An integer overflow may be ignored if an int value is assigned to a long int variable. The problem does not occur if optimization is turned off (compiler version 13.1) or reduced to -O1 (compiler version 11.1). Operating system Linux SLED11SP3. gcc produces the expected result with all optimization levels.
Smallest code example to reproduce:
#include <stdio.h>
int main( int argc, char** argv)
{
int i,i0;
unsigned int ui;
long int l;
unsigned long int ul;
i0=1200000000;
i=2*i0;
ui=2*i0;
l=i;
ul=i;
printf(" int=%d\n unsigned int=%u\n", i,ui);
printf("source int\n long int=%ld\n unsigned long int=%lu\n", l,ul);
l=ui;
ul=ui;
printf("source unsigned int\n long int=%ld\n unsigned long int=%lu\n", l,ul);
}
progs> icc --version
icc (ICC) 13.1.2 20130514
Copyright (C) 1985-2013 Intel Corporation. All rights reserved.
progs> icc iccbug.c;./a.out
int=-1894967296
unsigned int=2400000000
source int
long int=2400000000
unsigned long int=2400000000
source unsigned int
long int=2400000000
unsigned long int=2400000000
progs> icc -O0 iccbug.c;./a.out
int=-1894967296
unsigned int=2400000000
source int
long int=-1894967296
unsigned long int=18446744071814584320
source unsigned int
long int=2400000000
unsigned long int=2400000000
