🚀 go-pugleaf

fred@mindcraft.com (Fred Zlotnick) writes:
>The C standard reserves certain name spaces for the implementor: __*,
>_[A-Z]*, and for identifiers with file scope (and this is where my
>question arises) _*.  (See section 4.1.2.1 of the ANSI edition, or,
>according to Plauger's book, clause 7.1.3 of the ISO edition, of the
>Standard.)
>Suppose an implementation header defines a macro
>	#define _toupper(ch) ( (ch) + 'A' - 'a' )
>or something similar.  (This is quite common.)  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.  Can such a
>declaration ever get expanded by the macro?  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?

main() {
	int blee;
	double _toupper();

	/* code which does not use _toupper() */
}

This code fragment declares an identifier _toupper with block scope, which
is legal (as long as the program does not create a declaration with file
scope, which means the program can't actually use the function).  Declaring
a macro with that name would probably make the program fail to compile.

I think, therefore, that the implementation may not #define _[0-9a-z]*
identifiers, since they are not reserved for all scopes.