Check for Endianess of a Machine

EndianTest.c

/* Prints if a machine is Big-Endian or Little-Endian */
#include <stdio.h>
#include <stdint.h>

int main()
{
    uint32_t num = 0x12345678;
    uint8_t *ptr = (uint8_t *) &num;
    
    if (ptr[0] == 0x78)
	printf("LITTLE ENDIAN\n");
    else
	printf("BIG ENDIAN\n");

    printf("Bytes in Memory: %x\t%x\t%x\t%x\n",ptr[0],ptr[1],ptr[2],ptr[3]);
    printf("Addresses:\t %p\t%p\t%p\t%p\n",&ptr[0],&ptr[1],&ptr[2],&ptr[3]);

    return 0;

}

you should change the code to

volatile uint8_t *ptr = (uint8_t *) #

or else the evaluation is optmized out at compiletime showing only the compiletime endianess

bool is_little_endian()
{
uint32_t num = 0x12345678;
volatile uint8_t* ptr = (uint8_t *)#
return ptr[0] == 0x78;
}