Arch Linux

is not only lazarus-qt5 but all program qt make with lazarus
what's weird is that qt5 programs written with lazarus don't have this problem with xfce

as doublecmd-qt5
PollThread: Finish polling
An unhandled exception occurred at $00007F54FB83936E:
EAccessViolation:
$00007F54FB83936E in /usr/lib/libQt5Core.so.5

Just tested with doublecmd, no issue closing

doublecmd

(doublecmd:12033): Gtk-WARNING **: 18:08:58.397: Unable to locate theme engine in module_path: "adwaita",

(doublecmd:12033): Gtk-WARNING **: 18:08:58.397: Unable to locate theme engine in module_path: "adwaita",

(doublecmd:12033): Gtk-WARNING **: 18:08:58.399: Unable to locate theme engine in module_path: "murrine",

(doublecmd:12033): Gtk-WARNING **: 18:08:58.399: Unable to locate theme engine in module_path: "murrine",

(doublecmd:12033): Gtk-WARNING **: 18:08:58.399: Unable to locate theme engine in module_path: "murrine",

(doublecmd:12033): Gtk-WARNING **: 18:08:58.400: Unable to locate theme engine in module_path: "murrine",

(doublecmd:12033): Gtk-WARNING **: 18:08:58.400: Unable to locate theme engine in module_path: "murrine",

(doublecmd:12033): Gtk-WARNING **: 18:08:58.400: Unable to locate theme engine in module_path: "murrine",

(doublecmd:12033): Gtk-WARNING **: 18:08:58.400: Unable to locate theme engine in module_path: "murrine",

(doublecmd:12033): Gtk-WARNING **: 18:08:58.400: Unable to locate theme engine in module_path: "murrine",

(doublecmd:12033): Gtk-WARNING **: 18:08:58.400: Unable to locate theme engine in module_path: "murrine",

(doublecmd:12033): Gtk-WARNING **: 18:08:58.400: Unable to locate theme engine in module_path: "murrine",

(doublecmd:12033): Gtk-WARNING **: 18:08:58.401: Unable to locate theme engine in module_path: "murrine",
Starting GuiMessageQueue
Starting Double Commander
Double Commander 0.8.3 beta
Revision: 8160
Build: 2018/06/04
Lazarus: 1.8.2.0
Free Pascal: 3.0.4
Platform: x86_64-Linux-qt5
System: Arch Linux
Desktop Environment: Unknown
Widgetset library: Qt 5.11.0, libQt5Pas 5.6.1
This program is free software released under terms of GNU GPL 2
(C)opyright 2006-2017 Alexander Koblov (alexx2000@mail.ru)
and contributors (see about dialog)
Executable directory: /usr/lib/doublecmd/
Loading configuration from /home/ike/.config/doublecmd/
WDX: LOAD: /usr/lib/doublecmd/plugins/wdx/rpm_wdx/rpm_wdx.wdx
WDX: LOAD: /usr/lib/doublecmd/plugins/wdx/deb_wdx/deb_wdx.wdx
WDX: LOAD: /usr/lib/doublecmd/plugins/wdx/audioinfo/audioinfo.wdx
Error loading configuration file /home/ike/.config/doublecmd/favoritetabs.xml
PollThread: Start polling
PollThread: AddPoll 11
Creating PixmapManager
Loading icon theme Hicolor
Loading icon theme Hicolor
Loading icon theme DCTheme
Loading icon theme DCTheme
PollThread: AddPoll 15
UDev: Begin monitoring
Detecting mounts through /proc/self/mounts
PollThread: AddPoll 16
TColumnsFileView.Create components
Creating TFileSystemFileSource
TColumnsFileView.Create components
FileSystemWatcher thread starting
frmMain.frmMainShow
PollThread: RemovePoll 11
PollThread: AddPoll 11
Finished Double Commander
Destroying main form
Drive watcher finished
Waiting for workers thread 0000000002751648
Finalized workers thread 0000000002751648
Waiting for FileSystemWatcher thread
FileSystemWatcher thread finished
Waiting for workers thread 0000000002752488
Finalized workers thread 0000000002752488
Destroying TFileSystemFileSource when refcount=0
Main form destroyed
Finishing GuiMessageQueue
Shutting down PixmapManager
PollThread: RemovePoll 11
PollThread: Finish polling

with qt 5.11.0

@papajoke could you give more information in what environment you are starting these?

what WM/DE, maybe other configuration related to QT

arch stable updated (today with last qt-base 5.11.1-1)

for me it's not QT but plasma (not wayland) !
with plasma : same bug with my acount and a fresh new user (created only for this test)
with jwm my same account as plasma (same partition/packages/kernel/home as plasma) : no bug, doublecmd close well

my plasma account env :
grep -Ei "qt|kde|plasma"
QT_LOGGING_RULES=*=false
KDE_SESSION_VERSION=5
KDE_SESSION_UID=1000
DESKTOP_SESSION=/usr/share/xsessions/plasma
XDG_SESSION_DESKTOP=KDE
QT_AUTO_SCREEN_SCALE_FACTOR=0
XDG_CURRENT_DESKTOP=KDE
KDE_FULL_SESSION=true

my jwm account env :
grep -Ei "qt|kde|plasma"
QT_LOGGING_RULES=*=false


With my plasma : same bug with brize and oxygen / with global menus and not / with menu in caption and not

-----
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I have create a empty qt5 program with lazarus, same bug as doublecmd ( in /usr/lib/libQt5Core.so.5)

begin
Writeln('App start');

RequireDerivedFormResource:=True;
Application.Initialize;
Application.CreateForm(TForm1, Form1);
Application.Run;

Writeln ('App end');
Writeln ('desktop: '+ fpgetenv('XDG_CURRENT_DESKTOP'));
Writeln ('session: '+ fpgetenv('DESKTOP_SESSION'));
Writeln ('Process: '+ IntToStr(GetProcessID));
end.

gdb:
Starting program: /home/Data/Patrick/workspace/lazarus/test2/test --no-daemon --verbose
[Thread debugging using libthread_db enabled]
Using host libthread_db library "/usr/lib/libthread_db.so.1".
[New Thread 0x7fffea713700 (LWP 4508)]
[New Thread 0x7fffdc20f700 (LWP 4509)]
App start
FormCreate
[New Thread 0x7fffcc927700 (LWP 4510)]
FormClose
App end
desktop: KDE
session: /usr/share/xsessions/plasma
Process: 4503
Heap dump by heaptrc unit
1122 memory blocks allocated : 1597232/1599088
1122 memory blocks freed : 1597232/1599088
0 unfreed memory blocks : 0
True heap size : 589824
True free heap : 589824
[Thread 0x7fffcc927700 (LWP 4510) exited]

Thread 1 "test" received signal SIGSEGV, Segmentation fault.
0x00007ffff532f45e in QMetaCallEvent::QMetaCallEvent(QtPrivate::QSlotObjectBase*, QObject const*, int, int, int*, void**, QSemaphore*) () from /usr/lib/libQt5Core.so.5

Ok
XDG_CURRENT_DESKTOP

if i unset all env KDE it's ok or change only XDG_CURRENT_DESKTOP=PLASMA is ok :

if i add XDG_CURRENT_DESKTOP=KDE , i have a crash, and program not killed ! ?

to reproduce:
$ XDG_CURRENT_DESKTOP=KDE doublecmd

BUT
if i change XDG_CURRENT_DESKTOP, theme used by qt program is not plasma but gtk ! so not the solution

https://bugs.freepascal.org/view.php?id=33667

I don't see this issue anymore running the latest plasma desktop (non-testing) with the last lazarus-qt5 package