C++ array declare issue

Question

This code is giving me segfault :

#include <stdio.h>  

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

int ar[20000000];  

return 0;  

}  

But if I reduce the size of array by 0 - then its fine. Am I exceeding the max size? What if I want to store that amount of integers? Thanks.

Answer 1

It probably has to do with the fact that you're trying to allocate over 70 megabytes of data on the stack. Windows has a default stack size of 1 megabyte per thread IIRC. Try allocating it on the free-store with new , like so:

int* ar = new int[20000000];

and when you're done using it, delete[] it:

delete[] ar;

Answer 2

You got stack overflow :DA real one.

Allocate the memory on the heap, using new

int* ar = new int[ 20000000 ];
// do stuff with ar
delete[] ar; // do **not** forget about this

Answer 3

the declaration of int ar[20000000] on the stack, takes appx 70MB+ (76.2939453MB) of memory... maybe you run out of space?

Use new to allocate on the heap.

Answer 4

You may be exceeding the size allowed by the stack frame, which is enforced by your compiler. If you were to allocate the space dynamically, eg:

int array = new int[SIZE]

you would be limited by your OS and hardware rather than your compiler. (This is because dynamically allocating memory stores it on the heap, whereas a locally declared variable is stored on the stack, which has a stricter size limitation.)

Answer 5

如果我没错，那就是400万

Answer 6

If you really want to allocate this array on the stack, you can. You just need to increase the stack size. You don't say what compiler / linker you are using, but instructions for Visual Studio C++ are here: http://msdn.microsoft.com/en-us/library/tdkhxaks.aspx and other environments should have similar options.