tl;dr<\/h3>\n\n\n\n
Clang Rocks!!!<\/p>\n\n\n\n
You can find the plugin here<\/a>.<\/p>\n\n\n\n While working on BloodMagic<\/a>, I realised that it’d be nice to have a tool for checking semantic errors related to BM usage. For example: in the interface property marked as I concluded that I need to work with and I need a full-featured parser.<\/p>\n\n\n\n I’ve tried different approaches: flex<\/a>+bison<\/a>, libclang<\/a>, but ultimately I decided to write a Clang plugin.<\/p>\n\n\n\n Just for testing purposes I’ve started a simple plugin with the following goals:<\/p>\n\n\n\n Features of the test plugin:<\/p>\n\n\n\n For plugin development we need llvm\/clang, built from source<\/p>\n\n\n\n Current Create directory for plugin<\/p>\n\n\n\n Our plugin based on example from Clang repo and here is it’s structure:<\/p>\n\n\n\n We’ll use one source file for simplification<\/p>\n\n\n\n Now we’re able to generate Xcode-project, based on Run Clang AST module provides RecursiveASTVisitor<\/a>, which allows us to traverse via AST. Let’s create test source file and check how plugin works.<\/p>\n\n\n\n Rebuild plugin and run<\/p>\n\n\n\n We’ll see a huge list of classes.<\/p>\n\n\n\n Let’s report warning in case if class’ name starts with lowercase letter<\/p>\n\n\n\n Add Add check<\/p>\n\n\n\n Add some class with “bad” name<\/p>\n\n\n\n rebuild and run<\/p>\n\n\n\n Let’s generate error in case of class’ name contains Output after running<\/p>\n\n\n\n Uncomment first check Unfortunately, system (under ‘system’ I mean Xcode’s clang) clang doesn’t support plugins, so we need to hack Xcode a bit, to allow using of custom compiler.<\/p>\n\n\n\n Unzip this<\/a> archive and run following commands:<\/p>\n\n\n\n This will enable custom compiler for Xcode.<\/p>\n\n\n\n Reopen Xcode and you’ll see new compiler:<\/p>\n\n\n\n Create new project and select newly added custom clang in To enable plugin add following parameters to the Note, that we use Also, you should disable modules for this target\/build<\/p>\n\n\n\n Add After build you’ll see error and warnings in a more familiar form<\/p>\n\n\n\n It’s time to add Rebuild plugin and try to build test project<\/p>\n\n\n\n As you can see, creating a clang plugin is relatively simple, but it needs some dirty hacks with Xcode, and you should use custom built clang, so I’d not recommend you to use this clang for building apps for production usage. Apple provides patched version, and we can’t know the difference between them. Also, it needs a lot of efforts to make it work, which doesn’t make it widely usable. You still can use it on your system for different diagnostic purposes, but please do not force other people to depend on such heavyweight things.<\/p>\n\n\n\n If you have any comments, questions or suggestions feel free to ask me on twitter<\/a>, open issue on GitHub<\/a>, or just leave a comment here.<\/p>\n\n\n\n Happy hacking!<\/p>\n","protected":false},"excerpt":{"rendered":" This tutorial describes how to create Clang plugin and covers the next things: environment setupbasic plugin setupsetup Xcode project for plugin developmentwarnings reportingerrors reportingXcode integrationinteractive hints for errors\/warnings riddance tl;dr Clang Rocks!!! You can find the plugin here. Intro While working on BloodMagic, I realised that it’d be nice to have a tool for checking…<\/p>\n","protected":false},"author":55,"featured_media":9446,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"_acf_changed":false,"footnotes":""},"categories":[3],"tags":[],"coauthors":["AlexDenisov"],"class_list":["post-6549","post","type-post","status-publish","format-standard","has-post-thumbnail","hentry","category-development"],"acf":[],"aioseo_notices":[],"categories_data":[{"name":"Engineering","link":"https:\/\/railsware.com\/blog?category=development"}],"post_thumbnails":"\/\/railsware.com\/blog\/wp-content\/uploads\/2014\/02\/custom_compiler.png","amp_enabled":true,"_links":{"self":[{"href":"https:\/\/railsware.com\/blog\/wp-json\/wp\/v2\/posts\/6549","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/railsware.com\/blog\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/railsware.com\/blog\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/railsware.com\/blog\/wp-json\/wp\/v2\/users\/55"}],"replies":[{"embeddable":true,"href":"https:\/\/railsware.com\/blog\/wp-json\/wp\/v2\/comments?post=6549"}],"version-history":[{"count":25,"href":"https:\/\/railsware.com\/blog\/wp-json\/wp\/v2\/posts\/6549\/revisions"}],"predecessor-version":[{"id":13962,"href":"https:\/\/railsware.com\/blog\/wp-json\/wp\/v2\/posts\/6549\/revisions\/13962"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/railsware.com\/blog\/wp-json\/wp\/v2\/media\/9446"}],"wp:attachment":[{"href":"https:\/\/railsware.com\/blog\/wp-json\/wp\/v2\/media?parent=6549"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/railsware.com\/blog\/wp-json\/wp\/v2\/categories?post=6549"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/railsware.com\/blog\/wp-json\/wp\/v2\/tags?post=6549"},{"taxonomy":"author","embeddable":true,"href":"https:\/\/railsware.com\/blog\/wp-json\/wp\/v2\/coauthors?post=6549"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}Intro<\/h3>\n\n\n\n
lazy<\/code>, but not defined as @dynamic<\/code> in the implementation, or property marked as lazy<\/code>, but class container doesn’t support injections.<\/p>\n\n\n\n_<\/code><\/li>Environment setup<\/h4>\n\n\n\n
cd \/opt\nsudo mkdir llvm\nsudo chown `whoami` llvm\ncd llvm\nexport LLVM_HOME=`pwd`<\/pre>\n\n\n\n
clang<\/code> version on my system – 3.3.1, so let’s build respective version:<\/p>\n\n\n\ngit clone -b release_33 https:\/\/github.com\/llvm-mirror\/llvm.git llvm\ngit clone -b release_33 https:\/\/github.com\/llvm-mirror\/clang.git llvm\/tools\/clang\ngit clone -b release_33 https:\/\/github.com\/llvm-mirror\/clang-tools-extra.git llvm\/tools\/clang\/tools\/extra\ngit clone -b release_33 https:\/\/github.com\/llvm-mirror\/compiler-rt.git llvm\/projects\/compiler-rt\n \nmkdir llvm_build\ncd llvm_build\ncmake ..\/llvm -DCMAKE_BUILD_TYPE:STRING=Release\nmake -j`sysctl -n hw.logicalcpu`<\/pre>\n\n\n\n
Basic plugin setup<\/h4>\n\n\n\n
cd $LLVM_HOME\nmkdir toy_clang_plugin; cd toy_clang_plugin<\/pre>\n\n\n\n
ToyClangPlugin.exports\nCMakeLists.txt\nToyClangPlugin.cpp<\/pre>\n\n\n\n
#include \"clang\/Frontend\/FrontendPluginRegistry.h\"\n#include \"clang\/AST\/AST.h\"\n#include \"clang\/AST\/ASTConsumer.h\"\n#include \"clang\/Frontend\/CompilerInstance.h\"\n \nusing namespace clang;\n \nnamespace\n{\n class ToyConsumer : public ASTConsumer\n {\n };\n \n class ToyASTAction : public PluginASTAction\n {\n public:\n virtual clang::ASTConsumer *CreateASTConsumer(CompilerInstance &Compiler,\n llvm::StringRef InFile)\n {\n return new ToyConsumer;\n }\n \n bool ParseArgs(const CompilerInstance &CI, const\n std::vector<std::string>& args) {\n return true;\n }\n };\n}\n \nstatic clang::FrontendPluginRegistry::Add<ToyASTAction>\nX(\"ToyClangPlugin\", \"Toy Clang Plugin\");<\/pre>\n\n\n\ncmake_minimum_required (VERSION 2.6)\nproject (ToyClangPlugin)\n\nset( CMAKE_RUNTIME_OUTPUT_DIRECTORY ${CMAKE_BINARY_DIR}\/bin )\nset( CMAKE_LIBRARY_OUTPUT_DIRECTORY ${CMAKE_BINARY_DIR}\/lib )\nset( CMAKE_ARCHIVE_OUTPUT_DIRECTORY ${CMAKE_BINARY_DIR}\/lib )\n\nset( LLVM_HOME \/opt\/llvm )\nset( LLVM_SRC_DIR ${LLVM_HOME}\/llvm )\nset( CLANG_SRC_DIR ${LLVM_HOME}\/llvm\/tools\/clang )\nset( LLVM_BUILD_DIR ${LLVM_HOME}\/llvm_build )\nset( CLANG_BUILD_DIR ${LLVM_HOME}\/llvm_build\/tools\/clang)\n\nadd_definitions (-D__STDC_LIMIT_MACROS -D__STDC_CONSTANT_MACROS)\nadd_definitions (-D_GNU_SOURCE -DHAVE_CLANG_CONFIG_H)\n\nset (CMAKE_CXX_COMPILER \"${LLVM_BUILD_DIR}\/bin\/clang++\")\nset (CMAKE_CC_COMPILER \"${LLVM_BUILD_DIR}\/bin\/clang\")\n\nset (CMAKE_CXX_FLAGS \"${CMAKE_CXX_FLAGS}\n -fPIC\n -fno-common\n -Woverloaded-virtual\n -Wcast-qual\n -fno-strict-aliasing\n -pedantic\n -Wno-long-long\n -Wall\n -Wno-unused-parameter\n -Wwrite-strings\n -fno-exceptions \n -fno-rtti\")\n\nset (CMAKE_MODULE_LINKER_FLAGS \"-Wl,-flat_namespace -Wl,-undefined -Wl,suppress\")\n\nset (LLVM_LIBS\n LLVMJIT\n LLVMX86CodeGen\n LLVMX86AsmParser\n LLVMX86Disassembler\n LLVMExecutionEngine\n LLVMAsmPrinter\n LLVMSelectionDAG\n LLVMX86AsmPrinter\n LLVMX86Info\n LLVMMCParser\n LLVMCodeGen\n LLVMX86Utils\n LLVMScalarOpts\n LLVMInstCombine\n LLVMTransformUtils\n LLVMipa\n LLVMAnalysis\n LLVMTarget\n LLVMCore\n LLVMMC\n LLVMSupport\n LLVMBitReader\n LLVMOption\n)\n\nmacro(add_clang_plugin name)\n set (srcs ${ARGN})\n\n include_directories( \"${LLVM_SRC_DIR}\/include\"\n \"${CLANG_SRC_DIR}\/include\"\n \"${LLVM_BUILD_DIR}\/include\"\n \"${CLANG_BUILD_DIR}\/include\" )\n link_directories( \"${LLVM_BUILD_DIR}\/lib\" )\n\n add_library( ${name} SHARED ${srcs} )\n \n if (SYMBOL_FILE)\n set_target_properties( ${name} PROPERTIES LINK_FlAGS\n \"-exported_symbols_list ${SYMBOL_FILE}\")\n endif()\n\n foreach (clang_lib ${CLANG_LIBS})\n target_link_libraries( ${name} ${clang_lib} ) \n endforeach()\n \n foreach (llvm_lib ${LLVM_LIBS})\n target_link_libraries( ${name} ${llvm_lib} )\n endforeach()\n \n foreach (user_lib ${USER_LIBS})\n target_link_libraries( ${name} ${user_lib} )\n endforeach()\n\nendmacro(add_clang_plugin)\n\nset(SYMBOL_FILE ToyClangPlugin.exports)\n\nset (CLANG_LIBS\n clang\n clangFrontend\n clangAST\n clangAnalysis\n clangBasic\n clangCodeGen\n clangDriver\n clangFrontendTool\n clangLex\n clangParse\n clangSema\n clangEdit\n clangSerialization\n clangStaticAnalyzerCheckers\n clangStaticAnalyzerCore\n clangStaticAnalyzerFrontend\n)\n\nset (USER_LIBS\n pthread\n curses\n)\n\nadd_clang_plugin(ToyClangPlugin \n ToyClangPlugin.cpp\n)\n\nset_target_properties(ToyClangPlugin PROPERTIES\n LINKER_LANGUAGE CXX\n PREFIX \"\")<\/pre>\n\n\n\n__ZN4llvm8Registry*<\/pre>\n\n\n\n
CMakeLists.txt<\/code><\/p>\n\n\n\nmkdir build; cd build\ncmake -G Xcode ..\nopen ToyClangPlugin.xcodeproj<\/pre>\n\n\n\n
ALL_BUILD<\/code> target, and you’ll see dynamic library at lib\/Debug\/ToyCLangPlugin.dylib<\/code>.<\/p>\n\n\n\nRecursiveASTVisitor<\/h4>\n\n\n\n
We just need to create a subclass and implement interesting methods.
For test we’ll print all the found class names.<\/p>\n\n\n\n class ToyClassVisitor : public RecursiveASTVisitor<ToyClassVisitor>\n {\n public:\n bool VisitObjCInterfaceDecl(ObjCInterfaceDecl *declaration)\n {\n printf(\"ObjClass: %s\\n\", declaration->getNameAsString().c_str());\n return true;\n }\n };\n\n class ToyConsumer : public ASTConsumer\n {\n public:\n void HandleTranslationUnit(ASTContext &context) {\n visitor.TraverseDecl(context.getTranslationUnitDecl());\n }\n private:\n ToyClassVisitor visitor;\n };<\/pre>\n\n\n\n#import <Foundation\/Foundation.h>\n\n@interface ToyObject : NSObject\n\n@end\n\n@implementation ToyObject\n\n@end<\/pre>\n\n\n\n
\/opt\/llvm\/toy_clang_plugin\/build $ $LLVM_HOME\/llvm_build\/bin\/clang ..\/test.m \\\n -Xclang -load \\\n -Xclang lib\/Debug\/ToyClangPlugin.dylib \\\n -Xclang -plugin \\\n -Xclang ToyClangPlugin<\/pre>\n\n\n\n
Report warnings<\/h4>\n\n\n\n
ASTContext<\/code> to ToyClassVisitor<\/code><\/p>\n\n\n\nclass ToyClassVisitor : public RecursiveASTVisitor<ToyClassVisitor>\n{\nprivate:\n ASTContext *context;\npublic:\n void setContext(ASTContext &context)\n {\n this->context = &context;\n }\n\/\/ ...\n};\n\n\/\/ ...\nvoid HandleTranslationUnit(ASTContext &context) {\n visitor.setContext(context);\n visitor.TraverseDecl(context.getTranslationUnitDecl());\n}\n \/\/ ...<\/pre>\n\n\n\nbool VisitObjCInterfaceDecl(ObjCInterfaceDecl *declaration)\n{\n checkForLowercasedName(declaration);\n return true;\n}\n\/\/ ...\nvoid checkForLowercasedName(ObjCInterfaceDecl *declaration)\n{\n StringRef name = declaration->getName();\n char c = name[0];\n if (isLowercase(c)) {\n DiagnosticsEngine &diagEngine = context->getDiagnostics();\n unsigned diagID = diagEngine.getCustomDiagID(DiagnosticsEngine::Warning, \"Class name should not start with lowercase letter\");\n SourceLocation location = declaration->getLocation();\n diagEngine.Report(location, diagID);\n }\n}<\/pre>\n\n\n\n@interface bad_ToyObject : NSObject\n\n@end\n\n@implementation bad_ToyObject\n\n@end<\/pre>\n\n\n\n
\/opt\/llvm\/toy_clang_plugin\/build $ $LLVM_HOME\/llvm_build\/bin\/clang ..\/test.m \\\n -Xclang -load \\\n -Xclang lib\/Debug\/ToyClangPlugin.dylib \\\n -Xclang -plugin \\\n -Xclang ToyClangPlugin\n\n..\/test.m:11:12: warning: Class name should not start with lowercase letter\n@interface bad_ToyObject : NSObject\n ^\n1 warning generated.<\/pre>\n\n\n\n
Report error<\/h4>\n\n\n\n
_<\/code><\/p>\n\n\n\nvoid checkForUnderscoreInName(ObjCInterfaceDecl *declaration)\n{\n size_t underscorePos = declaration->getName().find('_');\n if (underscorePos != StringRef::npos) {\n DiagnosticsEngine &diagEngine = context->getDiagnostics();\n unsigned diagID = diagEngine.getCustomDiagID(DiagnosticsEngine::Error, \"Class name with `_` forbidden\");\n SourceLocation location = declaration->getLocation().getLocWithOffset(underscorePos);\n diagEngine.Report(location, diagID);\n }\n}\n\nbool VisitObjCInterfaceDecl(ObjCInterfaceDecl *declaration)\n{\n \/\/ disable this check temporary\n \/\/ checkForLowercasedName(declaration);\n checkForUnderscoreInName(declaration);\n return true;\n}<\/pre>\n\n\n\n\/opt\/llvm\/toy_clang_plugin\/build $ $LLVM_HOME\/llvm_build\/bin\/clang ..\/test.m \\\n -Xclang -load \\\n -Xclang lib\/Debug\/ToyClangPlugin.dylib \\\n -Xclang -plugin \\\n -Xclang ToyClangPlugin\n\n..\/test.m:11:15: error: Class name with `_` forbidden\n@interface bad_ToyObject : NSObject\n ^\n1 error generated.<\/pre>\n\n\n\n
checkForLowercasedName<\/code> and you’ll see both error and warning in the output<\/p>\n\n\n\n\/opt\/llvm\/toy_clang_plugin\/build $ $LLVM_HOME\/llvm_build\/bin\/clang ..\/test.m \\\n -Xclang -load \\\n -Xclang lib\/Debug\/ToyClangPlugin.dylib \\\n -Xclang -plugin \\\n -Xclang ToyClangPlugin\n\n..\/test.m:11:12: warning: Class name should not start with lowercase letter\n@interface bad_ToyObject : NSObject\n ^\n..\/test.m:11:15: error: Class name with `_` forbidden\n@interface bad_ToyObject : NSObject\n ^\n1 warning and 1 error generated.<\/pre>\n\n\n\n
Xcode integration<\/h4>\n\n\n\n
sudo mv HackedClang.xcplugin `xcode-select -print-path`\/..\/PlugIns\/Xcode3Core.ideplugin\/Contents\/SharedSupport\/Developer\/Library\/Xcode\/Plug-ins\nsudo mv HackedBuildSystem.xcspec `xcode-select -print-path`\/Platforms\/iPhoneSimulator.platform\/Developer\/Library\/Xcode\/Specifications<\/pre>\n\n\n\n
![\"custom_compiler\"\/](\"\/\/railsware.com\/blog\/wp-content\/uploads\/2014\/02\/custom_compiler.png\")
<\/figure>\n\n\n\nBuild settings<\/code><\/p>\n\n\n\nOTHER_CFLAGS<\/code> section<\/p>\n\n\n\n-Xclang -load -Xclang \/opt\/llvm\/toy_clang_plugin\/build\/lib\/Debug\/ToyClangPlugin.dylib -Xclang -add-plugin -Xclang ToyClangPlugin<\/pre>\n\n\n\n
![\"OTHER_CFLAGS\"\/](\"\/\/railsware.com\/blog\/wp-content\/uploads\/2014\/02\/other_cflags.png\")
<\/figure>\n\n\n\n-add-plugin<\/code> here, because we want to add our ASTAction<\/code>, not to replace the existing<\/p>\n\n\n\n![\"disable_modules\"\/](\"\/\/railsware.com\/blog\/wp-content\/uploads\/2014\/02\/disable_modules.png\")
<\/figure>\n\n\n\ntest.m<\/code> to this project, or create new one, with class names that match plugin criteria<\/p>\n\n\n\n![\"error_warning\"\/](\"\/\/railsware.com\/blog\/wp-content\/uploads\/2014\/02\/error_warning.png\")
<\/figure>\n\n\n\nInteractive hints<\/h4>\n\n\n\n
FixItHints<\/code> for both warning and error<\/p>\n\n\n\nvoid checkForLowercasedName(ObjCInterfaceDecl *declaration)\n{\n StringRef name = declaration->getName();\n char c = name[0];\n if (isLowercase(c)) {\n std::string tempName = name;\n tempName[0] = toUppercase(c);\n StringRef replacement(tempName);\n \n SourceLocation nameStart = declaration->getLocation();\n SourceLocation nameEnd = nameStart.getLocWithOffset(name.size());\n \n FixItHint fixItHint = FixItHint::CreateReplacement(SourceRange(nameStart, nameEnd), replacement);\n \n DiagnosticsEngine &diagEngine = context->getDiagnostics();\n unsigned diagID = diagEngine.getCustomDiagID(DiagnosticsEngine::Warning, \"Class name should not start with lowercase letter\");\n SourceLocation location = declaration->getLocation();\n diagEngine.Report(location, diagID).AddFixItHint(fixItHint);\n }\n}\n\nvoid checkForUnderscoreInName(ObjCInterfaceDecl *declaration)\n{\n StringRef name = declaration->getName();\n size_t underscorePos = name.find('_');\n if (underscorePos != StringRef::npos) {\n std::string tempName = name;\n std::string::iterator end_pos = std::remove(tempName.begin(), tempName.end(), '_');\n tempName.erase(end_pos, tempName.end());\n StringRef replacement(tempName);\n \n SourceLocation nameStart = declaration->getLocation();\n SourceLocation nameEnd = nameStart.getLocWithOffset(name.size());\n \n FixItHint fixItHint = FixItHint::CreateReplacement(SourceRange(nameStart, nameEnd), replacement);\n \n DiagnosticsEngine &diagEngine = context->getDiagnostics();\n unsigned diagID = diagEngine.getCustomDiagID(DiagnosticsEngine::Error, \"Class name with `_` forbidden\");\n SourceLocation location = declaration->getLocation().getLocWithOffset(underscorePos);\n diagEngine.Report(location, diagID).AddFixItHint(fixItHint);\n }\n}<\/pre>\n\n\n\n![\"warning_fixit_hint\"\/](\"\/\/railsware.com\/blog\/wp-content\/uploads\/2014\/02\/warning_fixit_hint.png\")
<\/figure>\n\n\n\n![\"error_fixit_hint\"\/](\"\/\/railsware.com\/blog\/wp-content\/uploads\/2014\/02\/error_fixit_hint.png\")
<\/figure>\n\n\n\nConclusion<\/h4>\n\n\n\n
Another issue you might face is unstable API, cause it uses internal API which changes continuously.<\/p>\n\n\n\n