platform.libc_ver() fails on Cygwin

[quiver]

BPO	928297
Nosy	@malemburg

^{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/malemburg'
closed_at = <Date 2007-01-13.19:29:39.000>
created_at = <Date 2004-04-02.14:55:32.000>
labels = ['library']
title = 'platform.libc_ver() fails on Cygwin'
updated_at = <Date 2007-01-13.19:29:39.000>
user = 'https://bugs.python.org/quiver'

bugs.python.org fields:

activity = <Date 2007-01-13.19:29:39.000>
actor = 'lemburg'
assignee = 'lemburg'
closed = True
closed_date = None
closer = None
components = ['Library (Lib)']
creation = <Date 2004-04-02.14:55:32.000>
creator = 'quiver'
dependencies = []
files = []
hgrepos = []
issue_num = 928297
keywords = []
message_count = 6.0
messages = ['20413', '20414', '20415', '20416', '20417', '20418']
nosy_count = 2.0
nosy_names = ['lemburg', 'quiver']
pr_nums = []
priority = 'normal'
resolution = 'wont fix'
stage = None
status = 'closed'
superseder = None
type = None
url = 'https://bugs.python.org/issue928297'
versions = ['Python 2.4']

[quiver]

>>> import platform
>>> platform.libc_ver()
Traceback (most recent call last):
  File "<stdin>", line 1, in ?
  File "/usr/lib/python2.3/platform.py", line 134, in libc_ver
    f = open(executable,'rb')
IOError: [Errno 2] No such file or 
directory: '/usr/bin/python'

The problem is that on Cygwin sys.executable
returns /path/to/python, but since Cygwin is running on
Windows, sys.executable is a symbolic link
to /path/to/python.exe.

>>> import os, sys
>>> os.path.exists(sys.executable)
True
>>> os.path.isfile(sys.executable)
True
>>> file(sys.executable)
Traceback (most recent call last):
  File "<stdin>", line 1, in ?
IOError: [Errno 2] No such file or 
directory: '/usr/bin/python'
>>> os.path.islink(sys.executable)
True
>>> os.path.realpath(sys.executable)
'/usr/bin/python2.3.exe'
>>> file(sys.executable + '.exe')
<open file '/usr/bin/python.exe', mode 'r' at 0xa100ca0>

Following is the info about the machine I tested:

>>> from platform import *
>>> platform()
'CYGWIN_NT-5.0-1.5.7-0.109-3-2-i686-32bit'
>>> python_compiler()
'GCC 3.3.1 (cygming special)'
>>> python_build()
(1, 'Dec 30 2003 08:29:25')
>>> python_version()
'2.3.3'
>>> uname()
('CYGWIN_NT-5.0', 'my_user_name', '1.5.7
(0.109/3/2)', '2004-01-30 19:32', 'i686', '')

[malemburg]

Logged In: YES
user_id=38388

Patches are welcome :-)

I don't have cygwin installed, so there's nothing much
I can do about this.

[quiver]

Logged In: YES
user_id=671362

First, I need to correct my previous post. 'symbolic' was
unrelated.
Python on Cygwin does't like exe files that doesn't end
with '.exe'.
I think changing fileobject.c to support I/O exe files on
Cygwin whether it ends with '.exe' or not is the way to go.

Is there anyone who can do that? It's beyoond my skill level.

$ ls -l /usr/bin/python*
lrwxrwxrwx  1 abel  Users    24 Jan  1 01:34 /usr/bin/python -
> python2.3.exe
lrwxrwxrwx  1 abel  Users    24 Jan  1 
01:34 /usr/bin/python.exe -> python2.3.exe
-rwxrwxrwx  1 abel  Users  4608 Dec 30 
22:32 /usr/bin/python2.3.exe

>>> file('/usr/bin/python')
Traceback (most recent call last):
  File "<stdin>", line 1, in ?
IOError: [Errno 2] No such file or directory: '/usr/bin/python'
>>> file('/usr/bin/python.exe')
<open file '/usr/bin/python.exe', mode 'r' at 0xa069320>
>>> file('/usr/bin/python2.3')
Traceback (most recent call last):
  File "<stdin>", line 1, in ?
IOError: [Errno 2] No such file or 
directory: '/usr/bin/python2.3'
>>> file('/usr/bin/python2.3.exe')
<open file '/usr/bin/python2.3.exe', mode 'r' at 0xa0c8de0>

[malemburg]

Logged In: YES
user_id=38388

Would applying os.path.realpath() to sys.executable before
trying to open that file fix the problem on Cygwin ?

Another question: does using libc_ver() even make sense on
cygwin ?

libc_ver() was never intended to be used on non-*nix
platforms. I don't even know whether it works on other
platforms than Linux.

[quiver]

Logged In: YES
user_id=671362

Sorry for my late response, Marc.

Would applying os.path.realpath() to sys.executable before
trying to open that file fix the problem on Cygwin ?

That change fixes the IO problem. After this, it doesn't raise
IOError. The result of platform.libc_ver() is as follows:

>>> import platform
>>> platform.libc_ver()
('', '')

Another question: does using libc_ver() even make sense on
cygwin ?

As far as I have checked, it doesn't look like so. According to
the Cygwin FAQ[*], Cygwin doesn't use glibc, although it
says that there's a counterpart(called ``newlib'') in Cygwin. C
runtime embedded into cygwin1.dll uses newlib.

Experienced C & Cygwin programmers might anser this
question more precisely.

[*] Where is glibc? :
http://rustam.uwp.edu/support/faq.html#SEC88

[malemburg]

Since Cygwin doesn't appear to use the GLibC, there's no surprise in libc_ver() not returning any useful information.