It's the attempt to tell the host language what you're doing with the arguments that makes a real mess. Module scope is roughly the same as putting it in a sepa

It's the attempt to tell the host language what you're doing with the arguments that makes a real mess. Module scope is roughly the same as putting it in a separate file, i.e. less horrible. C++ has better string literal escaping options which would help. It's very easy to get the constraints wrong and have the aggregate still "work", until unrelated changes months later perturb the register allocation slightly such that it no longer runs as hoped. It's documented and usable but working with it is never a very good time.