🚀 go-pugleaf

The ANSI standard says in Section 7.8.1.1 with regard to the macro:

va_start(ap,parmN)

that:

"If the parameter parmN is declared .... with a type that is not compatible
with the type that results after the application of the default argument
promotions,the behavior is undefined."

This prevents parmN from having char/short/float type.
My question is: why is this restriction imposed?

It seems to me that the variadic function being defined by <stdarg.h> and
va_start will have a prototype with the ellipsis function, and can assume
that all calls to it will be governed by a prototype, and therefore need
not have the default promotions applied to the named parameters.
I see no reason why the compiler can't support char/short/float types.

Sorry if this is discussed in the "rationale", but I haven't a copy of it.

Thanks for any insight,
David Spuler
--
David Spuler, James Cook University of North Queensland, Australia
Author of "Comprehensive C", Prentice-Hall, 1992, pp416, ISBN  0-13-156514-1
INTRO TOPICS: types, operators, structures, strings, fns, ptrs, files etc etc
ADVANCED TOPICS: efficiency, debugging, style, portability, large programs