Segmentation fault while calling subplot function

[seb.belese]

GNU Octave, version 3.8.0-5ubuntu5
Ubuntu Trusty Tahr, kernel 3.13.0-16-generic

When calling the subplot function in octave (new session), I directly get a segmentation fault and the program crashes:

octave:1> subplot(2,1,1)
panic: Segmentation fault -- stopping myself...
attempting to save variables to 'octave-workspace'...
save to 'octave-workspace' complete
Erreur de segmentation

[seb.belese (seb-belese)]

Actually, it also crashes with the plot function:

octave:2> plot([1:5,3:6])
panic: Segmentation fault -- stopping myself...
attempting to save variables to 'octave-workspace'...
save to 'octave-workspace' complete
Erreur de segmentation

Calling:
figure
does not crash and produces a blank figure as expected. However, trying to plot something on it makes octave crash.

[seb.belese (seb-belese)]

The problem is related to fltk, since I do not get the segfault if I use:
graphics_toolkit("gnuplot");

Sorry for multiple comments...

[Mike Miller (mtmiller)]

Thank you for taking the time to report this bug and helping to make Ubuntu better. Please try to obtain a backtrace following the instructions at http://wiki.ubuntu.com/DebuggingProgramCrash and upload the backtrace (as an attachment) to the bug report. This will greatly help us in tracking down your problem.

It would also help if you could describe what model of video card you have and what graphics drivers you are using.

Does the crash occur if you run "graphics_toolkit gnuplot" before opening the first figure?

[Mike Miller (mtmiller)]

Ok good, thanks for testing with gnuplot and confirming it only crashes with fltk. The graphics driver and device information and a full stack trace with debug symbols will be helpful.

[seb.belese (seb-belese)]

I have a radeon video card radeon with open source driver:
        description: VGA compatible controller
       produit: Whistler [Radeon HD 6630M/6650M/6750M/7670M/7690M]
       fabriquant: Advanced Micro Devices, Inc. [AMD/ATI]
       identifiant matériel: 0
       information bus: pci@0000:01:00.0
       version: 00
       bits: 64 bits
       horloge: 33MHz
       fonctionnalités: pm pciexpress msi vga_controller bus_master cap_list rom
       configuration: driver=radeon latency=0
       ressources: irq:49 mémoire:90000000-9fffffff mémoire:b0800000-b081ffff portE/S:2000(taille=256) mémoire:b0820000-b083ffff

Running on a macbook pro 8,2 (EFI mode)

[Mike Miller (mtmiller)]

Thanks for the extra information. I know very little about Radeon graphics configurations, but this looks to me suspiciously like a poorly configured Radeon setup that does not fully support OpenGL graphics. Having a working OpenGL configuration is a prerequisite for using the FLTK plotting backend. There is an open upstream bug report about gracefully reporting an error under such conditions, so this is a known problem.

It appears to me that we can pursue this crash from one of two angles:
1. Continue treating this as a bug that Octave should not crash with a segmentation fault when sufficient OpenGL support is lacking. The outcome of a potential fix for this bug would simply be an error message saying that you are unable to use FLTK.
2. Convert this to a support question and we address your system configuration so you can get OpenGL and FLTK plots working with your Radeon video card.

Which of these look most appropriate to you?

Of course if you *do* know about Radeon graphics configuration and you can prove that your system *is* correctly configured for full OpenGL support, and Octave still crashes using FLTK, then something else is going on here.

[seb.belese (seb-belese)]

Thanks for taking the time to deal with this issue.

I will try to identify what is wrong with my config since it does not seem related to Octave. Other OpenGl applications work with no problem, but there may be a more specific issue. I have a rather exotic setup.

Even though this is not a high priority, an error message from Octave would indeed be more appropriate than a segfault.

[Joshua Bakita (bakitajoshua)]

Thank you for taking the time to report this bug and helping to make Ubuntu better. This particular bug has already been reported and is a duplicate of bug #1293876, so it is being marked as such. Please look at the other bug report to see if there is any missing information that you can provide, or to see if there is a workaround for the bug. Additionally, any further discussion regarding the bug should occur in the other report. Feel free to continue to report any other bugs you may find.