On June 19, 2017 7:46:03 PM GMT+02:00, Jakub Jelinek <ja...@redhat.com> wrote:
>Hi!
>
>Another easy to fix bug reported by bootstrap-ubsan.
>We check that rhsunitoffset fits into shwi, but even if it does,
>8x that might not, in which case we trigger UB.
>Fixed by doing the multiplication in unsigned HWI type to make it well
>defined.
>
>Bootstrapped/regtested on x86_64-linux and i686-linux (both normal
>and bootstrap-ubsan), ok for trunk?
OK.
Richard.
>2017-06-19 Jakub Jelinek <ja...@redhat.com>
>
> * tree-ssa-structalias.c (get_constraint_for_ptr_offset): Multiply
> in UWHI to avoid undefined overflow.
>
>--- gcc/tree-ssa-structalias.c.jj 2017-05-24 11:59:06.000000000 +0200
>+++ gcc/tree-ssa-structalias.c 2017-06-19 14:10:50.989594911 +0200
>@@ -3087,7 +3087,7 @@ get_constraint_for_ptr_offset (tree ptr,
> {
> /* Make sure the bit-offset also fits. */
> HOST_WIDE_INT rhsunitoffset = soffset.to_shwi ();
>- rhsoffset = rhsunitoffset * BITS_PER_UNIT;
>+ rhsoffset = rhsunitoffset * (unsigned HOST_WIDE_INT) BITS_PER_UNIT;
> if (rhsunitoffset != rhsoffset / BITS_PER_UNIT)
> rhsoffset = UNKNOWN_OFFSET;
> }
>
> Jakub
