[Zope-dev] What does error code 136 mean?

[Peter Keller]

Hi,

I have tried Leonardo's very helpful suggestion to get a Python traceback:

> Try to run zope under a debugger. Follow instructions here:
> http://www.zope.org/Members/4am/debugspinningzope

> but type "continue" (w/out quotes) as soon as you get the gdb prompt to
> get zope to run normally.

This, combined with some debugging of the corefile at the C level (which I
know a lot more about than anything to do with Python) has helped me
figure out what the problem is.

The DTML that was cauisng the crash was:

   <dtml-in Catalog sort=lastEditTime reverse>

but some items in Catalog did not have a property lastEditTime. In my
particular circumstances I can exclude these objects from the ZCatalog,
but surely there ought to be a cleaner way of handling this - either
putting objects with missing properties at the end of the list, or not
having them feature in the list at all? Perhaps some way of controlling
this (or at least raising a more meaningful error) might be considered in
a future release of Zope?

The gory details.... I've appended the Python traceback. You can see the
problem call to sort in lib/python/DocumentTemplate/DT_In.py .

Why a SIGFPE? Dates seem to get converted to C doubles by Python for
comparison. From debugging the core file, line 345 in
Objects/floatobject.c in the python v2.1.3 source is causing the problem:

    340 static int
    341 float_compare(PyFloatObject *v, PyFloatObject *w)
    342 {
    343         double i = v->ob_fval;
    344         double j = w->ob_fval;
>   345         return (i < j) ? -1 : (i > j) ? 1 : 0;
    346 }
    347

w is a missing python object with a junk w->ob_fval, which presumably
comes from the missing lastEditTime property of one of the objects
involved in the comparison:

(ladebug) p *w.ob_type
struct _typeobject {

  ...snip...

  tp_name = 0x3fffffa0648="Missing";

  ...snip...

  tp_doc = 0x3fffffa04d0[Ladebug Warning: String is too long to display.
Only the first 128 characters are shown.]="Represent totally unknown
quantities\n\nMissing values are used to represent numberic quantities
that are\nunknown.  They support a";

  ...snip...

}

The Python traceback:

  File "/ebi/msdlocal0/servers/Zope-2.5.1-src/ZServer/PubCore/ZServerPublisher.py", line 23, in __init__
    response=response)
  File "/ebi/msdlocal0/servers/Zope-2.5.1-src/lib/python/ZPublisher/Publish.py", line 150, in publish_module
    response = publish(request, module_name, after_list, debug=debug)
  File "/ebi/msdlocal0/servers/Zope-2.5.1-src/lib/python/ZPublisher/Publish.py", line 98, in publish
    request, bind=1)
  File "/ebi/msdlocal0/servers/Zope-2.5.1-src/lib/python/ZPublisher/mapply.py", line 88, in mapply
    if debug is not None: return debug(object,args,context)
  File "/ebi/msdlocal0/servers/Zope-2.5.1-src/lib/python/ZPublisher/Publish.py", line 39, in call_object
    result=apply(object,args) # Type s<cr> to step into published object.
  File "/ebi/msdlocal0/servers/Zope-2.5.1-src/lib/python/Products/ZWiki/ZWikiPage.py", line 151, in __call__
    body = apply(self._render,(client,REQUEST,RESPONSE),kw)
  File "/ebi/msdlocal0/servers/Zope-2.5.1-src/lib/python/Products/ZWiki/ZWikiPage.py", line 163, in _render
    return apply(method,(self, REQUEST, RESPONSE), kw)
  File "/ebi/msdlocal0/servers/Zope-2.5.1-src/lib/python/Products/ZWiki/ZWikiPage.py", line 553, in render_prelinkdtmlhtml
    t = apply(DTMLDocument.__call__,(self, client, REQUEST, RESPONSE), kw)
  File "/ebi/msdlocal0/servers/Zope-2.5.1-src/lib/python/OFS/DTMLDocument.py", line 127, in __call__
    r=apply(HTML.__call__, (self, (client, bself), REQUEST), kw)
  File "/ebi/msdlocal0/servers/Zope-2.5.1-src/lib/python/DocumentTemplate/DT_String.py", line 473, in __call__
    try: result = render_blocks(self._v_blocks, md)
  File "/ebi/msdlocal0/servers/Zope-2.5.1-src/lib/python/DocumentTemplate/DT_Try.py", line 140, in render
    return self.render_try_except(md)
  File "/ebi/msdlocal0/servers/Zope-2.5.1-src/lib/python/DocumentTemplate/DT_Try.py", line 149, in render_try_except
    result = render_blocks(self.section, md)
  File "/ebi/msdlocal0/servers/Zope-2.5.1-src/lib/python/DocumentTemplate/DT_In.py", line 639, in renderwob
    sequence=self.sort_sequence(sequence, md)
  File "/ebi/msdlocal0/servers/Zope-2.5.1-src/lib/python/DocumentTemplate/DT_In.py", line 775, in sort_sequence
    s.sort()
  File "/ebi/msdlocal0/servers/Zope-2.5.1-src/lib/python/DateTime/DateTime.py", line 1205, in equalTo
    return (self._t == t)
  File "<string>", line 1, in ?

Regards,
Peter.

-- 
========================================================================
Peter Keller.                     | "Research without indebtedness is
European Bioinformatics Institute,|  suspect, and somebody must always,
Hinxton Hall,                     |  somehow, be thanked."
Cambridge, CB10 1SD, UK           |                     --- Umberto Eco
-----------------------------------
Email: keller@ebi.ac.uk |
Tel. (+44/0)1223 494637 | Macromolecular Structure Database
Fax. (+44/0)1223 494468 | http://msd.ebi.ac.uk
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