lib/StaticAnalyzer/Checkers/ObjCUnusedIVarsChecker.cpp

   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/CheckerV2.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       BR.EmitBasicReport("Unused instance variable", "Optimization",
 163                          os.str(), I->first->getLocation());
 164     }
 165 }
 166
 167 //===----------------------------------------------------------------------===//
 168 // ObjCUnusedIvarsChecker
 169 //===----------------------------------------------------------------------===//
 170
 171 namespace {
 172 class ObjCUnusedIvarsChecker : public CheckerV2<
 173                                       check::ASTDecl<ObjCImplementationDecl> > {
 174 public:
 175   void checkASTDecl(const ObjCImplementationDecl *D, AnalysisManager& mgr,
 176                     BugReporter &BR) const {
 177     checkObjCUnusedIvar(D, BR);
 178   }
 179 };
 180 }
 181
 182 void ento::registerObjCUnusedIvarsChecker(CheckerManager &mgr) {
 183   mgr.registerChecker<ObjCUnusedIvarsChecker>();
 184 }