gdb/gnu-v2-abi.c

   1 /* Abstraction of GNU v2 abi.
   2
   3    Copyright (C) 2001, 2002, 2003, 2005, 2007, 2008
   4    Free Software Foundation, Inc.
   5
   6    Contributed by Daniel Berlin <dberlin@redhat.com>
   7
   8    This file is part of GDB.
   9
  10    This program is free software; you can redistribute it and/or modify
  11    it under the terms of the GNU General Public License as published by
  12    the Free Software Foundation; either version 3 of the License, or
  13    (at your option) any later version.
  14
  15    This program is distributed in the hope that it will be useful,
  16    but WITHOUT ANY WARRANTY; without even the implied warranty of
  17    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  18    GNU General Public License for more details.
  19
  20    You should have received a copy of the GNU General Public License
  21    along with this program.  If not, see <http://www.gnu.org/licenses/>.  */
  22
  23 #include "defs.h"
  24 #include "gdb_string.h"
  25 #include "symtab.h"
  26 #include "gdbtypes.h"
  27 #include "value.h"
  28 #include "demangle.h"
  29 #include "cp-abi.h"
  30 #include "cp-support.h"
  31 #include "gnu-v2-abi.h"
  32
  33 #include <ctype.h>
  34
  35 struct cp_abi_ops gnu_v2_abi_ops;
  36
  37 static int vb_match (struct type *, int, struct type *);
  38
  39 static enum dtor_kinds
  40 gnuv2_is_destructor_name (const char *name)
  41 {
  42   if ((name[0] == '_' && is_cplus_marker (name[1]) && name[2] == '_')
  43       || strncmp (name, "__dt__", 6) == 0)
  44     return complete_object_dtor;
  45   else
  46     return 0;
  47 }
  48
  49 static enum ctor_kinds
  50 gnuv2_is_constructor_name (const char *name)
  51 {
  52   if ((name[0] == '_' && name[1] == '_'
  53        && (isdigit (name[2]) || strchr ("Qt", name[2])))
  54       || strncmp (name, "__ct__", 6) == 0)
  55     return complete_object_ctor;
  56   else
  57     return 0;
  58 }
  59
  60 static int
  61 gnuv2_is_vtable_name (const char *name)
  62 {
  63   return (((name)[0] == '_'
  64            && (((name)[1] == 'V' && (name)[2] == 'T')
  65                || ((name)[1] == 'v' && (name)[2] == 't'))
  66            && is_cplus_marker ((name)[3])) ||
  67           ((name)[0] == '_' && (name)[1] == '_'
  68            && (name)[2] == 'v' && (name)[3] == 't' && (name)[4] == '_'));
  69 }
  70
  71 static int
  72 gnuv2_is_operator_name (const char *name)
  73 {
  74   return strncmp (name, "operator", 8) == 0;
  75 }
  76
  77 \f
  78 /* Return a virtual function as a value.
  79    ARG1 is the object which provides the virtual function
  80    table pointer.  *ARG1P is side-effected in calling this function.
  81    F is the list of member functions which contains the desired virtual
  82    function.
  83    J is an index into F which provides the desired virtual function.
  84
  85    TYPE is the type in which F is located.  */
  86 static struct value *
  87 gnuv2_virtual_fn_field (struct value **arg1p, struct fn_field * f, int j,
  88                         struct type * type, int offset)
  89 {
  90   struct value *arg1 = *arg1p;
  91   struct type *type1 = check_typedef (value_type (arg1));
  92
  93
  94   struct type *entry_type;
  95   /* First, get the virtual function table pointer.  That comes
  96      with a strange type, so cast it to type `pointer to long' (which
  97      should serve just fine as a function type).  Then, index into
  98      the table, and convert final value to appropriate function type.  */
  99   struct value *entry;
 100   struct value *vfn;
 101   struct value *vtbl;
 102   struct value *vi = value_from_longest (builtin_type_int,
 103                                      (LONGEST) TYPE_FN_FIELD_VOFFSET (f, j));
 104   struct type *fcontext = TYPE_FN_FIELD_FCONTEXT (f, j);
 105   struct type *context;
 106   if (fcontext == NULL)
 107     /* We don't have an fcontext (e.g. the program was compiled with
 108        g++ version 1).  Try to get the vtbl from the TYPE_VPTR_BASETYPE.
 109        This won't work right for multiple inheritance, but at least we
 110        should do as well as GDB 3.x did.  */
 111     fcontext = TYPE_VPTR_BASETYPE (type);
 112   context = lookup_pointer_type (fcontext);
 113   /* Now context is a pointer to the basetype containing the vtbl.  */
 114   if (TYPE_TARGET_TYPE (context) != type1)
 115     {
 116       struct value *tmp = value_cast (context, value_addr (arg1));
 117       arg1 = value_ind (tmp);
 118       type1 = check_typedef (value_type (arg1));
 119     }
 120
 121   context = type1;
 122   /* Now context is the basetype containing the vtbl.  */
 123
 124   /* This type may have been defined before its virtual function table
 125      was.  If so, fill in the virtual function table entry for the
 126      type now.  */
 127   if (TYPE_VPTR_FIELDNO (context) < 0)
 128     fill_in_vptr_fieldno (context);
 129
 130   /* The virtual function table is now an array of structures
 131      which have the form { int16 offset, delta; void *pfn; }.  */
 132   vtbl = value_primitive_field (arg1, 0, TYPE_VPTR_FIELDNO (context),
 133                                 TYPE_VPTR_BASETYPE (context));
 134
 135   /* With older versions of g++, the vtbl field pointed to an array
 136      of structures.  Nowadays it points directly to the structure. */
 137   if (TYPE_CODE (value_type (vtbl)) == TYPE_CODE_PTR
 138       && TYPE_CODE (TYPE_TARGET_TYPE (value_type (vtbl))) == TYPE_CODE_ARRAY)
 139     {
 140       /* Handle the case where the vtbl field points to an
 141          array of structures. */
 142       vtbl = value_ind (vtbl);
 143
 144       /* Index into the virtual function table.  This is hard-coded because
 145          looking up a field is not cheap, and it may be important to save
 146          time, e.g. if the user has set a conditional breakpoint calling
 147          a virtual function.  */
 148       entry = value_subscript (vtbl, vi);
 149     }
 150   else
 151     {
 152       /* Handle the case where the vtbl field points directly to a structure. */
 153       vtbl = value_add (vtbl, vi);
 154       entry = value_ind (vtbl);
 155     }
 156
 157   entry_type = check_typedef (value_type (entry));
 158
 159   if (TYPE_CODE (entry_type) == TYPE_CODE_STRUCT)
 160     {
 161       /* Move the `this' pointer according to the virtual function table. */
 162       set_value_offset (arg1, value_offset (arg1) + 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 (TYPE_CODE (entry_type) == 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, lookup_pointer_type (TYPE_FN_FIELD_TYPE (f, j)));
 178
 179   *arg1p = arg1;
 180   return vfn;
 181 }
 182
 183
 184 static struct type *
 185 gnuv2_value_rtti_type (struct value *v, int *full, int *top, int *using_enc)
 186 {
 187   struct type *known_type;
 188   struct type *rtti_type;
 189   CORE_ADDR coreptr;
 190   struct value *vp;
 191   long top_offset = 0;
 192   char rtti_type_name[256];
 193   CORE_ADDR vtbl;
 194   struct minimal_symbol *minsym;
 195   struct symbol *sym;
 196   char *demangled_name, *p;
 197   struct type *btype;
 198
 199   if (full)
 200     *full = 0;
 201   if (top)
 202     *top = -1;
 203   if (using_enc)
 204     *using_enc = 0;
 205
 206   /* Get declared type */
 207   known_type = value_type (v);
 208   CHECK_TYPEDEF (known_type);
 209   /* RTTI works only or class objects */
 210   if (TYPE_CODE (known_type) != TYPE_CODE_CLASS)
 211     return NULL;
 212
 213   /* Plan on this changing in the future as i get around to setting
 214      the vtables properly for G++ compiled stuff.  Also, I'll be using
 215      the type info functions, which are always right.  Deal with it
 216      until then.  */
 217
 218   /* If the type has no vptr fieldno, try to get it filled in */
 219   if (TYPE_VPTR_FIELDNO(known_type) < 0)
 220     fill_in_vptr_fieldno(known_type);
 221
 222   /* If we still can't find one, give up */
 223   if (TYPE_VPTR_FIELDNO(known_type) < 0)
 224     return NULL;
 225
 226   /* Make sure our basetype and known type match, otherwise, cast
 227      so we can get at the vtable properly.
 228   */
 229   btype = TYPE_VPTR_BASETYPE (known_type);
 230   CHECK_TYPEDEF (btype);
 231   if (btype != known_type )
 232     {
 233       v = value_cast (btype, v);
 234       if (using_enc)
 235         *using_enc=1;
 236     }
 237   /*
 238     We can't use value_ind here, because it would want to use RTTI, and
 239     we'd waste a bunch of time figuring out we already know the type.
 240     Besides, we don't care about the type, just the actual pointer
 241   */
 242   if (VALUE_ADDRESS (value_field (v, TYPE_VPTR_FIELDNO (known_type))) == 0)
 243     return NULL;
 244
 245   vtbl=value_as_address(value_field(v,TYPE_VPTR_FIELDNO(known_type)));
 246
 247   /* Try to find a symbol that is the vtable */
 248   minsym=lookup_minimal_symbol_by_pc(vtbl);
 249   if (minsym==NULL
 250       || (demangled_name=DEPRECATED_SYMBOL_NAME (minsym))==NULL
 251       || !is_vtable_name (demangled_name))
 252     return NULL;
 253
 254   /* If we just skip the prefix, we get screwed by namespaces */
 255   demangled_name=cplus_demangle(demangled_name,DMGL_PARAMS|DMGL_ANSI);
 256   p = strchr (demangled_name, ' ');
 257   if (p)
 258     *p = '\0';
 259
 260   /* Lookup the type for the name */
 261   /* FIXME: chastain/2003-11-26: block=NULL is bogus.  See pr gdb/1465. */
 262   rtti_type = cp_lookup_rtti_type (demangled_name, NULL);
 263   if (rtti_type == NULL)
 264     return NULL;
 265
 266   if (TYPE_N_BASECLASSES(rtti_type) > 1 &&  full && (*full) != 1)
 267     {
 268       if (top)
 269         *top=TYPE_BASECLASS_BITPOS(rtti_type,TYPE_VPTR_FIELDNO(rtti_type))/8;
 270       if (top && ((*top) >0))
 271         {
 272           if (TYPE_LENGTH(rtti_type) > TYPE_LENGTH(known_type))
 273             {
 274               if (full)
 275                 *full=0;
 276             }
 277           else
 278             {
 279               if (full)
 280                 *full=1;
 281             }
 282         }
 283     }
 284   else
 285     {
 286       if (full)
 287         *full=1;
 288     }
 289
 290   return rtti_type;
 291 }
 292
 293 /* Return true if the INDEXth field of TYPE is a virtual baseclass
 294    pointer which is for the base class whose type is BASECLASS.  */
 295
 296 static int
 297 vb_match (struct type *type, int index, struct type *basetype)
 298 {
 299   struct type *fieldtype;
 300   char *name = TYPE_FIELD_NAME (type, index);
 301   char *field_class_name = NULL;
 302
 303   if (*name != '_')
 304     return 0;
 305   /* gcc 2.4 uses _vb$.  */
 306   if (name[1] == 'v' && name[2] == 'b' && is_cplus_marker (name[3]))
 307     field_class_name = name + 4;
 308   /* gcc 2.5 will use __vb_.  */
 309   if (name[1] == '_' && name[2] == 'v' && name[3] == 'b' && name[4] == '_')
 310     field_class_name = name + 5;
 311
 312   if (field_class_name == NULL)
 313     /* This field is not a virtual base class pointer.  */
 314     return 0;
 315
 316   /* It's a virtual baseclass pointer, now we just need to find out whether
 317      it is for this baseclass.  */
 318   fieldtype = TYPE_FIELD_TYPE (type, index);
 319   if (fieldtype == NULL
 320       || TYPE_CODE (fieldtype) != TYPE_CODE_PTR)
 321     /* "Can't happen".  */
 322     return 0;
 323
 324   /* What we check for is that either the types are equal (needed for
 325      nameless types) or have the same name.  This is ugly, and a more
 326      elegant solution should be devised (which would probably just push
 327      the ugliness into symbol reading unless we change the stabs format).  */
 328   if (TYPE_TARGET_TYPE (fieldtype) == basetype)
 329     return 1;
 330
 331   if (TYPE_NAME (basetype) != NULL
 332       && TYPE_NAME (TYPE_TARGET_TYPE (fieldtype)) != NULL
 333       && strcmp (TYPE_NAME (basetype),
 334                  TYPE_NAME (TYPE_TARGET_TYPE (fieldtype))) == 0)
 335     return 1;
 336   return 0;
 337 }
 338
 339 /* Compute the offset of the baseclass which is
 340    the INDEXth baseclass of class TYPE,
 341    for value at VALADDR (in host) at ADDRESS (in target).
 342    The result is the offset of the baseclass value relative
 343    to (the address of)(ARG) + OFFSET.
 344
 345    -1 is returned on error. */
 346
 347 int
 348 gnuv2_baseclass_offset (struct type *type, int index,
 349                         const bfd_byte *valaddr, CORE_ADDR address)
 350 {
 351   struct type *basetype = TYPE_BASECLASS (type, index);
 352
 353   if (BASETYPE_VIA_VIRTUAL (type, index))
 354     {
 355       /* Must hunt for the pointer to this virtual baseclass.  */
 356       int i, len = TYPE_NFIELDS (type);
 357       int n_baseclasses = TYPE_N_BASECLASSES (type);
 358
 359       /* First look for the virtual baseclass pointer
 360          in the fields.  */
 361       for (i = n_baseclasses; i < len; i++)
 362         {
 363           if (vb_match (type, i, basetype))
 364             {
 365               CORE_ADDR addr
 366               = unpack_pointer (TYPE_FIELD_TYPE (type, i),
 367                                 valaddr + (TYPE_FIELD_BITPOS (type, i) / 8));
 368
 369               return addr - (LONGEST) address;
 370             }
 371         }
 372       /* Not in the fields, so try looking through the baseclasses.  */
 373       for (i = index + 1; i < n_baseclasses; i++)
 374         {
 375           int boffset =
 376           baseclass_offset (type, i, valaddr, address);
 377           if (boffset)
 378             return boffset;
 379         }
 380       /* Not found.  */
 381       return -1;
 382     }
 383
 384   /* Baseclass is easily computed.  */
 385   return TYPE_BASECLASS_BITPOS (type, index) / 8;
 386 }
 387
 388 static void
 389 init_gnuv2_ops (void)
 390 {
 391   gnu_v2_abi_ops.shortname = "gnu-v2";
 392   gnu_v2_abi_ops.longname = "GNU G++ Version 2 ABI";
 393   gnu_v2_abi_ops.doc = "G++ Version 2 ABI";
 394   gnu_v2_abi_ops.is_destructor_name = gnuv2_is_destructor_name;
 395   gnu_v2_abi_ops.is_constructor_name = gnuv2_is_constructor_name;
 396   gnu_v2_abi_ops.is_vtable_name = gnuv2_is_vtable_name;
 397   gnu_v2_abi_ops.is_operator_name = gnuv2_is_operator_name;
 398   gnu_v2_abi_ops.virtual_fn_field = gnuv2_virtual_fn_field;
 399   gnu_v2_abi_ops.rtti_type = gnuv2_value_rtti_type;
 400   gnu_v2_abi_ops.baseclass_offset = gnuv2_baseclass_offset;
 401 }
 402
 403 extern initialize_file_ftype _initialize_gnu_v2_abi; /* -Wmissing-prototypes */
 404
 405 void
 406 _initialize_gnu_v2_abi (void)
 407 {
 408   init_gnuv2_ops ();
 409   register_cp_abi (&gnu_v2_abi_ops);
 410   set_cp_abi_as_auto_default (gnu_v2_abi_ops.shortname);
 411 }