布局和非布局分配器

Question

What are the placement and non-placement allocation/deallocation function? I've been reading sec. 3.7.4.2 of N3797 and come across with the placement and non-placement allocation / deallocation function concepts. For instance:

The global operator delete with exactly one parameter is a usual ( non-placement ) deallocation function.

I could not find a definition of these concepts and I assume that non-placement is the functions which have one of the following signature:

void* operator new(std::size_t);
void* operator new[](std::size_t);
void operator delete(void*);
void operator delete[](void*);
void operator delete(void*, std::size_t) noexcept;
void operator delete[](void*, std::size_t) noexcept;

Have I understood correctly?

Answer 1

The definition of placement new is in N3797 in section 5.3.4.13 :

The new-placement syntax is used to supply additional arguments to an allocation function. If used, overload resolution is performed on a function call created by assembling an argument list consisting of the amount of space requested (the first argument) and the expressions in the new-placement part of the new-expression (the second and succeeding arguments). The first of these arguments has type std::size_t and the remaining arguments have the corresponding types of the expressions in the new-placement.