1 //==- ObjCUnusedIVarsChecker.cpp - Check for unused ivars --------*- C++ -*-==// 2 // 3 // The LLVM Compiler Infrastructure 4 // 5 // This file is distributed under the University of Illinois Open Source 6 // License. See LICENSE.TXT for details. 7 // 8 //===----------------------------------------------------------------------===// 9 // 10 // This file defines a CheckObjCUnusedIvars, a checker that 11 // analyzes an Objective-C class's interface/implementation to determine if it 12 // has any ivars that are never accessed. 13 // 14 //===----------------------------------------------------------------------===// 15 16 #include "ClangSACheckers.h" 17 #include "clang/StaticAnalyzer/Core/Checker.h" 18 #include "clang/StaticAnalyzer/Core/BugReporter/PathDiagnostic.h" 19 #include "clang/StaticAnalyzer/Core/BugReporter/BugReporter.h" 20 #include "clang/AST/ExprObjC.h" 21 #include "clang/AST/Expr.h" 22 #include "clang/AST/DeclObjC.h" 23 #include "clang/Basic/LangOptions.h" 24 #include "clang/Basic/SourceManager.h" 25 26 using namespace clang; 27 using namespace ento; 28 29 enum IVarState { Unused, Used }; 30 typedef llvm::DenseMap<const ObjCIvarDecl*,IVarState> IvarUsageMap; 31 32 static void Scan(IvarUsageMap& M, const Stmt *S) { 33 if (!S) 34 return; 35 36 if (const ObjCIvarRefExpr *Ex = dyn_cast<ObjCIvarRefExpr>(S)) { 37 const ObjCIvarDecl *D = Ex->getDecl(); 38 IvarUsageMap::iterator I = M.find(D); 39 if (I != M.end()) 40 I->second = Used; 41 return; 42 } 43 44 // Blocks can reference an instance variable of a class. 45 if (const BlockExpr *BE = dyn_cast<BlockExpr>(S)) { 46 Scan(M, BE->getBody()); 47 return; 48 } 49 50 for (Stmt::const_child_iterator I=S->child_begin(),E=S->child_end(); I!=E;++I) 51 Scan(M, *I); 52 } 53 54 static void Scan(IvarUsageMap& M, const ObjCPropertyImplDecl *D) { 55 if (!D) 56 return; 57 58 const ObjCIvarDecl *ID = D->getPropertyIvarDecl(); 59 60 if (!ID) 61 return; 62 63 IvarUsageMap::iterator I = M.find(ID); 64 if (I != M.end()) 65 I->second = Used; 66 } 67 68 static void Scan(IvarUsageMap& M, const ObjCContainerDecl *D) { 69 // Scan the methods for accesses. 70 for (ObjCContainerDecl::instmeth_iterator I = D->instmeth_begin(), 71 E = D->instmeth_end(); I!=E; ++I) 72 Scan(M, (*I)->getBody()); 73 74 if (const ObjCImplementationDecl *ID = dyn_cast<ObjCImplementationDecl>(D)) { 75 // Scan for @synthesized property methods that act as setters/getters 76 // to an ivar. 77 for (ObjCImplementationDecl::propimpl_iterator I = ID->propimpl_begin(), 78 E = ID->propimpl_end(); I!=E; ++I) 79 Scan(M, *I); 80 81 // Scan the associated categories as well. 82 for (const ObjCCategoryDecl *CD = 83 ID->getClassInterface()->getCategoryList(); CD ; 84 CD = CD->getNextClassCategory()) { 85 if (const ObjCCategoryImplDecl *CID = CD->getImplementation()) 86 Scan(M, CID); 87 } 88 } 89 } 90 91 static void Scan(IvarUsageMap &M, const DeclContext *C, const FileID FID, 92 SourceManager &SM) { 93 for (DeclContext::decl_iterator I=C->decls_begin(), E=C->decls_end(); 94 I!=E; ++I) 95 if (const FunctionDecl *FD = dyn_cast<FunctionDecl>(*I)) { 96 SourceLocation L = FD->getLocStart(); 97 if (SM.getFileID(L) == FID) 98 Scan(M, FD->getBody()); 99 } 100 } 101 102 static void checkObjCUnusedIvar(const ObjCImplementationDecl *D, 103 BugReporter &BR) { 104 105 const ObjCInterfaceDecl *ID = D->getClassInterface(); 106 IvarUsageMap M; 107 108 // Iterate over the ivars. 109 for (ObjCInterfaceDecl::ivar_iterator I=ID->ivar_begin(), 110 E=ID->ivar_end(); I!=E; ++I) { 111 112 const ObjCIvarDecl *ID = *I; 113 114 // Ignore ivars that... 115 // (a) aren't private 116 // (b) explicitly marked unused 117 // (c) are iboutlets 118 // (d) are unnamed bitfields 119 if (ID->getAccessControl() != ObjCIvarDecl::Private || 120 ID->getAttr<UnusedAttr>() || ID->getAttr<IBOutletAttr>() || 121 ID->getAttr<IBOutletCollectionAttr>() || 122 ID->isUnnamedBitfield()) 123 continue; 124 125 M[ID] = Unused; 126 } 127 128 if (M.empty()) 129 return; 130 131 // Now scan the implementation declaration. 132 Scan(M, D); 133 134 // Any potentially unused ivars? 135 bool hasUnused = false; 136 for (IvarUsageMap::iterator I = M.begin(), E = M.end(); I!=E; ++I) 137 if (I->second == Unused) { 138 hasUnused = true; 139 break; 140 } 141 142 if (!hasUnused) 143 return; 144 145 // We found some potentially unused ivars. Scan the entire translation unit 146 // for functions inside the @implementation that reference these ivars. 147 // FIXME: In the future hopefully we can just use the lexical DeclContext 148 // to go from the ObjCImplementationDecl to the lexically "nested" 149 // C functions. 150 SourceManager &SM = BR.getSourceManager(); 151 Scan(M, D->getDeclContext(), SM.getFileID(D->getLocation()), SM); 152 153 // Find ivars that are unused. 154 for (IvarUsageMap::iterator I = M.begin(), E = M.end(); I!=E; ++I) 155 if (I->second == Unused) { 156 std::string sbuf; 157 llvm::raw_string_ostream os(sbuf); 158 os << "Instance variable '" << *I->first << "' in class '" << *ID 159 << "' is never used by the methods in its @implementation " 160 "(although it may be used by category methods)."; 161 162 PathDiagnosticLocation L = 163 PathDiagnosticLocation::create(I->first, BR.getSourceManager()); 164 BR.EmitBasicReport("Unused instance variable", "Optimization", 165 os.str(), L); 166 } 167 } 168 169 //===----------------------------------------------------------------------===// 170 // ObjCUnusedIvarsChecker 171 //===----------------------------------------------------------------------===// 172 173 namespace { 174 class ObjCUnusedIvarsChecker : public Checker< 175 check::ASTDecl<ObjCImplementationDecl> > { 176 public: 177 void checkASTDecl(const ObjCImplementationDecl *D, AnalysisManager& mgr, 178 BugReporter &BR) const { 179 checkObjCUnusedIvar(D, BR); 180 } 181 }; 182 } 183 184 void ento::registerObjCUnusedIvarsChecker(CheckerManager &mgr) { 185 mgr.registerChecker<ObjCUnusedIvarsChecker>(); 186 } 187