Understanding memory allocation, test program crashing

Question

I am just about finished reading K&R, and that is all the C that I know. All my compilation is done from Windows command line using MinGW, and I have no knowledge of ad

Answer 1

The size of the stack in a Windows program is usually around 1 MB, so on the second recursion, you're overflowing the stack. You shouldn't be allocating such large arrays on the stack, use malloc and free to allocate and deallocate the memory on the heap (there's no way to get around malloc for such sizes of arrays):

void alloc_one_meg() {
    int *megabyte = malloc(sizeof(int) * 250000); // allocate space for 250000
                                                  // ints on the heap
    int i;
    for (i=0; i<250000; i++) {
        megabyte[i] = rand();
    }
    j++;
    printf("Loop %d\n", j); // ghetto debug
    if (j<1000) {
        alloc_one_meg();
    }

    free(megabyte); // DO NOT FORGET THIS
}

That said, you can actually change the stack size of a program and make it bigger (though I'd only do so as an educational exercise, not in production code). For Visual Studio you can use the /F compiler option, and on linux you can use setrlimit(3). I'm not sure what to use with MinGW though.