backtrace and demangling symbols at runtime

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Hi..
I'm using __cxxabiv1::__cxa_demangle() function to demangle the symbols
obtained by backtrace_symbols().  This works almost fine.  However, can
somebody explain what does the symbol __gxx_personality_v0 mean?
Consider this example:

class A
{
public:
A() {}
};

class B
{
public:
B() {}
private:
A a;
};

int main()
{
B b;
return 0;
}

Note that class A is implemented in a shared library linked dynamically
to my example.  I see the backtrace from A's constructor, but I don't
see anything about B, the backtrace looks like this:

(stuff called from A's constructor)
A::A
__gxx_personality_v0
__gxx_personality_v0
__libc_start_main
__gxx_personality_v0

So my problem is I don't see where A is created from.
Can somebody enlighten me?
Thanks.