https://gcc.gnu.org/bugzilla/show_bug.cgi?id=99162
Bug ID: 99162
Summary: problem when compile with O2 or O3
Product: gcc
Version: 4.9.2
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: c++
Assignee: unassigned at gcc dot gnu.org
Reporter: haibin-zhang at 263 dot net
Target Milestone: ---
$ g++ --version
g++ (GCC) 4.9.2
Copyright (C) 2014 Free Software Foundation, Inc.
This is free software; see the source for copying conditions. There is NO
warranty; not even for MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
$ cat a.C
#include <stdlib.h>
#include <stdio.h>
void f(int n) {
unsigned int u = abs(n);
while(true) {
if(u < 10) {
printf("u = %u\n", u);
break;
}
printf("u = %u\n", u);
u /= 10;
}
}
main() {
f(0x80000000);
}
//////////////////////// 02 or 03 can not work ////////////////////////
$ g++ a.C -O2
$ ./a.out
u = 2147483648
//////////////////////// O1 no problem ////////////////////////////////
$ g++ a.C -O1
$ ./a.out
u = 2147483648
u = 214748364
u = 21474836
u = 2147483
u = 214748
u = 21474
u = 2147
u = 214
u = 21
u = 2
