Setting a double pointer array

Question

I know there are a lot of double pointer questions, but I couldn't find one that pertained to starting an array.

In the code below, I can set pointers in main by ptrs[0] = &array[0];, but the code halts when enqueue() calls *queue[i] = p;. Why is that? I don't know if it matters, but ptrs[] is not initialized.

#define QUEUE_LEN 5

int *ptrs[5];
int array[5] = {1,2,3,4,5};

void enqueue(int *p, int **queue) {
    int i = 0;
    int *tmp;

    // Find correct slot
    while (*queue && *queue[i] >= *p) {
        i++;
    }

    // Error no free slots
    if (i == QUEUE_LEN) {
        printf("No free slots.\r\n");
        return;
    }

    // Insert process
    if (!*queue) {
        *queue[i] = p;
        return;
    }
    else {
        tmp = *queue[i];
        *queue[i] = p;
    }

    // Increment the other processes

    return;
}

int main(int argc, char** argv) {

    int i;
    for (i=0; i<5; i++) {
        enqueue(&array[i], ptrs);
    }

    for (i=0; i<QUEUE_LEN; i++)
        printf("%d\n", *(ptrs[i]));

    return 0;
}

Answer 1

After first loop, i will remain zero. Here:

if (!*queue) {
    *queue[i] = p;
    return;
}

You check, that *queue is 0 and dereference it as well. It is UB.

PS. Btw, this:

*queue[i] = p;

Will not compiles, since *queue[i] has type int, but p has type int*.