| /* Abstraction of GNU v3 abi. |
| Contributed by Jim Blandy <jimb@redhat.com> |
| |
| Copyright 2001, 2002, 2003, 2005 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 "cp-support.h" |
| #include "demangle.h" |
| #include "gdb_assert.h" |
| #include "gdb_string.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 (void) |
| { |
| struct type *vtable_type = gdbarch_data (current_gdbarch, |
| 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 (current_gdbarch, |
| vtable_type_gdbarch_data); |
| struct type *values_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 type *run_time_type; |
| struct type *base_type; |
| LONGEST offset_to_top; |
| |
| /* We only have RTTI for class objects. */ |
| if (TYPE_CODE (values_type) != TYPE_CODE_CLASS) |
| return NULL; |
| |
| /* If we can't find the virtual table pointer for values_type, we |
| can't find the RTTI. */ |
| fill_in_vptr_fieldno (values_type); |
| if (TYPE_VPTR_FIELDNO (values_type) == -1) |
| return NULL; |
| |
| if (using_enc_p) |
| *using_enc_p = 0; |
| |
| /* Fetch VALUE's virtual table pointer, and tweak it to point at |
| an instance of our imaginary gdb_gnu_v3_abi_vtable structure. */ |
| base_type = check_typedef (TYPE_VPTR_BASETYPE (values_type)); |
| if (values_type != base_type) |
| { |
| value = value_cast (base_type, value); |
| if (using_enc_p) |
| *using_enc_p = 1; |
| } |
| vtable_address |
| = value_as_address (value_field (value, TYPE_VPTR_FIELDNO (values_type))); |
| vtable = value_at_lazy (vtable_type, |
| vtable_address - vtable_address_point_offset ()); |
| |
| /* 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 (vtable_symbol_name == NULL |
| || strncmp (vtable_symbol_name, "vtable for ", 11)) |
| { |
| warning (_("can't find linker symbol for virtual table for `%s' value"), |
| TYPE_NAME (values_type)); |
| if (vtable_symbol_name) |
| warning (_(" found `%s' instead"), vtable_symbol_name); |
| return NULL; |
| } |
| class_name = vtable_symbol_name + 11; |
| |
| /* Try to look up the class name as a type name. */ |
| /* FIXME: chastain/2003-11-26: block=NULL is bogus. See pr gdb/1465. */ |
| run_time_type = cp_lookup_rtti_type (class_name, NULL); |
| if (run_time_type == NULL) |
| return NULL; |
| |
| /* 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; |
| |
| 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 (current_gdbarch, |
| vtable_type_gdbarch_data); |
| struct value *value = *value_p; |
| struct type *values_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 (values_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); |
| if (TYPE_VPTR_FIELDNO (vfn_base) < 0) |
| error (_("Could not find virtual table pointer for class \"%s\"."), |
| TYPE_TAG_NAME (vfn_base) ? TYPE_TAG_NAME (vfn_base) : "<unknown>"); |
| |
| /* 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 != values_type) |
| value = value_cast (vfn_base, value); |
| |
| /* Now value is an object of the appropriate base type. Fetch its |
| virtual table. */ |
| /* It might be possible to do this cast at the same time as the above. |
| Does multiple inheritance affect this? |
| Can this even trigger, or is TYPE_VPTR_BASETYPE idempotent? |
| */ |
| if (TYPE_VPTR_BASETYPE (vfn_base) != vfn_base) |
| value = value_cast (TYPE_VPTR_BASETYPE (vfn_base), value); |
| vtable_address |
| = value_as_address (value_field (value, TYPE_VPTR_FIELDNO (vfn_base))); |
| |
| vtable = value_at_lazy (vtable_type, |
| vtable_address - vtable_address_point_offset ()); |
| |
| /* 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); |
| |
| /* Is (type)value always numerically the same as (vfn_base)value? |
| If so we can spare this cast and use one of the ones above. */ |
| *value_p = value_addr (value_cast (type, *value_p)); |
| |
| return vfn; |
| } |
| |
| /* Compute the offset of the baseclass which is |
| the INDEXth baseclass of class TYPE, |
| for value at VALADDR (in host) at ADDRESS (in target). |
| The result is the offset of the baseclass value relative |
| to (the address of)(ARG) + OFFSET. |
| |
| -1 is returned on error. */ |
| static int |
| gnuv3_baseclass_offset (struct type *type, int index, const bfd_byte *valaddr, |
| CORE_ADDR address) |
| { |
| struct type *vtable_type = gdbarch_data (current_gdbarch, |
| vtable_type_gdbarch_data); |
| struct value *vtable; |
| struct type *vbasetype; |
| struct value *offset_val, *vbase_array; |
| CORE_ADDR vtable_address; |
| long int cur_base_offset, base_offset; |
| |
| /* If it isn't a virtual base, this is easy. The offset is in the |
| type definition. */ |
| if (!BASETYPE_VIA_VIRTUAL (type, index)) |
| return TYPE_BASECLASS_BITPOS (type, index) / 8; |
| |
| /* To access a virtual base, we need to use the vbase offset stored in |
| our vtable. Recent GCC versions provide this information. If it isn't |
| available, we could get what we needed from RTTI, or from drawing the |
| complete inheritance graph based on the debug info. Neither is |
| worthwhile. */ |
| cur_base_offset = TYPE_BASECLASS_BITPOS (type, index) / 8; |
| if (cur_base_offset >= - vtable_address_point_offset ()) |
| error (_("Expected a negative vbase offset (old compiler?)")); |
| |
| cur_base_offset = cur_base_offset + vtable_address_point_offset (); |
| if ((- cur_base_offset) % TYPE_LENGTH (builtin_type_void_data_ptr) != 0) |
| error (_("Misaligned vbase offset.")); |
| cur_base_offset = cur_base_offset |
| / ((int) TYPE_LENGTH (builtin_type_void_data_ptr)); |
| |
| /* We're now looking for the cur_base_offset'th entry (negative index) |
| in the vcall_and_vbase_offsets array. We used to cast the object to |
| its TYPE_VPTR_BASETYPE, and reference the vtable as TYPE_VPTR_FIELDNO; |
| however, that cast can not be done without calling baseclass_offset again |
| if the TYPE_VPTR_BASETYPE is a virtual base class, as described in the |
| v3 C++ ABI Section 2.4.I.2.b. Fortunately the ABI guarantees that the |
| vtable pointer will be located at the beginning of the object, so we can |
| bypass the casting. Verify that the TYPE_VPTR_FIELDNO is in fact at the |
| start of whichever baseclass it resides in, as a sanity measure - iff |
| we have debugging information for that baseclass. */ |
| |
| vbasetype = TYPE_VPTR_BASETYPE (type); |
| if (TYPE_VPTR_FIELDNO (vbasetype) < 0) |
| fill_in_vptr_fieldno (vbasetype); |
| |
| if (TYPE_VPTR_FIELDNO (vbasetype) >= 0 |
| && TYPE_FIELD_BITPOS (vbasetype, TYPE_VPTR_FIELDNO (vbasetype)) != 0) |
| error (_("Illegal vptr offset in class %s"), |
| TYPE_NAME (vbasetype) ? TYPE_NAME (vbasetype) : "<unknown>"); |
| |
| vtable_address = value_as_address (value_at_lazy (builtin_type_void_data_ptr, |
| address)); |
| vtable = value_at_lazy (vtable_type, |
| vtable_address - vtable_address_point_offset ()); |
| offset_val = value_from_longest(builtin_type_int, cur_base_offset); |
| vbase_array = value_field (vtable, vtable_field_vcall_and_vbase_offsets); |
| base_offset = value_as_long (value_subscript (vbase_array, offset_val)); |
| return base_offset; |
| } |
| |
| static void |
| init_gnuv3_ops (void) |
| { |
| vtable_type_gdbarch_data = gdbarch_data_register_post_init (build_gdb_vtable_type); |
| |
| 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 = |
| (enum dtor_kinds (*) (const char *))is_gnu_v3_mangled_dtor; |
| gnu_v3_abi_ops.is_constructor_name = |
| (enum ctor_kinds (*) (const char *))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; |
| gnu_v3_abi_ops.baseclass_offset = gnuv3_baseclass_offset; |
| } |
| |
| extern initialize_file_ftype _initialize_gnu_v3_abi; /* -Wmissing-prototypes */ |
| |
| void |
| _initialize_gnu_v3_abi (void) |
| { |
| init_gnuv3_ops (); |
| |
| register_cp_abi (&gnu_v3_abi_ops); |
| } |