To do it in almost-plain C, you'd need fairly complex macros that are more difficult to write correctly.
To do it in plain C without macros, or plain C++ without templates... you'd need to work out the combination of the template expansion yourself and write down a piece of code that is more likely to have bugs and more difficult to understand.
I'm not quite sure: you could probably use plain C functions, and a reasonably smart compiler could see through it all and inline and duplicate and merge the code as necessary.
EDIT: I just had an AI agent run the experiment. At least for my version of clang, they produce the same assembly for x86_64 (modulo using slightly different registers).
