How does g++ implement error handling?

[Euler Herbert]

Hi everyone, 

I am trying to find out how g++ implements error handling. 
My environment is CPU AMD Athlon(tm) XP 2000+, Debian GNU/Linux 
3.1, GCC 3.4.3-6, and Glibc 2.3.2.ds1-20. After researching 
assembling codes generated by g++, I have known the beginning 
and ending part. That is, we will call __cxa_allocate_exception 
when writing 'throw expression', then the constructor of the 
exception class, and then __cxa_throw. __cxa_throw calls 
_Unwind_RaiseException. But this function is so complex for 
me that I cannot get the outline of the real process. However, 
I found uw_install_context (which is a macro) will be called 
if _Unwind_RaiseException succeeds, and the body of 
uw_install_context contains calling of longjmp. So setjmp will 
be somewhere, but I did no find it. Could somebody tell me the 
outline of the unwinding process? 

Thanks in advance. 

Regard, 
Guanpeng Xu

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