linux-kernel - Re: [PATCH 1/2] tools/nolibc: add stdarg.h header

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Date:   Wed, 30 Aug 2023 09:27:45 +0200
From:   Willy Tarreau <w@....eu>
To:     Thomas Weißschuh <linux@...ssschuh.net>
Cc:     Shuah Khan <shuah@...nel.org>, Zhangjin Wu <falcon@...ylab.org>,
        Yuan Tan <tanyuan@...ylab.org>, linux-kernel@...r.kernel.org,
        linux-kselftest@...r.kernel.org
Subject: Re: [PATCH 1/2] tools/nolibc: add stdarg.h header

On Sun, Aug 27, 2023 at 10:00:15AM +0200, Thomas Weißschuh wrote:
> This allows nolic to work with `-nostdinc` avoiding any reliance on
> system headers.
> 
> The implementation has been lifted from musl libc 1.2.4.
> There is already an implementation of stdarg.h in include/linux/stdarg.h
> but that is GPL licensed and therefore not suitable for nolibc.
> 
> The used compiler builtins have been validated to be at least available
> since GCC 4.1.2 and clang 3.0.0.
> 
> Signed-off-by: Thomas Weißschuh <linux@...ssschuh.net>
> ---
>  tools/include/nolibc/Makefile |  1 +
>  tools/include/nolibc/stdarg.h | 16 ++++++++++++++++
>  2 files changed, 17 insertions(+)
> 
> diff --git a/tools/include/nolibc/Makefile b/tools/include/nolibc/Makefile
> index 909b6eb500fe..e69c26abe1ea 100644
> --- a/tools/include/nolibc/Makefile
> +++ b/tools/include/nolibc/Makefile
> @@ -34,6 +34,7 @@ all_files := \
>  		signal.h \
>  		stackprotector.h \
>  		std.h \
> +		stdarg.h \
>  		stdint.h \
>  		stdlib.h \
>  		string.h \
> diff --git a/tools/include/nolibc/stdarg.h b/tools/include/nolibc/stdarg.h
> new file mode 100644
> index 000000000000..c628b5783da6
> --- /dev/null
> +++ b/tools/include/nolibc/stdarg.h
> @@ -0,0 +1,16 @@
> +/* SPDX-License-Identifier: LGPL-2.1 OR MIT */
> +/*
> + * Variadic argument support for NOLIBC
> + * Copyright (C) 2005-2020 Rich Felker, et al.
> + */
> +
> +#ifndef _NOLIBC_STDARG_H
> +#define _NOLIBC_STDARG_H
> +
> +typedef __builtin_va_list va_list;
> +#define va_start(v, l)   __builtin_va_start(v, l)
> +#define va_end(v)        __builtin_va_end(v)
> +#define va_arg(v, l)     __builtin_va_arg(v, l)
> +#define va_copy(d, s)    __builtin_va_copy(d, s)
> +
> +#endif /* _NOLIBC_STDARG_H */

Now with your other explanation I agree, however we need to change:

  #include <stdarg.h>

to

  #include "stdarg.h"

in stdio.h and sys.h so that we always use ours from now on.

Willy