abs.c

#include <stdio.h>
#include <limits.h>

int f(int x)
{
        int y = x >> 31;
        return (x ^ y) - y;
}


void abs_test(int in)
{
        printf("in=%d, abs=%d\n", in, f(in));
}

int main (int argc, char **argv)
{
        int x = -45, x0 = 100500, x1 = INT_MIN, x2 = 0, x3 = INT_MAX;

        abs_test(x);
        abs_test(x0);
        abs_test(x1);
        abs_test(x2);
        abs_test(x3);

        return 0;
}