More C++ Idioms/Free Function Allocators

Free Function Allocators

Intent

Allow containers to use custom allocators without creating a new type

Motivation

C++ standard allocators have serious problems, because they change the underlying type of the container.

Solution and Sample Code

This idiom is superior to the way that std::allocators work the whole idiom is outlined here.

struct user_allocator_nedmalloc
{
	typedef std::size_t size_type;
	typedef std::ptrdiff_t difference_type;
	
	static inline char* malloc(const size_type bytes) {
		return reinterpret_cast<char*>(nedmalloc(bytes));
	}
	
	static inline void free(char* const block) {
		nedfree(block);
	}
};

Known Uses

• boost::ptr_container

References

• http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2005/n1850.pdf