From: Denis Vlasenko <vda@ilport.com.ua>
To: "linux-os \(Dick Johnson\)" <linux-os@analogic.com>
Subject: Re: Use enum to declare errno values
Date: Fri, 2 Dec 2005 08:49:28 +0200
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Cc: "Paul Jackson" <pj@sgi.com>, francis_moreau2000@yahoo.fr,
       linux-kernel@vger.kernel.org
References: <20051123132443.32793.qmail@web25813.mail.ukl.yahoo.com> <20051123233016.4a6522cf.pj@sgi.com> <Pine.LNX.4.61.0512011458280.21933@chaos.analogic.com>
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On Thursday 01 December 2005 22:01, linux-os (Dick Johnson) wrote:
> On Thu, 24 Nov 2005, Paul Jackson wrote:
> 
> > If errno's were an enum type, what would be the type
> > of the return value of a variety of kernel routines
> > that now return an int, returning negative errno's on
> > error and zero or positive values on success?
> 
> enums are 'integer types', one of the reasons why #defines
> which are also 'integer types' are just as useful. If you
> want to auto-increment these integer types, then enums are
> useful. Otherwise, just use definitions.

There is another reason why enums are better than #defines:

file.h:
#define foo 123
enum {
	bar = 123
};


file.c:
...
#include "something_which_eventually_includes_file.h"
...
int f(int foo, int bar)
{
	return foo+bar;	
}

Above program has compile-time bug, but it's rather hard
to see it if you are looking at file.c alone.
--
vda
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