🚀 go-pugleaf

In article <1992Apr4.011606.23687@mindcraft.com> fred@mindcraft.com (Fred
Zlotnick) writes:
>Suppose an implementation header defines a macro
>       #define _toupper(ch) ( (ch) + 'A' - 'a' )
>or something similar.  (This is quite common.)

It's not common in ANSI conforming implementations, except possibly as an
extension where the program has to do some non-strictly-conforming thing
in order to request the extension.

>Does this step on the application's namespace?  An application is free to
>declare an identifier "_toupper" as long as it does not have file scope.

It does, for the reason you gave.

>This is a function-like macro, and thus is only expanded when the identifier
>is immediately followed by a left parenthesis.  So I guess my question is:
>Can an identifier that is not an external identifier ever legally be followed
>by a left parenthesis?

If the implementation fails to accept this:
  #include <stdlib.h>
  #include <ctype.h>              /* Can use name _toupper for SOME things */
  main() {
    void (*_toupper)() = &exit;   /* Program declares block-scope variable */
    _toupper(EXIT_SUCCESS);       /* Program uses block-scope variable     */
  }
then the implementation is non-conforming.
--
Norman Diamond       diamond@jit081.enet.dec.com
If this were the company's opinion, I wouldn't be allowed to post it.
"Yeah -- bad wiring.  That was probably it.  Very bad."