Re: [gentoo-user] useflag hell.

[Alan McKinnon <alan.mckinnon@gmail.com>]

On 28/02/2016 20:14, Alan Grimes wrote:
> I've been running number theory code for a few weeks, so haven't been
> updating my machine too often...
> 
> I for the last day or so I'm in a run my "pretendupdate" script, look at
> the results, decide whether to run ufed or bleep with package.use....
> run the pretendupdate script again, do something while it computes, come
> back to it hours later, and repeat the cycle... This is really getting
> silly and I'm starting to suspect that I'm stuck in useflag hell and
> there isn't a solution to this.


There's always a solution, and they are seldom hard to solve. However,
portage doesn't exactly make it easy for you with the output. Mere
information is often obfuscated and looks like stuff you must fix,
whereas the real nuggets can be hidden in the noise.

Often running without -v can help considerably.

So, here goes, comments inline
> 
> 
> 
> 
> tortoise ~ # ./pretendupdate
> 
> These are the packages that would be merged, in order:
> 
> Calculating dependencies... done!
> 
> !!! Multiple package instances within a single package slot have been pulled
> !!! into the dependency graph, resulting in a slot conflict:
> 
> dev-libs/icu:0
> 
>   (dev-libs/icu-56.1:0/56::gentoo, ebuild scheduled for merge) pulled in by
>     (no parents that aren't satisfied by other packages in this slot)
> 
>   (dev-libs/icu-55.1:0/55::gentoo, installed) pulled in by
>     dev-libs/icu:0/55=[abi_x86_32(-),abi_x86_64(-)] required by
> (dev-qt/qtcore-4.8.7-r1:4/4::gentoo, installed)
>                
> ^^^^^^  

Despite what it looks like all this is mere information.
Two separate things result in different version of Qt being pulled into
the problem solution. And it's exactly the form you'd expect.

The first chunk is really saying that icu-56.1 is the most recent
version and all other things being equal, that's the one portage would
install. The second chunk is saying that qtcore-4.8.7-r1 requires
icu-55.1 (not the most recent), so portage spews forth heaps of junk to
helpfully let you not figure it out.

What portage really should say is more like:

Most recent version of icu (icu-56.1) not installed due to these
requirements:
qtcore-4.8.7-r1 requires icu-55.1

Ignore the multiple OMG! bangs before all of the above output


> 
> 
> 
> It may be possible to solve this problem by using package.mask to
> prevent one of those packages from being selected. However, it is also
> possible that conflicting dependencies exist such that they are
> impossible to satisfy simultaneously.  If such a conflict exists in
> the dependencies of two different packages, then those packages can
> not be installed simultaneously.
> 
> For more information, see MASKED PACKAGES section in the emerge man
> page or refer to the Gentoo Handbook.
> 
> 
> !!! The ebuild selected to satisfy
> ">=media-libs/mlt-0.9.8-r1[ffmpeg,kdenlive,melt,qt5,sdl,xml]" has unmet
> requirements.

This is the expression portage needs to install based on dependencies,
most recent version, maskings, and your USE flags. It's informational.

> - media-libs/mlt-0.9.8-r2::gentoo USE="ffmpeg fftw gtk kde kdenlive lua
> melt opengl python qt5 sdl xine xml -compressed-lumas -debug -frei0r
> -jack -libav -libsamplerate -qt4 -rtaudio (-ruby) -vdpau" ABI_X86="64"
> CPU_FLAGS_X86="mmx sse sse2" PYTHON_TARGETS="python2_7"
> 
>   The following REQUIRED_USE flag constraints are unsatisfied:
>     kde? ( qt4 )

This is the actual problem, According to the ebuild, if you set
USE="kde", then you also need USE="qt4". Your USE has qt5 enabled, and
that's the problem.

Presumably, mtl does not yet support KDE with Qt5
> 
>   The above constraints are a subset of the following complete expression:
>     python? ( python_targets_python2_7 ) qt5? ( !qt4 ) kde? ( qt4 )

And this is the helpful gigantic USE expression, all of which must be
satisfied to install mlt. The bit above this shows just the part that is
problematic, so this is also informational. Note
> 
> (dependency required by "kde-apps/kdenlive-15.12.1::gentoo" [ebuild])
> (dependency required by "kde-apps/kdemultimedia-meta-15.12.1-r1::gentoo"
> [ebuild])
> (dependency required by "kde-apps/kde-apps-meta-15.08.3-r3::gentoo"
> [ebuild])
> (dependency required by "kde-apps/kde-meta-15.08.3::gentoo" [ebuild])
> (dependency required by "@selected" [set])
> (dependency required by "@world" [argument])

And the is a part of the full dep tree that leads to mlt being included
> tortoise ~ #
> 
> 
> ######################
> 
> 
> The attached files are whatever is left after --- six years of resolving
> similar issues on this same install...


What you need to do now is set one of the following combinations in
package.use for mlt:

USE=-kde qt4 -qt5
USE=kde qt4 -qt5

On a plasma system like you have this will probably cause similar issues
for other packages, so you must iteratively solve those as well till no
more inconsistencies remain.

Portage does an atrocious job of presenting it's output to you, but
essentially it's a problem in graph theory and detecting mutually
incompatible data.


-- 
Alan McKinnon
alan.mckinnon@gmail.com