Compile this with -O2 -W -Wall and you should not get a warning but you get an
overflow warning which is a false positive as this condition can never be false
even with overflow (as shown by doing -Dint=unsigned):
int bar(int);
int f(int x)
{
int y;
if (x<=4) y = 1;
else y = x/4;
return y <= 0;
}
---------------- CUT -------------------
t.c: In function 'f':
t.c:8: warning: assuming signed overflow does not occur when simplifying
conditional to constant
How can x/4 cause an overflow when x>4 and never negative?
Also when I do -Dint=unsigned or even -fwrapv, VRP still is able to say y is
always greater than 0.
--
Summary: [4.3 Regression] False overflow warning with division
Product: gcc
Version: 4.3.0
Status: UNCONFIRMED
Keywords: diagnostic
Severity: normal
Priority: P3
Component: tree-optimization
AssignedTo: unassigned at gcc dot gnu dot org
ReportedBy: pinskia at gcc dot gnu dot org
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=31522
