New submission from Dustin Spicuzza <dus...@virtualroadside.com>:
I'm cross-compiling python to ARM, following instructions from the crossenv project @ https://crossenv.readthedocs.io/en/latest/quickstart.html#build-or-obtain-host-python I was getting pthread related errors when using cross-built extension modules. I realized the issue was that distutils wasn't passing -pthread to gcc. On my native python (Fedora 32 Python 3.8): >>> import pprint, distutils.sysconfig >>> pprint.pprint({i: distutils.sysconfig.get_config_vars(i)[0] for i in ('CC', >>> 'CXX', 'LDSHARED')}) {'CC': 'gcc -pthread', 'CXX': 'g++ -pthread', 'LDSHARED': 'gcc -pthread -shared -Wl,-z,relro -Wl,--as-needed -Wl,-z,now ' '-g -Wl,-z,relro -Wl,--as-needed -Wl,-z,now -g'} In my cross-compiled python environment: >>> import pprint, distutils.sysconfig >>> pprint.pprint({i: distutils.sysconfig.get_config_vars(i)[0] for i in ('CC', >>> 'CXX', 'LDSHARED')}) {'CC': 'arm-frc2020-linux-gnueabi-gcc', 'CXX': 'arm-frc2020-linux-gnueabi-c++', 'LDSHARED': 'arm-frc2020-linux-gnueabi-gcc -shared'} As you can see, no -pthread flag. I went digging in the configure script and found this comment in configure.ac:2110: # Some compilers won't report that they do not support -pthread, # so we need to run a program to see whether it really made the # function available. ... well, that doesn't work when cross-compiling. I looked at some other variables set to override things for cross compiling, and tried adding "ac_cv_pthread_is_default=no ac_cv_pthread=yes ac_cv_cxx_thread=yes" to my cross-compile ./configure, and it's closer: >>> import pprint, distutils.sysconfig >>> pprint.pprint({i: distutils.sysconfig.get_config_vars(i)[0] for i in ('CC', >>> 'CXX', 'LDSHARED')}) {'CC': 'arm-frc2020-linux-gnueabi-gcc -pthread', 'CXX': 'arm-frc2020-linux-gnueabi-c++', 'LDSHARED': 'arm-frc2020-linux-gnueabi-gcc -pthread -shared'} Closer, but not there yet! It appears that the $ac_cv_cxx_thread is not externally settable (unlike ac_cv_pthread), which I guess is because it's not wrapped in a AC_CACHE_VAL macro? It seems that the right fix would be for someone to use AC_CACHE_VAL to allow $ac_cv_cxx_thread to be set externally? I'm happy to cargo cult some code from other parts of configure.ac and make a PR for it, but it's not immediately clear (a) what bad side effects this could cause and (b) what the best mechanism to use to regenerate configure et al is? ---------- components: Cross-Build messages: 377858 nosy: Alex.Willmer, virtuald priority: normal severity: normal status: open title: cxx pthread check is not overrideable versions: Python 3.8 _______________________________________ Python tracker <rep...@bugs.python.org> <https://bugs.python.org/issue41916> _______________________________________ _______________________________________________ Python-bugs-list mailing list Unsubscribe: https://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com
