Builtin symbols should be namespaced __exp() and he one who want the builtin short named could (and I guess the include math.h) can do that. #define exp __exp There is no problem of renaming it because as a user you will never set a BP into the builtin. With the reversed logic, compilers (or normalisation I guess) despotically pick a stdlib function name, decide it become a builtin, and the one who never used it, but may colide with the symbol, are now directed toward their rename #define exp my_exp That is a pitty because now, some debugger don't know this macro name so setting BP is a problem (you got to remember the macro expanded name) I am not to happy with that. On this occurence I can manage by declaring my int exp as static, with some tricks to pass the addr of it to other CU consumers, the beauty of external static.. How well...
