linux-kernel - Re: [PATCH] perf tools: fix type mismatch

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Date:	Mon, 15 Sep 2014 16:52:01 -0300
From:	Arnaldo Carvalho de Melo <acme@...hat.com>
To:	Alexey Brodkin <Alexey.Brodkin@...opsys.com>
Cc:	linux-kernel@...r.kernel.org,
	Vineet Gupta <Vineet.Gupta1@...opsys.com>,
	Borislav Petkov <bp@...e.de>, Jiri Olsa <jolsa@...nel.org>,
	Cody P Schafer <dev@...yps.com>,
	Arnaldo Carvalho de Melo <acme@...nel.org>
Subject: Re: [PATCH] perf tools: fix type mismatch - long vs __statfs_word

Em Wed, Aug 13, 2014 at 09:03:49PM +0400, Alexey Brodkin escreveu:
> >From "include/uapi/asm-generic/statfs.h" it is seen that "statfs.f_type" is of
> type "__statfs_word" which in its turn is "__u32" (unsigned int) for 32-bit
> systems.
> 
> So in case of compilation with "-Werror" following breakage happens:
> --->---
> fs.c: In function ‘fs__valid_mount’:
> fs.c:76:24: error: comparison between signed and unsigned integer expressions [-Werror=sign-compare]
>   else if (st_fs.f_type != magic)
>                         ^
> cc1: all warnings being treated as errors
> --->---
> 
> Note that now when fs.c is in "lib/api/fs" and in "tools/lib/api/Makefile"
> CFLAGS has hard-coded "-Werror" this is inevitable even if one builds "perf"
> with "WERROR=0".

So we have one more case of comparision involving f_type:

[acme@zoo linux]$ find tools/ -type f | xargs grep -w f_type
tools/lib/api/fs/fs.c:	else if (st_fs.f_type != magic)
tools/lib/api/fs/debugfs.c:	else if (st_fs.f_type != (long) DEBUGFS_MAGIC)
[acme@zoo linux]$

Do we have to apply the same fix to that other case as well?
Interestingly it does it on a different way, that by your description
above would make it fail on 32-bit systems, no?

- Arnaldo
 
> Signed-off-by: Alexey Brodkin <abrodkin@...opsys.com>
> 
> Cc: Vineet Gupta <vgupta@...opsys.com>
> Cc: Borislav Petkov <bp@...e.de>
> Cc: Jiri Olsa <jolsa@...nel.org>
> Cc: Cody P Schafer <dev@...yps.com>
> Cc: Arnaldo Carvalho de Melo <acme@...hat.com>
> ---
>  tools/lib/api/fs/fs.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/tools/lib/api/fs/fs.c b/tools/lib/api/fs/fs.c
> index c1b49c3..4b2fa7b 100644
> --- a/tools/lib/api/fs/fs.c
> +++ b/tools/lib/api/fs/fs.c
> @@ -75,7 +75,7 @@ static int fs__valid_mount(const char *fs, long magic)
>  
>  	if (statfs(fs, &st_fs) < 0)
>  		return -ENOENT;
> -	else if (st_fs.f_type != magic)
> +	else if ((long)st_fs.f_type != magic)
>  		return -ENOENT;
>  
>  	return 0;
> -- 
> 1.9.3
--
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