[PATCH] MSVC 2013 type trait support

[Alp Toker]

On 17/01/2014 21:36, Richard Smith wrote:
> On Fri, Jan 17, 2014 at 6:52 AM, Alp Toker <alp at nuanti.com 
> <mailto:alp at nuanti.com>> wrote:
>
>     Ping
>
>     Need this to parse MSVC headers, patch rebased to ToT.
>
>
> Really sorry for the delay!
>
> For the 'nothrow' tests, please use Sema::canThrow rather than 
> checking the exception specification (that way, you'll also handle 
> exceptions within default arguments, exceptions within the conversion 
> sequences for the parameters, and so on).

On balance there's no need for bug-for-bug compatibility here so yes, 
let's do the right thing. The patch was developed from a description of 
MSVC behaviour but I've reached the conclusion they've simply made a 
pig's ear of it.

As a note, the MS built-in __has_*constructor() primitives only seem to 
check the first ctor in cases where there are multiple constructors 
defined -- another behaviour we certainly don't want.

Thanks for pointing this out!

> Please also *don't* return true if the construction is trivial but not 
> noexcept -- that doesn't match what the standard requires from these 
> traits.
>
> If you're intending on providing follow-up patches implementing the 
> other stubbed-out traits, I'm OK with them being broken in the interim 
> (it's a good start); otherwise I'd like for them to be diagnosed 
> rather than silently giving the wrong answers.

It's worth getting these into SVN to stem bug reports -- failure to 
parse is the most reported issue. So I'll land with the 
__is_*constructive() checks as KEYALL now that it looks like the 
semantics will be generally useful, and keep the unimplemented cases as 
KEYMS with a view to completing their implementations shortly.

Richard, if you have a minute could you review my proposal "Type trait 
primitives and feature detection" taking into account r199562 -- that's 
the roadmap I've set out for getting trait feature detection and 
documentation back in order and I'd appreciate your second opinion.

Alp.


>
> On 12/12/2013 17:13, Alp Toker wrote:
>
>         This patch adds support for the MSVC12.0 / 2013 type trait
>         builtin primitives sufficiently to support the new type_trait
>         facilities added to the C++ standard library.
>
>         With these clang is now more or less able to parse itself with
>         the Visual Studio 2013 SDK.
>
>         Fully Implemented:
>
>         * __is_constructible()
>         * __is_nothrow_constructible()
>
>         Implemented through fallback to other type traits (WIP, noted
>         with two TODOs):
>
>         * __is_destructible()
>         * __is_nothrow_destructible()
>         * __is_nothrow_assignable()
>
>         The patch is built on top of the other two posted earlier
>         today unifying (1) contextual keywords and (2) the new type
>         traits implementation.
>
>         Alp.
>
>
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