Re: share/private/slave a subtree - define vs enum

From: Denis Vlasenko <vda@ilport.com.ua>
To: Roman Zippel <zippel@linux-m68k.org>,
	Bryan Henderson <hbryan@us.ibm.com>
Cc: Andrew Morton <akpm@osdl.org>,
	bfields@fieldses.org, linux-fsdevel@vger.kernel.org,
	linux-kernel@vger.kernel.org, linuxram@us.ibm.com,
	mike@waychison.com, Miklos Szeredi <miklos@szeredi.hu>,
	Pekka J Enberg <penberg@cs.helsinki.fi>,
	Alexander Viro <viro@parcelfarce.linux.theplanet.co.uk>
Subject: Re: share/private/slave a subtree - define vs enum
Date: Sun, 10 Jul 2005 13:55:33 +0300	[thread overview]
Message-ID: <200507101355.33338.vda@ilport.com.ua> (raw)
In-Reply-To: <Pine.LNX.4.61.0507081845170.3743@scrub.home>

On Friday 08 July 2005 19:57, Roman Zippel wrote:
> Hi,
> 
> On Fri, 8 Jul 2005, Bryan Henderson wrote:
> 
> > I wasn't aware anyone preferred defines to enums for declaring enumerated 
> > data types.
> 
> If it's really enumerated data types, that's fine, but this example was 
> about bitfield masks.
> 
> > Isn't the only argument for defines, "that's what I'm used to."?
> 
> defines are not just used for constants and there is _nothing_ wrong with 
> using defines for constants.

Apart from the wart that defines know zilch about scopes.
Thus completely fine looking code will give you atrociously
obscure compiler message. Real world example for userspace:

# cat t.c
#include <errno.h>
#include <stdio.h>

void f() {
    char errno[] = "hello world";
    puts(errno);
}

# gcc -c t.c
t.c: In function `f':
t.c:5: error: function `__errno_location' is initialized like a variable
t.c:5: error: conflicting types for '__errno_location'
/usr/include/bits/errno.h:38: error: previous declaration of '__errno_location' was here
--
vda