procyberian/gcc
1
0
Fork 0
Code Issues Pull requests Projects Releases Packages Wiki Activity Actions

strlen: Fix another spot that can create invalid ranges [PR114293]

Browse source 
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].

2024-03-12  Jakub Jelinek  <jakub@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.
This commit is contained in:
Jakub Jelinek 2024-03-12 10:23:19 +01:00
parent cdf0c6604d
commit 39737cdf00
2 changed files with 12 additions and 0 deletions
Show stats Download patch file Download diff file Expand all files Collapse all files

10
gcc/testsuite/gcc.dg/pr114293.c Normal file
View file

@ -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);
}

2
gcc/tree-ssa-strlen.cc
View file

@ -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