Invalid C code result with optimization by SolidSnake2011

The following code gives invalid result with optimization (Release configuration).

#include <stdio.h>
#include <stdlib.h>

typedef char T; // char or short
#define N 4 // any from 4 to 10

void
int2Buf (T * buf, int value, int nBits)
{
    int i;
    for (i = 0 ; i < nBits; i++) {
        buf[i] = value & 1;
        value >>= 1;
    }
}

void
printBuf (T * buf, int nBits)
{
    int i;
    printf ("bits: ");
    for (i = 0; i < nBits; i++) {
        printf ("%d", (int)buf[i]);
    }
    printf ("\n");
}

int
main (void)
{
    T buf[32];
    int2Buf (buf, 0x55555555, N);
    printBuf (buf, N);
    int2Buf (buf, abs(0x55555555), N);
    printBuf (buf, N);
    return 0;
}