[Development] Co-installation & library naming rules

[Ziller Eike]

On 23 Sep 2012, at 20:30, Erik van Pienbroek <erik at vanpienbroek.nl> wrote:

> Thiago Macieira schreef op vr 21-09-2012 om 16:47 [+0200]:
>> Include the major version number (5) in all library base names
> 
> Hi,
> 
> As the person who filed the mentioned QT-BUG in the first place I would
> like to let you know that I'm +1 to the proposal from Thiago. For the
> people who don't know me yet: I'm a member of the Fedora MinGW group and
> we provide cross-compiled binaries of Qt for the win32 and win64 targets
> so users can easily cross-compile their software on a Linux host and run
> them on Windows (or Wine).
> 
> On IRC I've been discussing this subject with Kevin Kofler (Fedora KDE
> group) and he also +1's the proposal from Thiago
> 
> Some days ago I started on packaging the entire Qt5 stack and stumbled
> across the fact that by default Qt4 and Qt5 can't be installed in the
> same prefix as there are various file name conflicts. Therefore I had to
> do some additional patching (like
> https://codereview.qt-project.org/34981 ) and manual renames to make it
> possible to co-install Qt4 and Qt5. The resulting packages can be found
> at https://bugzilla.redhat.com/showdependencytree.cgi?id=3D858058
> 
> The reason why we want to be able to co-install Qt4 and Qt5 is because
> all packages in Fedora are expected to follow the FHS as close as
> possible and the packaging rules state that no packages are allowed to
> conflict with each other.

"- unversioned applications, like assistant, linguist, qdbus,
		  qdbusviewer"

Wouldn't that also conflict this rule? Or are these expected to be in its own package separate from the "versioned" parts of Qt?

> A suggestion was made in this thread that distro's should use separate
> prefixes to install Qt4 and Qt5. This will be a no-go as in that
> situation you will force all users of Qt4 or Qt5 to apply
> distribution-specific hacks to get their Qt-using application built.
> Examples of these hacks are:
> 
> For qmake:
> - Users having to manually call $some_random_prefix/bin/qmake to select
> either Qt4 or Qt5 instead of having the qmake binary available in their
> default path
> 
> For pkg-config:
> - Manually setting PKG_CONFIG_PATH to point to the pkg-config folder
> where either the Qt4 or Qt5 pkg-config files are stored
> 
> As mentioned earlier in this thread the gtk folks have been using
> versioned library names for a very long time already and due to this the
> introduction of gtk3 itself was quite painless (just speaking about gtk3
> here, not gnome3). All gtk-using packages are supposed to use pkg-config
> to detect the compiler flags for gtk. The gtk2 library has been
> providing a pkg-config file named 'gtk+-2.0.pc' and the gtk3 library is
> providing a pkg-config file named' gtk+-3.0.pc'. As these names don't
> conflict all gtk2-using packages rebuilt fine even when gtk3 is
> installed. Packages which want to use gtk3 can indicate so by using
> pkg-config to check for 'gtk+-3.0'.
> 
> In my opinion the Qt project should make it possible to co-install Qt4
> and Qt5 in the same prefix. If the Qt project refuses to do so then this
> will result in distributions applying random patches to get Qt5 working
> correctly on their distribution. This will lead to more
> distribution-specific hacks and will make it more hard for you guys to
> diagnose and resolve bugs (as you're not aware of distribution-specific
> patches). Now various distributions could start a collaboration to come
> to uniform packaging guidelines for the Qt package (naming of qmake,
> installation location, etc..) but why not solve the problem at the level
> where it's supposed to be fixed, upstream?
> 
> I don't think it's fair to move the problem to the distributions. If the
> library name stays as is you're forcing a lot of additional work on us
> package maintainers while it can be resolved quite easily and now is the
> perfect time to do so (right before the release of a major new version
> of Qt)
> 
> Kind regards,
> 
> Erik van Pienbroek
> Fedora MinGW SIG
> 
> 
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