curses: calling addch() with an 1-length str segfaults with ncurses6 compiled with --enable-ext-colors

[yyt16384]

BPO	28549
Nosy	@Yhg1s, @serhiy-storchaka, @yyt16384
PRs	[Do Not Merge] Convert Misc/NEWS so that it is managed by towncrier #552
Files	curses_setcchar.patch curses_setcchar_2.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/serhiy-storchaka'
closed_at = <Date 2016-10-30.21:02:55.466>
created_at = <Date 2016-10-28.17:51:09.852>
labels = ['extension-modules', '3.7', 'type-crash']
title = 'curses: calling addch() with an 1-length str segfaults with ncurses6 compiled with --enable-ext-colors'
updated_at = <Date 2017-03-31.16:36:30.780>
user = 'https://github.com/yyt16384'

bugs.python.org fields:

activity = <Date 2017-03-31.16:36:30.780>
actor = 'dstufft'
assignee = 'serhiy.storchaka'
closed = True
closed_date = <Date 2016-10-30.21:02:55.466>
closer = 'serhiy.storchaka'
components = ['Extension Modules']
creation = <Date 2016-10-28.17:51:09.852>
creator = 'yyt16384'
dependencies = []
files = ['45254', '45260']
hgrepos = []
issue_num = 28549
keywords = ['patch']
message_count = 7.0
messages = ['279620', '279627', '279644', '279660', '279678', '279747', '279750']
nosy_count = 4.0
nosy_names = ['twouters', 'python-dev', 'serhiy.storchaka', 'yyt16384']
pr_nums = ['552']
priority = 'normal'
resolution = 'fixed'
stage = 'resolved'
status = 'closed'
superseder = None
type = 'crash'
url = 'https://bugs.python.org/issue28549'
versions = ['Python 3.5', 'Python 3.6', 'Python 3.7']

[yyt16384]

When addch() is called with an 1-length str, it is converted into a cchar_t. Ncurses6 adds a new field ext_color to cchar_t if it is enabled at compile time, and it is not initialized here, which causes various problems like segfaults or wrong display of characters.

[serhiy-storchaka]

The _curses module uses direct access to cchar_t fields. Proposed patch makes it using setcchar. Does it fixes this issue Yutao?

[yyt16384]

It fails to compile for me. setcchar should take a cchar_t* and a const wchar_t* instead.

[serhiy-storchaka]

Ah, sorry. libncursesw5-dev was not installed on my computer.

Please try updated patch.

[yyt16384]

Yes, it works for me now.

[python-dev]

New changeset d06bf822585c by Serhiy Storchaka in branch '3.5':
Issue bpo-28549: Fixed segfault in curses's addch() with ncurses6.
https://hg.python.org/cpython/rev/d06bf822585c

New changeset 382b3d19e9fc by Serhiy Storchaka in branch '3.6':
Issue bpo-28549: Fixed segfault in curses's addch() with ncurses6.
https://hg.python.org/cpython/rev/382b3d19e9fc

New changeset 11cb97de3edd by Serhiy Storchaka in branch 'default':
Issue bpo-28549: Fixed segfault in curses's addch() with ncurses6.
https://hg.python.org/cpython/rev/11cb97de3edd

[serhiy-storchaka]

Thank you for testing this.