linux-kernel - Re: [PATCH] arch: x86: entry: vdso: fix type conversion on printf() call

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Date:   Tue, 15 Dec 2020 08:32:20 -0800
From:   Randy Dunlap <rdunlap@...radead.org>
To:     "Enrico Weigelt, metux IT consult" <info@...ux.net>,
        linux-kernel@...r.kernel.org
Cc:     luto@...nel.org, tglx@...utronix.de, mingo@...hat.com,
        bp@...en8.de, x86@...nel.org, hpa@...or.com
Subject: Re: [PATCH] arch: x86: entry: vdso: fix type conversion on printf()
 call

On 12/15/20 8:03 AM, Enrico Weigelt, metux IT consult wrote:
> Fixing the following compiler warning by explicit conversion to long:
> 
> In file included from /home/nekrad/src/apu2-dev/pkg/kernel.apu2.git/arch/x86/entry/vdso/vdso2c.c:162:0:
> /home/nekrad/src/apu2-dev/pkg/kernel.apu2.git/arch/x86/entry/vdso/vdso2c.h: In function 'extract64':
> /home/nekrad/src/apu2-dev/pkg/kernel.apu2.git/arch/x86/entry/vdso/vdso2c.h:38:52: warning: format '%lu' expects argument of type 'long unsigned int', but argument 4 has type 'size_t {aka unsigned int}' [-Wformat=]
>   fprintf(outfile, "static const unsigned char %s[%lu] = {", name, len);
>                                                     ^
>   CC      mm/filemap.o
> In file included from /home/nekrad/src/apu2-dev/pkg/kernel.apu2.git/arch/x86/entry/vdso/vdso2c.c:166:0:
> /home/nekrad/src/apu2-dev/pkg/kernel.apu2.git/arch/x86/entry/vdso/vdso2c.h: In function 'extract32':
> /home/nekrad/src/apu2-dev/pkg/kernel.apu2.git/arch/x86/entry/vdso/vdso2c.h:38:52: warning: format '%lu' expects argument of type 'long unsigned int', but argument 4 has type 'size_t {aka unsigned int}' [-Wformat=]
>   fprintf(outfile, "static const unsigned char %s[%lu] = {", name, len);
> 
> Signed-off-by: Enrico Weigelt, metux IT consult <info@...ux.net>
> ---
>  arch/x86/entry/vdso/vdso2c.h | 3 ++-
>  1 file changed, 2 insertions(+), 1 deletion(-)

Hi,

size_t is normally printed with %zu.
Is there some reason that isn't being used here?

> diff --git a/arch/x86/entry/vdso/vdso2c.h b/arch/x86/entry/vdso/vdso2c.h
> index 1c7cfac7e64a..5c6a4bbc63f9 100644
> --- a/arch/x86/entry/vdso/vdso2c.h
> +++ b/arch/x86/entry/vdso/vdso2c.h
> @@ -35,7 +35,8 @@ static void BITSFUNC(extract)(const unsigned char *data, size_t data_len,
>  	if (offset + len > data_len)
>  		fail("section to extract overruns input data");
>  
> -	fprintf(outfile, "static const unsigned char %s[%lu] = {", name, len);
> +	fprintf(outfile, "static const unsigned char %s[%lu] = {", name,
> +		(unsigned long)len);
>  	BITSFUNC(copy)(outfile, data + offset, len);
>  	fprintf(outfile, "\n};\n\n");
>  }
> 

thanks.
-- 
~Randy