[Python-Dev] Import Fails in setup.py On Android

[Frank, Matthew I]

There’s now (as of a couple days ago) a python mobile-sig (https://mail.python.org/mailman/listinfo/mobile-sig).  While that group is much smaller than python-dev and probably not as knowledgeable about the Cpython source base, that’s where you’re going to find folks who have a vested interest in getting Python working on mobile platforms like Android.  (And who would be interested in hearing about your experiences, no matter whether they can help you or not.)

What you are doing (trying to run the entire C compiler toolchain on an Android machine, instead of using the cross-compilers that come in Google’s Android NDK (native development kit)) is way outside the mainstream.  (I.e., you’re not going to find very many people trying to do this here or anywhere.)

Since you compiled all the libraries that you are linking against, there is some possibility (likelihood) that the problem is in one of those libraries, not anywhere in the CPython source.  (Some other library was compiled without the necessary –dl flag.)  The right way to track down this problem (no matter where it is) is to run under gdb and type “where” when the program crashes.

The reason I suspect that the problem is in one of the libraries you compiled before building Python, rather than a problem in the CPython sources or build scripts, is that I don’t have this problem when I cross-compile Python 3.4.2 on a Linux machine, then take the result and copy it over to the Android machine.  I’ve posted instructions and patches for successfully performing this cross compilation (for Android KitKat running on an x86) here: https://github.com/wandering-logic/android_x86_python-3.4.

Best,
-Matt

From: Cyd Haselton [mailto:chaselton at gmail.com]
Sent: Monday, February 02, 2015 3:25 PM
To: Ryan Gonzalez
Cc: Python-Dev
Subject: Re: [Python-Dev] Import Fails in setup.py On Android

No traceback unfortunately...the fakechroot in the environment throws the error and setup.py<http://setup.py> fails.

I'll roll back that change...any idea where I could find info about the original method?
On February 2, 2015 3:17:54 PM CST, Ryan Gonzalez <rymg19 at gmail.com<mailto:rymg19 at gmail.com>> wrote:
In reality, things just got broken even more. I don't know when that patch was created, but it's now very out of date: importlib._bootstrap has no load function. That's what the error you're getting is telling you. Since it isn't getting to load anything, the issue seems "solved". Not really.

What's the full traceback for the undefined reference exception?

On Mon, Feb 2, 2015 at 2:04 PM, Cyd Haselton <chaselton at gmail.com<mailto:chaselton at gmail.com>> wrote:
Update: While waiting for replies I made the change referenced here: https://bugs.python.org/review/5309/diff2/12811:12826/setup.py?context=3&column_width=80

specifically changing
importlib. _bootstrap._SpecMethods(spec).load()
to
importlib._bootstrap.load(spec)

I no longer get a terminating 'undefined reference to dlopen' error, but I do get 'importing extensions failed' errors for each extension...like this:

*** WARNING: importing extension "_pickle" failed with <class 'AttributeError'>: 'module' object has no attribute 'load'

On February 2, 2015 1:36:29 PM CST, Cyd Haselton <chaselton at gmail.com<mailto:chaselton at gmail.com>> wrote:
After fixing a segfault issue (many thanks Ryan) I'm back to the same issue I was having with Python 2.7.8; the newly built python throws an undefined reference to dlopen when running setup.py<http://setup.py>...specifically when importing just-built extensions

I've managed to narrow the problem down to the following line:

importlib._bootstrap._SpecMethods(spec).load()

Googling this brings up a few hits from bugs.python.org<http://bugs.python.org> and not much else. I'm new to Python; any ideas what this does...or where I can read up on it for troubleshooting purposes?

--
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Ryan
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