Bugs item #1075984, was opened at 2004-11-30 13:13
Message generated for change (Comment added) made by mwh
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Category: XML
Group: Python 2.4
Status: Open
Resolution: None
Priority: 5
Submitted By: Maik Hertha (mhertha)
>Assigned to: Fred L. Drake, Jr. (fdrake)
Summary: Memory fault pyexpat.so on SGI
Initial Comment:
I build the latest RC1 of python 2.4.
System SGI Fuel IP35, Irix 6.5.26m
cc -version
MIPSpro Compilers: Version 7.3.1.3m
- make tests passes test_pyexpat without error
- running this code leads to a core dump
-- code ---
import xml.dom.minidom
doc = xml.dom.minidom.parseString(fstream)
<<< core dump >>>
--- runing python -v test.py
#
/opt/python24c1/lib/python2.4/xml/dom/expatbuilder.pyc
matches
/opt/python24c1/lib/python2.4/xml/dom/expatbuilder.py
import xml.dom.expatbuilder # precompiled from
/opt/python24c1/lib/python2.4/xml/dom/expatbuilder.pyc
import xml.parsers # directory
/opt/python24c1/lib/python2.4/xml/parsers
#
/opt/python24c1/lib/python2.4/xml/parsers/__init__.pyc
matches
/opt/python24c1/lib/python2.4/xml/parsers/__init__.py
import xml.parsers # precompiled from
/opt/python24c1/lib/python2.4/xml/parsers/__init__.pyc
# /opt/python24c1/lib/python2.4/xml/parsers/expat.pyc
matches /opt/python24c1/lib/python2.4/xml/parsers/expat.py
import xml.parsers.expat # precompiled from
/opt/python24c1/lib/python2.4/xml/parsers/expat.pyc
dlopen("/opt/python24c1/lib/python2.4/lib-dynload/pyexpat.so",
2);
Memory fault(coredump)
- running this code from an interactive session leads
not to a coredump
I need some assistance howto provide further debug
information.
--maik./
----------------------------------------------------------------------
>Comment By: Michael Hudson (mwh)
Date: 2005-02-02 10:35
Message:
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It's a nasty one, I'll give you that.
Fred, what do you think of bos's patch? It solves the immediate issue,
but I'm not sure it's a complete fix.
It seems to me that it would be better to resolve the expat symbols at
builf time, but I don't know how to arrange for that.
----------------------------------------------------------------------
Comment By: Bryan O'Sullivan (bos)
Date: 2005-02-02 06:09
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By the way, this is not an SGI-specific bug. This will bite any Unix system
with a modern sysv-style dynamic linker. The priority of this bug should be
higher, IMO.
----------------------------------------------------------------------
Comment By: Bryan O'Sullivan (bos)
Date: 2005-02-01 07:53
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I've been bitten by the same bug. In my case, the problem was with Qt, not GTK.
It's not actually necessary to check the expat version; just see if
XML_ErrorString actually returns anything.
Here's the patch I use for this problem:
--- python/Modules/pyexpat.c 2005-01-06 16:26:13 -08:00
+++ python/Modules/pyexpat.c 2005-01-31 23:46:36 -08:00
@@ -1936,9 +1936,12 @@
}
#endif
-#define MYCONST(name) - PyModule_AddStringConstant(errors_module, #name, -
(char*)XML_ErrorString(name))
+#define MYCONST(name) + { + char *_v =
(char*)XML_ErrorString(name); + if (_v) +
PyModule_AddStringConstant(errors_module, #name, _v); + }
MYCONST(XML_ERROR_NO_MEMORY);
MYCONST(XML_ERROR_SYNTAX);
----------------------------------------------------------------------
Comment By: Stephen Watson (kerofin)
Date: 2004-12-13 13:46
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pyexpat initializes using its internal copy of expat.
libexpat.so is still mapped in (after pyexpat has
initilized), but gdb finds the python copy of
XML_ErrorString and other functions.
I suspect that this will be a problem if the system version
of expat is newer than Python's.
----------------------------------------------------------------------
Comment By: Michael Hudson (mwh)
Date: 2004-12-13 13:01
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1) Good sleuthing.
2) Argh!
3) What happens if you import pyexpat before pygtk?
----------------------------------------------------------------------
Comment By: Stephen Watson (kerofin)
Date: 2004-12-13 09:29
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I've looked at the program that was dumping core and the
sequence is this:
1) Program imports pygtk, which links in the GTK libraries
2) Program loads SVG image which links in librsvg.so which
in turn links in /usr/local/lib/libexpat.so
3) Program imports pyexpat.
4) pyexpat calls XML_ErrorString, but as ld.so has already
linked in XML_ErrorString from /usr/local/lib/libexpat.so it
calls that version, not the one in pyexpat.so.
5) pyexpat looks up an error defined by the later version of
expat it is expecting and gets a NULL pointer from the
earlier version it has. It attempts to use it without
checking (strlen) and dumps core.
----------------------------------------------------------------------
Comment By: Stephen Watson (kerofin)
Date: 2004-12-10 17:01
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Maybe it compiled against its own copy of expat, but pulled
in the system's copy when run?
----------------------------------------------------------------------
Comment By: Michael Hudson (mwh)
Date: 2004-12-10 16:52
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Uh, Python includes its own copy of expat, and I really
thought we were supposed to prefer our own version over
anything found on the system...
----------------------------------------------------------------------
Comment By: Stephen Watson (kerofin)
Date: 2004-12-10 16:46
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I also got a core dump importing pyexpat on Solaris (SPARC)
and somebody else reported it on a *BSD system.
It appears to be a problem with older versions of expat not
being tested for. I used gdb to trace it down to line 1972
in pyexpat.c where it attempts to define the first constant
from 1.95.8. I had expat 1.95.7. After upgrading to 1.95.8
it worked fine, as did the *BSD system.
I think Python needs to check the expat version, as it does
elsewhere in the file, before defining those constants.
I am still puzzelled over how it managed to compile
pyexpat.c in the first place...
----------------------------------------------------------------------
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