Reviewing this as part of the Sponsor process, but with my SRU Team hat
on.
The only releases python2.7 is present in which are still eligible for
SRUs are focal, jammy, and kinetic.
All of these releases post-date the demotion of python2.7 to universe.
No one should be deploying new code on python2.7 in Ubuntu 20.04 or
later.
For the cflags to have been this way for years without anyone noticing,
I do not think 'high' is a correct bug importance.
We would not rebuild the python extensions in the archive to correct the
CFLAGS they were already built with when released.
For the uncommon case of a user building their extensions, the obvious
workaround is to set any important flags directly instead of relying on
them being inherited from python2.7.
I would not accept this as an SRU in Ubuntu. Therefore I do not think
anyone should proceed with sponsorship. Unsubscribing the sponsors team
and marking wontfix.
** Changed in: python2.7 (Ubuntu Focal)
Status: In Progress => Won't Fix
** Changed in: python2.7 (Ubuntu Jammy)
Status: In Progress => Won't Fix
** Changed in: python2.7 (Ubuntu Kinetic)
Status: In Progress => Won't Fix
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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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