在C ++中重载operator new和operator new []有什么区别？

Question

The operator new and operator new[] has the same function prototype: void * (size_t size) . What should I pay attention to when I'm going to overload them?

Is that OK if I only overload operator new ?

And what's the difference between overload operator delete and operator delete[] ?

Answer 1

operator new is used for creating single object, such as:

my_class* p = new my_class;

operator new[] is used for creating object's array, such as:

my_class* p = new my_class[10];

Is that OK if I only overload operator new?

It depends on if you need special treatment for array version ( operator new[] ). By default operator new[] will call operator new .

Basically, if you need to overload operator new , it's better to overload operator new[] too, because if you want to implement your own memory management, it's a good idea to keep them all consistent. And don't forget the nothrow and placement version(as member functions only, the global version can't be displaced).

The same is true for operator delete and operator delete[] .

Answer 2

new creates an instance, whereas new[] creates a an array.

new[] will almost have little memory overhead compared to new to store the size of the array.

You can't use non-default constructors with new[].

new must be used with delete.

new[] must be used with delete[].

another Difference:

new[] is an operator to allocate and initialize an array of objects and return a pointer to the first element.

This differs from the new operator which has the same behavior but for one allocation, not an array