deleting a char array pointer trigger a mysterious breakpoint

Question

I have the next following code :

#include<iostream>
using namespace std;


void test(char arr[], int size){
    char* newA = new char[5];
    delete[] arr; // this line cause the breakpoint
    arr = newA;
}

void main(){
    char* aa = new char[5];
    test(aa,5);
    aa[0] = 's';
}

When I run this code I see that the variable "aa" at index zero is 's' then the breakpoint is triggered.

https://i.sstatic.net/pzcw6.png

Answer 1

You are passing arr by value, so this line

arr = newA;

has no effect in the caller side. So you are reading from a deleted array here:

aa[0] = 's';

This is undefined behaviour. You can fix this in three ways:

Pass a reference:

void test(char*& arr, int size) { .... }

Return the pointer:

char* test(char* arr, int size) {
  delete[] arr;
  return new char[5];

}

Or, better, use well behaved standard library types such as std::string.