[gentoo-user] Re: Qt-4.8.7 bug

[Jörg Schaible]

Hello Kai,

Kai Krakow wrote:

> Am Mon, 22 May 2017 19:33:55 +0200
> schrieb Jörg Schaible <joerg.schaible@×××.de>:
>
>> Peter Humphrey wrote:

[snip]

>> >
>> > I can only suggest you read bug report 618922 if you haven't
>> > already, including following its reference to bug 595618. It makes
>> > sense to me.
>>
>> It does not for me. My packages were already compiled with gcc-5.4.0.
>> Those Buzilla issues only talk about (plasma/qt) packages compiled
>> with previous gcc-4.x which are supposed to be incompatible. All of
>> the plasma/qt related packages that have been recompiled, because
>> they were built upon libQtCore.so.4 were already recompiled with
>> gcc5. I've checked my logs.
>
> Is the problem maybe order of building packages?
>
> From your description I see one edge case: Plasma could have been
> compiled with gcc-5 but linked to qt still built with gcc-4. Then, qt
> was rebuilt after this and is compiled by gcc-5 now.
>
> Without reading the bug report I would guess that is what the bug is
> about: Linking plasma against gcc-4 built qt binaries... Even when you
> rebuild qt with gcc-5 after this, you'd need to relink plasma.
>
> From your logs, you should see the order in which those packages were
> rebuilt and linked.
>
> revdep-rebuild is not always able to perfectly order packages right for
> emerge, and emerge in turn has no problem with wrong ordering because
> it is rebuilding packages and the dependency constraints are already
> fulfilled (read: runtime and build deps are already there). Portage
> does not consider rebuilds as a hard dependency/precondition for
> rebuilding other packages...
>
> As far as I understood, "--changed-deps" should fix this and also
> rebuild packages depending on the rebuilt packages _after_ they've been
> rebuilt.
>
> The "--empty" option would have a similar effect, tho rebuild many more
> packages.
>
> You could've tried if "revdep-rebuild ... -- --changed-deps" would've
> done anything better. I would be interested...

Too late now for this, but your assumption can be true. The rebuild for the 
gcc5 switch did not work smoothly because emerge failed to build all 515 
packages reported by revdep-rebuild in correct order. Especially the Kontact 
suite was affected, because emerge tried to build kdepim-common-libs before 
some of the dependent packages (happened to me on two different machines). A 
second run rebuilding only the failed stuff succeeded in the end, but that 
might have lead to the linker situation you've described above. I wonder, 
what else might still be affected :-/

Cheers,
Jörg