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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                                const CheckerBase *Checker) {
     45 
     46   QualType ResDerived = MethDerived->getReturnType();
     47   QualType ResAncestor = MethAncestor->getReturnType();
     48 
     49   if (!AreTypesCompatible(ResDerived, ResAncestor, Ctx)) {
     50     std::string sbuf;
     51     llvm::raw_string_ostream os(sbuf);
     52 
     53     os << "The Objective-C class '"
     54        << *MethDerived->getClassInterface()
     55        << "', which is derived from class '"
     56        << *MethAncestor->getClassInterface()
     57        << "', defines the instance method '";
     58     MethDerived->getSelector().print(os);
     59     os << "' whose return type is '"
     60        << ResDerived.getAsString()
     61        << "'.  A method with the same name (same selector) is also defined in "
     62           "class '"
     63        << *MethAncestor->getClassInterface()
     64        << "' and has a return type of '"
     65        << ResAncestor.getAsString()
     66        << "'.  These two types are incompatible, and may result in undefined "
     67           "behavior for clients of these classes.";
     68 
     69     PathDiagnosticLocation MethDLoc =
     70       PathDiagnosticLocation::createBegin(MethDerived,
     71                                           BR.getSourceManager());
     72 
     73     BR.EmitBasicReport(
     74         MethDerived, Checker, "Incompatible instance method return type",
     75         categories::CoreFoundationObjectiveC, os.str(), MethDLoc);
     76   }
     77 }
     78 
     79 static void CheckObjCInstMethSignature(const ObjCImplementationDecl *ID,
     80                                        BugReporter &BR,
     81                                        const CheckerBase *Checker) {
     82 
     83   const ObjCInterfaceDecl *D = ID->getClassInterface();
     84   const ObjCInterfaceDecl *C = D->getSuperClass();
     85 
     86   if (!C)
     87     return;
     88 
     89   ASTContext &Ctx = BR.getContext();
     90 
     91   // Build a DenseMap of the methods for quick querying.
     92   typedef llvm::DenseMap<Selector,ObjCMethodDecl*> MapTy;
     93   MapTy IMeths;
     94   unsigned NumMethods = 0;
     95 
     96   for (auto *M : ID->instance_methods()) {
     97     IMeths[M->getSelector()] = M;
     98     ++NumMethods;
     99   }
    100 
    101   // Now recurse the class hierarchy chain looking for methods with the
    102   // same signatures.
    103   while (C && NumMethods) {
    104     for (const auto *M : C->instance_methods()) {
    105       Selector S = M->getSelector();
    106 
    107       MapTy::iterator MI = IMeths.find(S);
    108 
    109       if (MI == IMeths.end() || MI->second == nullptr)
    110         continue;
    111 
    112       --NumMethods;
    113       ObjCMethodDecl *MethDerived = MI->second;
    114       MI->second = nullptr;
    115 
    116       CompareReturnTypes(MethDerived, M, BR, Ctx, ID, Checker);
    117     }
    118 
    119     C = C->getSuperClass();
    120   }
    121 }
    122 
    123 //===----------------------------------------------------------------------===//
    124 // ObjCMethSigsChecker
    125 //===----------------------------------------------------------------------===//
    126 
    127 namespace {
    128 class ObjCMethSigsChecker : public Checker<
    129                                       check::ASTDecl<ObjCImplementationDecl> > {
    130 public:
    131   void checkASTDecl(const ObjCImplementationDecl *D, AnalysisManager& mgr,
    132                     BugReporter &BR) const {
    133     CheckObjCInstMethSignature(D, BR, this);
    134   }
    135 };
    136 }
    137 
    138 void ento::registerObjCMethSigsChecker(CheckerManager &mgr) {
    139   mgr.registerChecker<ObjCMethSigsChecker>();
    140 }
    141