r208062 - Fix crash when one overload candidate is a template instead of a function. Patch by Kaelyn Takata.

[Richard Smith]

On Tue, May 6, 2014 at 12:16 PM, Kaelyn Takata <rikka at google.com> wrote:

> On Tue, May 6, 2014 at 12:02 AM, Richard Smith <richard at metafoo.co.uk>wrote:
>
>> On Mon, May 5, 2014 at 11:35 PM, Nick Lewycky <nicholas at mxc.ca> wrote:
>>
>>> Author: nicholas
>>> Date: Tue May  6 01:35:27 2014
>>> New Revision: 208062
>>>
>>> URL: http://llvm.org/viewvc/llvm-project?rev=208062&view=rev
>>> Log:
>>> Fix crash when one overload candidate is a template instead of a
>>> function. Patch by Kaelyn Takata.
>>>
>>> Testcase coming out of creduce will land in a separate commit shortly.
>>>
>>> Also, it appears that this callback is used even in a SFINAE context
>>> where the results are never displayed.
>>>
>>> Modified:
>>>     cfe/trunk/lib/Sema/SemaOverload.cpp
>>>
>>> Modified: cfe/trunk/lib/Sema/SemaOverload.cpp
>>> URL:
>>> http://llvm.org/viewvc/llvm-project/cfe/trunk/lib/Sema/SemaOverload.cpp?rev=208062&r1=208061&r2=208062&view=diff
>>>
>>> ==============================================================================
>>> --- cfe/trunk/lib/Sema/SemaOverload.cpp (original)
>>> +++ cfe/trunk/lib/Sema/SemaOverload.cpp Tue May  6 01:35:27 2014
>>> @@ -9260,6 +9260,7 @@ struct CompareOverloadCandidatesForDispl
>>>            L->FailureKind == ovl_fail_too_few_arguments) {
>>>          if (R->FailureKind == ovl_fail_too_many_arguments ||
>>>              R->FailureKind == ovl_fail_too_few_arguments) {
>>> +          if (!L->Function || !R->Function) return !R->Function;
>>>
>>
>> What happens if !L->Function && !R->Function? Is this a strict weak order?
>>
>
> If  !L->Function && !R->Function then L will be ordered before R. This
> isn't a strict weak order in that if you transpose L and R then the
> original R would be ordered before the original L, but that was true prior
> to my adding the parameter-count based sorting (when false was always
> returned for L if it had too few or too many arguments, regardless of what
> R was).
>

If this isn't a strict weak ordering, we have a bug: we're passing this as
the comparator to std::sort.

           int LDist = std::abs((int)L->Function->getNumParams() -
>>> (int)NumArgs);
>>>            int RDist = std::abs((int)R->Function->getNumParams() -
>>> (int)NumArgs);
>>>            if (LDist == RDist)
>>>
>>>
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>>
>>
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