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From: schmidt@zola.ics.uci.edu (Doug Schmidt)
Newsgroups: comp.lang.fortran,comp.lang.c
Subject: Function prototypes
Message-ID: <12942@paris.ics.uci.edu>
Date: 29 Apr 89 19:18:17 GMT
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Xref: utzoo comp.lang.fortran:1990 comp.lang.c:18183

I'm about to port a C++ program to C.  The original C++ program uses
function prototypes heavily.  It seems ashame to remove all the extra
type checking, but the port must run on both ANSI and non-ANSI C
compilers.  Therefore, I'd like to know whether anyone has devised a
useful set of preprocessor conventions that allow relatively
transparent conversion between compilers that accept prototypes and
those that don't.

Dealing with external declarations seems fairly straight-forward:

/* prototype.h */
#ifdef __STDC__
#define P(X) X
#else
#define P(X)
#endif

Then all extern decls could look like:

#include "prototype.h"
int foo (P(int foobar));

and the preprocessor will correctly substitute in a prototype for ANSI
compilers or do nothing, for non-ANSI compilers.  This should work in
general, right?

However, for function definitions things get messy.  For example, I
could use the old:

#ifdef __STDC__
int foo (int foobar)
#else
int foo (foobar)
    int foobar;        
#endif

trick, but this gets ugly real quick.

Does anyone have a set of macros that helps simplify and beautify the
process?!

thanks,

   Doug
--
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