From: Gianni Mariani <gmariani@chaincast.com>
To: Robert Dewar <dewar@gnat.com>
Cc: gcc@gcc.gnu.org
Subject: Re: c++ "with" keyword
Date: Sun, 05 Jan 2003 02:55:00 -0000 [thread overview]
Message-ID: <3E17968F.7020807@chaincast.com> (raw)
In-Reply-To: <20030104223552.724F0F28C4@nile.gnat.com>
Robert Dewar wrote:
>>Any language construct that fails in this regard (like with) is very bad
>>- period.
>>
>>
>
>But look carefully at what you are saying. We are talking about a structure
>or class whose members are visible to the client of the library. The change
>we are talking about is adding a new member to the structure. You cannot
>possibly think that such a change can be done in a guaranteed 100%
>upwards compatible manner. That's absurd.
>
>(for example, at the very least the size of an instance will change).
>
>Furthermore, the situations under which adding this member will cause
>specifically a difficulty with WITH are very marginal. It is indeed
>far more likely that the addition of a member will cause other compatibility
>differences.
>
>If you disagree, give a specific realistic example of what you are talking
>about. I certainly can't think of one!
>
You talk about binary compatability. I'm more concerned about source
compatability however there are issues with binary compatability as well
- in the case, use of enums or typedefs in a class may cause binary
issues. Think a little harder, they are there.
>
>
>
>>Again, our perspectives on what is important is different, as a library
>>maintainer, I see this as much more important an issue than you do.
>>
>>
>>
>>
>
>Again, remember we are talking not about the writer of the library but the
>user.
>
Hey - I'm talking about both - in any case, almost moderately sized
project will have libraries and in a software development house, you
want source level compatability. The distinction of library producer
and consumer is mute.
>Suppose the user obtains an offset of a member of the structure, and
>you add a new member. Well then the offset changes, and that could cause
>arbitrary chaos of a really difficult nature. Would you use this to argue
>that it should be impossible to obtain the offset of a structure member.
>Of course not.
>
>If a user uses WITH on one of your structs, then it is still extremely
>unlikely that your change will cause trouble.
>
>I really think that you need to give an example. Talking in generalities
>is always misleading. If you think something is dangerous don't just go
>around sounding red alert. Instead give a specific technical example :-)
>
>
Robert, we have different perspectives on the same problem. Obviously
issues I see as critical, you see as mute.
I've given examples. They still stand.
G
next prev parent reply other threads:[~2003-01-05 2:21 UTC|newest]
Thread overview: 42+ messages / expand[flat|nested] mbox.gz Atom feed top
2003-01-04 23:27 Robert Dewar
2003-01-04 23:36 ` Lynn Winebarger
2003-01-05 2:55 ` Gianni Mariani [this message]
-- strict thread matches above, loose matches on Subject: below --
2003-01-06 13:07 Robert Dewar
2003-01-05 18:41 Robert Dewar
2003-01-05 13:03 Robert Dewar
2003-01-05 13:39 ` Toon Moene
2003-01-05 12:56 Robert Dewar
2003-01-05 18:22 ` Joseph S. Myers
2003-01-05 12:56 Robert Dewar
2003-01-06 12:18 ` Andrew Haley
2003-01-05 12:44 Robert Dewar
2003-01-05 3:16 Robert Dewar
2003-01-05 0:38 Robert Dewar
2003-01-05 0:29 Robert Dewar
2003-01-05 0:37 ` Kevin Handy
2003-01-04 22:13 Robert Dewar
2003-01-04 20:59 Robert Dewar
2003-01-04 22:36 ` Gianni Mariani
2003-01-04 20:09 Robert Dewar
2003-01-04 19:36 Robert Dewar
2003-01-04 19:59 ` Tolga Dalman
2003-01-04 19:13 Robert Dewar
2003-01-04 20:58 ` Gianni Mariani
2003-01-04 18:11 Robert Dewar
2003-01-04 18:47 ` Gianni Mariani
2003-01-04 17:52 Robert Dewar
2003-01-04 17:59 ` Gianni Mariani
2003-01-04 17:06 Robert Dewar
2003-01-04 17:22 ` Daniel Berlin
2003-01-05 11:33 ` Andrew Haley
2003-01-05 11:36 ` Toon Moene
2003-01-04 14:29 Robert Dewar
2003-01-04 15:00 ` Momchil Velikov
2003-01-04 15:24 ` Andrew Haley
2003-01-04 16:25 ` Neil Booth
2003-01-04 17:35 ` Gianni Mariani
2003-01-04 17:59 ` Tolga Dalman
2003-01-04 18:36 ` Gianni Mariani
2003-01-04 18:54 ` Tolga Dalman
2003-01-04 23:32 ` Kevin Handy
2002-12-29 8:32 Norman Jonas
2002-12-29 12:46 ` Russ Allbery
2002-12-29 6:49 Erik Schnetter
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