[Bug sanitizer/90865] ubsan causes coverage branch errors

[marxin at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=90865

Martin Liška <marxin at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|UNCONFIRMED                 |RESOLVED
         Resolution|---                         |INVALID

--- Comment #1 from Martin Liška <marxin at gcc dot gnu.org> ---
(In reply to sshannin from comment #0)
> Code compiled with gcov and ubsan produces bad coverage results.  It seems
> that ubsan inserts some branches which are visible to gcov as part of its
> instrumentation.
> 
> In the following snippet below you can observe that gcov has flagged "int
> res = 5 / argc;" as containing uncovered branches (checking for division by
> 0?).

Yes, it's expected behavior:

    argc.0 = argc;
    _1 = argc.0 == 0;
    _2 = _1;
    if (_2 != 0) goto <D.2285>; else goto <D.2286>;
    <D.2285>:
    _3 = (unsigned long) argc.0;
    __builtin___ubsan_handle_divrem_overflow (&*.Lubsan_data0, 5, _3);