GCC seems to treat the 32-bit integer constant -0x80000000 (INT_MIN) as an
unsigned value, when it should be signed. (I don't think this is a duplicate
of bug 25329, since I'm not trying to negate the constant.) For example:
int a = 1;
int foo(void)
{
return -0x80000000 < a;
}
improperly returns 0, even though -0x80000000 is less than any positive value.
>From the assembly output, it seems as though GCC is treating -0x80000000 as an
unsigned value (using the unsigned "seta" instruction to interpret the
comparison result):
movl a, %eax
cmpl $-2147483648, %eax
seta %al
Changing the comparison to:
return (int)-0x80000000 < a; // Cast to signed
succeeds, as expected (interestingly using "setne" rather than "setg", though
certainly either works).
--
Summary: -0x80000000 (INT_MIN) erroneously treated as unsigned
Product: gcc
Version: 4.2.4
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: c
AssignedTo: unassigned at gcc dot gnu dot org
ReportedBy: gcczilla at achurch dot org
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=36402
