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List:       kde-devel
Subject:    Re: C++ exceptions
From:       Kevin Krammer <kevin.krammer () gmx ! at>
Date:       2005-12-08 12:40:53
Message-ID: 200512081340.53888.kevin.krammer () gmx ! at
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On Wednesday 07 December 2005 22:15, Volker Lukas wrote:
> Kevin Krammer wrote:
> > [...]
> >
> > If the application developer wants to deploy on Linux systems _and_ use
> > the systems Qt3 installation, he can safely assume it was built without
> > exceptions [...]
>
> This is in some way a chicken and egg problem: Programmers fear that Qt is
> built with -fno-exceptions, which puts them of from using exceptions. In
> consequence, the people building Qt packages are less compelled to give up
> this practice. This alone does not say much about whether it is a good or a
> bad practice.

Well, almost. Currently programmers can be almost certain that Qt3 is built 
without exceptions support and my guess is this is not going to change as 
pretty all software developed for it depends on that.

> > [...] because of the problems earlier GCC versions had with them and
> > so most (all+) software assumes -fno-exceptions
>
> I use an older release series myself (3.3.x) and exception support creates
> much less problems than support for some other C++ features.
>
> This release series is binary compatible to GCC 3.2, if I recall correctly.
> GCC 3.2 has been released in August 2002. This means users of GCC releases
> from that time on can easily upgrade their release to an "unproblematic"
> version. The intermediary releases 3.0.0 - 3.1.1 were not adopted widely.
> So the preceding release series was GCC 2.95, with the first release in
> July 1999 (last March 2001). This means that the "problematic" compiler is
> basically 6 years old. I do not think that it is reasonable to hold
> progress back, just to cater for such an old compiler.

The problem is not the currently used compiler version, but the one used when 
the software was created.
Just because the modern versions of GCC can handle exceptions nicely does not 
automatically make all code safe to use them.

If a distributor switches to a new compiler, their developers will likely test 
which newly available options they can activate _without_ breaking the 
software they intend to ship.

If enabling exceptions in libqt3 breaks ~100% of the Qt3 applications they 
package, the chance of libqt3 compiled with exceptions is quite low.

It's all a matter of compatability.

Cheers,
Kevin

-- 
Kevin Krammer <kevin.krammer@gmx.at>
Qt/KDE Developer, Debian User
Moderator: www.mrunix.de (German), www.qtforum.org

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