Rust's macros are recursive intentionally, and the compiler implements a recursion limit that IIRC defaults to 64, at which point it will error out and mention that you need to increase it with an attribute in the code if you need it to be higher. This isn't just for macros though, as I've seen it get triggered before with the compiler attempting to resolve deeply nested generics, so it seems plausible to me that C compilers might already have some sort of internal check for this. At the very least, C++ templates certainly can get pretty deeply nested, and given that the major C compilers are pretty closely related to their C++ counterparts, maybe this is something that exists in the shared part of the compiler logic.