[scan-build] fix warnings emitted on Clang CodeGen code base

[apelete]

Summary

Fix "Logic error" warnings of the type "Called c++ object pointer is
null" reported by Clang Static Analyzer on the following files:

• lib/CodeGen/CGDebugInfo.cpp,
• lib/CodeGen/CodeGenModule.cpp.

Signed-off-by: Apelete Seketeli <[e-mail]>

[dblaikie]

lib/CodeGen/CGDebugInfo.cpp

1317

It looks like this assertion could actually be a different assertion a little higher up.

For 'V' to be non-null, one of the if/else if chain above must fire.

So change the last else if to an else, and the dyn_cast to a cast, and the cast will fail an internal assertion if it's not valid (& the analyzer can easily then see that at least one of the assignments to V happens - whether or not the analyzer assumes that all the initializers of V are non-null, that's a separate issue...)

lib/CodeGen/CodeGenModule.cpp

2302

Again, a bit confused about whether you're proposing fixing nearly every pointer parameter in Clang and LLVM to assert non-null... I think we'd need a discussion about what that looks like.

[apelete]

lib/CodeGen/CGDebugInfo.cpp

1317

I do not understand what you are suggesting here.
Are you suggesting I should try those changes and see for myself that at least one of the assignments to V actually happens (which would mean that the warning is a false positive), or are you suggesting that the right way to fix it is to remove the assert and replace the last 'else if' construct with an 'else' ?

lib/CodeGen/CodeGenModule.cpp

2302

Sorry my intentions were not clear.
The only function pointer parameters I'm asserting are the ones that trigger a warning when running scan-build.
This might not be the right way to fix the issue, I will be waiting for you advice in that case (please have a look at my reply to your concern on the mailing list).

lib/CodeGen/CGDebugInfo.cpp

case TemplateArgument::Declaration: {
         // These five lines (& possibly the above member function pointer
         // handling) might be able to be refactored to use similar code in
         // CodeGenModule::getMemberPointerConstant
         uint64_t fieldOffset = CGM.getContext().getFieldOffset(D);
         CharUnits chars =
             CGM.getContext().toCharUnitsFromBits((int64_t)fieldOffset);
         V = CGM.getCXXABI().EmitMemberDataPointer(MPT, chars);
       }
+      assert(V && "constant must be not NULL at this point");
       TemplateParams.push_back(DBuilder.createTemplateValueParameter(
           TheCU, Name, TTy,
           cast_or_null<llvm::Constant>(V->stripPointerCasts())));
     } break;
     case TemplateArgument::NullPtr: {
       QualType T = TA.getNullPtrType();
       llvm::DIType *TTy = getOrCreateType(T, Unit);
       llvm::Constant *V = nullptr;

lib/CodeGen/CodeGenModule.cpp

 
 CharUnits CodeGenModule::GetTargetTypeStoreSize(llvm::Type *Ty) const {
   return Context.toCharUnitsFromBits(
       getDataLayout().getTypeStoreSizeInBits(Ty));
 }
 
 unsigned CodeGenModule::GetGlobalVarAddressSpace(const VarDecl *D,
                                                  unsigned AddrSpace) {
+  assert(D && "variable declaration must be not NULL");
   if (LangOpts.CUDA && LangOpts.CUDAIsDevice) {
     if (D->hasAttr<CUDAConstantAttr>())
       AddrSpace = getContext().getTargetAddressSpace(LangAS::cuda_constant);
     else if (D->hasAttr<CUDASharedAttr>())
       AddrSpace = getContext().getTargetAddressSpace(LangAS::cuda_shared);
     else
       AddrSpace = getContext().getTargetAddressSpace(LangAS::cuda_device);
   }