Override delete operator

Question

I want to override delete operator in my class. Here's what I am trying to do,but not succeeding.

class Complex{              
    void *operator new(size_t s);
    void operator delete(void *ptr);
};

void Complex::operator delete(void *ptr){
    delete ptr;
}

I get the error:

deleting void* is undefined

Solution 1

As the error message indicates, you can't delete a void*. Try this:

// See http://www.informit.com/guides/content.aspx?g=cplusplus&seqNum=40

#include <new> // for size_t

class Complex
{
public:
 Complex() {}
 ~Complex() {}
 static void* operator new (size_t size) {
  return new char[size];
 }
 static void operator delete (void *p) {
  return delete[] static_cast<char*>(p);
 }
};

int main () {
  Complex *p = new Complex;
  delete p;
}

Solution 2

Your declarations are correct. The problem is in the code that implements your operator delete: it uses the keyword delete instead of calling the global operator delete. Write it like this:

void Complex::operator delete(void *ptr) {
    ::operator delete(ptr);
}

That's assuming that your operator new used the global operator new.

Comments

[Admin]

So, may i know what is happening in those two lines?

[GManNickG]

Use static_cast here, not reinterpret_cast.

[Admin]

So, in the new method does it suffice to write : return (::operator new(s));

[Pete Becker]

@AntonioKumar - yes, the static member function can be written to call the global operator new like that. Which, of course, raises the question of why it's there, since it just does what the compiler would do in its absence.

[GManNickG]

@EmilioGaravaglia: Use a static_cast to undo implicit conversions (char* implicitly converts to void*), reinterpret_cast is too strong. You aren't reinterpreting anything, just rightfully undoing an implicit cast.