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4. Solution
For cross compiling, there is no `-pthread', so we should explicitly add
`-lpthread' to build multiprocessing.
Peterson tried to do it in the following commit:
...
commit e711cafab13efc9c1fe6c5cd75826401445eb585
Author: Benjamin Peterson <benjamin@python.org>
Date: Wed Jun 11 16:44:04 2008 +0000
 Merged revisions 64104,64117 via svnmerge from
 svn+ssh://pythondev@svn.python.org/python/trunk
...
git show e711cafab13efc9c1fe6c5cd75826401445eb585 -- setup.py
--- a/setup.py
+++ b/setup.py
@@ -1110,6 +1110,56 @@ class PyBuildExt(build_ext):
 
 # _fileio -- supposedly cross platform
 exts.append(Extension('_fileio', ['_fileio.c']))
+ # Richard Oudkerk's multiprocessing module
+ if platform == 'win32': # Windows
+ macros = dict()
+ libraries = ['ws2_32']
+
+ elif platform == 'darwin': # Mac OSX
+ macros = dict(
+ HAVE_SEM_OPEN=1,
+ HAVE_SEM_TIMEDWAIT=0,
+ HAVE_FD_TRANSFER=1,
+ HAVE_BROKEN_SEM_GETVALUE=1
+ )
+ libraries = []
+
+ elif platform == 'cygwin': # Cygwin
+ macros = dict(
+ HAVE_SEM_OPEN=1,
+ HAVE_SEM_TIMEDWAIT=1,
+ HAVE_FD_TRANSFER=0,
+ HAVE_BROKEN_SEM_UNLINK=1
+ )
+ libraries = []
+ else: # Linux and other unices
+ macros = dict(
+ HAVE_SEM_OPEN=1,
+ HAVE_SEM_TIMEDWAIT=1,
+ HAVE_FD_TRANSFER=1
+ )
+ libraries = ['rt']
+
+ if platform == 'win32':
+ multiprocessing_srcs = [ '_multiprocessing/multiprocessing.c',
+ '_multiprocessing/semaphore.c',
+ '_multiprocessing/pipe_connection.c',
+ '_multiprocessing/socket_connection.c',
+ '_multiprocessing/win32_functions.c'
+ ]
+
+ else:
+ multiprocessing_srcs = [ '_multiprocessing/multiprocessing.c',
+ '_multiprocessing/socket_connection.c'
+ ]
+
+ if macros.get('HAVE_SEM_OPEN', False):
+ multiprocessing_srcs.append('_multiprocessing/semaphore.c')
+
+ exts.append ( Extension('_multiprocessing', multiprocessing_srcs,
+ define_macros=list(macros.items()),
+ include_dirs=["Modules/_multiprocessing"]))
+ # End multiprocessing
It defined variable `libraries' and assigned it according to
host_platform, but forgot to pass it to Extension.
So we should correct it, and add `-lpthread' for linux.