[patch] Delay __fastcall attribute checking utnil after merging declarations

[Nico Weber]

(adding back cfe-commits, which I had accidentally dropped.)

On Thu, Jul 31, 2014 at 1:04 PM, Reid Kleckner <rnk at google.com> wrote:

> On Thu, Jul 31, 2014 at 11:16 AM, Nico Weber <thakis at chromium.org> wrote:
>
>> On Thu, Jul 31, 2014 at 9:45 AM, Nico Weber <thakis at chromium.org> wrote:
>>
>>>  Thanks!
>>>
>>> On Tue, Jul 29, 2014 at 10:40 AM, Reid Kleckner <rnk at google.com> wrote:
>>>
>>>> +  // Diagnose the use of X86 fastcall on unprototyped functions.
>>>>
>>>> We should also diagnose unprototyped stdcall functions, but I'm not
>>>> sure if that would be too disruptive.  Currently we accept this and always
>>>> call _f at 0:
>>>> void __stdcall f();
>>>> int main() {
>>>>   f(1);
>>>>   f(1, 2);
>>>>   f(1, 2, 3);
>>>> }
>>>>
>>>> MSVC rejects with "t.c(5) : error C2708: 'f' : actual parameters length
>>>> in bytes differs from previous call or reference".
>>>>
>>>
>>> I added a TODO for adding this and reshuffled the if to make this easy
>>> to add. I'll give it a try once this patch is in.
>>>
>>
>>
> Actually, should this happen for all isCalleeCleanup() calling
>> conventions? I suppose thiscall always has a prototype, but pascal(l :-P)
>> might not?
>>
>
> That sounds like the right predicate, considering we verifier-fail on this
> in plain C mode:
> void __thiscall f();
> int main() { f(1); }
>
> MSVC rejects __thiscall in C mode, but we don't.
>

I did give it a try, and rejecting stdcall fires on Windows SDK headers:

...win8sdk/Include/um\imm.h(432,13) :  error(clang): function with no
prototype cannot use stdcall calling convention
BOOL WINAPI ImmDisableLegacyIME();
            ^

So the same mechanism doesn't work for stdcall. We could do the same thing
for thiscall, but if msvc rejects that in C files, we should probably just
do that too?
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