Re: [PATCH 02/14] gnu: Add qtimageformats.

[Efraim Flashner]

On Sun, Jun 12, 2016 at 04:12:21PM +0200, Andreas Enge wrote:
> On Fri, Jun 10, 2016 at 12:30:45PM -0400, Leo Famulari wrote:
> > On Fri, Jun 10, 2016 at 03:10:13PM +0300, Efraim Flashner wrote:
> > > +(define-public qtimageformats
> > > +  (package (inherit qtsvg)
> > These patches make me realize my understanding of package inheritance is
> > unclear.
> > 
> > If qtsvg is updated, but no other changes are made, will qtimageformats
> > (and all the other packages that inherit from qtsvg) need to be rebuilt
> > as well?
> > 
> > Looking at `guix refresh -l` and `guix gc --references` suggests the
> > answer is "no".
> 
> My understanding is that not the package definition, but the derivation
> counts. So for instance, if the version is increased in qtsvg, this new
> version also appears in qtimageformats, but if it is set back there, not
> even the package definition has changed.
> 
> So this should be safe; in a sense, the inheritance from qtsvg creates a
> "qt build system"; since this is so far only used internally to build qt
> itself, I think it is okay to not expose it to the exterior world.
> 
> However, another question: Are all the inputs for qtbase needed for all the
> other modules, too, or could the list be trimmed?
> 
> Andreas
> 

quite possibly the inputs could be shortened, but since they're all
using qmake for configure I don't really know how to check. The best I
have for cross-distro comparison is debian:
$ apt-cache depends libqt5svg5
libqt5svg5
PreDepends: dpkg
dpkg:i386
Depends: libc6
Depends: libqt5core5a
Depends: libqt5gui5
Depends: libqt5widgets5
Depends: libstdc++6
Depends: <qtbase-abi-5-5-1>
Depends: zlib1g

I don't think I've seen anything like <qtbase-abi-5-5-1> before, but I'm
assuming its the list of inputs/depends that qtbase-5.5.1 uses in
Debian. qtcore, qtgui and qtwidgets are all outputs of qtbase.

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