Thread: What does FDECL mean? (eg. function #define questions)

Being curious, I did a search which eventually led me to this .

Code:

#ifdef HAVE_PROTOTYPES
# define NDECL(f)        f(void)
# define FDECL(f, p)     f p
# ifdef HAVE_STDARG
#  define VDECL(f, p)     f p
# else
#  define VDECL(f, p)     f()
# endif
#else
# define NDECL(f)        f()
# define FDECL(f, p)     f()
# define VDECL(f, p)     f()
#endif

I would say that in this case, NDECL is being used with functions with no arguments, and FDECL is being used with functions that have arguments. HAVE_PROTOTYPES appears to be conditional depending on whether pre-standard C is being used.

Code:

#if __STDC__ - 0
# undef  HAVE_PROTOTYPES
# define HAVE_PROTOTYPES
#endif

There was no void in pre-standard C.

And the STATIC_DECL is a conditionally-static declaration. That is, given certain precompiler conditions, the function may be declared as static or it may not.

A #define does macro replacement, text for text. If you ran this through the preprocessor,

Code:

extern int    FDECL(cstrcmp,(CONST char *s, CONST char *t));

it would become this.

Code:

extern int    cstrcmp (CONST char *s, CONST char *t);

(And the CONST is likely to conditionally be const or nothing.)

The macros appear to be a way in which this project attempts to be compatible a number of systems.

Originally Posted by sofakng

What about something like this: (?)

Code:

E void FDECL(m_unleash, (struct monst *,BOOLEAN_P));

I now understand that it would become:

E void m_unleash (struct monst *, BOOLEAN_P)

...but what does the E mean?

I thought I saw it somewhere (conditionally?) #defined as extern.

Originally Posted by sofakng

Also, one last question about the following code. Ignore what it's doing, my question has to do with the function declaration syntax...

Code:

#ifndef WIN32CON
/* fatal error */
/*VARARGS1*/
void
error VA_DECL(const char *,s)
	char buf[BUFSZ];
	VA_START(s);
	VA_INIT(s, const char *);
	/* error() may get called before tty is initialized */
	if (iflags.window_inited) end_screen();
	if (!strncmpi(windowprocs.name, "tty", 3)) {
		buf[0] = '\n';
		(void) vsprintf(&buf[1], s, VA_ARGS);
		Strcat(buf, "\n");
		msmsg(buf);
	} else {
		(void) vsprintf(buf, s, VA_ARGS);
		Strcat(buf, "\n");
		raw_printf(buf);
	}
	VA_END();
	exit(EXIT_FAILURE);
}
#endif

VA_DECL is declared like this:

Code:

# define VA_DECL(typ1,var1)	(typ1 var1, ...) { va_list the_args;
// or  (depending on some #define)
#  define VA_DECL(typ1,var1)	(va_alist) va_dcl {\
		va_list the_args; typ1 var1;

What confuses me is that the function above (void error) is that it looks like it's being started without an opening brace. Is that taken care of from the #define macro? Is the #define macro also declaring a variable? It looks like the macro needs four parameters but is only being passed in two...

[I added the highlighting.]

The opening brace is part of the macro. And these are the two parameters it takes. The bold stuff is the replacement list.

Originally Posted by sofakng

I would expect it to be replaced like this:

(va_list) va_dcl {
va_list the_args; typ1 var1;

...instead of:

(va_list) va_dcl {
va_list the_args; hello goodbye;

It would be the latter.

Code:

(va_list) va_dcl {
  va_list the_args; hello goodbye;

Originally Posted by sofakng

At least according to a tutorial I've read about #define's. Also, can a #define have other defines inside of it? It looks like va_dcl might be yet another #define inside the #define... (confusing...)

Can you post a link to the tutorial?

Often parentheses are used with macros because it is just a text replacement. Things may be dandy with simple things, but results may be surprising with more complicated expressions.