r261669 - Amends r252104 to evaluate the controlling expression in an unevaluated context. This eliminates false-positive diagnostics about null pointer dereferences (etc) in the controlling expression.

[Aaron Ballman via cfe-commits]

On Tue, Feb 23, 2016 at 2:03 PM, Hans Wennborg <hans at chromium.org> wrote:
> Hi Aaron,
>
> I'll let it sit in the tree for a bit, and will then merge it later today.

Sounds great, thank you!

~Aaron

>
> Many thanks,
> Hans
>
> On Tue, Feb 23, 2016 at 11:01 AM, Aaron Ballman <aaron at aaronballman.com> wrote:
>> Hans, this should be safe to merge into 3.8 (as Richard had mentioned
>> in the review thread). Can you do the merge magic on my behalf?
>>
>> Thanks!
>>
>> ~Aaron
>>
>> On Tue, Feb 23, 2016 at 1:55 PM, Aaron Ballman via cfe-commits
>> <cfe-commits at lists.llvm.org> wrote:
>>> Author: aaronballman
>>> Date: Tue Feb 23 12:55:15 2016
>>> New Revision: 261669
>>>
>>> URL: http://llvm.org/viewvc/llvm-project?rev=261669&view=rev
>>> Log:
>>> Amends r252104 to evaluate the controlling expression in an unevaluated context. This eliminates false-positive diagnostics about null pointer dereferences (etc) in the controlling expression.
>>>
>>> Modified:
>>>     cfe/trunk/lib/Sema/SemaExpr.cpp
>>>     cfe/trunk/test/Sema/generic-selection.c
>>>
>>> Modified: cfe/trunk/lib/Sema/SemaExpr.cpp
>>> URL: http://llvm.org/viewvc/llvm-project/cfe/trunk/lib/Sema/SemaExpr.cpp?rev=261669&r1=261668&r2=261669&view=diff
>>> ==============================================================================
>>> --- cfe/trunk/lib/Sema/SemaExpr.cpp (original)
>>> +++ cfe/trunk/lib/Sema/SemaExpr.cpp Tue Feb 23 12:55:15 2016
>>> @@ -1373,10 +1373,13 @@ Sema::CreateGenericSelectionExpr(SourceL
>>>
>>>    // Decay and strip qualifiers for the controlling expression type, and handle
>>>    // placeholder type replacement. See committee discussion from WG14 DR423.
>>> -  ExprResult R = DefaultFunctionArrayLvalueConversion(ControllingExpr);
>>> -  if (R.isInvalid())
>>> -    return ExprError();
>>> -  ControllingExpr = R.get();
>>> +  {
>>> +    EnterExpressionEvaluationContext Unevaluated(*this, Sema::Unevaluated);
>>> +    ExprResult R = DefaultFunctionArrayLvalueConversion(ControllingExpr);
>>> +    if (R.isInvalid())
>>> +      return ExprError();
>>> +    ControllingExpr = R.get();
>>> +  }
>>>
>>>    // The controlling expression is an unevaluated operand, so side effects are
>>>    // likely unintended.
>>>
>>> Modified: cfe/trunk/test/Sema/generic-selection.c
>>> URL: http://llvm.org/viewvc/llvm-project/cfe/trunk/test/Sema/generic-selection.c?rev=261669&r1=261668&r2=261669&view=diff
>>> ==============================================================================
>>> --- cfe/trunk/test/Sema/generic-selection.c (original)
>>> +++ cfe/trunk/test/Sema/generic-selection.c Tue Feb 23 12:55:15 2016
>>> @@ -31,4 +31,8 @@ void foo(int n) {
>>>
>>>    const int i = 12;
>>>    int a9[_Generic(i, int: 1, default: 2) == 1 ? 1 : -1];
>>> +
>>> +  // This is expected to not trigger any diagnostics because the controlling
>>> +  // expression is not evaluated.
>>> +  (void)_Generic(*(int *)0, int: 1);
>>>  }
>>>
>>>
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