[Bug middle-end/95903] gcc 10: wrong code with -fwrapv
cvs-commit at gcc dot gnu.org
gcc-bugzilla@gcc.gnu.org
Mon Jun 29 09:35:23 GMT 2020
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=95903
--- Comment #11 from CVS Commits <cvs-commit at gcc dot gnu.org> ---
The releases/gcc-10 branch has been updated by Jakub Jelinek
<jakub@gcc.gnu.org>:
https://gcc.gnu.org/g:e29959c5fcd6c37b426c2939d7ba0c199b40d1ac
commit r10-8384-ge29959c5fcd6c37b426c2939d7ba0c199b40d1ac
Author: Jakub Jelinek <jakub@redhat.com>
Date: Sat Jun 27 12:38:23 2020 +0200
c-family: Use TYPE_OVERFLOW_UNDEFINED instead of !TYPE_UNSIGNED in
pointer_sum [PR95903]
For lp64 targets and int off ... ptr[off + 1]
is lowered in pointer_sum to *(ptr + ((sizetype) off + (sizetype) 1)).
That is fine when signed integer wrapping is undefined (and is not done
already if off has unsigned type), but changes behavior for -fwrapv, where
overflow is well defined. Runtime test could be:
int
main ()
{
char *p = __builtin_malloc (0x100000000UL);
if (!p) return 0;
char *q = p + 0x80000000UL;
int o = __INT_MAX__;
q[o + 1] = 1;
if (q[-__INT_MAX__ - 1] != 1) __builtin_abort ();
return 0;
}
with -fwrapv or so, not included in the testsuite because it requires 4GB
allocation (with some other test it would be enough to have something
slightly above 2GB, but still...).
2020-06-27 Jakub Jelinek <jakub@redhat.com>
PR middle-end/95903
gcc/c-family/
* c-common.c (pointer_int_sum): Use TYPE_OVERFLOW_UNDEFINED instead
of
!TYPE_UNSIGNED check to see if we can apply distributive law and
handle
smaller precision intop operands separately.
gcc/testsuite/
* c-c++-common/pr95903.c: New test.
(cherry picked from commit 37995960984ea2222346dd9d168d332cd6f7adf0)
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