subprocess: surrogates of the error message (Python implementation on non-Windows)

[vstinner]

BPO	8467
Nosy	@vstinner
Files	subprocess_errmsg.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 = None
closed_at = <Date 2010-04-23.20:22:34.391>
created_at = <Date 2010-04-20.12:02:54.306>
labels = ['library', 'expert-unicode']
title = 'subprocess: surrogates of the error message (Python implementation on non-Windows)'
updated_at = <Date 2010-04-23.20:22:34.390>
user = 'https://github.com/vstinner'

bugs.python.org fields:

activity = <Date 2010-04-23.20:22:34.390>
actor = 'vstinner'
assignee = 'none'
closed = True
closed_date = <Date 2010-04-23.20:22:34.391>
closer = 'vstinner'
components = ['Library (Lib)', 'Unicode']
creation = <Date 2010-04-20.12:02:54.306>
creator = 'vstinner'
dependencies = []
files = ['17005']
hgrepos = []
issue_num = 8467
keywords = ['patch']
message_count = 2.0
messages = ['103694', '104045']
nosy_count = 1.0
nosy_names = ['vstinner']
pr_nums = []
priority = 'normal'
resolution = 'fixed'
stage = None
status = 'closed'
superseder = None
type = None
url = 'https://bugs.python.org/issue8467'
versions = ['Python 3.1', 'Python 3.2']

[vstinner]

On a non-Windows OS where _posixsubprocess is missing (subprocess uses the pure Python implementation), if the child fails with a Python exception and the exception message contains a surrogate character, message.encode() fails silently (exception while processing exceptions are just ignored).

Surrogates should be passed to the parent process: surrogatepass can be used for that. Attached patch implements this idea with an unit test.

--

_posixsubprocess is not concerned because it writes an empty message for OSError (the parent process calls os.strerror() to get the message) or "Exception occurred in preexec_fn." (pure ASCII string) for RuntimeError.

On Windows, _subprocess.CreateProcess() calls PyErr_SetFromWindowsErr() on failure without the filename. So there is no surrogates here.

[vstinner]

Commited in py3k (r80413), blocked in 3.1 (r80414).

Python 3.1 uses pickle to encode the traceback and pickle supports surrogates (see bpo-8383).