Bugs item #1289136, was opened at 2005-09-12 14:04
Message generated for change (Comment added) made by jlt63
You can respond by visiting:
https://sourceforge.net/tracker/?func=detail&atid=105470&aid=1289136&group_id=5470
Please note that this message will contain a full copy of the comment thread,
including the initial issue submission, for this request,
not just the latest update.
Category: Distutils
Group: None
Status: Open
Resolution: None
Priority: 5
Submitted By: John Whitley (jwhitley)
Assigned to: Nobody/Anonymous (nobody)
Summary: distutils extension library path bug on cygwin
Initial Comment:
A while back I reported a problem on the Cygwin mailing
list where all python extension packages would fail
"python setup.py install" at the link step due to a
mangled lib dir (-L) option. distutils was producing a
link line with "-L.", instead of the desired
"-L/usr/lib/python2.4/config". I've finally rooted out
the cause of this problem.
The relevant code is the if-block starting at line 188 of:
/usr/lib/python2.4/distutils/command/build_ext.py
I've reproduced that block here for clarity of
discussion (indentation truncated for redability)
if sys.platform[:6] == 'cygwin' or sys.platform[:6]
== 'atheos':
if string.find(sys.executable, sys.exec_prefix)
!= -1:
# building third party extensions
self.library_dirs.append(os.path.join(sys.prefix, "lib",
"python" +
get_python_version(),
"config"))
else:
# building python standard extensions
self.library_dirs.append('.')
The test "string.find(...) != -1" attempts to test
whether "/usr" appears in the full executable name.
This incorrectly fails in the case that /bin is in the
user's path before /usr/bin. (i.e.
string.find("/bin/python","/usr") == -1) Note that a
vagary of Cygwin is that /usr/bin is a Cygwin mount to
/bin.
The user-side workaround is to ensure that /usr/bin
appears in your path before /bin. It looks like a new
and improved Cygwin special case test is needed to fix
this problem; I'm not sure offhand what the best case
would be. Perhaps an outright test as follows would work:
sys.executable.startswith(sys.exec_prefix) or
sys.executable.startswith(os.sep+"bin")
----------------------------------------------------------------------
>Comment By: Jason Tishler (jlt63)
Date: 2005-11-01 04:16
Message:
Logged In: YES
user_id=86216
I agree with John -- distutils needs to know whether it is
building Python itself or just a extension module. I can
think of the following ways to this accomplish this:
1. Check sys.path
2. Use some of the checks in Modules/getpath.c
Any thoughts about which approach would be better?
Any other ideas?
----------------------------------------------------------------------
Comment By: John Whitley (jwhitley)
Date: 2005-10-28 09:29
Message:
Logged In: YES
user_id=649097
Jason is correct that readlink won't help. On Cygwin
installations,
/bin and /usr/bin are not symlinks, they're aliases in
Cygwin's default mount system. (C:\cygwin on / (root) and
C:\cygwin\bin on /usr/bin) The Python 2.4.1 docs says:
"readlink(path) Return a string representing the path to
which the symbolic link points." For good measure, I
confirmed that readlink doesn't give the desired results.
The bigger problem that I see is that this code is using
hard-coded automagic path detection to figure out something
that it should be told explicitly. That is, "are we in the
special case of building python's own libraries/extensions."
(versus trying to install an extension to an existing
python installation.)
To illustrate the problem, both my proposal and the original
code are broken for trying to build python in /usr/local.
(e.g. build under /usr/local/src -- thinks it's an install
not a build due to "/usr" prefix...)
----------------------------------------------------------------------
Comment By: Jason Tishler (jlt63)
Date: 2005-10-28 04:21
Message:
Logged In: YES
user_id=86216
Unfortunately, I don't think readlink will help.
I was thinking of comparing inodes, but AFAICT inodes
under Cygwin are not guaranteed to be unique for all
platforms and filesystems.
So, maybe John's check is the only reliable option?
----------------------------------------------------------------------
Comment By: Neal Norwitz (nnorwitz)
Date: 2005-10-23 18:47
Message:
Logged In: YES
user_id=33168
What does os.readlink(sys.executable) return?
Maybe that will help you find the true canonical name?
----------------------------------------------------------------------
Comment By: Jason Tishler (jlt63)
Date: 2005-09-16 04:04
Message:
Logged In: YES
user_id=86216
John,
Thanks for the excellent analysis!
All,
Unfortunately, I'm not sure what is the best way to solve this
problem. Does anyone have any suggestions? Thanks.
----------------------------------------------------------------------
You can respond by visiting:
https://sourceforge.net/tracker/?func=detail&atid=105470&aid=1289136&group_id=5470
_______________________________________________
Python-bugs-list mailing list
Unsubscribe:
http://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com
