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Date: Fri, 12 Sep 2025 11:07:45 -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
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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, 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.

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