ImportError undefined symbol _ZTIPi on `import clr` · Issue #939 · pythonnet/pythonnet · GitHub

Environment

Pythonnet version: v2.4.0
Python version: 3.7.4 but it affects all versions of python I try building the library for
Operating System: Ubuntu 16.04

pythonnet installed inside a virtualenv

Details

Importing the clr library results in an import error:

Traceback (most recent call last):
  File "<string>", line 1, in <module>
ImportError: /usr/lib/libmonosgen-2.0.so.1 undefined symbol: _ZTIPi

Minimal example:

    import clr

This had been working just fine, however it looks like libmonosgen-2.0.so.1 updated on the 9th and I think that's what is the cause of this issue. Rebuilding completely from scratch in a fresh virtualenv doesn't fix this problem.

Looks like this is the same issue as is being discussed here #925 (comment)

Temporary workaround is to revert and pin mono to 5.20.1

It doesn't work for me with older versions of mono:

# rpm -qa | grep mono
mono-extras-5.20.1.19-0.xamarin.3.epel7.x86_64
mono-devel-5.20.1.19-0.xamarin.3.epel7.x86_64
libmono-llvm0-5.20.1.19-0.xamarin.3.epel7.x86_64
mono-web-5.20.1.19-0.xamarin.3.epel7.x86_64
mono-winforms-5.20.1.19-0.xamarin.3.epel7.x86_64
mono-data-5.20.1.19-0.xamarin.3.epel7.x86_64
mono-core-5.20.1.19-0.xamarin.3.epel7.x86_64
libmonosgen-2_0-1-6.4.0.198-0.xamarin.3.epel7.x86_64
mono-winfxcore-5.20.1.19-0.xamarin.3.epel7.x86_64
mono-wcf-5.20.1.19-0.xamarin.3.epel7.x86_64
mono-data-oracle-5.20.1.19-0.xamarin.3.epel7.x86_64
mono-llvm-tools-6.0+mono20190708165219-0.xamarin.1.epel7.x86_64
mono-mvc-5.20.1.19-0.xamarin.3.epel7.x86_64
mono-data-sqlite-5.20.1.19-0.xamarin.3.epel7.x86_64

# python -c 'import clr'
Traceback (most recent call last):
  File "<string>", line 1, in <module>
ImportError: /lib64/libmonosgen-2.0.so.1: undefined symbol: _ZTIPi

# uname -a
Linux pp-mag604.uk8.scp.bskyb.com 3.10.0-1062.4.1.el7.x86_64 #1 SMP Fri Oct 18 17:15:30 UTC 2019 x86_64 x86_64 x86_64 GNU/Linux

# cat /etc/redhat-release
CentOS Linux release 7.7.1908 (Core)

# python -V
Python 2.7.5

# pip show pythonnet
DEPRECATION: Python 2.7 will reach the end of its life on January 1st, 2020. Please upgrade your Python as Python 2.7 won't be maintained after that date. A future version of pip will drop support for Python 2.7. More details about Python 2 support in pip, can be found at https://pip.pypa.io/en/latest/development/release-process/#python-2-support
Name: pythonnet
Version: 2.4.0
Summary: .Net and Mono integration for Python
Home-page: https://pythonnet.github.io/
Author: The Python for .Net developers
Author-email: pythondotnet@python.org
License: MIT
Location: /usr/lib64/python2.7/site-packages
Requires:
Required-by:

Tried with older version as well, didn't work:

# rpm -qa | grep mono
mono-mvc-5.18.1.3-0.xamarin.1.epel7.x86_64
mono-extras-5.18.1.3-0.xamarin.1.epel7.x86_64
mono-devel-5.18.1.3-0.xamarin.1.epel7.x86_64
libmono-llvm0-5.18.1.3-0.xamarin.1.epel7.x86_64
mono-winforms-5.18.1.3-0.xamarin.1.epel7.x86_64
mono-data-5.18.1.3-0.xamarin.1.epel7.x86_64
libmonosgen-2_0-1-6.4.0.198-0.xamarin.3.epel7.x86_64
mono-data-sqlite-5.18.1.3-0.xamarin.1.epel7.x86_64
mono-wcf-5.18.1.3-0.xamarin.1.epel7.x86_64
mono-core-5.18.1.3-0.xamarin.1.epel7.x86_64
mono-winfxcore-5.18.1.3-0.xamarin.1.epel7.x86_64
mono-data-oracle-5.18.1.3-0.xamarin.1.epel7.x86_64
mono-llvm-tools-6.0+mono20190708165219-0.xamarin.1.epel7.x86_64
mono-web-5.18.1.3-0.xamarin.1.epel7.x86_64

How can I make it work?

libmonosgen-2_0-1-6.4.0.198-0.xamarin.3.epel7.x86_64 is the problem, this will not work (if you don't compile things yourself). I don't know why different C++ ABIs are used here but I also have no capacities to debug this.

Thanks @filmor, I didn't notice that package had higher version, now it works, thanks.

Is that still an issue? I just ran into this using pythonnet 2.4 with a dotnetcore2.0 build and having latest mono-devel installed which is, at time of writing, 6.8.0.

I think I figured out the root cause, but don't know yet what is the proper way to fix it: mono/mono#19628

TL;DR; properly linking libmono from Mono 6.8 requires C++ linker or to manually specify C++ stdlib to be linked with C linker (e.g. -lstdc++). I believe workaround is to manually add -lstdc++ to setup.py like this:

...
libs = mono_libs.strip() + " " + glib_libs.strip() + " -lstdc++"
...

I'll wait for Mono response to give us a supported way to do this.

Aaaand after getting pythonnet successfully install with this workaround I hit #1034

The C++ linker does a bit more than just -lstdc++, it's probably enough to just use language="c++" in the Extension constructor.

And the module functions need to be extern "C".

ImportError undefined symbol _ZTIPi on `import clr` · Issue #939 · pythonnet/pythonnet · GitHub

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ImportError undefined symbol _ZTIPi on `import clr` · Issue #939 · pythonnet/pythonnet · GitHub

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ImportError undefined symbol _ZTIPi on import clr #939

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jj-tetraquark commented on Aug 13, 2019

antivirtel commented on Nov 15, 2019

filmor commented on Nov 15, 2019

antivirtel commented on Nov 15, 2019

bneumann commented on Jan 28, 2020

lostmsu commented on Apr 22, 2020

lostmsu commented on Apr 22, 2020

filmor commented on Apr 22, 2020

filmor commented on Apr 23, 2020

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