On 2016-11-14 20:51-0500 Hazen Babcock wrote:
>
> Hello,
>
> All the file based Qt devices are failing for me in ctest. This is an
> example error message:
>
> test 17
> Start 17: examples_pngqt
>
> 17: Test command: /bin/bash "-c"
> "EXAMPLES_DIR=/home/hbabcock/Code/plplot-build/examples
> SRC_EXAMPLES_DIR=/home/hbabcock/Code/plplot/examples
> OUTPUT_DIR=/home/hbabcock/Code/plplot-build/ctest_examples_output_dir
> VC_CTEST_DIRECTORY= ./plplot-test.sh --verbose --front-end=c --device=pngqt"
> 17: Test timeout computed to be: 1500
> 17: Testing front-end c
> 17: x00c
> 17: x01c
> 17: x02c
> 17: ./test_c.sh: line 32: 16690 Segmentation fault (core dumped)
> $DEBUG_CMD "$cdir"/x${index}${lang} -dev $device -o
> "${OUTPUT_DIR}"/x${index}${lang}%n.$dsuffix $options 2> test.error >|
> "${OUTPUT_DIR}"/x${index}${lang}_${dsuffix}.txt
> 17/24 Test #17: examples_pngqt ...................***Failed 0.61 sec
>
>
> The equivalent(?) command line seems to work fine:
> $ ./x03c -dev pngqt -o ex3.png
>
> This is on a linux system.
> Linux Dell-XPS-8100 4.4.0-47-generic #68-Ubuntu SMP Wed Oct 26 19:39:52
> UTC 2016 x86_64 x86_64 x86_64 GNU/Linux
>
> gcc (Ubuntu 5.4.0-6ubuntu1~16.04.4) 5.4.0 20160609
>
Hi Hazen:
Is this segfault occurring for Qt5 or Qt4? If the former, my advice is
to try Qt4 instead.
That is the short response, and now here is the (much) longer one.
My current testing hasn't detected this segfault, but that doesn't
mean much since that is the nature of memory management issues; they
sometimes segfault and they sometimes do not. By the way, the "x02c" prompt
occurs at the start of that portion of the test (see
plplot_test/test_c.sh.in) so that is
the example that segfaulted, not x03c. So you might or might
not see a segfault with
./x02c -dev pngqt -o ex2.png
However, a valgrind run on that here (for the Qt5 case) does show
memory management issues (invalid reads) that do not lead to segfaults
for me but which lead to segfaults (like you have seen) for others.
Furthermore, similar valgrind runs on x00c, x01c and x03c shows no
such memory management issues. I will take a look at that memory
management incompatiblity between the qt devices and example 2 _if_
that issue also shows up for Qt4, but if this is a Qt5-only issue I
won't bother with it because I attribute (see below) Qt5-only memory
management issues to the immaturity of Qt5 compared to Qt4.
An example of this Qt5-only possibility I was dealing with just
today is my current testing shows
qt_example generates valgrind reports about invalid reads for Qt5 but
not Qt4. I looked deeply at that until I realized that Qt5 memory
management issue was generated by the following bog-standard Qt5 code
(taken right out of Qt5 documentation)
QMessageBox msgBox;
msgBox.setText( buf );
msgBox.exec();
to implement that message box used to report interactive selection
coordinates. (That memory management issue appeared when the OK
button was pressed on the message box.) I also discovered our pyqt5
example intermittently segfaulted while clicking the OK button on that
message box while our pyqt4 example does not.
In sum, I attribute all these symptoms and any further Qt5 memory
management issues that do not appear for Qt4 to the continuing
immaturity of Qt5 (at least the Debian Jessie Qt version 5.3.2 I have
access to) and I presume all these Qt5-only symptoms are nothing to do
with the PLplot code and will go away once Qt5 memory management is
properly debugged.
Note, an additional complicating factor here is I am just finishing up
some substantial build-system changes for Qt5 and some smaller changes
for Qt4, and some of my previous commits on this topic may have
screwed up linking which could also introduce memory management
issues. Anyhow, when I make the final commit on this topic, I plan to
check all qt-related results with "ldd -r" to make sure there are no
linking issues left. Furthermore, I plan to run some systematic
valgrind tests for the pngqt case for both Qt4 and Qt5 to see whatever
examples (if any) still have both Qt4 and Qt5 memory management
problems.
Alan
__________________________
Alan W. Irwin
Astronomical research affiliation with Department of Physics and Astronomy,
University of Victoria (astrowww.phys.uvic.ca).
Programming affiliations with the FreeEOS equation-of-state
implementation for stellar interiors (freeeos.sf.net); the Time
Ephemerides project (timeephem.sf.net); PLplot scientific plotting
software package (plplot.sf.net); the libLASi project
(unifont.org/lasi); the Loads of Linux Links project (loll.sf.net);
and the Linux Brochure Project (lbproject.sf.net).
__________________________
Linux-powered Science
__________________________
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