[Ironpython-users] Differences with pyc-compiled assemblies?

[Jeff Hardy]

On Sun, Nov 11, 2012 at 5:43 PM, Nicholas Devenish <misnomer at gmail.com> wrote:
>>> Traceback (most recent call last):
>>>  File "<stdin>", line 1, in <module>
>>>  File "sqlalchemy\__init__.py", line 52, in <module>
>>>  File "sqlalchemy\types", line 27, in <module>
>>>  File "sqlalchemy\schema", line 2670, in <module>
>>>  File "sqlalchemy\schema", line 2706, in DDLElement
>>>  File "sqlalchemy\util\deprecations", line 45, in decorate
>>>  File "sqlalchemy\util\deprecations", line 116, in _decorate_with_warning
>>>  File "sqlalchemy\util\langhelpers", line 41, in decorate
>>>  File "c:\Program Files\IronPython 2.7\Lib\inspect.py", line 814, in getargspec
>>>  File "c:\Program Files\IronPython 2.7\Lib\inspect.py", line 758, in getargs
>>> IndexError: index out of range: 2
>> In inspect.py, just before line 758, it looks at co.co_argcount and
>> co.co_varnames and assumes that they are the same length, but my guess
>> is that they might not be when compiled with pyc. If you can figure
>> out exactly what getargspec is being called on, that might help make a
>> simpler reproduction that I can work off of.
>
> So, I've traced down the stack trace with some tested output. This is what it seems to be doing:

First off, thank you for the detailed analysis. It's very helpful.

>
>> Starting with the wrapped function (though the line number seems off slightly,
>> everything else in the stack trace and debug output before the exception matches
>> up exactly):
>> ... snip ...
>> That calls getargs:
>>
>>     def getargs(co):
>>         if not iscode(co):
>>             raise TypeError('{!r} is not a code object'.format(co))
>>
>>         nargs = co.co_argcount
>>         names = co.co_varnames
>>         args = list(names[:nargs])
>>         step = 0
>>
>>         for i in range(nargs):
>>             if args[i][:1] in ('', '.'):
>>
>> With values for the variables:
>>
>>     print "getargs:"
>>     print " args:  {}".format(args)
>>     print " nargs: {}".format(nargs)
>>     print " names: {}".format(names)
>>
>> And the output from these print statements:
>>
>>     getargs:
>>      args:  ['target', 'call_event']
>>      nargs: 3
>>      names: ('target', 'call_event')
>

It's odd that nargs (co_argcount) is 3, but names (co_varnames) has
only 2 elements. I'm afraid it might be a bug in how IronPython
compiles the code. It's possible that no one has tried using pyc on
code that accesses the co_* values before.

- Jeff