1 /* Abstraction of GNU v2 abi. 2 3 Copyright (C) 2001-2023 Free Software Foundation, Inc. 4 5 Contributed by Daniel Berlin <dberlin@redhat.com> 6 7 This file is part of GDB. 8 9 This program is free software; you can redistribute it and/or modify 10 it under the terms of the GNU General Public License as published by 11 the Free Software Foundation; either version 3 of the License, or 12 (at your option) any later version. 13 14 This program is distributed in the hope that it will be useful, 15 but WITHOUT ANY WARRANTY; without even the implied warranty of 16 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the 17 GNU General Public License for more details. 18 19 You should have received a copy of the GNU General Public License 20 along with this program. If not, see <http://www.gnu.org/licenses/>. */ 21 22 #include "defs.h" 23 #include "symtab.h" 24 #include "gdbtypes.h" 25 #include "value.h" 26 #include "demangle.h" 27 #include "gdb-demangle.h" 28 #include "cp-abi.h" 29 #include "cp-support.h" 30 #include <ctype.h> 31 32 static cp_abi_ops gnu_v2_abi_ops; 33 34 static int vb_match (struct type *, int, struct type *); 35 36 static enum dtor_kinds 37 gnuv2_is_destructor_name (const char *name) 38 { 39 if ((name[0] == '_' && is_cplus_marker (name[1]) && name[2] == '_') 40 || startswith (name, "__dt__")) 41 return complete_object_dtor; 42 else 43 return (enum dtor_kinds) 0; 44 } 45 46 static enum ctor_kinds 47 gnuv2_is_constructor_name (const char *name) 48 { 49 if ((name[0] == '_' && name[1] == '_' 50 && (isdigit (name[2]) || strchr ("Qt", name[2]))) 51 || startswith (name, "__ct__")) 52 return complete_object_ctor; 53 else 54 return (enum ctor_kinds) 0; 55 } 56 57 static int 58 gnuv2_is_vtable_name (const char *name) 59 { 60 return (((name)[0] == '_' 61 && (((name)[1] == 'V' && (name)[2] == 'T') 62 || ((name)[1] == 'v' && (name)[2] == 't')) 63 && is_cplus_marker ((name)[3])) || 64 ((name)[0] == '_' && (name)[1] == '_' 65 && (name)[2] == 'v' && (name)[3] == 't' && (name)[4] == '_')); 66 } 67 68 static int 69 gnuv2_is_operator_name (const char *name) 70 { 71 return startswith (name, CP_OPERATOR_STR); 72 } 73 74 75 /* Return a virtual function as a value. 76 ARG1 is the object which provides the virtual function 77 table pointer. *ARG1P is side-effected in calling this function. 78 F is the list of member functions which contains the desired virtual 79 function. 80 J is an index into F which provides the desired virtual function. 81 82 TYPE is the type in which F is located. */ 83 static struct value * 84 gnuv2_virtual_fn_field (struct value **arg1p, struct fn_field * f, int j, 85 struct type * type, int offset) 86 { 87 struct value *arg1 = *arg1p; 88 struct type *type1 = check_typedef (value_type (arg1)); 89 struct type *entry_type; 90 /* First, get the virtual function table pointer. That comes 91 with a strange type, so cast it to type `pointer to long' (which 92 should serve just fine as a function type). Then, index into 93 the table, and convert final value to appropriate function type. */ 94 struct value *entry; 95 struct value *vfn; 96 struct value *vtbl; 97 LONGEST vi = (LONGEST) TYPE_FN_FIELD_VOFFSET (f, j); 98 struct type *fcontext = TYPE_FN_FIELD_FCONTEXT (f, j); 99 struct type *context; 100 struct type *context_vptr_basetype; 101 int context_vptr_fieldno; 102 103 if (fcontext == NULL) 104 /* We don't have an fcontext (e.g. the program was compiled with 105 g++ version 1). Try to get the vtbl from the TYPE_VPTR_BASETYPE. 106 This won't work right for multiple inheritance, but at least we 107 should do as well as GDB 3.x did. */ 108 fcontext = TYPE_VPTR_BASETYPE (type); 109 context = lookup_pointer_type (fcontext); 110 /* Now context is a pointer to the basetype containing the vtbl. */ 111 if (context->target_type () != type1) 112 { 113 struct value *tmp = value_cast (context, value_addr (arg1)); 114 115 arg1 = value_ind (tmp); 116 type1 = check_typedef (value_type (arg1)); 117 } 118 119 context = type1; 120 /* Now context is the basetype containing the vtbl. */ 121 122 /* This type may have been defined before its virtual function table 123 was. If so, fill in the virtual function table entry for the 124 type now. */ 125 context_vptr_fieldno = get_vptr_fieldno (context, &context_vptr_basetype); 126 /* FIXME: What to do if vptr_fieldno is still -1? */ 127 128 /* The virtual function table is now an array of structures 129 which have the form { int16 offset, delta; void *pfn; }. */ 130 vtbl = value_primitive_field (arg1, 0, context_vptr_fieldno, 131 context_vptr_basetype); 132 133 /* With older versions of g++, the vtbl field pointed to an array 134 of structures. Nowadays it points directly to the structure. */ 135 if (value_type (vtbl)->code () == TYPE_CODE_PTR 136 && value_type (vtbl)->target_type ()->code () == TYPE_CODE_ARRAY) 137 { 138 /* Handle the case where the vtbl field points to an 139 array of structures. */ 140 vtbl = value_ind (vtbl); 141 142 /* Index into the virtual function table. This is hard-coded because 143 looking up a field is not cheap, and it may be important to save 144 time, e.g. if the user has set a conditional breakpoint calling 145 a virtual function. */ 146 entry = value_subscript (vtbl, vi); 147 } 148 else 149 { 150 /* Handle the case where the vtbl field points directly to a 151 structure. */ 152 vtbl = value_ptradd (vtbl, vi); 153 entry = value_ind (vtbl); 154 } 155 156 entry_type = check_typedef (value_type (entry)); 157 158 if (entry_type->code () == TYPE_CODE_STRUCT) 159 { 160 /* Move the `this' pointer according to the virtual function table. */ 161 set_value_offset (arg1, value_offset (arg1) 162 + value_as_long (value_field (entry, 0))); 163 164 if (!value_lazy (arg1)) 165 { 166 set_value_lazy (arg1, 1); 167 value_fetch_lazy (arg1); 168 } 169 170 vfn = value_field (entry, 2); 171 } 172 else if (entry_type->code () == TYPE_CODE_PTR) 173 vfn = entry; 174 else 175 error (_("I'm confused: virtual function table has bad type")); 176 /* Reinstantiate the function pointer with the correct type. */ 177 deprecated_set_value_type (vfn, 178 lookup_pointer_type (TYPE_FN_FIELD_TYPE (f, j))); 179 180 *arg1p = arg1; 181 return vfn; 182 } 183 184 185 static struct type * 186 gnuv2_value_rtti_type (struct value *v, int *full, LONGEST *top, int *using_enc) 187 { 188 struct type *known_type; 189 struct type *rtti_type; 190 CORE_ADDR vtbl; 191 struct bound_minimal_symbol minsym; 192 char *p; 193 const char *linkage_name; 194 struct type *btype; 195 struct type *known_type_vptr_basetype; 196 int known_type_vptr_fieldno; 197 198 if (full) 199 *full = 0; 200 if (top) 201 *top = -1; 202 if (using_enc) 203 *using_enc = 0; 204 205 /* Get declared type. */ 206 known_type = value_type (v); 207 known_type = check_typedef (known_type); 208 /* RTTI works only or class objects. */ 209 if (known_type->code () != TYPE_CODE_STRUCT) 210 return NULL; 211 212 /* Plan on this changing in the future as i get around to setting 213 the vtables properly for G++ compiled stuff. Also, I'll be using 214 the type info functions, which are always right. Deal with it 215 until then. */ 216 217 /* Try to get the vptr basetype, fieldno. */ 218 known_type_vptr_fieldno = get_vptr_fieldno (known_type, 219 &known_type_vptr_basetype); 220 221 /* If we can't find it, give up. */ 222 if (known_type_vptr_fieldno < 0) 223 return NULL; 224 225 /* Make sure our basetype and known type match, otherwise, cast 226 so we can get at the vtable properly. */ 227 btype = known_type_vptr_basetype; 228 btype = check_typedef (btype); 229 if (btype != known_type ) 230 { 231 v = value_cast (btype, v); 232 if (using_enc) 233 *using_enc=1; 234 } 235 /* We can't use value_ind here, because it would want to use RTTI, and 236 we'd waste a bunch of time figuring out we already know the type. 237 Besides, we don't care about the type, just the actual pointer. */ 238 if (value_address (value_field (v, known_type_vptr_fieldno)) == 0) 239 return NULL; 240 241 vtbl = value_as_address (value_field (v, known_type_vptr_fieldno)); 242 243 /* Try to find a symbol that is the vtable. */ 244 minsym=lookup_minimal_symbol_by_pc(vtbl); 245 if (minsym.minsym==NULL 246 || (linkage_name=minsym.minsym->linkage_name ())==NULL 247 || !is_vtable_name (linkage_name)) 248 return NULL; 249 250 /* If we just skip the prefix, we get screwed by namespaces. */ 251 gdb::unique_xmalloc_ptr<char> demangled_name 252 = gdb_demangle(linkage_name,DMGL_PARAMS|DMGL_ANSI); 253 p = strchr (demangled_name.get (), ' '); 254 if (p) 255 *p = '\0'; 256 257 /* Lookup the type for the name. */ 258 /* FIXME: chastain/2003-11-26: block=NULL is bogus. See pr gdb/1465. */ 259 rtti_type = cp_lookup_rtti_type (demangled_name.get (), NULL); 260 if (rtti_type == NULL) 261 return NULL; 262 263 if (TYPE_N_BASECLASSES(rtti_type) > 1 && full && (*full) != 1) 264 { 265 if (top) 266 *top = TYPE_BASECLASS_BITPOS (rtti_type, 267 TYPE_VPTR_FIELDNO(rtti_type)) / 8; 268 if (top && ((*top) >0)) 269 { 270 if (rtti_type->length () > known_type->length ()) 271 { 272 if (full) 273 *full=0; 274 } 275 else 276 { 277 if (full) 278 *full=1; 279 } 280 } 281 } 282 else 283 { 284 if (full) 285 *full=1; 286 } 287 288 return rtti_type; 289 } 290 291 /* Return true if the INDEXth field of TYPE is a virtual baseclass 292 pointer which is for the base class whose type is BASECLASS. */ 293 294 static int 295 vb_match (struct type *type, int index, struct type *basetype) 296 { 297 struct type *fieldtype; 298 const char *name = type->field (index).name (); 299 const char *field_class_name = NULL; 300 301 if (*name != '_') 302 return 0; 303 /* gcc 2.4 uses _vb$. */ 304 if (name[1] == 'v' && name[2] == 'b' && is_cplus_marker (name[3])) 305 field_class_name = name + 4; 306 /* gcc 2.5 will use __vb_. */ 307 if (name[1] == '_' && name[2] == 'v' && name[3] == 'b' && name[4] == '_') 308 field_class_name = name + 5; 309 310 if (field_class_name == NULL) 311 /* This field is not a virtual base class pointer. */ 312 return 0; 313 314 /* It's a virtual baseclass pointer, now we just need to find out whether 315 it is for this baseclass. */ 316 fieldtype = type->field (index).type (); 317 if (fieldtype == NULL 318 || fieldtype->code () != TYPE_CODE_PTR) 319 /* "Can't happen". */ 320 return 0; 321 322 /* What we check for is that either the types are equal (needed for 323 nameless types) or have the same name. This is ugly, and a more 324 elegant solution should be devised (which would probably just push 325 the ugliness into symbol reading unless we change the stabs format). */ 326 if (fieldtype->target_type () == basetype) 327 return 1; 328 329 if (basetype->name () != NULL 330 && fieldtype->target_type ()->name () != NULL 331 && strcmp (basetype->name (), 332 fieldtype->target_type ()->name ()) == 0) 333 return 1; 334 return 0; 335 } 336 337 /* Compute the offset of the baseclass which is the INDEXth baseclass 338 of class TYPE, for value at VALADDR (in host) at ADDRESS (in 339 target). The result is the offset of the baseclass value relative 340 to (the address of)(ARG) + OFFSET. */ 341 342 static int 343 gnuv2_baseclass_offset (struct type *type, int index, 344 const bfd_byte *valaddr, LONGEST embedded_offset, 345 CORE_ADDR address, const struct value *val) 346 { 347 struct type *basetype = TYPE_BASECLASS (type, index); 348 349 if (BASETYPE_VIA_VIRTUAL (type, index)) 350 { 351 /* Must hunt for the pointer to this virtual baseclass. */ 352 int i, len = type->num_fields (); 353 int n_baseclasses = TYPE_N_BASECLASSES (type); 354 355 /* First look for the virtual baseclass pointer 356 in the fields. */ 357 for (i = n_baseclasses; i < len; i++) 358 { 359 if (vb_match (type, i, basetype)) 360 { 361 struct type *field_type; 362 LONGEST field_offset; 363 int field_length; 364 CORE_ADDR addr; 365 366 field_type = check_typedef (type->field (i).type ()); 367 field_offset = type->field (i).loc_bitpos () / 8; 368 field_length = field_type->length (); 369 370 if (!value_bytes_available (val, embedded_offset + field_offset, 371 field_length)) 372 throw_error (NOT_AVAILABLE_ERROR, 373 _("Virtual baseclass pointer is not available")); 374 375 addr = unpack_pointer (field_type, 376 valaddr + embedded_offset + field_offset); 377 378 return addr - (LONGEST) address + embedded_offset; 379 } 380 } 381 /* Not in the fields, so try looking through the baseclasses. */ 382 for (i = index + 1; i < n_baseclasses; i++) 383 { 384 /* Don't go through baseclass_offset, as that wraps 385 exceptions, thus, inner exceptions would be wrapped more 386 than once. */ 387 int boffset = 388 gnuv2_baseclass_offset (type, i, valaddr, 389 embedded_offset, address, val); 390 391 if (boffset) 392 return boffset; 393 } 394 395 error (_("Baseclass offset not found")); 396 } 397 398 /* Baseclass is easily computed. */ 399 return TYPE_BASECLASS_BITPOS (type, index) / 8; 400 } 401 402 static void 403 init_gnuv2_ops (void) 404 { 405 gnu_v2_abi_ops.shortname = "gnu-v2"; 406 gnu_v2_abi_ops.longname = "GNU G++ Version 2 ABI"; 407 gnu_v2_abi_ops.doc = "G++ Version 2 ABI"; 408 gnu_v2_abi_ops.is_destructor_name = gnuv2_is_destructor_name; 409 gnu_v2_abi_ops.is_constructor_name = gnuv2_is_constructor_name; 410 gnu_v2_abi_ops.is_vtable_name = gnuv2_is_vtable_name; 411 gnu_v2_abi_ops.is_operator_name = gnuv2_is_operator_name; 412 gnu_v2_abi_ops.virtual_fn_field = gnuv2_virtual_fn_field; 413 gnu_v2_abi_ops.rtti_type = gnuv2_value_rtti_type; 414 gnu_v2_abi_ops.baseclass_offset = gnuv2_baseclass_offset; 415 } 416 417 void _initialize_gnu_v2_abi (); 418 void 419 _initialize_gnu_v2_abi () 420 { 421 init_gnuv2_ops (); 422 register_cp_abi (&gnu_v2_abi_ops); 423 } 424