strftime fails on HP-UX

[michael-o]

BPO	34402
Nosy	@terryjreedy, @michael-o

^{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 = None
created_at = <Date 2018-08-14.12:36:57.811>
labels = ['3.7', 'type-bug', 'library']
title = 'strftime fails on HP-UX'
updated_at = <Date 2018-08-18.18:55:23.430>
user = 'https://github.com/michael-o'

bugs.python.org fields:

activity = <Date 2018-08-18.18:55:23.430>
actor = 'michael-o'
assignee = 'none'
closed = False
closed_date = None
closer = None
components = ['Library (Lib)']
creation = <Date 2018-08-14.12:36:57.811>
creator = 'michael-o'
dependencies = []
files = []
hgrepos = []
issue_num = 34402
keywords = []
message_count = 4.0
messages = ['323512', '323513', '323680', '323728']
nosy_count = 2.0
nosy_names = ['terry.reedy', 'michael-o']
pr_nums = []
priority = 'normal'
resolution = None
stage = None
status = 'open'
superseder = None
type = 'behavior'
url = 'https://bugs.python.org/issue34402'
versions = ['Python 3.7']

[michael-o]

strftime() fails on HP-UX. It is mapped to wcsftime(3). It has a quirk on HP-UX that is does not conform to POSIX. To enable POSIX compat one has to do (excerpt from manpage):

APPLICATION USAGE
The "Unix Standards Only" prototype of wcsftime() is available to
applications if they are:
a. c99 conformant.

       b. Compiled with -D_XOPEN_SOURCE macro with a value \>=500.

       c. Compiled with -D_POSIX_C_SOURCE macro with a value \>= 200112.

  Also the application must be compiled with the environment variable
  UNIX_STD set to the value 98 or above and exported.

b and c are satasfied according to config.log. Let's get to a). The manpage of aCC says:

EXTERNAL INFLUENCES
Environment Variables
[...]
UNIX95 or UNIX_STD specify the XPG4 behavior for c89(1) and c99(1).
-D_XOPEN_UNIX is also set. UNIX_STD must be set to 1995, 1998 or
2003. Both these variables cause an appropriate object file to be
linked into executables in order to customize libc to match ISO/IEC
9899:1990/Amendment 1:1995 (1995) and the C++ and C99 Standards for
the various wide char (1998) or other C99 libc functions (2003).
NOTE: 2003 is only available on HP-UX 11.31.

So one must at least do "export UNIX_STD=1998".

I am quite certain that other parts of Python are affected too.

The safest bet would be actually to test wcsftime at configure time wether the output is fine and have this env var set in the Makefile, unfortunately, this will only work for GNU make. Alternatively, a warning at the very end of the configure run has to be printed to export this env var.

If done, test_strftime and test_teststrptime will pass flawlessly.

[michael-o]

The worst thing about wcsftime(3) is that it silently fails by not writing to output buffer. timemodule.c allocates more and more memory and then gives up.

[terryjreedy]

Same comment as for bpo-34401.

[michael-o]

Thanks changed appropriately. I here also have a PR idea I will try on Monday. It won't be idiotproof, but someone will likely comment on it and provide more input.

I am willing to provide even more patches, but am currently stuck with #8786 and juggle with "git stash" to make Python actually compile on HP-UX. This is cumbersome.