Sounds like the Odin implementation isn't particularly optimal. My point wasn't about speed or good implementations. My point was about which languages make it practical to consistenly use custom allocators as a user of the language. Not just across your own code, but also code from the standard library and external packages.

I have no practical Odin experience, I just looked at the core concepts. I tried a bit of Zig and there's significant discipline in the standard library to enable allocator use. But in 3rd Party libraries this discipline is hard to enforce because it also makes it harder to design easy to use interfaces.

I'm interested where on the spectrum of allocator usability Rust will end up at. I'd expect it somewhere between Zig and C++