Hello Nafees, or anyone else affected,

Accepted python2.7 into focal-proposed. The package will build now and
be available at
https://launchpad.net/ubuntu/+source/python2.7/2.7.18-1~20.04.4 in a few
hours, and then in the -proposed repository.

Please help us by testing this new package.  See
https://wiki.ubuntu.com/Testing/EnableProposed for documentation on how
to enable and use -proposed.  Your feedback will aid us getting this
update out to other Ubuntu users.

If this package fixes the bug for you, please add a comment to this bug,
mentioning the version of the package you tested, what testing has been
performed on the package and change the tag from verification-needed-
focal to verification-done-focal. If it does not fix the bug for you,
please add a comment stating that, and change the tag to verification-
failed-focal. In either case, without details of your testing we will
not be able to proceed.

Further information regarding the verification process can be found at
https://wiki.ubuntu.com/QATeam/PerformingSRUVerification .  Thank you in
advance for helping!

N.B. The updated package will be released to -updates after the bug(s)
fixed by this package have been verified and the package has been in
-proposed for a minimum of 7 days.

** Changed in: python2.7 (Ubuntu Focal)
       Status: In Progress => Fix Committed

** Tags added: verification-needed-focal

-- 
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:
  Invalid
Status in python2.7 source package in Bionic:
  Won't Fix
Status in python2.7 source package in Focal:
  Fix Committed
Status in python2.7 source package in Jammy:
  Fix Committed
Status in python2.7 source package in Kinetic:
  Invalid
Status in python2.7 source package in Lunar:
  Invalid
Status in python2.7 source package in Mantic:
  Invalid

Bug description:
  [ Impact ]

  When compiling Python extensions using Python2, CFLAGS optimization
  flags are dropped.

  This behavior has been caused by our update in this patch
  
http://archive.ubuntu.com/ubuntu/pool/universe/p/python2.7/python2.7_2.7.18-1~20.04.3.diff.gz
  which differs from upstream.

  The fix modifies the portion of code in Lib/distutils/sysconfig.py
  which gets the cflags from the environments, and includes the dropped
  OPT flag from get_config_vars().

  [ Test Plan ]

  There will be 2 separate tests for this bug:
  * Ensuring no-change rebuilds are not changed
  * Ensuring local builds are not changed unless environment variable is set

  Test 1) No-change rebuilds

  To test that no-change rebuilds are not changed, the package python-
  stdlib-extensions will be built against the new python2.7, and confirm
  the compiler flags are not altered. This will be a manual test and
  visual inspection of the build logs.

  Test 2) Functional test

  1. Create test container
  $ lxc launch ubuntu:jammy jammy-2002043
  $ lxc shell ubuntu:jammy jammy-2002043

  2. Install required packages
  For Jammy
  # apt update -y && apt install -y python2 python-pip
  For Focal
  # apt update -y && apt install -y python2 python-setuptools

  3. Create test files
  # mkdir testprog
  # cd testprog
  # cat >setup.py <<EOL
  from setuptools import setup, Extension

  setup(
      name="test",
      ext_modules=[Extension("test", sources=["testmodule.c"])],
      zip_safe=False
  )
  EOL
  # cat >testmodule.c <<EOL
  #include <stdio.h>

  int main(void)
  {
          printf("This is test program");
          return 0;
  }
  EOL

  4. Compile a test program
  # python2 setup.py build_ext --inplace

  5. Check CFLAGS
  # python2 -c "import sysconfig; print(sysconfig.get_config_var('CFLAGS'))"
  -fno-strict-aliasing -DNDEBUG -g -fwrapv -O2 -Wall -Wstrict-prototypes 
-Wdate-time -D_FORTIFY_SOURCE=2 -g 
-ffile-prefix-map=/build/python2.7-W40Ff2/python2.7-2.7.18=. -flto=auto 
-ffat-lto-objects -flto=auto -ffat-lto-objects -fstack-protector-strong 
-Wformat -Werror=format-security

  6. Check the flags used to compile the test wheel
  # strings build/lib.linux-x86_64-2.7/test.so  | grep -- -O
  GNU GIMPLE 11.4.0 -mtune=generic -march=x86-64 -g -g -g -g -O2 -fno-openmp 
-fno-openacc -fcf-protection=full -fno-strict-aliasing -fwrapv 
-fstack-protector-strong -ffat-lto-objects -fstack-protector-strong -fPIC 
-fltrans

  7. Install fixed python
  Once updated, this will simply be an apt update && apt upgrade
  # add-apt-repository ppa:mitchdz/python2.7-optimization-flags -y
  # apt install -y python2.7
  # dpkg -s python2.7 | grep Version:
  Version: 2.7.18-13ubuntu1.2~jammy9

  8. Clean build
  # rm -rf build/ test.so

  9. Enable opt-in environment variable
  # export APPLY_LP2002043_UBUNTU_CFLAGS_WORKAROUND=""

  9. Rebuild with new python2.7 installed
  # python2 setup.py build_ext --inplace

  10. Check build flags
  # strings build/lib.linux-x86_64-2.7/test.so  | grep -- -O
  GNU GIMPLE 11.4.0 -mtune=generic -march=x86-64 -g -g -g -g -O2 -O2 
-fno-openmp -fno-openacc -fcf-protection=full -fno-strict-aliasing -fwrapv 
-fstack-protector-strong -ffat-lto-objects -fstack-protector-strong -fPIC 
-fltrans
  GNU C17 11.4.0 -mtune=generic -march=x86-64 -g -g -O2 -fno-strict-aliasing 
-fwrapv -flto -flto -ffat-lto-objects -fstack-protector-strong -fPIC 
-fasynchronous-unwind-tables -fstack-protector-strong -fstack-clash-protection 
-fcf-protection

  [ Where problems could occur ]

  * Changing optimization flags can cause a myriad of unattended side effects, 
but the change being opt-in means the users should be aware a change is being 
made
  * The change is opt-in, so an informative message is printed to the console 
to spread awareness of the issue and how to use the workaround. A questionably 
made CI/CD system might see the new console output and flag it as a failure, so 
it is important to choose wording carefully.

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https://bugs.launchpad.net/ubuntu/+source/python2.7/+bug/2002043/+subscriptions


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