| 1 | /* Abstraction of GNU v3 abi. |
| 2 | Contributed by Jim Blandy <jimb@redhat.com> |
| 3 | |
| 4 | Copyright 2001, 2002, 2003 Free Software Foundation, Inc. |
| 5 | |
| 6 | This file is part of GDB. |
| 7 | |
| 8 | This program is free software; you can redistribute it and/or |
| 9 | modify it under the terms of the GNU General Public License as |
| 10 | published by the Free Software Foundation; either version 2 of the |
| 11 | License, or (at your option) any later version. |
| 12 | |
| 13 | This program is distributed in the hope that it will be useful, |
| 14 | but WITHOUT ANY WARRANTY; without even the implied warranty of |
| 15 | MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the |
| 16 | GNU General Public License for more details. |
| 17 | |
| 18 | You should have received a copy of the GNU General Public License |
| 19 | along with this program; if not, write to the Free Software |
| 20 | Foundation, Inc., 59 Temple Place - Suite 330, |
| 21 | Boston, MA 02111-1307, USA. */ |
| 22 | |
| 23 | #include "defs.h" |
| 24 | #include "value.h" |
| 25 | #include "cp-abi.h" |
| 26 | #include "cp-support.h" |
| 27 | #include "demangle.h" |
| 28 | #include "gdb_assert.h" |
| 29 | #include "gdb_string.h" |
| 30 | |
| 31 | static struct cp_abi_ops gnu_v3_abi_ops; |
| 32 | |
| 33 | static int |
| 34 | gnuv3_is_vtable_name (const char *name) |
| 35 | { |
| 36 | return strncmp (name, "_ZTV", 4) == 0; |
| 37 | } |
| 38 | |
| 39 | static int |
| 40 | gnuv3_is_operator_name (const char *name) |
| 41 | { |
| 42 | return strncmp (name, "operator", 8) == 0; |
| 43 | } |
| 44 | |
| 45 | |
| 46 | /* To help us find the components of a vtable, we build ourselves a |
| 47 | GDB type object representing the vtable structure. Following the |
| 48 | V3 ABI, it goes something like this: |
| 49 | |
| 50 | struct gdb_gnu_v3_abi_vtable { |
| 51 | |
| 52 | / * An array of virtual call and virtual base offsets. The real |
| 53 | length of this array depends on the class hierarchy; we use |
| 54 | negative subscripts to access the elements. Yucky, but |
| 55 | better than the alternatives. * / |
| 56 | ptrdiff_t vcall_and_vbase_offsets[0]; |
| 57 | |
| 58 | / * The offset from a virtual pointer referring to this table |
| 59 | to the top of the complete object. * / |
| 60 | ptrdiff_t offset_to_top; |
| 61 | |
| 62 | / * The type_info pointer for this class. This is really a |
| 63 | std::type_info *, but GDB doesn't really look at the |
| 64 | type_info object itself, so we don't bother to get the type |
| 65 | exactly right. * / |
| 66 | void *type_info; |
| 67 | |
| 68 | / * Virtual table pointers in objects point here. * / |
| 69 | |
| 70 | / * Virtual function pointers. Like the vcall/vbase array, the |
| 71 | real length of this table depends on the class hierarchy. * / |
| 72 | void (*virtual_functions[0]) (); |
| 73 | |
| 74 | }; |
| 75 | |
| 76 | The catch, of course, is that the exact layout of this table |
| 77 | depends on the ABI --- word size, endianness, alignment, etc. So |
| 78 | the GDB type object is actually a per-architecture kind of thing. |
| 79 | |
| 80 | vtable_type_gdbarch_data is a gdbarch per-architecture data pointer |
| 81 | which refers to the struct type * for this structure, laid out |
| 82 | appropriately for the architecture. */ |
| 83 | static struct gdbarch_data *vtable_type_gdbarch_data; |
| 84 | |
| 85 | |
| 86 | /* Human-readable names for the numbers of the fields above. */ |
| 87 | enum { |
| 88 | vtable_field_vcall_and_vbase_offsets, |
| 89 | vtable_field_offset_to_top, |
| 90 | vtable_field_type_info, |
| 91 | vtable_field_virtual_functions |
| 92 | }; |
| 93 | |
| 94 | |
| 95 | /* Return a GDB type representing `struct gdb_gnu_v3_abi_vtable', |
| 96 | described above, laid out appropriately for ARCH. |
| 97 | |
| 98 | We use this function as the gdbarch per-architecture data |
| 99 | initialization function. We assume that the gdbarch framework |
| 100 | calls the per-architecture data initialization functions after it |
| 101 | sets current_gdbarch to the new architecture. */ |
| 102 | static void * |
| 103 | build_gdb_vtable_type (struct gdbarch *arch) |
| 104 | { |
| 105 | struct type *t; |
| 106 | struct field *field_list, *field; |
| 107 | int offset; |
| 108 | |
| 109 | struct type *void_ptr_type |
| 110 | = lookup_pointer_type (builtin_type_void); |
| 111 | struct type *ptr_to_void_fn_type |
| 112 | = lookup_pointer_type (lookup_function_type (builtin_type_void)); |
| 113 | |
| 114 | /* ARCH can't give us the true ptrdiff_t type, so we guess. */ |
| 115 | struct type *ptrdiff_type |
| 116 | = init_type (TYPE_CODE_INT, TARGET_PTR_BIT / TARGET_CHAR_BIT, 0, |
| 117 | "ptrdiff_t", 0); |
| 118 | |
| 119 | /* We assume no padding is necessary, since GDB doesn't know |
| 120 | anything about alignment at the moment. If this assumption bites |
| 121 | us, we should add a gdbarch method which, given a type, returns |
| 122 | the alignment that type requires, and then use that here. */ |
| 123 | |
| 124 | /* Build the field list. */ |
| 125 | field_list = xmalloc (sizeof (struct field [4])); |
| 126 | memset (field_list, 0, sizeof (struct field [4])); |
| 127 | field = &field_list[0]; |
| 128 | offset = 0; |
| 129 | |
| 130 | /* ptrdiff_t vcall_and_vbase_offsets[0]; */ |
| 131 | FIELD_NAME (*field) = "vcall_and_vbase_offsets"; |
| 132 | FIELD_TYPE (*field) |
| 133 | = create_array_type (0, ptrdiff_type, |
| 134 | create_range_type (0, builtin_type_int, 0, -1)); |
| 135 | FIELD_BITPOS (*field) = offset * TARGET_CHAR_BIT; |
| 136 | offset += TYPE_LENGTH (FIELD_TYPE (*field)); |
| 137 | field++; |
| 138 | |
| 139 | /* ptrdiff_t offset_to_top; */ |
| 140 | FIELD_NAME (*field) = "offset_to_top"; |
| 141 | FIELD_TYPE (*field) = ptrdiff_type; |
| 142 | FIELD_BITPOS (*field) = offset * TARGET_CHAR_BIT; |
| 143 | offset += TYPE_LENGTH (FIELD_TYPE (*field)); |
| 144 | field++; |
| 145 | |
| 146 | /* void *type_info; */ |
| 147 | FIELD_NAME (*field) = "type_info"; |
| 148 | FIELD_TYPE (*field) = void_ptr_type; |
| 149 | FIELD_BITPOS (*field) = offset * TARGET_CHAR_BIT; |
| 150 | offset += TYPE_LENGTH (FIELD_TYPE (*field)); |
| 151 | field++; |
| 152 | |
| 153 | /* void (*virtual_functions[0]) (); */ |
| 154 | FIELD_NAME (*field) = "virtual_functions"; |
| 155 | FIELD_TYPE (*field) |
| 156 | = create_array_type (0, ptr_to_void_fn_type, |
| 157 | create_range_type (0, builtin_type_int, 0, -1)); |
| 158 | FIELD_BITPOS (*field) = offset * TARGET_CHAR_BIT; |
| 159 | offset += TYPE_LENGTH (FIELD_TYPE (*field)); |
| 160 | field++; |
| 161 | |
| 162 | /* We assumed in the allocation above that there were four fields. */ |
| 163 | gdb_assert (field == (field_list + 4)); |
| 164 | |
| 165 | t = init_type (TYPE_CODE_STRUCT, offset, 0, 0, 0); |
| 166 | TYPE_NFIELDS (t) = field - field_list; |
| 167 | TYPE_FIELDS (t) = field_list; |
| 168 | TYPE_TAG_NAME (t) = "gdb_gnu_v3_abi_vtable"; |
| 169 | |
| 170 | return t; |
| 171 | } |
| 172 | |
| 173 | |
| 174 | /* Return the offset from the start of the imaginary `struct |
| 175 | gdb_gnu_v3_abi_vtable' object to the vtable's "address point" |
| 176 | (i.e., where objects' virtual table pointers point). */ |
| 177 | static int |
| 178 | vtable_address_point_offset (void) |
| 179 | { |
| 180 | struct type *vtable_type = gdbarch_data (current_gdbarch, |
| 181 | vtable_type_gdbarch_data); |
| 182 | |
| 183 | return (TYPE_FIELD_BITPOS (vtable_type, vtable_field_virtual_functions) |
| 184 | / TARGET_CHAR_BIT); |
| 185 | } |
| 186 | |
| 187 | |
| 188 | static struct type * |
| 189 | gnuv3_rtti_type (struct value *value, |
| 190 | int *full_p, int *top_p, int *using_enc_p) |
| 191 | { |
| 192 | struct type *vtable_type = gdbarch_data (current_gdbarch, |
| 193 | vtable_type_gdbarch_data); |
| 194 | struct type *values_type = check_typedef (value_type (value)); |
| 195 | CORE_ADDR vtable_address; |
| 196 | struct value *vtable; |
| 197 | struct minimal_symbol *vtable_symbol; |
| 198 | const char *vtable_symbol_name; |
| 199 | const char *class_name; |
| 200 | struct type *run_time_type; |
| 201 | struct type *base_type; |
| 202 | LONGEST offset_to_top; |
| 203 | |
| 204 | /* We only have RTTI for class objects. */ |
| 205 | if (TYPE_CODE (values_type) != TYPE_CODE_CLASS) |
| 206 | return NULL; |
| 207 | |
| 208 | /* If we can't find the virtual table pointer for values_type, we |
| 209 | can't find the RTTI. */ |
| 210 | fill_in_vptr_fieldno (values_type); |
| 211 | if (TYPE_VPTR_FIELDNO (values_type) == -1) |
| 212 | return NULL; |
| 213 | |
| 214 | if (using_enc_p) |
| 215 | *using_enc_p = 0; |
| 216 | |
| 217 | /* Fetch VALUE's virtual table pointer, and tweak it to point at |
| 218 | an instance of our imaginary gdb_gnu_v3_abi_vtable structure. */ |
| 219 | base_type = check_typedef (TYPE_VPTR_BASETYPE (values_type)); |
| 220 | if (values_type != base_type) |
| 221 | { |
| 222 | value = value_cast (base_type, value); |
| 223 | if (using_enc_p) |
| 224 | *using_enc_p = 1; |
| 225 | } |
| 226 | vtable_address |
| 227 | = value_as_address (value_field (value, TYPE_VPTR_FIELDNO (values_type))); |
| 228 | vtable = value_at_lazy (vtable_type, |
| 229 | vtable_address - vtable_address_point_offset ()); |
| 230 | |
| 231 | /* Find the linker symbol for this vtable. */ |
| 232 | vtable_symbol |
| 233 | = lookup_minimal_symbol_by_pc (VALUE_ADDRESS (vtable) |
| 234 | + value_offset (vtable) |
| 235 | + VALUE_EMBEDDED_OFFSET (vtable)); |
| 236 | if (! vtable_symbol) |
| 237 | return NULL; |
| 238 | |
| 239 | /* The symbol's demangled name should be something like "vtable for |
| 240 | CLASS", where CLASS is the name of the run-time type of VALUE. |
| 241 | If we didn't like this approach, we could instead look in the |
| 242 | type_info object itself to get the class name. But this way |
| 243 | should work just as well, and doesn't read target memory. */ |
| 244 | vtable_symbol_name = SYMBOL_DEMANGLED_NAME (vtable_symbol); |
| 245 | if (vtable_symbol_name == NULL |
| 246 | || strncmp (vtable_symbol_name, "vtable for ", 11)) |
| 247 | { |
| 248 | warning ("can't find linker symbol for virtual table for `%s' value", |
| 249 | TYPE_NAME (values_type)); |
| 250 | if (vtable_symbol_name) |
| 251 | warning (" found `%s' instead", vtable_symbol_name); |
| 252 | return NULL; |
| 253 | } |
| 254 | class_name = vtable_symbol_name + 11; |
| 255 | |
| 256 | /* Try to look up the class name as a type name. */ |
| 257 | /* FIXME: chastain/2003-11-26: block=NULL is bogus. See pr gdb/1465. */ |
| 258 | run_time_type = cp_lookup_rtti_type (class_name, NULL); |
| 259 | if (run_time_type == NULL) |
| 260 | return NULL; |
| 261 | |
| 262 | /* Get the offset from VALUE to the top of the complete object. |
| 263 | NOTE: this is the reverse of the meaning of *TOP_P. */ |
| 264 | offset_to_top |
| 265 | = value_as_long (value_field (vtable, vtable_field_offset_to_top)); |
| 266 | |
| 267 | if (full_p) |
| 268 | *full_p = (- offset_to_top == VALUE_EMBEDDED_OFFSET (value) |
| 269 | && (TYPE_LENGTH (VALUE_ENCLOSING_TYPE (value)) |
| 270 | >= TYPE_LENGTH (run_time_type))); |
| 271 | if (top_p) |
| 272 | *top_p = - offset_to_top; |
| 273 | |
| 274 | return run_time_type; |
| 275 | } |
| 276 | |
| 277 | |
| 278 | static struct value * |
| 279 | gnuv3_virtual_fn_field (struct value **value_p, |
| 280 | struct fn_field *f, int j, |
| 281 | struct type *type, int offset) |
| 282 | { |
| 283 | struct type *vtable_type = gdbarch_data (current_gdbarch, |
| 284 | vtable_type_gdbarch_data); |
| 285 | struct value *value = *value_p; |
| 286 | struct type *values_type = check_typedef (value_type (value)); |
| 287 | struct type *vfn_base; |
| 288 | CORE_ADDR vtable_address; |
| 289 | struct value *vtable; |
| 290 | struct value *vfn; |
| 291 | |
| 292 | /* Some simple sanity checks. */ |
| 293 | if (TYPE_CODE (values_type) != TYPE_CODE_CLASS) |
| 294 | error ("Only classes can have virtual functions."); |
| 295 | |
| 296 | /* Find the base class that defines this virtual function. */ |
| 297 | vfn_base = TYPE_FN_FIELD_FCONTEXT (f, j); |
| 298 | if (! vfn_base) |
| 299 | /* In programs compiled with G++ version 1, the debug info doesn't |
| 300 | say which base class defined the virtual function. We'll guess |
| 301 | it's the same base class that has our vtable; this is wrong for |
| 302 | multiple inheritance, but it's better than nothing. */ |
| 303 | vfn_base = TYPE_VPTR_BASETYPE (type); |
| 304 | |
| 305 | /* This type may have been defined before its virtual function table |
| 306 | was. If so, fill in the virtual function table entry for the |
| 307 | type now. */ |
| 308 | if (TYPE_VPTR_FIELDNO (vfn_base) < 0) |
| 309 | fill_in_vptr_fieldno (vfn_base); |
| 310 | if (TYPE_VPTR_FIELDNO (vfn_base) < 0) |
| 311 | error ("Could not find virtual table pointer for class \"%s\".", |
| 312 | TYPE_TAG_NAME (vfn_base) ? TYPE_TAG_NAME (vfn_base) : "<unknown>"); |
| 313 | |
| 314 | /* Now that we know which base class is defining our virtual |
| 315 | function, cast our value to that baseclass. This takes care of |
| 316 | any necessary `this' adjustments. */ |
| 317 | if (vfn_base != values_type) |
| 318 | value = value_cast (vfn_base, value); |
| 319 | |
| 320 | /* Now value is an object of the appropriate base type. Fetch its |
| 321 | virtual table. */ |
| 322 | /* It might be possible to do this cast at the same time as the above. |
| 323 | Does multiple inheritance affect this? |
| 324 | Can this even trigger, or is TYPE_VPTR_BASETYPE idempotent? |
| 325 | */ |
| 326 | if (TYPE_VPTR_BASETYPE (vfn_base) != vfn_base) |
| 327 | value = value_cast (TYPE_VPTR_BASETYPE (vfn_base), value); |
| 328 | vtable_address |
| 329 | = value_as_address (value_field (value, TYPE_VPTR_FIELDNO (vfn_base))); |
| 330 | |
| 331 | vtable = value_at_lazy (vtable_type, |
| 332 | vtable_address - vtable_address_point_offset ()); |
| 333 | |
| 334 | /* Fetch the appropriate function pointer from the vtable. */ |
| 335 | vfn = value_subscript (value_field (vtable, vtable_field_virtual_functions), |
| 336 | value_from_longest (builtin_type_int, |
| 337 | TYPE_FN_FIELD_VOFFSET (f, j))); |
| 338 | |
| 339 | /* Cast the function pointer to the appropriate type. */ |
| 340 | vfn = value_cast (lookup_pointer_type (TYPE_FN_FIELD_TYPE (f, j)), |
| 341 | vfn); |
| 342 | |
| 343 | /* Is (type)value always numerically the same as (vfn_base)value? |
| 344 | If so we can spare this cast and use one of the ones above. */ |
| 345 | *value_p = value_addr (value_cast (type, *value_p)); |
| 346 | |
| 347 | return vfn; |
| 348 | } |
| 349 | |
| 350 | /* Compute the offset of the baseclass which is |
| 351 | the INDEXth baseclass of class TYPE, |
| 352 | for value at VALADDR (in host) at ADDRESS (in target). |
| 353 | The result is the offset of the baseclass value relative |
| 354 | to (the address of)(ARG) + OFFSET. |
| 355 | |
| 356 | -1 is returned on error. */ |
| 357 | static int |
| 358 | gnuv3_baseclass_offset (struct type *type, int index, char *valaddr, |
| 359 | CORE_ADDR address) |
| 360 | { |
| 361 | struct type *vtable_type = gdbarch_data (current_gdbarch, |
| 362 | vtable_type_gdbarch_data); |
| 363 | struct value *vtable; |
| 364 | struct type *vbasetype; |
| 365 | struct value *offset_val, *vbase_array; |
| 366 | CORE_ADDR vtable_address; |
| 367 | long int cur_base_offset, base_offset; |
| 368 | |
| 369 | /* If it isn't a virtual base, this is easy. The offset is in the |
| 370 | type definition. */ |
| 371 | if (!BASETYPE_VIA_VIRTUAL (type, index)) |
| 372 | return TYPE_BASECLASS_BITPOS (type, index) / 8; |
| 373 | |
| 374 | /* To access a virtual base, we need to use the vbase offset stored in |
| 375 | our vtable. Recent GCC versions provide this information. If it isn't |
| 376 | available, we could get what we needed from RTTI, or from drawing the |
| 377 | complete inheritance graph based on the debug info. Neither is |
| 378 | worthwhile. */ |
| 379 | cur_base_offset = TYPE_BASECLASS_BITPOS (type, index) / 8; |
| 380 | if (cur_base_offset >= - vtable_address_point_offset ()) |
| 381 | error ("Expected a negative vbase offset (old compiler?)"); |
| 382 | |
| 383 | cur_base_offset = cur_base_offset + vtable_address_point_offset (); |
| 384 | if ((- cur_base_offset) % TYPE_LENGTH (builtin_type_void_data_ptr) != 0) |
| 385 | error ("Misaligned vbase offset."); |
| 386 | cur_base_offset = cur_base_offset |
| 387 | / ((int) TYPE_LENGTH (builtin_type_void_data_ptr)); |
| 388 | |
| 389 | /* We're now looking for the cur_base_offset'th entry (negative index) |
| 390 | in the vcall_and_vbase_offsets array. We used to cast the object to |
| 391 | its TYPE_VPTR_BASETYPE, and reference the vtable as TYPE_VPTR_FIELDNO; |
| 392 | however, that cast can not be done without calling baseclass_offset again |
| 393 | if the TYPE_VPTR_BASETYPE is a virtual base class, as described in the |
| 394 | v3 C++ ABI Section 2.4.I.2.b. Fortunately the ABI guarantees that the |
| 395 | vtable pointer will be located at the beginning of the object, so we can |
| 396 | bypass the casting. Verify that the TYPE_VPTR_FIELDNO is in fact at the |
| 397 | start of whichever baseclass it resides in, as a sanity measure - iff |
| 398 | we have debugging information for that baseclass. */ |
| 399 | |
| 400 | vbasetype = TYPE_VPTR_BASETYPE (type); |
| 401 | if (TYPE_VPTR_FIELDNO (vbasetype) < 0) |
| 402 | fill_in_vptr_fieldno (vbasetype); |
| 403 | |
| 404 | if (TYPE_VPTR_FIELDNO (vbasetype) >= 0 |
| 405 | && TYPE_FIELD_BITPOS (vbasetype, TYPE_VPTR_FIELDNO (vbasetype)) != 0) |
| 406 | error ("Illegal vptr offset in class %s", |
| 407 | TYPE_NAME (vbasetype) ? TYPE_NAME (vbasetype) : "<unknown>"); |
| 408 | |
| 409 | vtable_address = value_as_address (value_at_lazy (builtin_type_void_data_ptr, |
| 410 | address)); |
| 411 | vtable = value_at_lazy (vtable_type, |
| 412 | vtable_address - vtable_address_point_offset ()); |
| 413 | offset_val = value_from_longest(builtin_type_int, cur_base_offset); |
| 414 | vbase_array = value_field (vtable, vtable_field_vcall_and_vbase_offsets); |
| 415 | base_offset = value_as_long (value_subscript (vbase_array, offset_val)); |
| 416 | return base_offset; |
| 417 | } |
| 418 | |
| 419 | static void |
| 420 | init_gnuv3_ops (void) |
| 421 | { |
| 422 | vtable_type_gdbarch_data = gdbarch_data_register_post_init (build_gdb_vtable_type); |
| 423 | |
| 424 | gnu_v3_abi_ops.shortname = "gnu-v3"; |
| 425 | gnu_v3_abi_ops.longname = "GNU G++ Version 3 ABI"; |
| 426 | gnu_v3_abi_ops.doc = "G++ Version 3 ABI"; |
| 427 | gnu_v3_abi_ops.is_destructor_name = is_gnu_v3_mangled_dtor; |
| 428 | gnu_v3_abi_ops.is_constructor_name = is_gnu_v3_mangled_ctor; |
| 429 | gnu_v3_abi_ops.is_vtable_name = gnuv3_is_vtable_name; |
| 430 | gnu_v3_abi_ops.is_operator_name = gnuv3_is_operator_name; |
| 431 | gnu_v3_abi_ops.rtti_type = gnuv3_rtti_type; |
| 432 | gnu_v3_abi_ops.virtual_fn_field = gnuv3_virtual_fn_field; |
| 433 | gnu_v3_abi_ops.baseclass_offset = gnuv3_baseclass_offset; |
| 434 | } |
| 435 | |
| 436 | extern initialize_file_ftype _initialize_gnu_v3_abi; /* -Wmissing-prototypes */ |
| 437 | |
| 438 | void |
| 439 | _initialize_gnu_v3_abi (void) |
| 440 | { |
| 441 | init_gnuv3_ops (); |
| 442 | |
| 443 | register_cp_abi (&gnu_v3_abi_ops); |
| 444 | } |