Placement New in C + +

Placement New in C + + is: The overloaded version of operator new, which is used to create objects on already allocated memory. This allows the memory to be manipulated in user space, reducing the cost of object generation, controlling the object's address to reduce memory fragmentation, and object pool estimation.

classa{ Public: A () {cout<<"A"<<Endl; }    ~A () {cout<<"~a"<<Endl; }};intMain () {void* T=MALLOC (sizeof(Char)* -); A* a=New(t) A (); Delete A;}

Function prototype: void *operator new (size_t, void *p) throw () {return p;}

The above is called after: Oerator new (sizeof (a), a).

Recently see Netty source, buffer unexpectedly use jemalloc things, it seems to take some time to chew down this piece

Placement New in C + +