[Octave-bug-tracker] [bug #55052] Memory consumption of figure command going up significantly from 4.2 to 4.4

[John W. Eaton]

Follow-up Comment #14, bug #55052 (project octave):

While investigating this problem, I also noticed a leak when just creating a
figure and exiting Octave.  With current dev sources (revision eb32cf98eed1)
built on my debian system, the problem showed up in the address sanitizer
report like this:


Indirect leak of 1376256 byte(s) in 4 object(s) allocated from:
    #0 0x7f6d250b7ffd in __interceptor_posix_memalign
../../../../src/libsanitizer/asan/asan_malloc_linux.cpp:145
    #1 0x7f6c024ab3be 
(/usr/lib/x86_64-linux-gnu/libQt5Widgets.so.5.15.6+0x723be)


This leak happened for me if I started Octave and executed


figure
quit


If I executed the figure function N times and then quit, the log showed a
larger number of bytes lost in N*4 objects allocated from somewhere in
libQt5Widgets.

>From what I could tell, the leak seemed to happening inside QOpenGLWidget.

In an attempt to find exactly where inside QOpenGLWidget the leak was
happening, I tried installing debugging symbols for the Qt libraries.  But
that forced an upgrade (I'm running debian testing) and then afterward, with
NO changes to Octave, I'm now unable to detect the leak.  I'm not sure what
changed.  I'm now using Qt 5.15.8 and Mesa 22.3.3.  Previously I believe it
was Qt 5.15.2 and Mesa 20.3.5.

Unless someone can point to how we are using QOpenGLWidget incorrectly in a
way that would cause this leak, then I have to conclude that it is either a
bug in Qt (that may be fixed now) or a bug in the OpenGL libraries.

As part of digging into Octave's use of QOpenGLWidget, I did make the
following change, but it is not what made the memory leak disappear for me.

http://hg.savannah.gnu.org/hgweb/octave/rev/d94ceed56929


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