I am in need to write / overload / override default C++ new operator. I found this below [information](http://en.cppreference.com/w/cpp/memory/new/operator_new) -

```
non-allocating placement allocation functions
void* operator new  ( std::size_t count, void* ptr );
(9) 
void* operator new[]( std::size_t count, void* ptr );
(10)    

```

As per documentation it state -

```
Called by the standard single-object placement new expression. The standard library implementation performs no action and returns ptr unmodified.

```

I am not able to clear myself by what is meant by "**non-allocating placement allocation functions**"?