New submission from Jason Howlett :
This error is observed in Python 2.7.2.
Steps to recreate problem:
1) Create directory ~/pytest.
2) Untar Python 2.7.2 sources into ~/pytest
3) configure, build, and install with --prefix=~/pytest/pyinstall
4) mkdir -p ~/pytest/other/bin
5) cd ~/pytest/other/bin
6) ln -s ../../pyinstall/bin/python
7) cd ~/pytest
8) ln -s other/bin bin
9) bin/python
This will result in the following exception:
Traceback (most recent call last):
File "/home/jason/pytest/bin/../../pyinstall/lib/python2.7/site.py", line
564, in
main()
File "/home/jason/pytest/bin/../../pyinstall/lib/python2.7/site.py", line
546, in main
known_paths = addusersitepackages(known_paths)
File "/home/jason/pytest/bin/../../pyinstall/lib/python2.7/site.py", line
279, in addusersitepackages
user_site = getusersitepackages()
File "/home/jason/pytest/bin/../../pyinstall/lib/python2.7/site.py", line
254, in getusersitepackages
user_base = getuserbase() # this will also set USER_BASE
File "/home/jason/pytest/bin/../../pyinstall/lib/python2.7/site.py", line
243, in getuserbase
from sysconfig import get_config_var
ImportError: No module named sysconfig
Placing 'print sys.path' on line 242 of site.py prints out something like this:
['/home/jason/pyinstall/lib/python27.zip',
'/home/jason/pyinstall/lib/python2.7',
'/home/jason/pyinstall/lib/python2.7/plat-linux2',
'/home/jason/pyinstall/lib/python2.7/lib-tk',
'/home/jason/pyinstall/lib/python2.7/lib-old',
'/home/jason/pyinstall/lib/python2.7/lib-dynload']
Notice that the root directory is /home/jason/pyinstall instead of the correct
value /home/jason/pytest/pyinstall.
Now, on line 65 of site.py, add import sysconfig. For some reason this works at
this point in site.py, but not down on line 243.
In sysconfig.py, at line 94, add the following:
print 'SYSCONFIG:', sys.exec_prefix, _EXEC_PREFIX
This will print the following:
SYSCONFIG: /home/jason/pytest/bin/../../pyinstall /home/jason/pyinstall
Line 93 of sysconfig.py is a call to normpath that collapses the path. The root
of this problem is that the value of sys.exec_prefix is not correct. The value
it has will work fine if ls'ing it in a shell as it handles the symlink
/home/jason/pytest/bin properly. Path calculations internal to python, however,
do not end up with the correct results.
I believe the fix to this problem is to modify Modules/getpath.c, starting at
line 488, and instead of looking only for a symlink in the python executable,
also look for a link in any of the path elements leading up to the executable.
Detecting and expanding these out should result, in this example, with
sys.exec_prefix being /home/jason/pytest/pyinstall and the correct behavior in
sysconfig, site, etc.
--
components: Interpreter Core
messages: 145582
nosy: Jason.Howlett
priority: normal
severity: normal
status: open
title: Multi-layered symlinks cause runtime error. sys.path is malformed.
type: crash
versions: Python 2.7
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<http://bugs.python.org/issue13184>
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