Integer promotion rules!!!

gistfile1.txt

fabiang@ryg-ivbultra ~/code/uac » cat test.c
#include <stdio.h>

int main()
{
    size_t a = ~0;
    size_t b = ~0 << 5;
    size_t c = ~0 >> 1;
    size_t d = ~0u >> 1;
    printf("a=0x%zx\n", a);
    printf("b=0x%zx\n", b);
    printf("c=0x%zx\n", c);
    printf("d=0x%zx\n", d);
    return 0;
}
fabiang@ryg-ivbultra ~/code/uac » gcc -Wall test.c && ./a.out
a=0xffffffffffffffff
b=0xffffffffffffffe0
c=0xffffffffffffffff
d=0x7fffffff