Hi Mitchell, Do you have any update for this bug?
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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.
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