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      1 //=- CheckObjCInstMethodRetTy.cpp - Check ObjC method signatures -*- 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 CheckObjCInstMethSignature, a flow-insenstive check
     11 //  that determines if an Objective-C class interface incorrectly redefines
     12 //  the method signature in a subclass.
     13 //
     14 //===----------------------------------------------------------------------===//
     15 
     16 #include "ClangSACheckers.h"
     17 #include "clang/AST/ASTContext.h"
     18 #include "clang/AST/DeclObjC.h"
     19 #include "clang/AST/Type.h"
     20 #include "clang/StaticAnalyzer/Core/BugReporter/BugReporter.h"
     21 #include "clang/StaticAnalyzer/Core/BugReporter/PathDiagnostic.h"
     22 #include "clang/StaticAnalyzer/Core/Checker.h"
     23 #include "llvm/ADT/DenseMap.h"
     24 #include "llvm/Support/raw_ostream.h"
     25 
     26 using namespace clang;
     27 using namespace ento;
     28 
     29 static bool AreTypesCompatible(QualType Derived, QualType Ancestor,
     30                                ASTContext &C) {
     31 
     32   // Right now don't compare the compatibility of pointers.  That involves
     33   // looking at subtyping relationships.  FIXME: Future patch.
     34   if (Derived->isAnyPointerType() &&  Ancestor->isAnyPointerType())
     35     return true;
     36 
     37   return C.typesAreCompatible(Derived, Ancestor);
     38 }
     39 
     40 static void CompareReturnTypes(const ObjCMethodDecl *MethDerived,
     41                                const ObjCMethodDecl *MethAncestor,
     42                                BugReporter &BR, ASTContext &Ctx,
     43                                const ObjCImplementationDecl *ID) {
     44 
     45   QualType ResDerived  = MethDerived->getResultType();
     46   QualType ResAncestor = MethAncestor->getResultType();
     47 
     48   if (!AreTypesCompatible(ResDerived, ResAncestor, Ctx)) {
     49     std::string sbuf;
     50     llvm::raw_string_ostream os(sbuf);
     51 
     52     os << "The Objective-C class '"
     53        << *MethDerived->getClassInterface()
     54        << "', which is derived from class '"
     55        << *MethAncestor->getClassInterface()
     56        << "', defines the instance method '"
     57        << MethDerived->getSelector().getAsString()
     58        << "' whose return type is '"
     59        << ResDerived.getAsString()
     60        << "'.  A method with the same name (same selector) is also defined in "
     61           "class '"
     62        << *MethAncestor->getClassInterface()
     63        << "' and has a return type of '"
     64        << ResAncestor.getAsString()
     65        << "'.  These two types are incompatible, and may result in undefined "
     66           "behavior for clients of these classes.";
     67 
     68     PathDiagnosticLocation MethDLoc =
     69       PathDiagnosticLocation::createBegin(MethDerived,
     70                                           BR.getSourceManager());
     71 
     72     BR.EmitBasicReport(MethDerived,
     73                        "Incompatible instance method return type",
     74                        categories::CoreFoundationObjectiveC,
     75                        os.str(), MethDLoc);
     76   }
     77 }
     78 
     79 static void CheckObjCInstMethSignature(const ObjCImplementationDecl *ID,
     80                                        BugReporter& BR) {
     81 
     82   const ObjCInterfaceDecl *D = ID->getClassInterface();
     83   const ObjCInterfaceDecl *C = D->getSuperClass();
     84 
     85   if (!C)
     86     return;
     87 
     88   ASTContext &Ctx = BR.getContext();
     89 
     90   // Build a DenseMap of the methods for quick querying.
     91   typedef llvm::DenseMap<Selector,ObjCMethodDecl*> MapTy;
     92   MapTy IMeths;
     93   unsigned NumMethods = 0;
     94 
     95   for (ObjCImplementationDecl::instmeth_iterator I=ID->instmeth_begin(),
     96        E=ID->instmeth_end(); I!=E; ++I) {
     97 
     98     ObjCMethodDecl *M = *I;
     99     IMeths[M->getSelector()] = M;
    100     ++NumMethods;
    101   }
    102 
    103   // Now recurse the class hierarchy chain looking for methods with the
    104   // same signatures.
    105   while (C && NumMethods) {
    106     for (ObjCInterfaceDecl::instmeth_iterator I=C->instmeth_begin(),
    107          E=C->instmeth_end(); I!=E; ++I) {
    108 
    109       ObjCMethodDecl *M = *I;
    110       Selector S = M->getSelector();
    111 
    112       MapTy::iterator MI = IMeths.find(S);
    113 
    114       if (MI == IMeths.end() || MI->second == 0)
    115         continue;
    116 
    117       --NumMethods;
    118       ObjCMethodDecl *MethDerived = MI->second;
    119       MI->second = 0;
    120 
    121       CompareReturnTypes(MethDerived, M, BR, Ctx, ID);
    122     }
    123 
    124     C = C->getSuperClass();
    125   }
    126 }
    127 
    128 //===----------------------------------------------------------------------===//
    129 // ObjCMethSigsChecker
    130 //===----------------------------------------------------------------------===//
    131 
    132 namespace {
    133 class ObjCMethSigsChecker : public Checker<
    134                                       check::ASTDecl<ObjCImplementationDecl> > {
    135 public:
    136   void checkASTDecl(const ObjCImplementationDecl *D, AnalysisManager& mgr,
    137                     BugReporter &BR) const {
    138     CheckObjCInstMethSignature(D, BR);
    139   }
    140 };
    141 }
    142 
    143 void ento::registerObjCMethSigsChecker(CheckerManager &mgr) {
    144   mgr.registerChecker<ObjCMethSigsChecker>();
    145 }
    146