gdb/gnu-v2-abi.c

   1 /* Abstraction of GNU v2 abi.
   2
   3    Copyright (C) 2001, 2002, 2003, 2005, 2007 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 "gdb_string.h"
  24 #include "symtab.h"
  25 #include "gdbtypes.h"
  26 #include "value.h"
  27 #include "demangle.h"
  28 #include "cp-abi.h"
  29 #include "cp-support.h"
  30 #include "gnu-v2-abi.h"
  31
  32 #include <ctype.h>
  33
  34 struct cp_abi_ops gnu_v2_abi_ops;
  35
  36 static int vb_match (struct type *, int, struct type *);
  37
  38 static enum dtor_kinds
  39 gnuv2_is_destructor_name (const char *name)
  40 {
  41   if ((name[0] == '_' && is_cplus_marker (name[1]) && name[2] == '_')
  42       || strncmp (name, "__dt__", 6) == 0)
  43     return complete_object_dtor;
  44   else
  45     return 0;
  46 }
  47
  48 static enum ctor_kinds
  49 gnuv2_is_constructor_name (const char *name)
  50 {
  51   if ((name[0] == '_' && name[1] == '_'
  52        && (isdigit (name[2]) || strchr ("Qt", name[2])))
  53       || strncmp (name, "__ct__", 6) == 0)
  54     return complete_object_ctor;
  55   else
  56     return 0;
  57 }
  58
  59 static int
  60 gnuv2_is_vtable_name (const char *name)
  61 {
  62   return (((name)[0] == '_'
  63            && (((name)[1] == 'V' && (name)[2] == 'T')
  64                || ((name)[1] == 'v' && (name)[2] == 't'))
  65            && is_cplus_marker ((name)[3])) ||
  66           ((name)[0] == '_' && (name)[1] == '_'
  67            && (name)[2] == 'v' && (name)[3] == 't' && (name)[4] == '_'));
  68 }
  69
  70 static int
  71 gnuv2_is_operator_name (const char *name)
  72 {
  73   return strncmp (name, "operator", 8) == 0;
  74 }
  75
  76 \f
  77 /* Return a virtual function as a value.
  78    ARG1 is the object which provides the virtual function
  79    table pointer.  *ARG1P is side-effected in calling this function.
  80    F is the list of member functions which contains the desired virtual
  81    function.
  82    J is an index into F which provides the desired virtual function.
  83
  84    TYPE is the type in which F is located.  */
  85 static struct value *
  86 gnuv2_virtual_fn_field (struct value **arg1p, struct fn_field * f, int j,
  87                         struct type * type, int offset)
  88 {
  89   struct value *arg1 = *arg1p;
  90   struct type *type1 = check_typedef (value_type (arg1));
  91
  92
  93   struct type *entry_type;
  94   /* First, get the virtual function table pointer.  That comes
  95      with a strange type, so cast it to type `pointer to long' (which
  96      should serve just fine as a function type).  Then, index into
  97      the table, and convert final value to appropriate function type.  */
  98   struct value *entry;
  99   struct value *vfn;
 100   struct value *vtbl;
 101   struct value *vi = value_from_longest (builtin_type_int,
 102                                      (LONGEST) TYPE_FN_FIELD_VOFFSET (f, j));
 103   struct type *fcontext = TYPE_FN_FIELD_FCONTEXT (f, j);
 104   struct type *context;
 105   if (fcontext == NULL)
 106     /* We don't have an fcontext (e.g. the program was compiled with
 107        g++ version 1).  Try to get the vtbl from the TYPE_VPTR_BASETYPE.
 108        This won't work right for multiple inheritance, but at least we
 109        should do as well as GDB 3.x did.  */
 110     fcontext = TYPE_VPTR_BASETYPE (type);
 111   context = lookup_pointer_type (fcontext);
 112   /* Now context is a pointer to the basetype containing the vtbl.  */
 113   if (TYPE_TARGET_TYPE (context) != type1)
 114     {
 115       struct value *tmp = value_cast (context, value_addr (arg1));
 116       arg1 = value_ind (tmp);
 117       type1 = check_typedef (value_type (arg1));
 118     }
 119
 120   context = type1;
 121   /* Now context is the basetype containing the vtbl.  */
 122
 123   /* This type may have been defined before its virtual function table
 124      was.  If so, fill in the virtual function table entry for the
 125      type now.  */
 126   if (TYPE_VPTR_FIELDNO (context) < 0)
 127     fill_in_vptr_fieldno (context);
 128
 129   /* The virtual function table is now an array of structures
 130      which have the form { int16 offset, delta; void *pfn; }.  */
 131   vtbl = value_primitive_field (arg1, 0, TYPE_VPTR_FIELDNO (context),
 132                                 TYPE_VPTR_BASETYPE (context));
 133
 134   /* With older versions of g++, the vtbl field pointed to an array
 135      of structures.  Nowadays it points directly to the structure. */
 136   if (TYPE_CODE (value_type (vtbl)) == TYPE_CODE_PTR
 137       && TYPE_CODE (TYPE_TARGET_TYPE (value_type (vtbl))) == TYPE_CODE_ARRAY)
 138     {
 139       /* Handle the case where the vtbl field points to an
 140          array of structures. */
 141       vtbl = value_ind (vtbl);
 142
 143       /* Index into the virtual function table.  This is hard-coded because
 144          looking up a field is not cheap, and it may be important to save
 145          time, e.g. if the user has set a conditional breakpoint calling
 146          a virtual function.  */
 147       entry = value_subscript (vtbl, vi);
 148     }
 149   else
 150     {
 151       /* Handle the case where the vtbl field points directly to a structure. */
 152       vtbl = value_add (vtbl, vi);
 153       entry = value_ind (vtbl);
 154     }
 155
 156   entry_type = check_typedef (value_type (entry));
 157
 158   if (TYPE_CODE (entry_type) == TYPE_CODE_STRUCT)
 159     {
 160       /* Move the `this' pointer according to the virtual function table. */
 161       set_value_offset (arg1, value_offset (arg1) + value_as_long (value_field (entry, 0)));
 162
 163       if (!value_lazy (arg1))
 164         {
 165           set_value_lazy (arg1, 1);
 166           value_fetch_lazy (arg1);
 167         }
 168
 169       vfn = value_field (entry, 2);
 170     }
 171   else if (TYPE_CODE (entry_type) == TYPE_CODE_PTR)
 172     vfn = entry;
 173   else
 174     error (_("I'm confused:  virtual function table has bad type"));
 175   /* Reinstantiate the function pointer with the correct type.  */
 176   deprecated_set_value_type (vfn, lookup_pointer_type (TYPE_FN_FIELD_TYPE (f, j)));
 177
 178   *arg1p = arg1;
 179   return vfn;
 180 }
 181
 182
 183 static struct type *
 184 gnuv2_value_rtti_type (struct value *v, int *full, int *top, int *using_enc)
 185 {
 186   struct type *known_type;
 187   struct type *rtti_type;
 188   CORE_ADDR coreptr;
 189   struct value *vp;
 190   long top_offset = 0;
 191   char rtti_type_name[256];
 192   CORE_ADDR vtbl;
 193   struct minimal_symbol *minsym;
 194   struct symbol *sym;
 195   char *demangled_name, *p;
 196   struct type *btype;
 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   CHECK_TYPEDEF (known_type);
 208   /* RTTI works only or class objects */
 209   if (TYPE_CODE (known_type) != TYPE_CODE_CLASS)
 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   /* If the type has no vptr fieldno, try to get it filled in */
 218   if (TYPE_VPTR_FIELDNO(known_type) < 0)
 219     fill_in_vptr_fieldno(known_type);
 220
 221   /* If we still can't find one, give up */
 222   if (TYPE_VPTR_FIELDNO(known_type) < 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   */
 228   btype = TYPE_VPTR_BASETYPE (known_type);
 229   CHECK_TYPEDEF (btype);
 230   if (btype != known_type )
 231     {
 232       v = value_cast (btype, v);
 233       if (using_enc)
 234         *using_enc=1;
 235     }
 236   /*
 237     We can't use value_ind here, because it would want to use RTTI, and
 238     we'd waste a bunch of time figuring out we already know the type.
 239     Besides, we don't care about the type, just the actual pointer
 240   */
 241   if (VALUE_ADDRESS (value_field (v, TYPE_VPTR_FIELDNO (known_type))) == 0)
 242     return NULL;
 243
 244   vtbl=value_as_address(value_field(v,TYPE_VPTR_FIELDNO(known_type)));
 245
 246   /* Try to find a symbol that is the vtable */
 247   minsym=lookup_minimal_symbol_by_pc(vtbl);
 248   if (minsym==NULL
 249       || (demangled_name=DEPRECATED_SYMBOL_NAME (minsym))==NULL
 250       || !is_vtable_name (demangled_name))
 251     return NULL;
 252
 253   /* If we just skip the prefix, we get screwed by namespaces */
 254   demangled_name=cplus_demangle(demangled_name,DMGL_PARAMS|DMGL_ANSI);
 255   p = strchr (demangled_name, ' ');
 256   if (p)
 257     *p = '\0';
 258
 259   /* Lookup the type for the name */
 260   /* FIXME: chastain/2003-11-26: block=NULL is bogus.  See pr gdb/1465. */
 261   rtti_type = cp_lookup_rtti_type (demangled_name, NULL);
 262   if (rtti_type == NULL)
 263     return NULL;
 264
 265   if (TYPE_N_BASECLASSES(rtti_type) > 1 &&  full && (*full) != 1)
 266     {
 267       if (top)
 268         *top=TYPE_BASECLASS_BITPOS(rtti_type,TYPE_VPTR_FIELDNO(rtti_type))/8;
 269       if (top && ((*top) >0))
 270         {
 271           if (TYPE_LENGTH(rtti_type) > TYPE_LENGTH(known_type))
 272             {
 273               if (full)
 274                 *full=0;
 275             }
 276           else
 277             {
 278               if (full)
 279                 *full=1;
 280             }
 281         }
 282     }
 283   else
 284     {
 285       if (full)
 286         *full=1;
 287     }
 288
 289   return rtti_type;
 290 }
 291
 292 /* Return true if the INDEXth field of TYPE is a virtual baseclass
 293    pointer which is for the base class whose type is BASECLASS.  */
 294
 295 static int
 296 vb_match (struct type *type, int index, struct type *basetype)
 297 {
 298   struct type *fieldtype;
 299   char *name = TYPE_FIELD_NAME (type, index);
 300   char *field_class_name = NULL;
 301
 302   if (*name != '_')
 303     return 0;
 304   /* gcc 2.4 uses _vb$.  */
 305   if (name[1] == 'v' && name[2] == 'b' && is_cplus_marker (name[3]))
 306     field_class_name = name + 4;
 307   /* gcc 2.5 will use __vb_.  */
 308   if (name[1] == '_' && name[2] == 'v' && name[3] == 'b' && name[4] == '_')
 309     field_class_name = name + 5;
 310
 311   if (field_class_name == NULL)
 312     /* This field is not a virtual base class pointer.  */
 313     return 0;
 314
 315   /* It's a virtual baseclass pointer, now we just need to find out whether
 316      it is for this baseclass.  */
 317   fieldtype = TYPE_FIELD_TYPE (type, index);
 318   if (fieldtype == NULL
 319       || TYPE_CODE (fieldtype) != TYPE_CODE_PTR)
 320     /* "Can't happen".  */
 321     return 0;
 322
 323   /* What we check for is that either the types are equal (needed for
 324      nameless types) or have the same name.  This is ugly, and a more
 325      elegant solution should be devised (which would probably just push
 326      the ugliness into symbol reading unless we change the stabs format).  */
 327   if (TYPE_TARGET_TYPE (fieldtype) == basetype)
 328     return 1;
 329
 330   if (TYPE_NAME (basetype) != NULL
 331       && TYPE_NAME (TYPE_TARGET_TYPE (fieldtype)) != NULL
 332       && strcmp (TYPE_NAME (basetype),
 333                  TYPE_NAME (TYPE_TARGET_TYPE (fieldtype))) == 0)
 334     return 1;
 335   return 0;
 336 }
 337
 338 /* Compute the offset of the baseclass which is
 339    the INDEXth baseclass of class TYPE,
 340    for value at VALADDR (in host) at ADDRESS (in target).
 341    The result is the offset of the baseclass value relative
 342    to (the address of)(ARG) + OFFSET.
 343
 344    -1 is returned on error. */
 345
 346 int
 347 gnuv2_baseclass_offset (struct type *type, int index,
 348                         const bfd_byte *valaddr, CORE_ADDR address)
 349 {
 350   struct type *basetype = TYPE_BASECLASS (type, index);
 351
 352   if (BASETYPE_VIA_VIRTUAL (type, index))
 353     {
 354       /* Must hunt for the pointer to this virtual baseclass.  */
 355       int i, len = TYPE_NFIELDS (type);
 356       int n_baseclasses = TYPE_N_BASECLASSES (type);
 357
 358       /* First look for the virtual baseclass pointer
 359          in the fields.  */
 360       for (i = n_baseclasses; i < len; i++)
 361         {
 362           if (vb_match (type, i, basetype))
 363             {
 364               CORE_ADDR addr
 365               = unpack_pointer (TYPE_FIELD_TYPE (type, i),
 366                                 valaddr + (TYPE_FIELD_BITPOS (type, i) / 8));
 367
 368               return addr - (LONGEST) address;
 369             }
 370         }
 371       /* Not in the fields, so try looking through the baseclasses.  */
 372       for (i = index + 1; i < n_baseclasses; i++)
 373         {
 374           int boffset =
 375           baseclass_offset (type, i, valaddr, address);
 376           if (boffset)
 377             return boffset;
 378         }
 379       /* Not found.  */
 380       return -1;
 381     }
 382
 383   /* Baseclass is easily computed.  */
 384   return TYPE_BASECLASS_BITPOS (type, index) / 8;
 385 }
 386
 387 static void
 388 init_gnuv2_ops (void)
 389 {
 390   gnu_v2_abi_ops.shortname = "gnu-v2";
 391   gnu_v2_abi_ops.longname = "GNU G++ Version 2 ABI";
 392   gnu_v2_abi_ops.doc = "G++ Version 2 ABI";
 393   gnu_v2_abi_ops.is_destructor_name = gnuv2_is_destructor_name;
 394   gnu_v2_abi_ops.is_constructor_name = gnuv2_is_constructor_name;
 395   gnu_v2_abi_ops.is_vtable_name = gnuv2_is_vtable_name;
 396   gnu_v2_abi_ops.is_operator_name = gnuv2_is_operator_name;
 397   gnu_v2_abi_ops.virtual_fn_field = gnuv2_virtual_fn_field;
 398   gnu_v2_abi_ops.rtti_type = gnuv2_value_rtti_type;
 399   gnu_v2_abi_ops.baseclass_offset = gnuv2_baseclass_offset;
 400 }
 401
 402 extern initialize_file_ftype _initialize_gnu_v2_abi; /* -Wmissing-prototypes */
 403
 404 void
 405 _initialize_gnu_v2_abi (void)
 406 {
 407   init_gnuv2_ops ();
 408   register_cp_abi (&gnu_v2_abi_ops);
 409   set_cp_abi_as_auto_default (gnu_v2_abi_ops.shortname);
 410 }