1.5.517: "QWidget: Cannot create a QWidget without QApplication"

[VVD]

Description

During run print in console and exit:

<X>2023-08-12 12:49:06.486 Loading settings from "/home/USER/.config/Mumble/Mumble/mumble_settings.json"
<F>2023-08-12 12:49:06.488 QWidget: Cannot create a QWidget without QApplication

Steps to reproduce

1. Build with options:
   bundled-gsl client oss overlay overlay-xcompile plugins translations xinput2 dbus lto
   or
   bundled-gsl client oss overlay overlay-xcompile plugins translations xinput2 lto rnnoise speechd
2. Run.

Mumble version

1.5.517

Mumble component

Client

OS

FreeBSD

Reproducible?

Yes

Additional information

Downstream bug report: https://bugs.freebsd.org/bugzilla/show_bug.cgi?id=273078

# pkg info -q | grep ^qt5
qt5-3d-5.15.8p0
qt5-assistant-5.15.8p1
qt5-buildtools-5.15.8p157
qt5-charts-5.15.8p0
qt5-concurrent-5.15.8p157
qt5-connectivity-5.15.8p5
qt5-core-5.15.8p157_1
qt5-dbus-5.15.8p157
qt5-declarative-5.15.8p21
qt5-declarative-test-5.15.8p21
qt5-designer-5.15.8p1
qt5-graphicaleffects-5.15.8p0
qt5-gui-5.15.8p157_2
qt5-help-5.15.8p1
qt5-imageformats-5.15.8p6_2
qt5-l10n-5.15.8p0
qt5-linguist-5.15.8p1
qt5-linguisttools-5.15.8p1
qt5-location-5.15.8p3
qt5-multimedia-5.15.8p1_1
qt5-network-5.15.8p157
qt5-networkauth-5.15.8p0
qt5-opengl-5.15.8p157
qt5-printsupport-5.15.8p157
qt5-qdbus-5.15.8p1
qt5-qdoc-5.15.8p1
qt5-qdoc-data-5.15.8
qt5-qmake-5.15.8p157_2
qt5-qtpaths-5.15.8p1
qt5-quick3d-5.15.8p1
qt5-quickcontrols-5.15.8p0
qt5-quickcontrols2-5.15.8p7
qt5-remoteobjects-5.15.8p0
qt5-script-5.15.11p0
qt5-scripttools-5.15.11p0
qt5-sensors-5.15.8p0
qt5-serialport-5.15.8p0
qt5-speech-5.15.8p1_1
qt5-sql-5.15.8p157
qt5-sqldrivers-sqlite3-5.15.8p157
qt5-svg-5.15.8p8
qt5-testlib-5.15.8p157
qt5-uiplugin-5.15.8p1
qt5-uitools-5.15.8p1
qt5-virtualkeyboard-5.15.8p0
qt5-wayland-5.15.8p57
qt5-webchannel-5.15.8p3
qt5-webengine-5.15.8_5
qt5-webkit-5.212.0.a4_14
qt5-websockets-5.15.8p2
qt5-webview-5.15.8p0_1
qt5-widgets-5.15.8p157
qt5-x11extras-5.15.8p0
qt5-xml-5.15.8p157
qt5-xmlpatterns-5.15.8p0

# pkg info -q | grep ^plasma
plasma-wayland-protocols-1.10.0
plasma5-breeze-5.27.7
plasma5-breeze-gtk-5.27.7
plasma5-discover-5.27.7
plasma5-drkonqi-5.27.7
plasma5-kactivitymanagerd-5.27.7
plasma5-kde-cli-tools-5.27.7
plasma5-kde-gtk-config-5.27.7
plasma5-kdecoration-5.27.7
plasma5-kdeplasma-addons-5.27.7
plasma5-kgamma5-5.27.7
plasma5-khotkeys-5.27.7
plasma5-kinfocenter-5.27.7
plasma5-kmenuedit-5.27.7
plasma5-kscreen-5.27.7
plasma5-kscreenlocker-5.27.7
plasma5-ksshaskpass-5.27.7
plasma5-ksysguard-5.22.0_4
plasma5-ksystemstats-5.27.7
plasma5-kwallet-pam-5.27.7
plasma5-kwayland-integration-5.27.7
plasma5-kwin-5.27.7
plasma5-kwrited-5.27.7
plasma5-layer-shell-qt-5.27.7
plasma5-libkscreen-5.27.7
plasma5-libksysguard-5.27.7
plasma5-milou-5.27.7
plasma5-oxygen-5.27.7
plasma5-plasma-5.27.7
plasma5-plasma-browser-integration-5.27.7
plasma5-plasma-desktop-5.27.7.1
plasma5-plasma-disks-5.27.7
plasma5-plasma-integration-5.27.7
plasma5-plasma-sdk-5.27.7.1
plasma5-plasma-workspace-5.27.7
plasma5-plasma-workspace-wallpapers-5.27.7
plasma5-polkit-kde-agent-1-5.27.7
plasma5-powerdevil-5.27.7
plasma5-sddm-kcm-5.27.7
plasma5-systemsettings-5.27.7
plasma5-xdg-desktop-portal-kde-5.27.7

Relevant log output

No response

Screenshots

No response

[VVD]

This line in main.cpp "fails": ApplicationPalette applicationPalette;

[VVD]

With option lto off work fine.

[davidebeatrici]

Thank you for investigating.

MumbleApplication is our QApplication and is instantiated quite early in main() (before ApplicationPalette anyway).

We should try to reproduce the issue with a basic program.

[Krzmbrzl]

With option lto off work fine.

Ouch. That most likely means we have some undefined behavior somewhere 👀

[VVD]

Tried to build with llvm13 from base FreeBSD 13.2 and devel/llvm15 from ports - same result.
Maybe some sort of optimization breaks this…

[VVD]

llvm/llvm-project#45814
InBetweenNames/gentooLTO#444

[Krzmbrzl]

Oh that's interesting.
@VVD if I understood the linked issues correctly, tbough it seems like it should be fixed in Clang 12+. However, that doesn't seem to be what you observed, right?

[VVD]

Look like it's still issue for Qt5 applications with LTO.

[Krzmbrzl]

I'll close this as there doesn't seem to be much we can do to work around what seemingly is a compiler bug 👀