Add a Linux clang ubsan undefined behavior sanitizer buildbot

[gpshead]

BPO	33321
Nosy	@gpshead, @vadmium

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

Show more details

GitHub fields:

assignee = 'https://github.com/gpshead'
closed_at = <Date 2018-05-20.16:53:22.222>
created_at = <Date 2018-04-20.23:48:21.944>
labels = ['3.8', 'build', '3.7']
title = 'Add a Linux clang ubsan undefined behavior sanitizer buildbot'
updated_at = <Date 2018-05-20.16:53:22.222>
user = 'https://github.com/gpshead'

bugs.python.org fields:

activity = <Date 2018-05-20.16:53:22.222>
actor = 'gregory.p.smith'
assignee = 'gregory.p.smith'
closed = True
closed_date = <Date 2018-05-20.16:53:22.222>
closer = 'gregory.p.smith'
components = ['Build']
creation = <Date 2018-04-20.23:48:21.944>
creator = 'gregory.p.smith'
dependencies = []
files = []
hgrepos = []
issue_num = 33321
keywords = ['buildbot']
message_count = 3.0
messages = ['315542', '317088', '317188']
nosy_count = 2.0
nosy_names = ['gregory.p.smith', 'martin.panter']
pr_nums = []
priority = 'normal'
resolution = 'fixed'
stage = 'resolved'
status = 'closed'
superseder = None
type = 'compile error'
url = 'https://bugs.python.org/issue33321'
versions = ['Python 2.7', 'Python 3.7', 'Python 3.8']

[gpshead]

CPython needs to be regularly built and vetted for C undefined behavior.

CFLAGS=-fsanitize=undefined LDFLAGS=-fsanitize=undefined CC=clang LD=clang ./configure

is all it takes to start with.

if you do this today, test_ctypes will knock your socks off with errors. We should detect this type of build and intentionally skip its tests on ubsan, tracking that with another yet to be filed issue.

I'll look into having Google run one.

[vadmium]

Perhaps your “ctypes” problems may be helped by my ctypes_v2.patch in bpo-1621. Or perhaps they are already documented in bpo-15119 and/or bpo-28169.

[gpshead]

A buildbot is up and running:
http://buildbot.python.org/all/#/builders?tags=%2Bubsan

in order to see the errors though, you have to manually string search for "runtime error" in the giant test logs stdout.

At the moment, Modules/_ctypes/_ctypes.c dominates the error lists with misaligned access problems - I suggest filtering that out and looking for the others to start with for anyone working on these issues.