python-gdb.py must be updated for the new Python 3.6 compact dict

[vstinner]

BPO	28023
Nosy	@jcea, @vstinner, @ned-deily, @methane
PRs	[Do Not Merge] Convert Misc/NEWS so that it is managed by towncrier #552
Files	dict_gdb.patch dict_gdb2.patch

^{Note: these values reflect the state of the issue at the time it was migrated and might not reflect the current state.}

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GitHub fields:

assignee = 'https://github.com/methane'
closed_at = <Date 2016-11-22.14:53:15.985>
created_at = <Date 2016-09-08.16:25:40.238>
labels = ['3.7', 'release-blocker']
title = 'python-gdb.py must be updated for the new Python 3.6 compact dict'
updated_at = <Date 2017-05-17.17:34:55.171>
user = 'https://github.com/vstinner'

bugs.python.org fields:

activity = <Date 2017-05-17.17:34:55.171>
actor = 'jcea'
assignee = 'methane'
closed = True
closed_date = <Date 2016-11-22.14:53:15.985>
closer = 'vstinner'
components = ['Demos and Tools']
creation = <Date 2016-09-08.16:25:40.238>
creator = 'vstinner'
dependencies = []
files = ['44959', '45589']
hgrepos = []
issue_num = 28023
keywords = ['patch', 'needs review']
message_count = 15.0
messages = ['275058', '275064', '278028', '278295', '280739', '281346', '281359', '281453', '281460', '281462', '281464', '281471', '281474', '281478', '281488']
nosy_count = 5.0
nosy_names = ['jcea', 'vstinner', 'ned.deily', 'methane', 'python-dev']
pr_nums = ['552']
priority = 'release blocker'
resolution = 'fixed'
stage = 'resolved'
status = 'closed'
superseder = None
type = None
url = 'https://bugs.python.org/issue28023'
versions = ['Python 3.6', 'Python 3.7']

[vstinner]

The issue bpo-27350 changed the design of Python dictionaries to make them compact. python-gdb.py must be updated for the new structure of Python dict.

[python-dev]

New changeset 0bd618fe0639 by Victor Stinner in branch 'default':
Implement compact dict
https://hg.python.org/cpython/rev/0bd618fe0639

[methane]

I've fixed dict support of python-gdb.py.

But I found py-bt and py-bt-full are broken. They doesn't show builtin method.
I think it's because FASTCALL. But I'm not sure.
I just skip the test for py-bt in attached patch.

[methane]

Could someone review this before 3.6b2?
Without this patch, python-gdb.py causes many RuntimeError.

[methane]

@Haypo, would you review this patch?

[methane]

ping

[vstinner]

I reviewed dict_gdb.patch.

[vstinner]

dict_gdb2.patch LGTM. Can you please follow Ned's instructions to get this change merged into 3.6 final? python-gdb.py is an important tool and it's completly broken. The patch cannot make python-gdb.py worse :-D (More seriously, it fixes python-gdb.py.)

[methane]

https://mail.python.org/pipermail/python-committers/2016-November/004065.html

The 3.6 branch in the cpython repo is now available again but, as noted, *only* for reviewed release critical fixes appropriate for the 3.6.0 final and for final 3.6.0 doc updates!

So now I think I can commit this for now.

[python-dev]

New changeset 4f6fb9e47f6b by INADA Naoki in branch '3.6':
Issue bpo-28023: Fix python-gdb.py didn't support new dict implementation
https://hg.python.org/cpython/rev/4f6fb9e47f6b

New changeset c51045920410 by INADA Naoki in branch 'default':
Issue bpo-28023: Fix python-gdb.py didn't support new dict implementation
https://hg.python.org/cpython/rev/c51045920410

[vstinner]

test_gdb failed on a lot of buildbots. Examples:

• http://buildbot.python.org/all/builders/PPC64%20Fedora%203.x/builds/2089
• http://buildbot.python.org/all/builders/AMD64%20Debian%20PGO%203.6/builds/330
• http://buildbot.python.org/all/builders/x86%20Gentoo%20Non-Debug%20with%20X%203.6/builds/287

Extract of the Gentoo non-debug:

(...)
GNU gdb (Gentoo 7.10.1 vanilla) 7.10.1
(...)
======================================================================
FAIL: test_NULL_ob_type (test.test_gdb.PrettyPrintTests)
Ensure that a PyObject* with NULL ob_type is handled gracefully
----------------------------------------------------------------------

Traceback (most recent call last):
  File "/buildbot/buildarea/3.6.ware-gentoo-x86.nondebug/build/Lib/test/test_gdb.py", line 490, in test_NULL_ob_type
    'set v->ob_type=0')
  File "/buildbot/buildarea/3.6.ware-gentoo-x86.nondebug/build/Lib/test/test_gdb.py", line 461, in assertSane
    cmds_after_breakpoint=cmds_after_breakpoint)
  File "/buildbot/buildarea/3.6.ware-gentoo-x86.nondebug/build/Lib/test/test_gdb.py", line 240, in get_gdb_repr
    import_site=import_site)
  File "/buildbot/buildarea/3.6.ware-gentoo-x86.nondebug/build/Lib/test/test_gdb.py", line 218, in get_stack_trace
    self.assertEqual(unexpected_errlines, [])
AssertionError: Lists differ: ["Python Exception <class 'gdb.error'> Can[663 chars].: "] != []

First list contains 10 additional elements.
First extra element 0:
"Python Exception <class 'gdb.error'> Cannot convert value to int.: "

Diff is 745 characters long. Set self.maxDiff to None to see it.