[Python-bugs-list] [ python-Bugs-445928 ] UnboundLocalError in httplib.py

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Bugs item #445928, was opened at 2001-07-30 05:35
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Category: Python Library
Group: Python 2.2
Status: Open
Resolution: None
Priority: 5
Submitted By: Just van Rossum (jvr)
Assigned to: Martin v. Löwis (loewis)
Summary: UnboundLocalError in httplib.py

Initial Comment:
Python 2.2a0 (#1, 07/30/01, 13:21:09) 
[GCC Apple DevKit-based CPP 6.0alpha] on darwin1
Type "help", "copyright", "credits" or "license" for 
more information.
>>> import urllib
>>> f = urllib.urlopen("http://www.letterror.com/")
Traceback (most recent call last):
  File "<stdin>", line 1, in ?
  File "/usr/local/lib/python2.2/urllib.py", line 71, in 
urlopen
    return _urlopener.open(url)
  File "/usr/local/lib/python2.2/urllib.py", line 176, 
in open
    return getattr(self, name)(url)
  File "/usr/local/lib/python2.2/urllib.py", line 283, 
in open_http
    h.putrequest('GET', selector)
  File "/usr/local/lib/python2.2/httplib.py", line 449, 
in putrequest
    self.send(str)
  File "/usr/local/lib/python2.2/httplib.py", line 391, 
in send
    self.connect()
  File "/usr/local/lib/python2.2/httplib.py", line 375, 
in connect
    raise socket.error, msg
UnboundLocalError: local variable 'msg' referenced 
before assignment
>>>


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>Comment By: Guido van Rossum (gvanrossum)
Date: 2001-07-30 19:00

Message:
Logged In: YES 
user_id=6380

IMO it's still ugly to have code that relies on a variable
set in an except clause in a for loop. Any decent
compile-time checker would flag this as a potential error.
No matter how getaddrinfo() is fixed, I think httplib.py
should be made more robust as well.


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Comment By: Martin v. Löwis (loewis)
Date: 2001-07-30 15:40

Message:
Logged In: YES 
user_id=21627

I believe getaddrinfo must never return an empty list. If 
lookup fails, it shall raise an exception. From the 
Solaris manpage
<man>
For getaddrinfo(), if the query is successful, a pointer to
a  linked  list  of  one  or  more addrinfo structures
is returned by the fourth argument and the function
returns 0. If the query fails, a non-zero error code will
be returned.
</man>

So returning a 0 result and an empty list is an 
implementation bug in getaddrinfo (or an incorrect call to 
it). If we want to protect us against buggy 
implementations, we should do BadInternalCall or similar 
in the C code, instead of dealing with the impossible case 
in Python.


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Comment By: Guido van Rossum (gvanrossum)
Date: 2001-07-30 10:39

Message:
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But even if getaddrinfo() returns an empty list, this error
should not occur.  You may have to initialize msg to
something and do something differently at the end when msg
is still None.

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Comment By: Martin v. Löwis (loewis)
Date: 2001-07-30 08:42

Message:
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user_id=21627

It appears that Darwin does provide getaddrinfo. I'm not
sure why it doesn't work.

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Comment By: Just van Rossum (jvr)
Date: 2001-07-30 07:43

Message:
Logged In: YES 
user_id=92689

socketmodule.c: 1.157
getaddrinfo.c: 1.6

socket.getaddrinfo('www.letterror.com',80,0,socket.SOCK_STREA
M) indeed returns an empty list.

I can try to give you access, but I'll have to fiddle with
permissions.


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Comment By: Martin v. Löwis (loewis)
Date: 2001-07-30 07:16

Message:
Logged In: YES 
user_id=21627

Can you please indicate what version of socketmodule.c and
getaddrinfo.c was used for this build?

Please report the result of
import socket
socket.getaddrinfo('www.letterror.com',80,0,socket.SOCK_STREAM)

It should be something like
[(2, 2, 0, '', ('216.218.226.21', 80))]

If it is an empty list (as it appears from the error
message), can you please try step through 
PySocket_getaddrinfo with a debugger and analyse why it
doesn't find out the IP address? If not, is there a chance
to get access to such a machine to debug it myself remotely?


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