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

[caiyinyu <caiyinyu@loongson.cn>]

在 2023/3/27 下午10:45, Xi Ruoyao 写道:
> 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.

So I believe that the assembly implementation of syscalls is still 
necessary, especially for users who are using GCC<=13.

patch:

https://sourceware.org/pipermail/libc-alpha/2023-March/146588.html

>