Double the shenanigans

pi.c

#include <stdio.h>

#ifndef M_PI
#define M_PI                3.14159265358979323846264338327950288
#endif
#define SIGNIFICAND_SIZE    52
#define EXPONENT_MASK       0x7FF
#define SIGNIFICAND_MASK    0x000FFFFFFFFFFFFFL

typedef union {
    unsigned long i;
    double f;
} louble;

int main() {
    louble x = { .f = M_PI };
    unsigned long exp = (x.i >> SIGNIFICAND_SIZE) & EXPONENT_MASK,
                  sig = x.i & SIGNIFICAND_MASK;

    printf("π = 0x%016lx = %lg\n", x.i, x.f);
    printf("    Exp: 0x%3lx\tSig: 0x%lx\n", exp, sig);

    return 0;
}