• C

Machine type.

How can I know the machine type
whether it is Big-Endian or Little-Endian programmatically.
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Assuming a 32-bit machine:

#include <stdio.h>

main(int argc, char **argv)
    int i = 0x01020304;
    unsigned char buf[4];
    static unsigned char big[4] = { 0x1, 0x2, 0x3, 0x4};
    static unsigned char little[4] = { 0x4, 0x3, 0x2, 0x1 };

    memcpy(buf, &i, sizeof(buf));

    if (memcmp(buf, big, sizeof(buf)) == 0) {
        printf("Big Endian\n");
    } else if (memcmp(buf, little, sizeof(buf)) == 0) {
        printf("Little Endian\n");
    } else {
        printf("Unknown Layout\n");

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One more small code

typedef union s
int i;
char c[4];

s u;
      printf("Little Endian");
      printf("Big Endian");

Both routines seem to assume 32 bit int and 8 bit char,
u.c==0x44 is comparing a (char *) with an (int),
But even after that's fixed, I don't think the the C standard actually guarantees that the semantics of union members will work that way.
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