[Bug c/109151] UBsan misses a divide-by-zero

[cvs-commit at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=109151

--- Comment #5 from CVS Commits <cvs-commit at gcc dot gnu.org> ---
The releases/gcc-12 branch has been updated by Jakub Jelinek
<jakub@gcc.gnu.org>:

https://gcc.gnu.org/g:ffb22189be90216e6af386aaef8b76d2dcd05b84

commit r12-9292-gffb22189be90216e6af386aaef8b76d2dcd05b84
Author: Jakub Jelinek <jakub@redhat.com>
Date:   Fri Mar 17 16:10:14 2023 +0100

    c, ubsan: Instrument even shortened divisions [PR109151]

    On the following testcase, the C FE decides to shorten the division because
    it has a guarantee that INT_MIN / -1 division won't be encountered, the
    first operand is widened from narrower unsigned and/or the second operand
is
    a constant other than all ones (in this case both are true).
    The problem is that the narrower type in this case is _Bool and
    ubsan_instrument_division only instruments it if op0's type is INTEGER_TYPE
    or REAL_TYPE.  Strangely this doesn't happen in C++ FE.
    Anyway, we only shorten divisions if the INT_MIN / -1 case is impossible,
    so I think we should be fine even with -fstrict-enums in C++ in case it
    shortened to ENUMERAL_TYPEs.

    The following patch just instruments those on the ubsan_instrument_division
    side.  Perhaps only the first hunk and testcase might be needed because
    we shouldn't shorten if the other case could be triggered.

    2023-03-17  Jakub Jelinek  <jakub@redhat.com>

            PR c/109151
            * c-ubsan.cc (ubsan_instrument_division): Handle all scalar
integral
            types rather than just INTEGER_TYPE.

            * c-c++-common/ubsan/div-by-zero-8.c: New test.

    (cherry picked from commit 103d423f6ce72ccb03d55b7b1dfa2dabd5854371)