Historically stl::allocator were though to overcome issue with near and far pointer on intel archictecture and share a lot of issue from this time. Andreid revisit how they should have been implemented. - CppCon

which gives interface:

• allocate
• owns
• deallocate
• deallocateAll

Manipulating block made of (addr, size).

Danger:

• Freelist: are adversed to cache and can eat all memory.

See also custom vector allocator