QTreeWidget causes the app to crash after deleting the last QTreeWidgetItem

Andrea_Venturelli

@jsulm
you need to help me about this request because yesterday I tryed to lunch the app in debug mode for the first time ever in my life, and i didn't get it :/

What are the steps that i need to do, in order to collect the information you need ?
thanks in advance.

Andrea_Venturelli

I have an Hint; seems that, after removing successfully once of the three item, the QTreeWidget automatically select the previous index (if it is the first item, select the index after). When the last only remaining item is deleted i think the QTreeWidget is trying to set the previous index, but no indexex are available causing the program to crush

jsulm

@Andrea_Venturelli said in QTreeWidget causes the app to crash after deleting the last QTreeWidgetItem:

What are the steps that i need to do, in order to collect the information you need ?

Click at the button in the bottom right corner with a bug on it in Qtcreator.
When the app crashes you will have the stack trace at the bottom.

Andrea_Venturelli

@jsulm okay, when i compile and run the application normaly, the application starts and I can test it without problems.
Instead, trying to run it in the Debug Mode (the button in the bottom-corner) nothing appen and no window appear..

Here some screenshots:

1show version
2show debug-file-directory
3set max-completions 1000
4complete set arch 
5set breakpoint pending on
6set print elements 10000
7set index-cache on
8set unwindonsignal on
9set width 0
10set height 0
Setting up inferior...
11set substitute-path /Users/qt/work/qt C:/Qt/6.7.1/Src
12set substitute-path C:/work/build/qt5_workdir/w/s C:/Qt/6.7.1/Src
13set substitute-path Q:/qt5_workdir/w/s C:/Qt/6.7.1/Src
14set substitute-path c:/Users/qt/work/install C:/Qt/6.7.1/Src
15set substitute-path c:/users/qt/work/qt C:/Qt/6.7.1/Src
# directory does not exist: /usr/src/debug/qt5base/src/corelib
# directory does not exist: /usr/src/debug/qt5base/src/gui
# directory does not exist: /usr/src/debug/qt5base/src/network
16python sys.path.insert(1, 'C:/Qt/Tools/QtCreator/share/qtcreator/debugger')
17python from gdbbridge import *
18python theDumper.loadDumpers({"token":18})
Debugging has failed.
19show version
20show debug-file-directory
21set max-completions 1000
22complete set arch 
23set breakpoint pending on
24set print elements 10000
25set index-cache on
26set unwindonsignal on
27set width 0
28set height 0
Setting up inferior...
29set substitute-path /Users/qt/work/qt C:/Qt/6.7.1/Src
30set substitute-path C:/work/build/qt5_workdir/w/s C:/Qt/6.7.1/Src
31set substitute-path Q:/qt5_workdir/w/s C:/Qt/6.7.1/Src
32set substitute-path c:/Users/qt/work/install C:/Qt/6.7.1/Src
33set substitute-path c:/users/qt/work/qt C:/Qt/6.7.1/Src
# directory does not exist: /usr/src/debug/qt5base/src/corelib
# directory does not exist: /usr/src/debug/qt5base/src/gui
# directory does not exist: /usr/src/debug/qt5base/src/network
34python sys.path.insert(1, 'C:/Qt/Tools/QtCreator/share/qtcreator/debugger')
35python from gdbbridge import *
36python theDumper.loadDumpers({"token":36})
Debugging has failed.
37show version
38show debug-file-directory
39set max-completions 1000
40complete set arch 
41set breakpoint pending on
42set print elements 10000
43set index-cache on
44set unwindonsignal on
45set width 0
46set height 0
Setting up inferior...
47set substitute-path /Users/qt/work/qt C:/Qt/6.7.1/Src
48set substitute-path C:/work/build/qt5_workdir/w/s C:/Qt/6.7.1/Src
49set substitute-path Q:/qt5_workdir/w/s C:/Qt/6.7.1/Src
50set substitute-path c:/Users/qt/work/install C:/Qt/6.7.1/Src
51set substitute-path c:/users/qt/work/qt C:/Qt/6.7.1/Src
# directory does not exist: /usr/src/debug/qt5base/src/corelib
# directory does not exist: /usr/src/debug/qt5base/src/gui
# directory does not exist: /usr/src/debug/qt5base/src/network
52python sys.path.insert(1, 'C:/Qt/Tools/QtCreator/share/qtcreator/debugger')
53python from gdbbridge import *
54python theDumper.loadDumpers({"token":54})
Debugging has failed.
55show version
56show debug-file-directory
57set max-completions 1000
58complete set arch 
59set breakpoint pending on
60set print elements 10000
61set index-cache on
62set unwindonsignal on
63set width 0
64set height 0
Setting up inferior...
65set substitute-path /Users/qt/work/qt C:/Qt/6.7.1/Src
66set substitute-path C:/work/build/qt5_workdir/w/s C:/Qt/6.7.1/Src
67set substitute-path Q:/qt5_workdir/w/s C:/Qt/6.7.1/Src
68set substitute-path c:/Users/qt/work/install C:/Qt/6.7.1/Src
69set substitute-path c:/users/qt/work/qt C:/Qt/6.7.1/Src
# directory does not exist: /usr/src/debug/qt5base/src/corelib
# directory does not exist: /usr/src/debug/qt5base/src/gui
# directory does not exist: /usr/src/debug/qt5base/src/network
70python sys.path.insert(1, 'C:/Qt/Tools/QtCreator/share/qtcreator/debugger')
71python from gdbbridge import *
72python theDumper.loadDumpers({"token":72})
Debugging has failed.
73show version
74show debug-file-directory
75set max-completions 1000
76complete set arch 
77set breakpoint pending on
78set print elements 10000
79set index-cache on
80set unwindonsignal on
81set width 0
82set height 0
Setting up inferior...
83set substitute-path /Users/qt/work/qt C:/Qt/6.7.1/Src
84set substitute-path C:/work/build/qt5_workdir/w/s C:/Qt/6.7.1/Src
85set substitute-path Q:/qt5_workdir/w/s C:/Qt/6.7.1/Src
86set substitute-path c:/Users/qt/work/install C:/Qt/6.7.1/Src
87set substitute-path c:/users/qt/work/qt C:/Qt/6.7.1/Src
# directory does not exist: /usr/src/debug/qt5base/src/corelib
# directory does not exist: /usr/src/debug/qt5base/src/gui
# directory does not exist: /usr/src/debug/qt5base/src/network
88python sys.path.insert(1, 'C:/Qt/Tools/QtCreator/share/qtcreator/debugger')
89python from gdbbridge import *
90python theDumper.loadDumpers({"token":90})
Debugging has failed.
91show version
92show debug-file-directory
93set max-completions 1000
94complete set arch 
95set breakpoint pending on
96set print elements 10000
97set index-cache on
98set unwindonsignal on
99set width 0
100set height 0
Setting up inferior...
101set substitute-path /Users/qt/work/qt C:/Qt/6.7.1/Src
102set substitute-path C:/work/build/qt5_workdir/w/s C:/Qt/6.7.1/Src
103set substitute-path Q:/qt5_workdir/w/s C:/Qt/6.7.1/Src
104set substitute-path c:/Users/qt/work/install C:/Qt/6.7.1/Src
105set substitute-path c:/users/qt/work/qt C:/Qt/6.7.1/Src
# directory does not exist: /usr/src/debug/qt5base/src/corelib
# directory does not exist: /usr/src/debug/qt5base/src/gui
# directory does not exist: /usr/src/debug/qt5base/src/network
106python sys.path.insert(1, 'C:/Qt/Tools/QtCreator/share/qtcreator/debugger')
107python from gdbbridge import *
108python theDumper.loadDumpers({"token":108})
Debugging has failed.

d[GDB] UNEXPECTED GDB STDERR: error: unknown option: --tty=\\.\pipe\creator-11944-28798
derror: unknown option: -i
dUse 'lldb.exe --help' for a complete list of options.
d[GDB] GDB PROCESS FINISHED, status 0, exit code 1 (0x1)
d[GDB] NOTE: ENGINE SETUP FAILED
d[GDB] State changed from EngineSetupRequested(1) to EngineSetupFailed(2)
<Debugging has failed.
d[GDB] State changed from EngineSetupFailed(2) to DebuggerFinished(16)

jsulm

@Andrea_Venturelli It's not clear to me what debugger you set in the Kit you're using? Seems to be lldb. With MinGW one is usually using GDB. The GDB debugger is provided as part of the MinGW setup from Qt Online Installer.

Andrea_Venturelli

@jsulm let's see if this helps you a little bit more.

unfortunally i do not understand where I need to search for the informations needed to help you understand why my debugger fails to compile and run.

I'm open to suggestions or direction where to retrive this kind of helpfull information in order to simplify your life and not wasting so much of yours time.

jsulm

@Andrea_Venturelli Please check in the Kit you're using what debugger is set there. It should be GDB from MinGW.

Andrea_Venturelli

yes @jsulm, is GDB as illustrated in the code snippet some messages ago

this is taken from the "Global Debugger Log" panel , after running the Debug play button
and is clearly referring to GDB

GDB PROCESS FINISHED, status 0, exit code 1 (0x1)
d[GDB] NOTE: ENGINE SETUP FAILED

d[GDB] UNEXPECTED GDB STDERR: error: unknown option: --tty=\\.\pipe\creator-11944-28798
derror: unknown option: -i
dUse 'lldb.exe --help' for a complete list of options.
d[GDB] GDB PROCESS FINISHED, status 0, exit code 1 (0x1)
d[GDB] NOTE: ENGINE SETUP FAILED
d[GDB] State changed from EngineSetupRequested(1) to EngineSetupFailed(2)
<Debugging has failed.
d[GDB] State changed from EngineSetupFailed(2) to DebuggerFinished(16)

jsulm

@Andrea_Venturelli said in QTreeWidget causes the app to crash after deleting the last QTreeWidgetItem:

dUse 'lldb.exe --help' for a complete list of options.

Why don't you simply check in the Kit which debugger is set?

Andrea_Venturelli

how can i do that? it's not clear to me, where the informations of the debug type resides; a screenshot could be helpfull or even the path like so:

[Qt creator] >> Edit >> Preferences... >> Debugger .. and so on or
[Qt Maintenance Tool] >> Extencion >> ecc..

because I have a little experience with Qt Creator, resulting in me, not knowing where to look for

jsulm

@Andrea_Venturelli [Qt creator] >> Edit >> Preferences... >> Kits - then select the Kit you're using

Andrea_Venturelli

this is what I use to create the projects (and using qMake to built):

jsulm

@Andrea_Venturelli Please show ALL settings of that Kit (especially Qt version and debugger set).

Andrea_Venturelli

Desktop Qt 6.7.1 llvm-mingw 64-bit

c++ compiler:

LLVM-MinGW 17.0.6 64-bit for c++

Debugger:

LLVM lldb 17.0.6 64-bit

Qt version:

Qt 6.7.1 llvm-mingw 64-bit

CMake Tool:

CMake 3.27.7 (Qt)

jsulm

@Andrea_Venturelli Try with Qt for MinGW (not llvm-mingw).
Maybe QtCreator does not support lldb properly.

cristian-adam

It looks like the LLVM MInGW debugger has the wrong debugger type set. It should be LLDB and not GDB.

https://bugreports.qt.io/browse/QTBUG-123330 was supposed to be a thing of the past...

Andrea_Venturelli

How should I change the current project KIT, transitioning from llvm-mingw to MinGW ??

I tryed it, from the preferences panel under: Edit >> Preferences... >> Kits
but I'm pretty sure that has no impact on the current project, instead will change the default Kit, the next time I'll create a new project.

Exists such a way to change the Kit to the current running project or I'm forced to create a brand-new one and manually paste the code?

jsulm

@Andrea_Venturelli said in QTreeWidget causes the app to crash after deleting the last QTreeWidgetItem:

How should I change the current project KIT, transitioning from llvm-mingw to MinGW ??

On the right side in QtCreator "Projects".
From your screen-shots it looks like you already have a Kit for Qt MinGW.

Andrea_Venturelli

okay, finally we did it!
for the other reader who might encounter this problem with the debugger, the solution is:

on the left panel (where it is "Welcome", "Edit", "Design") there is "Projects"
open projects and under "Built & Run" you have all the kit available
I switched from Desktop Qt 6.7.1 llvm-mingw 64-bit to Desktop Qt 6.7.1 MinGW 64-bit
I pressed the "run" button and compile fine.
after I Run the normal "Debug play button" at the bottom left cornern and now is working

now we can go back to the main issues where this discussion started

Andrea_Venturelli

this is the error I get after deleting the last item in the QTreeWidget:

here the call stack:

I also found out where was the problem, other then I'm a big chicken ;)

SOLUTION

I had the QTreeWidget::ItemChanged signal, connected to one of my custom slots where i automatically update the values inside the LineEdits. But I ignored that, even when the last item is deleted, the QTreeWidget calls the "ItemChanged" signal.

adding a check if the, before trying to retrive information from an empty QTreeWidgetItem solved the problem

void Dialog::on_treeWidgetItemChanged()
{
    // check control
    if (m_paths.count())
    {
        auto current_itm = ui->left_wdg->currentItem();

        // update the lineEdit' values
        ui->fn_le->setText(current_itm->text(0));           // THIS WAS THE CAUSE OF THE ERROR
        ui->fPath_le->setText(current_itm->text(1));
    }
}