linux-kernel - Re: [PATCH] lib/zlib: drop EQUAL macro

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Message-ID: <a80a05d3-beb5-4545-9a0d-c10efc9fe3a4@linux.ibm.com>
Date: Thu, 6 Feb 2025 18:53:17 +0100
From: Zaslonko Mikhail <zaslonko@...ux.ibm.com>
To: Yury Norov <yury.norov@...il.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Heiko Carstens <heiko.carstens@...ibm.com>,
        Ilya Leoshkevich <iii@...ux.ibm.com>,
        Sergey Senozhatsky <sergey.senozhatsky@...il.com>,
        linux-kernel@...r.kernel.org
Cc: Joe Perches <joe@...ches.com>
Subject: Re: [PATCH] lib/zlib: drop EQUAL macro

Hi Yury,

I think the initial idea was to keep the code similar to the userspace zlib for serviceability.
But since it leads to extra warnings, it's worth fixing.

Reviewed-by: Mikhail Zaslonko <zaslonko@...ux.ibm.com>

On 05.02.2025 22:29, Yury Norov wrote:
> The macro is pre-historic, and only exists to help those readers who
> don't know what memcmp() returns if memory areas differ. This is pretty
> well documented, so the macro looks excessive.
> 
> Now that the only user of the macro depends on DEBUG_ZLIB config, GCC
> warns about unused macro if the library is built with W=2 against
> defconfig. So drop it for good.
> 
> Signed-off-by: Yury Norov <yury.norov@...il.com>
> ---
> scripts/get_maintainer.pl failed to attribute this patch, so adding
> Andrew and recent active developers, and Joe Perches for the script.
> 
> $ scripts/get_maintainer.pl 0001-zlib-drop-EQUAL-macro.patch
> Bad divisor in main::vcs_assign: 0
> "GitAuthor: Yury Norov" <yury.norov@...il.com> (authored:1/1=100%,added_lines:1/1=100%,removed_lines:5/5=100%)
> linux-kernel@...r.kernel.org (open list)
> 
>  lib/zlib_deflate/deflate.c | 6 +-----
>  1 file changed, 1 insertion(+), 5 deletions(-)
> 
> diff --git a/lib/zlib_deflate/deflate.c b/lib/zlib_deflate/deflate.c
> index 3a1d8d34182e..8fb2a3e17c0e 100644
> --- a/lib/zlib_deflate/deflate.c
> +++ b/lib/zlib_deflate/deflate.c
> @@ -151,9 +151,6 @@ static const config configuration_table[10] = {
>   * meaning.
>   */
>  
> -#define EQUAL 0
> -/* result of memcmp for equal strings */
> -
>  /* ===========================================================================
>   * Update a hash value with the given input byte
>   * IN  assertion: all calls to UPDATE_HASH are made with consecutive
> @@ -713,8 +710,7 @@ static void check_match(
>  )
>  {
>      /* check that the match is indeed a match */
> -    if (memcmp((char *)s->window + match,
> -                (char *)s->window + start, length) != EQUAL) {
> +    if (memcmp((char *)s->window + match, (char *)s->window + start, length)) {
>          fprintf(stderr, " start %u, match %u, length %d\n",
>  		start, match, length);
>          do {