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1. TERM PROJECT FALL SEMESTER 2012 elevator C 11 Enhancements for Eclipse CDT INSTITUTE FOR SOFTWARE Authors Andr Frohlich Christian Mollekopf Advisor H S R Peter Sommerlad HOCHSCHULE FUR TECHNIK RAPPERSWIL FHO Fachhochschule Ostschweiz Task We want to develop two Eclipse Plugins to help developers writing and fixing code ac cording to the C 11 standard The first plugin concentrates on initializers and should detect both uninitialized declara tions as well as non C 11 initializations and allow to easily fix or convert to C 11 initializations For instance would an uninitialized declaration such as int x be marked in the code and a quickfix for the issue would ask the developer for an initial ization value and fix the initialization int x The second plugin should allow to extract lambda expressions into functions or functors to allow for code reuse This includes identifying local variables which need to be passed to the generated function functor identifying if the variables should be passed by reference or by value and asking for a suitable name for the function functor For instance could a lambda expression like this int x int y return x y be transformed into a reusable function like this int add int x int y return x y Or a lambda expression from auto a int x int y return x y struct Addition int operator2. The core functionality is split up in one class for the checker and one for the quickfix 3 2 Implementation Details The plugin was implemented using the CDT plugin framework for quickfixes and uses the Abstract Syntax Tree AST provided by Codan the static code analysis framework Further information about CDT plugin development can be found in 3 2 1 Control Flow The basic cotrol flow goes the following 1 The Checker traverses the AST of reports any problems found using reportProblem 2 CDT places a marker in the editor for every reported problem and allows the user to trigger the quickfix if QuickFix isApplicable returns true 3 If the quickfix gets triggered QuickFix modifyAst get s called which applies the quickfix by replacing the offending statement using ASTRewrite replace Wikipedia Abstract Syntax Tree Wikipedia The Free Encyclopedia wikt eclipse org 14 3 2 2 Checker Since we re primarily interested in declarators the primary entry point for the checker is int visit IASTDeclarator element The function consists of all cases which we explicitly want to avoid and should be skipped and in the end the detection of the initializers which we want to detect and report a problem for According to the problem analysis the following declarations are explicitly ignored e function declarations e parameter declarations e already correctly initialized variables e class memb
3. int x int y return x y 1 A dialog box may prompt for a name similar to the existing Extract Function refactoring Both Plugins should be developed together with suitable documentation and a fully au tomated and installable build Abstract The aim of this project was to develop an Eclipse plug in to help highlighting and fixing initialization issues in respect to the new C 11 brace initializer syntax The C 11 brace initializer provides a uniform syntax for initialization and is preferred in C 11 code over pre C 11 initialization mechanisms such as copy initialization or direct initialization The developed Eclipse plug in detects initialization issues and provides an automated quickfix to make it as easy as possible to fix initialization issues Besides detecting issues the plug in also ensures that no semantic changes are introduced by a quickfix so the resulting code is equivalent The plug in is written in Java using Eclipse CDT s Codan which is a static code anal ysis framework for C providing an abstract syntax tree that we traverse and modify to detect and fix the issues To realize the Eclipse plug in the existing quickfix plug in framework was used to ensure that the plug in integrates well into eclipse and behaves as any other quickfix plug in To enable efficient fixing of larger code bases to C 11 initializations an additional mass refactoring has been implemented This functi
4. Online accessed 13 11 2012 2012 URL eclipse org Tycho Online accessed 13 11 2012 2012 URL ycho N3337 ISO IEC Working Draft Standard for Programming Language C Geneva Switzerland ISO IEC 2012 URL Vogel Lars Eclipse tutorials Online accessed 13 11 2012 2012 URL Tycho tutorial Online accessed 13 11 2012 2012 URL WikiBooks LaTeX Wikibooks Open books for an open world Online accessed 13 11 2012 2012 URL http en wikibooks org wiki LaTeX wiki eclipse org Codan Static Analysis Online accessed 13 11 2012 2012 URL wiki eclipse org CDT designs StaticAnalysis Wikipedia Abstract Syntax Tree Wikipedia The Free Encyclopedia Online accessed 13 11 2012 2012 nL lhttp en wikipedia org wiki Abstract syntax _ tree Redmine Wikipedia The Free Encyclopedia Online accessed 13 11 2012 2012 URL http en wikipedia org w index php title Redminesgoldid 521828609 Visitor Pattern Wikipedia The Free Encyclopedia Online accessed 13 11 2012 m lt D 0 ya W Q D D O K D 39
5. SECIMO ALE 2 String Dark JJ The second example doesn t work because the unordered_map has no constructor which takes a generic list the return type of map list_of and the type must match exactly when using the brace initializer When using the equal initializer on the other hand the type must only be convertible to the target type The conversion would thus break valid code Non initialization boost assign uses can be safely ignored though as we can default initialize the vector as usual vector lt int gt x gt vector lt int gt x x 1 2 repeat 8 5 1 Strategy If boost assign is detected within a declaration the declaration should be skipped 2 1 4 Reference initialization Uninitialized references should be ignored by the plugin as they re illegal anyways and cannot be default initialized Equal Initialized references should be converted to the brace initializer as usual but as there is a bug in the current standard this feature should be configurable and disabled by default Example int x int amp y x gt int amp y x Illegal in current standard but valid in future revision Strategy Ignore uninitialized references Configurable conversion for copy initialized references Note While the used draft of the CH1 1 standard does not support initializing references using the brace initializer syntax the feature is being worked on and future versio
6. e to 1500 30 A 3 User Manual The Elevator plug in for Eclipse CDT gives you the ability to detect and convert unini tialized and initialized varbiables to the new C 11 style brace initialization syntax A 3 1 Installation This manual asumes that you are familar with Eclipse and Eclipse plug in installation To install the Elevator plug in simply add the update site and install the plug in After the installation was succesful you ll find under Code Analysis in the Eclipse preferences window a new problem item called Non or ill initialized variable code Code Analysis Or r F wrest Problems Code Analysis F ena E Coding Style Editor LJ Name convention for function Content Assist Non or ill initialized variable amp Warning Atici LJ Return with parenthesis amp Warning vjava M Potential Programming Problems Code Style Mi Assignment in condition amp Warning Clean Up A Assignment to itself Error A Catrhina hw referanre ic rernmmaenrlarl 2 Warninn Figure A 3 The code analysis preference page A 3 2 Detection 600 C C Calc wc wc cpp Eclipse SDK e py ProjetE X O Le wc cpp X Y amp include lt iostream gt include lt string gt vis Calc Sint main If gt 5 Includes gt allcharc gt averagef gt 2 averagei gt amp calc gt calcstream gt calcstreamTest gt calcTest gt amp charc gt amp
7. API s for the right function to call to get the needed information and not solving generally hard problems or writing a lot of code I learned to appreciate some debugging tools eclipse and java have to offer We also succeeded in using the test driven appraoch much more rigorously than I ever managed before and I think that this really payed off Overall I think I learned quite a lot of things even if not primarily in programming but more in the realm surrounding it 23 A Appendix A 1 Environment A 1 1 Version Management We decided to use Git as our verison control system Although an installation on the provided server sinv 56051 edu hsr ch would be an easy task using Ubuntu s apt get command we used the Git service on git hsr ch In case this services turns out to be unreliable it is possible to migrate to an own Git installation with a minimum of effort elevator Einstellungen Berechtigungen WebHooks Name elevator Typ Git git Kontakt cmolleko hsr ch Url https git hsr ch git elevator Checkout git clone https afroehli git hsr ch git elevator Commits Source Figure A 1 Git Configuration Settings elevator Einstellungen age LU WEDHOOKS Hinzuf gen Entfernen Name a Typ Gruppen Berecht afroehli OWNER E cmolleko OWNER E m1stocke READ E psommerl READ E Figure A 2 Access Configuration We added read only access for our advisors in addition to obvious
8. access rules for us Although we are both familiar with Git and it now belongs to the school curriculum we want to point out that there is an excellent free book written by Scott Chacon available as a reference A 1 2 Build System The buildsystem is based on maven and tycho Chacon 24 Maven Apache Maverl is not really a traditional buildsystem but rather a system to specify the project structure in a way that enables automated builds Unlike traditional Makefiles known from C C development or ANT files which are just scripts executing a bunch of commands maven pom files specify projects modules dependency repositories and various plugins which serve a certain purpose such as executing automated tests That means the specification is much more declarative in constrast to the imperative nature of traditional buildsystems Due to the high level of abstraction it is fairly complex to understand what is happening and how to get started but the resulting system is very powerful The buildsystem we set up installs the complete build environment including all required dependencies runs all automated tests creates an eclipse repository and builds the latex based documentation That means all that is required to build the project on a new system is e Installing Git and Maven e Checking out the git repository of the project e Running maven clean verify latex latex will clean any existing leftovers from
9. ase again although the checker already did that once which means there is some duplication For this reason the ch hsr ifs cdt elevator initializerlist Problems class was meant as a way to bundle the prob lem information so it could be used from both the checker and the quickfix parts Since the duplication is marginal the Problems class wasn t really used in the end though This could be refactored to either use the Problems class properly or remove it entierly 3 4 3 Problems e It is not possible to select multiple variables in the editor and apply the quickfix to those only as this is not supported by the framework 3 4 4 Reverse Quickfix Due to the limited time available it was not possible to implement the reverse quickfix functionality As there exists no prepared solution for Quickassists using CDT this would have to be developed as well and that would have been too much effort within the available time 18 4 Conclusion 4 1 Project Review While the problem we wanted to solve seemed fairly trivial at first we quickly started to discover more and more cases where the default method of simply replacing any existing initializer with the brace initializer does not work This in turn required a deeper analysis of the C code to be able to judge if a quickfix can be safely applied or not Of course as we tried to understand the C code better that opened new problems again i e as you try to understand if t
10. ases using this plugin Extract lambda expressions plug in The extract lambda expression refactoring could be provided as a separate plugin or as part of elevator plugin 4 3 Planning The following figures show the planning as initially estimated after a first revision in week 45 and how it ended up to be at the end of the project start date 17 09 24 09 Y 01 10 08 10 A 15 10 22 10 29 10 05 11 12 11 19 11 26 11 03 12 10 12 17 12 rr O O O O O O O O O O O IS IR mE E Figure 4 1 Initial Planning Project kick off Documentation Initializerlist Plugin Lambda Refactoring Plugin Finish Infrastructure Buildserver Bugtracker Buildsystem Initializerlist Plugin Buildsystem Lambda Refactoring Plugin Initialization List Checker Requirements Design amp Specification Prototype Final Implementation Testing Refactoring Lambda Refactoring Requirements Design amp Specification Prototype Implementation Testing Refactoring Delivery Presentation Week 38 39 40 41 42 43 44 45 46 47 48 49 50 51 start date 17 09 24 09 01 10 08 10 5 15 10 5 22 10 29 10 05 11 12 11 819 11 26 11 03 128 10 12 817 12 Project kick off a a A A ee ee A eee Documentation Initializerlist Plugin al jimi E Lambda Refactoring Plugin ES PA Finish Infrastructure Buildserver Bugtracker Buildsystem Initializerlist Plugin Buildsystem Lambda Refactoring Plugi Initializat
11. be applied to generate a replace ment statement TASTNode newStatement resolveConstructorInitializer ast getASTNodeFactory targetStatement While generating the replacement statement it is important to copy as much as possible from the original statement to avoid changing any unnecessary aspects of the original statement This is generally achieved by copying the full declarator and then replacing the initializer only Finally the function applies the quickfix and modifies the AST using ASTRewrite r ASTRewrite create ast r replace targetStatement newStatement null Change c r rewriteAST c perform new NullProgressMonitor This results in the code being effectively modified in the editor 3 2 4 Mass conversion The mass conversion features triggers all the markers found This works similar to the CheckTestCase class which also has to invoke the quickfixes from markers in an editor First the markers as well as an instance of the quickfix are required IMarker markers projectResource findMarkers IProblemReporter GENERIC_CODE_ANALYSIS_MARKER_TYPE true 2 AbstractCodanCMarkerResolution quickFix new QuickFix 16 It is now possible to iterate over the array of markers and invoking the quickfix for each marker for IMarker marker markers quickFix run marker The difference between doing a mass refactoring for the current editor and the current project is the re
12. d by eclipse afterwards that functionality is hardly useful A 1 3 Project Management For collaboration we decided to use Redmine Redmine is a free and open source web based project management and bug tracking tool The installation process was fairly simple Using the apt get command we installed the redmine as well as the apache and the libapache2 mod passenger packages The later is an apache module for supporting Ruby on Rails on which Redmine is built sudo apt get install redmine libapache2 mod passenger sudo ln s usr share redmine public var www redmine sudo nano w etc apache2 mods available passenger conf PassengerDefaultUser www data sudo nano w etc apache2 sites available default lt Directory var www redmine gt RailsBaseURI redmine PassengerResolveSymlinksInDocumentRoot on lt Directory gt sudo service apache2 restart A 1 4 Continuous Integration For continuous integration we decided to use Jenkins a popular and extendible server Jenkins only needs a Java Servlet container to run on For our project we set up two jobs One for building the plug in and the second for building the documentation Both jobs are configured to grep the source code from our git repository and build it with maven The jobs are triggered to be run once an hour if a change in the repository was made Wikipedia Redmine Wikipedia The Free Encyclopedia 26 With maven it was possible to build as w
13. danMarkerResolution Defines a resolution for a problem Quickfix e org eclipse cdt codan ui codanProblemDetails Allows to supply additional informa tion about the found problem e org eclipse core resources markers Allows to define custom markers Further information on eclipse plugin development can be found in the tutorials herd WikiBooks LaTeX Wikibooks Open books for an open world Vogel 27 A 2 2 AST The following is a list of the most important AST nodes e ASTDeclarator A Declarator node a single variable with a type and initializer e ASTInitializer An initializer node e IASTExpression Contains type information e ICPPConstructor A constructor with arguments e ICPPClassType Allows to retrieve constructors of a type including implicit con structors e IType Represents a type which can be either a builtin type or also a custom type e IASTName Represents a name in the program such as a variable name e IBinding The binding represents the semantics of a name It can i e be used to get the fully expanded type of a name which uses typedefs for the type specification While there are many more these are the most important ones used throughout the code so it is vital to understand all of them Most of them have several specialized subclasses so 1t is always a good idea to have a look at the type hierarchy should a new class appear while writing debugging code A 2 3 Abstrac
14. ded into an eclipse in stance and runs all the tests For checker test cases there is the org eclipse cdt codan core test CheckerTest Ca interface for Quickfix Tests there exists no official equivalent though Therefore the Quick FixTestCase class was copied from the internal API of codan The InitializerCheckerTest contains all tests for the checker part while the Initializ erQuickfixTest contains the tests for the quckfix Both require all tests to be prefixed with test and execute all tests in a random order Checker Tests Checker Tests allow the specification of a codefragment in a comment above the testfunction which is then loaded into the editor when the test is executed One can then assert in which line an error should be detected An example test looks like this Jf elass Tj L TR public void testFindUninitializedType loadCodeAndRunCpp getAboveComment checkErrorLine 2 This test ensures that an error is detected on the second line of the comment upon T x which is an uninitialized variable Similarly it is possible to check that no error has occured FE ant TOO public void testIgnoreFunctionDecl loadCodeAndRunCpp getAboveComment checkNoErrorsOfKind elevator initializer list By using checkNoErrorsOfKind elevator initializerlist instead of checkNoErrors One can circumvent problems due to some built in plugins reporting code issues such as an error being
15. e constructor call to the initializer list syntax without introducing potential ambiguity Example vector lt int gt 4 2 gt Vector lt int gt amp 12 2 25255 MOE Vector lt int gt Xx 14 27 Strategy If the constructor call contains arguments and the type contains an initializer list constructor the call must not be converted to the braced init list 2 1 2 Use of implicit type conversion when using direct or copy initialization Direct initialization using the Constructor initializer and copy initialization allow the use implicit type conversion but the direct initialization using the brace initializer does not Therefore conversions of an initialization which relies on implicit type conversion must not be carried out automatically The user may decide to use explicitconversion but this is not safe to do automatically Example Je ff EA ne A32 PAR ALA ON SO AL Sine NS Strategy Only convert automatically if types are matching exactly and no implicit conversion is happening This can be checked by looking for an appropriate constructor in the target type 2 1 3 boost assign Initializations using boost assign have to be skipped as we cannot convert them Example 10 works boost unordered_map lt int std string gt map boost assign map_list_of L1 Serimg Ane 4 Seringt Derk doesn t work boost unordered_map lt int std string gt map boost assign map_list_of la
16. e than just building and even goes some steps to direct publishing right from the same tool All in all a refreshing new take at buildsystems It was also nice to finally get to know jenkins a little closer which does indeed a nice job as an automated buildsystem I personally didn t use it a lot as I anways run all the tests locally regularly and with a two man team the gain isn t really there Latex provided about what I expected a steep learning curve until we had figured out all the necessary quirks but it was a breeze working with it afterwards Especially due to the excellent interoperability with git because of the plaintext files Also the produced documentation really does looks fantastic compared to any word document or alike I wasn t overly impressed by the eclipse framework I m sure there are reasons why it is what it is but I just don t like how eclipse seems to try to develop everything there is to an IDE in one gigantic framework instead of using existing or creating new self contained reusable libraries At least that was my first impression The parts we ve been working with worked well enough but didn t really give the feeling of an overall concept and a good design but rather as if they were just hacked together to get some job done That feeling was probably also fueled by a lack of documentation and thus also understanding Since a large part of the work consisted of searching through
17. ee 13 2 2 4 Mass Refactoringl 22 2 Cm mon nen 13 2 2 5 Reverse Refactoring ooo 13 14 TAREA 14 PRETENDEN E 14 arado sara 14 3 22 becker os Soe 5 vu 0 0 DR SHO eee Oe Soe AA 15 TEMER 15 AE 16 Dro ET esa RRA eek beh ee ee AAA 17 aras eee meee eee eee ee 17 34T Checks bs ba wee 2S OOO ORS eRe Eee as 18 AAA As sa 18 DO Pr blemsl 2 5 scenes aaa 18 TEN EEE ea eeeeee ease 18 19 TIENE 19 AD os AREA E 19 dos EMM e oe Hoe casaron do AAA AAA 20 rasos odos 21 4 4 Andr Frohlich 000 000 0000 00000008 22 4 5 Christian Mollekopfl e 23 A Appendix 24 Cee ee eee Bee ae ee ee ene eee Pee eae ee 24 ee eee ee ee ee ee 24 Pe oat dh ead eRe 24 TE 26 boheme Gout nnseeupee arn 26 aaa ree 27 eras E ee ee er ee eee ee eee 27 eGo wh sob aa aa 27 Era aaa aora 28 TERA 28 a es 28 FEET 29 A 3 User Manuall u au ua 0 oe se bbe ee we baw Se ra ee EEE HR OO 31 EI 31 A 31 A 3 3 Conversion 2 m moon 32 A 3 4 Mass Conversion 2 2 oo on 33 B Glossary 34 1 Introduction Everyone who writes C code occasionaly forgets to initialize variables The code com piles and often the programm seems to work as expected Unfortunatly this is error prone and can lead to undefined behaviour With the introduction of the C 11 standard there is a new simple and consistent way to initialize variables using curly braces It would be convient if the integrated development enviroment could
18. ell as test the plug in using Jenkins To get the source from the git repository we used the Git Jenkins plug in Because the tests require an X server for running Eclipse the Xvfb was also used To build the documentation with KIEX no special Jenkins plug in was needed as we used maven to build the documentation A 1 5 Documentation The documentation was written using RIEX It is recommended to use the texlive ATRX distribution which was used in the version 2012 The following wikibooK contains a lot of helpful tipps for working with latex A 2 Eclipse Framework To implement the C refactoring plugin Codan the static analysis framework of CDT has been used For providing Quickfixes two major parts are required First detecting problems and setting an according marker with a provided quickfix option and second applying the actual quickfix A 2 1 CDT Plugin interface A CDT plugin has the following required parts e plugin xml Describes and defines the used extension points e Activator implementing the AbstractUIPlugin interface Defines a PLUGIN_ID The Activator is referenced in the MANIFEST MF as Bundle Activator and controls the plugin lifecycle Used Extension Points as defined in plugin xml e org eclipse cdt codan core checkers Defines a checker which can be used to detect problems and place a marker The extension point is also used to define specific problems e org eclipse cdt codan ui co
19. erefore requires a lot of time in order to find your way That is also the reason why the project has not progressed as quickly as I desired Many problems that I thought they were difficult to solve were actually quite simple On the other hand the framework complicated problems We often had to search on the internet to solve a particular problem or find out how something works We also had to read the source to understand how to use the API Altough it was interesting to explore the framework so it cost us too much time I would have preferred to implement more features instead Either way it was a very good experience and preparation for the bachelor thesis and I enjoyed working with Christian 22 4 5 Christian Mollekopf Having worked most of my professional private and academic life with C C and even from that part a large part was spent with the Qt Framework and tools like git and cmake this project took me out of my comfort zone to face some new technologies This was my second real Java based project and the first time I worked with maven the eclipse framework jenkins and latex Maven proved to be somewhat of an entry barrier mostly due to the lack of documentation how to build eclipse plugins using it I appreciate the declarative aspect of the pom xml files though and find it an interesting approach compared to the traditional Makefiles Ant scripts Another interesting aspect is that maven wants to provide mor
20. ers e types with initializer list constructors e initializations using boost assign e initializations using implicit type conversions Constructor init lists aren t part of a declarator and are therefore individually handled in int visit IASTInitializer initializer Detected problems for which a quickfix should be provided are reported using the reportProblem function which takes the following arguments e String id The problem id which is used in the plugin xml to connect the quickfix to the problem e IASTNode node The node where the problem was found which is used for the marker position e Object args Arguments which can be used to transport further information to the quickfix 3 2 3 Quickfix Before the quickfix is executed the framework checks if the quickfix is applicable to the problem using bool isApplicable IMarker marker 15 This function should return true if the quickfix is applicable to the problem or false if not The following function is called if a quickfix is executed void modifyAST IIndex index IMarker marker The index is used to retrieve the AST and the marker contains the position where a problem was detected Since the marker only contains the absolute position in the file the target statement first needs to be retreived from the AST TASTNode targetStatement getEnclosingDeclarator astName Once the traget statement is identified the quickfix can
21. fracttab gt amp lc getline Ic newline gt 3 multab gt amp sumf gt amp sumi gt j gt wc unsigned count std string s while std cin gt gt s count std cout lt lt count lt lt words n E Console 3 No consoles to display at this time Writable Smart Insert Figure A 4 An open file with detected issues The plug in automaticaly detects initialization issues and marks them in the editor l A 3 3 Conversion by ProjectE X lt 10stream gt 5 e a pr aoe vin Calc Sint maint gt Includes amp unsigned count gt allcharc E std stri 4 Replace with C listo gt gt averagef o while std 5 Rename in file gt gt averagei std cout Rename in workspace CBR gt amp calc az gt amp calcstream gt gt calcstreamTest gt amp calcTest gt amp charc gt amp fracttab gt amp Ic getline gt amp Ic newline gt amp multab da E Console 3 o ne gt we No consoles to display at this time Non or i tialized Writable Smart Insert Figure A 5 Invoking a quickfix To convert a detected issue you can click on the icon on the side and chose the provided quickfix to convert the issue Projecte X 7 o Vv amp include lt iostream gt include lt string gt Vie Calc Sint mainO gt Includes o unsigned count gt allcharc std string s gt averagef w
22. g gt at v Calc Sint main gt K Includes unsigned count gt allcharc std string s gt gt averagef while std cin gt gt s count gt gt averagei std cout lt lt count lt lt words n gt amp calc gt calcstream gt calcstreamTest gt calcTest gt charc gt fracttab gt gt Ic getline gt Ic newline gt E multab d pe E Console 3 gt Gwe No consoles to display at this time Writable Smart Insert AR Figure A 8 All initialization issues are gone To convert all issues of the current project choose Convert Project from the Elevator menu 33 B Glossary Declaration A specification how a name should be interpreted int f int x A single variable function or type within a declaration int x conversion with precision loss int x 3 2 j x 3 Conversion constructor Constructor taking single argument of source type allowing a non narrowing conversion Abstract Syntax Tre o ooo Table B 1 C Not Initialized int x List initialization Initialization from a braced init list 13 4 35 Constructor init list C a 1 b 2 c3 Table B 2 Initializations 34 Bibliography Apache Foundation Apache Maven Online accessed 13 11 2012 2012 URL g Chacon Scott Pro Git 1st Berkely CA USA Apress 2009 ISBN 978 1430218333 URL t EPp git sen com book codehaus org Latex Maven Mojo
23. gtracker e g what there is to do Overall the project was managed fairly efficiently and we learned some points where we can improve in future projects The resulting plugin should do it s job well and since it was developed with care that no valid code is broken it should also not get in the way of the developer which is of course very important for a plugin that aims to support The plugin may still have some rough spots which would need to be ironed out simply because it didn t receive any real world testing so far and will first need to prove itself by being used productively Unfortunately we didn t manage to implement all the features we planned for originally such the reverse refactoring and the extract lambda plugin 4 2 Outlook Further development could tackle the following problems 19 Reverse refactoring To get C 11 code to compile with a non C 11 compiler it would be desirable to have a reverse refactoring which transforms C 11 initializations to non C 11 initializations This refactoring should be applicable to single statements as reverse operation of the quickfix but also as mass refactoring to fix larger code bases Support for further C 11 features The plugin could provide support for more C 11 features which are not limited to the new initializerlist syntax The aim should be to help developers leveraging the new features of C 11 and to make it easier to modernize existing code b
24. hile std cin gt gt s count gt gt averagei std cout lt lt count lt lt words n gt amp calc gt gt calcstream gt amp calcstreamTest gt amp calcTest gt amp charc gt fracttab gt amp Ic getline gt Ic newline gt amp multab gt amp sumf gt amp sumi E Console X spen gt we No consoles to display at this time Figure A 6 The file after the conversion of the first issue 32 A 3 4 Mass Conversion It is possible to convert all issues at once To accomplish this simply choose Convert from the Elevator menu Eclipse File Edit Source Refactor Navic ate Search Project 43 10 Run Window Help C C Calc wc wc cpp Eclipse SDK Convert Project Le we cpp Y include lt iostream gt m include lt string gt rc v 15 Calc Sint mainO gt i Includes amp unsigned count gt allcharc E std string s gt gt averagef while std cin gt gt s count gt gt averagei std cout lt lt count lt lt words n gt 3 calc gt amp calcstream gt calcstreamTest gt amp calcTest E charc gt fracttab gt amp Ic getline gt Ic newline gt amp multab d pea E Console 3 gt we No consoles to display at this time Writable Smart Insert 4 7 a Figure A 7 Convert all issues of the current editor Project E 23 A we cpp 3 include lt iostream gt m include lt strin
25. ion List Checker no gt 1 x y gt x y int x a gt a o E f i Exceptions NSDMI Reverse Refactoring Refactoring Cleanup Lambda Refactoring Delivery Presentation Figure 4 2 First Iteration 20 Project kick off Documentation Initializerlist Plugin Lambda Refactoring Plugin Finish Infrastructure Buildserver Bugtracker Buildsystem Initializerlist Plugin Buildsystem Lambda Refactoring Plugin Initialization List Checker no gt x y gt xy int x a gt a Exceptions NSDMI Implicit type conversion Mass refactoring Reverse Refactoring Refactoring Cleanup Lambda Refactoring Delivery Presentation Figure 4 3 Final Planning The planning changed quite a bit over time as we found new requirements or removed planned features and had to be adjusted accordingly 4 3 1 Spent Time HoursMWeek Christian Mollek opf 4 Andr Fr hlich 0 19 09 2309 2778 01 10 05 10 08 10 13 10 17 10 21 1100 25 10 29 10 02 11 06 11 10 11 14 11 18 11 22 11 26 11 30 11 04 12 08 12 12 12 16 12 20 12 24 12 17 09 2109 25098 29 08 03 10 07 10 11 10 15 10 19 10 23 10 27 10 31 10 04 11 08 11 12 11 16 11 20 11 24 11 28 11 02 12 08 12 10 12 14 12 18 12 22 12 ma Figure 4 4 Spent Time The time we spent on the project fluctuated a bit around the 17 5h per week which was the expected effort The initial peak was during the setup of the buildsystem which caused some trouble followed by a
26. large drop caused by private responisbilities and followed by illness The curves stabilized afterwards until the end of the project where we had to give another boost to finish the documentation The curves look very similar since we usually worked together on Monday and Tuesday 21 4 4 Andr Frohlich Since I had not much experience with C I wanted to do this project I was also a good way to refresh my knowledge from the C module Programmieren 3 It was also important to me to work on something that seemed to be useful in the end My professional background was to be a web developer so many things were new to me at least the application of them in such a big project I had a little experience with latex and git and I was able to learn much using these tools so extensive during the project I never used a continuous integration server but it was pretty easy However as we were only two this would not have been necessary Redmine as a project management tool was not bad but in hindsight I would have pre ferred something simpler and more agile Maybe a little more like Github The time tracking and project planning was pretty time consuming with Redmine Although I am convinced my Java programming experience is nod bad I still had some respect for the Eclipse framework At the same time it was a joy to be able to learn something new However the framework was also a little tedious It s incredibly large and th
27. mplementation can sometimes be a bit of a drag as much of the work consists of figuring out how to find a particular statement in the AST which basically is a huge type hierarchy so one usually has to cast the way through all the interfaces to finally get the statement one is looking for Also since there exists such a mass of types in the tree it is 17 often very difficult to figure out which statement actually conveys the information one is looking for Therefore a lot of work has to be done using a testcase and the debugger to get what one wants using lots of internal api and usually overly complex processes which can then be cleaned up in a second round 3 4 1 Checker While the code should be fairly easy to understand and extend it is also very easy to break one of the special cases as they are all implemented in the same function as conditional return s all cases affect each other directly The test driven development approach is therefore essential with all basic cases covered by the testcases Most parts are implemented cleanly but the following implementations should be re vised e Checker getTargetTypeConstructors Uses internal API due to an exception being thrown when using the interface e Checker hasInitializerListConstructor Relies on string comparison to detect the ini tializer_list type which i e doesn t work with typedefs 3 4 2 Quickfix The quickfix implementation has to detect the problem c
28. ns of the standard should support this 1N3337 Working Draft Standard for Programming Language C 11 2 1 5 Declaration Lists Multiple uninitialized declarations should be handled properly Example int x y 3 z 4 gt int x y 3 z 4 Strategy Iterate over declarations and handle each individually 2 1 6 Function declarations Function declarations have the same syntax as a constructor call but must be ignored Example int x Strategy Ignore function declarations 2 1 7 Pointers Pointers should be default initialized just as any other variable resulting in a nullptr Example int x gt int xx Strategy Initialize as usual 2 1 8 Member variables Member variables should be ignored as this can lead to a change of semantics and the initialization is covered upon instantiation Example struct A int x y Strategy Ignore member variables 12 2 1 9 Constructor init list Constructor init lists should be converted to C gt 11 initialization as well Example td he Re la ad Dei Strategy Initialize as usual 2 2 Features The plugin is implemented as a Marker with a Quickfix to correct the problem Addition ally a refactoring will be provided to enable mass conversion 2 2 1 Marker The plugin should detect missing invalid and non C 11 initializations and set a marker accordingly This marker is then visible in the edit
29. onality can be triggered from the usual refactoring menus to fix either complete source files or even full projects Management Summary This chapter shows you the goals of the Elevator project gives you an overview how the Elevator plug in can help you converting existing C source code to the new C 11 syntax and ends with a look at what can be improved even more Prior to C 11 there was no uniform way to initialize variables In addition uninitialized variables are a common issue C 11 introduced with brace initialization a uniform way to initialize variables Take a look at this simple example Notice that the last variable is not initialized The other variables show common ways to initialize variables In C 11 we can uses braces for initialization This new syntax can also be used like an initalizer list to initialize sequences of values It also prevents narrowing issues During the project we have developed an Eclipse CDT plug in that helps to convert C source code to the new C 11 syntax After installating the plug in it highlights any occurrence of a variable initialization not using the new brace syntax To resolve a issue a developer can select it and use the provided Eclipse quickfix to resolve it In addition it is possible to convert all occurrences in the active editor or even in the project To achieve this the plug in uses the static code analysis frame of Eclipse CDT It can parse and alter the abstract
30. or window and helps the developer to spot initialization errors and allows to trigger a matching quickfix 2 2 2 Quickfix The quickfix should allow for automatic correction of the detected problems It can be invoked as usual in Eclipse by clicking on the marker or using the quickfix shortcut The quickfix should honor the current text selection so if i e only a single variable is marked within a declaration list only that one should be refactored 2 2 3 Reverse Quickfix To revert the quickfix operation a Quick Assist should be provided to revert the operation The reverse operation should not be implemented as quickfix as this would result in always a problem being detected either the quickfix or the reverse quickfix 2 2 4 Mass Refactoring The mass refactoring allows to automatically fix all initialization problems in a file or project to allow efficiently fixing larger codebases 2 2 5 Reverse Refactoring The reverse refactoring allows to convert either individual or batch convert all C 11 initializations to non C 11 initializations 13 3 Implementation 3 1 Logical Structure To implement the desired functionality we use the project structure as described in the appendix It consists of several Eclipse Maven projects e One eclipse project contains the core functionality e One eclipse project contains the unit tests e An eclipse parent project to reference the other two projects
31. pre vious builds build both the Eclipse plug in and the documentation including down loading all required dependencies and run all the unit tests of the project This ensures the project can be built on any machine with a minimum of effort and that a the builds are fully reproducible Tycho Tychd is a maven plug in providing integration for Eclipse plug in projects It extracts information from the existing eclipse spec files i e plugin xml and provides that meta information to maven so no duplication is required although two differen buildsys tems are used Further information on setting up tycho can be found herd To execute unittests the tycho surefire plugin was used Documentation Since the documentation is written in latex it is built as well using maven To build the documentation the maven latex plugin from www codehaus org was used The documentation can be built using the maven latex latex target Apache Foundation Apache Maven 3 eclipse org Vogel Tycho tutorial codehls OF 20 Eclipse integration While the maven eclipse integration works well based on the tycho plugin the other way is barely existing While there are maven integration plugins eclipse doesn t really internally use maven to build the project but uses it s own build tools anyways All the maven integration tools do is allowing to schedule a maven build from eclipse but since the result isn t use
32. provide some assis tance for such cases In the Eclipse CDT there are already markers avaible for various kinds of hints and some even provide quickfixes as needed The idea is to develop a new Eclipse CDT plugin which provides a marker for the intro duced problem as well as a quickfix which allows to fix the problem automatically The plug in should for example detect and mark the following uninitialized variable An invocation of the corresponding quickfix would then result in the variable being default initialized Similarly non C 11 code should be refactored to use the C 11 initializer syntax would result in int 1 1 int yil 2 Analysis The following relevant cases of initialization exist 6 Braced init list initialization Tx 3 Table 2 1 Initializations The default strategy for conversion looks the follwing Detected POD default initialization Bul Default initialization ESTE 5 Copy initialization 6 Reverse default initialization 5 T x 2 Reverse direct initialization 6 T x 3 Table 2 2 Default Conversions 3 TO 6 Example T xy APA ayy T RS Ders EX Ll S H 7 RAS 235 T X TUN 7 2 R Sy Zune 2 1 Special Cases The following section lines out the existing special cases where the default strategy does not apply 2 1 1 Container using an initializer list constructor If a type has an initializer list constructor we cannot convert th
33. reported regarding a declared but never defined function foo here Quickfix Tests The Quickfix test also loads a codefragment from the comment above the testfunction and then runs the Quickfix on that codefragment The assert checks if the expected transformation is present in the result string An example test looks like this If Class IT ae 3G public void testUninitializedClass throws Exception loadcode getAboveComment String result runQuickFixOneFile 29 assertContainedin 7 x 4 result This test ensures that the result contains the string T x Running the Tests The tests should be executed as JUnit Plug in Test using JUnit4 It is possible to either execute the whole testproject but also individual test classes or even individual test functions Problems e It is not always guaranteed that a unittest behaves exactly the same as if an eclipse instance was started and a certain feature tested manually This is because some parts are not covered by the unittests such as the isApplicable function of the Quickfix e Note that the Quickfix tests depend on the formatting setting in eclipse as it is a simple string comparison including whitespace e The Quickfix test depends on a startup delay to ensure the plugin is loaded De pending on the hostcomputer this delay can be too small resulting in failing tests The delay can be adjusted in QuickFixTestCase runQuickFixOneFile i
34. source we need to obtain the markers from The current editor is accessible with the getActivePage Method from the current work bench window The editor also provides a way to get the project IWorkbench workbench PlatformUl getWorkbench IWorkbenchWindow workbenchWindow workbench getActiveWorkbenchWindow IWorkbenchPage workbenchPage workbenchWindow getActivePage IEditorPart editor workbenchPage getActiveEditor IEditorInput editorInput editor getEditorlInput IResource editorResource ResourceUtil getResource editorInput IResource projectResource editorResource getProject All dirty editors have to be saved editor doSave null PlatformUl getWorkbench saveAllEditors false 3 3 Unit Tests There are two test cases The first simply tests for placed markers to investigate the behavior of the Checker java class The other one focuses on testing all functionalty covered by the Quickfix java class Care has been taken that each testcase only tests a single requirement and that the tests are a simple as possible The checker testcases cover all default conversions as well as well as all exceptions which are explicitly ignored as listed in Further tests have been added for likely false positives Full path coverage is not targeted there are as few tests as possible and as many as necessary More information about the unit test framework can be found in 3 4 Review The i
35. syntax tree und find issues and convert them struct Rect A Rect int w int h zu wC wy gt Ar Replace with C 11 Initializerlist H Rename in file bp Rename in workspace R int w int h 3 woid foot Fa Rect r1 4 2 Zi Rect r2 rl Smart Insert The Elevator Eclipse CDT plug in in action Even the plug in is useful to convert legacy code it would be nice to be able to convert the code back to not use the new brace syntax This could be useful when one wants to use new code in a project where the new C 11 syntax is not permitted Unfortunately we had not enough time to implement this feature It would also be conceivable to support more C 11 features Contents 1 Introduction 8 2 Analysis 9 21 Special Cabes s ss opos aes OS eae oA EAS eae Ba eS Se ee 10 2 1 1 Container using an initializer list constructor 10 21 9 OOOStOSsICUl ss s es oe eA ar eee eee wee eS 10 edu E eh EE 11 2 1 5 Declaration Lists 0 0 000 0 0 0 0 00008 12 2 1 6 Function declarations m m nn 12 21 7 Ponte sass meee hee Eee ER ESRB EN EH REGRESS EE 12 2 1 8 Member variables 2 2 2 Ho mn nn nn 12 2 1 9 Constructor init ist nn 13 Doe EEE E 13 2 2 Mke sss 2 32 00 u 8 2 20 8 ee RE GSS EE ER SSeS EE HEE 13 Dee eee eee eee eee ee ee ee ee IR eee eee eet 13 Dees ee eee ee ae ene eee ee eee e
36. tindexAstChecker The org eclipse cdt codan core cxx model AbstractIndexAstChecker is a visitor which tra verses the Abstract Syntax Tree AST everytime CDT s parser detects a modfication The tree is traversed top down node by node using the processAst member function The return value of processAST allows the implementation to decide if it wants to go any deeper in the tree or stop at the current node Using the reportProblem function found problems can be reported using the problem ID as specified in plugin xml which results in a marker being placed in the editor A 2 4 AbstractAstRewriteQuickfix The org eclipse cdt codan ui Abstract AstRewriteQuickF ix interface requires essentially two functions to be implemented for a quickfix e isApplicable gets a marker as argument and should return true if the quickfix is applicable to the reported problem e modifyAST receives a marker and the current project index to apply the actual quickfix by modifying the AST Since problems are reported per declarator the quickfix also only operates on single declarators and not complete declarations This ensures that i e variables in declaration lists are processed individually Wikipedia Visitor Pattern Wikipedia The Free Encyclopedia 28 A 2 5 Testing The unittests are in a separate project to avoid dependencies from the plugin to test libraries The test is implemented as a separate plugin which is loa
37. wo types are compatible you have to start inspecting the constructors of the target type you have to deal with reference types you have to deal with builtin types which might or might not have a non narrowing conversion you have to deal with template types which you first have to fully expand due to the use of using namespace and namespace X Y and so on So in that respect the problem became a lot complexer than we expected initially but at the same time also more interesting of course From a project management side the project went fairly smooth The regular meetings forced us to concentrate on individual tasks which we could accomplish which in turn ensured we could put all our effort in accomplishing those tasks and not in finding out what there is to do We could have used the bugtracker more rigorously which would have improved the visibility of the current project status Also it wasn t ideal how we initially setup the bugtracker with the traget versions misused as timeboxed milestones and with a strong focus on the gantt chart which resulted in duplicating bugs just for the sake of having it under every target milestone in the gantt chart That is of course not helpful for establishing the current state of the project and results in a lot of effort for maintaining the bugtracker Once we settled for using just tickets with sub tickets that effort was reduced a lot and helped us to get meaningful information from the bu
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