I see a lot of crash reports with Qt5.6.x - try to update Qt and KDE if you can.

And also the nvidia-384 proprietary driver, might be a culprit...

384.90 to be precise.

*** Bug 389308 has been marked as a duplicate of this bug. ***

Created attachment 111065 [details]
New crash information added by DrKonqi

konsole (16.04.3) using Qt 5.6.1

- What I was doing when the application crashed:

You are closing the konsole window after you finish compiling a program when you crash konsole

-- Backtrace (Reduced):
#6  0x00007f6a073e0428 in __GI_raise (sig=sig@entry=6) at ../sysdeps/unix/sysv/linux/raise.c:54
#7  0x00007f6a073e202a in __GI_abort () at abort.c:89
[...]
#9  0x00007f6a0742b37a in malloc_printerr (ar_ptr=<optimized out>, ptr=<optimized out>, str=0x7f6a0753bfe8 "double free or corruption (out)", action=3) at malloc.c:5006
#10 _int_free (av=<optimized out>, p=<optimized out>, have_lock=0) at malloc.c:3867
#11 0x00007f6a0742f53c in __GI___libc_free (mem=<optimized out>) at malloc.c:2968

*** Bug 390429 has been marked as a duplicate of this bug. ***

*** Bug 391737 has been marked as a duplicate of this bug. ***

*** Bug 391506 has been marked as a duplicate of this bug. ***

*** Bug 391643 has been marked as a duplicate of this bug. ***

It might be worthwhile to update the nvidia driver on your system, as this crash seems to happen with version 384.11. Also to report the issue at https://devtalk.nvidia.com/default/board/98/ , as only the nvidia devs can have access to nvidia libs debug symbols being proprietary and all.

*** Bug 393184 has been marked as a duplicate of this bug. ***

I have just experience the same issue when closing Konsole: 

Application: Konsole (konsole), signal: Aborted
Using host libthread_db library "/lib/x86_64-linux-gnu/libthread_db.so.1".
[Current thread is 1 (Thread 0x7fbfd7cae940 (LWP 23363))]

Thread 2 (Thread 0x7fbfd5364700 (LWP 23364)):
#0  __lll_lock_wait_private () at ../sysdeps/unix/sysv/linux/x86_64/lowlevellock.S:95
#1  0x00007fbfe9e472bd in _int_free (av=0x7fbfd0000020, p=0x7fbfd00009a0, have_lock=0) at malloc.c:3962
#2  0x00007fbfe9e4b53c in __GI___libc_free (mem=<optimized out>) at malloc.c:2968
#3  0x00007fbfe2389439 in __nptl_deallocate_tsd () at pthread_create.c:175
#4  0x00007fbfe238a870 in __nptl_deallocate_tsd () at pthread_create.c:326
#5  start_thread (arg=0x7fbfd5364700) at pthread_create.c:346
#6  0x00007fbfe9ece41d in clone () at ../sysdeps/unix/sysv/linux/x86_64/clone.S:109

Thread 1 (Thread 0x7fbfd7cae940 (LWP 23363)):
[KCrash Handler]
#6  0x00007fbfe9dfc428 in __GI_raise (sig=sig@entry=6) at ../sysdeps/unix/sysv/linux/raise.c:54
#7  0x00007fbfe9dfe02a in __GI_abort () at abort.c:89
#8  0x00007fbfe9e3e7ea in __libc_message (do_abort=2, fmt=fmt@entry=0x7fbfe9f57ed8 "*** Error in `%s': %s: 0x%s ***\n") at ../sysdeps/posix/libc_fatal.c:175
#9  0x00007fbfe9e457c3 in malloc_printerr (ar_ptr=0x7fbfd0000020, ptr=0x7fbfd0003fd0, str=0x7fbfe9f54c92 "corrupted double-linked list", action=<optimized out>) at malloc.c:5006
#10 malloc_consolidate (av=av@entry=0x7fbfd0000020) at malloc.c:4175
#11 0x00007fbfe9e47678 in _int_free (av=0x7fbfd0000020, p=<optimized out>, have_lock=0) at malloc.c:4075
#12 0x00007fbfe9e4b53c in __GI___libc_free (mem=<optimized out>) at malloc.c:2968
#13 0x00007fbfd76f2900 in ?? () from /usr/lib/x86_64-linux-gnu/libQt5XcbQpa.so.5
#14 0x00007fbfd76c658b in QXcbConnection::~QXcbConnection() () from /usr/lib/x86_64-linux-gnu/libQt5XcbQpa.so.5
#15 0x00007fbfd76c6ac9 in QXcbConnection::~QXcbConnection() () from /usr/lib/x86_64-linux-gnu/libQt5XcbQpa.so.5
#16 0x00007fbfd76c8216 in QXcbIntegration::~QXcbIntegration() () from /usr/lib/x86_64-linux-gnu/libQt5XcbQpa.so.5
#17 0x00007fbfd76c8329 in QXcbIntegration::~QXcbIntegration() () from /usr/lib/x86_64-linux-gnu/libQt5XcbQpa.so.5
#18 0x00007fbfe6d7dcb3 in QGuiApplicationPrivate::~QGuiApplicationPrivate() () from /usr/lib/x86_64-linux-gnu/libQt5Gui.so.5
#19 0x00007fbfe7333089 in QApplicationPrivate::~QApplicationPrivate() () from /usr/lib/x86_64-linux-gnu/libQt5Widgets.so.5
#20 0x00007fbfe6a7bb48 in QObject::~QObject() () from /usr/lib/x86_64-linux-gnu/libQt5Core.so.5
#21 0x00007fbfe7334e79 in QApplication::~QApplication() () from /usr/lib/x86_64-linux-gnu/libQt5Widgets.so.5
#22 0x00007fbfea1b8d9c in kdemain () from /usr/lib/x86_64-linux-gnu/libkdeinit5_konsole.so
#23 0x00007fbfe9de7830 in __libc_start_main (main=0x400710 <main>, argc=1, argv=0x7fffa75b2308, init=<optimized out>, fini=<optimized out>, rtld_fini=<optimized out>, stack_end=0x7fffa75b22f8) at ../csu/libc-start.c:291
#24 0x0000000000400749 in _start ()

Thank you for the crash report.

As it has been a while since this was reported, can you please test and confirm if this issue is still occurring or if this bug report can be marked as resolved.

I have set the bug status to "needsinfo" pending your response, please change back to "reported" or "resolved/worksforme" when you respond, thank you.

Created attachment 134195 [details]
attachment-21210-0.html

Unfortunately I no longer have access to this machine to test.

On Thu., Dec. 17, 2020, 00:39 Justin Zobel, <bugzilla_noreply@kde.org>
wrote:

> https://bugs.kde.org/show_bug.cgi?id=389272
>
> Justin Zobel <justin.zobel@gmail.com> changed:
>
>            What    |Removed                     |Added
>
> ----------------------------------------------------------------------------
>          Resolution|---                         |WAITINGFORINFO
>              Status|CONFIRMED                   |NEEDSINFO
>
> --- Comment #13 from Justin Zobel <justin.zobel@gmail.com> ---
> Thank you for the crash report.
>
> As it has been a while since this was reported, can you please test and
> confirm
> if this issue is still occurring or if this bug report can be marked as
> resolved.
>
> I have set the bug status to "needsinfo" pending your response, please
> change
> back to "reported" or "resolved/worksforme" when you respond, thank you.
>
> --
> You are receiving this mail because:
> You are on the CC list for the bug.

Dear Bug Submitter,

This bug has been in NEEDSINFO status with no change for at least
15 days. Please provide the requested information as soon as
possible and set the bug status as REPORTED. Due to regular bug
tracker maintenance, if the bug is still in NEEDSINFO status with
no change in 30 days the bug will be closed as RESOLVED > WORKSFORME
due to lack of needed information.

For more information about our bug triaging procedures please read the
wiki located here:
https://community.kde.org/Guidelines_and_HOWTOs/Bug_triaging

If you have already provided the requested information, please
mark the bug as REPORTED so that the KDE team knows that the bug is
ready to be confirmed.

Thank you for helping us make KDE software even better for everyone!

Thanks for the update; changing status.

Remove me from the list please and thank you.

Kevin McErlean

> On Jan 9, 2021, at 10:46 AM, Christoph Feck <bugzilla_noreply@kde.org> wrote:
> 
> https://bugs.kde.org/show_bug.cgi?id=389272
> 
> Christoph Feck <cfeck@kde.org> changed:
> 
>          What    |Removed                     |Added
> ----------------------------------------------------------------------------
>            Status|NEEDSINFO                   |RESOLVED
>        Resolution|WAITINGFORINFO              |WORKSFORME
> 
> --- Comment #16 from Christoph Feck <cfeck@kde.org> ---
> Thanks for the update; changing status.
> 
> -- 
> You are receiving this mail because:
> You are on the CC list for the bug.

Done. Next time, please remove yourself from bugs you no longer want to follow, or change your bugzilla settings.