https://gcc.gnu.org/bugzilla/show_bug.cgi?id=102697
Martin Sebor <msebor at gcc dot gnu.org> changed:
What |Removed |Added
----------------------------------------------------------------------------
Summary|[Diagnostics] overflow |[12 Regression] overflow
|warning missing after O2 |warning missing after -O2
|vectorization. |vectorization
Last reconfirmed| |2021-10-12
Ever confirmed|0 |1
Status|UNCONFIRMED |NEW
--- Comment #2 from Martin Sebor <msebor at gcc dot gnu.org> ---
Confirmed as a false negative and a GCC 12 regression.
The expected warning is based on the assumption that an unknown offset to a
subobject is non-negative. This assumption is supported by the constraint that
pointer arithmetic must be confined to the [sub]object the pointer points to.
I.e., it's not valid to form a pointer to one subobject by adding an offset to
a pointer to another [sub]object (even within the same object). The same
constraint is enforced by -Warray-bounds. The missing -Wstringop-overflow is
due to the hack mentioned in the following discussion:
https://gcc.gnu.org/pipermail/gcc-patches/2021-September/580172.html
The warning is issued from the strlen pass which runs at -O2 and above. It's
still issued when -fno-tree-vectorized is specified but should be issued even
with vectorization, and ideally at all optimization levels, including -O0.
