'undefined reference' after autofilereloader commit

[mccowanm]

Bug Description

Hello,
After 45363b7 builds no longer work against main, failing when linking the mixxx executable with the errors below.
Fresh builds (on Gentoo x86, QT 6.7.2) on prior commits run to completion.
Unfortunately I don't have the Qt skills to attempt a patch.

Many thanks for a great piece of software
Matt

/usr/lib/gcc/x86_64-pc-linux-gnu/13/../../../../x86_64-pc-linux-gnu/bin/ld: libmixxx-qml-lib.a(qmlapplication.cpp.o): in function `mixxx::qml::QmlApplication::~QmlApplication()':
/home/matt/mixxx/src/qml/qmlapplication.cpp:80:(.text+0x11c6): undefined reference to `vtable for AutoFileReloader'
/usr/lib/gcc/x86_64-pc-linux-gnu/13/../../../../x86_64-pc-linux-gnu/bin/ld: libmixxx-qml-lib.a(qmlapplication.cpp.o): in function `AutoFileReloader::~AutoFileReloader()':
/home/matt/mixxx/src/util/autofilereloader.h:9:(.text._ZN16AutoFileReloaderD2Ev[_ZN16AutoFileReloaderD5Ev]+0x1c): undefined reference to `vtable for AutoFileReloader'
/usr/lib/gcc/x86_64-pc-linux-gnu/13/../../../../x86_64-pc-linux-gnu/bin/ld: libmixxx-qml-lib.a(qmlapplication.cpp.o): in function `AutoFileReloader::~AutoFileReloader()':
/home/matt/mixxx/src/util/autofilereloader.h:9:(.text._ZN16AutoFileReloaderD0Ev[_ZN16AutoFileReloaderD5Ev]+0x1c): undefined reference to `vtable for AutoFileReloader'
/usr/lib/gcc/x86_64-pc-linux-gnu/13/../../../../x86_64-pc-linux-gnu/bin/ld: libmixxx-qml-lib.a(qmlautoreload.cpp.o): in function `mixxx::qml::QmlAutoReload::QmlAutoReload()':
/home/matt/mixxx/src/qml/qmlautoreload.cpp:15:(.text+0x234c): undefined reference to `AutoFileReloader::AutoFileReloader(RuntimeLoggingCategory const&)'
/usr/lib/gcc/x86_64-pc-linux-gnu/13/../../../../x86_64-pc-linux-gnu/bin/ld: /home/matt/mixxx/src/qml/qmlautoreload.cpp:17:(.text+0x236e): undefined reference to `AutoFileReloader::fileChanged(QString const&)'
/usr/lib/gcc/x86_64-pc-linux-gnu/13/../../../../x86_64-pc-linux-gnu/bin/ld: libmixxx-qml-lib.a(qmlautoreload.cpp.o): in function `QMetaObject::Connection QObject::connect<void (AutoFileReloader::*)(QString const&), void (mixxx::qml::QmlAutoReload::*)()>(QtPrivate::FunctionPointer<void (AutoFileReloader::*)(QString const&)>::Object const*, void (AutoFileReloader::*)(QString const&), QtPrivate::ContextTypeForFunctor<void (mixxx::qml::QmlAutoReload::*)(), void>::ContextType const*, void (mixxx::qml::QmlAutoReload::*&&)(), Qt::ConnectionType)':
/usr/include/qt6/QtCore/qobject.h:263:(.text+0x23d6): undefined reference to `AutoFileReloader::staticMetaObject'
/usr/lib/gcc/x86_64-pc-linux-gnu/13/../../../../x86_64-pc-linux-gnu/bin/ld: libmixxx-qml-lib.a(qmlautoreload.cpp.o): in function `non-virtual thunk to mixxx::qml::QmlAutoReload::~QmlAutoReload()':
/home/matt/mixxx/src/qml/qmlautoreload.h:11:(.text._ZN5mixxx3qml13QmlAutoReloadD2Ev[_ZN5mixxx3qml13QmlAutoReloadD5Ev]+0x2f): undefined reference to `vtable for AutoFileReloader'
/usr/lib/gcc/x86_64-pc-linux-gnu/13/../../../../x86_64-pc-linux-gnu/bin/ld: libmixxx-qml-lib.a(qmlautoreload.cpp.o): in function `mixxx::qml::QmlAutoReload::~QmlAutoReload()':
/home/matt/mixxx/src/qml/qmlautoreload.h:11:(.text._ZN5mixxx3qml13QmlAutoReloadD2Ev[_ZN5mixxx3qml13QmlAutoReloadD5Ev]+0x44f): undefined reference to `vtable for AutoFileReloader'
/usr/lib/gcc/x86_64-pc-linux-gnu/13/../../../../x86_64-pc-linux-gnu/bin/ld: libmixxx-qml-lib.a(qmlautoreload.cpp.o): in function `non-virtual thunk to mixxx::qml::QmlAutoReload::~QmlAutoReload()':
/home/matt/mixxx/src/qml/qmlautoreload.h:11:(.text._ZN5mixxx3qml13QmlAutoReloadD0Ev[_ZN5mixxx3qml13QmlAutoReloadD5Ev]+0x33): undefined reference to `vtable for AutoFileReloader'
/usr/lib/gcc/x86_64-pc-linux-gnu/13/../../../../x86_64-pc-linux-gnu/bin/ld: libmixxx-qml-lib.a(qmlautoreload.cpp.o): in function `mixxx::qml::QmlAutoReload::~QmlAutoReload()':
/home/matt/mixxx/src/qml/qmlautoreload.h:11:(.text._ZN5mixxx3qml13QmlAutoReloadD0Ev[_ZN5mixxx3qml13QmlAutoReloadD5Ev]+0x45f): undefined reference to `vtable for AutoFileReloader'

Version

34dde6f

OS

gentoo

[acolombier]

src/qml/qmlautoreload.cpp:15:(.text+0x234c): undefined reference to `AutoFileReloader::AutoFileReloader(RuntimeLoggingCategory const&)

Looks like the signal symbol is not autogen correctly. What's strange is your are using 45363b7 but the QML file loader (introducing the AutoFileReloader changes) was only merged one commit after. Could you try with 21f4c88? Also, may I ask you to try with a clean build as well?

[Swiftb0y]

thats, weird. I'll try to look into it.

[Swiftb0y]

@mccowanm unfortunately I can't reproduce locally. Nevertheless, I did forget to declare a virtual destructor explicitly, so that may be the issue. Can you please try a clean build and additionally #13756?

[Swiftb0y]

Actually, this is failing to link libmixxx-qml-lib. I have QML=OFF locally unfortunately due to (imo) broken fedora packages.

I think I figured it out. 707a08f

Shouldn't this have been caught by the CI though?

[acolombier]

Shouldn't this have been caught by the CI though?

This doesn't seem to occur on Qt 6.2.4 with QML=ON, which is the Qt version used by our 22.04 runner. I guess we could soon consider adding 24.04 runners, thought they are only using Qt 6.4.

[Swiftb0y]

I don't think the qt version matters much. The problem is simply that qmlfilereloader depends on autoreloader, but the latter was not getting linked to the former because the former is part of a different target. I didn't catch this at that time because due to the packaging issues, I'm currently not building the qml target, but those linker errors should've been caught by CI which does build it.

[acolombier]

As I said I cannot reproduce it either, so I don't think it's fair to expect the CI to catch those either. This means that there is something else that seems to come in the equation.
As the original logs, the symbol to the signal was missing, a symbol generated by autogen AFAIK, thus why I suggested the Qt version.

[Swiftb0y]

I think its the entire vtable

/home/matt/mixxx/src/qml/qmlapplication.cpp:80:(.text+0x11c6): undefined reference to `vtable for AutoFileReloader'

But anyways. Pretty sure its fixed by 707a08f. @mccowanm could you do us a favor and test that since no else can currently reproduce this commit?

[pvagner]

Hello,
I am on arch-linux with qt6 6.7.3 and I also need this commit in order to link successfully.
Thanks for looking into it.

[Swiftb0y]

Thank you for confirming.

[daschuer]

Launchpad has also caught the issue:
https://launchpad.net/~mixxx/+archive/ubuntu/nightlies/+packages

I was pinged by it but have not instantly found the failing error message which is on line 9523 of 9685. We have also the issue that Launchpad build fails now and then because of stalled tests. So I did a rebuild as a first try.

Unlike on Launchpad we use mold as linker on GitHub? This probably manage to find the missing reference in the final link stage.

@Swiftb0y I think you can in addition remove src/util/autofilereloader.cpp from mixxx-lib

[fwcd]

Ran into the same issue with my mostly static Linux build, but wasn't sure if this was some issue with my unusual build environment. CI seems to have reproduced it reliably for the past few days: https://github.com/fwcd/m1xxx/actions/runs/11310446122/job/31455509966

[Swiftb0y]

I think you can in addition remove src/util/autofilereloader.cpp from mixxx-lib

I could in theory, though the purpose of the autofilereloader is to be used outside of QML. So when someone eventually incorporates it into the mixxx-lib, we'll repeat this same debacle again. So I would prefer to keep it in both because I don't see any downside to it tbh.

[daschuer]

I don't agree. We should only add currently required link scripts to libraries to avoid to have two time the same function in the linker resources. I think this debacle is an indicator that our library structure is not yet correct. We have a criss cross dependency between mixxx-lib and mixxx-qml-lib which need to be solved.
Since QML will allways be defined in main, maybe it would be staright forward to retire that flag?
Alternative would be to add a new independent lib for all these QML/Widget less classes-

[Swiftb0y]

I agree that we should start separating mixxx into smaller modules.

We have a criss cross dependency between mixxx-lib and mixxx-qml-lib which need to be solved.

I think this is technically more similar to a diamond dependency problem. Why is this a problem? I would expect the linker to deduplicate symbols used multiple times.

[fwcd]

If we still have a way of building the GUI without QML it would be really useful to keep that flag IMO, if only for testing purposes.

[Swiftb0y]

I agree, especially since its currently broken (for me) on fedora 40.

[mccowanm]

707a08f does indeed fix a build on Gentoo thanks @Swiftb0y