[cfe-commits] r88988 - /cfe/trunk/lib/CodeGen/CGCXXExpr.cpp

[Ted Kremenek]

Hi Mike,

I think you introduced an uninitialized variable bug in this commit:

llvm[4]: Compiling CGCXXExpr.cpp for Release build
/Users/kremenek/llvm/tools/clang/lib/CodeGen/CGCXXExpr.cpp: In member function ‘llvm::Value* clang::CodeGen::CodeGenFunction::EmitDynamicCast(llvm::Value*, const clang::CXXDynamicCastExpr*)’:
/Users/kremenek/llvm/tools/clang/lib/CodeGen/CGCXXExpr.cpp:500: warning: ‘FBadTy’ is used uninitialized in this function


On Nov 16, 2009, at 2:52 PM, Mike Stump wrote:

> Author: mrs
> Date: Mon Nov 16 16:52:20 2009
> New Revision: 88988
> 
> URL: http://llvm.org/viewvc/llvm-project?rev=88988&view=rev
> Log:
> Implement dynamic_cast<void*>(E).
> 
> Modified:
>    cfe/trunk/lib/CodeGen/CGCXXExpr.cpp
> 
> Modified: cfe/trunk/lib/CodeGen/CGCXXExpr.cpp
> URL: http://llvm.org/viewvc/llvm-project/cfe/trunk/lib/CodeGen/CGCXXExpr.cpp?rev=88988&r1=88987&r2=88988&view=diff
> 
> ==============================================================================
> --- cfe/trunk/lib/CodeGen/CGCXXExpr.cpp (original)
> +++ cfe/trunk/lib/CodeGen/CGCXXExpr.cpp Mon Nov 16 16:52:20 2009
> @@ -408,26 +408,14 @@
> llvm::Value *CodeGenFunction::EmitDynamicCast(llvm::Value *V,
>                                               const CXXDynamicCastExpr *DCE) {
>   QualType CastTy = DCE->getTypeAsWritten();
> +  QualType InnerType = CastTy->getPointeeType();
>   QualType ArgTy = DCE->getSubExpr()->getType();
>   const llvm::Type *LArgTy = ConvertType(ArgTy);
>   const llvm::Type *LTy = ConvertType(DCE->getType());
> -  CXXRecordDecl *SrcTy;
> -  CXXRecordDecl *DstTy;
> -  QualType Ty = CastTy.getTypePtr()->getPointeeType();
> -  CanQualType CanTy = CGM.getContext().getCanonicalType(Ty);
> -  Ty = CanTy.getUnqualifiedType();
> -  DstTy = cast<CXXRecordDecl>(Ty->getAs<RecordType>()->getDecl());
> -  Ty = ArgTy;
> -  if (ArgTy.getTypePtr()->isPointerType()
> -      || ArgTy.getTypePtr()->isReferenceType())
> -    Ty = Ty.getTypePtr()->getPointeeType();
> -  CanTy = CGM.getContext().getCanonicalType(Ty);
> -  Ty = CanTy.getUnqualifiedType();
> -  SrcTy = cast<CXXRecordDecl>(Ty->getAs<RecordType>()->getDecl());
> +
>   bool CanBeZero = false;
> -  bool ThrowOnBad = false;
>   bool ToVoid = false;
> -  QualType InnerType = CastTy->getPointeeType();
> +  bool ThrowOnBad = false;
>   if (CastTy->isPointerType()) {
>     // FIXME: if PointerType->hasAttr<NonNullAttr>(), we don't set this
>     CanBeZero = true;
> @@ -438,7 +426,14 @@
>     ThrowOnBad = true;
>   }
> 
> -  // FIXME: Add support for ToVoid
> +  CXXRecordDecl *SrcTy;
> +  QualType Ty = ArgTy;
> +  if (ArgTy.getTypePtr()->isPointerType()
> +      || ArgTy.getTypePtr()->isReferenceType())
> +    Ty = Ty.getTypePtr()->getPointeeType();
> +  CanQualType CanTy = CGM.getContext().getCanonicalType(Ty);
> +  Ty = CanTy.getUnqualifiedType();
> +  SrcTy = cast<CXXRecordDecl>(Ty->getAs<RecordType>()->getDecl());
> 
>   llvm::BasicBlock *ContBlock = createBasicBlock();
>   llvm::BasicBlock *NullBlock = 0;
> @@ -452,44 +447,62 @@
>     EmitBlock(NonZeroBlock);
>   }
> 
> +  llvm::BasicBlock *BadCastBlock = 0;
> 
> -  /// Call __dynamic_cast
> -  const llvm::Type *ResultType = llvm::Type::getInt8PtrTy(VMContext);
> -  const llvm::FunctionType *FTy;
> -  std::vector<const llvm::Type*> ArgTys;
> -  const llvm::Type *PtrToInt8Ty
> -    = llvm::Type::getInt8Ty(VMContext)->getPointerTo();
>   const llvm::Type *PtrDiffTy = ConvertType(getContext().getSizeType());
> -  ArgTys.push_back(PtrToInt8Ty);
> -  ArgTys.push_back(PtrToInt8Ty);
> -  ArgTys.push_back(PtrToInt8Ty);
> -  ArgTys.push_back(PtrDiffTy);
> -  FTy = llvm::FunctionType::get(ResultType, ArgTys, false);
> -
> -  // FIXME: Calculate better hint.
> -  llvm::Value *hint = llvm::ConstantInt::get(PtrDiffTy, -1ULL);
> -  llvm::Value *SrcArg = CGM.GenerateRttiRef(SrcTy);
> -  llvm::Value *DstArg = CGM.GenerateRttiRef(DstTy);
> -  V = Builder.CreateBitCast(V, PtrToInt8Ty);
> -  V = Builder.CreateCall4(CGM.CreateRuntimeFunction(FTy, "__dynamic_cast"),
> -                          V, SrcArg, DstArg, hint);
> -  V = Builder.CreateBitCast(V, LTy);
> -
> -  llvm::BasicBlock *BadCastBlock = 0;
> -  if (ThrowOnBad) {
> -    BadCastBlock = createBasicBlock();
> 
> -    llvm::Value *Zero = llvm::Constant::getNullValue(LTy);
> -    Builder.CreateCondBr(Builder.CreateICmpNE(V, Zero),
> -                         ContBlock, BadCastBlock);
> -    EmitBlock(BadCastBlock);
> -    /// Call __cxa_bad_cast
> -    ResultType = llvm::Type::getVoidTy(VMContext);
> -    const llvm::FunctionType *FBadTy;
> -    FTy = llvm::FunctionType::get(ResultType, false);
> -    llvm::Value *F = CGM.CreateRuntimeFunction(FBadTy, "__cxa_bad_cast");
> -    Builder.CreateCall(F)->setDoesNotReturn();
> -    // Builder.CreateUnreachable();
> +  // See if this is a dynamic_cast(void*)
> +  if (ToVoid) {
> +    llvm::Value *This = V;
> +    V = Builder.CreateBitCast(This, PtrDiffTy->getPointerTo()->getPointerTo());
> +    V = Builder.CreateLoad(V, "vtable");
> +    V = Builder.CreateConstInBoundsGEP1_64(V, -2ULL);
> +    V = Builder.CreateLoad(V, "offset to top");
> +    This = Builder.CreateBitCast(This, llvm::Type::getInt8PtrTy(VMContext));
> +    V = Builder.CreateInBoundsGEP(This, V);
> +    V = Builder.CreateBitCast(V, LTy);
> +  } else {
> +    /// Call __dynamic_cast
> +    const llvm::Type *ResultType = llvm::Type::getInt8PtrTy(VMContext);
> +    const llvm::FunctionType *FTy;
> +    std::vector<const llvm::Type*> ArgTys;
> +    const llvm::Type *PtrToInt8Ty
> +      = llvm::Type::getInt8Ty(VMContext)->getPointerTo();
> +    ArgTys.push_back(PtrToInt8Ty);
> +    ArgTys.push_back(PtrToInt8Ty);
> +    ArgTys.push_back(PtrToInt8Ty);
> +    ArgTys.push_back(PtrDiffTy);
> +    FTy = llvm::FunctionType::get(ResultType, ArgTys, false);
> +    CXXRecordDecl *DstTy;
> +    Ty = CastTy.getTypePtr()->getPointeeType();
> +    CanTy = CGM.getContext().getCanonicalType(Ty);
> +    Ty = CanTy.getUnqualifiedType();
> +    DstTy = cast<CXXRecordDecl>(Ty->getAs<RecordType>()->getDecl());
> +
> +    // FIXME: Calculate better hint.
> +    llvm::Value *hint = llvm::ConstantInt::get(PtrDiffTy, -1ULL);
> +    llvm::Value *SrcArg = CGM.GenerateRttiRef(SrcTy);
> +    llvm::Value *DstArg = CGM.GenerateRttiRef(DstTy);
> +    V = Builder.CreateBitCast(V, PtrToInt8Ty);
> +    V = Builder.CreateCall4(CGM.CreateRuntimeFunction(FTy, "__dynamic_cast"),
> +                            V, SrcArg, DstArg, hint);
> +    V = Builder.CreateBitCast(V, LTy);
> +
> +    if (ThrowOnBad) {
> +      BadCastBlock = createBasicBlock();
> +
> +      llvm::Value *Zero = llvm::Constant::getNullValue(LTy);
> +      Builder.CreateCondBr(Builder.CreateICmpNE(V, Zero),
> +                           ContBlock, BadCastBlock);
> +      EmitBlock(BadCastBlock);
> +      /// Call __cxa_bad_cast
> +      ResultType = llvm::Type::getVoidTy(VMContext);
> +      const llvm::FunctionType *FBadTy;
> +      FTy = llvm::FunctionType::get(ResultType, false);
> +      llvm::Value *F = CGM.CreateRuntimeFunction(FBadTy, "__cxa_bad_cast");
> +      Builder.CreateCall(F)->setDoesNotReturn();
> +      // Builder.CreateUnreachable();
> +    }
>   }
> 
>   if (CanBeZero) {
> 
> 
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