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

[Reid Kleckner]

On Thu, Aug 29, 2013 at 3:09 PM, Charles Davis <cdavis5x at gmail.com> wrote:

>
> On Aug 29, 2013, at 11:32 AM, Reid Kleckner wrote:
>
> 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.
>
> You mean, like this?
>
> There's one side effect of your suggested change that still bugs me,
> though. Now, if we're on a target that uses the SysV calling convention,
> the diagnostics always say "cdecl", even if the function was explicitly
> declared "sysv_abi". (Same with Windows and "ms_abi".) This might be
> slightly confusing to your average user, but for obvious reasons I don't
> want to add special cases to the places these diagnostics get printed.
>

I think the right way to handle this is to build AttributedType nodes for
the no-op attribute, but let equivalent and modified types be the same.
 The type printer should use __attribute__((sysv_abi/ms_abi)).  Looking at
SemaType, it's not clear if this happens.

Can you write a test for the bad case with a FIXME maybe?
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