Re: [PATCH] stdlib: Avoid undefined behavior in stdlib/tst-labs

[Siddhesh Poyarekar <siddhesh@gotplt.org>]

Reviewed-by: Siddhesh Poyarekar <siddhesh@sourceware.org>

On 2023-05-16 17:35, Florian Weimer via Libc-alpha wrote:
> The last loop could attempt to overflow beyond INT_MAX on 32-bit
> architectures.
> 
> Also switch to GNU style.
> 
> ---
>   stdlib/tst-labs.c | 25 +++++++++++++------------
>   1 file changed, 13 insertions(+), 12 deletions(-)
> 
> diff --git a/stdlib/tst-labs.c b/stdlib/tst-labs.c
> index 92b456745a..a8d2381f87 100644
> --- a/stdlib/tst-labs.c
> +++ b/stdlib/tst-labs.c
> @@ -25,25 +25,26 @@
>   
>   static int do_test (void)
>   {
> -  long i;
> +  long int i;
>   
> -  TEST_COMPARE(labs(LONG_MAX), LONG_MAX);
> -  TEST_COMPARE(labs(LONG_MIN + 1), LONG_MAX);
> -  TEST_COMPARE(labs(-1), 1);
> -  TEST_COMPARE(labs(0), 0);
> -  TEST_COMPARE(labs(1), 1);
> +  TEST_COMPARE (labs (LONG_MAX), LONG_MAX);
> +  TEST_COMPARE (labs (LONG_MIN + 1), LONG_MAX);
> +  TEST_COMPARE (labs (-1), 1);
> +  TEST_COMPARE (labs (0), 0);
> +  TEST_COMPARE (labs (1), 1);
>   
>     for (i = LONG_MIN + 1; i < LONG_MIN + INT_MAX; i += LARGE_PRIME)
> -    TEST_COMPARE(labs(i), -i);
> +    TEST_COMPARE (labs (i), -i);
>   
> -  for (i = LONG_MAX - INT_MAX; i < LONG_MAX - LARGE_PRIME; i += LARGE_PRIME)
> -    TEST_COMPARE(labs(i), i);
> +  for (i = LONG_MAX - INT_MAX; i < LONG_MAX - LARGE_PRIME;
> +       i += LARGE_PRIME)
> +    TEST_COMPARE (labs (i), i);
>   
>     for (i = INT_MIN + 1; i < 0; i += LARGE_PRIME)
> -    TEST_COMPARE(labs(i), -i);
> +    TEST_COMPARE (labs (i), -i);
>   
> -  for (i = 0; i < INT_MAX; i += LARGE_PRIME)
> -    TEST_COMPARE(labs(i), i);
> +  for (i = 0; i <= INT_MAX - LARGE_PRIME; i += LARGE_PRIME)
> +    TEST_COMPARE (labs (i), i);
>   
>     return EXIT_SUCCESS;
>   }
> 
> base-commit: 641c4c2b7eb80e2cb2121b1c31096158091a6419
>