[kdevelop] [Bug 376595] Kdevelop crashes on watch member variable

[Aetf]

https://bugs.kde.org/show_bug.cgi?id=376595

Aetf <7437...@gmail.com> changed:

   What|Removed |Added

 Status|VERIFIED|CLOSED

--- Comment #27 from Aetf <7437...@gmail.com> ---
Thank you for reporting!

I've also added a link pointing back to this bug in their bug tracker.

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[kdevelop] [Bug 376595] Kdevelop crashes on watch member variable

[Ian Haber]

https://bugs.kde.org/show_bug.cgi?id=376595

--- Comment #26 from Ian Haber  ---
Alright. I posted in the gdb bugtracking
https://sourceware.org/bugzilla/show_bug.cgi?id=21192 

hopefully they will fix it eventually.

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[kdevelop] [Bug 376595] Kdevelop crashes on watch member variable

[Aetf]

https://bugs.kde.org/show_bug.cgi?id=376595

Aetf <7437...@gmail.com> changed:

   What|Removed |Added

 Resolution|WAITINGFORINFO  |UPSTREAM

--- Comment #25 from Aetf <7437...@gmail.com> ---
Well adding an UI to set prefix and extra code to identify and match member
variable just sounds too much for a workaround for some bug in gdb that will
eventually be fixed.

For the "info locals", there are also global and static variables that are not
member variable. There are too many corner cases, not to even mention single
variable is only the simplest case for watchpoint[1].

[1] https://sourceware.org/gdb/onlinedocs/gdb/Set-Watchpoints.html

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[kdevelop] [Bug 376595] Kdevelop crashes on watch member variable

[Ian Haber]

https://bugs.kde.org/show_bug.cgi?id=376595

--- Comment #24 from Ian Haber  ---
would it be possible to maybe have some sort of manually set variable that
would be a prefix for member variables? a lot of us use a very specific member
variable prefix, so if it starts with that prefix, chances are it is a member? 

it is also possible to determine if the variable was declared in the current
scope by using 'info locals', right? so any variable not in 'info locals' would
be a member?

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[kdevelop] [Bug 376595] Kdevelop crashes on watch member variable

[Aetf]

https://bugs.kde.org/show_bug.cgi?id=376595

Aetf <7437...@gmail.com> changed:

   What|Removed |Added

 Attachment #104135|0   |1
is obsolete||

--- Comment #23 from Aetf <7437...@gmail.com> ---
Created attachment 104160
  --> https://bugs.kde.org/attachment.cgi?id=104160=edit
Better handle and report debugger errors

Anyway, I've updated my patch to better report and end the debug session in
this case.

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[kdevelop] [Bug 376595] Kdevelop crashes on watch member variable

[Aetf]

https://bugs.kde.org/show_bug.cgi?id=376595

--- Comment #22 from Aetf <7437...@gmail.com> ---
Okay I can reproduce your issue now. I guess the difference is that yours is
multi-threaded (several threads for qt internal stuff). And when gdb stopped,
it stopped at another thread different from the main thread. Probably gdb can't
handle this case well.

However I'm afraid there's no much I can do on the kdevelop side. As it's hard
to distinguish a member variable from normal ones, and it's unclear whether
this is the only condition that would trigger the bug. Maybe you should report
this to gdb.

In the mean time, as a workaround, you can set watchpoints in the Breakpoints
tool view manually, using "this." as the location. This works as
intended.

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[kdevelop] [Bug 376595] Kdevelop crashes on watch member variable

[Ian Haber]

https://bugs.kde.org/show_bug.cgi?id=376595

--- Comment #21 from Ian Haber  ---
Created attachment 104158
  --> https://bugs.kde.org/attachment.cgi?id=104158=edit
Log file for the test case

Here is the log file for the test case i created.

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[kdevelop] [Bug 376595] Kdevelop crashes on watch member variable

[Ian Haber]

https://bugs.kde.org/show_bug.cgi?id=376595

--- Comment #20 from Ian Haber  ---
I have created a simple test program that causes the crash. 
//main.cpp
int main(int argc, char* argv[])
{
QApplication applicationInstance(argc, argv);
testGDBCrash crasher;
if (crasher.exec() != QDialog::Accepted)
return 0;
return applicationInstance.exec();
}
//testGDBCrash.h
#ifndef TESTGDBCRASH_H
#define TESTGDBCRASH_H
#include 
#include 
class testGDBCrash : public QDialog
{
Q_OBJECT
public: 
testGDBCrash(QWidget * parent=0);
Q_SLOT void TestCrash();
bool m_bInUpdate; 
};
#endif // TESTGDBCRASH_H
//testGDBCrash.cpp
#include "testGDBCrash.h"
#include 
#include 
testGDBCrash::testGDBCrash(QWidget* parent):QDialog(parent)
{
resize(200,100);
QHBoxLayout * layout=new QHBoxLayout(this);
QPushButton * pb=new QPushButton("crash",this);
layout->addWidget(pb);
setLayout(layout);
show();
m_bInUpdate=false;

connect(pb,SIGNAL(clicked()),this,SLOT(TestCrash()));
}
void testGDBCrash::TestCrash()
{
if(m_bInUpdate)
return;
m_bInUpdate=false;
m_bInUpdate=true;
m_bInUpdate=false;
}

Steps to crash:
1. Run
2. put a breakpoint on line 18 of testGDBCrash.cpp (the if statement)
3. break on change for m_bInUpdate
4. Continue
5. Watch crash.

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[kdevelop] [Bug 376595] Kdevelop crashes on watch member variable

[Ian Haber]

https://bugs.kde.org/show_bug.cgi?id=376595

--- Comment #19 from Ian Haber  ---
ran the test case, it does not give me the same behavior. i'm currently
modifying it to see if i can reproduce the issue. As far as i can tell, the
only differences between my current version of the test and my normal source is
that the method i'm attempting to use this on is a slot... but in qt, pretty
much everything is a slot or called by a slot.

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[kdevelop] [Bug 376595] Kdevelop crashes on watch member variable

[Aetf]

https://bugs.kde.org/show_bug.cgi?id=376595

--- Comment #18 from Aetf <7437...@gmail.com> ---
Created attachment 104154
  --> https://bugs.kde.org/attachment.cgi?id=104154=edit
GDB outputs when watchpoint goes out of scope

Yes, kdevelop uses plain variable name when adding watch points for member
variables. This however should work because gdb will delete all invalid
watchpoints when the execution left valid scope.

I've created a minimal test program to trigger this problem:

struct testStruct {
int a; int b;
void bar() {
a = a + 1;
}
};

int main() {
testStruct ts;
ts.a = ts.b = 0;
ts.bar();
ts.b++;
return 0;
}

After compile and load it in gdb, this is what I got:

1. break at line 4
2. watch a
3. continue and gdb stopped after a = a + 1 because of watchpoint hit
4. continue again and gdb stopped at some random point after leaving
testStruct::bar() with the following output

Error evaluating expression for watchpoint 2
current stack frame does not contain a variable named `this'
Watchpoint 2 deleted.

5. continue and the program exits normally.

If I use watch this.a instead, the outcome is almost the same with the only
difference being the warning from gdb:

Watchpoint 3 deleted because the program has left the block in
which its expression is valid.

I've attached the full output from gdb. The point here is that gdb should be
able to delete invalid watchpoint gracefully regardless it was set as
"this." or "". And it shouldn't produce malformed output in
its machine interface which kdevelop uses.

That being said, I'm using a newer version of gdb than yours, so probably the
behavior changed. Ian, are you getting the same behavior using my test program?

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[kdevelop] [Bug 376595] Kdevelop crashes on watch member variable

[Ian Haber]

https://bugs.kde.org/show_bug.cgi?id=376595

--- Comment #17 from Ian Haber  ---
The patch does prevent the crash, although as you suggested, gdb is just
sitting there hanging now. Messing with the gdb console outside of kdevelop led
me to something interesting. if i use the command 'watch m_bInUpdate', when i
attempt to continue, it will just say "current stack frame does not contain a
variable named 'this'" and not do anything. If i use the command 'watch
this.m_bInUpdate', it works as i would expect. 

Could it be that when kdevelop adds a watch for member variables it just uses
'watch '? That being said, if this were the case, i would expect that
it would be causing issues for everyone.

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[kdevelop] [Bug 376595] Kdevelop crashes on watch member variable

[Aetf]

https://bugs.kde.org/show_bug.cgi?id=376595

--- Comment #16 from Aetf <7437...@gmail.com> ---
Created attachment 104135
  --> https://bugs.kde.org/attachment.cgi?id=104135=edit
Proposed patch

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[kdevelop] [Bug 376595] Kdevelop crashes on watch member variable

[Aetf]

https://bugs.kde.org/show_bug.cgi?id=376595

--- Comment #15 from Aetf <7437...@gmail.com> ---
Okay. So setting watch point itself seems normal in log. The crash actually
happens before the watch point was triggered.

gdb returned two replies for 35-exec-continue command:

35^running and 35^error,msg=\"Command aborted.\"

This doesn't confirm to the spec and confused kdevelop which assumes each reply
must have a corresponding command.

I will fix this by ignoring wild replies from gdb. Please try if my patch fixes
the crash.

But this is likely also a bug within gdb itself. I would suggest verify if
debugging directly in gdb command line works with your program if there's still
something wrong. (Probably something like the program doesn't resume execution
because the exec-continue command failed)

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[kdevelop] [Bug 376595] Kdevelop crashes on watch member variable

[Milian Wolff]

https://bugs.kde.org/show_bug.cgi?id=376595

--- Comment #14 from Milian Wolff  ---
Please also try valgrind, that is usually much more helpful in such situations:

valgrind --smc-check=all-non-file --track-origins=yes kdevelop

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[kdevelop] [Bug 376595] Kdevelop crashes on watch member variable

[Ian Haber]

https://bugs.kde.org/show_bug.cgi?id=376595

--- Comment #13 from Ian Haber  ---
Created attachment 104134
  --> https://bugs.kde.org/attachment.cgi?id=104134=edit
Debug output for debugger

Here is the output. my gdb version:
GNU gdb (Ubuntu 7.11.1-0ubuntu1~16.04) 7.11.1

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[kdevelop] [Bug 376595] Kdevelop crashes on watch member variable

[Aetf]

https://bugs.kde.org/show_bug.cgi?id=376595

--- Comment #12 from Aetf <7437...@gmail.com> ---
I see. Seems your Qt version doesn't support semicolon separated logging rules.
Instead, create a file named logging.conf with the following content:

[Rules]
kdevelop.debuggers.gdb.debug=true
kdevelop.debuggers.common.debug=true

And launch kdevelop with

QT_LOGGING_CONF='/path/to/logging.conf' kdevelop

I think the crash might be specific to some particular gdb version. But without
detailed logging, I can't tell anything yet.

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[kdevelop] [Bug 376595] Kdevelop crashes on watch member variable

[Ian Haber]

https://bugs.kde.org/show_bug.cgi?id=376595

--- Comment #11 from Ian Haber  ---
I get the crash regardless of how i set the breakpoint. i can set it in gdb or
through kdevelop and both will crash.

the only logging stuff i got was 
qt.core.logging: Ignoring malformed logging rule:
'kdevelop.debuggers.gdb.debug=true;kdevelop.debuggers.common.debug=true' at the
start of the program

and kdevelop.debuggers.common: "No environment group specified, looks like a
broken configuration, please check run configuration 'xx'. Using default
environment group." during the startup of my program. 


'Breakpoint doesn't contain required location/expression data' is logged when i
create the breakpoint. There is nothing after that before the backtrace.

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[kdevelop] [Bug 376595] Kdevelop crashes on watch member variable

[Aetf]

https://bugs.kde.org/show_bug.cgi?id=376595

--- Comment #10 from Aetf <7437...@gmail.com> ---
Hmm actually I can't reproduce this. I tried with a structure member variable
and it works as intended.

>From the log output, kdevelop was complaining about gdb not returning required
data. So my guessing is something went wrong with either the gdb itself or the
way we were setting breakpoints.

How do you exactly set break on change? By manually using the gdb console or by
hovering on the variable and click "stop on change" button?

Also, I'm expecting some log output with the prefix
"kdevelop.debuggers.common:" and related to the internal interaction between
kdevelop and gdb. Could you paste the full log output?

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[kdevelop] [Bug 376595] Kdevelop crashes on watch member variable

[Ian Haber]

https://bugs.kde.org/show_bug.cgi?id=376595

--- Comment #9 from Ian Haber  ---
with those debug messages, i get the same backtrace as before, but i get 

QMetaObject::invokeMethod: No such method
ExpandingTree::scrollTo(QModelIndex,QAbstractItemView::ScrollHint)
Breakpoint doesn't contain required location/expression data

before it.

i would assume though that you could recreate this. it is 100% for me.

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[kdevelop] [Bug 376595] Kdevelop crashes on watch member variable

[Aetf]

https://bugs.kde.org/show_bug.cgi?id=376595

Aetf <7437...@gmail.com> changed:

   What|Removed |Added

 Status|RESOLVED|VERIFIED

--- Comment #8 from Aetf <7437...@gmail.com> ---
Hi Ion, from the backtrace it's not clear what's going wrong here. There's no
abnormal pointer access in the frame 0 of the backtrace. Could you also provide
the console output when crashing?

The debugger plugin related logs are disabled by default, you can enable it by
starting kdevelop like this inside console:

QT_LOGGING_RULES="kdevelop.debuggers.gdb.debug=true;kdevelop.debuggers.common.debug=true"
kdevelop

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[kdevelop] [Bug 376595] Kdevelop crashes on watch member variable

[Kevin Funk]

https://bugs.kde.org/show_bug.cgi?id=376595

Kevin Funk  changed:

   What|Removed |Added

 CC||7437...@gmail.com

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[kdevelop] [Bug 376595] Kdevelop crashes on watch member variable

[Ian Haber]

https://bugs.kde.org/show_bug.cgi?id=376595

--- Comment #7 from Ian Haber  ---
if you need anything else from gdb, i still have it up and will get back to you
on monday.

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[kdevelop] [Bug 376595] Kdevelop crashes on watch member variable

[Ian Haber]

https://bugs.kde.org/show_bug.cgi?id=376595

--- Comment #6 from Ian Haber  ---
here is the backtrace. it also looks like i got a message saying 'breakpoint
doesn't contain required location/expression data'. maybe that has something to
do with it

Thread 1 "kdevelop" received signal SIGSEGV, Segmentation fault.
0x7fffb263a07e in KDevMI::MI::MICommand::markAsCompleted() ()
   from /home/ian/kde-5/lib/x86_64-linux-gnu/plugins/kdevplatform/27/kdevgdb.so
(gdb) bt
#0  0x7fffb263a07e in KDevMI::MI::MICommand::markAsCompleted() ()
   from /home/ian/kde-5/lib/x86_64-linux-gnu/plugins/kdevplatform/27/kdevgdb.so
#1  0x7fffb263bd9d in KDevMI::MIDebugger::processLine(QByteArray const&) ()
   from /home/ian/kde-5/lib/x86_64-linux-gnu/plugins/kdevplatform/27/kdevgdb.so
#2  0x7fffb263b506 in KDevMI::MIDebugger::readyReadStandardOutput() ()
   from /home/ian/kde-5/lib/x86_64-linux-gnu/plugins/kdevplatform/27/kdevgdb.so
#3  0x7fffb263e308 in QtPrivate::FunctorCall,
QtPrivate::List<>, void, void (KDevMI::MIDebugger::*)()>::call(void
(KDevMI::MIDebugger::*)(), KDevMI::MIDebugger*, void**) ()
   from /home/ian/kde-5/lib/x86_64-linux-gnu/plugins/kdevplatform/27/kdevgdb.so
#4  0x7fffb263e1ca in void QtPrivate::FunctionPointer::call, void>(void
(KDevMI::MIDebugger::*)(), KDevMI::MIDebugger*, void**) ()
   from /home/ian/kde-5/lib/x86_64-linux-gnu/plugins/kdevplatform/27/kdevgdb.so
#5  0x7fffb263ded1 in QtPrivate::QSlotObject, void>::impl(int,
QtPrivate::QSlotObjectBase*, QObject*, void**, bool*) ()
   from /home/ian/kde-5/lib/x86_64-linux-gnu/plugins/kdevplatform/27/kdevgdb.so
#6  0x75d35baf in QtPrivate::QSlotObjectBase::call (a=0x7fffcfa0,
r=0x6c72030, this=)
at ../../include/QtCore/../../src/corelib/kernel/qobject_impl.h:124
#7  QMetaObject::activate (sender=sender@entry=0x6c72120,
signalOffset=, 
local_signal_index=local_signal_index@entry=5, argv=argv@entry=0x0) at
kernel/qobject.cpp:3698
#8  0x75d36537 in QMetaObject::activate (sender=sender@entry=0x6c72120, 
m=m@entry=0x75f4c400 ,
local_signal_index=local_signal_index@entry=5, 
argv=argv@entry=0x0) at kernel/qobject.cpp:3578
#9  0x75c34b63 in QProcess::readyReadStandardOutput
(this=this@entry=0x6c72120) at .moc/moc_qprocess.cpp:266
---Type  to continue, or q  to quit---
#10 0x75c3d0c2 in QProcessPrivate::tryReadFromChannel (this=0x6c72140,
channel=0x6c72270)
at io/qprocess.cpp:966
#11 0x75c3d540 in QProcessPrivate::_q_canReadStandardOutput
(this=) at io/qprocess.cpp:977
#12 QProcess::qt_static_metacall (_o=, _c=,
_id=, _a=0x7fffd1a0)
at .moc/moc_qprocess.cpp:133
#13 0x75d35d2a in QMetaObject::activate (sender=sender@entry=0x6c72ec0,
signalOffset=, 
local_signal_index=local_signal_index@entry=0,
argv=argv@entry=0x7fffd1a0) at kernel/qobject.cpp:3713
#14 0x75d36537 in QMetaObject::activate (sender=sender@entry=0x6c72ec0, 
m=m@entry=0x75f50780 ,
local_signal_index=local_signal_index@entry=0, 
argv=argv@entry=0x7fffd1a0) at kernel/qobject.cpp:3578
#15 0x75db524e in QSocketNotifier::activated
(this=this@entry=0x6c72ec0, _t1=82)
at .moc/moc_qsocketnotifier.cpp:134
#16 0x75d421cb in QSocketNotifier::event (this=0x6c72ec0, e=) at kernel/qsocketnotifier.cpp:260
#17 0x765fa05c in QApplicationPrivate::notify_helper
(this=this@entry=0x647190, 
receiver=receiver@entry=0x6c72ec0, e=e@entry=0x7fffd410) at
kernel/qapplication.cpp:3716
#18 0x765ff516 in QApplication::notify (this=0x7fffd970,
receiver=0x6c72ec0, e=0x7fffd410)
at kernel/qapplication.cpp:3499
#19 0x75d0738b in QCoreApplication::notifyInternal
(this=0x7fffd970, receiver=0x6c72ec0, 
event=event@entry=0x7fffd410) at kernel/qcoreapplication.cpp:965
#20 0x75d5dc95 in QCoreApplication::sendEvent (event=0x7fffd410,
receiver=)
at ../../include/QtCore/../../src/corelib/kernel/qcoreapplication.h:224
#21 socketNotifierSourceDispatch (source=0x7659a0) at
kernel/qeventdispatcher_glib.cpp:101
#22 0x7fffee394197 in g_main_context_dispatch () from
/lib/x86_64-linux-gnu/libglib-2.0.so.0
#23 0x7fffee3943f0 in ?? () from /lib/x86_64-linux-gnu/libglib-2.0.so.0
#24 0x7fffee39449c in g_main_context_iteration () from
/lib/x86_64-linux-gnu/libglib-2.0.so.0
#25 0x75d5d7cf in QEventDispatcherGlib::processEvents (this=0x765850,
flags=...)
at kernel/qeventdispatcher_glib.cpp:418
#26 0x75d04b4a in QEventLoop::exec (this=this@entry=0x7fffd620,
flags=..., flags@entry=...)
at kernel/qeventloop.cpp:204
#27 0x75d0cbec in QCoreApplication::exec () at
kernel/qcoreapplication.cpp:1229
#28 0x0040e79e in main ()

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[kdevelop] [Bug 376595] Kdevelop crashes on watch member variable

[Kevin Funk]

https://bugs.kde.org/show_bug.cgi?id=376595

--- Comment #5 from Kevin Funk  ---
True, this got added just recently. I've restored compat with KF5 5.15 now.

See:
commit 2c775c07436107f90bec8ee16b73f4e5258f362d
Author: Kevin Funk 
Date:   Fri Feb 17 23:32:22 2017 +0100

Restore compat with KF5 5.15

The signal KUrlRequester::textEdited got only added in 5.21

Please try to compile again

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[kdevelop] [Bug 376595] Kdevelop crashes on watch member variable

[Ian Haber]

https://bugs.kde.org/show_bug.cgi?id=376595

--- Comment #4 from Ian Haber  ---
I get this build error when i attempt to build master. what module is
KUrlRequester in that i'm assuming i need to add to the list of things to
download and update.

/home/ian/kdesrc/kdevelop/languages/plugins/custom-definesandincludes/compilerprovider/widget/compilerswidget.cpp:81:34:
error: ‘textEdited’ is not a member of ‘KUrlRequester’
 connect(m_ui->compilerPath, ::textEdited, this,
::compilerEdited);

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[kdevelop] [Bug 376595] Kdevelop crashes on watch member variable

[Kevin Funk]

https://bugs.kde.org/show_bug.cgi?id=376595

--- Comment #3 from Kevin Funk  ---
FWIW, master should build fine according to CI. If you want to switch branches
I *think* you should be able to use this:

module kdevelop
  branch-group kf5-qt5
...

If that doesn't work you can still simply just `git checkout 5.1; make; make
install` in both the kdevplatform + kdevelop dir.

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[kdevelop] [Bug 376595] Kdevelop crashes on watch member variable

[Ian Haber]

https://bugs.kde.org/show_bug.cgi?id=376595

--- Comment #2 from Ian Haber  ---
so i've never been able to get a backtrace while using the appimage. I
attempted to build source today, but it seems there are build errors in master
at the moment. how do i set kdesrc-build to use branch 5.1 for kdevelop and
kdevplatform? 

I attempted to modify the .kdesrc-buildrc and set it to use branch 5.1, but it
attempts to use svn instead of git and then fails to update.

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[kdevelop] [Bug 376595] Kdevelop crashes on watch member variable

[Kevin Funk]

https://bugs.kde.org/show_bug.cgi?id=376595

Kevin Funk  changed:

   What|Removed |Added

 Status|UNCONFIRMED |RESOLVED
 Resolution|--- |WAITINGFORINFO

--- Comment #1 from Kevin Funk  ---
Please retrieve a backtrace of the crash.

See:
https://community.kde.org/Guidelines_and_HOWTOs/Debugging/How_to_create_useful_crash_reports

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