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Re: Function pointers and #defines

To: "Kevin D. Kissell" <kevink@mips.com>
Subject: Re: Function pointers and #defines
From: "Gleb O. Raiko" <raiko@niisi.msk.ru>
Date: Fri, 31 May 2002 13:15:22 +0400
Cc: Daniel Jacobowitz <dan@debian.org>, Justin Carlson <justinca@cs.cmu.edu>, linux-mips@oss.sgi.com
Organization: NIISI RAN
References: <1022787167.14210.472.camel@ldt-sj3-022.sj.broadcom.com> <20020530195052.GA10587@branoic.them.org> <023001c2081f$95a397d0$10eca8c0@grendel>
Sender: owner-linux-mips@oss.sgi.com
"Kevin D. Kissell" wrote:
> 
> From: "Daniel Jacobowitz" <dan@debian.org>
> > On Thu, May 30, 2002 at 12:32:47PM -0700, Justin Carlson wrote:
> > > A fair number of places in the headers, we have stuff like this:
> > >
> > > void (*_some_fn)(int arg1, int arg2);
> > > #define some_fn(arg1, arg2) _some_fn(arg1, arg2)
> > >
> > > Why do we do this, as opposed to:
> > >
> > > void (*some_fn)(int arg1, int arg2);
> > >
> > > Both syntaxes result in being able to say
> > >
> > > some_fn(1, 2);
> > >
> > > but the latter is both clearer and shorter.  Is there some deep,
> > > mystical C reason that we use the former, or did someone do it that way
> > > a long time ago and no one has changed it?
> >
> > At a guess, this prevents taking the address of the function
> > unintentionally...
> 
> More likely, some ancient early version of the code was
> written with a single global function, some_fn(), and it
> was easier to override it with a pointer indirection in
> the header than to hunt down and change all invocations.
> Sometimes that's good software engineering.  Sometimes
> it's just laziness...
> 
>             Kevin K.

Just remove the declaration, compile, and look at the code generated.
So, #define is just a safety belt.

Regards,
Gleb.

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