How to get attual method in GCC AST

[Kien Nguyen Trung]

I am work on a project related with GCC AST.
In my project, i write a plugin for GCC. This plugin read a AST from a
source code, a covert this source code to another language.
Currently i have a problem with GCC AST. In particular, i cannot
retrieve all information about CALL_EXPR.
I read GCC internal, and i have known about structure of CALL_EXPR node in GCC.
But when i have a source code
class A{
public:
    virtual void read();
};
class B : A {
public:
    int a;

    void read() {}
};
class D {
public:
    void test() {
        B *b;
        b->read();
    }
};
int main(int argc, char** argv) {
    D d;
    d.test();
}

This is AST of method test in class D i got:
bind_expr (test.cpp:21-18)
    statement_list
      decl_expr (test.cpp:20-12)
        var_decl : b (B *) (test.cpp :20)
      cleanup_point_expr (test.cpp:21-18)
        expr_stmt (test.cpp:21-18)
          call_expr (test.cpp:21-17)
            obj_type_ref
              indirect_ref (test.cpp:21-17)
                non_lvalue_expr (test.cpp:21-17)
                  component_ref
                    component_ref
                      indirect_ref
                        non_lvalue_expr
                          var_decl : b (B *) (test.cpp :20)
                      field_decl : internal hidden (unknown type) (test.cpp :9)
                    field_decl : _vptr.A (int * *) (test.cpp :4)
              non_lvalue_expr
                var_decl : b (B *) (test.cpp :20)
              integer_cst 0
            non_lvalue_expr
              var_decl : b (B *) (test.cpp :20)

The problem is method read() of class B is get from a virtual method
of based class A. And i cannot get the real name of  this method.
Do you have any ideal to help me. Thansk