Why does this give a segmentation fault?

I'm stunned, why does this code give me a segmentation fault?

#include <stdio.h>

#define LIMIT 1500000

typedef struct {
    int p;
    int a;
    int b;
} triplet;

int main(int argc, char **argv) { 
    int i;
    triplet triplets[LIMIT];

    for (i = 0; i < LIMIT; i++) {
        triplets[i].p = 9; // remove this line and everything works fine
    }

    printf("%d\n", triplets[15].p);

    return 0; 
}

EDIT: After changing LIMIT to 150 I no longer get a segmentation fault, it prints random numbers instead.

EDIT2: Now I know what the site name stands for :) I made the array global a开发者_Python百科nd everything works fine now.

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Stack overflow! Allocating 1500000 records at 12 bytes per record (assuming 4-byte int), requires more than 17 MB of stack space. Make your triplets array global or dynamically allocate it.

As to your edit - shrinking the array will probably stop the stack overflow, but your printf() call will still print uninitialized data - triplets[15].p could be anything at the time you print it out.

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When you do

triplet triplets[LIMIT];

you're allocating that on the stack. Which is apparently too big for your system.

If you do

triplet* triplets=(triplet*)malloc(LIMIT*sizeof(triplet));

you'll allocate it on the heap and everything should be fine. Be sure to free the memory when you're done with it

free(triplets);