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.

[Hans Wennborg via cfe-commits]

On Tue, Feb 23, 2016 at 11:12 AM, Aaron Ballman <aaron at aaronballman.com> wrote:
> 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!

r261684.


>> 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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