UnboundLocalError in cgitb.py

[jemfinch]

BPO	861340
Nosy	@smontanaro
Files	lookup.py

^{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/smontanaro'
closed_at = <Date 2005-05-20.03:26:45.000>
created_at = <Date 2003-12-16.23:09:19.000>
labels = ['library']
title = 'UnboundLocalError in cgitb.py'
updated_at = <Date 2005-05-20.03:26:45.000>
user = 'https://bugs.python.org/jemfinch'

bugs.python.org fields:

activity = <Date 2005-05-20.03:26:45.000>
actor = 'skip.montanaro'
assignee = 'skip.montanaro'
closed = True
closed_date = None
closer = None
components = ['Library (Lib)']
creation = <Date 2003-12-16.23:09:19.000>
creator = 'jemfinch'
dependencies = []
files = ['1142']
hgrepos = []
issue_num = 861340
keywords = []
message_count = 8.0
messages = ['19427', '19428', '19429', '19430', '19431', '19432', '19433', '19434']
nosy_count = 3.0
nosy_names = ['skip.montanaro', 'nnorwitz', 'jemfinch']
pr_nums = []
priority = 'normal'
resolution = 'out of date'
stage = None
status = 'closed'
superseder = None
type = None
url = 'https://bugs.python.org/issue861340'
versions = ['Python 2.3']

[jemfinch]

Here's the exception:

Exception
return cgitb.text((E, e, tb)).rstrip('\r\n')
File "/usr/lib/python2.3/cgitb.py", line 197, in text
vars = scanvars(reader, frame, locals)
File "/usr/lib/python2.3/cgitb.py", line 76, in scanvars
parent = value
UnboundLocalError: local variable 'value' referenced
before assignment

And here's the code:

        if lasttoken == '.': 
            if parent is not \_\_UNDEF__: 
                value = getattr(parent, token, \_\_UNDEF__) 
                vars.append((prefix + token, prefix, value)) 
        else: 
            where, value = lookup(token, frame, locals) 
            vars.append((token, where, value)) 
    elif token == '.': 
        prefix += lasttoken + '.' 
        parent = value 

If lasttoken is '.' and parent is __UNDEF__, value doesn't
get set. I'd offer a patch, but I really have no idea what this
code is doing and so don't know what to set value to.

[nnorwitz]

Logged In: YES
user_id=33168

Jeremy, can you attach a complete test case?

Skip, I realize you didn't write the scanvars code (Ping
did), but you did add text. So maybe you have an idea.
From a brief scan, it looks like if value is initialized to
None, the code might work.

[smontanaro]

Logged In: YES
user_id=44345

Sorry, I have no idea what it does either. I'll look into it a bit,
but don't expect a miracle. :-(

[smontanaro]

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I pulled scanvars() and lookup() out into a separate file and
instrumented things a little. From staring at the code I thought
that perhaps it didn't handle the case where the line starts with
a dot separating an object and its attribute. I can't provoke a
failure in that situation though. See attached lookup.py.

Jeremy, can you fiddle it to make it fail?

[jemfinch]

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user_id=99508

To be honest, it's just something I ran into in my own test suite
when my exception-handling logging code caught an exception I
didn't expect to get raised. Since I have no idea what the code in
cgitb that's raising the exception is actually doing, I really don't
know how to begin to try and narrow it down to a test case.

[jemfinch]

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The code that caused the raised exception (which subsequently
triggered the exception in cgitb) was this:

    outputstr = '%d %s match \\'%s\\' (%s):' % (len(bugs), \\ 
    utils.pluralize(len(bugs), 'bug'), 
    searchstr, utils.commaAndify(keywords, And='AND')) 

That's actually from the diff where I changed it to be a bit more
idiomatic :) It wasn't my code, I promise!

[nnorwitz]

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user_id=33168

Jeremy, that's still not enough to reproduce the bug. What
exception was thrown by the code below and from where? What
were the values of bugs, searchstr, and keywords? What are
the definitions for utils.pluralize() and utils.commaAndify()?

[smontanaro]

Logged In: YES
user_id=44345

Looks like this was fixed at some point. The local variable value is
clearly initialized in scanvars() at this point.