Array index limit in C

arrays, c

Solution

You're allocating around 14-15 GB memory, and for whatever reason the allocator cannot give you that much at the moment- thus `calloc` returns NULL and you segfault as you're dereferencing a NULL pointer.

Check if calloc returns NULL.

That's assuming you're compiling a 64-bit program under a 64-bit Linux. If you're doing something else - you might overflow the calculation to the first argument to `calloc` if a long is not 64 bits on your system.

For example, try

#include    <stdlib.h>
#include    <stdio.h>

#define N    44000L

int main(void)
{
    size_t width = N * 2 - 1;
    printf("Longs are %lu bytes. About to allocate %lu bytes\n",
           sizeof(long), width * N * sizeof(int));
    int *c = calloc(width * N, sizeof(int));
    if (c == NULL) {
        perror("calloc");
        return 1;
    }
    c[N / 2] = 1;
    return 0;
}

Problem

Original source