linux-kernel - Re: [PATCH -next] selftests/mm: mseal, self_elf: Fix warning comparing pointer to 0

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Message-Id: <20240717204616.7a3d2465272d4f8fd1736831@linux-foundation.org>
Date: Wed, 17 Jul 2024 20:46:16 -0700
From: Andrew Morton <akpm@...ux-foundation.org>
To: Jiapeng Chong <jiapeng.chong@...ux.alibaba.com>
Cc: shuah@...nel.org, linux-mm@...ck.org, linux-kselftest@...r.kernel.org,
 linux-kernel@...r.kernel.org, Abaci Robot <abaci@...ux.alibaba.com>
Subject: Re: [PATCH -next] selftests/mm: mseal, self_elf: Fix warning
 comparing pointer to 0

On Thu, 18 Jul 2024 11:10:39 +0800 Jiapeng Chong <jiapeng.chong@...ux.alibaba.com> wrote:

> Avoid pointer type value compared with 0 to make code clear.
> 
> ./tools/testing/selftests/mm/mseal_test.c:486:27-28: WARNING comparing pointer to 0.
> ./tools/testing/selftests/mm/mseal_test.c:1399:29-30: WARNING comparing pointer to 0.
> 
> ...
>
> --- a/tools/testing/selftests/mm/mseal_test.c
> +++ b/tools/testing/selftests/mm/mseal_test.c
> @@ -481,9 +481,8 @@ static void test_seal_zero_address(void)
>  	int prot;
>  
>  	/* use mmap to change protection. */
> -	ptr = sys_mmap(0, size, PROT_NONE,
> -			MAP_ANONYMOUS | MAP_PRIVATE | MAP_FIXED, -1, 0);
> -	FAIL_TEST_IF_FALSE(ptr == 0);
> +	ptr = sys_mmap(0, size, PROT_NONE, MAP_ANONYMOUS | MAP_PRIVATE | MAP_FIXED, -1, 0);
> +	FAIL_TEST_IF_FALSE(!ptr);
> @@ -1390,13 +1389,12 @@ static void test_seal_mremap_move_fixed_zero(bool seal)
>  	/*
>  	 * MREMAP_FIXED can move the mapping to zero address
>  	 */
> -	ret2 = mremap(ptr, size, 2 * page_size, MREMAP_MAYMOVE | MREMAP_FIXED,
> -			0);
> +	ret2 = mremap(ptr, size, 2 * page_size, MREMAP_MAYMOVE | MREMAP_FIXED, 0);

The author of this code chose to make it tractable in an 80-column
display.  It's best not to change that, without explanation.