Lmms: Piano Roll - Crash on mouse wheel scroll in the note edit area on a new/empty project

[zonkmachine]

In an empty Song Editor, new project before any notes has been entered. If you scroll the mouse wheel in the note edit area (bottom), lmms crashes.

Replicated on lmms-1.1.3 and the latest betas.

Original report in the forum and video (from the forum post):
https://lmms.io/forum/viewtopic.php?f=7&t=27410
https://www.youtube.com/watch?v=P8cQTYuCiJE

Program received signal SIGSEGV, Segmentation fault.
0x00000000005f1ba0 in QVector<Note*>::begin (this=0x1f0) at /usr/include/qt4/QtCore/qvector.h:248
248     inline const_iterator begin() const { return p->array; }
(gdb) bt
#0  0x00000000005f1ba0 in QVector<Note*>::begin (this=0x1f0) at /usr/include/qt4/QtCore/qvector.h:248
#1  0x00000000005eb694 in PianoRoll::wheelEvent (this=0x15b3d50, we=0x7fffffffd410) at /home/zonkmachine/builds/lmms/lmms/src/gui/editors/PianoRoll.cpp:3203
#2  0x00007ffff71220e4 in QWidget::event (this=0x15b3d50, event=0x7fffffffd410) at kernel/qwidget.cpp:8395
#3  0x00007ffff70d2e2c in QApplicationPrivate::notify_helper (this=this@entry=0x9ad590, receiver=receiver@entry=0x15b3d50, e=e@entry=0x7fffffffd410)
    at kernel/qapplication.cpp:4567
#4  0x00007ffff70da4f4 in QApplication::notify (this=<optimized out>, receiver=0x15b3d50, e=0x7fffffffd410) at kernel/qapplication.cpp:4165
#5  0x00007ffff695c4dd in QCoreApplication::notifyInternal (this=0x99ead0, receiver=receiver@entry=0x15b3d50, event=event@entry=0x7fffffffd410)
    at kernel/qcoreapplication.cpp:953
#6  0x00007ffff7147adf in sendSpontaneousEvent (event=0x7fffffffd410, receiver=0x15b3d50)
    at ../../include/QtCore/../../src/corelib/kernel/qcoreapplication.h:234
#7  QETWidget::translateWheelEvent (this=this@entry=0xf04550, global_x=<optimized out>, global_y=<optimized out>, delta=-120, buttons=..., modifiers=..., 
    orient=Qt::Vertical) at kernel/qapplication_x11.cpp:4672
#8  0x00007ffff714decc in QETWidget::translateMouseEvent (this=this@entry=0xf04550, event=event@entry=0x7fffffffd8a0) at kernel/qapplication_x11.cpp:4449

[zonkmachine]

It crashes here: https://github.com/LMMS/lmms/blob/08573fc96db564283f8580ae79de48085665f9dc/src/gui/editors/PianoRoll.cpp#L3203

[zonkmachine]

Putting if( !hasValidPattern() ){return;} before the for loop fixes this. I'm a bit unsure to as precisely where though.

[PhysSong]

I can find some more places where the check is missing. I'll try to find more crashes tomorrow.

[zonkmachine]

Oki! I suggest you assign this to yourself then.

[PhysSong]

Functions which need the check:

shiftSemiTone
shiftPos
keyPressEvent // Alt + L/R arrow
wheelEvent

Functions which lack of the check, but don't need the check:

isSelection
selectionCount

testPlayNote
pauseTestNotes
testPlayKey

mouseReleaseEvent // ActionMoveNote
dragNotes // ActionMoveNote, ActionResizeNote

desiredPlayModeForAccompany

noteUnderMouse

[zonkmachine]

Another one. <Shift> + <Arrow key>

Program terminated with signal SIGSEGV, Segmentation fault.
#0  0x00000000005f1bfa in QVector<Note*>::begin (this=0x1f0) at /usr/include/qt4/QtCore/qvector.h:248
248     inline const_iterator begin() const { return p->array; }
(gdb) bt
#0  0x00000000005f1bfa in QVector<Note*>::begin (this=0x1f0) at /usr/include/qt4/QtCore/qvector.h:248
#1  0x00000000005e2c05 in PianoRoll::isSelection (this=0x2615f10) at /home/zonkmachine/builds/lmms/lmms/src/gui/editors/PianoRoll.cpp:1013
#2  0x00000000005e2a4d in PianoRoll::shiftPos (this=0x2615f10, amount=12) at /home/zonkmachine/builds/lmms/lmms/src/gui/editors/PianoRoll.cpp:976
#3  0x00000000005e3328 in PianoRoll::keyPressEvent (this=0x2615f10, ke=0x7ffd6aaaef00)
    at /home/zonkmachine/builds/lmms/lmms/src/gui/editors/PianoRoll.cpp:1117
#4  0x00007f4f7872d3e4 in QWidget::event (this=0x2615f10, event=0x7ffd6aaaef00) at kernel/qwidget.cpp:8422

[PhysSong]

That's also included, too.

[zonkmachine]

It doesn't seem to be. The above crash is on 7f1ffd0982d3372d3a695fa7a7dc2a77e5bd859f . I should probably have posted this in the PR.

[PhysSong]

Okay. It seems like I missed one call. I'll fix it.

[PhysSong]

Fixed that. Please re-test the pull request!