[PATCH] Bug 14984 - Implement __attribute__((ms_abi))

[Reid Kleckner]

I think the lesson of CC_Default vs. CC_C is that there are *far* too many
places to check for calling convention compatibility, and that it's much
better to use a single representation for equivalent conventions.

Therefore, I'd remove areCCsCompatible() and let
TargetInfo::checkCallingConvention() adjust the the sysv or MS CCs to CC_C
when appropriate.

This way, when you target x64 Windows, the ms_abi attr will show up in the
AST, but it will produce function types that are nicely canonically
equivalent to normal function types.  Similarly, sysv_abi will be a no-op
on sysv targets.


On Wed, Aug 28, 2013 at 9:40 PM, Charles Davis <cdavis5x at gmail.com> wrote:

>
> On Aug 19, 2013, at 3:15 PM, Charles Davis wrote:
>
>
> On Aug 19, 2013, at 2:06 PM, Reid Kleckner wrote:
>
> On Thu, Jul 25, 2013 at 7:27 PM, Charles Davis <cdavis5x at gmail.com> wrote:
>
>> Actually, it's whatever the default calling convention is. Normally,
>> that's __cdecl, unless you pass -mrtd; then it's __stdcall. It's still
>> ignored on i386; it's just that gcc won't warn on it anymore (for some
>> reason). I haven't been able to find anything in their Bugzilla about it.
>> (This is at least true on 4.7, but I really don't feel like building 4.8 to
>> find out if that's changed. It took all day just for the computer running
>> Linux to build 4.7 so I could verify this for you. ;)
>>
>> The question is, since it has no effect on any platform except x86-64,
>> should *we* warn about it? I think we should.
>>
>> I have a new patch, but I need to test it first. I'm also tired. I'll
>> have it for you tomorrow morning (hopefully).
>>
>
>  Any news on this front?
>
> Yeah, but it's bad news.
>
> I haven't yet been able to figure out how to make Clang think cdecl is
> compatible with whatever calling convention (ms_abi or sysv_abi) is the
> default without breaking a bunch of other stuff. I was waiting for your
> CC_Default patch to go in, because I was hoping that would make it easier.
>
> Maybe it would just be easier for now to do what GCC does, and just
> declare that cdecl is compatible with both no matter which target we're
> targeting.
>
> Since I've had no luck working on this, I've had this set aside for now.
> I'll attach what I've got for now, but (since you're still busy with the
> CC_Default patch) I don't imagine you'll have a lot of time to work on
> this. I'll see if I can make this work in the meantime.
>
> Now that your CC_Default patch is in, I've had better luck.
>
> This patch passes all the tests I added. PTAL.
>
> Chip
>
>
>
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