Find out a machine's CPU architecture in C

cpu-arch.c

#include <stdio.h>

int main(void)
{
    /*
     * AMD64
     */

#if defined(__amd64__) || defined(__amd64) || defined(__x86_64__) || defined(__x86_64)
    printf("AMD64\n");
#endif

    /*
     * ARM (32 bits I presume)
     */

#if defined(__arm__)
    printf("ARM 32bits\n");
#endif

    /*
     * ARM64
     */

#if defined(__aarch64__)
    printf("ARM64\n");
#endif

    /*
     * x86
     */

#if defined(i386) || defined(__i386) || defined(__i386__)
    printf("x86\n");
#endif

#ifdef __i486__
    printf("__i486__\n");
#endif

#ifdef __i586__
    printf("__i586__\n");
#endif

#ifdef __i686__
    printf("__i686__\n");
#endif

    return 0;
}