Ensure midi port exists before removing

[zonkmachine]

I got a crash on closing so I reference this to issue #2633.

Unfortunately I can't replicate the crash to test the fix. I've tried turning on/off my midi keyboard before closing but so far I haven't had the fortune of another malfunction.

In this crash in particular it failed on qFind (here) so I suspect it was because of bad data in.
#9 0x0000000000579043 in MidiClient::removePort (this=0x29758f0, port=0x7fa4c40a89a8) at /home/zonkmachine/builds/lmms/lmms/src/core/midi/MidiClient.cpp:71

Does this sound plausible?

 Program terminated with signal SIGABRT, Aborted. #0 0x00007fa4cd366c37 in __GI_raise (sig=sig@entry=6) at ../nptl/sysdeps/unix/sysv/linux/raise.c:56 56	../nptl/sysdeps/unix/sysv/linux/raise.c: No such file or directory. (gdb) bt #0 0x00007fa4cd366c37 in __GI_raise (sig=sig@entry=6) at ../nptl/sysdeps/unix/sysv/linux/raise.c:56 #1 0x00007fa4cd36a028 in __GI_abort () at abort.c:89 #2 0x00007fa4cfae8c92 in qt_message_output (msgType=msgType@entry=QtFatalMsg, buf=0x285dec8 "ASSERT: \"asize <= aalloc\" in file /usr/include/qt4/QtCore/qvector.h, line 474") at global/qglobal.cpp:2383 #3 0x00007fa4cfae8ff9 in qt_message(QtMsgType, const char *, typedef __va_list_tag __va_list_tag *) (msgType=msgType@entry=QtFatalMsg, msg=0x7fa4cfc56a20 "ASSERT: \"%s\" in file %s, line %d", ap=ap@entry=0x7ffcf27f81f8) at global/qglobal.cpp:2429 #4 0x00007fa4cfae9804 in qFatal (msg=<optimized out>) at global/qglobal.cpp:2612 #5 0x0000000000579bbf in QVector<MidiPort*>::realloc (this=0x29758f8, asize=56747520, aalloc=0) at /usr/include/qt4/QtCore/qvector.h:474 #6 0x0000000000579eb2 in QVector<MidiPort*>::detach_helper (this=0x29758f8) at /usr/include/qt4/QtCore/qvector.h:337 #7 0x0000000000579a24 in QVector<MidiPort*>::detach (this=0x29758f8) at /usr/include/qt4/QtCore/qvector.h:147 #8 0x00000000005797c2 in QVector<MidiPort*>::end (this=0x29758f8) at /usr/include/qt4/QtCore/qvector.h:250 #9 0x0000000000579043 in MidiClient::removePort (this=0x29758f0, port=0x7fa4c40a89a8) at /home/zonkmachine/builds/lmms/lmms/src/core/midi/MidiClient.cpp:71 #10 0x000000000057bffa in MidiPort::~MidiPort (this=0x7fa4c40a89a8, __in_chrg=<optimized out>) at /home/zonkmachine/builds/lmms/lmms/src/core/midi/MidiPort.cpp:93 #11 0x000000000057a109 in MidiController::~MidiController (this=0x7fa4c40a8920, __in_chrg=<optimized out>) at /home/zonkmachine/builds/lmms/lmms/src/core/midi/MidiController.cpp:51 #12 0x000000000057a166 in MidiController::~MidiController (this=0x7fa4c40a8920, __in_chrg=<optimized out>) at /home/zonkmachine/builds/lmms/lmms/src/core/midi/MidiController.cpp:53 #13 0x00007fa4cfc0c168 in QObjectPrivate::deleteChildren (this=this@entry=0x26f38e0) at kernel/qobject.cpp:1907 

 (gdb) bt full #0 0x00007fa4cd366c37 in __GI_raise (sig=sig@entry=6) at ../nptl/sysdeps/unix/sysv/linux/raise.c:56 resultvar = 0 pid = 11019 selftid = 11019 #1 0x00007fa4cd36a028 in __GI_abort () at abort.c:89 save_stage = 2 act = {__sigaction_handler = {sa_handler = 0x7ffcf27f8190, sa_sigaction = 0x7ffcf27f8190}, sa_mask = {__val = {140724376928672, 42327752, 140345858389751, 140720308486149, 0, 140345835254464, 140345794063664, 3, 42327752, 140724376928544, 140345858418341, 1, 2147483648, 140345840351168, 10, 140345840351192}}, sa_flags = -786049088, sa_restorer = 0x726f4374512f3474} sigs = {__val = {32, 0 <repeats 15 times>}} #2 0x00007fa4cfae8c92 in qt_message_output (msgType=msgType@entry=QtFatalMsg, buf=0x285dec8 "ASSERT: \"asize <= aalloc\" in file /usr/include/qt4/QtCore/qvector.h, line 474") at global/qglobal.cpp:2383 No locals. #3 0x00007fa4cfae8ff9 in qt_message(QtMsgType, const char *, typedef __va_list_tag __va_list_tag *) (msgType=msgType@entry=QtFatalMsg, msg=0x7fa4cfc56a20 "ASSERT: \"%s\" in file %s, line %d", ap=ap@entry=0x7ffcf27f81f8) at global/qglobal.cpp:2429 buf = {static shared_null = {ref = {_q_value = 79}, alloc = 0, size = 0, data = 0x7fa4cff5b7d8 <QByteArray::shared_null+24> "", array = ""}, static shared_empty = {ref = {_q_value = 2}, alloc = 0, size = 0, data = 0x7fa4cff5b7b8 <QByteArray::shared_empty+24> "", array = ""}, d = 0x285deb0} #4 0x00007fa4cfae9804 in qFatal (msg=<optimized out>) at global/qglobal.cpp:2612 ap = {{gp_offset = 32, fp_offset = 48, overflow_arg_area = 0x7ffcf27f82d0, reg_save_area = 0x7ffcf27f8210}} #5 0x0000000000579bbf in QVector<MidiPort*>::realloc (this=0x29758f8, asize=56747520, aalloc=0) at /usr/include/qt4/QtCore/qvector.h:474 x = {d = 0x2edbe6ff, p = 0x2edbe6ff} #6 0x0000000000579eb2 in QVector<MidiPort*>::detach_helper (this=0x29758f8) at /usr/include/qt4/QtCore/qvector.h:337 No locals. #7 0x0000000000579a24 in QVector<MidiPort*>::detach (this=0x29758f8) at /usr/include/qt4/QtCore/qvector.h:147 No locals. #8 0x00000000005797c2 in QVector<MidiPort*>::end (this=0x29758f8) at /usr/include/qt4/QtCore/qvector.h:250 No locals. #9 0x0000000000579043 in MidiClient::removePort (this=0x29758f0, port=0x7fa4c40a89a8) at /home/zonkmachine/builds/lmms/lmms/src/core/midi/MidiClient.cpp:71 it = 0x7fa4c40a9180 #10 0x000000000057bffa in MidiPort::~MidiPort (this=0x7fa4c40a89a8, __in_chrg=<optimized out>) at /home/zonkmachine/builds/lmms/lmms/src/core/midi/MidiPort.cpp:93 No locals. #11 0x000000000057a109 in MidiController::~MidiController (this=0x7fa4c40a8920, __in_chrg=<optimized out>) at /home/zonkmachine/builds/lmms/lmms/src/core/midi/MidiController.cpp:51 No locals. #12 0x000000000057a166 in MidiController::~MidiController (this=0x7fa4c40a8920, __in_chrg=<optimized out>) at /home/zonkmachine/builds/lmms/lmms/src/core/midi/MidiController.cpp:53 No locals. #13 0x00007fa4cfc0c168 in QObjectPrivate::deleteChildren (this=this@entry=0x26f38e0) at kernel/qobject.cpp:1907 i = 0 reallyWasDeleted = true 

[BaraMGB]

Anyway it's always a good idea to test a pointer before doing something with it. 👍