[cfe-dev] Recent failing tests in libc++

[Marshall Clow via cfe-dev]

On Mon, May 28, 2018 at 2:29 PM, Richard Smith <richard at metafoo.co.uk>
wrote:

> Clang 5 implemented the originally adopted proposal. The behaviour you're
> referring to was introduced by P0620R0, which I think was not implemented
> until Clang 6.
>

That would explain what I'm seeing.


> Perhaps we should bump the deduction guides feature test macro version for
> that paper?
>

I don't see any mention of feature macros in P0620R0 :-(
Besides, I don't see how it will help now that clang 6 is out there.

-- Marshall




> On 28 May 2018 14:10, "Marshall Clow via cfe-dev" <cfe-dev at lists.llvm.org>
> wrote:
>
> On Mon, May 28, 2018 at 12:51 PM, Marshall Clow <mclow.lists at gmail.com>
> wrote:
>
>> This past week, I checked in a bunch of code (and tests) having to do
>> with the deduction guides features of C++17 - adding support for many of
>> the standard library types. Some of the tests started failing - mostly (but
>> not exclusively) on ARM. JF tried to fix some of the tests on Friday, but
>> was not completely successful.
>>
>> Today, I took a fresh look at the failures, and realized that all but one
>> of them were on bots that were running clang-5.  It appears that clang-5
>> has a bug where it mis-deduces the template arguments when it is handed
>> something that looks like a copy constructor. (Alternately, it implicitly
>> generates an incorrect template deduction guide and uses that.)
>>
>
> Another possible diagnosis is that clang-5 generates no implicit deduction
> guides - and only uses the explicitly provided ones.
>
> -- Marshall
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