The following program:
#include <stdio.h>
int main(int argc, char **argv) {
unsigned int testu32a = 0x506f85f;
unsigned long long testu64a = 0x9afa246709018f48ULL;
printf("before: testu64a = %08x%08x, testu32a = %08x\n", (unsigned
int)( testu64a >> 32 ), (unsigned int)( testu64a & 0xffffffff ), testu32a );
while ((unsigned long long)testu32a * (unsigned long long)0xffffffff <
testu64a)
testu64a /= 2;
printf("after: testu64a = %08x%08x, testu32a = %08x\n", (unsigned int)(
testu64a >> 32 ), (unsigned int)( testu64a & 0xffffffff ), testu32a );
return 0;
}
When compiled under freebsd 6 using "gcc -o test test.c" gives different
results when using gcc 3.4.4 or gcc 4.2.4:
Using 3.4.4:
before: testu64a = 9afa246709018f48, testu32a = 0506f85f
after: testu64a = 04d7d12338480c7a, testu32a = 0506f85f
Using 4.2.4:
before: testu64a = 9afa246709018f48, testu32a = 0506f85f
after: testu64a = 9afa246709018f48, testu32a = 0506f85f
The behavior of 4.2.4 has also been seen on a linux gentoo machine running gcc
4.1.2, a 64bit xp machine running gcc 4.2.1, and a regular xp machine running
gcc 4.2.1.
--
Summary: unsinged long long and while loop evaluation regression?
Product: gcc
Version: 4.2.4
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: c
AssignedTo: unassigned at gcc dot gnu dot org
ReportedBy: wilbert at jdg dot info
GCC build triplet: several
GCC host triplet: several
GCC target triplet: several
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=35885
