linux-kernel - Re: [PATCH 4/4] tools/nolibc: add missing memchr() to string.h

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Message-ID: <d7b81639-c53c-4186-9e30-04137576a1f1@t-8ch.de>
Date: Sat, 21 Jun 2025 10:27:11 +0200
From: Thomas Weißschuh <thomas@...ch.de>
To: Willy Tarreau <w@....eu>
Cc: Thomas Weißschuh <thomas.weissschuh@...utronix.de>, 
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH 4/4] tools/nolibc: add missing memchr() to string.h

On 2025-06-20 12:02:51+0200, Willy Tarreau wrote:
> Surprisingly we forgot to add this common one. It was added with a
> per-arch guard allowing to later implement it in arch-specific asm
> code like was done for a few other ones.
> 
> The test verifies that we don't search past the indicated length.
> 
> Signed-off-by: Willy Tarreau <w@....eu>
> ---
>  tools/include/nolibc/string.h                | 15 +++++++++++++++
>  tools/testing/selftests/nolibc/nolibc-test.c |  2 ++
>  2 files changed, 17 insertions(+)
> 
> diff --git a/tools/include/nolibc/string.h b/tools/include/nolibc/string.h
> index 163a17e7dd38b..4000926f44ac4 100644
> --- a/tools/include/nolibc/string.h
> +++ b/tools/include/nolibc/string.h
> @@ -93,6 +93,21 @@ void *memset(void *dst, int b, size_t len)
>  }
>  #endif /* #ifndef NOLIBC_ARCH_HAS_MEMSET */
>  
> +#ifndef NOLIBC_ARCH_HAS_MEMCHR

So far we only have added these guards when necessary,
which they aren't here. Can we drop them?

> +static __attribute__((unused))
> +void *memchr(const void *s, int c, size_t len)
> +{
> +	char *p = (char *)s;

The docs say that they are interpreted as "unsigned char".
Also, can we keep the const?

> +
> +	while (len--) {
> +		if (*p == (char)c)
> +			return p;
> +		p++;
> +	}
> +	return NULL;
> +}
> +#endif /* #ifndef NOLIBC_ARCH_HAS_MEMCHR */
> +
>  static __attribute__((unused))
>  char *strchr(const char *s, int c)
>  {

<snip>