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From: mcdaniel@adi.com (Tim McDaniel)
Newsgroups: comp.lang.c
Subject: Re: Using Macros
Message-ID: <MCDANIEL.90Aug9180827@dolphin.adi.com>
Date: 9 Aug 90 22:08:27 GMT
References: <362.26be9dcc@astro.pc.ab.com> <878@mwtech.UUCP>
Sender: news@adi.COM
Organization: Applied Dynamics Int'l.
Lines: 32
In-reply-to: martin@mwtech.UUCP's message of 8 Aug 90 13:34:33 GMT

martin@mwtech.UUCP (Martin Weitzel) writes:
> As I allready recommended, such macros should not be used very often.
> In fact, I can see only two places where they sometimes may be
> desirable:

c) You need to do something which is impossible without use of the
   preprocessor.  The canonical example is an "assert(x)" that does
   not evaluate its argument at all if assertion checking is turned
   off.

d) You want to make some kind of syntax change to the language.  This
   should be done with EXTREME care!  (The canonical counterexample is
   the original, damn near unreadable, Bourne shell source code.)

   Our example is "MESSAGE(fooBar);" which expands to
      char fooBar = "fooBar";
   In that way, we can
   1) do
         formatMessage(fooBar, ...);
      to get the same effect as
         formatMessage("fooBar", ...);
   2) get a compile-time error rather than a run-time error if we
      make a typo in a message name.
   3) in another section do a check like
         if (message == fooBar) ...	/* pointer equality */
      rather than
         if (!strcmp(message, "fooBar")) ... /* string equality */
--
"I'm not a nerd -- I'm 'socially challenged'."

Tim McDaniel
Internet: mcdaniel@adi.com             UUCP: {uunet,sharkey}!amara!mcdaniel