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IDProjectCategoryView StatusLast Update
0033667LazarusWidgetsetpublic2020-05-06 21:33
ReporterReinhard Berger Assigned ToZeljan Rikalo  
Status resolvedResolutionno change required 
Product Version1.8.3 (SVN) 
Summary0033667: Exception-Klasse »External: SIGSEGV
DescriptionError Box Exception at Adress 7FFFF531CC17 happens when program is compiled for Qt5 and option "dQT_NATIVE_DIALOGS" is enabled.
Note : It happens when calling the native KDE Dialogs only.
By using the Qt own ones this does not happen.

Exception always happens after calling the KDE Native Dialogs (this works without exceptions) but happens when the program get closed.
Steps To Reproduce1.) Put a TOpenDialog to a blank form.
2.) Put a Button on it.
3.) Call OpenDialog1.Execute
4.) Compile with "dQT_NATIVE_DIALOGS"
5.) Execute Program , click button to open the KDE Dialog.
6.) Close Program.
7.) Exception happens.
TagsNo tags attached.
Fixed in Revision
Attached Files


related to 0036019 resolvedZeljan Rikalo Qt5 programs on exit terminated with Segmentation fault 
related to 0037029 new Using TOpenDialog results in SIGESGV when program closed 


Reinhard Berger

2018-07-07 21:09

reporter   ~0109282

Must have something to do with kubuntu 18.04
It does not appear on 16.04 as well as kde neon and also not on lubuntu qt even if it uses the new pcmanfm filedialogs.
Maybe some KDE bug ?

Juha Manninen

2018-07-07 23:39

developer   ~0109285

For me it happens when closing any application built with QT5. QT_NATIVE_DIALOGS does not need to be defined.
I am running Manjaro Linux which has recent library versions.
I remember Zeljko also experienced it with a new Fedora version. It was mentioned in some mailing list post but I did not find it now.

> Maybe some KDE bug ?
No, LCL bindings only use QT. This is about some interaction betweeen recent QT5 and the bindings code.

--- debugger backtrace ---

Thread 1 "project1" received signal SIGSEGV, Segmentation fault.
0x00007ffff532f45e in QMetaCallEvent::QMetaCallEvent(QtPrivate::QSlotObjectBase*, QObject const*, int, int, int*, void**, QSemaphore*) () from /usr/lib/
(gdb) bt
#0 0x00007ffff532f45e in QMetaCallEvent::QMetaCallEvent(QtPrivate::QSlotObjectBase*, QObject const*, int, int, int*, void**, QSemaphore*) () from /usr/lib/
0000001 0x00007ffff53319af in QMetaObject::activate(QObject*, int, int, void**) () from /usr/lib/
0000002 0x00007ffff53321d0 in QObject::destroyed(QObject*) () from /usr/lib/
0000003 0x00007ffff5338c61 in QObject::~QObject() () from /usr/lib/
0000004 0x00007fffe38a0681 in ?? () from /usr/lib/
0000005 0x00007ffff6fd9f2c in __run_exit_handlers () from /usr/lib/
0000006 0x00007ffff6fda05a in exit () from /usr/lib/
0000007 0x00007ffff6fc4072 in __libc_start_main () from /usr/lib/
0000008 0x0000000000000000 in ?? ()

Lutz Mändle

2018-07-08 00:37

reporter   ~0109286

The same problem occurs on OpenSuse Tumbleweed (x86_64) since KDE-Plasma 5.13.x. I can suppress this by unsetting the following environment variables (all of them): KDE_FULL_SESSION DESKTOP_SESSION XDG_CURRENT_DESKTOP.
On Raspberry Pi (armv7l) and Odroid-C2 (aarch64) with Xfce 4.12 it runs fine (both with QT 5.11.1).

Reinhard Berger

2018-07-08 07:07

reporter   ~0109287

But for me it has to do with KDE since when you run the project on lxQt wich uses same Qt Version as kubuntu, the exception does not appear.

Only difference is that lxqt uses its own native open/save dialog.

In a pure Qt without KDE there is no native KDE dialog , and without that native KDE dialog the exception does not appear.

For compare :

Kubuntu :
QT Version 5.9.5
KDE Version : 5.44.0
Exception appears

LxQT :
QT Version : 5.9.5
KDE Version : none (uses its own open/file dialog)
no exception

KDE Neon :
Qt Version : 5.10.0
KDE Version : 5.45.0
No exception

Oleksandr Natalenko

2019-01-25 23:53

reporter   ~0113623

Zeljan Rikalo

2019-01-27 14:49

developer   ~0113669

IMO, this problem is related to fpc. I've builded my own fpc-3.0.4 and later fpc_fixes_3_2 and this problem does not exist (Fedora 28 64 bit virtual machine). When I copy fpc-3.0.4 build from my fedora 24 then problem raises again.

Zeljan Rikalo

2019-10-07 19:41

developer   ~0118398

Last edited: 2019-10-07 19:42

View 2 revisions

Finally, I've found out that this is KDE bug (kio core exactly).
Try: XDG_SESSION_DESKTOP=Plasma ./yourapp
and see if it crashes in that case.

Zeljan Rikalo

2020-04-15 19:00

developer   ~0122161

1. It's about fpc-3.0.4, problem with alignment is fixed in r38400, so fpc-3.2.0beta contains fix, fpc trunk also.
2. It's about KioCore bug which is fixed few months ago, so recent KDE plasmas are ok.

Please close.

Issue History

Date Modified Username Field Change
2018-04-30 15:31 Reinhard Berger New Issue
2018-04-30 20:36 Bart Broersma LazTarget => -
2018-04-30 20:36 Bart Broersma Category LCL => Widgetset
2018-07-07 21:09 Reinhard Berger Note Added: 0109282
2018-07-07 23:39 Juha Manninen Note Added: 0109285
2018-07-07 23:39 Juha Manninen Assigned To => Juha Manninen
2018-07-07 23:39 Juha Manninen Status new => assigned
2018-07-07 23:39 Juha Manninen Assigned To Juha Manninen => Zeljan Rikalo
2018-07-08 00:37 Lutz Mändle Note Added: 0109286
2018-07-08 07:07 Reinhard Berger Note Added: 0109287
2019-01-25 23:53 Oleksandr Natalenko Note Added: 0113623
2019-01-27 14:49 Zeljan Rikalo Note Added: 0113669
2019-08-28 10:13 Zeljan Rikalo Relationship added related to 0036019
2019-10-07 19:41 Zeljan Rikalo Status assigned => confirmed
2019-10-07 19:41 Zeljan Rikalo Note Added: 0118398
2019-10-07 19:42 Zeljan Rikalo Note Edited: 0118398 View Revisions
2020-04-15 19:00 Zeljan Rikalo Status confirmed => resolved
2020-04-15 19:00 Zeljan Rikalo Resolution open => no change required
2020-04-15 19:00 Zeljan Rikalo Widgetset QT5 => QT5
2020-04-15 19:00 Zeljan Rikalo Note Added: 0122161
2020-05-06 21:33 Juha Manninen Relationship added related to 0037029