lib/GR/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 "clang/GR/Checkers/LocalCheckers.h"
  17 #include "clang/GR/BugReporter/PathDiagnostic.h"
  18 #include "clang/GR/BugReporter/BugReporter.h"
  19 #include "clang/AST/ExprObjC.h"
  20 #include "clang/AST/Expr.h"
  21 #include "clang/AST/DeclObjC.h"
  22 #include "clang/Basic/LangOptions.h"
  23 #include "clang/Basic/SourceManager.h"
  24
  25 using namespace clang;
  26 using namespace GR;
  27
  28 enum IVarState { Unused, Used };
  29 typedef llvm::DenseMap<const ObjCIvarDecl*,IVarState> IvarUsageMap;
  30
  31 static void Scan(IvarUsageMap& M, const Stmt* S) {
  32   if (!S)
  33     return;
  34
  35   if (const ObjCIvarRefExpr *Ex = dyn_cast<ObjCIvarRefExpr>(S)) {
  36     const ObjCIvarDecl *D = Ex->getDecl();
  37     IvarUsageMap::iterator I = M.find(D);
  38     if (I != M.end())
  39       I->second = Used;
  40     return;
  41   }
  42
  43   // Blocks can reference an instance variable of a class.
  44   if (const BlockExpr *BE = dyn_cast<BlockExpr>(S)) {
  45     Scan(M, BE->getBody());
  46     return;
  47   }
  48
  49   for (Stmt::const_child_iterator I=S->child_begin(),E=S->child_end(); I!=E;++I)
  50     Scan(M, *I);
  51 }
  52
  53 static void Scan(IvarUsageMap& M, const ObjCPropertyImplDecl* D) {
  54   if (!D)
  55     return;
  56
  57   const ObjCIvarDecl* ID = D->getPropertyIvarDecl();
  58
  59   if (!ID)
  60     return;
  61
  62   IvarUsageMap::iterator I = M.find(ID);
  63   if (I != M.end())
  64     I->second = Used;
  65 }
  66
  67 static void Scan(IvarUsageMap& M, const ObjCContainerDecl* D) {
  68   // Scan the methods for accesses.
  69   for (ObjCContainerDecl::instmeth_iterator I = D->instmeth_begin(),
  70        E = D->instmeth_end(); I!=E; ++I)
  71     Scan(M, (*I)->getBody());
  72
  73   if (const ObjCImplementationDecl *ID = dyn_cast<ObjCImplementationDecl>(D)) {
  74     // Scan for @synthesized property methods that act as setters/getters
  75     // to an ivar.
  76     for (ObjCImplementationDecl::propimpl_iterator I = ID->propimpl_begin(),
  77          E = ID->propimpl_end(); I!=E; ++I)
  78       Scan(M, *I);
  79
  80     // Scan the associated categories as well.
  81     for (const ObjCCategoryDecl *CD =
  82           ID->getClassInterface()->getCategoryList(); CD ;
  83           CD = CD->getNextClassCategory()) {
  84       if (const ObjCCategoryImplDecl *CID = CD->getImplementation())
  85         Scan(M, CID);
  86     }
  87   }
  88 }
  89
  90 static void Scan(IvarUsageMap &M, const DeclContext *C, const FileID FID,
  91                  SourceManager &SM) {
  92   for (DeclContext::decl_iterator I=C->decls_begin(), E=C->decls_end();
  93        I!=E; ++I)
  94     if (const FunctionDecl *FD = dyn_cast<FunctionDecl>(*I)) {
  95       SourceLocation L = FD->getLocStart();
  96       if (SM.getFileID(L) == FID)
  97         Scan(M, FD->getBody());
  98     }
  99 }
 100
 101 void GR::CheckObjCUnusedIvar(const ObjCImplementationDecl *D,
 102                                 BugReporter &BR) {
 103
 104   const ObjCInterfaceDecl* ID = D->getClassInterface();
 105   IvarUsageMap M;
 106
 107   // Iterate over the ivars.
 108   for (ObjCInterfaceDecl::ivar_iterator I=ID->ivar_begin(),
 109         E=ID->ivar_end(); I!=E; ++I) {
 110
 111     const ObjCIvarDecl* ID = *I;
 112
 113     // Ignore ivars that...
 114     // (a) aren't private
 115     // (b) explicitly marked unused
 116     // (c) are iboutlets
 117     // (d) are unnamed bitfields
 118     if (ID->getAccessControl() != ObjCIvarDecl::Private ||
 119         ID->getAttr<UnusedAttr>() || ID->getAttr<IBOutletAttr>() ||
 120         ID->getAttr<IBOutletCollectionAttr>() ||
 121         ID->isUnnamedBitfield())
 122       continue;
 123
 124     M[ID] = Unused;
 125   }
 126
 127   if (M.empty())
 128     return;
 129
 130   // Now scan the implementation declaration.
 131   Scan(M, D);
 132
 133   // Any potentially unused ivars?
 134   bool hasUnused = false;
 135   for (IvarUsageMap::iterator I = M.begin(), E = M.end(); I!=E; ++I)
 136     if (I->second == Unused) {
 137       hasUnused = true;
 138       break;
 139     }
 140
 141   if (!hasUnused)
 142     return;
 143
 144   // We found some potentially unused ivars.  Scan the entire translation unit
 145   // for functions inside the @implementation that reference these ivars.
 146   // FIXME: In the future hopefully we can just use the lexical DeclContext
 147   // to go from the ObjCImplementationDecl to the lexically "nested"
 148   // C functions.
 149   SourceManager &SM = BR.getSourceManager();
 150   Scan(M, D->getDeclContext(), SM.getFileID(D->getLocation()), SM);
 151
 152   // Find ivars that are unused.
 153   for (IvarUsageMap::iterator I = M.begin(), E = M.end(); I!=E; ++I)
 154     if (I->second == Unused) {
 155       std::string sbuf;
 156       llvm::raw_string_ostream os(sbuf);
 157       os << "Instance variable '" << I->first << "' in class '" << ID
 158          << "' is never used by the methods in its @implementation "
 159             "(although it may be used by category methods).";
 160
 161       BR.EmitBasicReport("Unused instance variable", "Optimization",
 162                          os.str(), I->first->getLocation());
 163     }
 164 }