[PATCH v2] selftest/mm: fix pointer comparison in mremap_test

[PATCH v2] selftest/mm: fix pointer comparison in mremap_test

[Ankit Khushwaha]

Pointer arthemitic with 'void * addr' and 'ulong dest_alignment'
triggers following warning:

mremap_test.c:1035:31: warning: pointer comparison always evaluates to
false [-Wtautological-compare]
 1035 |                 if (addr + c.dest_alignment < addr) {
      |                                             ^

this warning is raised from clang version 20.1.8 (Fedora 20.1.8-4.fc42).

use 'void *tmp_addr' to do the pointer arthemitic.

Signed-off-by: Ankit Khushwaha <ankitkhushwaha.linux@gmail.com>
---
Changelog:
v2:
- use 'void *tmp_addr' for pointer arthemitic instead of typecasting
'addr' to 'unsigned long long' as suggested by Andrew.

v1: https://lore.kernel.org/linux-kselftest/20251106104917.39890-1-ankitkhushwaha.linux@gmail.com/
---
 tools/testing/selftests/mm/mremap_test.c | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/tools/testing/selftests/mm/mremap_test.c b/tools/testing/selftests/mm/mremap_test.c
index a95c0663a011..308576437228 100644
--- a/tools/testing/selftests/mm/mremap_test.c
+++ b/tools/testing/selftests/mm/mremap_test.c
@@ -994,7 +994,7 @@ static void mremap_move_multi_invalid_vmas(FILE *maps_fp, unsigned long page_siz
 static long long remap_region(struct config c, unsigned int threshold_mb,
 			      char *rand_addr)
 {
-	void *addr, *src_addr, *dest_addr, *dest_preamble_addr = NULL;
+	void *addr, *tmp_addr, *src_addr, *dest_addr, *dest_preamble_addr = NULL;
 	unsigned long long t, d;
 	struct timespec t_start = {0, 0}, t_end = {0, 0};
 	long long  start_ns, end_ns, align_mask, ret, offset;
@@ -1032,7 +1032,8 @@ static long long remap_region(struct config c, unsigned int threshold_mb,
 	/* Don't destroy existing mappings unless expected to overlap */
 	while (!is_remap_region_valid(addr, c.region_size) && !c.overlapping) {
 		/* Check for unsigned overflow */
-		if (addr + c.dest_alignment < addr) {
+		tmp_addr = addr + c.dest_alignment;
+		if (tmp_addr < addr) {
 			ksft_print_msg("Couldn't find a valid region to remap to\n");
 			ret = -1;
 			goto clean_up_src;
--
2.51.1

Re: [PATCH v2] selftest/mm: fix pointer comparison in mremap_test

[David Hildenbrand (Red Hat)]

On 08.11.25 17:18, Ankit Khushwaha wrote:
> Pointer arthemitic with 'void * addr' and 'ulong dest_alignment'
> triggers following warning:
> 
> mremap_test.c:1035:31: warning: pointer comparison always evaluates to
> false [-Wtautological-compare]
>   1035 |                 if (addr + c.dest_alignment < addr) {
>        |                                             ^
> 
> this warning is raised from clang version 20.1.8 (Fedora 20.1.8-4.fc42).
> 
> use 'void *tmp_addr' to do the pointer arthemitic.
> 
> Signed-off-by: Ankit Khushwaha <ankitkhushwaha.linux@gmail.com>
> ---

Acked-by: David Hildenbrand (Red Hat) <david@kernel.org>

-- 
Cheers

David

Re: [PATCH v2] selftest/mm: fix pointer comparison in mremap_test

[Mike Rapoport]

On Sat, Nov 08, 2025 at 09:48:29PM +0530, Ankit Khushwaha wrote:
> Pointer arthemitic with 'void * addr' and 'ulong dest_alignment'
> triggers following warning:
> 
> mremap_test.c:1035:31: warning: pointer comparison always evaluates to
> false [-Wtautological-compare]
>  1035 |                 if (addr + c.dest_alignment < addr) {
>       |                                             ^
> 
> this warning is raised from clang version 20.1.8 (Fedora 20.1.8-4.fc42).
> 
> use 'void *tmp_addr' to do the pointer arthemitic.
> 
> Signed-off-by: Ankit Khushwaha <ankitkhushwaha.linux@gmail.com>
> ---
> Changelog:
> v2:
> - use 'void *tmp_addr' for pointer arthemitic instead of typecasting
> 'addr' to 'unsigned long long' as suggested by Andrew.
> 
> v1: https://lore.kernel.org/linux-kselftest/20251106104917.39890-1-ankitkhushwaha.linux@gmail.com/
> ---
>  tools/testing/selftests/mm/mremap_test.c | 5 +++--
>  1 file changed, 3 insertions(+), 2 deletions(-)
> 
> diff --git a/tools/testing/selftests/mm/mremap_test.c b/tools/testing/selftests/mm/mremap_test.c
> index a95c0663a011..308576437228 100644
> --- a/tools/testing/selftests/mm/mremap_test.c
> +++ b/tools/testing/selftests/mm/mremap_test.c
> @@ -994,7 +994,7 @@ static void mremap_move_multi_invalid_vmas(FILE *maps_fp, unsigned long page_siz
>  static long long remap_region(struct config c, unsigned int threshold_mb,
>  			      char *rand_addr)
>  {
> -	void *addr, *src_addr, *dest_addr, *dest_preamble_addr = NULL;
> +	void *addr, *tmp_addr, *src_addr, *dest_addr, *dest_preamble_addr = NULL;
>  	unsigned long long t, d;
>  	struct timespec t_start = {0, 0}, t_end = {0, 0};
>  	long long  start_ns, end_ns, align_mask, ret, offset;
> @@ -1032,7 +1032,8 @@ static long long remap_region(struct config c, unsigned int threshold_mb,
>  	/* Don't destroy existing mappings unless expected to overlap */
>  	while (!is_remap_region_valid(addr, c.region_size) && !c.overlapping) {
>  		/* Check for unsigned overflow */
> -		if (addr + c.dest_alignment < addr) {
> +		tmp_addr = addr + c.dest_alignment;

Nit: tmp_addr can be declared here.

Other than that

Acked-by: Mike Rapoport (Microsoft) <rppt@kernel.org>

> +		if (tmp_addr < addr) {
>  			ksft_print_msg("Couldn't find a valid region to remap to\n");
>  			ret = -1;
>  			goto clean_up_src;
> --
> 2.51.1
> 

-- 
Sincerely yours,
Mike.