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
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;
}
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.
Deleting through delete is quite strange, but deleting a void* is UB.
Also, size_t is not a built-in type: it is define in <cstddef>.
This can be fine:
#include <cstddef>
class Complex
{
void *operator new(size_t s);
void operator delete(void *ptr);
};
void* Complex::operator new(size_t s)
{ return new char[s]; } //allocate a buffer of s bytes
void Complex::operator delete(void *ptr)
{ delete[] static_cast<char*>(ptr); } //deallocate the buffer
Practically, we allocate/deallocate a buffer of appropriate size coherently in new / delete.
In new, we ask the system to give us the bytes we need. I used char[s] since char is the unit of memory size_t measures: sizeof(char) == 1 by definition.
In delete we have to give back to the system the bytes identified by ptr.
Since we allocated them as char[], we have to delete them as char[], hence the use of delete[] and the cast to char*.
