Traits/UI (chaco) plotting application breaks, when run in a 32-bit Anaconda environment, on 64-bit Ubuntu 16.04

Question

I have a Traits/UI (chaco) plotting application, which runs fine in the root environment of my Anaconda 64-bit installation, on 64-bit Ubuntu 16.04. However, when I try to run it from a 32-bit environment, which I created for testing, it fails.

It appears to be defaulting to the "null" graphical back-end toolkit for some reason, giving me a stack trace, which ends thusly:

File "/home/dbanas/anaconda2/envs/pybert_32/lib/python2.7/site-packages/enable/toolkit.py", line 40, in _init_toolkit format_exception_only(t, v)) ImportError: Unable to import the image backend for the null toolkit (reason: ['ImportError: libGL.so.1: cannot open shared object file: No such file or directory\n']).

So, I realized that I didn't have 32-bit Gtk+ library support installed on my system. I installed that. And, now, the application segment faults when I launch it in my 32-bit environment! Here is the stack trace, from gdb:

> #0  0xf76e7f10 in ?? () from /lib/ld-linux.so.2
> #1  0xf76e8a4b in ?? () from /lib/ld-linux.so.2
> #2  0xf76ea7c9 in ?? () from /lib/ld-linux.so.2
> #3  0xf76f26bf in ?? () from /lib/ld-linux.so.2
> #4  0xf76ee204 in ?? () from /lib/ld-linux.so.2
> #5  0xf76f1f02 in ?? () from /lib/ld-linux.so.2
> #6  0xf74febf5 in ?? () from /lib/i386-linux-gnu/libdl.so.2
> #7  0xf76ee204 in ?? () from /lib/ld-linux.so.2
> #8  0xf74ff30d in ?? () from /lib/i386-linux-gnu/libdl.so.2
> #9  0xf74fec9e in dlopen () from /lib/i386-linux-gnu/libdl.so.2
> #10 0xf76523e6 in _PyImport_GetDynLoadFunc (fqname=0x8b72188 "PyQt4.QtCore", shortname=0x8b7218e "QtCore", 
>     pathname=0x8b73190 "/home/dbanas/anaconda2/envs/pybert_32/lib/python2.7/site-packages/PyQt4/QtCore.so",
> 
>     fp=0x8981b98) at Python/dynload_shlib.c:130
> #11 0xf7636512 in _PyImport_LoadDynamicModule (name=0x8b72188 "PyQt4.QtCore", 
>     pathname=0x8b73190 "/home/dbanas/anaconda2/envs/pybert_32/lib/python2.7/site-packages/PyQt4/QtCore.so",
> 
>     fp=0x8981b98) at ./Python/importdl.c:42
> #12 0xf76343c0 in load_module (name=0x8b72188 "PyQt4.QtCore", fp=<optimized out>, 
>     pathname=0x8b73190 "/home/dbanas/anaconda2/envs/pybert_32/lib/python2.7/site-packages/PyQt4/QtCore.so",
> type=3, 
>     loader=0x0) at Python/import.c:1937
> #13 0xf7634c43 in import_submodule (mod=0xf2b9c26c, subname=0x8b7218e "QtCore", fullname=0x8b72188 "PyQt4.QtCore")
>     at Python/import.c:2725
> #14 0xf7634ebc in load_next (mod=0xf2b9c26c, altmod=0xf2b9c26c, p_name=0xff97d7fc, buf=0x8b72188 "PyQt4.QtCore", 
>     p_buflen=0xff97d7f8) at Python/import.c:2539
> #15 0xf76354fb in import_module_level (level=-1, fromlist=0xf2b33c8c, locals=<optimized out>, globals=0xf2b2de84, 
>     name=0x0) at Python/import.c:2256
> #16 PyImport_ImportModuleLevel (name=0xf2b35264 "PyQt4.QtCore", globals=0xf2b2de84, locals=0xf2b2de84, 
>     fromlist=0xf2b33c8c, level=-1) at Python/import.c:2312
> #17 0xf7615e76 in builtin___import__ (self=0x0, args=0xf2b352fc, kwds=0x0) at Python/bltinmodule.c:49
> #18 0xf75b6188 in PyCFunction_Call (func=0xf72cf78c, arg=0xf2b352fc, kw=0x0) at Objects/methodobject.c:85
> #19 0xf756bb9c in PyObject_Call (func=0xf72cf78c, arg=0xf2b352fc, kw=0x0) at Objects/abstract.c:2547
> #20 0xf7616454 in PyEval_CallObjectWithKeywords (func=0xf72cf78c, arg=0xf2b352fc, kw=0x0) at Python/ceval.c:4221
> #21 0xf761a8aa in PyEval_EvalFrameEx (f=0xf4ba19cc, throwflag=0) at Python/ceval.c:2624
> #22 0xf761ff25 in PyEval_EvalCodeEx (co=0xf2b361d0, globals=0xf2b2de84, locals=0xf2b2de84, args=0x0, argcount=0, 
>     kws=0x0, kwcount=0, defs=0x0, defcount=0, closure=0x0) at Python/ceval.c:3584
> ---Type <return> to continue, or q <return> to quit---

So, I just made some progress:

Making the following code change, in my Python application:

from traits.trait_base import ETSConfig
# ETSConfig.toolkit = 'qt4'
ETSConfig.toolkit = 'wx'

resulted in some helpful error messages being printed out to my console, regarding missing libraries. After several iterations of the sequence:

dpkg -S libGLU.so.1
sudo apt-get install libglu1-mesa:i386

my application came up! However, the colors of the GUI are all screwed up, and when I first launch it, I get a warning dialog with the following message:

iCCP: known incorrect sRGB profile 07:07:37

So, now, I have two questions:

1. How do I fix the colors of the "wx" version?
2. How do I get the "qt4" version to spit out the same sort of helpful messages about missing libraries, instead of just seg. faulting?

Aha! Installing those missing 32-bit libraries has fixed the seg. faulting, and my "qt4" version is running, as well. And, the GUI colors are correct! :)

Answer 1

The problem was missing 32-bit libraries, which is not surprising, since I'm running 64-bit Ubuntu. However, getting the system to tell me which libraries were missing required changing the Python GUI application from the qt4 back-end to the wx back-end, like so:

from traits.trait_base import ETSConfig
# ETSConfig.toolkit = 'qt4'
ETSConfig.toolkit = 'wx'

The 32-bit library installations, which I was prompted to perform by trying to get the "wx" mode running, were enough to get the "qt4" mode running, as well. And, that's important, because the "wx" mode produces goofy GUI colors, while the "qt4" mode produces correct GUI colors.