What does the operator delete[] do?

Question

#include <iostream>
using namespace std;
class A{
  public:
    int s;
    // ~A(){}
};

int main(){
  A *c = new A[10];  

  delete c;
  return 0;
}

Code above can run successfully, but when i code will get an error. Who can tell me why?

score 2 · Answer 1 · answered Jul 27 '17 at 13:14

2

The behaviour of your code is undefined.

You must write delete[] c; if c is a pointer to memory allocated with new[].

(Interestingly, some compilers sort out this mess for your, but don't rely on that since then you're not writing portable C++).

answered Jul 27 '17 at 13:14

Bathsheba

Thanks. I know what you mean. But why I got an error when I add a destructor for class A? I am confused. – user8376173 Jul 27 '17 at 13:55
That's the nature of undefined behaviour. Anything can happen. – Bathsheba Jul 27 '17 at 13:56
OK. By the way, if I `A *a = new A[10] ` to get an array. Will g++ place the length of a in `(int*)a - 1` ? Just like other compilers do. – user8376173 Jul 27 '17 at 14:16
I think it might put the length at `(size_t*)a - 1`, but I'm not sure. – Bathsheba Jul 27 '17 at 14:18

1 Answers1