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[Launchpad Bug Tracker <1783252@xxxxxxxxxxxxxxxxxx>]

This bug was fixed in the package gcc-5 - 5.4.0-6ubuntu1~16.04.11

---------------
gcc-5 (5.4.0-6ubuntu1~16.04.11) xenial; urgency=medium

  * Backport upstream revision r235876 to correct PIC_OFFSET_TABLE_REGNUM
    on ppc64el.
    LP: #1783252

 -- Dimitri John Ledkov <xnox@xxxxxxxxxx>  Wed, 01 Aug 2018 22:22:10
+0100

** Changed in: gcc-5 (Ubuntu Xenial)
       Status: Fix Committed => Fix Released

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https://bugs.launchpad.net/bugs/1783252

Title:
  gcc on ppc64le has bogus r30 register handling, as exposed by greenlet
  0.4.14 will not build on ppc64le

Status in The Ubuntu-power-systems project:
  Fix Committed
Status in gcc-5 package in Ubuntu:
  Fix Released
Status in gcc-6 package in Ubuntu:
  Fix Released
Status in python-greenlet package in Ubuntu:
  Fix Released
Status in gcc-5 source package in Xenial:
  Fix Released
Status in gcc-5 source package in Bionic:
  Confirmed
Status in gcc-6 source package in Cosmic:
  Fix Committed

Bug description:
  [Impact]

   * GCC has a minor bug w.r.t. clobber r30 register in PIC binaries.
   * A patch to fix this has been upstream in 6+
   * But it is not in gcc-5.4 as used on xenial
   * This prevents compiling future-proof and correct greenlet code, on Ubuntu 16.04 LTS as used by current and supported Openstack Queens release on ppc64el
   * Whilst backported greenlet is available via the cloud archive for binary usage, the toolchain is still technically incorrect, and thus hinders using Ubuntu 16.04 LTS as workers in upstream Openstack CI
   * As a wishlist it would be nice to backport this one small gcc patch as an SRU

  [Test Case]

   * git clone https://github.com/python-greenlet/greenlet
   * cd greenlet
   * ./setup.py build
  Expect success

  Current result failure:

  creating build/temp.linux-ppc64le-2.7
  powerpc64le-linux-gnu-gcc -pthread -DNDEBUG -g -fwrapv -O2 -Wall -Wstrict-prototypes -fno-strict-aliasing -Wdate-time -D_FORTIFY_SOURCE=2 -g -fstack-protector-strong -Wformat -Werror=format-security -fPIC -I/usr/include/python2.7 -c greenlet.c -o build/temp.linux-ppc64le-2.7/greenlet.o -fno-tree-dominator-opts
  In file included from slp_platformselect.h:16:0,
                   from greenlet.c:343:
  platform/switch_ppc64_linux.h: In function 'slp_switch':
  platform/switch_ppc64_linux.h:80:5: error: PIC register clobbered by 'r30' in 'asm'
       __asm__ volatile ("" : : : REGS_TO_SAVE);
       ^
  platform/switch_ppc64_linux.h:95:5: error: PIC register clobbered by 'r30' in 'asm'
       __asm__ volatile ("" : : : REGS_TO_SAVE);
       ^
  error: command 'powerpc64le-linux-gnu-gcc' failed with exit status 1

  
  [Regression Potential] 

   * Upstream cherrypick present in later releases including bionic
  https://gcc.gnu.org/git/?p=gcc.git;a=commitdiff;h=9213244550335bcb2b8590a0d7d58ac74c932361

  
  [Other Info]
   
   * Original bug report

  
  == Comment: #0 - William M. Edmonds <edmondsw@xxxxxxxxxx> - 2018-07-23 16:21:41 ==
  ---Problem Description---
  greenlet 0.4.14 will not build on ppc64le

  Opened https://github.com/python-greenlet/greenlet/issues/136 because
  attempting to build bdist_wheel for greenlet 0.4.14 on ppc64le Ubuntu
  16.04 LTS yields the following error:

  running build
  running build_ext
  building 'greenlet' extension
  creating build
  creating build/temp.linux-ppc64le-2.7
  powerpc64le-linux-gnu-gcc -pthread -DNDEBUG -g -fwrapv -O2 -Wall -Wstrict-prototypes -fno-strict-aliasing -Wdate-time -D_FORTIFY_SOURCE=2 -g -fstack-protector-strong -Wformat -Werror=format-security -fPIC -I/usr/include/python2.7 -c greenlet.c -o build/temp.linux-ppc64le-2.7/greenlet.o -fno-tree-dominator-opts
  In file included from slp_platformselect.h:16:0,
                      from greenlet.c:343:
     platform/switch_ppc64_linux.h: In function 'slp_switch':
     platform/switch_ppc64_linux.h:80:5: error: PIC register clobbered by 'r30' in 'asm'
          __asm__ volatile ("" : : : REGS_TO_SAVE);
          ^
     platform/switch_ppc64_linux.h:95:5: error: PIC register clobbered by 'r30' in 'asm'
          __asm__ volatile ("" : : : REGS_TO_SAVE);
          ^
     error: command 'powerpc64le-linux-gnu-gcc' failed with exit status 1```

  But the greenlet community is saying this is a gcc bug and it would
  not be safe to revert the greenlet change that exposed this issue. I
  have no idea whether that is true or not. Supposedly this should be
  fixed by
  https://gcc.gnu.org/git/?p=gcc.git;a=commitdiff;h=9213244550335bcb2b8590a0d7d58ac74c932361
  but that fix is not present in the latest version of gcc (5.4.0)
  available for Ubuntu 16.04 LTS.

  ---uname output---
  unavailable due to lab outage

  Machine Type = unavailable due to lab outage

  ---Debugger---
  A debugger is not configured

  ---Steps to Reproduce---
  This should be reproducible with `git clone git://github.com/python-greenlet/greenlet; cd greenlet; python setup.py bdist_wheel`, though it was originally found using pypi rather than github and with a more complicated (scripted) command as detailed in the greenlet bug description.

  Contact Information = Matthew Edmonds / edmondsw@xxxxxxxxxx

  Userspace tool common name: greenlet

  The userspace tool has the following bit modes: no idea

  Userspace rpm: N/A

  Userspace tool obtained from project website:  0.4.14

  *Additional Instructions for Matthew Edmonds / edmondsw@xxxxxxxxxx:
  -Attach ltrace and strace of userspace application.

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