https://gcc.gnu.org/bugzilla/show_bug.cgi?id=80525
Bug ID: 80525
Summary: -Wlogical-op confused by undefined integer overflow
Product: gcc
Version: 7.0.1
Status: UNCONFIRMED
Keywords: diagnostic, xfail
Severity: normal
Priority: P3
Component: c
Assignee: unassigned at gcc dot gnu.org
Reporter: rguenth at gcc dot gnu.org
Target Milestone: ---
A subset of c-c++-common/Wlogical-op-1.c doesn't work with -fstrict-overflow:
if ((a + 1) && (a + 1)) {}
and
if ((a + 1) || (a + 1)) {}
do not warn because op_left is a <maybe_const_expr a + 1> != 0 and
op_right a + 1. Fr the first make_range simply returns
<maybe_const_expr a + 1> while for the second it returns a.
it looks like maybe_const_expr handling is bogus here.
With removing -fstrict-overflow I need to XFAIL the subtests (or add -fwrapv
give the test only runs at -O0 at the moment and thus with signed overflow
not undefined).
Testcase:
void andfn (int a, int b)
{
if ((a + 1) && (a + 1)) {}
}
> gcc-7 -S t.c -Wlogical-op
t.c: In function ‘andfn’:
t.c:3:15: warning: logical ‘and’ of equal expressions [-Wlogical-op]
if ((a + 1) && (a + 1)) {}
^~
> gcc-7 -S t.c -Wlogical-op -fstrict-overflow
<nothing>
