Home | History | Annotate | Download | only in Checkers 
      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(D, "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