The select and time modules use functions from libm, but do not link against it.

• selectmodule.c calls ceil(3) in pyepoll_poll()
• timemodule.c calls fmod(3) and floor(3) in floatsleep()

Note: This causes problems at least when running on android, where the system is unable to find the symbols when loading the modules at runtime.

Additionally,

• audioop calls floor()
• _ctypes_test calls sqrt()

Patch attached.

audioop_ctypes_test_link_with_libm.patch

+ libraries=['m'])

Why not using math_libs here? It would also be nice to add a comment explaining why libm is needed in each module.

Can someone please combine both patches?

> audioop_ctypes_test_link_with_libm.patch

•                         libraries=['m'])
  

Why not using math_libs here?

math_libs is defined in detect_modules(). But the _ctypes_test
extension is defined in a different function: detect_ctypes().

The other option, would be to define math_libs=['m'] directly above this line and then use it once. I didn't think that added clarity, but I'd be happy to do it that way if it fits better with standard style.

It would also be nice to add a comment explaining why libm is needed in each module.

Done.

Can someone please combine both patches?

Done.

Bump. For rev c6930661599b timemodule.c and selectmodule.c no longer calls libm functions, while audioop.c and _ctypes_test.c still do. I have my updated patch here based on previous patches. Note that the introduction of detect_math_libs() is my naive try. Its naming and position in setup.py may need more consideration.

Here's the result before and after my patch.

Before:
shell@GT-N7000:/data/local/tmp $ python3
Python 3.6.0a0 (default:6a8fbb97c8d8+, Nov 26 2015, 18:42:29) 
[GCC 4.9 20140827 (prerelease)] on linux
Type "help", "copyright", "credits" or "license" for more information.
>>> import select 
>>> import time
>>> import audioop
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
ImportError: dlopen failed: cannot locate symbol "floor" referenced by "audioop.cpython-36m-arm-linux-gnueabi.so"...
>>> import _ctypes_test
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
ImportError: dlopen failed: cannot locate symbol "sqrt" referenced by "_ctypes_test.cpython-36m-arm-linux-gnueabi.so"...
>>> 

After:

shell@GT-N7000:/data/local/tmp $ python3
Python 3.6.0a0 (default:c6930661599b+, Nov 26 2015, 19:10:15) 
[GCC 4.9 20140827 (prerelease)] on linux
Type "help", "copyright", "credits" or "license" for more information.
>>> import time
>>> import selectr
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
ImportError: No module named 'selectr'
>>> import select 
>>> import audioop
>>> import _ctypes_test
>>> 

Tested on Samsung Galaxy Note GT-N7000 with my custom build of CyanogenMod 11.0

Well, the hg revision of Python in two tests are different, because I hg pull -u each time I build.

The _datetime module also calls functions in libm: delta_new() uses
round() and accum() uses modf().

The attached patch updates setup.py for all the modules that use libm.

The approach with a helper function is better. See https://github.com/yan12125/python3-android/blob/038271d/mk/python/modules-link-libm.patch.

By the way, I have verified there are no libraries referencing libm functions with https://github.com/yan12125/python3-android/blob/cpython-hg/devscripts/import_all.py

New changeset f92fea23161d by Victor Stinner in branch '3.5':
setup.py: add missing libm dependency
https://hg.python.org/cpython/rev/f92fea23161d

New changeset 3a9b47b062b9 by Victor Stinner in branch 'default':
Merge 3.5: Issue bpo-21668
https://hg.python.org/cpython/rev/3a9b47b062b9

I pushed ext_modules_libm.patch with the helper function proposed by Chi Hsuan Yen in https://github.com/yan12125/python3-android/blob/038271d/mk/python/modules-link-libm.patch.

Tell me if it's not enough. I hope that it will make CPython a little bit more portable ;-)

The patch should be acknowledged in Misc/NEWS to Chi Hsuan Yen and not to me.

New changeset f76753f26982 by Victor Stinner in branch 'default':
Issue bpo-21668: Fix author of the patch.
https://hg.python.org/cpython/rev/f76753f26982

New changeset 7530caa5ed1a by Victor Stinner in branch 'default':
Issue bpo-21668: Add also Chi Hsuan Yen to Misc/ACKS
https://hg.python.org/cpython/rev/7530caa5ed1a

Xavier de Gaye: "The patch should be acknowledged in Misc/NEWS to Chi Hsuan Yen and not to me."

Oh sorry. I see 4 authors in attached patches, I picked the latest. Thank you to all authors for your contribution on this issue ;-) I fixed the author in Misc/NEWS.