Studying note of GCC-3.4.6 source (157)

5.13.4.2.              Iterate - emitting tinfo

Now all tinfos need code emitted have been chained into unemitted_tinfo_decls , then in finish_file at line 2628, emit_tinfo_decl determines whether the tinfo of decl needs be emitted, returns true if so. Below see that doing_runtime is set as 1 in emit_support_tinfos which is invoked at line 2571 in finish_file before.

Then at point invoking class_initializer (emit_tinfo_decl à get_pseudo_ti_init ), argument trail will be tree in below figure. Note that VAR_DECL of tinfo of base has been generated with initializers (desc is the corresponding VAR_DECL for tinfo of current class).

 

951    static tree

952    class_initializer (tree desc, tree target, tree trail)                                                  in rtti.c

953    {

954      tree init = tinfo_base_init (desc, target);

955     

956      TREE_CHAIN (init) = trail;

957      init = build_constructor (NULL_TREE, init);

958      TREE_HAS_CONSTRUCTOR (init) = TREE_CONSTANT (init) = TREE_STATIC (init) = 1;

959      return init; 

960    }

 

See that in class type_info, there is a “const char *” field name , block beginning at line 745 generates initializing code and the mangled name for this field.

 

738    static tree

739    tinfo_base_init (tree desc, tree target)                                                                in rtti.c

740    {

741      tree init = NULL_TREE;

742      tree name_decl;

743      tree vtable_ptr;

744     

745      {

746        tree name_name;

747       

748        /* Generate the NTBS array variable.  */

749        tree name_type = build_cplus_array_type

750                       (build_qualified_type (char_type_node, TYPE_QUAL_CONST),

751                        NULL_TREE);

752         tree name_string = tinfo_name (target);

753   

754        name_name = mangle_typeinfo_string_for_type (target);

755        name_decl = build_lang_decl (VAR_DECL, name_name, name_type);

756       

757        DECL_ARTIFICIAL (name_decl) = 1;

758        TREE_READONLY (name_decl) = 1;

759        TREE_STATIC (name_decl) = 1;

760        DECL_EXTERNAL (name_decl) = 0;

761        TREE_PUBLIC (name_decl) = 1;

762        import_export_tinfo (name_decl, target, typeinfo_in_lib_p (target));

763        /* External name of the string containing the type's name has a

764          special name.  */

765        SET_DECL_ASSEMBLER_NAME (name_decl,

766                                       mangle_typeinfo_string_for_type (target));

767        DECL_INITIAL (name_decl) = name_string;

768        mark_used (name_decl);

769        pushdecl_top_level_and_finish (name_decl, name_string);

770      }

771   

772      vtable_ptr = TINFO_VTABLE_DECL (desc);

773      if (!vtable_ptr)

774      {

775        tree real_type;

776     

777        push_nested_namespace (abi_node);

778        real_type = xref_tag (class_type, TINFO_REAL_NAME (desc),

779                          true, false);

780        pop_nested_namespace (abi_node);

781     

782        if (!COMPLETE_TYPE_P (real_type))

783        {

784          /* We never saw a definition of this type, so we need to

785            tell the compiler that this is an exported class, as

786            indeed all of the __*_type_info classes are.  */

787          SET_CLASSTYPE_INTERFACE_KNOWN (real_type);

788          CLASSTYPE_INTERFACE_ONLY (real_type) = 1;

789        }

790   

791        vtable_ptr = get_vtable_decl (real_type, /*complete=*/ 1);

792        vtable_ptr = build_unary_op (ADDR_EXPR, vtable_ptr, 0);

793   

794        /* We need to point into the middle of the vtable.  */

795        vtable_ptr = build

796                   (PLUS_EXPR, TREE_TYPE (vtable_ptr), vtable_ptr,

797                    size_binop (MULT_EXPR,

798                        size_int (2 * TARGET_VTABLE_DATA_ENTRY_DISTANCE),

799                        TYPE_SIZE_UNIT (vtable_entry_type )));

800        TREE_CONSTANT (vtable_ptr) = 1;

801   

802        TINFO_VTABLE_DECL (desc) = vtable_ptr;

803      }

804   

805      init = tree_cons (NULL_TREE, vtable_ptr, init);

806     

807      init = tree_cons (NULL_TREE, decay_conversion (name_decl), init);

808     

809      init = build_constructor (NULL_TREE, nreverse (init));

810      TREE_HAS_CONSTRUCTOR (init) = TREE_CONSTANT (init) = TREE_STATIC (init) = 1;

811       init = tree_cons (NULL_TREE, init, NULL_TREE);

812     

813      return init;

814    }

 

Notice that above at line 791, the last argument of get_vtable_decl is 1, the function creates the VAR_DECL of vtable for this type of tinfo, and this VRA_DECL is marked as external, but within which cp_finish_decl does nothing.

Finally, var_init in emit_tinfo_decl at line 1452 is the following tree. And var_init will be used as initializer for this tinfo. And at line 1461 in emit_tinfo_decl , decl is the VAR_DECL of the tinfo, as we have seen in former section, cp_finish_decl has nothing to do.

If emit_tinfo_decl returns successfully, it means the intermediate tree has been changed, forces to iterate the DO WHILE loop again.