Re: [PATCH v2 0/5] linux: Avoid va_list for generic syscall wrappers if possible

[Xi Ruoyao <xry111@xry111.site>]

On Mon, 2023-03-27 at 10:04 -0400, Carlos O'Donell wrote:

> In summary, I think this is a compiler problem

Definitely true.

> and that working around this in glibc
> is going to result in:
> 
> - Odd corner case ABI issues between public declarations of variadic functions and
>   internal non-variadic definitions.
> 
> - Poorer testing of #else code that uses variadic arguments, as the public interface
>   requires.
> 
> I don't support going in this direction.

Valid reasons.  Abandon this series then.

But I hope these could be raised earlier (in the discussion about
LoongArch syscall.S) so I wouldn't write all the code :).

> Is there an alternative that could generate better code that doesn't go this way?

For LoongArch I can improve GCC to save only the GARs containing the
arguments really used in va_arg (i.e. one GAR for things like open() or
fcntl() instead of all 8 GARs), but I guess the patch will be delayed
into GCC 14.

Generally I've not got an idea about how to make GCC avoid saving GARs
unnecessarily with va_arg.

-- 
Xi Ruoyao <xry111@xry111.site>
School of Aerospace Science and Technology, Xidian University