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Date: Fri, 12 Sep 2025 17:14:00 -0700 (PDT)
To: Christian Franke via Cygwin <cygwin@cygwin.com>
cc: Christian Franke <Christian.Franke@t-online.de>
Subject: Re: clang 20.1.8+21.1.1: __stdcall__ warning only from Cygwin version
In-Reply-To: <568c797f-19cf-6da1-cef4-480e3a64445f@jdrake.com>
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 <568c797f-19cf-6da1-cef4-480e3a64445f@jdrake.com>
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From: Jeremy Drake via Cygwin <cygwin@cygwin.com>
Reply-To: Jeremy Drake <cygwin@jdrake.com>
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On Fri, 12 Sep 2025, Jeremy Drake via Cygwin wrote:

> On Fri, 12 Sep 2025, Christian Franke via Cygwin wrote:
>
> > First of all: thanks for providing recent clang packages!
> >
> > Testcase:
> >
> > $ cat winapi.c
> > #include <windows.h>
> > int WINAPI SomeDllFunction(int, int, int, int, int);
> >
> > int call_it()
> > {
> >    return SomeDllFunction(1, 2, 3, 4, 5);
> > }
> >
> > $ clang -S winapi.c  # with 20.1.8 and 21.1.1
> > winapi.c:2:5: warning: '__stdcall__' calling convention is not supported
> > for this target
> >        [-Wignored-attributes]
> >      2 | int WINAPI SomeDllFunction(int, int, int, int, int);
> >        |     ^
> > /usr/include/w32api/minwindef.h:98:16: note: expanded from macro 'WINAPI'
> >     98 | #define WINAPI __stdcall
> >        |                ^
> > <built-in>:400:34: note: expanded from macro '__stdcall'
> >    400 | #define __stdcall __attribute__((__stdcall__))
> >        |                                  ^
> > 1 warning generated.
> >
>
> I was wondering about this one when trying to figure out what Windows
> behaviors should be enabled for Cygwin.  It is a fact that x86_64 doesn't
> support stdcall/thiscall/fastcall, but for Windows targets those calling
> conventions are silently ignored rather than warned about.
>
> Another thing that's got me confused in that vicinity is sysv_abi vs
> ms_abi calling convention attribute.  I think Cygwin defaults to ms_abi
> so should allow __attribute__((sysv_abi)) to override, but I think it
> would warn about that.

https://github.com/llvm/llvm-project/pull/158385 if you're interested in
following it.

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