Unclear warning for subprocess.call

[azumanga]

BPO	7177
Nosy	@birkenfeld, @pjenvey

^{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/pjenvey'
closed_at = <Date 2009-12-03.02:42:48.590>
created_at = <Date 2009-10-20.20:20:03.106>
labels = ['docs']
title = 'Unclear warning for subprocess.call'
updated_at = <Date 2009-12-03.02:42:48.589>
user = 'https://bugs.python.org/azumanga'

bugs.python.org fields:

activity = <Date 2009-12-03.02:42:48.589>
actor = 'pjenvey'
assignee = 'pjenvey'
closed = True
closed_date = <Date 2009-12-03.02:42:48.590>
closer = 'pjenvey'
components = ['Documentation']
creation = <Date 2009-10-20.20:20:03.106>
creator = 'azumanga'
dependencies = []
files = []
hgrepos = []
issue_num = 7177
keywords = []
message_count = 3.0
messages = ['94297', '94314', '95922']
nosy_count = 3.0
nosy_names = ['georg.brandl', 'pjenvey', 'azumanga']
pr_nums = []
priority = 'normal'
resolution = 'fixed'
stage = None
status = 'closed'
superseder = None
type = None
url = 'https://bugs.python.org/issue7177'
versions = ['Python 3.1']

[azumanga]

I wandered across subprocess.call as it was mentioned as a replacement for os.system. The
following large warning is attached to it:

Warning Like Popen.wait(), this will deadlock if the child process generates enough output to a
stdout or stderr pipe such that it blocks waiting for the OS pipe buffer to accept more data.

This scared my off completely, and I assumed the function was simply broken, as I assumed
"stdout pipe" just meant that wherever stdout was sent by default.

I now believe this warning only applies if 'stdout=PIPE', or similar, is used explicitally.

Could this warning be better worded, perhaps adding "if stdout or stderr are explicitly
redirected", as in:

Warning Like Popen.wait(), if stdout or stderr are explicitly redirected this will deadlock if
the child process generates enough output to a stdout or stderr pipe such that it blocks
waiting for the OS pipe buffer to accept more data.

[birkenfeld]

Assigning to Philip who added the warning.

[pjenvey]

Improved in r76640 / r76641 to explicitly mention this applies to
stdout/err=PIPE