On Tue, 12 Mar 2024, Jakub Jelinek wrote:
> Hi!
>
> This PR is similar to PR110603 fixed with r14-8487, except in a different
> spot. From the memset with -1 size of non-zero value we determine minimum
> of (size_t) -1 and the code uses PTRDIFF_MAX - 2 (not really sure I
> understand why it is - 2 and not - 1, e.g. heap allocated array
> with PTRDIFF_MAX char elements which contain '\0' in the last element
> should be fine, no? One can still represent arr[PTRDIFF_MAX] - arr[0]
> and arr[0] - arr[PTRDIFF_MAX] in ptrdiff_t and
> strlen (arr) == PTRDIFF_MAX - 1) as the maximum, so again invalid range.
> As in the other case, it is just UB that can lead to that, and we have
> choice to only keep the min and use +inf for max, or only keep max
> and use 0 for min, or not set the range at all, or use [min, min] or
> [max, max] etc. The following patch uses [min, +inf].
>
> Bootstrapped/regtested on x86_64-linux and i686-linux, ok for trunk?
OK.
Richard.
> 2024-03-12 Jakub Jelinek <ja...@redhat.com>
>
> PR tree-optimization/114293
> * tree-ssa-strlen.cc (strlen_pass::handle_builtin_strlen): If
> max is smaller than min, set max to ~(size_t)0.
>
> * gcc.dg/pr114293.c: New test.
>
> --- gcc/tree-ssa-strlen.cc.jj 2024-01-30 09:57:58.361809262 +0100
> +++ gcc/tree-ssa-strlen.cc 2024-03-11 10:35:04.305650520 +0100
> @@ -2341,6 +2341,8 @@ strlen_pass::handle_builtin_strlen ()
> wide_int min = wi::to_wide (old);
> wide_int max
> = wi::to_wide (TYPE_MAX_VALUE (ptrdiff_type_node)) - 2;
> + if (wi::gtu_p (min, max))
> + max = wi::to_wide (TYPE_MAX_VALUE (TREE_TYPE (lhs)));
> set_strlen_range (lhs, min, max);
> }
> else
> --- gcc/testsuite/gcc.dg/pr114293.c.jj 2024-03-11 10:41:04.375708877
> +0100
> +++ gcc/testsuite/gcc.dg/pr114293.c 2024-03-11 10:40:50.355895196 +0100
> @@ -0,0 +1,10 @@
> +/* PR tree-optimization/114293 */
> +/* { dg-do compile } */
> +/* { dg-options "-O2 -w" } */
> +
> +int
> +foo (int x)
> +{
> + __builtin_memset (&x, 5, -1);
> + return __builtin_strlen ((char *) &x);
> +}
>
> Jakub
>
>
--
Richard Biener <rguent...@suse.de>
SUSE Software Solutions Germany GmbH,
Frankenstrasse 146, 90461 Nuernberg, Germany;
GF: Ivo Totev, Andrew McDonald, Werner Knoblich; (HRB 36809, AG Nuernberg)
