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/* Abstraction of GNU v3 abi. Contributed by Jim Blandy <jimb@redhat.com> Copyright 2001 Free Software Foundation, Inc. This file is part of GDB. This program is free software; you can redistribute it and/or modify it under the terms of the GNU General Public License as published by the Free Software Foundation; either version 2 of the License, or (at your option) any later version. This program is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for more details. You should have received a copy of the GNU General Public License along with this program; if not, write to the Free Software Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA. */ #include "defs.h" #include "value.h" #include "cp-abi.h" #include "demangle.h" #include "gdb_assert.h" static struct cp_abi_ops gnu_v3_abi_ops; static int gnuv3_is_vtable_name (const char *name) { return strncmp (name, "_ZTV", 4) == 0; } static int gnuv3_is_operator_name (const char *name) { return strncmp (name, "operator", 8) == 0; } /* To help us find the components of a vtable, we build ourselves a GDB type object representing the vtable structure. Following the V3 ABI, it goes something like this: struct gdb_gnu_v3_abi_vtable { / * An array of virtual call and virtual base offsets. The real length of this array depends on the class hierarchy; we use negative subscripts to access the elements. Yucky, but better than the alternatives. * / ptrdiff_t vcall_and_vbase_offsets[0]; / * The offset from a virtual pointer referring to this table to the top of the complete object. * / ptrdiff_t offset_to_top; / * The type_info pointer for this class. This is really a std::type_info *, but GDB doesn't really look at the type_info object itself, so we don't bother to get the type exactly right. * / void *type_info; / * Virtual table pointers in objects point here. * / / * Virtual function pointers. Like the vcall/vbase array, the real length of this table depends on the class hierarchy. * / void (*virtual_functions[0]) (); }; The catch, of course, is that the exact layout of this table depends on the ABI --- word size, endianness, alignment, etc. So the GDB type object is actually a per-architecture kind of thing. vtable_type_gdbarch_data is a gdbarch per-architecture data pointer which refers to the struct type * for this structure, laid out appropriately for the architecture. */ static struct gdbarch_data *vtable_type_gdbarch_data; /* Human-readable names for the numbers of the fields above. */ enum { vtable_field_vcall_and_vbase_offsets, vtable_field_offset_to_top, vtable_field_type_info, vtable_field_virtual_functions }; /* Return a GDB type representing `struct gdb_gnu_v3_abi_vtable', described above, laid out appropriately for ARCH. We use this function as the gdbarch per-architecture data initialization function. We assume that the gdbarch framework calls the per-architecture data initialization functions after it sets current_gdbarch to the new architecture. */ static void * build_gdb_vtable_type (struct gdbarch *arch) { struct type *t; struct field *field_list, *field; int offset; struct type *void_ptr_type = lookup_pointer_type (builtin_type_void); struct type *ptr_to_void_fn_type = lookup_pointer_type (lookup_function_type (builtin_type_void)); /* ARCH can't give us the true ptrdiff_t type, so we guess. */ struct type *ptrdiff_type = init_type (TYPE_CODE_INT, TARGET_PTR_BIT / TARGET_CHAR_BIT, 0, "ptrdiff_t", 0); /* We assume no padding is necessary, since GDB doesn't know anything about alignment at the moment. If this assumption bites us, we should add a gdbarch method which, given a type, returns the alignment that type requires, and then use that here. */ /* Build the field list. */ field_list = xmalloc (sizeof (struct field [4])); memset (field_list, 0, sizeof (struct field [4])); field = &field_list[0]; offset = 0; /* ptrdiff_t vcall_and_vbase_offsets[0]; */ FIELD_NAME (*field) = "vcall_and_vbase_offsets"; FIELD_TYPE (*field) = create_array_type (0, ptrdiff_type, create_range_type (0, builtin_type_int, 0, -1)); FIELD_BITPOS (*field) = offset * TARGET_CHAR_BIT; offset += TYPE_LENGTH (FIELD_TYPE (*field)); field++; /* ptrdiff_t offset_to_top; */ FIELD_NAME (*field) = "offset_to_top"; FIELD_TYPE (*field) = ptrdiff_type; FIELD_BITPOS (*field) = offset * TARGET_CHAR_BIT; offset += TYPE_LENGTH (FIELD_TYPE (*field)); field++; /* void *type_info; */ FIELD_NAME (*field) = "type_info"; FIELD_TYPE (*field) = void_ptr_type; FIELD_BITPOS (*field) = offset * TARGET_CHAR_BIT; offset += TYPE_LENGTH (FIELD_TYPE (*field)); field++; /* void (*virtual_functions[0]) (); */ FIELD_NAME (*field) = "virtual_functions"; FIELD_TYPE (*field) = create_array_type (0, ptr_to_void_fn_type, create_range_type (0, builtin_type_int, 0, -1)); FIELD_BITPOS (*field) = offset * TARGET_CHAR_BIT; offset += TYPE_LENGTH (FIELD_TYPE (*field)); field++; /* We assumed in the allocation above that there were four fields. */ gdb_assert (field == (field_list + 4)); t = init_type (TYPE_CODE_STRUCT, offset, 0, 0, 0); TYPE_NFIELDS (t) = field - field_list; TYPE_FIELDS (t) = field_list; TYPE_TAG_NAME (t) = "gdb_gnu_v3_abi_vtable"; return t; } /* Return the offset from the start of the imaginary `struct gdb_gnu_v3_abi_vtable' object to the vtable's "address point" (i.e., where objects' virtual table pointers point). */ static int vtable_address_point_offset () { struct type *vtable_type = gdbarch_data (vtable_type_gdbarch_data); return (TYPE_FIELD_BITPOS (vtable_type, vtable_field_virtual_functions) / TARGET_CHAR_BIT); } static struct type * gnuv3_rtti_type (struct value *value, int *full_p, int *top_p, int *using_enc_p) { struct type *vtable_type = gdbarch_data (vtable_type_gdbarch_data); struct type *value_type = check_typedef (VALUE_TYPE (value)); CORE_ADDR vtable_address; struct value *vtable; struct minimal_symbol *vtable_symbol; const char *vtable_symbol_name; const char *class_name; struct symbol *class_symbol; struct type *run_time_type; LONGEST offset_to_top; /* We only have RTTI for class objects. */ if (TYPE_CODE (value_type) != TYPE_CODE_CLASS) return NULL; /* If we can't find the virtual table pointer for value_type, we can't find the RTTI. */ fill_in_vptr_fieldno (value_type); if (TYPE_VPTR_FIELDNO (value_type) == -1) return NULL; /* Fetch VALUE's virtual table pointer, and tweak it to point at an instance of our imaginary gdb_gnu_v3_abi_vtable structure. */ vtable_address = value_as_pointer (value_field (value, TYPE_VPTR_FIELDNO (value_type))); vtable = value_at_lazy (vtable_type, vtable_address - vtable_address_point_offset (), VALUE_BFD_SECTION (value)); /* Find the linker symbol for this vtable. */ vtable_symbol = lookup_minimal_symbol_by_pc (VALUE_ADDRESS (vtable) + VALUE_OFFSET (vtable) + VALUE_EMBEDDED_OFFSET (vtable)); if (! vtable_symbol) return NULL; /* The symbol's demangled name should be something like "vtable for CLASS", where CLASS is the name of the run-time type of VALUE. If we didn't like this approach, we could instead look in the type_info object itself to get the class name. But this way should work just as well, and doesn't read target memory. */ vtable_symbol_name = SYMBOL_DEMANGLED_NAME (vtable_symbol); if (strncmp (vtable_symbol_name, "vtable for ", 11)) error ("can't find linker symbol for virtual table for `%s' value", TYPE_NAME (value_type)); class_name = vtable_symbol_name + 11; /* Try to look up the class name as a type name. */ class_symbol = lookup_symbol (class_name, 0, STRUCT_NAMESPACE, 0, 0); if (! class_symbol) error ("can't find class named `%s', as given by C++ RTTI", class_name); /* Make sure the type symbol is sane. (An earlier version of this code would find constructor functions, who have the same name as the class.) */ if (SYMBOL_CLASS (class_symbol) != LOC_TYPEDEF || TYPE_CODE (SYMBOL_TYPE (class_symbol)) != TYPE_CODE_CLASS) error ("C++ RTTI gives a class name of `%s', but that isn't a type name", class_name); /* This is the object's run-time type! */ run_time_type = SYMBOL_TYPE (class_symbol); /* Get the offset from VALUE to the top of the complete object. NOTE: this is the reverse of the meaning of *TOP_P. */ offset_to_top = value_as_long (value_field (vtable, vtable_field_offset_to_top)); if (full_p) *full_p = (- offset_to_top == VALUE_EMBEDDED_OFFSET (value) && (TYPE_LENGTH (VALUE_ENCLOSING_TYPE (value)) >= TYPE_LENGTH (run_time_type))); if (top_p) *top_p = - offset_to_top; if (using_enc_p) *using_enc_p = 0; return run_time_type; } static struct value * gnuv3_virtual_fn_field (struct value **value_p, struct fn_field *f, int j, struct type *type, int offset) { struct type *vtable_type = gdbarch_data (vtable_type_gdbarch_data); struct value *value = *value_p; struct type *value_type = check_typedef (VALUE_TYPE (value)); struct type *vfn_base; CORE_ADDR vtable_address; struct value *vtable; struct value *vfn; /* Some simple sanity checks. */ if (TYPE_CODE (value_type) != TYPE_CODE_CLASS) error ("Only classes can have virtual functions."); /* Find the base class that defines this virtual function. */ vfn_base = TYPE_FN_FIELD_FCONTEXT (f, j); if (! vfn_base) /* In programs compiled with G++ version 1, the debug info doesn't say which base class defined the virtual function. We'll guess it's the same base class that has our vtable; this is wrong for multiple inheritance, but it's better than nothing. */ vfn_base = TYPE_VPTR_BASETYPE (type); /* This type may have been defined before its virtual function table was. If so, fill in the virtual function table entry for the type now. */ if (TYPE_VPTR_FIELDNO (vfn_base) < 0) fill_in_vptr_fieldno (vfn_base); /* Now that we know which base class is defining our virtual function, cast our value to that baseclass. This takes care of any necessary `this' adjustments. */ if (vfn_base != value_type) /* It would be nicer to simply cast the value to the appropriate base class (and I think that is supposed to be legal), but value_cast only does the right magic when casting pointers. */ value = value_ind (value_cast (vfn_base, value_addr (value))); /* Now value is an object of the appropriate base type. Fetch its virtual table. */ vtable_address = value_as_pointer (value_field (value, TYPE_VPTR_FIELDNO (vfn_base))); vtable = value_at_lazy (vtable_type, vtable_address - vtable_address_point_offset (), VALUE_BFD_SECTION (value)); /* Fetch the appropriate function pointer from the vtable. */ vfn = value_subscript (value_field (vtable, vtable_field_virtual_functions), value_from_longest (builtin_type_int, TYPE_FN_FIELD_VOFFSET (f, j))); /* Cast the function pointer to the appropriate type. */ vfn = value_cast (lookup_pointer_type (TYPE_FN_FIELD_TYPE (f, j)), vfn); return vfn; } static void init_gnuv3_ops (void) { vtable_type_gdbarch_data = register_gdbarch_data (build_gdb_vtable_type, 0); gnu_v3_abi_ops.shortname = "gnu-v3"; gnu_v3_abi_ops.longname = "GNU G++ Version 3 ABI"; gnu_v3_abi_ops.doc = "G++ Version 3 ABI"; gnu_v3_abi_ops.is_destructor_name = is_gnu_v3_mangled_dtor; gnu_v3_abi_ops.is_constructor_name = is_gnu_v3_mangled_ctor; gnu_v3_abi_ops.is_vtable_name = gnuv3_is_vtable_name; gnu_v3_abi_ops.is_operator_name = gnuv3_is_operator_name; gnu_v3_abi_ops.rtti_type = gnuv3_rtti_type; gnu_v3_abi_ops.virtual_fn_field = gnuv3_virtual_fn_field; } void _initialize_gnu_v3_abi (void) { init_gnuv3_ops (); register_cp_abi (gnu_v3_abi_ops); }