#include <stdio.h>
#include <endian.h>

#define TESTIF(a)  printf((a)? (#a ": TRUE") : (#a ": FALSE"));

int main(int argc, char **argv)
{
    TESTIF(sizeof(short) == 2)
    TESTIF(sizeof(int) == 4)
    TESTIF(sizeof(long) == 4)
    TESTIF(sizeof(long long) == 8)
    TESTIF(sizeof(void*) == 4)
    TESTIF(__BYTE_ORDER == __LITTLE_ENDIAN)
}

You can find out the word sizes and endianness of a device by compiling the following program with a cross compiler and looking at the executable with the `strings` program or a hex editor.  The `TESTIF` macro puts a copy of the statement to test and its truth value into a string which will be present in the exe.  This helps if you do not have such a device handy, or if it is cumbersome to access (requires loading firmware etc.).

Determine word sizes by cross-compiling only

C