Well, you have expicit allocators. A popular branch of the field calls this ‘dependency injection’. It's true that the current standard library never allocates

Well, you have expicit allocators. A popular branch of the field calls this ‘dependency injection’. It's true that the current standard library never allocates implicitly, because that would be bad on constrained projects, but there's nothing stopping you from writing code that does so, or presumably even using libc.