text: // MallocSizeofChecker.cpp - Check for dubious malloc arguments ---*- C++ -*-=//
  //
  //                     The LLVM Compiler Infrastructure
  //
  // This file is distributed under the University of Illinois Open Source
  // License. See LICENSE.TXT for details.
  //
  //===----------------------------------------------------------------------===//
  //
  // Reports inconsistencies between the casted type of the return value of a
  // malloc/calloc/realloc call and the operand of any sizeof expressions
  // contained within its argument(s).
  //
  //===----------------------------------------------------------------------===//
  
  #include "ClangSACheckers.h"
  #include "clang/AST/StmtVisitor.h"
  #include "clang/AST/TypeLoc.h"
  #include "clang/StaticAnalyzer/Core/BugReporter/BugReporter.h"
  #include "clang/StaticAnalyzer/Core/Checker.h"
  #include "clang/StaticAnalyzer/Core/CheckerManager.h"
  #include "clang/StaticAnalyzer/Core/PathSensitive/AnalysisManager.h"
  #include "llvm/ADT/SmallString.h"
  #include "llvm/Support/raw_ostream.h"
  
  using namespace clang;
  using namespace ento;
  
  namespace {
  
  typedef std::pair<const TypeSourceInfo *, const CallExpr *> TypeCallPair;
  typedef llvm::PointerUnion<const Stmt *, const VarDecl *> ExprParent;
  
  class CastedAllocFinder
    : public ConstStmtVisitor<CastedAllocFinder, TypeCallPair> {
    IdentifierInfo *II_malloc, *II_calloc, *II_realloc;
  
  public:
    struct CallRecord {
      ExprParent CastedExprParent;
      const Expr *CastedExpr;
      const TypeSourceInfo *ExplicitCastType;
      const CallExpr *AllocCall;
  
      CallRecord(ExprParent CastedExprParent, const Expr *CastedExpr,
                 const TypeSourceInfo *ExplicitCastType,
                 const CallExpr *AllocCall)
        : CastedExprParent(CastedExprParent), CastedExpr(CastedExpr),
          ExplicitCastType(ExplicitCastType), AllocCall(AllocCall) {}
    };
  
    typedef std::vector<CallRecord> CallVec;
    CallVec Calls;
  
    CastedAllocFinder(ASTContext *Ctx) :
      II_malloc(&Ctx->Idents.get("malloc")),
      II_calloc(&Ctx->Idents.get("calloc")),
      II_realloc(&Ctx->Idents.get("realloc")) {}
  
    void VisitChild(ExprParent Parent, const Stmt *S) {
      TypeCallPair AllocCall = Visit(S);
      if (AllocCall.second && AllocCall.second != S)
        Calls.push_back(CallRecord(Parent, cast<Expr>(S), AllocCall.first,
                                   AllocCall.second));
    }
  
    void VisitChildren(const Stmt *S) {
      for (Stmt::const_child_iterator I = S->child_begin(), E = S->child_end();
           I!=E; ++I)
        if (const Stmt *child = *I)
          VisitChild(S, child);
    }
  
    TypeCallPair VisitCastExpr(const CastExpr *E) {
      return Visit(E->getSubExpr());
    }
  
    TypeCallPair VisitExplicitCastExpr(const ExplicitCastExpr *E) {
      return TypeCallPair(E->getTypeInfoAsWritten(),
                          Visit(E->getSubExpr()).second);
    }
  
    TypeCallPair VisitParenExpr(const ParenExpr *E) {
      return Visit(E->getSubExpr());
    }
  
    TypeCallPair VisitStmt(const Stmt *S) {
      VisitChildren(S);
      return TypeCallPair();
    }
  
    TypeCallPair VisitCallExpr(const CallExpr *E) {
      VisitChildren(E);
      const FunctionDecl *FD = E->getDirectCallee();
      if (FD) {
        IdentifierInfo *II = FD->getIdentifier();
        if (II == II_malloc || II == II_calloc || II == II_realloc)
          return TypeCallPair((const TypeSourceInfo *)0, E);
      }
      return TypeCallPair();
    }
  
    TypeCallPair VisitDeclStmt(const DeclStmt *S) {
      for (DeclStmt::const_decl_iterator I = S->decl_begin(), E = S->decl_end();
           I!=E; ++I)
        if (const VarDecl *VD = dyn_cast<VarDecl>(*I))
          if (const Expr *Init = VD->getInit())
            VisitChild(VD, Init);
      return TypeCallPair();
    }
  };
  
  class SizeofFinder : public ConstStmtVisitor<SizeofFinder> {
  public:
    std::vector<const UnaryExprOrTypeTraitExpr *> Sizeofs;
  
    void VisitBinMul(const BinaryOperator *E) {
      Visit(E->getLHS());
      Visit(E->getRHS());
    }
  
    void VisitImplicitCastExpr(const ImplicitCastExpr *E) {
      return Visit(E->getSubExpr());
    }
  
    void VisitParenExpr(const ParenExpr *E) {
      return Visit(E->getSubExpr());
    }
  
    void VisitUnaryExprOrTypeTraitExpr(const UnaryExprOrTypeTraitExpr *E) {
      if (E->getKind() != UETT_SizeOf)
        return;
  
      Sizeofs.push_back(E);
    }
  };
  
  // Determine if the pointee and sizeof types are compatible.  Here
  // we ignore constness of pointer types.
  static bool typesCompatible(ASTContext &C, QualType A, QualType B) {
    while (true) {
      A = A.getCanonicalType();
      B = B.getCanonicalType();
    
      if (A.getTypePtr() == B.getTypePtr())
        return true;
      
      if (const PointerType *ptrA = A->getAs<PointerType>())
        if (const PointerType *ptrB = B->getAs<PointerType>()) {
          A = ptrA->getPointeeType();
          B = ptrB->getPointeeType();
          continue;
        }
        
      break;
    }
    
    return false;
  }
  
  static bool compatibleWithArrayType(ASTContext &C, QualType PT, QualType T) {
    // Ex: 'int a[10][2]' is compatible with 'int', 'int[2]', 'int[10][2]'.
    while (const ArrayType *AT = T->getAsArrayTypeUnsafe()) {
      QualType ElemType = AT->getElementType();
      if (typesCompatible(C, PT, AT->getElementType()))
        return true;
      T = ElemType;
    }
  
    return false;
  }
  
  class MallocSizeofChecker : public Checker<check::ASTCodeBody> {
  public:
    void checkASTCodeBody(const Decl *D, AnalysisManager& mgr,
                          BugReporter &BR) const {
      AnalysisDeclContext *ADC = mgr.getAnalysisDeclContext(D);
      CastedAllocFinder Finder(&BR.getContext());
      Finder.Visit(D->getBody());
      for (CastedAllocFinder::CallVec::iterator i = Finder.Calls.begin(),
           e = Finder.Calls.end(); i != e; ++i) {
        QualType CastedType = i->CastedExpr->getType();
        if (!CastedType->isPointerType())
          continue;
        QualType PointeeType = CastedType->getAs<PointerType>()->getPointeeType();
        if (PointeeType->isVoidType())
          continue;
  
        for (CallExpr::const_arg_iterator ai = i->AllocCall->arg_begin(),
             ae = i->AllocCall->arg_end(); ai != ae; ++ai) {
          if (!(*ai)->getType()->isIntegralOrUnscopedEnumerationType())
            continue;
  
          SizeofFinder SFinder;
          SFinder.Visit(*ai);
          if (SFinder.Sizeofs.size() != 1)
            continue;
  
          QualType SizeofType = SFinder.Sizeofs[0]->getTypeOfArgument();
  
          if (typesCompatible(BR.getContext(), PointeeType, SizeofType))
            continue;
  
          // If the argument to sizeof is an array, the result could be a
          // pointer to any array element.
          if (compatibleWithArrayType(BR.getContext(), PointeeType, SizeofType))
            continue;
  
          const TypeSourceInfo *TSI = 0;
          if (i->CastedExprParent.is<const VarDecl *>()) {
            TSI =
                i->CastedExprParent.get<const VarDecl *>()->getTypeSourceInfo();
          } else {
            TSI = i->ExplicitCastType;
          }
  
          SmallString<64> buf;
          llvm::raw_svector_ostream OS(buf);
  
          OS << "Result of ";
          const FunctionDecl *Callee = i->AllocCall->getDirectCallee();
          if (Callee && Callee->getIdentifier())
            OS << '\'' << Callee->getIdentifier()->getName() << '\'';
          else
            OS << "call";
          OS << " is converted to a pointer of type '"
              << PointeeType.getAsString() << "', which is incompatible with "
              << "sizeof operand type '" << SizeofType.getAsString() << "'";
          SmallVector<SourceRange, 4> Ranges;
          Ranges.push_back(i->AllocCall->getCallee()->getSourceRange());
          Ranges.push_back(SFinder.Sizeofs[0]->getSourceRange());
          if (TSI)
            Ranges.push_back(TSI->getTypeLoc().getSourceRange());
  
          PathDiagnosticLocation L =
              PathDiagnosticLocation::createBegin(i->AllocCall->getCallee(),
                  BR.getSourceManager(), ADC);
  
          BR.EmitBasicReport(D, "Allocator sizeof operand mismatch",
              categories::UnixAPI,
              OS.str(),
              L, Ranges.data(), Ranges.size());
        }
      }
    }
  };
  
  }
  
  void ento::registerMallocSizeofChecker(CheckerManager &mgr) {
    mgr.registerChecker<MallocSizeofChecker>();
  }
  