Lack of pw_gecos field in Android's struct passwd causes cross-compilation for the pwd module to fail

[shiz]

BPO	20306
Nosy	@pitrou, @skrah, @freakboy3742, @xdegaye
Files	Python-3.4.0tip-workaround-android-missing-pw_gecos-field.patch: A patch that works around the lack of a pw_gecos field by setting the relevant value to None. pw_gecos-field-workaround-with-config_ac-mods.patch: shiz's patch extended with the required addition to configure.ac pw_gecos-field-workaround-with-config_ac-mods.patch: patch without mods to generated files (just mods pwdmodule.c and configure.ac)

^{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/skrah'
closed_at = <Date 2016-04-26.00:04:14.754>
created_at = <Date 2014-01-19.18:23:41.849>
labels = ['build']
title = "Lack of pw_gecos field in Android's struct passwd causes cross-compilation for the pwd module to fail"
updated_at = <Date 2016-04-26.09:50:06.970>
user = 'https://bugs.python.org/shiz'

bugs.python.org fields:

activity = <Date 2016-04-26.09:50:06.970>
actor = 'skrah'
assignee = 'skrah'
closed = True
closed_date = <Date 2016-04-26.00:04:14.754>
closer = 'skrah'
components = ['Build']
creation = <Date 2014-01-19.18:23:41.849>
creator = 'shiz'
dependencies = []
files = ['33550', '37009', '37930']
hgrepos = []
issue_num = 20306
keywords = ['patch']
message_count = 9.0
messages = ['208487', '217356', '217368', '229964', '235061', '264201', '264229', '264243', '264244']
nosy_count = 7.0
nosy_names = ['pitrou', 'skrah', 'freakboy3742', 'xdegaye', 'python-dev', 'shiz', 'WanderingLogic']
pr_nums = []
priority = 'normal'
resolution = 'fixed'
stage = 'resolved'
status = 'closed'
superseder = None
type = 'compile error'
url = 'https://bugs.python.org/issue20306'
versions = ['Python 3.6']

[shiz]

As the title states, mkpwent() in pwdmodule.c accesses pw_gecos, which is not defined for struct passwd in Bionic, Android's C library.

Attached is a patch that works around the issue by setting the field to None on Android.

[pitrou]

Interesting. It seems pw_gecos isn't mandated by POSIX:
http://pubs.opengroup.org/onlinepubs/9699919799/basedefs/pwd.h.html

I wonder if there's a better way to do this (autoconf check?) than an Android-specific #ifdef, though.

[shiz]

Ah, yes, if it's not actually mandated by POSIX, something like HAVE_PASSWD_PW_GECOS would be more appropriate. I'll rework the patch into something more generic.

[WanderingLogic]

Here is shiz's patch extended with the addition to configure.ac. I added the variable HAVE_PASSWD_GECOS_FIELD and the appropriate tests. Luckily this very problem (missing pw_gecos field) is the example used in the autoconf manual (https://www.gnu.org/software/autoconf/manual/autoconf-2.69/html_node/Generic-Structures.html#Generic-Structures). (Otherwise I would have been as lost as I usually am with autoconf.)

[WanderingLogic]

Apologies. That last patch includes diffs to generated files (configure and pyconfig.h.in). This version just patches Modules/pwdmodule.c and configure.ac.

After applying the patch please run "autoheader" and "autoconf" to correctly regenerate configure and pyconfig.h.in.

[python-dev]

New changeset 0d74d4937ab9 by Stefan Krah in branch 'default':
Issue bpo-20306: The pw_gecos and pw_passwd fields are not required by POSIX.
https://hg.python.org/cpython/rev/0d74d4937ab9

[xdegaye]

With changeset 0d74d4937ab9, test_pwd fails on android API level 21 at test_values with:
  Traceback (most recent call last):
    File "/sdcard/org.bitbucket.pyona/lib/python3.6/test/test_pwd.py", line 27, in test_values
      self.assertIsInstance(e.pw_passwd, str)
  AssertionError: None is not an instance of <class 'str'>

On android API 21 HAVE_STRUCT_PASSWD_PW_PASSWD is defined but p->pw_passwd is set to NULL.

[python-dev]

New changeset f0f519aca558 by Stefan Krah in branch 'default':
Issue bpo-20306: Android is the only system that returns NULL for the pw_passwd
https://hg.python.org/cpython/rev/f0f519aca558

[skrah]

Okay, for the record: I think that returning "None" would probably be
more correct than the empty string, but I don't think users actually
care to the point that they will introduce a case split in their
applications.

Realistically, probably no one cares about pw_passwd at all.