Question

I am curious whether it is possible to determine the maximum size that an array can have in C++.

    #include <iostream>

    using namespace std;

    #define MAX 2000000

    int main()
    {
      long array[MAX];
      cout << "Message" << endl;
      return 0;
    }

This compiles just fine, but then segfaults as soon as I run it (even though array isn’t actually referenced). I know it’s the array size too because if I change it to 1000000 it runs just fine.

So, is there some define somewhere or some way of having #define MAX MAX_ALLOWED_ARRAY_SIZE_FOR_MY_MACHINE_DEFINED_SOMEWHERE_FOR_ME?

I don’t actually need this for anything, this question is for curiosity’s sake.

Answer 1

There isn’t a way to determine this statically, because the actual limit depends on how much stack space your thread has been given. You could create a new thread, give it 10 megabytes of stack, and you would be able to allocate a correspondingly larger local array.

The amount you can allocate on the stack also depends on how much has already been used so far.