gdb/gnu-v2-abi.c

   1 /* Abstraction of GNU v2 abi.
   2
   3    Copyright 2001, 2002, 2003 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
  10    modify
  11    it under the terms of the GNU General Public License as published
  12    by
  13    the Free Software Foundation; either version 2 of the License, or
  14    (at your option) any later version.
  15
  16    This program is distributed in the hope that it will be useful,
  17    but WITHOUT ANY WARRANTY; without even the implied warranty of
  18    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  19    GNU General Public License for more details.
  20
  21    You should have received a copy of the GNU General Public License
  22    along with this program; if not, write to the Free Software
  23    Foundation, Inc., 59 Temple Place - Suite 330,
  24    Boston, MA 02111-1307, USA.  */
  25
  26 #include "defs.h"
  27 #include "gdb_string.h"
  28 #include "symtab.h"
  29 #include "gdbtypes.h"
  30 #include "value.h"
  31 #include "demangle.h"
  32 #include "cp-abi.h"
  33 #include "cp-support.h"
  34
  35 #include <ctype.h>
  36
  37 struct cp_abi_ops gnu_v2_abi_ops;
  38
  39 static int vb_match (struct type *, int, struct type *);
  40 int gnuv2_baseclass_offset (struct type *type, int index, char *valaddr,
  41                             CORE_ADDR address);
  42
  43 static enum dtor_kinds
  44 gnuv2_is_destructor_name (const char *name)
  45 {
  46   if ((name[0] == '_' && is_cplus_marker (name[1]) && name[2] == '_')
  47       || strncmp (name, "__dt__", 6) == 0)
  48     return complete_object_dtor;
  49   else
  50     return 0;
  51 }
  52
  53 static enum ctor_kinds
  54 gnuv2_is_constructor_name (const char *name)
  55 {
  56   if ((name[0] == '_' && name[1] == '_'
  57        && (isdigit (name[2]) || strchr ("Qt", name[2])))
  58       || strncmp (name, "__ct__", 6) == 0)
  59     return complete_object_ctor;
  60   else
  61     return 0;
  62 }
  63
  64 static int
  65 gnuv2_is_vtable_name (const char *name)
  66 {
  67   return (((name)[0] == '_'
  68            && (((name)[1] == 'V' && (name)[2] == 'T')
  69                || ((name)[1] == 'v' && (name)[2] == 't'))
  70            && is_cplus_marker ((name)[3])) ||
  71           ((name)[0] == '_' && (name)[1] == '_'
  72            && (name)[2] == 'v' && (name)[3] == 't' && (name)[4] == '_'));
  73 }
  74
  75 static int
  76 gnuv2_is_operator_name (const char *name)
  77 {
  78   return strncmp (name, "operator", 8) == 0;
  79 }
  80
  81 \f
  82 /* Return a virtual function as a value.
  83    ARG1 is the object which provides the virtual function
  84    table pointer.  *ARG1P is side-effected in calling this function.
  85    F is the list of member functions which contains the desired virtual
  86    function.
  87    J is an index into F which provides the desired virtual function.
  88
  89    TYPE is the type in which F is located.  */
  90 static struct value *
  91 gnuv2_virtual_fn_field (struct value **arg1p, struct fn_field * f, int j,
  92                         struct type * type, int offset)
  93 {
  94   struct value *arg1 = *arg1p;
  95   struct type *type1 = check_typedef (VALUE_TYPE (arg1));
  96
  97
  98   struct type *entry_type;
  99   /* First, get the virtual function table pointer.  That comes
 100      with a strange type, so cast it to type `pointer to long' (which
 101      should serve just fine as a function type).  Then, index into
 102      the table, and convert final value to appropriate function type.  */
 103   struct value *entry;
 104   struct value *vfn;
 105   struct value *vtbl;
 106   struct value *vi = value_from_longest (builtin_type_int,
 107                                      (LONGEST) TYPE_FN_FIELD_VOFFSET (f, j));
 108   struct type *fcontext = TYPE_FN_FIELD_FCONTEXT (f, j);
 109   struct type *context;
 110   if (fcontext == NULL)
 111     /* We don't have an fcontext (e.g. the program was compiled with
 112        g++ version 1).  Try to get the vtbl from the TYPE_VPTR_BASETYPE.
 113        This won't work right for multiple inheritance, but at least we
 114        should do as well as GDB 3.x did.  */
 115     fcontext = TYPE_VPTR_BASETYPE (type);
 116   context = lookup_pointer_type (fcontext);
 117   /* Now context is a pointer to the basetype containing the vtbl.  */
 118   if (TYPE_TARGET_TYPE (context) != type1)
 119     {
 120       struct value *tmp = value_cast (context, value_addr (arg1));
 121       arg1 = value_ind (tmp);
 122       type1 = check_typedef (VALUE_TYPE (arg1));
 123     }
 124
 125   context = type1;
 126   /* Now context is the basetype containing the vtbl.  */
 127
 128   /* This type may have been defined before its virtual function table
 129      was.  If so, fill in the virtual function table entry for the
 130      type now.  */
 131   if (TYPE_VPTR_FIELDNO (context) < 0)
 132     fill_in_vptr_fieldno (context);
 133
 134   /* The virtual function table is now an array of structures
 135      which have the form { int16 offset, delta; void *pfn; }.  */
 136   vtbl = value_primitive_field (arg1, 0, TYPE_VPTR_FIELDNO (context),
 137                                 TYPE_VPTR_BASETYPE (context));
 138
 139   /* With older versions of g++, the vtbl field pointed to an array
 140      of structures.  Nowadays it points directly to the structure. */
 141   if (TYPE_CODE (VALUE_TYPE (vtbl)) == TYPE_CODE_PTR
 142       && TYPE_CODE (TYPE_TARGET_TYPE (VALUE_TYPE (vtbl))) == TYPE_CODE_ARRAY)
 143     {
 144       /* Handle the case where the vtbl field points to an
 145          array of structures. */
 146       vtbl = value_ind (vtbl);
 147
 148       /* Index into the virtual function table.  This is hard-coded because
 149          looking up a field is not cheap, and it may be important to save
 150          time, e.g. if the user has set a conditional breakpoint calling
 151          a virtual function.  */
 152       entry = value_subscript (vtbl, vi);
 153     }
 154   else
 155     {
 156       /* Handle the case where the vtbl field points directly to a structure. */
 157       vtbl = value_add (vtbl, vi);
 158       entry = value_ind (vtbl);
 159     }
 160
 161   entry_type = check_typedef (VALUE_TYPE (entry));
 162
 163   if (TYPE_CODE (entry_type) == TYPE_CODE_STRUCT)
 164     {
 165       /* Move the `this' pointer according to the virtual function table. */
 166       VALUE_OFFSET (arg1) += value_as_long (value_field (entry, 0));
 167
 168       if (!VALUE_LAZY (arg1))
 169         {
 170           VALUE_LAZY (arg1) = 1;
 171           value_fetch_lazy (arg1);
 172         }
 173
 174       vfn = value_field (entry, 2);
 175     }
 176   else if (TYPE_CODE (entry_type) == TYPE_CODE_PTR)
 177     vfn = entry;
 178   else
 179     error ("I'm confused:  virtual function table has bad type");
 180   /* Reinstantiate the function pointer with the correct type.  */
 181   VALUE_TYPE (vfn) = lookup_pointer_type (TYPE_FN_FIELD_TYPE (f, j));
 182
 183   *arg1p = arg1;
 184   return vfn;
 185 }
 186
 187
 188 static struct type *
 189 gnuv2_value_rtti_type (struct value *v, int *full, int *top, int *using_enc)
 190 {
 191   struct type *known_type;
 192   struct type *rtti_type;
 193   CORE_ADDR coreptr;
 194   struct value *vp;
 195   long top_offset = 0;
 196   char rtti_type_name[256];
 197   CORE_ADDR vtbl;
 198   struct minimal_symbol *minsym;
 199   struct symbol *sym;
 200   char *demangled_name;
 201   struct type *btype;
 202
 203   if (full)
 204     *full = 0;
 205   if (top)
 206     *top = -1;
 207   if (using_enc)
 208     *using_enc = 0;
 209
 210   /* Get declared type */
 211   known_type = VALUE_TYPE (v);
 212   CHECK_TYPEDEF (known_type);
 213   /* RTTI works only or class objects */
 214   if (TYPE_CODE (known_type) != TYPE_CODE_CLASS)
 215     return NULL;
 216
 217   /* Plan on this changing in the future as i get around to setting
 218      the vtables properly for G++ compiled stuff.  Also, I'll be using
 219      the type info functions, which are always right.  Deal with it
 220      until then.  */
 221
 222   /* If the type has no vptr fieldno, try to get it filled in */
 223   if (TYPE_VPTR_FIELDNO(known_type) < 0)
 224     fill_in_vptr_fieldno(known_type);
 225
 226   /* If we still can't find one, give up */
 227   if (TYPE_VPTR_FIELDNO(known_type) < 0)
 228     return NULL;
 229
 230   /* Make sure our basetype and known type match, otherwise, cast
 231      so we can get at the vtable properly.
 232   */
 233   btype = TYPE_VPTR_BASETYPE (known_type);
 234   CHECK_TYPEDEF (btype);
 235   if (btype != known_type )
 236     {
 237       v = value_cast (btype, v);
 238       if (using_enc)
 239         *using_enc=1;
 240     }
 241   /*
 242     We can't use value_ind here, because it would want to use RTTI, and
 243     we'd waste a bunch of time figuring out we already know the type.
 244     Besides, we don't care about the type, just the actual pointer
 245   */
 246   if (VALUE_ADDRESS (value_field (v, TYPE_VPTR_FIELDNO (known_type))) == 0)
 247     return NULL;
 248
 249   vtbl=value_as_address(value_field(v,TYPE_VPTR_FIELDNO(known_type)));
 250
 251   /* Try to find a symbol that is the vtable */
 252   minsym=lookup_minimal_symbol_by_pc(vtbl);
 253   if (minsym==NULL
 254       || (demangled_name=DEPRECATED_SYMBOL_NAME (minsym))==NULL
 255       || !is_vtable_name (demangled_name))
 256     return NULL;
 257
 258   /* If we just skip the prefix, we get screwed by namespaces */
 259   demangled_name=cplus_demangle(demangled_name,DMGL_PARAMS|DMGL_ANSI);
 260   *(strchr(demangled_name,' '))=0;
 261
 262   /* Lookup the type for the name */
 263   /* FIXME: chastain/2003-11-26: block=NULL is bogus.  See pr gdb/1465. */
 264   rtti_type = cp_lookup_rtti_type (demangled_name, NULL);
 265   if (rtti_type == NULL)
 266     return NULL;
 267
 268   if (TYPE_N_BASECLASSES(rtti_type) > 1 &&  full && (*full) != 1)
 269     {
 270       if (top)
 271         *top=TYPE_BASECLASS_BITPOS(rtti_type,TYPE_VPTR_FIELDNO(rtti_type))/8;
 272       if (top && ((*top) >0))
 273         {
 274           if (TYPE_LENGTH(rtti_type) > TYPE_LENGTH(known_type))
 275             {
 276               if (full)
 277                 *full=0;
 278             }
 279           else
 280             {
 281               if (full)
 282                 *full=1;
 283             }
 284         }
 285     }
 286   else
 287     {
 288       if (full)
 289         *full=1;
 290     }
 291
 292   return rtti_type;
 293 }
 294
 295 /* Return true if the INDEXth field of TYPE is a virtual baseclass
 296    pointer which is for the base class whose type is BASECLASS.  */
 297
 298 static int
 299 vb_match (struct type *type, int index, struct type *basetype)
 300 {
 301   struct type *fieldtype;
 302   char *name = TYPE_FIELD_NAME (type, index);
 303   char *field_class_name = NULL;
 304
 305   if (*name != '_')
 306     return 0;
 307   /* gcc 2.4 uses _vb$.  */
 308   if (name[1] == 'v' && name[2] == 'b' && is_cplus_marker (name[3]))
 309     field_class_name = name + 4;
 310   /* gcc 2.5 will use __vb_.  */
 311   if (name[1] == '_' && name[2] == 'v' && name[3] == 'b' && name[4] == '_')
 312     field_class_name = name + 5;
 313
 314   if (field_class_name == NULL)
 315     /* This field is not a virtual base class pointer.  */
 316     return 0;
 317
 318   /* It's a virtual baseclass pointer, now we just need to find out whether
 319      it is for this baseclass.  */
 320   fieldtype = TYPE_FIELD_TYPE (type, index);
 321   if (fieldtype == NULL
 322       || TYPE_CODE (fieldtype) != TYPE_CODE_PTR)
 323     /* "Can't happen".  */
 324     return 0;
 325
 326   /* What we check for is that either the types are equal (needed for
 327      nameless types) or have the same name.  This is ugly, and a more
 328      elegant solution should be devised (which would probably just push
 329      the ugliness into symbol reading unless we change the stabs format).  */
 330   if (TYPE_TARGET_TYPE (fieldtype) == basetype)
 331     return 1;
 332
 333   if (TYPE_NAME (basetype) != NULL
 334       && TYPE_NAME (TYPE_TARGET_TYPE (fieldtype)) != NULL
 335       && strcmp (TYPE_NAME (basetype),
 336                  TYPE_NAME (TYPE_TARGET_TYPE (fieldtype))) == 0)
 337     return 1;
 338   return 0;
 339 }
 340
 341 /* Compute the offset of the baseclass which is
 342    the INDEXth baseclass of class TYPE,
 343    for value at VALADDR (in host) at ADDRESS (in target).
 344    The result is the offset of the baseclass value relative
 345    to (the address of)(ARG) + OFFSET.
 346
 347    -1 is returned on error. */
 348
 349 int
 350 gnuv2_baseclass_offset (struct type *type, int index, char *valaddr,
 351                   CORE_ADDR address)
 352 {
 353   struct type *basetype = TYPE_BASECLASS (type, index);
 354
 355   if (BASETYPE_VIA_VIRTUAL (type, index))
 356     {
 357       /* Must hunt for the pointer to this virtual baseclass.  */
 358       int i, len = TYPE_NFIELDS (type);
 359       int n_baseclasses = TYPE_N_BASECLASSES (type);
 360
 361       /* First look for the virtual baseclass pointer
 362          in the fields.  */
 363       for (i = n_baseclasses; i < len; i++)
 364         {
 365           if (vb_match (type, i, basetype))
 366             {
 367               CORE_ADDR addr
 368               = unpack_pointer (TYPE_FIELD_TYPE (type, i),
 369                                 valaddr + (TYPE_FIELD_BITPOS (type, i) / 8));
 370
 371               return addr - (LONGEST) address;
 372             }
 373         }
 374       /* Not in the fields, so try looking through the baseclasses.  */
 375       for (i = index + 1; i < n_baseclasses; i++)
 376         {
 377           int boffset =
 378           baseclass_offset (type, i, valaddr, address);
 379           if (boffset)
 380             return boffset;
 381         }
 382       /* Not found.  */
 383       return -1;
 384     }
 385
 386   /* Baseclass is easily computed.  */
 387   return TYPE_BASECLASS_BITPOS (type, index) / 8;
 388 }
 389
 390 static void
 391 init_gnuv2_ops (void)
 392 {
 393   gnu_v2_abi_ops.shortname = "gnu-v2";
 394   gnu_v2_abi_ops.longname = "GNU G++ Version 2 ABI";
 395   gnu_v2_abi_ops.doc = "G++ Version 2 ABI";
 396   gnu_v2_abi_ops.is_destructor_name = gnuv2_is_destructor_name;
 397   gnu_v2_abi_ops.is_constructor_name = gnuv2_is_constructor_name;
 398   gnu_v2_abi_ops.is_vtable_name = gnuv2_is_vtable_name;
 399   gnu_v2_abi_ops.is_operator_name = gnuv2_is_operator_name;
 400   gnu_v2_abi_ops.virtual_fn_field = gnuv2_virtual_fn_field;
 401   gnu_v2_abi_ops.rtti_type = gnuv2_value_rtti_type;
 402   gnu_v2_abi_ops.baseclass_offset = gnuv2_baseclass_offset;
 403 }
 404
 405 extern initialize_file_ftype _initialize_gnu_v2_abi; /* -Wmissing-prototypes */
 406
 407 void
 408 _initialize_gnu_v2_abi (void)
 409 {
 410   init_gnuv2_ops ();
 411   register_cp_abi (&gnu_v2_abi_ops);
 412   set_cp_abi_as_auto_default (gnu_v2_abi_ops.shortname);
 413 }