how to declare a structure with large structure arrays inside it

Question

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

#define     MAXNO   1000

typedef struct
{
    int     n;
    char    site[4];
} stru;

typedef struct
{
    stru t1[MAXNO];
    stru t2[MAXNO];
} struall;

int main()
{
    struall tmp;
    int i;
    printf("%d\n",i);
    return 1;
}

Hi everyone, I am trying to declare a structure variable which has two structure array members inside it. If the array size (MAXNO) is small, i can compile successfully. However, if the array size is very large (define MAXNO as 1000000), the declaration fails with segmentation fault.

Can anyone tell me the reason?

Thanks a lot!

Read a little bit about [stack and heap](http://stackoverflow.com/questions/79923/what-and-where-are-the-stack-and-heap) — Logman, Jul 06 '16 at 02:20
@sjsam You right but reason for this problem is the same in both languages. — Logman, Jul 06 '16 at 02:35

score 2 · Answer 1 · answered Jul 06 '16 at 02:17

2

You can only fit "oh-so-much" onto the machine stack. Try:

struall* tmp = malloc(sizeof(struall));

in C or one of the following for C++:

struall* tmp = new struall; // C++03
std::unique_ptr<struall> tmp{new struall}; // C++11
auto tmp = std::make_unique<struall>(); // C++14

answered Jul 06 '16 at 02:17

kirbyfan64sos

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Nice and complete :-) A bit of explanation about each method will give you a fanbase for this one I guess..nbd though.. – sjsam Jul 06 '16 at 02:41

how to declare a structure with large structure arrays inside it

1 Answers1