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Overloading Global operator new in C++

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Hello All I overloaded the global operator new to act in a certain manner when provided with additional arguments.
class key{};

void* operator new(size_t sz, key&)
{
    //do some stuff
    return ::operator new(sz);
};
This works fine, except for classes for which operator new is already overloaded.
class test
{
public:
	void* operator new(size_t sz)
	{
		cout << "using custom new"<<endl;
		return ::operator new(sz);
	};
};

int main(int argc, char* argv[])
{
	k k1;
	int*  p_int = new(k1) int;\\ok
        test* p_test1 = new test;\\ok
        test* p_test2 = new(k1) test;\\error
        test* p_test3 = ::new(k1) test;\\ok, but doesn't use test's operator new
	return 0;
}
I am compiling using VC++ 6 and the error I get is: error C2660: 'new' : function does not take 2 parameters Is there a way to support creating my custom new without affecting user class defined new? thanks

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I doubt there is any simple solution to this. Your operator new has no information about what type it's being called on, so any "forwarding" also cannot depend on that type.

The simplest thing you can do is implement intrusively the operator new(size_t, key&) in any classes you wish to use it on, and have it forward the call to the class' operator new.

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The purpose of a placement-new operator is to allocate memory for an object. The purpose of a class-specific new operator is to allocate memory for an object. If you were to invoke both of those, that would equate to allocating memory twice. What are you trying to accomplish.. tracking allocations?

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Just a small correction. Placement new doesn't allocate any memory but constructs an object on a previously allocated memory or even on a stack.

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Quote:
Original post by KreK
Just a small correction. Placement new doesn't allocate any memory but constructs an object on a previously allocated memory or even on a stack.

You're thinking specifically of the placement-new operator which takes a void*. Semantically, the general meaning of new, including placement-new, is the allocation of memory to a resource (note that the term "allocation" doesn't necessarily imply malloc).

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