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I'm posting an edited question since the whole business of segfaults and third-party libraries in the original question are just distracting.

What I have is a program that uses xerces-c and segfaults (creating a core-dump in the process). What I want to do is to fire up gdb and traverse the created DOMDocument from the core-dump.

e.g., I want to get the attributes of a given DOMElement or it's children nodes and so on. Does anyone have any articles I can read up for this that describe the internal structure of DOMElements and so on? Or even point me to some resources on the xerces-c source code since I've been unable to find the source code for DOMElement in my source tarball. (Having the source code might help since then I know exactly how DOMElement is implemented allowing me to traverse it).

As I said, I'm not too familiar with the xerces-c codebase and apache documentation is patently horrible.

Original Question:-

I'm using an third-party library that in turn uses xercesc for xml parsing somewhere which is segfaulting. How do I inspect xerces-c elements from the core-dump?

I have access to the library source code and it's segfaulting in a function that uses a DOMElement reference as a function argument. Something like 

void func (DOMElement& e, ...) {
}

I want to inspect this DOMElement from the core-dump (as in print out it's name, tags, children elements and so on. basically traverse the DOMDocument below this DOMElement) but I'm not familiar with the xerces-c codebase.

Any idea of how I can go about doing this?

Additional info :- I'm using gdb.

owagh
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1 Answers1

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If you are using gdb I assume you are using linux, right? Then you should install libexerces-c++-dev (or libexerces-c++-devel depending on your distribution) packet AND the source code. This would allow you to even set breakpoints in the xerces code.

I've been using xerces a lot in the past and when it crashes generally the problem is not in the library itself but in the "caller". In your case I'd create a very trivial project using the external library, and try to parse a simple known-to-work XML file, because even if you can find the crash instructions I doubt it would help, given that xerces is used not directly by you but by another library

Emiliano
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  • I've compiled xerces-c from source since I was lead to believe that the libxerces-c++-dev packages do not contain the full debugging symbol info. Anyways, I'm pretty sure the problem is not in xerces-c but in the library so I just want to check that the library is creating and passing around the "correct" DOMElement nodes. Running DOMPrint on the XML file works perfectly fine so the issue isn't there. Writing a small test exec also works fine. The segfault is definitely in the external library so it's not xercesc that I'm worried about. – owagh May 10 '12 at 17:15
  • Have you tried writing a small test exec which uses the external library? That was what I meant in my answer: the small test was meant for the external library, not for `xerces`. I'll update my answer to remove ambiguity – Emiliano May 11 '12 at 14:23
  • I had figured that you meant that... And yes the small test exec seems to work fine. I haven't been able to recreate it in a minimal executable. Anyways, I fixed the segfaults but my question is still unanswered. How do we traverse a xerces-c DOMDocument while in the debugger. I'll update the question to make it a bit more general since the whole business of the third-party library and segfaults is just distracting from the main point of the question. – owagh May 11 '12 at 18:38