Thread 1 "kwrite" received signal SIGSEGV, Segmentation fault.
0x00007ffff776469a in Kate::TextBlock::startLine (this=0x22500000000) at /tmp/ktexteditor/src/buffer/katetextblock.cpp:34
34          return m_buffer->m_startLines[m_blockIndex];
(gdb) bt
#0  0x00007ffff776469a in Kate::TextBlock::startLine (this=0x22500000000) at /tmp/ktexteditor/src/buffer/katetextblock.cpp:34
#1  0x00007ffff775520f in Kate::TextCursor::lineInternal (this=0x555555c2ccc0) at /tmp/ktexteditor/src/buffer/katetextcursor.h:127
#2  0x00007ffff77516d7 in Kate::TextBuffer::rangesForLine (this=0x555555f60360, line=0, view=0x555555b51cf0, rangesWithAttributeOnly=false, outRanges=Python Exception <class 'gdb.error'>: cannot resolve overloaded method `end': no arguments supplied
)
    at /tmp/ktexteditor/src/buffer/katetextbuffer.cpp:1007
#3  0x00007ffff790a23f in Kate::TextBuffer::rangesForLine (this=0x555555f60360, line=0, view=0x555555b51cf0, rangesWithAttributeOnly=false)
    at /tmp/ktexteditor/src/buffer/katetextbuffer.h:495
#4  0x00007ffff79b0496 in KTextEditor::ViewPrivate::updateRangesIn (this=0x555555b51cf0, activationType=KTextEditor::Attribute::ActivateMouseIn)
    at /tmp/ktexteditor/src/view/kateview.cpp:4797
#5  0x00007ffff79b0214 in KTextEditor::ViewPrivate::slotDelayedUpdateOfView (this=0x555555b51cf0) at /tmp/ktexteditor/src/view/kateview.cpp:4761
#6  0x00007ffff79ccb88 in QtPrivate::FunctorCall<QtPrivate::IndexesList<>, QtPrivate::List<>, void, void (KTextEditor::ViewPrivate::*)()>::call(void (KTextEditor::ViewPrivate::*)(), KTextEditor::ViewPrivate*, void**)
    (f=(void (KTextEditor::ViewPrivate::*)(KTextEditor::ViewPrivate * const)) 0x7ffff79b01f2 <KTextEditor::ViewPrivate::slotDelayedUpdateOfView()>, o=0x555555b51cf0, arg=0x555556009348) at /usr/include/qt6/QtCore/qobjectdefs_impl.h:145
#7  0x00007ffff79ca062 in QtPrivate::FunctionPointer<void (KTextEditor::ViewPrivate::*)()>::call<QtPrivate::List<>, void>(void (KTextEditor::ViewPrivate::*)(), KTextEditor::ViewPrivate*, void**)
    (f=(void (KTextEditor::ViewPrivate::*)(KTextEditor::ViewPrivate * const)) 0x7ffff79b01f2 <KTextEditor::ViewPrivate::slotDelayedUpdateOfView()>, o=0x555555b51cf0, arg=0x555556009348) at /usr/include/qt6/QtCore/qobjectdefs_impl.h:182
#8  0x00007ffff79c6fe5 in QtPrivate::QCallableObject<void (KTextEditor::ViewPrivate::*)(), QtPrivate::List<>, void>::impl(int, QtPrivate::QSlotObjectBase*, QObject*, void**, bool*) (which=1, this_=0x555555b102d0, r=0x555555b51cf0, a=0x555556009348, ret=0x0) at /usr/include/qt6/QtCore/qobjectdefs_impl.h:553
#9  0x00007ffff500a21b in QObject::event(QEvent*) () at /usr/lib64/libQt6Core.so.6
#10 0x00007ffff79b00a3 in KTextEditor::ViewPrivate::event (this=0x555555b51cf0, e=0x555556009300) at /tmp/ktexteditor/src/view/kateview.cpp:4712
#11 0x00007ffff6221439 in QApplicationPrivate::notify_helper(QObject*, QEvent*) () at /usr/lib64/libQt6Widgets.so.6
#12 0x00007ffff5083bd8 in QCoreApplication::notifyInternal2(QObject*, QEvent*) () at /usr/lib64/libQt6Core.so.6
#13 0x00007ffff50a970e in QCoreApplicationPrivate::sendPostedEvents(QObject*, int, QThreadData*) () at /usr/lib64/libQt6Core.so.6
#14 0x00007ffff4e47a37 in postEventSourceDispatch(_GSource*, int (*)(void*), void*) () at /usr/lib64/libQt6Core.so.6
#15 0x00007ffff1dfab1b in g_main_dispatch () at /usr/lib64/libglib-2.0.so.0
#16 0x00007ffff1dfdea7 in g_main_context_iterate_unlocked.isra () at /usr/lib64/libglib-2.0.so.0
#17 0x00007ffff1dfe500 in g_main_context_iteration () at /usr/lib64/libglib-2.0.so.0
#18 0x00007ffff4e45be3 in QEventDispatcherGlib::processEvents(QFlags<QEventLoop::ProcessEventsFlag>) () at /usr/lib64/libQt6Core.so.6
#19 0x00007ffff50ae3fa in QEventLoop::exec(QFlags<QEventLoop::ProcessEventsFlag>) () at /usr/lib64/libQt6Core.so.6
#20 0x00007ffff50ae595 in QCoreApplication::exec() () at /usr/lib64/libQt6Core.so.6
#21 0x000055555555796d in main (argc=2, argv=0x7fffffffd1d8) at /var/tmp/portage/kde-apps/kwrite-24.08.2/work/kate-24.08.2/apps/kwrite/main.cpp:162

Bisected to a65e18369bc6043577131dd43d4b3092400d5d5e:

commit a65e18369bc6043577131dd43d4b3092400d5d5e (HEAD)
Author: Waqar Ahmed <waqar.17a@gmail.com>
Date:   Mon Sep 16 18:11:58 2024 +0500

    Store multiline ranges spanning multiple blocks in TextBuffer

 autotests/src/movingrange_test.cpp | 63 +++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
 autotests/src/movingrange_test.h   |  1 +
 src/buffer/katetextblock.cpp       | 20 ++++++++++++++++++++
 src/buffer/katetextbuffer.cpp      | 47 +++++++++++++++++++++++++++++++++++++++++++++++
 src/buffer/katetextbuffer.h        | 24 ++++++++++++++++--------
 src/buffer/katetextrange.cpp       | 26 +++++++++++++++++++++++++-
 src/buffer/katetextrange.h         |  5 +++++
 7 files changed, 177 insertions(+), 9 deletions(-)

Git commit 2c7e0711efd65e68687d530240bb46a1cf8de122 by Waqar Ahmed.
Committed on 16/10/2024 at 05:32.
Pushed by waqar into branch 'master'.

Fix multiblock range handling when unwrapping line

M  +23   -0    autotests/src/movingrange_test.cpp
M  +1    -0    autotests/src/movingrange_test.h
M  +12   -5    src/buffer/katetextblock.cpp

https://invent.kde.org/frameworks/ktexteditor/-/commit/2c7e0711efd65e68687d530240bb46a1cf8de122

*** Bug 496163 has been marked as a duplicate of this bug. ***

*** Bug 496409 has been marked as a duplicate of this bug. ***

I am afraid that this segfault crash has not been totally fixed. I can still reproduce the crash in KDE Framework 6.8.0. Furthermore, the crash behavior is quite complicated. It is not reproducible every time. I have managed to find a method to reproduce the crash with 90% probability:

1. Open the attached file "crash.txt" (consisting of 100 lines of "1234567890") with Kwrite (or Kate).
2. Do a regex "Replace All" of "\n" (linefeed) to "" (empty string).

Then Kwrite will crash 90% of the time. If it does not crash:

3. Press Ctrl+Z to undo the replace, then click on the "Replace All" button again.
4. Repeat Step 3 as fast as possible.

Then Kwrite will crash 60% of the time.

If you replace from "\n" to "\n" (i.e. leave the linefeed unchanged), then Kwrite will not crash on the first replace, but still has a probability to crash on subsequent undo-and-replaces.

Crash on the first replace will yield a fixed backtrace (see Backtrace 1 in the attached file), while crash on subsequent undo-and-replaces will yield different backtraces randomly (see Backtraces 2 to 4).

Operating System: Arch Linux 
KDE Plasma Version: 6.2.3
KDE Frameworks Version: 6.8.0
Qt Version: 6.8.0
Kernel Version: 6.12.1-arch1-1 (64-bit)
Graphics Platform: Wayland

Created attachment 176231 [details]
The file used to trigger the crash

Created attachment 176232 [details]
A few backtraces yielded by crashes on different situations

Indeed there was one more case related to this. Just merged a fix for this, can you try latest master?

(In reply to Waqar Ahmed from comment #9)
> Indeed there was one more case related to this. Just merged a fix for this,
> can you try latest master?

I tried the AppImage version of Daily Build 8537 (last modified 2024-12-01 07:31 UTC+8) of Kate at https://cdn.kde.org/ci-builds/utilities/kate/master/linux/ and the crash is still reproducible.

(In reply to Huanyu Liu from comment #10)
> (In reply to Waqar Ahmed from comment #9)
> > Indeed there was one more case related to this. Just merged a fix for this,
> > can you try latest master?
> 
> I tried the AppImage version of Daily Build 8537 (last modified 2024-12-01
> 07:31 UTC+8) of Kate at
> https://cdn.kde.org/ci-builds/utilities/kate/master/linux/ and the crash is
> still reproducible.

I don't think that image includes the fix as that will still just use the last stable frameworks release.

Which framework version is shown in the about dialog?

(In reply to Christoph Cullmann from comment #12)
> Which framework version is shown in the about dialog?

It is built with KDE Framework 6.8.0. Not the latest version indeed.

I am trying to compile from source. It seems that Kate/Kwrite requires tons of dependencies, so the compilation process might be lengthy...

I think the commit below is in 6.8, let's just re-open atm.

I built Kate from source just now. The crash is no longer reproducible in the latest master. Specifically, it was fixed by the following commit:
https://invent.kde.org/frameworks/ktexteditor/-/commit/0cd45a976b6d04f223c4bbcbdf72185f547645e9

Just 14 hours before my report :( Close as fixed.

Thanks for testing :)

It was a tricky one.

*** Bug 497388 has been marked as a duplicate of this bug. ***

*** Bug 497618 has been marked as a duplicate of this bug. ***