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

[Chongyu Zhu]

Ping.
On Nov 9, 2013, at 12:37 PM, Chongyu Zhu <lembacon at gmail.com> wrote:

> 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>
>