"SO" config var not getting set

[msabramo]

BPO	19555
Nosy	@warsaw, @doko42, @vstinner, @msabramo
Files	issue19555.txt

^{Note: these values reflect the state of the issue at the time it was migrated and might not reflect the current state.}

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GitHub fields:

assignee = 'https://github.com/warsaw'
closed_at = <Date 2013-11-22.16:09:39.550>
created_at = <Date 2013-11-11.17:29:57.624>
labels = ['type-bug', 'library']
title = '"SO" config var not getting set'
updated_at = <Date 2014-03-09.22:50:24.773>
user = 'https://github.com/msabramo'

bugs.python.org fields:

activity = <Date 2014-03-09.22:50:24.773>
actor = 'python-dev'
assignee = 'barry'
closed = True
closed_date = <Date 2013-11-22.16:09:39.550>
closer = 'barry'
components = ['Distutils']
creation = <Date 2013-11-11.17:29:57.624>
creator = 'Marc.Abramowitz'
dependencies = []
files = ['32577']
hgrepos = []
issue_num = 19555
keywords = []
message_count = 12.0
messages = ['202634', '202637', '202638', '202639', '202648', '202649', '202650', '203701', '203735', '203793', '203865', '212996']
nosy_count = 5.0
nosy_names = ['barry', 'doko', 'vstinner', 'python-dev', 'Marc.Abramowitz']
pr_nums = []
priority = 'normal'
resolution = 'fixed'
stage = None
status = 'closed'
superseder = None
type = 'behavior'
url = 'https://bugs.python.org/issue19555'
versions = ['Python 3.4']

[msabramo]

I just installed Python 3.0a4 from source on an Ubuntu system and noticed that it doesn't seem to set the distutils.sysconfig config var: "SO":

vagrant@ubuntu:~/src/Python-3.4.0a4$ python3.4
Python 3.4.0a4 (default, Nov 11 2013, 17:11:59)
[GCC 4.6.3] on linux
Type "help", "copyright", "credits" or "license" for more information.
>>> from distutils import sysconfig
>>> sysconfig.get_config_var("SO")
>>> sysconfig.get_config_var("SO") is None
True

This worked fine for me in Python 3.3:

vagrant@ubuntu:~/src/Python-3.4.0a4$ python3.3
Python 3.3.2 (default, May 16 2013, 18:32:41)
[GCC 4.6.3] on linux
Type "help", "copyright", "credits" or "license" for more information.
>>> from distutils import sysconfig
>>> sysconfig.get_config_var("SO")
'.so'

[warsaw]

Indeed, this happens for me too in default head.

[warsaw]

Never mind, this is an intentional change:

• Issue bpo-16754: Fix the incorrect shared library extension on linux. Introduce
  two makefile macros SHLIB_SUFFIX and EXT_SUFFIX. SO now has the value of
  SHLIB_SUFFIX again (as in 2.x and 3.1). The SO macro is removed in 3.4.

Although this does introduce some backward compatibility issues. Perhaps sysconfig.get_config_var('SO') should be deprecated in 3.4 and removed in 3.5.

[msabramo]

Thanks Barry, for tracking down that this is intentional.

I wonder how one gets this value in Python code now? For example, the reason I stumbled upon this in the first place is that there is some code in PyCrypto (https://github.com/dlitz/pycrypto/blob/master/lib/Crypto/SelfTest/PublicKey/test_RSA.py#L464) that uses get_config_var("SO") thusly:

    except ImportError:
        from distutils.sysconfig import get_config_var
        import inspect
        _fm_path = os.path.normpath(os.path.dirname(os.path.abspath(
            inspect.getfile(inspect.currentframe())))
            +"/../../PublicKey/_fastmath"+get_config_var("SO"))
        if os.path.exists(_fm_path):
            raise ImportError("While the _fastmath module exists, importing "+
                "it failed. This may point to the gmp or mpir shared library "+
                "not being in the path. _fastmath was found at "+_fm_path)

What would be the way to express this now in Python >= 3.4?

[warsaw]

Here's a patch, sans NEWS and any docs.

[warsaw]

Note that obviously the DeprecationWarning is not raised if you do

sysconfig.get_config_vars()['SO']

but it still gets mapped to EXT_SUFFIX in that case.

[warsaw]

On Nov 11, 2013, at 06:27 PM, Marc Abramowitz wrote:

What would be the way to express this now in Python >= 3.4?

For now, use sysconfig.get_config_var('EXT_SUFFIX') though if no one objects
to my patch, I'll restore 'SO' for 3.4. We'll add a DeprecationWarning and
get rid of it in 3.5.

[python-dev]

New changeset fedc2b8fbb6e by Barry Warsaw in branch 'default':

• Issue bpo-19555: Restore sysconfig.get_config_var('SO'), with a
  http://hg.python.org/cpython/rev/fedc2b8fbb6e