Where should Allocators be created?

Hi all, sorry if this has been asked before. I’m a C++ developer and as a first simple project to learn zig I’m making a simple 2D game using SDL. One thing that still isn’t clear for the language is where exactly an allocator should be created (to follow the usual way of doing things). I know that it’s pretty common for games to have more than one allocator type, such as a general allocator and an ArenaAllocator and they can be declared in different places. But, for example, for a general allo...