> A few comments to explain this highly stylized and macro-laden code
> would be appreciated.
I probably can't do that before 2.1a1, but I promise to suggest
something right afterwards.
In general, the macro magic is designed to make the many expat
callbacks available to Python. RC_HANDLER (for return code) is the
most general template; VOID_HANDLER and INT_HANDLER are common
specializations. In the core of RC_HANDLER, there a tuple is built and
a Python function is called.
The code used to do PyEval_CallObject right inside the macro; the
call_with_frame feature is new compared to 2.0. It solves the specific
problem of incomprehensible tracebacks.
In a typical SAX application, the user code calls
expatreader.ExpatParser.parse, which in turn calls
self._parser.Parse(data, isFinal)
Now, in 2.0, a common problem was a traceback
self._parser.Parse(data, isFinal)
TypeError: not enough arguments; expected 4, got 2
Everybody assumes a problem in the call to Parse; the real problem is
in the call to the callback inside RC_HANDLER, which tried to call a
user's function with two arguments that expected four.
2.1 would improve this slightly on its own, writing
self._parser.Parse(data, isFinal)
TypeError: characters() takes exactly 4 arguments (2 given)
With that code, you get
File "/usr/local/lib/python2.1/xml/sax/expatreader.py", line 81, in feed
self._parser.Parse(data, isFinal)
File "pyexpat.c", line 379, in CharacterData
TypeError: characters() takes exactly 4 arguments (2 given)
So that tells you that it is the CharacterData handler that invokes
characters(). You are right that the frame object is not used
otherwise; it is just there to make a nice traceback.
> I simply don't understand what's going on -- and I'm deeply
> suspicious that it is the source of whatever problems Tim is seeing
> with test_sax.
I thought so, too, at first; it turned out that the problem was
elsewhere.
Regards,
Martin
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