What if, memory allocated using malloc is deleted using delete rather than free
c++, free, malloc, memory-management
Solution
When you call `delete` a pointer, the compiler will call the `dtor` of the class for you automatically, but `free` won't. (Also `new` will call `ctor` of the class, `malloc` won't.)
In you example, a char array apparently don't have a dtor, so delete does nothing but return the memory. That's why it's okay. (Or vise versa, new a char array and then free it.)
But there can still be a problem: what if `new` and `malloc` are borrowing memory from different heap manager?
Imagine that, you borrow money from people A, and return to people B later. Even if you are okay with that, have you ever consider A's feeling?
BTW, you should use `delete [] pArray;` to free an array allocated using `new[]`.
Problem
I came across an issue which I could not resolve. My question is, if I used `malloc` to allocate memory and then memory block is delete using `delete`? The general thumb rule is If we allocate memory using malloc, it should be deleted using free. If we allocate memory using new, it should be deleted using delete. Now, in order to check what happens if we do the reverse, I wrote a small code. ``` #include<iostream> #include<cstdio> #include<cstdlib> using namespace std; class A { int p=10; public: int lol() { return p; } }; int main() { int *a = (int *)malloc(sizeof(int)*5); for(int i=0; i<4; i++) { a[i] = i; cout << a[i] << endl; } delete(a); // Works fine till here.. A b; cout << b.lol() << endl; free(b); // Causes error. return 0; } ``` The error which I get is: error: cannot convert ‘A’ to ‘void*’ for argument ‘1’ to ‘void free(void*)’ I am unable to understand why is this happening. Please explain.