http://gcc.gnu.org/bugzilla/show_bug.cgi?id=56956
Bug #: 56956
Summary: ftrapv traps on valid abs-like code
Classification: Unclassified
Product: gcc
Version: 4.7.2
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: c
AssignedTo: unassig...@gcc.gnu.org
ReportedBy: sunf...@google.com
This program aborts when compiled with -ftrapv, despite not having any
overflow:
#include <limits.h>
#include <inttypes.h>
#include <stdio.h>
__attribute__((noinline))
uint64_t foo(uint64_t x) {
return x <= INT64_MAX ? x : -x;
}
int main() {
uint64_t n = foo((uint64_t)INT64_MIN);
printf("%" PRIx64 "\n", n);
return 0;
}
It appears that the code in foo is being folded into an absolute-value
expression which does not work properly on INT64_MIN. However, the code as
written does handle INT64_MIN without any signed overflow.
