[PATCH] Sema: Fix CheckReturnStackAddr when RetValExp is an explicit cast

[Chongyu Zhu]

Hi,

This is actually the same as http://lists.cs.uiuc.edu/pipermail/cfe-commits/Week-of-Mon-20131104/092692.html before I realized that I should use http://llvm-reviews.chandlerc.com to send patch for review.

Anyway, thanks for review :-)

Regards,
Chongyu Zhu

On Nov 9, 2013, at 12:32 PM, Chongyu Zhu <lembacon at gmail.com> wrote:

> I have found that `Sema::CheckReturnStackAddr` failed to generate warnings
> for `diag::warn_ret_stack_ref` and `diag::warn_ret_local_temp_ref` when the
> return value expression is an explicit cast.
> 
> Provided the following code,
> 
>> const int &test1()
>> {
>>  return 0;
>> }
>> 
>> const int &test2()
>> {
>>  int val = 0;
>>  return val;
>> }
>> 
>> const int &test3()
>> {
>>  return static_cast<const int &>(0);
>> }
>> 
>> const int &test4()
>> {
>>  int val = 0;
>>  return static_cast<const int &>(val);
>> }
> 
> Clang (as of r194251) generates warnings for `test1` and `test2`, however,
> no warnings are given for `test3` and `test4`.
> 
> GCC (4.8.1) is able to successfully generate warnings for all of the above.
> 
> http://llvm-reviews.chandlerc.com/D2132
> 
> Files:
>  lib/Sema/SemaChecking.cpp
> 
> Index: lib/Sema/SemaChecking.cpp
> ===================================================================
> --- lib/Sema/SemaChecking.cpp
> +++ lib/Sema/SemaChecking.cpp
> @@ -4192,10 +4192,17 @@
> 
>   E = E->IgnoreParens();
>   switch (E->getStmtClass()) {
> -  case Stmt::ImplicitCastExprClass: {
> -    ImplicitCastExpr *IE = cast<ImplicitCastExpr>(E);
> -    if (IE->getValueKind() == VK_LValue) {
> -      E = IE->getSubExpr();
> +  case Stmt::ImplicitCastExprClass:
> +  case Stmt::CStyleCastExprClass:
> +  case Stmt::CXXStaticCastExprClass:
> +  case Stmt::CXXDynamicCastExprClass:
> +  case Stmt::CXXReinterpretCastExprClass:
> +  case Stmt::CXXConstCastExprClass:
> +  case Stmt::CXXFunctionalCastExprClass:
> +  case Stmt::ObjCBridgedCastExprClass: {
> +    CastExpr *CE = cast<CastExpr>(E);
> +    if (CE->getValueKind() == VK_LValue) {
> +      E = CE->getSubExpr();
>       continue;
>     }
>     return NULL;
> <D2132.1.patch>