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Re: Destructors can copying objects

From "Alf P. Steinbach /Usenet" <alf.p.steinbach+usenet@gmail.com>
Newsgroups comp.lang.c++
Subject Re: Destructors can copying objects
Date 2011-04-16 15:57 +0200
Organization A noiseless patient Spider
Message-ID <ioc77p$oa6$1@dont-email.me> (permalink)
References (2 earlier) <in8ob0$ju1$4@reader1.panix.com> <4d984899$0$6987$9b4e6d93@newsspool4.arcor-online.net> <ioaisv$sah$1@reader1.panix.com> <ioaldo$4o8$1@dont-email.me> <4da976d8$0$6772$9b4e6d93@newsspool3.arcor-online.net>

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* Peter Remmers, on 16.04.2011 13:00:
> Am 16.04.2011 01:47, schrieb Alf P. Steinbach /Usenet:
>>
>> An alternative that is /non-standard/ and /not entirely reliable/, but that is
>> textually much cleaner, is to use a '#pragma once', like so:
>>
>>
>> #pragma once
>>
>> //... text of header file
>>
>>
>> The pragma is problematic when one employs symbolic links to files.
>
> Why would anyone do such a thing?

Well, people have stated directly (on SO) that they do employ symbolic links and 
prefer that. But as far as I recall they have not stated why they employ 
symbolic links, except for general convenience. So this is speculation, but 
consider a library of sublibries, where one would like usage to be like

   #include <vendor/sublibrary/module.h>

Then the directory structure for development might be like

     bigLibrary
         library1
             vendor
                 library1    -> files like [module.h]
         library2
             vendor
                 library2
         library3
             vendor
                 library3

For example, as I recall you find that kind of directory structure for the 
version 2 things in the OpenCV library.

It allows each of the library1 etc. directories to be placed just about anywhere 
and worked on independently, not just as parts of bigLibrary.

But for usage it's a nuisance to set up include paths to all of library1, 
library2, library3 etc. For usage you might therefore instead have

     bigLibrary
         include
             vendor
                 library1  as link to impl/bigLibrary/library1/vendor/library1
                 library2  as link to impl/bigLibrary/library2/vendor/library2

and set up include file search path only to bigLibrary/include directory.

In Windows XP and earlier this is a bit difficult to do  --  no symlinks! But 
the masochistic developer can set up folders that redirect to folders. He he.

<example>
C:\test> md a

C:\test> echo This is the 'a' directory... >a\description.txt

C:\test> which linkd.exe
C:\Program Files\Windows Resource Kits\Tools\linkd.exe

C:\test> md b

C:\test> linkd b a
Link created at: b

C:\test> cd b

C:\test\b> type description.txt
This is the 'a' directory...

C:\test\b> _
</example>


Disclaimer: I haven't tested that for includes. And the idea that this might be 
the reason for people using symlinks is, as I wrote, just speculation. A 
possibility.


Cheers & hth.,

- Alf

-- 
blog at <url: http://alfps.wordpress.com>

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Thread

Destructors can copying objects Ruben Safir <ruben@mrbrklyn.com> - 2011-04-02 12:58 +0000
  Re: Destructors can copying objects Volker Lukas <vlukas@gmx.de> - 2011-04-02 15:29 +0200
    Re: Destructors can copying objects Ruben Safir <ruben@mrbrklyn.com> - 2011-04-03 02:59 +0000
      Re: Destructors can copying objects "Balog Pal" <pasa@lib.hu> - 2011-04-03 11:32 +0200
        Re: Destructors can copying objects Leigh Johnston <leigh@i42.co.uk> - 2011-04-03 12:29 +0100
          Re: Destructors can copying objects Bart van Ingen Schenau <bart@ingen.ddns.info> - 2011-04-04 13:43 +0200
            Re: Destructors can copying objects Michael Doubez <michael.doubez@free.fr> - 2011-04-05 01:26 -0700
          Re: Destructors can copying objects Joshua Maurice <joshuamaurice@gmail.com> - 2011-04-04 14:03 -0700
            Re: Destructors can copying objects Ruben Safir <ruben@mrbrklyn.com> - 2011-04-04 21:10 +0000
            Re: Destructors can copying objects Leigh Johnston <leigh@i42.co.uk> - 2011-04-04 22:28 +0100
          Re: Destructors can copying objects Ruben Safir <ruben@mrbrklyn.com> - 2011-04-04 21:07 +0000
            Re: Destructors can copying objects Leigh Johnston <leigh@i42.co.uk> - 2011-04-04 22:31 +0100
              Re: Destructors can copying objects Leigh Johnston <leigh@i42.co.uk> - 2011-04-04 22:43 +0100
              Re: Destructors can copying objects Ruben Safir <ruben@mrbrklyn.com> - 2011-04-04 22:38 +0000
                Re: Destructors can copying objects Leigh Johnston <leigh@i42.co.uk> - 2011-04-04 23:42 +0100
                Re: Destructors can copying objects Ruben Safir <ruben@mrbrklyn.com> - 2011-04-04 22:54 +0000
      Re: Destructors can copying objects James Kanze <james.kanze@gmail.com> - 2011-04-03 10:07 -0700
        Re: Destructors can copying objects Ruben Safir <ruben@mrbrklyn.com> - 2011-04-04 21:14 +0000
        Re: Destructors can copying objects Ruben Safir <ruben@mrbrklyn.com> - 2011-04-04 21:17 +0000
          Re: Destructors can copying objects LR <lruss@superlink.net> - 2011-04-05 01:52 -0400
    Re: Destructors can copying objects Ruben Safir <ruben@mrbrklyn.com> - 2011-04-03 03:08 +0000
      Re: Destructors can copying objects Paavo Helde <myfirstname@osa.pri.ee> - 2011-04-03 02:11 -0500
      Re: Destructors can copying objects Volker Lukas <vlukas@gmx.de> - 2011-04-03 12:02 +0200
      Re: Destructors can copying objects Peter Remmers <p.remmers@expires-2011-04-30.arcornews.de> - 2011-04-03 12:14 +0200
        Re: Destructors can copying objects Roberto Waltman <usenet@rwaltman.com> - 2011-04-03 18:16 -0400
          Re: Destructors can copying objects Ruben Safir <ruben@mrbrklyn.com> - 2011-04-15 23:06 +0000
            Re: Destructors can copying objects LR <lruss@superlink.net> - 2011-04-15 19:19 -0400
        Re: Destructors can copying objects Ruben Safir <ruben@mrbrklyn.com> - 2011-04-15 23:03 +0000
          Re: Destructors can copying objects "Alf P. Steinbach /Usenet" <alf.p.steinbach+usenet@gmail.com> - 2011-04-16 01:47 +0200
            Re: Destructors can copying objects Peter Remmers <p.remmers@expires-2011-04-30.arcornews.de> - 2011-04-16 13:00 +0200
              Re: Destructors can copying objects "Alf P. Steinbach /Usenet" <alf.p.steinbach+usenet@gmail.com> - 2011-04-16 15:57 +0200
  Re: Destructors can copying objects LR <lruss@superlink.net> - 2011-04-02 09:51 -0400
  Re: Destructors can copying objects Yannick Tremblay <yannick@tremnblay.co.uk> - 2011-04-04 12:56 +0000
    Re: Destructors can copying objects Ruben Safir <ruben@mrbrklyn.com> - 2011-04-04 21:05 +0000
      Re: Destructors can copying objects Paavo Helde <myfirstname@osa.pri.ee> - 2011-04-04 21:56 -0500
      Re: Destructors can copying objects Yannick Tremblay <yannick@tremnblay.co.uk> - 2011-04-05 11:36 +0000
        Re: Destructors can copying objects Ruben Safir <ruben@mrbrklyn.com> - 2011-04-05 15:40 +0000
          Re: Destructors can copying objects Sana <sanatakos@gmail.com> - 2011-04-05 10:11 -0700
          Re: Destructors can copying objects Ruben Safir <ruben@mrbrklyn.com> - 2011-04-05 20:28 +0000
          Re: Destructors can copying objects Yannick Tremblay <yannick@tremnblay.co.uk> - 2011-04-06 11:12 +0000
      Re: Destructors can copying objects drew@furrfu.invalid (Drew Lawson) - 2011-04-05 13:02 +0000
        Re: Destructors can copying objects Ruben Safir <ruben@mrbrklyn.com> - 2011-04-05 15:51 +0000
          Re: Destructors can copying objects drew@furrfu.invalid (Drew Lawson) - 2011-04-05 17:47 +0000
            Re: Destructors can copying objects Ruben Safir <ruben@mrbrklyn.com> - 2011-04-05 20:25 +0000
              Re: Destructors can copying objects drew@furrfu.invalid (Drew Lawson) - 2011-04-05 20:37 +0000

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