Need help in understanding GDB stack trace

[Michael Snyder]

ying lcs wrote:
> All,
> 
> I need help in understadning Gdb stack trace:
> 
> [Switching to Thread 0xb73b4700 (LWP 28041)]
> 0x00000000 in ?? ()
> (gdb) bt
> #0  0x00000000 in ?? ()
> #1  0xb5bfc9a6 in DefaultSerializeElementRule::serializeStart (this=0xa450e40,
>     domElement=0xa03e104, fd=0xa450ab0)
>     at /media/storage/working/content/serializer/src/DefaultSerializeElementRule.cpp:55
> 
> And here is my method:
> 
> void DefaultSerializeElementRule::serializeStart(nsIDOMElement*
> domElement, FILE* fd) {
> 
>   nsAutoString tagName;
> 
>   domElement->GetTagName(tagName);
> 
>   fprintf(fd, "<%s", NS_ConvertUTF16toUTF8(tagName).get());
>   // this is line 55:
>   serializeAttribute(domElement, fd);
> 
> }
> 
> 
> I don't understand what is the meaning of :
> 0x00000000 in ?? ()
> 
> from the stack trace, both my domElement, fd are not null. So why my
> program crashes?

Try this:

(gdb) frame 1
(gdb) print domElement->GetTagName

See whether the function pointer is actually valid.
Hopefully it should point to a function...