linux-kernel - Re: [PATCH] selftests/vDSO: Fix assignment in condition without parentheses

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Date: Tue, 30 Apr 2024 00:17:46 +0000
From: Justin Stitt <justinstitt@...gle.com>
To: Edward Liaw <edliaw@...gle.com>
Cc: linux-kernel@...r.kernel.org, Shuah Khan <shuah@...nel.org>, 
	Nathan Chancellor <nathan@...nel.org>, Nick Desaulniers <ndesaulniers@...gle.com>, 
	Bill Wendling <morbo@...gle.com>, "H. Peter Anvin" <hpa@...ux.intel.com>, 
	Andy Lutomirski <luto@....edu>, linux-kselftest@...r.kernel.org, kernel-team@...roid.com, 
	llvm@...ts.linux.dev
Subject: Re: [PATCH] selftests/vDSO: Fix assignment in condition without
 parentheses

On Mon, Apr 29, 2024 at 08:34:36PM +0000, Edward Liaw wrote:
> Fixes clang compiler warnings by adding parentheses:
> 
> parse_vdso.c:65:9: warning: using the result of an assignment as a condition without parentheses [-Wparentheses]
>                 if (g = h & 0xf0000000)
>                     ~~^~~~~~~~~~~~~~~~
> parse_vdso.c:65:9: note: place parentheses around the assignment to silence this warning
>                 if (g = h & 0xf0000000)
>                       ^
>                     (                 )
> parse_vdso.c:65:9: note: use '==' to turn this assignment into an equality comparison
>                 if (g = h & 0xf0000000)
>                       ^
>                       ==
> 
> Fixes: 98eedc3a9dbf ("Document the vDSO and add a reference parser")
> Signed-off-by: Edward Liaw <edliaw@...gle.com>

For readability's sake, I tend to prefer just taking the assignment out
of the if statement:

g = h & 0xf0000000;
then testing it:
if (g) ...

but as it stands it's fine and the warning goes away.

Reviewed-by: Justin Stitt <justinstitt@...gle.com>
> ---
>  tools/testing/selftests/vDSO/parse_vdso.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/tools/testing/selftests/vDSO/parse_vdso.c b/tools/testing/selftests/vDSO/parse_vdso.c
> index 413f75620a35..b9cf771006da 100644
> --- a/tools/testing/selftests/vDSO/parse_vdso.c
> +++ b/tools/testing/selftests/vDSO/parse_vdso.c
> @@ -62,7 +62,7 @@ static unsigned long elf_hash(const unsigned char *name)
>  	while (*name)
>  	{
>  		h = (h << 4) + *name++;
> -		if (g = h & 0xf0000000)
> +		if ((g = h & 0xf0000000))
>  			h ^= g >> 24;
>  		h &= ~g;
>  	}
> -- 
> 2.44.0.769.g3c40516874-goog
>