No stub exists for XXX Semantic Error 16 A body for package XXX has already been declared Semantic Error 17 A body stub for package XXX has already been declared Semantic Error 18 Identifier XXX is not the name of a package Semantic Error 19 Identifier XXX is not the name of a procedure Semantic Error 20 Illegal operator symbol Issued if a renaming declaration contains a non existent operator Semantic Error 21 This entity is not an array Issued if an attempt is made to index into a name which does not represent an array Semantic Error 22 The type in this declaration is not consistent with the previous declaration of XXX Occurs when the type given in the Ada declaration of an own variable differs from that announced in the package s own variable clause Semantic Error 23 No parameter association is given for formal parameter XXX Semantic Error 24 The identifier XXX exported by called subprogram is not visible at this point Page 41 of 95 KKK KKK KKK KKK KKK KKK KKK KKK KKK KKK KKK KKK KKK KKK KKK SPARK Examiner EXM UM User Manual Release 7 3 Issue 7 3 When a procedure is called any global variables exported by th
68. ed Semantic Error 752 The identifier YYY XXX is either undeclared or not visible at this point This identifier must appear in a preceding legal global annotation or formal parameter list For an identifier to appear legally as an import in a derives annotation it must be a formal parameter or must appear legally in a preceding global annotation and must be of mode in or mode in out Semantic Error 753 The identifier YYY XXX is either undeclared not visible at this point This identifier must appear in a preceding legal global annotation or formal parameter list For an identifier to appear legally as an export in a derives annotation it must be a formal parameter or must appear legally in a preceding global annotation and must be of mode out or mode in out Semantic Error 754 The identifier YYY XXX is either undeclared or not visible at this point This package must be both inherited and withed to be visible here For a package name to be visible in Ada context it must appear in both the inherit clause and the with clause of the enclosing package Semantic Error 755 The identifier YYY XXX is either undeclared or not visible at this point A parent of a child package must be inherited to be visible here A parent of a child package must be inherited but not withed to be visible in that child Semantic Error 770 If Any_Priority is defined Priority and Interrupt_Priority must also be defined If the type An
69. ed e subtype Priority is Any_Priority range Any_Priority First implementation defined e subtype Interrupt_Priority is Any_Priority range Priority Last 1 Any_Priority Last Semantic Error 775 Interrupt_Priority Last must equal Any_Priority Last LRM D 1 10 Ada 95 requires that task priority types meet the following criteria the third of which is relevant to this e subtype Any_Priority is Integer range implementation defined e subtype Priority is Any_Priority range Any_Priority First implementation defined e subtype Interrupt_Priority is Any_Priority range Priority Last 1 Any_Priority Last Semantic Error 776 In SPARK95 mode only packages Standard System Ada Real_Time and Ada Interrupts may be specified in the config file In SPARK95 mode the packages that may be specified in the target configuration file are Standard System Ada Real_Time and Ada iInterrupts The latter two are ignored unless the Ravenscar profile is selected Semantic Error 777 In package System Priority must be an immediate subtype of Integer Ada 95 and hence SPARK95 defines Priority as being an immediate subtype of Integer Semantic Error 778 This identifier is not valid at this point in the target configuration file The specified identifier cannot be used here it is most probably either not valid in the target configuration file at all or might be valid in a different package but not here Semantic Error 779 Definition of this
70. ed file extension is 1 or p 1 where the intention is to use the default file extension giving a source name p 1 ada and 2 use the listing_file argument to ensure that a suitable listing file names are generated otherwise the Examiner will use generate the rather unintuitive listing file names p 1 and p 2 The use of command line metafiles described in Section 4 4 may be convenient for dealing with these cases Page 11 of 95 a SPARK Examiner EXM UM User Manual Release 7 3 Issue 7 3 M 3 1 Command Line Switch Summary 3 1 1 Input File Options source_extension so file type Allows the user to specify a default extension for source files index_file i file spec Identifies the index file to be used initially The index file mechanism is described in section 4 2 warning_file w file spec This identifies the warning control file to be used A warning control file is used to determine how certain warning messages generated by the Examiner are displayed The format and content of a warning control file is described in section 4 3 nowarning file now fv Provides full reporting of all warnings Provides full reporting of all warnings target_compiler_data ta file_spec Specifies the name of the target data file this file is described in section 4 3 notarget_compiler_data Suppresses the use of the target data file config_file conf file_spec Specifies the name of the target configuration file this file is
71. ed type specification Semantic Error 996 The protected operation XXX declared in this type does not have an associated body Each exported protected operation must have a matching implementation in the associated protected body Semantic Error 997 A body for protected type XXX has already been declared Each protected type declaration must have exactly one matching protected body or body stub Semantic Error 998 There is no protected type declaration for XXX Issued if a protected body or body stub is found and there is no matching declaration for it Semantic Error 999 This feature of Generics is not yet implemented Page 75 of 95 6 3 SPARK Examiner EXM UM User Manual Release 7 3 Issue 7 3 Warning messages As well as the error messages described above the Examiner may produce warnings The presence of warning messages does not mean that the program contains errors but does indicate areas which may require additional care by the user because the construction warned about may affect the meaning of a SPARK program in ways that cannot be detected by the Examiner Section 4 3 describes a way of instructing the Examiner to summarise rather than individually report some or all of these warning messages the keyword used in the warning control file to inhibit full reporting in each case is included in the explanations which follow The possible warning messages are described below Warning No semantic checks carried o
72. eka SPARK Examiner User Manual Release 7 3 NT EXM UM Issue 7 3 Status Definitive 12 January 2006 Originator SPARK Team Approver SPARK Team Line Manager ss SPARK Examiner EXM UM User Manual Release 7 3 Issue 7 3 M Copyright The contents of this manual are the subject of copyright and all rights in it are reserved The manual may not be copied in whole or in part without the written consent of Praxis High Integrity Systems Limited The software tools referred to in this manual are the subject of copyright and all rights in them are reserved The rights in these tools are owned by Praxis High Integrity Systems Limited and it may not be copied in whole or in part without the written consent of this company except for reasonable back up purposes The same proprietary and copyright notices must be affixed to any permitted copies as were affixed to the original This exception does not allow copies to be made for others whether or not sold and none of the material purchased may be sold given or loaned to another person or organisation Under law copying includes translating into another language or format 1991 2006 Praxis High Integrity Systems Limited 20 Manvers St Bath BA1 1PX Limited Warranty Praxis High Integrity Systems Limited save as required by law makes no warranty or representation either express or implied with respect to this software its quality performance merchantability or f
73. elected Semantic Error 950 Partition annotation expected a global and optionally a derives annotation must appear after main_program when the Ravenscar profile is selected When the Ravenscar profile is selected the global and derives annotation on the main program describes the behaviour of the environment task only not the entire program An additional annotation called the partition annotation is required to describe the entire program s behaviour this annotation follows immediately after main_program Semantic Error 951 Inherited package XXX contains tasks and or interrupt handlers and must therefore appear in the preceding WITH clause In order to ensure that a Ravenscar program is complete SPARK requires that all active packages inherited by the environment task also appear in a corresponding with clause This check ensures that any program entities described in the partition annotation are also linked into the program itself Semantic Error 952 Subprogram XXX is an interrupt handler and cannot be called Interrupt handler operations cannot be called Semantic Error 953 Interrupt property error for own variable YYY XXX is not an interrupt handler in type ZZZ The handler names in an interrupt property must match one in the protected type of the own variable Semantic Error 954 Interrupt property error for own variable XXX Interrupt stream name YYY is illegal The stream name must be unprefixed and not alrea
74. emantic Error 1324 Only one field name may appear here When using the extended SPARK update syntax for a record you can not update more than one element in each clause of the update For example you cannot use x y amp gt z you must instead use x amp gt z y amp gt z Semantic Error 1325 Type XXX has not been declared Occurs if a type is announced as part of an own variable clause and the end of the package is reached without an Ada declaration for a type of this name being found Semantic Error 326 Predicate is not boolean Occurs anywhere where a proof context is found not to be a boolean expression Page 51 of 95 KKK KKK KKK KKK KKK KKK KKK KKK KKK KKK KKK KKK KKK KKK KKK KKK SPARK Examiner EXM UM User Manual Release 7 3 Issue 7 3 Semantic Error 1327 XXX is a global variable which may not be updated in a function subprogram Semantic Error 1328 The identifier XXX exported by called subprogram may not be updated in a function subprogram Occurs if a function calls a procedure which exports a global variable this would create an illegal side effect of the function Semantic Error 1329 Illegal function call Issued if a call is made to a userdefined subprogram in a package initialization part Semantic Error 330 Illegal use of an own variable not of this package Issued if an attempt is made in a package initialization part to update an own variable of a non
75. en information flow analysis is not performed and when modes were specified in the global annotation It is a reminder that the dependencies specified in this annotation including whether each variable is an import or an export have not been checked against the code and may therefore be incorrect warning control file keyword notes Note 2 This dependency relation has been used only to identify imports and exports dependencies have been ignored Issued as a reminder when information flow analysis is not performed in SPARK 83 The dependencies specified in this annotation have not been checked against the code and may therefore be incorrect warning control file keyword notes Note 3 The deferred constant Null_Address has been implicitly defined here Issued as a reminder that the declaration of the type Address within the target configuration file implicitly defines a deferred constant of type Null_Address warning control file keyword notes Note 4 The constant Default_Priority of type Priority has been implicitly defined here Issued as a reminder that the declaration of the subtype Priority within the target configuration file implicitly defines a constant Default_Priority of type Priority with the value Priority First Priority Last 2 warning control file keyword notes Page 84 of 95 M 7 1 7 2 oss SPARK Examiner EXM UM User Manual Release 7 3 Issue 7 3 Control flow analysis General d
76. enclosing package Semantic Error 1331 Private types may not be unconstrained arrays Semantic Error 1332 This private type was not declared as limited Issued where the type contains a component which is a limited private type but where the declaration of this type in the visible part of the package does not specify that the type is limited Semantic Error 1333 Initialization of XXX is not announced in the initialization clause of this package Issued when an own variable is initialized either by assignment or by having a pragma Import attached to it when initialization of the variable is not announced in its package s own variable initialization specification Semantic Error 1334 Identifier XXX is not the name of a function Semantic Error 335 This annotation should be placed with the declaration of function XXX Issued if a function is declared in a package specification without an annotation but one is then supplied on the function body Semantic Error 336 Unexpected annotation all annotations required for function XXX have already occurred Semantic Error 1337 Package XXX may not be used as a prefix here Selected component notation may not be used in places where an item is directly visible Semantic Error 1338 Scalar parameter XXX is of mode in out and must appear as an import Parameters passed as mode in out must be listed as imports in the subprogram s dependency relation if they are of scalar types The rule als
77. eports a syntax error AR Syntax Error No APRAGMA can be start with reserved word IS This can occur when a stub for an embedded subprogram is wrongly terminated by a semicolon EAR Syntax Error No complete PROCEDURE_SPECIFICATION can be followed by ANNOTATION_START here This can occur when the reserved word body has been omitted from the declaration of a package body This error will occur at the annotation placed between the specification and the reserved word is of the first subprogram FRR Syntax Error No complete PROCEDURE_SPECIFICATION can be followed by reserved word IS here This can occur when the reserved word body has been omitted from the declaration of a package body This error will occur at the reserved word is which introduces the body of the first subprogram KER Syntax Error reserved word INHERIT expected This occurs where the annotation on a subprogram body is placed after the reserved word is instead of before it ERR Syntax Error No complete SIMPLE_EXPRESSION can be followed by here This can occur in an aggregate expression when there is a mixure of named and positional association being used EEK Syntax Error No complete SIMPLE_EXPRESSION can be followed by here Page 37 of 95 TH SPARK Examiner EXM UM User Manual Release 7 3 Issue 7 3 5 3 This can occur in an aggregate expression when there is a mixure of named and positional association being used
78. epresentations Facilities can be made available for run time checking of real numbers please contact Praxis High Integrity Systems if this is of interest Warning 402 Default assertion planted to cut loop In order to prove properties of code containing loops the loop must be cut with a suitable assertion statement When generating runtime checks the Examiner inserts a simple assertion to cut any loops which do not have one supplied by the user The assertion is placed at the point where this warning appears in the listing file The default assertion asserts that the subprogram s precondition if any is satisfied that all imports to it are in their subtypes and that any for loop counter is in its subtype In many cases this provides sufficient information to complete a proof of absence of run time errors If more information is required then the user can supply an assertion and the Examiner will append the above information to it Warning 403 XXX is declared as a variable but used as a constant XXX is a variable which was initialized at declaration but whose value is only ever read not updated it could therefore have been declared as a constant warning control file keyword constant_variables Warning 404 Subprogram imports variables of abstract types for which run time checks cannot be generated Warning 405 RTCs for statements including real numbers are approximate Where the optional RealRTC switch is used the Examin
79. er generates checks associated with real numbers using perfect arithmetic rather than the machine approximations used on the target platform It is possible that rounding errors might cause a constraint_error even if these run time check proofs are completed satisfactorily Please consult the Supplementary Release Note The RealRTC Option for more details Page 81 of 95 SPARK Examiner EXM UM User Manual Release 7 3 Issue 7 3 Warning 406 Subprogram imports or exports unconstrained array existence of run time errors depends on the calling environment see RTC manual Where a formal parameter of a subprogram is an unconstrained array the size of the array is determined by the size of the actual parameter in the calling environment this causes two difficulties for the proof of absence of run time errors 1 Checks on the validity of index expressions which are made inside the body of the subprogram will be in terms of the unconstrained array index type rather than in terms of the actual constrained size of the array for a particular call Therefore the successful proof of the index to be within the unconstrained array type is not sufficient to prove the absence of run time errors It is necessary to insert suitable annotations to move the proof obligation to the point of call where the array index type is known 2 Attributes such as Last of the array will not have a constant value for proof purposes since the value will vary from call to
80. escription Since Ada is already rich in control structures it is possible to remove its goto statement without unreasonably hindering the programmer Then to ensure that control structures are well formed for analysis purposes it suffices to place minor restrictions on the placement of exit statements and return statements Precise details are given in the SPARK Definition Checks that exit and return statements have been correctly placed are performed directly on the abstract syntax tree of a SPARK text Error messages Exit statements that violate the rules given in the SPARK Definition are always indicated by the following message ERE Illegal Structure 1 An exit statement may not occur here Exit statements must be of the form exit when c where the closest enclosing statement is a loop or if c then S exit where the if statement has no else part and its closest enclosing statement is a loop See the SPARK Definition for details Violations of the rules concerning return statements are indicated by messages of the following kinds EER Illegal Structure 2 A return statement may not occur here A return statement may only occur as the last statement of a function ae Illegal Structure 3 The last statement of this function is not a return statement SPARK requires that the last statement of a function be a return statement BAS Illegal Structure 4 Return statements may not occur in procedure subprograms Page 85 of 95
81. expected Issued when performing data flow analysis only where a subprogram has no dependency clause and its global variables have not been given modes in the global annotation Semantic Error 501 Dependency relation expected A dependency relation is required for each procedure if information flow analysis is to be performed Semantic Error 502 Exportation of XXX is incompatible with its global mode Issued when a procedure has both a global annotation with modes and a dependency relation and a global of mode in is listed as an export in the dependency relation Semantic Error 503 Importation of XXX is incompatible with its global mode Issued when a procedure has both a global annotation with modes and a dependency relation and a global of mode out is listed as an import in the dependency relation Semantic Error 504 Parameter XXX is of mode in out and must appear as an impot Semantic Error 505 Global variable XXX is of mode in out and must appear as an import Page 54 of 95 KKK KKK KKK KKK KKK KKK KKK KKK KKK KKK KKK KKK KKK KKK KKK KKK KKK KKK KKK KKK KKK SPARK Examiner EXM UM User Manual Release 7 3 Issue 7 3 Issued where a procedure has both a global annotation with modes and a dependency relation and a global variable of mode in out is not listed as an import in the dependency relation Semantic Error 506 Parameter XXX is of mode in out and must appear as an exp
82. exported Percent indicates the value of a variable on entry to a for loop this message occurs if either operator is applied to any other object Semantic Error 319 Tilde may only be applied to a variable which is both imported and exported The tilde decoration indicates the initial value of a variable or parameter which is both imported and exported this message occurs if the variable concerned is either exported only or imported only in which case no distinction between its initial and final value is required Semantic Error 320 Tilde or Percent may only be applied to an entire variable Tilde and may not be applied to an element of an array or field of a record e g to indicate the initial value of the Ith element of array V use V I not V I Semantic Error 1321 Tilde may not appear in pre conditions Since it does not make sense to refer to anything other than the initial value of a variable in a pre condition there is no need to use tilde to distinguish initial from final values Semantic Error 1322 Only imports may be referenced in pre conditions or return expressions Pre conditions are concerned with the initial values of information carried into a subprogram Since only imports can do this only imports can appear in pre condition expressions Semantic Error 323 Updates may only be applied to records or arrays The extended SPARK update syntax is only used to express changes to components of a structured variable S
83. from two or more subprograms will be written to the same file name if they have a sufficiently large number of characters in common Page 92 of 95 10 M SPARK Examiner EXM UM User Manual Release 7 3 Issue 7 3 Static limits and associated error messages The Examiner is written in SPARK and therefore does not make use of access types and dynamic data structures Because of this it contains a number of data structures of fixed sizes see the Release Note for the actual table sizes If any of these fixed limits is exceeded the Examiner will stop displaying the message Internal static tool limit reached on the terminal Preceding this will be the cause for example Syntax tree overflow The screen will also echo the consumption of the principal tables in these circumstances The solution in all Such cases is to move to a larger Examiner three sizes are provided in the distribution kit If the capacity of the largest Examiner is exceeded then please contact Praxis High Integrity Systems for advice A similar form of message will be seen if the tool reaches an operating system limit such as the number of files that can be open at any time In this case the message will be prefixed by Operating system limit reached Such limits must be attended to by the system manager of the system on which the Examiner is being operated Praxis High Integrity Systems may be able to assist in identifying the parameter that requires alterat
84. ft to right evaluation was assumed for RTC generation Issued when a potentially re orderable expression is encountered when run time expression overflow checks are being generated For example x a b c Whether intermediate sub expression values overflow may depend on the order of evaluation which is compiler dependent The Examiner generates RTCs on the basis of left to right evaluation however code generating this warning should be parenthesised to remove the ambiguity e g x a b c Warning 303 Overlapping choices may not be detected Issued where choices in an array aggregate or case statement are outside the range which can be detected because of limits on the size of a table internal to the Examiner Warning 304 Case statement may be incomplete Issued when the Examiner cannot determine the completeness of a case statement because the bounds of the type of the controlling expression exceed the size of the internal table used to perform the checks Warning 305 Value too big for internal representation Issued when the Examiner cannot determine the completeness of an array aggregate or case statement because the number used in a choice exceed the size allowed in the internal table used to perform the checks Warning 306 Aggregate may be incomplete Issued when the Examiner cannot determine the completeness of an array aggregate because its bounds exceed the size of the internal table used to perform the checks
85. ge AL tit 4 1 Slow Brrer 10 Assignment to U is inefrertire link displays an explanation in the ee bottom frame tit 2 Plow Error t 5 The verrable is neither refyrencod nor exported Mo summarised tarnings Wi Flow Error 10 TorGectve statement Erucuton af this statemavat cannot affect the Dnot value ef aay waported vanabls of the scberageens mnich u occurs The cause may bea dataflow anomia Le vie statorreat could br weaasiomment to a vans whack is ajwaye undated again bafore it is read However statements may Ss tnafiesty s far other reasaus ose Sesnon 4 af Appendix A I Flow Error 10 Asgignment to SOCK ig ine cve a ooo Figure 5 SPARK HI ML thet ow Notscapu Uair nams DyDI0Se Oust type package boa Unit has been analysed any errors ere iisted belon The line number link 3 error s oc osrning s displays the listing file at that line in the bottom frame P bavadei c Bie AT Flow Error Ds 7 t 0 Assignment ta ie ineffective t 33 The viable U ig neither referonced nor exported 44 Pibividets D O R aj EED SA Hs Errer t 10 Assignment to Q is ineffective 45 crm B we 75 EER SERN The listing file also links ie n errors to their explanations Eea d a aa as ia aaa a a aaa itt z Figure 6 Page 35 of 95 a SPARK Examiner EXM UM User Manual Release 7 3 Issue 7 3 M 4 8 2 5 Listing File Links The lis
86. ge XXX require initialization Either the package does not have an initializes annotation or all the own variables requiring initialization were given values at the point of declaration Semantic Error 67 Illegal machine code insertion Machine code functions are not permitted in SPARK 83 This is an Ada 83 rule Machine code can only be used in procedures Semantic Error 68 Illegal operator renaming operators are defined on types not subtypes Issued if an attempt is made to rename an operator using a subtype of the type for which it was originally implicitly declared Semantic Error 69 pragma XXX has two parameters Semantic Error 70 pragma Import expected Semantic Error 70 pragma Interface expected Semantic Error 71 This expression does not represent the expected subprogram or variable name XXX Issued if the name supplied in a pragma interface import or attach_handler does not match the name of the associated subprogram or variable Semantic Error 72 Unexpected pragma Import Pragma import may only occur in a body stub or immediately after a subprogram declaration in the visible part of a package or immediately after a variable declaration Semantic Error 72 Unexpected pragma Interface Pragma interface may only occur in a body stub or immediately after a subprogram declaration in the visible part of a package Semantic Error 73 XXX has already been declared or refined Page 44 of 95 KKK
87. ge which is embedded in a package or subprogram Semantic Error 615 Name does not match name of package Issued if the closing identifier of a package has a different number of identifiers from the name originally given for the package For example package P Q is end P Q R Semantic Error 616 The private package XXX is not visible at this point Issued if an attempt is made to with or inherit a private package from the visible part of a public package Semantic Error 617 Public sibling XXX is not visible at this point Arises from attempting to inherit a public sibling child package from a private child package Semantic Error 618 The owner of the current package does not inherit the package XXX A private child package can only inherit a remote package if its parent also inherits it this is a analogous to the behaviour of embedded packages which may also only inherit a remote package if their enclosing package also does so Semantic Error 619 The package XXX is not owned by the current package This message indicates an attempt to claim that own variables of a package other than a private child package of the current package are refinement constituents of an abstract own variable of the current package Semantic Error 620 Own variables here must be refinement constituents in package owner XXX Own variables of private child packages must appear as refinement constituents of the package which owns the child If the Ex
88. h as Unused for the actual parameter concerned The message Assignment to Unused is ineffective is then self documenting Flow Error 53 The package initialization of XXX is ineffective Here XXX is an own variable of a package initialized in the package initialization The message states that XXX is updated elsewhere before being read Flow Error 54 The initialization at declaration of XXX is ineffective Issued if the value assigned to a variable at declaration cannot affect the final value of any exported variable of the subprogram in which it occurs because for example it is overwritten before it is used Page 88 of 95 M 8 3 3 8 3 4 SPARK Examiner EXM UM User Manual Release 7 3 Issue 7 3 Invariant conditions and stable exit conditions 1 1 1 1 1 1 1 Flow Error 22 Value of expression is invariant The expression is either a case expression or a condition Boolean valued expression associated with an if statement not contained in a loop statement The message indicates that the expression takes the same value whenever it is evaluated in all program executions Note that if the expression depends on values obtained by a call to another other subprogram then a possible source for its invariance might be an incorrect annotation on the called subprogram Flow Error 40 Exit condition is stable of index O Flow Error 40 Exit condition is stable of index 1 Flow Error 40 Ex
89. h has occurred in a refined global annotation is neither a variable that occurred in the earlier global definition nor a refinement constituent of any such variable Semantic Error 86 At least one constituent of XXX was expected in this refined global definition Page 45 of 95 KKK KKK KKK KKK KKK KKK KKK KKK KKK KKK KKK KKK KKK KKK KKK KKK KKK KKK KKK KKK KKK KKK KKK KKK KKK SPARK Examiner EXM UM User Manual Release 7 3 Issue 7 3 If the global annotation of a procedure specification contains an own variable and that own variable is later refined then at least one refinement constituent of the own variable shall appear in the second global annotation supplied for the procedure body Semantic Error 87 Refined global definition expected for subprogram XXX A global definition containing abstract own variables was given in the definition for subprogram XXX in a package specification A refined global definition is required in the package body Semantic Error 88 Variable XXX is not a refinement constituent Semantic Error 89 XXX is not a private type declared in this package Semantic Error 90 This operator may not be applied to ranges Semantic Error 91 Ranges may not be assigned Semantic Error 92 Named association may not be used here Semantic Error 93 Number of index expressions differs from number of dimensions of array XXX Semantic Error 94 Condition i
90. h the Examiner uses to search an index file in order to associate a file location with a compilation unit is as follows 1 The Examiner scans the successive entries in the index file until it reaches an entry to which either of the following conditions apply a The unit name and type in the index entry match those of the sought compilation unit In this case the file location used is that given in the index entry b The entry is for an auxiliary index associated with the unit itself or its parent or a furtherremoved ancestor In other words the unit name in the entry is either the name of the sought unit or is a prefix of it In this case Step 1 is applied again to the auxiliary index in place of the original one This process is applied until either an entry meeting condition a is found or it terminates unsuccessfully It may be applied several times if auxiliary indexes themselves contain auxiliary indexes 2 If the search of an index and possibly auxiliary indexes in the above manner is unsuccessful Step 1 is then applied to the super index of the original index if it has one Should this be unsuccessful Step 1 is then applied to the super index of the super index and so on Note that the ordering of auxiliary indexes is important an auxiliary index for a compilation unit A must precede all auxiliary indexes for ancestors of A e g an auxiliary index for a unit X Y must precede an auxiliary index for X Page 20 of 9
91. hecked_Conversion only Semantic Error 638 Unexpected global annotation A generic subprogram may not reference or update global variables A standalone generic subprogram may not have a global annotation Note that a subprogram in a generic package may have a global annotation as long as it only refers to own variables that are local to the package Semantic Error 639 A generic formal object may only have default mode or mode in SPARK restricts formal objects to being constants in order to avoid concealed information flows Semantic Error 640 A generic formal object may only be instantiated with a constant expression SPARK restricts formal objects to being constants in order to avoid concealed information flows Semantic Error 641 There is no generic subprogram declaration named XXX so a generic body of that name cannot be declared here A generic body must be preceded by a generic declaration of the same name Semantic Error 642 XXX is not the name of a generic subprogram so a generic body cannot be declared here A generic body must be preceded by a generic declaration of the same name Semantic Error 643 XXX is a generic function so a generic procedure body cannot be declared here A generic body must be preceded by a generic declaration of the same name and kind Semantic Error 644 XXX is a generic procedure so a generic function body cannot be declared here A generic body must be preceded by a generic declaration
92. hecking all packages withed by the main program for tasks and interrupt handlers and constructing an overall flow relation that captures their cumulative effect It is for this reason that SPARK requires task and protected types to be declared in package specifications If a task or protected type which contains an interrupt handler is hidden from the Examiner in a hidden package privat part or contains errors in it specification the partition wide flow analysis cannot be constructed correctly and is therefore supressed Correct the specification of the affected tasks and temporarily if desired make them visible to the Examiner Warning 411 Task type XXX is unavailable and has not been considered in the shared variable check The Examiner checks that there is no potential sharing of unprotected data between tasks If a task type is hidden from the Examiner in a hidden package private part then it is not possible to check whether that task may share unprotected data Warning 412 Task type XXX is unavailable and has not been considered in the max one in a queue check The Examiner checks that no more than one task can suspend on a single object If a task is hidden from the Examiner in a hidden package private part then it is not possible to check whether that task may suspend on the same object as another task Warning 413 Task or main program XXX has errors in its annotations The shared variable and max one in a queue checks may be i
93. hen reading Boolean external variables More information on interfacing can be found in the INFORMED manual Warning 394 Variables of type XXX cannot be initialized using the facilities of this package A variable of a private type can only be used without generating a data flow error if there is some way of giving it an initial value For a limited private type only a procedure that has an export of that type and no imports of that type is suitable For a private type either a procedure function or deferred constant is required The required facility may be placed in or already available in a public child package Warning 395 Variable XXX is an external 6tream variable but does not have an address clause or a pragma import When own variables are given modes they are considered to be inputs from or outputs to the external environment The Examiner regards them as being volatile i e their values can change in ways not visible from an inspection of the source code If a variable is declared in that way but it is actually an ordinary variable which is NOT connected to the environment then misleading analysis is inevitable The Examiner expects to find an address clause or pragma import for variables of this kind to indicate that they are indeed memory mapped input output ports This warning is issued if an address clause or pragma import is not found Warning 396 Unexpected address clause Variable XXX is not identified as an external
94. ies which exist in the full Ada language SPARK incorporates annotations or formal comments These are of two kinds Core annotations whose use is imposed by certain language rules of SPARK The SPARK Definition contains a list of these and Proof contexts which may be employed to include formal specifications in a SPARK text and to guide its machine assisted proof The SPARK Examiner is a free standing software tool to support the use of this language The Examiner always e checks conformance of a text with the rules of SPARK e checks consistency of executable code with its core annotations and optionally can be used to e obtain verification conditions VCs for SPARK programs to which the SPADE Automatic Simplifier SAS may be applied The SAS reduces a substantial proportion of the provable conclusions in verification conditions to true Any VC conclusions remaining to be verified after application of the SAS can be read by the SPADE Proof Checker which can then be used to prove them interactively The use of the SPADE Automatic Simplifier and Proof Checker is described separately in other Praxis High Integrity Systems documents This manual explains how to use the Examiner to generate verification conditions for SPARK programs The process of proof is described in the manual Generation of Verification Conditions for SPARK Programs e facilitate demonstration that a SPARK program is free from run time errors This proces
95. ind of generic and its instantiation must match Page 56 of 95 KKK KKK KKK KKK KKK KKK KKK KKK KKK KKK KKK KKK KKK KKK SPARK Examiner EXM UM User Manual Release 7 3 Issue 7 3 Semantic Error 632 Generic procedure found where a generic function was expected Subprogram kind of generic and its instantiation must match Semantic Error 633 Generic actual part expected generic unit XXX has generic formal parameters The number of generic formal and actual parameters must match exactly Semantic Error 634 Unexpected generic actual part generic unit XXX does not have any generic formal parameters The number of generic formal and actual parameters must match exactly Semantic Error 635 Incorrect number of generic actual parameters for instantiation of genric unit XXX The number of generic formal and actual parameters must match exactly Semantic Error 636 Type XXX is not compatible with generic formal parameter YYY See ALRM 12 5 Each generic formal type parameter must be supplied with an actual type which is of a compatible class Note that SPARK does not have default values for such associations Semantic Error 637 User defined generic units are not permitted in SPARK 83 There are weaknesses in the generic type model of Ada 83 that prevent the implementation of a safe subset of generics in SPARK 83 These deficiences are overcome in Ada 95 SPARK 83 users may employ the predefined unit Unc
96. ion Fatal errors prefixed by Unexpected internal error indicate an internal anomaly in the Examiner in the unlikely event that errors of this form occur please contact Praxis High Integrity Systems Page 93 of 95 Dj y TH SPARK Examiner EXM UM User Manual Release 7 3 Issue 7 3 Document Control and References Praxis High Integrity Systems Limited 20 Manvers Street Bath BA1 1PX UK Copyright Praxis High Integrity Systems Limited 2004 All rights reserved File under CVSROOT userdocs Examiner_UM doc was S P0468 73 70 Changes history Issue 0 1 12th January 2000 First Draft created from v4 0 manual Issue 0 2 13th June 2000 Second draft believed complete Issue 1 0 16th June 2000 Definitive after formal review Issue 1 1 14th Feb 2001 Added cfrs 810 812 824 831 833 838 852 Documented RealRTC and OptFlow Issue 1 2 28th March 2001 Added documentation of Version switch CFR 879 Issue 1 3 13th July 2001 Start of updating for Release 6 0 Issue 1 4 24th August 2001 Adds errors 724 730 750 754 800 805 Issue 1 5 24th August 2001 Adds ability to specify Long_Integer attributes in target data file Issue 1 6 31st August 2001 Correct Examiner Simplifier and Checker context diagram Issue 2 0 31st October 2001 After review S P0468 79 74 Issue 2 1 7th January 2002 Added documentation of target configuration file CFR 992 Issue 2 11 5th February 2002 Added target configuration file to
97. ion is recommended NB If the target configuration file is specified on the command line but cannot be found by the Examiner then analysis of the source files will not be carried out and a warning will be emitted Syntax The format of the file resembles a number of SPARK package specifications concatenated in one file The grammar of the file is as follows config_file config_defn config_defn config_defn package package_name is seq_defn end package_name seq_defn defn defn defn fp_type_defn int_type_defn int_subtype_defn fp_const_defn int_const_defn private_defn fp_type_defn type fp_type_name is digits int_literal range fp_literal fp_literal int_type_defn type int_type_name is private_defn type private_type_name is int_expr un_exp_part add_sub int_literal add_sub un_exp_part exp_part range int_expr int_expr u un private Page 24 of 95 SPARK Examiner User Manual Release 7 3 exp_part int_literal int_literal int_literal int_subtype_defn subtype int_subtype_name is simple_name range in fp_const_defn fp_const_name constant fp_literal int_const_defn int_const_name constant int_expr int_literal lt a valid SPARK integer literal gt
98. it condition is stable of index greater than 1 In these cases the loop exit condition occurs in an iteration scheme an exit statement or an if statement whose unique sequence of statements ends with an unconditional exit statement see the SPARK Definition The concept of loop stability is explained in Section 4 4 of Appendix A A loop exit condition which is stable of index O takes the same value at every iteration around the loop and with a stability index of 1 it always takes the same value after the first iteration Stability with indices greater than O does not necessarily indicate a program error but the conditions for loop termination require careful consideration Flow Error 41 Expression is stable of index 0 Flow Error 41 Expression is stable of index 1 Flow Error 41 Expression is stable of index greater than 1 The expression occurring within a loop is either a case expression or a condition Boolean valued expression associated with an if statement whose value determines the path taken through the body of the loop but does not directly cause loop termination Information flow analysis shows that the expression does not vary as the loop is executed so the same branch of the case or if statement will be taken on every loop iteration An Index of O means that the expression is immediately stable 1 means it becomes stable after the first pass through the loop and so on The stability index is given with reference
99. itness for a purpose As a result the licence to use this software is sold as is and you the purchaser are assuming the entire risk as to its quality and performance Praxis High Integrity Systems Limited accepts no liability for direct indirect special or consequential damages nor any other legal liability wnatsoever and howsoever arising resulting from any defect in the software or its documentation even if advised of the possibility of such damages In particular Praxis High Integrity Systems Limited accepts no liability for any programs or data stored or processed using Praxis High Integrity Systems Limited products including the costs of recovering such programs or data SPADE is a trademark of Praxis High Integrity Systems Limited Note The SPARK programming language is not sponsored by or affiliated with SPARC International Inc and is not based on SPARC architecture Page 2 of 95 TH SPARK Examiner User Manual Release 7 3 Contents 1 Overview 2 General description 2 1 Examiner Operation 2 2 Verification Conditions and Run time Checks 3 Operating the Examiner 3 1 Command Line Switch Summary 3 2 The Default Switch File 4 Input and output files 4 1 The report file 4 2 The index file 4 3 The warning control file 44 The meta file 4 5 The target compiler data file 4 6 The target configuration file 4 7 VC output file structure 4 8 HTML Output 5 Lexical and syntactic analysis 5 1 General description 5 2 Error mes
100. ized during package elaboration or implicitly by the environment because it represents an input port it should be placed in an initializes annotation Otherwise there needs to be some way of assigning an initial value during program execution Either the own variable needs to be declared in the visible part of the package so that a direct assignment can be made to it or more usually the package must declare at least one procedure for which the own variable is an export but not an import Note that if the own variable is an abstract own variable with some constituents initialized during elaboration and some during program execution then it will never be possible correctly to initialize it such abstract own variables must be divided into separate initialized and uninitialized components Warning 399 The called subprogram has semantic errors in its interface parameters and or annotations which prevent flow analysis of this call Issued to inform the user that flow analysis has been suppressed because of the error in the called subprogram s interface Warning 400 Variable XXX is declared but not used Issued when a variable declared in a subprogram is neither referenced nor updated warning control file keyword unused_variables Warning 401 RTCs have not been generated for statements including real numbers The SPARK Examiner does not by default generate run time checks for real numbers due to the imprecise nature of their machine r
101. last Page 17 of 95 M 4 1 oss SPARK Examiner EXM UM User Manual Release 7 3 Issue 7 3 Input and output files The report file The report file summarises the activity and findings of the Examiner A report file has the following parts Banner The banner gives the tool name and release and names the licensee of the tool The date and time of analysis is also given Options An indication of the analysis options used by the Examiner including default values Selected files A list of the filenames directly selected for analysis Index file list A list of the index files used Meta file list A list of the meta files used and the filenames read from them Warning selection This lists the causes of warning messages which will be provided in a summarised form rather than reported fully Target compiler data A list of the values read from the target compiler data file Target configuration file A listing of the target configuration file including any syntactic or static semantic errors detected by the Examiner Source file list A list of the full file specs of all the source files used during analysis both those supplied on the command line including those specified in meta files and those read using the index mechanism Units required but not found A list of the units which were required during the analysis but could not be located because e there was no index file or e the given index file did not contain
102. ler have not been performed Issued when a hide XXX annotation is used to hide a userdefined exception handler warning control file keyword handler_parts Warning 10 XXX is hidden hidden text is ignored by the SPARK Examiner Issued when a hide XXX annotation is used warning control file keyword hidden_parts Warning 11 Unnecessary others clause case statement is already complete The others clause is non executable because all case choices have already been covered explicitly If the range of the case choice is altered later then the others clause may be executed with unexpected results It is better to omit the others clause in which case any extension of the case range will result in a compilation error Warning 12 Function XXX is an instantiation of Unchecked_Conversion See ALRM 13 9 The use of Unchecked_Conversion can result in implementation defined values being returned The function should be used with great care The principal use of Unchecked_Conversion is SPARK programs is the for the reading of external ports prior to performing a validity check here the suppression of contraint checking prior to validation is useful The Examiner does not assume that the value returned by an unchecked conversion is valid and so unprovable run time check VCs will result if a suitable validity check is not carried out before the value is used warning control file keyword unchecked_conversion Warning 13 Function XXX is
103. many pragmas e g pragma page are harmless others can change a program s meaning for example by causing two variables to share a single memory location warning control file keyword pragma pragma_identifier or pragma all Warning 4 declare annotation ignored by the SPARK Examiner The declare annotation is ignored by the Examiner if the profile is not Ravenscar warning control file keyword declare_annotations Warning 5 XXX contains interrupt handlers it is important that an interrupt identifier is not used by more than one handler Interrupt identifiers are implementation defined and the Examiner cannot check that values are used only once Duplication can occur by declaring more than object of a single sub type where that type defines handlers It may also occur if interrupt identifiers are set via discriminants and two or more actual discriminants generate the same value warning control file keyword interrupt_handlers Warning 6 Machine code insertion Code insertions are ignored by the Examiner Page 76 of 95 SPARK Examiner EXM UM User Manual Release 7 3 Issue 7 3 Machine code is inherently implementation dependent and cannot be analysed by the SPARK Examiner Users are responsible for ensuring that the behaviour of the inserted machine code matches the annotation of the subprogram containing it Warning 9 The body of XXX has a hidden exception handler analysis and verification of contracts for this hand
104. messages are evident WY Flow Error 30 The variable XXX is imported but neither referenced nor exported NY Flow Error 31 The variable XXX is exported but not internally defined gi Flow Error 32 The variable XXX is neither imported nor defined WY Flow Error 33 The variable XXX is neither referenced nor exported Page 90 of 95 8 3 7 1 SPARK Examiner EXM UM User Manual Release 7 3 Issue 7 3 Flow Error 35 Importation of the initial value of variable XXX is ineffective The meaning of this message is explained in Section 4 2 of Appendix A Inconsistencies between abstract and refined dependency relations 1 1 1 1 1 Flow Error 1 The previously stated updating of XXX has been omitted XXX occurred as an export in the earlier dependency relation but neither XXX nor any refinement constituent of it occurs in the refined dependency relation Flow Error 2 The updating of XXX has not been previously stated A refinement constituent of XXX occurs as an export in the refined dependency relation but XXX does not occur as an export in the earlier dependency relation Flow Error 3 The previously stated dependency of the exported value of XXX on the imported value of YYY has been omitted The dependency of the exported value of XXX on the imported value of YYY occurs in the earlier dependency relation but in the refined dependency relation no constituents of XXX depend on any constituents of YYY
105. n identifier which SPARK requires to be an entire composite constant represents something other than this Semantic Error 181 Invalid policy for constant proof rule generation Semantic Error 182 Rule Policy for YYY XXX already declared in current scope Issued when a rule policy has already been declared for this constant within this declarative region This rule policy will be ineffective Semantic Error 190 The name XXX already appears in the inherit clause Semantic Error 191 The name XXX already appears in the with clause Semantic Error 200 The parameter XXX is neither imported nor exported Each formal parameter of a subprogram shall be imported or exported or both Semantic Error 201 The global variable XXX is neither imported nor exported Every variable in a global definition shall be either imported or exported or both Semantic Error 250 The Size value for type XXX has already been set Semantic Error 251 The attribute value for XXX Size must be of an integer type Semantic Error 252 The attribute value for XXX Size must be a static simple expression The value of Size must be static and must be of an integer type Semantic Error 253 The attribute value for XXX Size must not be negative The value of Size must be a positive integer or zero Semantic Error 254 The Size attribute can only be specified for a first subtype Setting Size for a user defined non first subtype is not permitted See Ada95 LR
106. n variable Protected moded own variables are refined onto a set of virtual elements with the same mode As such private elements are not allowed Semantic Error 1929 Unexpected declare annotation Procedure XXX should have the declare annotation on the specification Declare annotations cannot appear on the procedure body if it appears on the procedure specification Semantic Error 1930 Task XXX does not appear in the own task annotation for this package A task has been declared that is not specified as an own task of the package Page 71 of 95 KKK KKK KKK KKK KKK KKK KKK KKK KKK KKK KKK KKK SPARK Examiner EXM UM User Manual Release 7 3 Issue 7 3 Semantic Error 1931 Task XXX does not have a definition A task name appears in the own task annotation for this package but is never declared Semantic Error 1932 The priority for protected object XXX does not match that given in the own variable declaration The priority given in the priority property must match that given in the protected type Semantic Error 933 A pragma Priority is required for the main program when Ravenscar Profile is enabled When SPARK profile Ravenscar is selected all tasks protected objects and the main program must explicitly be assigned a priority Semantic Error 1934 Priority ceiling check failure the priority of YYY is less than that of XXX The active priority of a task is the higher of its base priority
107. nal subject to any additional rules below In package Standard type Integer and all _Integer types are expected to be signed integer types Similarly type Float and all _Float types are expected to be constrained floating point types In package System which may only be included in SPARK95 mode the following well formedness checks apply e Type Address must be private The declaration of type Address implicitly declares a deferred constant System Null_Address of type Address e Storage_Unit Word_Size Max_Binary_Modulus Min_Int Max_Int Max_Digits Max_Base_Digits and Max_Mantissa are all expected to be named integers e Fine_Delta is expected to be a named real e Subtype Any_Priority is expected to have Integer as its parent type additionally if Any_Priority is specified both Priority and Interrupt_Priority must also be specified e Subtypes Priority and Interrupt_Priority are expected to have Any_Priority as their parent types The range of Priority must include at least 30 values The declaration of subtype Priority implicitly defines a constant Default_Priority of type Priority e The following relations must hold between Any_Priority Priority and Interrupt_Priority Any_Priority First Priority First Any_Priority Last Interrupt_Priority Last Priority Last 1 Interrupt_Priority First e Max_Binary_Modulus must be a positive power of 2 In addition standard SPARK rule
108. ncomplete Page 82 of 95 TH SPARK Examiner EXM UM User Manual Release 7 3 Issue 7 3 The Examiner checks that no more than one task can suspend on a single object and that there is no potential sharing of unprotected data between tasks These checks depend on the accuracy of the annotations on the task types withed by the main program If these annotations contain errors then any reported violations of the shared variable and max one in a queue checks will be correct however the check may be incomplete The errors in the task annotations should be corrected Page 83 of 95 6 4 SPARK Examiner EXM UM User Manual Release 7 3 Issue 7 3 Notes The Examiner may also produce the following messages which draw the user s attention to points which are considered worthy of note but which are considered to be less serious than the warnings described above Some of these messages may be suppressed by the use of the warning control file as described in section 4 3 where indicated below Note Ada 83 language rules selected Issued when the Examiner is used in SPARK 83 mode Note Information flow analysis not carried out This is issued as a reminder that information flow analysis has not been carried out in this run of the Examiner information flow errors may be present undetected in the text analysed Note 1 This dependency relation was not used for this analysis and has not been checked for accuracy Issued wh
109. ned by System Max_Digits Semantic Error 786 The number of digits specified exceeds the value defined for System Max_Base_Digits The maximum decimal precision for a floating point type where a range specification has been included is defined by System Max_Base_Digits Semantic Error 787 Digits value must be positive Semantic Error 788 Delta value must be positive Semantic Error 789 The only currently supported type attribute in this context is Base Semantic Error 790 A base type assertion requires a type here Semantic Error 791 The base type in this assertion must be a predefined type Predefined types are those defined either by the language or in package Standard using the configuration file mechanism Semantic Error 792 The types in this assertion must both be either floating point or signed integer Semantic Error 793 The base type in a base type assertion must have a defined range The ranges for the predefined types will generally be specified in the target configuration file Semantic Error 794 The range of the base type in a base type assertion must be at least as large as the type which is the subject of the assertion Semantic Error 795 A base type assertion must be in the same declarative region as that of the full type definition Semantic Error 796 This type already has a base type defined either it already has a base type assertion or it is a predefined type If the type which is the su
110. niversal expression may not be implicitly converted to a modular type here Right hand operand requires qualification to type XXX A universal expression cannot be used as the right hand operand of a binary operator if the left hand operand is of a modular type Qualification of the right hand expression is required in this case Semantic Error 811 Unnecessary others clause case statement is already complete Semantic Error 820 Abstract types are not currently permitted in SPARK Only non abstract tagged types are currently supported It is hoped to lift this restriction in a future Examiner release Semantic Error 821 This type declaration must be a tagged record because it s private type is tagged If a type is declared as tagged private then its full declaration must be a tagged record Semantic Error 1822 XXX is not a tagged type only tagged types may be extended In SPARK new can only be used to declare a type extension other derived types are not permitted Semantic Error 823 This type may not be extended in the same package in which it is declared SPARK only permits types from another library package to be extended This rule prevents overloading of inherited operations Semantic Error 824 This package already extends a type from package XXX Only one type extension per package is permitted SPARK only permits one type extension per package This rule prevents overloading of inherited operations Semantic Err
111. nscar profile is selected Support for concurrent features of the SPARK language including protected objects tasking etc are only supported when the Ravenscar profile is selected Semantic Error 851 The parameter to pragma Atomic must be a simple_name The parameter to pragma Atomic must be a simple_name and may not be passed using a named association Semantic Error 852 pragma Atomic may only appear in the same immediate scope as the type to which it applies This is an Ada rule pragma Atomic takes a local name see LRM 13 1 1 Note that this precludes the use of pragma Atomic on a predefined type Semantic Error 853 pragma Atomic may only apply to a scalar base type pragma Atomic may only be applied to base types that are scalar i e enumeration types integer types real types modular types The type must not be private Semantic Error 854 pragma Atomic takes exactly one parameter Semantic Error 855 The type of own variable XXX is not consistent with its modifier An own variable with a task modifier must be of a task type A task own variable must have the task modifier An own variable with a protected modifier must be a protected object suspension object or pragma atomic type A protected or suspension object own variable must have the protected modifier Semantic Error 858 A variable that appears in a protects property list may not appear in a refinement clause A variable in a protects list is effectively p
112. nt subprogram impossible Another message more precisely identifying the problem will be placed in the VCG file NY Program has a cyclic path without an assertion SPARK generates VCs for paths between cutpoints in the code these must be chosen by the developer in such a way that every loop traverses at least one cutpoint If the SPARK Examiner detects a loop which is not broken by a cutpoint it cannot generate verification conditions for the subprogram in which the loop is located and instead issues this warning This can only be corrected by formulating a suitable loop invariant assertion for the loop and including it as an assertion in the SPARK text at the appropriate point I Unable to create output files This message is echoed to the screen if the Examiner is unable to create output files for the VCs or PFs being generated for instance if the user does not have write permission for the current directory WW Unexpected node kind in main tree This message indicates corruption of the syntax tree being processed by the VC Generator It should not be seen in normal operation Please contact Praxis High Integrity Systems if it is produced MN Warning output file name has been truncated Echoed to the screen if an output file name is longer than the limit imposed by the operating system and has been truncated Section 4 6 describes how the output file names are constructed If this message is seen there is a possibility that the output
113. nual Release 7 3 Issue 7 3 Semantic Error 725 Protected function or variable XXX may only appear directly in an assignment or return statement To avoid ordering effects protected functions may only appear directly in assignment or return statements They may not appear as actual parameters or in any other form of expression Ordering effects occur because the global state referenced by the protected function may be updated by another process during expression evaluation Semantic Error 730 A loop with no iteration scheme or exit statements may only appear as the last statement in the outermost scope of the main subprogram or a task body when using the Ravenscar profile If a loop has neither an iteration scheme nor any exit statements then it will run forever Any statements following it will be unreachable SPARK only allows one such loop which must be the last statement of the main program Semantic Error 750 The identifier YYY XXX is either undeclared or not visible at this point An array type may not be used as its own index type The type mark used for the index of an array type declaration must not be the same as the name of the array type being declared Semantic Error 751 The identifier YYY XXX is either undeclared or not visible at this point A record type may not include fields of its own type The type mark given for a field in a record type declaration must not be the same as the name of the record type being declar
114. o applies to a parameter of a private type if its full declaration is scalar Semantic Error 1339 Subprogram XXX was not declared in package YYY Semantic Error 340 Only operators may be renamed in package specifications User declared subprograms may not be renamed in package specifications although the implicitly declared function subprograms associated with operators may be Semantic Error 1341 A range may not appear here Issued if a range is found where a single value is expected for example if an array slice is constructed Semantic Error 342 This proof annotation should be placed with the declaration of subprogram XXX Page 52 of 95 KKK KKK KKK KKK KKK KKK KKK KKK KKK KKK KKK KKK KKK KKK SPARK Examiner EXM UM User Manual Release 7 3 Issue 7 3 Like global and derives annotations proof annotations should be placed on the first appearance of a subprogram There may also be a requirement for a second proof annotation on a subprogram body where it references an abstract own variable Semantic Error 1343 Unexpected proof annotation all annotations required for subprogram XXX have already occurred Issued if a second proof annotation for a subprogram is found but the subprogram does not reference any abstract own variables A second annotation is only required where it is necessary to express both an abstract external and a refined internal view of an operation Semantic Error
115. o prevent more than one thread being suspended on the same item at any one time A thread is one of the main program a task an interrupt handler Semantic Error 940 XXX is a protected own variable Protected variables may not be used in proof contexts The use of protected variables in pre and postconditions or other proof annotations is not currently supported Protected variables are volatile because they can be changed at any time by another program thread and this may invalidate some common proof techniques The prohibition of protected variables does not prevent proof of absence of run time errors nor proof of protected operation bodies See the manuals Generation of VCs and Generation of RTCs for more details Semantic Error 941 The type of own variable XXX must be local to this package The type used to an announce an own variable with a protects property must be declared in the same package Semantic Error 942 Only one instance of the type XXX is allowed Type XXX has a protects property This means there can be only one object in the package that has this type or any subtype of this type Page 72 of 95 KKK KKK KKK KKK KKK KKK KKK KKK KKK KKK KKK KKK KKK SPARK Examiner EXM UM User Manual Release 7 3 Issue 7 3 Semantic Error 943 The name XXX cannot appear in a protects list All items in a protects list must be unprotected own variables owned by this package Semantic Er
116. o variable XXX which may be undefined The expression may be that in an assignment or return statement an actual parameter or a condition occurring in an if or case statement an iteration scheme or exit statement The Examiner has identified at least one syntactic path to this point where the variable has NOT been given a value Conditional data flow errors are extremely serious and must be carefully investigated NOTE the presence of random and possibly invalid values introduced by data flow errors invalidates proof of exception freedom for the subprogram body which contains them All reports of data flow errors must be eliminated or shown to be associated with semantically infeasible paths before attempting exception freedom proofs See the manual Generation of RTCs for SPARK Programs for full details Warning 504 Statement contains reference s to variable XXX which may be undefined The statement here is a procedure call and the variable XXX may appear in an actual parameter whose value is imported when the procedure is executed If the variable XXX does not occur in the actual parameter list it is an imported global variable of the procedure named in its global definition The Examiner has identified at least one syntactic path to this point where the variable has NOT been given a value Conditional data flow errors are extremely serious and must be carefully investigated NOTE the presence of random and possibly invalid values introd
117. ocedure or function is called before its body has been declared Re ordering of subprogram bodies in the package concerned will be required Semantic Error 164 Actual parameter of mode in out or out must be the name of a variable Semantic Error 165 This parameter is overlapped by another one which is exported Violation of the anti aliasing rule Semantic Error 166 This parameter is overlapped by an exported global variable Violation of the anti aliasing rule Semantic Error 167 Imported variable XXX is not named in the initialization specification of its package Issued when an own variable which is imported into the main program procedure or a task when the Ravenscar profile is enabled has not been declared as being initialized by its package At the main program level the only imports that are permitted are initialized own variables of inherited packages There are two possible cases to consider 1 the main program should be importing the variable in which case it should be annotated in its package with initializes and of course actually initialized in some way or be an external variable or protected variable which is implicitly initialized or 2 the own variable concerned is not initialized at elaboration should not therefore be considered an import to the main program and should be removed from the main program s import list Semantic Error 168 XXX is a loop parameter whose updating is not allowed Semantic E
118. of VCs associated Page 23 of 95 M 4 5 1 4 6 4 6 1 ss SPARK Examiner EXM UM User Manual Release 7 3 Issue 7 3 with Run time Checks there is also a positive impact on some wellformation checks The use of the target compiler data file is mutually exclusive with the use of the target configuration file It is only possible to supply values for Integer first Integer last and their Long_Integer equivalents the Examiner will also deduce the values of Positive last and Natural last from Integer last The use of the target compiler data file is now deprecated and it is recommended that new users use the target configuration file detailed at 4 6 The format of each line of the file is line typemark attribute_name integer based_literal typemark integer long_integer attribute_name first last Note that the lines in the file do NOT end with semicolons Example integer first 327608 integer last 32767 The target configuration file This file serves a similar purpose to the target data file in that it allows implementation dependent values to be supplied to the Examiner However it is a significantly more general mechanism and has a greater positive impact on the generation and simplification of VCs as well as static semantic checking The use of the target configuration file is mutually exclusive with the use of the target data file The use of the target configurat
119. of the same name and kind Semantic Error 645 Actual array element XXX is not compatible with the element type YYY of the generic formal parameter Page 57 of 95 KKK KKK KKK KKK KKK KKK KKK KKK KKK KKK SPARK Examiner EXM UM User Manual Release 7 3 Issue 7 3 See ALRM 12 5 Each generic formal type parameter must be supplied with an actual type which is of a compatible class Note that SPARK does not have default values for such associations Semantic Error 646 Actual array index XXX is not compatible with the index type YYY of the generic formal parameter See ALRM 12 5 Each generic formal type parameter must be supplied with an actual type which is of a compatible class Note that SPARK does not have default values for such associations Semantic Error 647 Actual array XXX has more dimensions than formal arrayYYY See ALRM 12 5 Each generic formal type parameter must be supplied with an actual type which is of a compatible class Note that SPARK does not have default values for such associations Semantic Error 648 Actual array XXX has fewer dimensions than formal array YYY See ALRM 12 5 Each generic formal type parameter must be supplied with an actual type which is of a compatible class Note that SPARK does not have default values for such associations Semantic Error 649 Actual array XXX is constrained but the associated formal YYY is unconstrained See ALRM 12 5 Each generic formal ty
120. of this declaration Semantic Error 407 This choice overlaps a previous one Choices in case statements and array aggregates may not overlap Semantic Error 408 Case statement is incomplete A case statement must either explicitly supply choices to cover the whole range of the sub type of the controlling expression or it must supply an others choice Semantic Error 409 Empty range specified In SPARK no static range is permitted to be null Semantic Error 410 Choice out of range The choices in case statements and array aggregates must be within the constraints of the appropriate sub type Semantic Error 411 Others clause required Issued where an others clause is required to satisfy the Ada language rules Semantic Error 412 Explicit boolean range not permitted Semantic Error 413 Invalid range constraint Page 53 of 95 KKK KKK KKK KKK KKK KKK KKK KKK KKK KKK KKK KKK KKK KKK KKK KKK SPARK Examiner EXM UM User Manual Release 7 3 Issue 7 3 Issued where a range constraint is outside the range of the sub type to which the constraint applies Semantic Error 414 Array aggregate is incomplete An array aggregate must either explicitly supply values for all array elements or provide an others clause Semantic Error 415 Too many entries in array aggregate Issued where an array aggregate using positional association contains more entries than required by the array index type
121. or 20 Expression contains reference s to undefined variable XXX The expression may be that in an assignment or return statement an actual parameter or a condition occurring in an if or case statement an iteration scheme or exit statement NOTE the presence of random and possibly invalid values introduced by data flow errors invalidates proof of exception freedom for the subprogram body which contains them All unconditional data flow errors must be eliminated before attempting exception freedom proofs See the manual Generation of RTCs for SPARK Programs for full details I Flow Error 23 Statement contains reference s to undefined variable XXX The statement here is a procedure call or an assignment to an array element and the variable XXX may appear in an actual parameter whose value is imported when the procedure is executed If the variable XXX does not occur in the actual parameter list it is an imported global variable of the procedure named in its global definition NOTE the presence of random and possibly invalid values introduced by data flow errors invalidates proof of exception freedom for the subprogram body which contains them All unconditional data flow errors must be Page 87 of 95 SPARK Examiner EXM UM User Manual Release 7 3 Issue 7 3 eliminated before attempting exception freedom proofs See the manual Generation of RTCs for SPARK Programs for full details Warning 501 Expression contains reference s t
122. or 825 Type XXX expected in order to complete earlier private extension Since SPARK only permits one type extension per package it follows that the declaration new XXX with private in a package visible part must be paired with new XXX with record in its private part The ancestor type XXX must be the same in both declarations Semantic Error 826 Type extension is not permitted in SPARK 83 Type extension is an Ada 95 feature not included in Ada or SPARK 83 Semantic Error 827 The actual parameter associated with a tagged formal parameter in an inherited operation must be an object not an expression There are several reasons for this SPARK rule Firstly Ada requires tagged parameters to be passed by reference and so an object must exist at least implicitly Secondly in order to perform flow analysis of inherited subprogram calls the Examiner needs identify what subset of the information available at the point of call is passed to and from the called subprogram Since information can only flow through objects it follows that actual parameter must be an object Semantic Error 1828 Tagged types and tagged type extensions may only be declared in library level package specifications Page 64 of 95 KKK KKK KKK KKK KKK KKK KKK KKK KKK KKK KKK SPARK Examiner EXM UM User Manual Release 7 3 Issue 7 3 This SPARK rule facilitates the main uses of tagged types while greatly simplifying visibility rules
123. orate_Body has one parameter Semantic Error 606 This expression does not represent the expected package name XXX Issued when the parameter to a pragma Elaborate_Boay is invalid Semantic Error 607 This package requires a body and must therefore include either pragma Elaborate_Body or a subprogram declaration Issued where a package specification contains no subprogram declarations but whose own variables as specified in the package annotation are not all declared and initialized where appropriate in the package specification This is because such a package is not allowed a body in Ada 95 unless either the pragma is given or a subprogram declared Semantic Error 608 Reduced accuracy subtypes of real numbers are considered obsolescent and are not supported by SPARK Semantic Error 609 This entity cannot be assigned to Semantic Error 610 Child packages may not be used in SPARK83 Semantic Error 611 Illegal use of deferred constant prior to its full declaration Semantic Error 7613 Illegal name for body stub Page 55 of 95 KKK KKK KKK KKK KKK KKK KKK KKK KKK KKK KKK KKK KKK SPARK Examiner EXM UM User Manual Release 7 3 Issue 7 3 Issued if a dotted name appears in a body stub as in package body P Q is separate No legal stub could ever have such a name Semantic Error 614 Child packages may be declared only at library level Issued if an attempt is made to declare a child packa
124. ormed lower in the calling hierarchy while still permitting full protection from data flow errors and language violations at the top of the calling tree e g in the system main loop or scheduler Additionally the use of moded global as a substitute for derives annotations may be appropriate for some perhaps less critical systems SPARK 83 data flow analysis The data flow analysis option is not available when operating the Examiner in SPARK 83 mode this is because Ada 83 language rules prevent the modes of a parameter being sufficient to determine whether it is an import or an export Users who have a need for data flow analysis of SPARK 83 programs should contact Praxis High Integrity Systems for guidance Error messages Data flow and information flow errors may be either unconditional or conditional An error is unconditional if it applies to all paths through a program and consequently to all its possible executions In signalling flow errors of this kind error messages always begin with three exclamation marks A conditional flow error is one that applies to some but not all program paths To determine whether such an error can manifest itself in practice it is necessary to establish whether any of the paths to which the error applies are executable which involves their semantic analysis Error reports on conditional errors begin with three question marks Data flow errors References to undefined variables IW Flow Err
125. ort Semantic Error 507 Global variable XXX is of mode in out and must appear as an export Issued where a procedure has both a global annotation with modes and a dependency relation and a global variable of mode in out is not listed as an export in the dependency relation Semantic Error 508 This global variable is a parameter of mode in and can only have the global mode in Semantic Error 550 use type clauses may only be used in SPARKQ5 clause ignored Semantic Error 551 All operators for type XXX are already visible Semantic Error 552 The type XXX already appears in the use type clause Semantic Error 554 XXX is a limited private type for which no operators can be made visible Semantic Error 555 XXX is not mentioned in an earlier with clause of this compilation unit Semantic Error 600 pragma Import has a minimum of 2 and a maximum of 4 parameters Semantic Error 601 Convention Entity External_Name or Link_Name expected Semantic Error 602 An association for XXX has already been given Semantic Error 603 No association for XXX was given Semantic Error 604 This package may not have a body consider use of pragma Elaborate_Body In Ada 95 a package body is illegal unless it is required for the purpose of providing a subprogram body or unless this pragma is used This error is issued where a package body is found for a package whose specification does not require a body Semantic Error 605 pragma Elab
126. orter unique representations of these options are recognised Each language feature placed in the warning control file selects that feature for summary rather than full reporting Pragma all selects all pragmas other than those such as pragma Import which are recognised by the Examiner for summary reporting alternatively a number of pragmas can be selected individually by name Example of a warning control file A warning control file with the following contents selected using the warning_file option would cause warning messages connected with direct updating of package own variables and with the pragmas Page and List to be summarised all other warnings would be reported in full direct pragma list pragma page Page 22 of 95 M 4 4 4 4 1 4 4 2 4 5 SPARK Examiner EXM UM User Manual Release 7 3 Issue 7 3 The meta file A meta file is a list of filenames this allows the user to specify that this list of files is to be Examined simply by naming the meta file preceded by the character on the command line The files specified in this way behave exactly as if they had been specified on the command line so a listing file is produced for each unless specifically suppressed This method allows the repeated Examination of groups of files without the need to specify them on the command line The default extension for a meta file name is smf Meta files can include Ada style comments File format Meta
127. ouble end P This would produce the following directories and files if VCs were generated e Adirectory called p containing a directory called double and files double fdl double ris and double vcg e Files sum fdl sum ris and sum vcg within directory p double VCs or PFs generated from subprograms in child packages appear in a similar directory sub tree rooted at a directory with the name of the parent package followed by a single underbar For example generation of VCs from package Parent Child is procedure Inc X in out Integer derives X from X end Parent Child would result in a directory called parent_ containing a directory called child containing files inc fdl inc rls and inc vcg If the length of any file name exceeds the maximum length permitted by the operating system it is truncated Note that this could lead to ambiguous file names in some cases causing the output from more than one subprogram to be written to files of the same name A warning message is displayed if file name truncation occurs see section Error Reference source not found Flat structure The name of each file generated is created by concatenating the name of the subprogram being analysed with name of each package or subprogram enclosing it separating each element with Page 29 of 95 M 4 7 3 4 8 4 8 1 oss SPARK Examiner EXM UM User Manual Release 7 3 Issue 7 3 underbar characters Thus VCs for subprogram P in p
128. owing changes to warn nowarn and nolisting options Issue 6 2 5th January 2006 Updated for Examiner release 7 2d15 Issue 7 3 12th January 2006 Updated for Examiner release 7 3 Changes forecast Nil Document references Page 95 of 95
129. pe Any_Priority is Integer range 0 gL subtype Priority is Any_Priority range 0 30 subtype Interrupt_Priority is Any Priority range 31 end System 1 189731495357231771 E 4932 Sls Page 25 of 95 M 4 6 3 SPARK Examiner EXM UM User Manual Release 7 3 Issue 7 3 Legality rules The Examiner supports package specifications in the target configuration file In SPARK95 mode both package Standard and package System may be specified In SPARK83 mode only package Standard is allowed The packages may appear in any order In package Standard the following types may be declared e Integer e Float e Any signed integer type which has _Integer as a suffix and e Any floating point type which has _Float as a suffix In package System the type Address may be declared as may the following subtypes e Any_Priority e Priority and e Integer_Priority Additionally the following named numbers may be defined e Storage_Unit e Word_Size e Max_Binary_Modulus Min_Int Max_lnt e Max_Digits e Max_Base_Digits Max_Mantissa and Fine_Delta Page 26 of 95 M 4 6 4 4 6 5 SPARK Examiner EXM UM User Manual Release 7 3 Issue 7 3 Static semantics The package specifications are expected to accord to the normal SPARK rule that the package name be specified in the end clause All declarations within the packages are optio
130. pe parameter must be supplied with an actual type which is of a compatible class Note that SPARK does not have default values for such associations Semantic Error 650 Actual array XXX is unconstrained but the associated formal YYY is constrained See ALRM 12 5 Each generic formal type parameter must be supplied with an actual type which is of a compatible class Note that SPARK does not have default values for such associations Semantic Error 700 Mode in out may not be applied to own variables or their refinement constituents Own variables may be given a mode to indicate that they are system level inputs or outputs i e they obtain values from or pass values to the external environment Since effective SPARK design strictly separates inputs from outputs the mode in out is not permitted Semantic Error 701 The mode of this refinement constituent is not consistent with its subject XXX If an abstract own variable is given a mode then its refinement constituents must all be of the same mode Semantic Error 702 Own variable XXX must be given the mode in to match its earlier announcement Issued if an own variable of an embedded package is not given the same mode as the earlier refinement constituent that announced it would exist Semantic Error 703 Own variable XXX must be given the mode out to match its earlier announcement Issued if an own variable of an embedded package is not given the same mode as the earlier
131. pilot Altitude Autopilot Heading states that the private children of package Autopilot are called Autopilot Altitude and Autopilot Heading Other index entries would then be used in the normal way as in the previous example above to locate the relevant source files Example index files queue idx SuperIndex is in library QueueOperations specification is in queue_ QueueOperations body is in queue Stacks auxindex is in stacks stacks idx Stacks specification is in stacks_ Stacks body is in stacks Stacks Pop subunit is in stackpop Stacks Push subunit is in stackpush In the above example queue_and queue refer to files queue_ ada and queue ada which contain Ada source code note that file names are case sensitive on Unix systems The name stacks refers to file stacks idx which is another auxiliary index file Finally library refers to a further Super index file Page 21 of 95 M 4 3 4 3 1 4 3 2 oss SPARK Examiner EXM UM User Manual Release 7 3 Issue 7 3 library idx in which the search will recommence if a required unit cannot be found in the index file supplied and the auxiliary indexes specified within it The warning control file The Examiner generates semantic warnings when certain program constructs are found The warnings are raised because the Examiner identifies properties of the SPARK source which although not illegal may be of interest to the user or because certain language features
132. portation is not allowed Semantic Error 714 The own variable or constituent XXX is of mode out and may not appear in a dependency clause as an import Own variables with mode out denote system level outputs their importation is not allowed Semantic Error 715 Function XXX references external stream variables and may only appear directly in an assignment or return statement To avoid ordering effects functions which globally access own variables which have modes indicating that they are connected to the external environment may only appear directly in assignment or return statements They may not appear as actual parameters or in any other form of expression Page 59 of 95 KKK KKK KKK KKK KKK KKK KKK KKK KKK SPARK Examiner EXM UM User Manual Release 7 3 Issue 7 3 Semantic Error 716 External stream variable XXX may only appear directly in an assignment or return statement or as an actual parameter to an unchecked conversion To avoid ordering effects own variables which have modes indicating that they are connected to the external environment may only appear directly in assignment or return statements They may not appear as actual parameters other than to instantiations of Unchecked_Conversion or in any other form of expression Semantic Error 717 External stream variable XXX is of mode in and may not be assigned to Own variables with mode in represent inputs to the system f
133. property which cannot suspend Or you have used an item in a suspends list that does not have the suspendable property An object can only suspend if it is a suspension object or a protected type with an entry Semantic Error 910 Name XXX must appear in the suspends list property for the enclosing unit Protected entry calls and calls to Ada Synchronous_Task_Control Suspend_Until_True may block the currently executing task SPARK requires you announce this fact by placing the actual callee name in the suspends list for the enclosing unit Semantic Error 911 The argument in pragma Priority for the main program must be an integer literal or a local constant of static integer value If the main program priority is not an integer literal then you should declare a constant that has the required value in the declarative part of the main program prior to the position of the pragma Semantic Error 1912 This call contains a delay property that is not propagated to the enclosing unit The call being made has a declare annotation that contains a delay property SPARK requires that this property is propagated up the call chain and hence must appear in a declare annotation for the enclosing unit Semantic Error 913 This call has a name in its suspends list which is not propagated to the enclosing unit The call being made has a declare annotation that contains a suspends list SPARK requires that the entire list is propagated up the call chain and
134. resents a package which contains a task or an interrupt handler then the partition level analysis performed by the Examiner will be incomplete Such packages must be inherited as well as withed Warning 392 External variable XXX may have an invalid representation Where values are read from external variables i e variables connected to the external environment there is no guarantee that the bit pattern read will be a valid representation for the type of the external variable Unexpected behaviour may result if invalid values are used in expressions For SPARK 95 the use of attribute Valid is strongly recommended see ALRM 13 9 2 For SPARK 83 external variables should always be read into variables of a type for which any bit pattern would be a valid representation e g a word and then range checked before conversion to the actual type desired Note that when the Examiner is used to generate Page 79 of 95 SPARK Examiner EXM UM User Manual Release 7 3 Issue 7 3 run time checks it will not be possible to discharge those involving external variables unless these steps are taken Boolean external variables require special care since the Examiner does not generate run time checks for Boolean variables use of Valid is essential when reading Boolean external variables More information on interfacing can be found in the INFORMED manual warning control file keyword external_assignment Warning 393 External variable XXX may have an
135. rom the external environment As such assigning to them does not make sense and is not permitted Semantic Error 718 External stream variable XXX is of mode out and may not be referenced Own variables with mode out represent outputs to the external environment from the system As such referencing them does not make sense and is not permitted Semantic Error 719 External stream variables may not be referenced or updated during package elaboration Own variables with modes represent inputs and outputs between the external environment and the system Referencing or updating them during package elaboration would introduce ordering effects and is not permitted Semantic Error 720 Variable XXX is an external stream variable and may not be initialized at declaration Own variables with modes represent inputs and outputs between the external environment and the system Referencing or updating them during package elaboration would introduce ordering effects and is not permitted Semantic Error 7721 This refined function global annotation may not reference XXX because it is an external stream variable whose abstract subject YYY does not have a mode Functions may be used to reference external stream variables and the Examiner generates the appropriate information flow to show that the value returned by the function is volatile If the abstract view of the same function shows it referencing an own variable which is not an e
136. ror 944 The name XXX is already protected by YYY The name XXX appears in more than one protects list The first time it appeared was for own variable YYY XXX should appear in at most one protects list Semantic Error 945 The property XXX must be given a static expression for its value This property can only accept a static expression Semantic Error 946 The own variable XXX must only ever be accessed from operations in protected type YYY The own variable XXX is protected by the protected type YYY and hence must never be accessed from anywhere else Semantic Error 947 The own variable XXX appears in a protects list for type YYY but is not used in the body The protected type YYY claims to protect XXX via a protects property However the variable XXX is not used by any operation in YYY Semantic Error 948 The type of own variable or task XXX must be a base type Own tasks and protected own variables of a protected type must be announced using the base type The subsequent variable declaration may be a subtype of the base type Semantic Error 949 Unexpected partition annotation a global annotation may only appear here when the Ravenscar profile is selected When the sequential SPARK profile is selected the global and derives annotation on the main program describes the entire program s behaviour No additional partition annotation is required or permitted Note that an annotation must appear here if the Ravenscar profile is s
137. rotected and hence cannot be refined Semantic Error 859 A protected own variable may not appear in a refinement clause Protected state cannot be refined or be used as refinement constituents Semantic Error 860 Own variable XXX appears in a protects list and hence must appear in the initializes clause Protected state including all refinement constituents must be initialized Semantic Error 863 Own variable XXX is protected and may not appear in an initializes clause Page 66 of 95 KKK KKK KKK KKK KKK KKK KKK KKK KKK KKK KKK SPARK Examiner EXM UM User Manual Release 7 3 Issue 7 3 Protected own variables must always be initialized and should not appear in initializes annotations Semantic Error 864 Unexpected initialization specification all own variables of this package are either implicitly initialized or do not require initialization An own variable initialization clause and that of its refinement constituents must be consistent Semantic Error 865 Field XXX is part of the ancestor part of this aggregate and does not require a value here An extension aggregate must supply values for all fields that are part of the overall aggregate type but not those which are part of the ancestor part Semantic Error 866 The expression in a delay_until statement must be of type Ada Real_Time Time When the Ravenscar Profile is selected the delay until statement may be used The argument of this
138. rror 169 Global variables of function subprograms must be of mode in It is an important property of SPARK that functions cannot have side effects therefore only the reading of global variable is permitted It is usually convenient to omit modes from function global annotations but use of mode in is permitted Semantic Error 170 XXX is a formal parameter of mode in whose updating is not allowed Semantic Error 171 XXX is a formal parameter of mode out whose value cannot be read Semantic Error 172 The actual parameter associated with an exported formal parameter must be an entire variable Issued if an actual parameter which is an array element is associated with an exported formal parameter in a procedure call Exported parameters must be either entire variables or a record field Semantic Error 173 This exported parameter is named in the global definition of the procedure Page 48 of 95 KKK KKK KKK KKK KKK KKK KKK KKK KKK KKK KKK KKK KKK KKK KKK KKK KKK SPARK Examiner EXM UM User Manual Release 7 3 Issue 7 3 Violation of the anti aliasing rule Semantic Error 1174 XXX is not an own variable Occurs in initialization specifications if something other than a variable is listed as being initialized Semantic Error 175 Information flow from XXX to YYY violates the selected information flow policy Semantic Error 180 Entire composite constant expected Issued when a
139. rror Reference source not found as reserved words This action is provided to give backward compatibility with the no longer supplied Standard Examiner which by default did not recognise FDL identifiers as reserved words version ve If this switch appears anywhere on an Examiner command line then the Examiner simply prints its banner information the date and static limits to the console All further processing of command line switches and analysis is terminated This option is useful for quickly checking the version number licence information and static limits of an Examiner help Prints a summary of Examiner command line options to the screen original_flow_errors O This switch affects the formatting of the flow errors printing one line for every error see section 8 3 4 error_explanations er option off Option is one of off first_occurrence every_occurrence which can be abbreviated to o f and e respectively Selects whether explanatatory notes are appended to Examiner error messages When first_occurrence is selected the explanation appears only for the first occurrence of each different error mesage in each of the screen echo listing files and report file The use of the html switch overrides error_explanations and turns them off for the report file only this is because explanations are already only one click away when viewing the HTML report file 3 2 The Default Switch File The Examiner can read
140. s in output or dates This can be useful when using diff utilities to compare analysis results because it leaves only the significant changes in the comparison output brief b Causes on screen errors and warnings to be issued in a brief format comprising lt filename gt lt line gt lt column gt lt message gt This format is designed to allow integration with other development environments and tools nolistings nol Suppresses the generation of all listing files to suppress individual listing files see section 3 The results are always Summarised in the Page 13 of 95 SPARK Examiner EXM UM User Manual Release 7 3 Issue 7 3 N 3 1 3 Analysis Options syntax_check sy Given this switch the Examiner will only check that the source files are in the SPARK syntax Note that this does NOT check whether a text is legal SPARK and must only be used as a pre processor ada83 ad Forces the Examiner to operate according to the rules of SPARK 83 instead of the default SPARK 95 fl type information The types are information and data and may be abbreviated to i and d respectively Section Error Reference source not found describes the different types of flow analysis Note that the data flow analysis option is not enabled by default when the Examiner is being used in SPARK 83 mode Please contact Praxis High Integrity Systems if you wish to make use of this feature on SPARK
141. s is described in the manual Generation of Run time Checks for SPARK Programs e produce an obsolescent and less rigorous form of analysis called path functions Its use for this purpose is described in the manual Generation of Path Functions for SPARK Programs Page 5 of 95 SPARK Examiner EXM UM TW User Manual Release 7 3 Issue 7 3 Advice on the contents of this document may be obtained by phone 44 0 1225 823829 direct line or 44 0 1225 466991 exchange by FAX 44 0 1225 469006 by Email sparkinfo praxis his com Page 6 of 95 M 2 1 oss SPARK Examiner EXM UM User Manual Release 7 3 Issue 7 3 General description The Examiner supports several levels of analysis The Examiner supports e checking of SPARK language syntactic and static semantic rules e data flow analysis e data and information flow analysis e formal program verification via generation of verification conditions proof of absence of run time errors There is also an option to make the Examiner perform syntax checks only Using this option on a source file does not require access to any other units on which the file depends so files can be syntax checked on an individual basis This allows any syntax errors to be corrected before the file is included ina complex examination This option must only be used as a pre processor the absence of syntax errors does NOT indicate that the source text is a legal SPARK program E
142. s not boolean Issued anywhere a boolean expression is required e g in if exit and while statements and the expression provided is not of type boolean Semantic Error 95 Type mark expected Semantic Error 96 Attribute XXX is not valid with this prefix Semantic Error 97 Attribute BASE may only appear as a prefix BASE may only be used as a prefix to another attribute Semantic Error 98 This expression is not a range Semantic Error 99 Unconstrained array expected Occurs if a subtype is declared of an array which is already constrained Semantic Error 100 Floating point type mark expected Semantic Error 101 Fixed point type mark expected Semantic Error 102 This is not the name of a field of record XXX Semantic Error 103 A value has already been supplied for field XXX Semantic Error 104 No value has been supplied for field XXX Semantic Error 105 More values have been supplied than number of fields in record XXX Semantic Error 106 Range is not of the expected type Semantic Error 107 Expression is not of the expected type Actual type is XXX Expected type is YYY Semantic Error 108 Expression is not of the expected type Expected any Integer type Semantic Error 109 Expression is not of the expected type Expected any Real type Semantic Error 110 Use type clauses following an embedded package are not currently supported by the Examiner Semantic Error 111 Package renaming is not curren
143. s on redeclaration of existing identifiers empty ranges and legality of subtype ranges apply Configuration file generator An Ada source file is distributed with the Examiner which will automatically generate a valid target configuration file when compiled and run it is named confgen adb and will be located in the same directory as the Examiner binary Please note that the resultant configuration file will only be valid for SPARKQ5 usage since it includes package System The packages specifications are generated on the standard output and can be redirected to a file in the normal fashion Page 27 of 95 M 4 7 4 7 1 oss SPARK Examiner EXM UM User Manual Release 7 3 Issue 7 3 The configuration file generator will probably require some minor modification depending on whether the target compiler supports Long_Integer for example so it is suggested that the user inspect the source code before use NOTE In an environment where both host and target cross compilers are being used it is very important that the configuration file is valid for the final target computer i e using the cross compiler not the host compiler VC output file structure The output files from the VC generator are either e produced in a directory tree structure as described in section 4 7 1 this is the default for NT and Sun or e produced in a single directory as described in section 4 7 2 this is the default for VAX There are import
144. sages 5 3 Reserved words 6 Static semantic analysis 6 1 General description 6 2 Error messages 6 3 Warning messages 6 4 Notes 7 Control flow analysis 7 1 General description 7 2 Error messages 8 Data and information flow analysis 8 1 General description 8 2 Optional information flow analysis 8 3 Error messages 9 Verification condition generation 9 1 General description 9 2 Error messages 10 Static limits and associated error messages Document Control and References File under Changes history EXM UM Issue 7 3 N 11 12 16 92 92 92 93 94 94 94 Page 3 of 95 SPARK Examiner User Manual Release 7 3 Changes forecast Document references EXM UM Issue 7 3 95 95 Page 4 of 95 ss SPARK Examiner EXM UM User Manual Release 7 3 Issue 7 3 M Overview SPARK is an annotated sublanguage of Ada intended for high integrity programming The language exists in variants based on both Ada 83 and Ada 95 The SPARK language is described in a separate reports SPARK the SPADE Ada Kernel and SPARK 95 the SPADE Ada 95 Kernel which form part of the Examiner manual set these reports will be referred to here as the SPARK Definition The Examiner is operated in the same way on both SPARK 83 and SPARK 95 source code although the rules which it implements differ according to the language variant selected As well as imposing language restrictions to eliminate ambiguities and insecurit
145. sed to declare constants Protected and suspension objects are used to ensure integrity of shared objects If it is necessary to share constant data then these constructs should not be used Page 69 of 95 KKK KKK KKK KKK KKK KKK KKK KKK KKK KKK KKK KKK SPARK Examiner EXM UM User Manual Release 7 3 Issue 7 3 Semantic Error 904 Protected or suspension objects cannot be used as subprogram parameters SPARK does not currently support this feature Semantic Error 905 Protected or suspension objects cannot be returned from functions SPARK does not currently support this feature Semantic Error 906 Protected or suspension objects cannot be used in composite types Protected and suspension objects cannot be used in record or array structures Semantic Error 907 Delay until must be called from a task or unprotected procedure body You are calling delay until from an invalid construct Any construct that calls delay until must have a delay property in the declare annotation This construct must be one of a task or procedure body Semantic Error 908 Blocking properties are not allowed in protected scope Procedures in protected scope must not block and therefore blocking properties are prohibited Semantic Error 909 Object XXX cannot suspend You are either applying the suspendable property to an own variable that cannot suspend or you have declared a variable whose own variable has the suspendable
146. statement must be of type Ada Real_Time Time Semantic Error 867 Subprogram XXX contains a delay statement but does not have a delay property Any subprogram that may call delay until must have a delay property in a declare annotation Your subprogram is directly or indirectly making a call to delay until Semantic Error 868 Protected object XXX may only be declared immediately within a library package This error message is issued if a type mark representing a protected type appears anywhere other than in a library level variable declaration or library level own variable type announcement Semantic Error 869 Protected type XXX already contains an Entry declaration only one Entry is permitted The Ravenscar profile prohibits a protected type from declaring more than one entry Semantic Error 870 Protected type XXX does not have any operations at least one operation must be declared A protected type which provides no operations can never be used so SPARK requires the declaration of at least one Semantic Error 872 Variable XXX is not protected only protected items may be globally accessed by protected operations In order to avoid the possibility of shared data corruption SPARK prohibits protected operations from accessing unprotected data items Semantic Error 873 This subprogram requires a global annotation which references the protected type name XXX In order to statically detect certain bounded errors defined by the
147. ster which would make pointing at it hazardous however SPARK only permits Access on protected types which are limited and therefore always passed by reference anyway and immune from register optimization Requiring aliased on protected objects that will appear in discriminant constraints is therefore unwanted syntactic sugar only Semantic Error 896 The task type XXX does not have an associated body Issued at the end of a package body if a task type declared in its specification contains neither a body nor a body stub for it Semantic Error 897 The protected type XXX does not have an associated body Issued at the end of a package body if a protected type declared in its specification contains neither a body nor a body stub for it Semantic Error 898 XXX is not a protected or task type which requires a body Issued if a body or body stub for a task or protected type is encountered and there is no matching specification Semantic Error 899 A body for type XXX has already been declared Issued if a body or body stub for a task or protected type is encountered and an earlier body has already been encountered Semantic Error 901 Suspension object XXX may only be declared immediately within a library package specification or body Suspension objects must be declared at library level They cannot be used in protected type state or as local variables in subprograms Semantic Error 903 Protected or suspension object types cannot be u
148. t appear in an initializes clause Mode own variables stream variables are implicitly initialized by the environment to which they are connected and may not appear in initializes clauses since this would require their explicit initialization Semantic Error 709 Own variable or constituent XXX has mode out and may not be referenced by a function Functions are permitted to reference own variables that are either unmoded or of mode in Since mode out own variables represent outputs to the environment reading them in a function does not make sense and is not allowed Semantic Error 710 The own variable or constituent XXX is of mode in and can only have global mode in Global modes if given must be consistent with the modes of own variables that appear in the global list Semantic Error 7711 The own variable or constituent XXX is of mode out and can only have global mode out Global modes if given must be consistent with the modes of own variables that appear in the global list Semantic Error 712 The own variable or constituent XXX is of either mode in or mode out and may not have global mode in out Global modes if given must be consistent with the modes of own variables that appear in the global list Semantic Error 713 The own variable or constituent XXX is of mode in and may not appear in a dependency clause as an export Own variables with mode in denote system level inputs their ex
149. t listing file name is the name of the source file with the source file extension replaced by the listing file extension The file specs of the argumentlist specify those files whose contents are to be analysed All units found in files specified on the command line will be analysed If an extension is not included in a given file spec then the default source extension will be used see below A Meta file spec is the name of a file containing a list of files to be analysed this option is described further in section 4 4 A file spec may contain space characters however where spaces are used the entire file spec must be enclosed in double quotes The Examiner may also be invoked without command line arguments in which case it displays help information giving the options available The Command options are given in the following table Note that the option names may be abbreviated the minimum abbreviation is that given in the column specifying the command syntax Note on Rational Apex source file naming convention The Rational Apex compiler uses a file naming convention that requires a little extra care when used with the SPARK Examiner Source file names take the form p 1 ada for package specifications and p 2 ada for package bodies The following steps should be taken to handle these filenames 1 specify the complete name of each source file including the ada extension The Examiner cannot distinguish between p 1 where the intend
150. tension option will change the names of the files Suppression of listing file generation with the nolisting option will suppress generation of the HTML listing file also errors htm This file contains explanations of error messages and is referenced by the HTML versions of the report file and listing files blank htm This file ensures compatibility with all browsers This is the default file for the bottom frame as displayed when spark htm is opened Browsing the Report File The Examiner generates HTML output in a subdirectory of the current working default directory The name of this directory can be specified on the command line as a parameter to the html switch If no directory name is given then HTML is used If this directory does not exist it is created by the Examiner The HTML output can be viewed by opening the file spark htm from the HTML subdirectory in an HTML browser This file splits the browser window into two frames The top frame contains the report file which is an HTML version of the report file described in section 4 1 and acts as a navigation tool Following links in the report file opens files in the bottom frame for viewing Figure 1 shows the report file in the top frame and a listing file being viewed in the bottom frame Page 31 of 95 TH SPARK Examiner EXM UM User Manual Release 7 3 4 8 2 1 Issue 7 3 PARC HTML Output Microxoft Iriteuet Explorer pe D View Go Fwi Heb e a
151. ting file also contains links from error messages to their explanations as shown in figure 5 Page 36 of 95 M 5 1 5 2 SPARK Examiner EXM UM User Manual Release 7 3 Issue 7 3 Lexical and syntactic analysis General description The Examiner employs an LALR parsing mechanism It is similar to a conventional LALR parser except that it employs explicit shift and reduce tables The tables have been generated explicitly to facilitate the correctness proof of the parser itself Error messages The Examiner employs a uniform method of error reporting in terms of the syntactic entities terminal and non terminal symbols of the SPARK grammar Reserved words operators and punctuation marks in syntax error messages are enclosed in quotes In almost all respects the grammar employed by the Examiner is the same as that given in the SPARK Definition however some minor transformations have been applied to reduce the original grammar to LALR form The messages given are nevertheless mostly quite comprehensible Occasionally misleading messages can be produced because of the form of the SPARK grammar common cases are listed below with a brief EAR Syntax Error expected If this is reported at the end of the input file it may well be caused by the misspelling of an identifier in a hide directive The parser then skips all the following text looking for the misspelled identifier but finds the end of file first where it r
152. tly supported by the Examiner Page 46 of 95 KKK KKK KKK KKK KKK KKK KKK KKK KKK KKK KKK KKK KKK KKK SPARK Examiner EXM UM User Manual Release 7 3 Issue 7 3 Semantic Error 112 A use type clause may not appear here They are only permitted as part of a context clause or directly following an embedded package specification Semantic Error 113 Private subprogram declarations are not permitted in SPARK 83 Private subprograms would not be callable in SPARK 83 and are therefore not permitted they may be declared and called in SPARK 95 Semantic Error 114 Subtype mark or Range may not be used in an expression in this context A subtype mark or an explicit Range attribute may not be used in a context where a simple expression is expected Semantic Error 120 Pragma import not allowed here because variable XXX is already initialized See ALRM B 1 24 Semantic Error 148 The abstract proof type XXX may not be used to define an own variable in another package Own variables may be type announced as being of an abstract proof type only where that type is declared later in the same package Thus own State T is legal if type T is abstract appears later in the package however own State P T is illegal if T is an abstract proof type declared in remote package P Semantic Error 149 More than one own variable has been announced as being of type XXX which may not therefore be de
153. to the loop most closely containing the expression Stable conditionals are not necessarily an error but do require careful evaluation they can often be removed by lifting them outside the loop Discrepancies between specified dependency relations and executable code The dependency relation provided with a subprogram specification explicitly in the case of a procedure implicitly for a function effectively names the subprogram imports and exports and states which initial values of imports may be used in deriving the final value of each export The SPARK Examiner also computes the import export dependency relation from the executable code and compares the specified and actual relations Any discrepancies are described by messages of the following kinds The first two messages indicates specified dependencies which are not found in the code implementation These are unconditional errors 1 1 Flow Error 50 YYY is not derived from the imported value s of XXX The item before is not derived is an export or function return value and the item s after are imports of the subprogram The message indicates that a dependency stated in the dependency relation derives annotation or implied by the function signature is not present in the code The absence of a stated dependency is always an error in either code or annotation Flow Error 50 The imported value of XXX is not used in the derivation of YYY Page 89 of 95 TH
154. type package specification Clicking here displays the Unit hes been ansigesed sany errors ace Listed below HTML listing file in the Unit never DyOZCES bottom frame as shown init type package specification Whit hee Deen snalysed any errors are Lisred helo gt 4 FA EA TAAAR EERE THEE OE HARA TENTH AAAA Liscing of SPARK Text SPARRSS Examiner with VO and ATO Generator Release 4 08a21ER 04 00 Praxis Critical Systems Bath England SPCC THT TSS ST ETS SS SKA KO ST STATE EEE TRA EEE DATE gt 19 APR 2050 10 45 46 6 z i ee oe i Figure 4 Analysis section links The analysis section links are also shown in figure 3 The source filename and listing filename are referenced and there is also a link to the HTML version of the listing file Error links If the analysis section of the report file shows that errors were found the error reports also have useful links The error message itself is linked to an explanation of the error displayed in the bottom frame see figure 4 Clicking on the line number of the error will display that line in the listing file in the bottom frame see figure 5 Note that the line number links will not work if no listing file was generated Page 34 of 95 TH SPARK Examiner EXM UM User Manual Release 7 3 Issue 7 3 SPARK HI ML ce Nolecage Unat has been analysed any errora are listed belog 2z error s ar e erming s Line 44 Pibavade c D G Biz The error messa
155. type sequential Selects a particular profile of the SPARK language which will be used during analysis Currently the only permitted profile value is the default sequential The profile value ravenscar which is only valid for SPARKQ5 selects the RavenSPARK analysis profile which allows use of concurrent language features Note that this option is not enabled by default Please contact Praxis High Integrity Systems if you wish to make use of this feature 3 1 4 Other Options annotation_character an character Allows selection of a character other than the default to indicate the start of aSPARK annotation e g anno would cause annotation to begin rather than statistics st Causes the Examiner to insert statistics concerning the consumption of internal tables at the end of the report file These statistics are described in section 4 1 nostatistics nos V Suppresses the production of statistics on the consumption of internal tables fdl_identifiers fd v This switch causes the Examiner to recognise proof related FDL identifiers see section Error Reference source not found as reserved words this has the effect of making source containing these identifiers syntactically unacceptable Page 15 of 95 TH SPARK Examiner EXM UM User Manual Release 7 3 Issue 7 3 nofdl_identifiers nofd This switch suppresses the recognition of proof related FDL identifiers see section E
156. uced by data flow errors invalidates proof of exception freedom for the subprogram body which contains them All reports of data flow errors must be eliminated or shown to be associated with semantically infeasible paths before attempting exception freedom proofs See the manual Generation of RTCs for SPARK Programs for full details 8 3 2 Data flow anomalies and ineffective statements 1 1 1 1 Flow Error 10 Ineffective statement Execution of this statement cannot affect the final value of any exported variable of the subprogram in which it occurs The cause may be a data flow anomaly i e the statement could be an assignment to a variable which is always updated again before it is read However statements may be ineffective for other reasons see Section 4 1 of Appendix A Flow Error 10 Assignment to XXX is ineffective This message always relates to a procedure call or an assignment to a record The variable XXX may be an actual parameter corresponding to a formal one that is exported otherwise XXX is an exported global variable of the procedure The message indicates that the updating of XXX as a result of the procedure call has no effect on any final values of exported variables of the calling subprogram Where the ineffective assignment is expected e g calling a supplied procedure that returns more parameters than are needed for the immediate purpose it can be a useful convention to choose a distinctive name suc
157. upt_Handler is of no use unless dynamic attachment of interrupt handlers is to be used Semantic Error 884 Pragma Attach_Handler is only permitted immediately after the corresponding protected procedure declaration in a protected type declaration Pragma Attach_Handler may only be used within a protected type declaration Furthermore it must immediately follow a protected procedure declaration with the same name as the first argument to the pragma Semantic Error 885 Pragma Attach_Handler may only be applied to a procedure with no parameters See LRM C 3 1 5 Semantic Error 887 A discriminant may only appear alone notin an expression Issued when a task or protected type priority is set using an expression involving a discriminant The use of such an expression greatly complicates the static evaluation of the priority of task or protected subtypes thus preventing the static elimination of certain Ravenscar bounded errors Semantic Error 888 Unexpected Delay XXX already has a Delay property A procedure may only have a maximum of one delay annotation Semantic Error 889 The own variable XXX must have the suspendable property Page 68 of 95 KKK KKK KKK KKK KKK KKK KKK KKK KKK KKK KKK KKK SPARK Examiner EXM UM User Manual Release 7 3 Issue 7 3 The type used to declare this object must be a protected type with and entry or a suspension object type Semantic Error 890 The name XXX alre
158. ut text may not be legal SPARK Issued when the Examiner is used solely to check the syntax of a SPARK text this does not check the semantics of a program e g the correctness of the annotations and therefore does not guarantee that a program is legal SPARK Warning 1 The identifier XXX is either undeclared or not visible at this point This warning will appear against an identifier in a with clause if it is not also present in an inherit clause Such an identifier cannot be used in any non hidden part of a SPARK program The use of with without inherit is permitted to allow reference in hidden parts of the text to imported packages which are not legal SPARK For example the body of SPARK_IO is hidden and implements the exported operations of the package by use of package TEXT_IO For this reason TEXT_IO must appear in the with clause of SPARK_IO warning control file keyword with_clauses Warning 2 Representation clause ignored by the SPARK Examiner The significance of representation clauses cannot be assessed by the Examiner because it depends on the specific memory architecture of the target system Like pragmas representation clauses can change the meaning of a SPARK program and the warning highlights the need to ensure their correctness by other means warning control file keyword representation_clauses Warning 3 Pragma ignored by the SPARK Examiner All pragmas encountered by the Examiner generate this warning While
159. value is for example too large to be evaluated using infinite precision arithmetic No value will be recorded for the expression and this may limit the Examiner s ability to detect certain sorts of errors such as numeric constraints warning control file keyword static_expressions Warning 201 This expression cannot be evaluated statically because its value may be implementation defined Raised for example when evaluating Size of a type that does not have an explicit Size representation clause Attributes of implementation defined types such as Integer Last may also be unknown to be Examiner if they are not specified in the configuration fil warning control file keyword static_expressions Page 77 of 95 SPARK Examiner EXM UM User Manual Release 7 3 Issue 7 3 Warning 202 An arithmetic overflow has ocurred Constraint checks have not been performed Raised when comparing two real numbers The examiner cannot deal with real numbers specified to such a high degree of precision Consider reducing the precision of these numbers Warning 300 VCs and PFs cannot be built for multi dimensional array aggregates Issued when an aggregate of a multi dimensional array is found Suppresses generation of VCs or PFs for that subprogram Can be worked round by using arrays of arrays Warning 301 Called subprogram exports abstract types for which RTCs are not possible Warning 302 This expression may be re ordered by a compiler Le
160. xaminer Operation The Examiner will analyse the contents of all the source files named in the Examiner command line Each file may contain any number of SPARK compilation units Within a compilation unit the body of any constituent subprogram or package may be fully implemented or hidden see SPARK Definition or replaced by a stub as appropriate For the Examiner to analyse a particular compilation unit it may require access to some other compilation units Specifically 1 toanalyse a package body the Examiner requires access to its specification 2 toanalyse a package specification or main program which inherits other packages the Examiner requires access to the specifications of all those inherited packages and to the specifications of all packages which they themselves inherit and so on 3 to analyse a sub unit the Examiner requires access to its parent The two ways in which access to these units can be provided are described below Firstly it is possible to specify all the files to be employed in an analysis in an Examiner command line either directly or indirectly by using meta files see section 4 4 In this case the Examiner will analyse all the contents of those files as it reads them in the order in which their names occur in the command line This order and the order of units within each of the files must be such that the Examiner only requires access to units which it has already analysed Page 7 of 95
161. xaminer determines whether each parameter and global is an import or an export by checking its mode Data flow analysis is then conducted using this mode information The validity of the data flow errors listed in Section 8 3 1 is completely unaffected Other error messages generated also remain valid however Some errors normally found by information flow analysis may no longer be detected For example if the Examiner in data flow analysis mode detects a stable loop see Section 8 3 3 then the loop is stable however not all cases of loop stability detectable by information flow analysis will necessarily be indicated The specific information flow error messages described in Section 8 3 4 will not appear at all It is possible to generate verification conditions including run time checks in conjunction with the data flow analysis option information flow analysis is not a prerequisite for these forms of analysis In Page 86 of 95 M 8 2 2 8 2 3 8 3 8 3 1 SPARK Examiner EXM UM User Manual Release 7 3 Issue 7 3 contrast it is not possible to generate path functions unless information flow analysis has been carried out Recommended use For new developments we recommend that global modes are supplied and that derives annotations are also supplied except where high in the calling tree their size and complexity is judged to make them of limited value This approach allows full information flow analysis to be perf
162. xternal stream then the volatility of the function is concealed The error can be removed either by making the abstract own variable a mode in stream or by using a procedure instead of a function to read the refined stream variable Semantic Error 722 The mode on abstract global variable YYY must be made in out to make it consistent with the referencing of mode in external stream constituent XXX in the refined global annotation Where a procedure references an external stream variable of mode in the Examiner constructs appropriate information flow to show that the input stream is volatile If the abstract view shows that the procedure obtains its result by simply reading an own variable which is not an external stream then the volatility is concealed The error can be removed either by making the global mode of XXX in out or making XXX an external stream variable of mode in Semantic Error 723 Variable XXX must appear in this refined global annotation Issued when a global variable which is present in the first abstract global annotation is omitted from the second refined one Semantic Error 724 Exit label must match the label of the most closely enclosing loop statement If an exit statement names a loop label then the most closely enclosing loop statement must have a matching label Page 60 of 95 KKK KKK KKK KKK KKK KKK KKK KKK KKK KKK KKK SPARK Examiner EXM UM User Ma
163. y_Priority is defined in package System then the subtypes Priority and Interrupt_Priority must also be defined if support for tasking is not required then the definition of Any_Priority may be removed Semantic Error 771 The parent type of this subtype must be Any_Priority Ada 95 requires that both Priority and Interrupt_Priority be immediate subtypes of Any_Priority Semantic Error 772 The range of Priority must contain at least 30 values LRM D 1 26 Page 61 of 95 KKK KKK KKK KKK KKK KKK KKK KKK KKK KKK SPARK Examiner EXM UM User Manual Release 7 3 Issue 7 3 Ada 95 requires that the range of the subtype Priority include at least 30 values this requirement is stated in the Ada 95 Language Reference Manual at D 1 26 Semantic Error 773 Priority First must equal Any_Priority First LRM D 1 10 Ada 95 requires that task priority tyoes meet the following criteria the second of which is relevant to this e subtype Any_Priority is Integer range implementation defined e subtype Priority is Any_Priority range Any_Priority First implementation defined e subtype Interrupt_Priority is Any_Priority range Priority Last 1 Any_Priority Last Semantic Error 7 74 Interrupt_Priority First must equal Priority Last 1 LRM D 1 10 Ada 95 requires that task priority types meet the following criteria the third of which is relevant to this e subtype Any_Priority is Integer range implementation defin

SPARK Examiner User Manual – Release 7.3 [NT]

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SPARK Examiner User Manual – Release 7.3 [NT]