Thanks for providing the workarounds. While the workarounds work in cases when user is willing to compile extensions from the python package sources and aware of these problems, for the most common cases work arounds are not feasible. There are 100’s of python packages with extension modules and the most common use case is to install them using pip. The general expectation from end user is to have them compile with right flags and work without any extra work. So it’s going to be very challenging for us to communicate end users about this potential problem which only occurs with Python 2 on Ubuntu distributions. I’m also not clear about the regression problem mentioned above. Why would we expect regressions if the patch itself is trying to fix the bug and use right optimizations (in this case O2)?
-- You received this bug notification because you are a member of Ubuntu Touch seeded packages, which is subscribed to python2.7 in Ubuntu. https://bugs.launchpad.net/bugs/2002043 Title: Python extension modules get built using wrong compiler flags with python2 Status in python2.7 package in Ubuntu: In Progress Status in python2.7 source package in Bionic: Won't Fix Status in python2.7 source package in Focal: Won't Fix Status in python2.7 source package in Jammy: Won't Fix Status in python2.7 source package in Kinetic: Won't Fix Status in python2.7 source package in Lunar: Won't Fix Status in python2.7 source package in Mantic: Won't Fix Bug description: Compiling a Python extension using Python2 (Python 2.7.18) is making use of wrong compiler flags, hence dropping required optimizations when required. This is happening only when python2 is installed from Ubuntu's repositories. By default, Python's distutils module uses compiler and linker flags used to compile Python itself to be used to compile extensions. Steps to reproduce: 1) On Ubuntu 20.04, install python2 using apt package manager. 2) After successful installation, verify the CFLAGS variable from sysconfig module. On my machine, the output is Python 2.7.18 (default, Jul 1 2022, 12:27:04) [GCC 9.4.0] on linux2 Type "help", "copyright", "credits" or "license" for more information. >>> import sysconfig >>> sysconfig.get_config_var('CFLAGS') '-fno-strict-aliasing -DNDEBUG -g -fwrapv -O2 -Wall -Wstrict-prototypes -Wdate-time -D_FORTIFY_SOURCE=2 -g -fdebug-prefix-map=/build/python2.7-vvQ8AI/python2.7-2.7.18=. -fstack-protector-strong -Wformat -Werror=format-security ' 3) Build a test extension module using python2 and verify the compilation flags. python2 setup.py build_ext --inplace Output from below command is not matching with our expected above CFLAGS. aarch64-linux-gnu-gcc -pthread -fno-strict-aliasing -Wdate-time -D_FORTIFY_SOURCE=2 -g -fdebug-prefix-map=/build/python2.7-vvQ8AI/python2.7-2.7.18=. -fstack-protector-strong -Wformat -Werror=format-security -fPIC -I/usr/include/python2.7 -c testmodule.c -o build/temp.linux-aarch64-2.7/testmodule.o On further investigation, it looks like Ubuntu's specific patch applied on libpython2.7-stdlib package is altering the original upstream implementation of distutils/sysconfig.py code. Package - https://packages.ubuntu.com/focal/libpython2.7-stdlib Patch - http://archive.ubuntu.com/ubuntu/pool/universe/p/python2.7/python2.7_2.7.18-1~20.04.3.diff.gz Below is the code block which is causing the issue, where the presence of configure_cflags is modifying cflags. This code is result of ubuntu's patch and doesn't come directly from upstream python implementation. File - /usr/lib/python2.7/distutils/sysconfig.py Part of code block: elif configure_cflags: cflags = ' '.join(str(x) for x in (basecflags, configure_cflags, extra_cflags) if x) ldshared = ldshared + ' ' + configure_cflags I don't see problem on Python3 though we have extra code added from patch there as well. Patch used on python3, is not modifying the cflags completely and instead appending new flags to cflags. On python3 (tested on Ubuntu 20.04) File - /usr/lib/python3.8/distutils/sysconfig.py Part of code block which doesn't alter cflags completely elif configure_cflags: cflags = cflags + ' ' + configure_cflags ldshared = ldshared + ' ' + configure_cflags Request to update the python2 patch to behave similar to what is been done on python3. To manage notifications about this bug go to: https://bugs.launchpad.net/ubuntu/+source/python2.7/+bug/2002043/+subscriptions -- Mailing list: https://launchpad.net/~touch-packages Post to : touch-packages@lists.launchpad.net Unsubscribe : https://launchpad.net/~touch-packages More help : https://help.launchpad.net/ListHelp
