linux-kernel - Re: [PATCH v2 12/13] tools/nolibc: add __nolibc_static

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Message-ID: <20251130110856.GE31522@1wt.eu>
Date: Sun, 30 Nov 2025 12:08:56 +0100
From: Willy Tarreau <w@....eu>
To: Thomas Weißschuh <linux@...ssschuh.net>
Cc: Shuah Khan <shuah@...nel.org>, Arnd Bergmann <arnd@...db.de>,
        linux-kernel@...r.kernel.org, linux-kselftest@...r.kernel.org
Subject: Re: [PATCH v2 12/13] tools/nolibc: add __nolibc_static_assert()

On Sat, Nov 22, 2025 at 05:59:18PM +0100, Thomas Weißschuh wrote:
> Add a wrapper for _Static_assert() to use within nolibc.
> While _Static_assert() itself was only standardized in C11,
> in GCC and clang dialects it is also available in older standards.
> 
> If it turns out that _Static_assert can't be used in some contexts,
> this wrapper can be adapted.
> 
> Signed-off-by: Thomas Weißschuh <linux@...ssschuh.net>
> ---
>  tools/include/nolibc/compiler.h | 2 ++
>  1 file changed, 2 insertions(+)
> 
> diff --git a/tools/include/nolibc/compiler.h b/tools/include/nolibc/compiler.h
> index 87090bbc53e0..ef247e916552 100644
> --- a/tools/include/nolibc/compiler.h
> +++ b/tools/include/nolibc/compiler.h
> @@ -47,4 +47,6 @@
>  #  define __nolibc_fallthrough do { } while (0)
>  #endif /* __nolibc_has_attribute(fallthrough) */
>  
> +#define __nolibc_static_assert(_t) _Static_assert(_t, "")

I'm not super fan of raising the bar to adoption by introducing forced
C11-isms, especially when they're only used to perform extra safety
checks that likely remain fine after you've checked them once. What
about instead:

+#if __STDC_VERSION__ >= 201112L
+# define __nolibc_static_assert(_t) _Static_assert(_t, "")
+#endif
+# define __nolibc_static_assert(_t) do { } while (0)
+#else

Note that this won't work out of code blocks but we very likely don't
care. And if we'd care, we could always switch to __asm__("") which
works everywhere.
 
What do you think ?

Thanks,
Willy