Custom allocator in std::vector

Question

Is it possible to use custom allocator for std::vector internal allocations? If yes, how?

Grappa

template < class T, class Allocator = allocator<T> > class vector; – Hyposensitize

@LuchianGrigore And how to use that? – Grappa

First google link - josuttis.com/libbook/memory/myalloc1.cpp.html and josuttis.com/libbook/memory/myalloc.hpp.html – Hyposensitize

See this recent answer by Howard Hinnant: https://mcmap.net/q/428335/-can-i-assume-allocators-don-39-t-hold-their-memory-pool-directly-and-can-therefore-be-copied – Blanco

What do you mean by "internal allocations"? What aspect of the vector's allocator concept is unclear? – Matti

@KerrekSB If I am not mistaken, vector calls new / delete internally when the size changes. Those (de)allocations were meant by the word 'internal'. – Grappa

@James: No. vector calls alloc.allocate() and alloc.deallocate() when the size changes. – Matti

Answer 1

You basically have to implement your allocator type to conform to the Allocator concept.

The linked page lists all requirements of that type, but the core functionality is implemented in the allocate member function.

Bellbottoms

could you give an example – Mechanical

@Mechanical Click on the link, it has tons of examples. – Bellbottoms

This is exactly the reason why link only answers are bad! The page doesn't exist anymore. Pointing towards examples in the broken link is even worse. – Gualterio

At least I updated the link. The new page is referenced, as cppreference is a wiki. But your point is taken. – Bellbottoms

Here is a running example derived from the reference. – Vanward