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
  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., 51 Franklin Street, Fifth Floor,
  24    Boston, MA 02110-1301, 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 #include "gnu-v2-abi.h"
  35
  36 #include <ctype.h>
  37
  38 struct cp_abi_ops gnu_v2_abi_ops;
  39
  40 static int vb_match (struct type *, int, struct type *);
  41
  42 static enum dtor_kinds
  43 gnuv2_is_destructor_name (const char *name)
  44 {
  45   if ((name[0] == '_' && is_cplus_marker (name[1]) && name[2] == '_')
  46       || strncmp (name, "__dt__", 6) == 0)
  47     return complete_object_dtor;
  48   else
  49     return 0;
  50 }
  51
  52 static enum ctor_kinds
  53 gnuv2_is_constructor_name (const char *name)
  54 {
  55   if ((name[0] == '_' && name[1] == '_'
  56        && (isdigit (name[2]) || strchr ("Qt", name[2])))
  57       || strncmp (name, "__ct__", 6) == 0)
  58     return complete_object_ctor;
  59   else
  60     return 0;
  61 }
  62
  63 static int
  64 gnuv2_is_vtable_name (const char *name)
  65 {
  66   return (((name)[0] == '_'
  67            && (((name)[1] == 'V' && (name)[2] == 'T')
  68                || ((name)[1] == 'v' && (name)[2] == 't'))
  69            && is_cplus_marker ((name)[3])) ||
  70           ((name)[0] == '_' && (name)[1] == '_'
  71            && (name)[2] == 'v' && (name)[3] == 't' && (name)[4] == '_'));
  72 }
  73
  74 static int
  75 gnuv2_is_operator_name (const char *name)
  76 {
  77   return strncmp (name, "operator", 8) == 0;
  78 }
  79
  80 \f
  81 /* Return a virtual function as a value.
  82    ARG1 is the object which provides the virtual function
  83    table pointer.  *ARG1P is side-effected in calling this function.
  84    F is the list of member functions which contains the desired virtual
  85    function.
  86    J is an index into F which provides the desired virtual function.
  87
  88    TYPE is the type in which F is located.  */
  89 static struct value *
  90 gnuv2_virtual_fn_field (struct value **arg1p, struct fn_field * f, int j,
  91                         struct type * type, int offset)
  92 {
  93   struct value *arg1 = *arg1p;
  94   struct type *type1 = check_typedef (value_type (arg1));
  95
  96
  97   struct type *entry_type;
  98   /* First, get the virtual function table pointer.  That comes
  99      with a strange type, so cast it to type `pointer to long' (which
 100      should serve just fine as a function type).  Then, index into
 101      the table, and convert final value to appropriate function type.  */
 102   struct value *entry;
 103   struct value *vfn;
 104   struct value *vtbl;
 105   struct value *vi = value_from_longest (builtin_type_int,
 106                                      (LONGEST) TYPE_FN_FIELD_VOFFSET (f, j));
 107   struct type *fcontext = TYPE_FN_FIELD_FCONTEXT (f, j);
 108   struct type *context;
 109   if (fcontext == NULL)
 110     /* We don't have an fcontext (e.g. the program was compiled with
 111        g++ version 1).  Try to get the vtbl from the TYPE_VPTR_BASETYPE.
 112        This won't work right for multiple inheritance, but at least we
 113        should do as well as GDB 3.x did.  */
 114     fcontext = TYPE_VPTR_BASETYPE (type);
 115   context = lookup_pointer_type (fcontext);
 116   /* Now context is a pointer to the basetype containing the vtbl.  */
 117   if (TYPE_TARGET_TYPE (context) != type1)
 118     {
 119       struct value *tmp = value_cast (context, value_addr (arg1));
 120       arg1 = value_ind (tmp);
 121       type1 = check_typedef (value_type (arg1));
 122     }
 123
 124   context = type1;
 125   /* Now context is the basetype containing the vtbl.  */
 126
 127   /* This type may have been defined before its virtual function table
 128      was.  If so, fill in the virtual function table entry for the
 129      type now.  */
 130   if (TYPE_VPTR_FIELDNO (context) < 0)
 131     fill_in_vptr_fieldno (context);
 132
 133   /* The virtual function table is now an array of structures
 134      which have the form { int16 offset, delta; void *pfn; }.  */
 135   vtbl = value_primitive_field (arg1, 0, TYPE_VPTR_FIELDNO (context),
 136                                 TYPE_VPTR_BASETYPE (context));
 137
 138   /* With older versions of g++, the vtbl field pointed to an array
 139      of structures.  Nowadays it points directly to the structure. */
 140   if (TYPE_CODE (value_type (vtbl)) == TYPE_CODE_PTR
 141       && TYPE_CODE (TYPE_TARGET_TYPE (value_type (vtbl))) == TYPE_CODE_ARRAY)
 142     {
 143       /* Handle the case where the vtbl field points to an
 144          array of structures. */
 145       vtbl = value_ind (vtbl);
 146
 147       /* Index into the virtual function table.  This is hard-coded because
 148          looking up a field is not cheap, and it may be important to save
 149          time, e.g. if the user has set a conditional breakpoint calling
 150          a virtual function.  */
 151       entry = value_subscript (vtbl, vi);
 152     }
 153   else
 154     {
 155       /* Handle the case where the vtbl field points directly to a structure. */
 156       vtbl = value_add (vtbl, vi);
 157       entry = value_ind (vtbl);
 158     }
 159
 160   entry_type = check_typedef (value_type (entry));
 161
 162   if (TYPE_CODE (entry_type) == TYPE_CODE_STRUCT)
 163     {
 164       /* Move the `this' pointer according to the virtual function table. */
 165       set_value_offset (arg1, value_offset (arg1) + value_as_long (value_field (entry, 0)));
 166
 167       if (!value_lazy (arg1))
 168         {
 169           set_value_lazy (arg1, 1);
 170           value_fetch_lazy (arg1);
 171         }
 172
 173       vfn = value_field (entry, 2);
 174     }
 175   else if (TYPE_CODE (entry_type) == TYPE_CODE_PTR)
 176     vfn = entry;
 177   else
 178     error (_("I'm confused:  virtual function table has bad type"));
 179   /* Reinstantiate the function pointer with the correct type.  */
 180   deprecated_set_value_type (vfn, lookup_pointer_type (TYPE_FN_FIELD_TYPE (f, j)));
 181
 182   *arg1p = arg1;
 183   return vfn;
 184 }
 185
 186
 187 static struct type *
 188 gnuv2_value_rtti_type (struct value *v, int *full, int *top, int *using_enc)
 189 {
 190   struct type *known_type;
 191   struct type *rtti_type;
 192   CORE_ADDR coreptr;
 193   struct value *vp;
 194   long top_offset = 0;
 195   char rtti_type_name[256];
 196   CORE_ADDR vtbl;
 197   struct minimal_symbol *minsym;
 198   struct symbol *sym;
 199   char *demangled_name;
 200   struct type *btype;
 201
 202   if (full)
 203     *full = 0;
 204   if (top)
 205     *top = -1;
 206   if (using_enc)
 207     *using_enc = 0;
 208
 209   /* Get declared type */
 210   known_type = value_type (v);
 211   CHECK_TYPEDEF (known_type);
 212   /* RTTI works only or class objects */
 213   if (TYPE_CODE (known_type) != TYPE_CODE_CLASS)
 214     return NULL;
 215
 216   /* Plan on this changing in the future as i get around to setting
 217      the vtables properly for G++ compiled stuff.  Also, I'll be using
 218      the type info functions, which are always right.  Deal with it
 219      until then.  */
 220
 221   /* If the type has no vptr fieldno, try to get it filled in */
 222   if (TYPE_VPTR_FIELDNO(known_type) < 0)
 223     fill_in_vptr_fieldno(known_type);
 224
 225   /* If we still can't find one, give up */
 226   if (TYPE_VPTR_FIELDNO(known_type) < 0)
 227     return NULL;
 228
 229   /* Make sure our basetype and known type match, otherwise, cast
 230      so we can get at the vtable properly.
 231   */
 232   btype = TYPE_VPTR_BASETYPE (known_type);
 233   CHECK_TYPEDEF (btype);
 234   if (btype != known_type )
 235     {
 236       v = value_cast (btype, v);
 237       if (using_enc)
 238         *using_enc=1;
 239     }
 240   /*
 241     We can't use value_ind here, because it would want to use RTTI, and
 242     we'd waste a bunch of time figuring out we already know the type.
 243     Besides, we don't care about the type, just the actual pointer
 244   */
 245   if (VALUE_ADDRESS (value_field (v, TYPE_VPTR_FIELDNO (known_type))) == 0)
 246     return NULL;
 247
 248   vtbl=value_as_address(value_field(v,TYPE_VPTR_FIELDNO(known_type)));
 249
 250   /* Try to find a symbol that is the vtable */
 251   minsym=lookup_minimal_symbol_by_pc(vtbl);
 252   if (minsym==NULL
 253       || (demangled_name=DEPRECATED_SYMBOL_NAME (minsym))==NULL
 254       || !is_vtable_name (demangled_name))
 255     return NULL;
 256
 257   /* If we just skip the prefix, we get screwed by namespaces */
 258   demangled_name=cplus_demangle(demangled_name,DMGL_PARAMS|DMGL_ANSI);
 259   *(strchr(demangled_name,' '))=0;
 260
 261   /* Lookup the type for the name */
 262   /* FIXME: chastain/2003-11-26: block=NULL is bogus.  See pr gdb/1465. */
 263   rtti_type = cp_lookup_rtti_type (demangled_name, NULL);
 264   if (rtti_type == NULL)
 265     return NULL;
 266
 267   if (TYPE_N_BASECLASSES(rtti_type) > 1 &&  full && (*full) != 1)
 268     {
 269       if (top)
 270         *top=TYPE_BASECLASS_BITPOS(rtti_type,TYPE_VPTR_FIELDNO(rtti_type))/8;
 271       if (top && ((*top) >0))
 272         {
 273           if (TYPE_LENGTH(rtti_type) > TYPE_LENGTH(known_type))
 274             {
 275               if (full)
 276                 *full=0;
 277             }
 278           else
 279             {
 280               if (full)
 281                 *full=1;
 282             }
 283         }
 284     }
 285   else
 286     {
 287       if (full)
 288         *full=1;
 289     }
 290
 291   return rtti_type;
 292 }
 293
 294 /* Return true if the INDEXth field of TYPE is a virtual baseclass
 295    pointer which is for the base class whose type is BASECLASS.  */
 296
 297 static int
 298 vb_match (struct type *type, int index, struct type *basetype)
 299 {
 300   struct type *fieldtype;
 301   char *name = TYPE_FIELD_NAME (type, index);
 302   char *field_class_name = NULL;
 303
 304   if (*name != '_')
 305     return 0;
 306   /* gcc 2.4 uses _vb$.  */
 307   if (name[1] == 'v' && name[2] == 'b' && is_cplus_marker (name[3]))
 308     field_class_name = name + 4;
 309   /* gcc 2.5 will use __vb_.  */
 310   if (name[1] == '_' && name[2] == 'v' && name[3] == 'b' && name[4] == '_')
 311     field_class_name = name + 5;
 312
 313   if (field_class_name == NULL)
 314     /* This field is not a virtual base class pointer.  */
 315     return 0;
 316
 317   /* It's a virtual baseclass pointer, now we just need to find out whether
 318      it is for this baseclass.  */
 319   fieldtype = TYPE_FIELD_TYPE (type, index);
 320   if (fieldtype == NULL
 321       || TYPE_CODE (fieldtype) != TYPE_CODE_PTR)
 322     /* "Can't happen".  */
 323     return 0;
 324
 325   /* What we check for is that either the types are equal (needed for
 326      nameless types) or have the same name.  This is ugly, and a more
 327      elegant solution should be devised (which would probably just push
 328      the ugliness into symbol reading unless we change the stabs format).  */
 329   if (TYPE_TARGET_TYPE (fieldtype) == basetype)
 330     return 1;
 331
 332   if (TYPE_NAME (basetype) != NULL
 333       && TYPE_NAME (TYPE_TARGET_TYPE (fieldtype)) != NULL
 334       && strcmp (TYPE_NAME (basetype),
 335                  TYPE_NAME (TYPE_TARGET_TYPE (fieldtype))) == 0)
 336     return 1;
 337   return 0;
 338 }
 339
 340 /* Compute the offset of the baseclass which is
 341    the INDEXth baseclass of class TYPE,
 342    for value at VALADDR (in host) at ADDRESS (in target).
 343    The result is the offset of the baseclass value relative
 344    to (the address of)(ARG) + OFFSET.
 345
 346    -1 is returned on error. */
 347
 348 int
 349 gnuv2_baseclass_offset (struct type *type, int index,
 350                         const bfd_byte *valaddr, CORE_ADDR address)
 351 {
 352   struct type *basetype = TYPE_BASECLASS (type, index);
 353
 354   if (BASETYPE_VIA_VIRTUAL (type, index))
 355     {
 356       /* Must hunt for the pointer to this virtual baseclass.  */
 357       int i, len = TYPE_NFIELDS (type);
 358       int n_baseclasses = TYPE_N_BASECLASSES (type);
 359
 360       /* First look for the virtual baseclass pointer
 361          in the fields.  */
 362       for (i = n_baseclasses; i < len; i++)
 363         {
 364           if (vb_match (type, i, basetype))
 365             {
 366               CORE_ADDR addr
 367               = unpack_pointer (TYPE_FIELD_TYPE (type, i),
 368                                 valaddr + (TYPE_FIELD_BITPOS (type, i) / 8));
 369
 370               return addr - (LONGEST) address;
 371             }
 372         }
 373       /* Not in the fields, so try looking through the baseclasses.  */
 374       for (i = index + 1; i < n_baseclasses; i++)
 375         {
 376           int boffset =
 377           baseclass_offset (type, i, valaddr, address);
 378           if (boffset)
 379             return boffset;
 380         }
 381       /* Not found.  */
 382       return -1;
 383     }
 384
 385   /* Baseclass is easily computed.  */
 386   return TYPE_BASECLASS_BITPOS (type, index) / 8;
 387 }
 388
 389 static void
 390 init_gnuv2_ops (void)
 391 {
 392   gnu_v2_abi_ops.shortname = "gnu-v2";
 393   gnu_v2_abi_ops.longname = "GNU G++ Version 2 ABI";
 394   gnu_v2_abi_ops.doc = "G++ Version 2 ABI";
 395   gnu_v2_abi_ops.is_destructor_name = gnuv2_is_destructor_name;
 396   gnu_v2_abi_ops.is_constructor_name = gnuv2_is_constructor_name;
 397   gnu_v2_abi_ops.is_vtable_name = gnuv2_is_vtable_name;
 398   gnu_v2_abi_ops.is_operator_name = gnuv2_is_operator_name;
 399   gnu_v2_abi_ops.virtual_fn_field = gnuv2_virtual_fn_field;
 400   gnu_v2_abi_ops.rtti_type = gnuv2_value_rtti_type;
 401   gnu_v2_abi_ops.baseclass_offset = gnuv2_baseclass_offset;
 402 }
 403
 404 extern initialize_file_ftype _initialize_gnu_v2_abi; /* -Wmissing-prototypes */
 405
 406 void
 407 _initialize_gnu_v2_abi (void)
 408 {
 409   init_gnuv2_ops ();
 410   register_cp_abi (&gnu_v2_abi_ops);
 411   set_cp_abi_as_auto_default (gnu_v2_abi_ops.shortname);
 412 }