[Bug 1783252] Comment bridged from LTC Bugzilla

[bugproxy]

------- Comment From edmondsw at us.ibm.com 2018-08-01 09:45 EDT-------
Current versions of OpenStack, e.g. Queens [1], require at least greenlet 0.4.10, so the 0.4.9 version that is the latest currently packaged for Ubuntu 16.04 is insufficient. Therefore, in order to run OpenStack's devstack project on Ubuntu 16.04, which is commonly done in OpenStack development and in OpenStack CI (continuous integration) automation, greenlet has to be pip installed, which fails with this issue because pip install will pull the latest release by default.

But let's step back for a minute. Top priority here should be to
determine whether this is really a gcc bug or a greenlet bug. Does
Ubuntu agree with the greenlet community that this is a gcc bug? At
least one greenlet contributor that I spoke to did not agree with that
assessment, so I don't think this is a given. And I was still able to
reproduce this bug after upgrading gcc-5, installing gcc-6, installing
gcc-7, and installing gcc-8 from the toolchain test builds PPA.

If this is a greenlet bug, then it needs to be fixed by the greenlet
community regardless of any Ubuntu versioning/packaging, and we'll all
be better off determining that sooner rather than later.

On the other hand, if it is a gcc bug, then it would presumably affect
other things besides greenlet, so that risk would need to be assessed
and balanced against the risk of patching gcc on Ubuntu 16.04.

I have not tested this on Ubuntu 18.04, so I cannot say whether the same
issue exists there or not.

[1] https://github.com/openstack/requirements/blob/stable/queens/global-
requirements.txt#L73

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

Title:
  greenlet 0.4.14 will not build on ppc64le

Status in The Ubuntu-power-systems project:
  Won't Fix
Status in gcc-5 package in Ubuntu:
  New

Bug description:
  == Comment: #0 - William M. Edmonds <edmondsw at us.ibm.com> - 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 at us.ibm.com 
   
  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 at us.ibm.com:
  -Attach ltrace and strace of userspace application.

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