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From: rfg@riunite.ACA.MCC.COM (Ron Guilmette)
Newsgroups: comp.lang.c++
Subject: Re: #once cpp directive implemented!
Message-ID: <126@riunite.ACA.MCC.COM>
Date: 20 Mar 89 17:58:46 GMT
References: <124@riunite.ACA.MCC.COM> <11338@ulysses.homer.nj.att.com>
Reply-To: rfg@riunite.UUCP (Ron Guilmette)
Organization: MCC  Austin, Texas
Lines: 38

In article <11338@ulysses.homer.nj.att.com> gsf@ulysses.homer.nj.att.com (Glenn Fowler[drew]) writes:
>In article <124@riunite.ACA.MCC.COM>, rfg@riunite.ACA.MCC.COM (Ron Guilmette) writes:
>
>implementing
>	#once
>as
>	#pragma once 
>would be more in line with the current standards efforts
>since #pragma's may/must be ignored by certain implementations

See my comments in another recent posting.  I think this is a *bad*
idea.

>this would allow for:

>(4)	correctness for any errors/choices in the file identity
>	algorithm (excuse the os-dependent examples):
>	note that with NFS and RFS the same physical file accessed
>	by different paths may have different <dev,ino>

I intentionaly left loopholes in the way #once is implemented.
If you want and/or need to circumvent it, you can easily do so
by simply making multiple links (hard or symbolic) to a given
include file, and then using different pathnames to include the
file.

The point about NFS/RFS and inodes is *not* relevant, because the
ommission of re-included #once files is done of the basis of
remembered pathnames, not on the basis of remembered inode numbers.
The reason for this is simple.  Some systems (e.g. VMS, MS-DOS)
may not support the concept of inodes.  Thus, using pathnames
should be more portable.

-- 
// Ron Guilmette  -  MCC  -  Experimental (parallel) Systems Kit Project
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