gdb/gnu-v2-abi.c

   1 /* Abstraction of GNU v2 abi.
   2
   3    Copyright (C) 2001, 2002, 2003, 2005, 2007, 2008, 2009
   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   struct type *entry_type;
  93   /* First, get the virtual function table pointer.  That comes
  94      with a strange type, so cast it to type `pointer to long' (which
  95      should serve just fine as a function type).  Then, index into
  96      the table, and convert final value to appropriate function type.  */
  97   struct value *entry;
  98   struct value *vfn;
  99   struct value *vtbl;
 100   struct value *vi = value_from_longest (builtin_type_int32,
 101                                      (LONGEST) TYPE_FN_FIELD_VOFFSET (f, j));
 102   struct type *fcontext = TYPE_FN_FIELD_FCONTEXT (f, j);
 103   struct type *context;
 104   struct type *context_vptr_basetype;
 105   int context_vptr_fieldno;
 106
 107   if (fcontext == NULL)
 108     /* We don't have an fcontext (e.g. the program was compiled with
 109        g++ version 1).  Try to get the vtbl from the TYPE_VPTR_BASETYPE.
 110        This won't work right for multiple inheritance, but at least we
 111        should do as well as GDB 3.x did.  */
 112     fcontext = TYPE_VPTR_BASETYPE (type);
 113   context = lookup_pointer_type (fcontext);
 114   /* Now context is a pointer to the basetype containing the vtbl.  */
 115   if (TYPE_TARGET_TYPE (context) != type1)
 116     {
 117       struct value *tmp = value_cast (context, value_addr (arg1));
 118       arg1 = value_ind (tmp);
 119       type1 = check_typedef (value_type (arg1));
 120     }
 121
 122   context = type1;
 123   /* Now context is the basetype containing the vtbl.  */
 124
 125   /* This type may have been defined before its virtual function table
 126      was.  If so, fill in the virtual function table entry for the
 127      type now.  */
 128   context_vptr_fieldno = get_vptr_fieldno (context, &context_vptr_basetype);
 129   /* FIXME: What to do if vptr_fieldno is still -1?  */
 130
 131   /* The virtual function table is now an array of structures
 132      which have the form { int16 offset, delta; void *pfn; }.  */
 133   vtbl = value_primitive_field (arg1, 0, context_vptr_fieldno,
 134                                 context_vptr_basetype);
 135
 136   /* With older versions of g++, the vtbl field pointed to an array
 137      of structures.  Nowadays it points directly to the structure. */
 138   if (TYPE_CODE (value_type (vtbl)) == TYPE_CODE_PTR
 139       && TYPE_CODE (TYPE_TARGET_TYPE (value_type (vtbl))) == TYPE_CODE_ARRAY)
 140     {
 141       /* Handle the case where the vtbl field points to an
 142          array of structures. */
 143       vtbl = value_ind (vtbl);
 144
 145       /* Index into the virtual function table.  This is hard-coded because
 146          looking up a field is not cheap, and it may be important to save
 147          time, e.g. if the user has set a conditional breakpoint calling
 148          a virtual function.  */
 149       entry = value_subscript (vtbl, vi);
 150     }
 151   else
 152     {
 153       /* Handle the case where the vtbl field points directly to a structure. */
 154       vtbl = value_ptradd (vtbl, vi);
 155       entry = value_ind (vtbl);
 156     }
 157
 158   entry_type = check_typedef (value_type (entry));
 159
 160   if (TYPE_CODE (entry_type) == TYPE_CODE_STRUCT)
 161     {
 162       /* Move the `this' pointer according to the virtual function table. */
 163       set_value_offset (arg1, value_offset (arg1) + value_as_long (value_field (entry, 0)));
 164
 165       if (!value_lazy (arg1))
 166         {
 167           set_value_lazy (arg1, 1);
 168           value_fetch_lazy (arg1);
 169         }
 170
 171       vfn = value_field (entry, 2);
 172     }
 173   else if (TYPE_CODE (entry_type) == TYPE_CODE_PTR)
 174     vfn = entry;
 175   else
 176     error (_("I'm confused:  virtual function table has bad type"));
 177   /* Reinstantiate the function pointer with the correct type.  */
 178   deprecated_set_value_type (vfn, 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, int *top, int *using_enc)
 187 {
 188   struct type *known_type;
 189   struct type *rtti_type;
 190   CORE_ADDR coreptr;
 191   struct value *vp;
 192   long top_offset = 0;
 193   char rtti_type_name[256];
 194   CORE_ADDR vtbl;
 195   struct minimal_symbol *minsym;
 196   struct symbol *sym;
 197   char *demangled_name, *p;
 198   struct type *btype;
 199   struct type *known_type_vptr_basetype;
 200   int known_type_vptr_fieldno;
 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   /* Try to get the vptr basetype, fieldno.  */
 222   known_type_vptr_fieldno = get_vptr_fieldno (known_type,
 223                                               &known_type_vptr_basetype);
 224
 225   /* If we can't find it, give up.  */
 226   if (known_type_vptr_fieldno < 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 = known_type_vptr_basetype;
 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, known_type_vptr_fieldno)) == 0)
 246     return NULL;
 247
 248   vtbl = value_as_address (value_field (v, known_type_vptr_fieldno));
 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=SYMBOL_LINKAGE_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   p = strchr (demangled_name, ' ');
 260   if (p)
 261     *p = '\0';
 262
 263   /* Lookup the type for the name */
 264   /* FIXME: chastain/2003-11-26: block=NULL is bogus.  See pr gdb/1465. */
 265   rtti_type = cp_lookup_rtti_type (demangled_name, NULL);
 266   if (rtti_type == NULL)
 267     return NULL;
 268
 269   if (TYPE_N_BASECLASSES(rtti_type) > 1 &&  full && (*full) != 1)
 270     {
 271       if (top)
 272         *top=TYPE_BASECLASS_BITPOS(rtti_type,TYPE_VPTR_FIELDNO(rtti_type))/8;
 273       if (top && ((*top) >0))
 274         {
 275           if (TYPE_LENGTH(rtti_type) > TYPE_LENGTH(known_type))
 276             {
 277               if (full)
 278                 *full=0;
 279             }
 280           else
 281             {
 282               if (full)
 283                 *full=1;
 284             }
 285         }
 286     }
 287   else
 288     {
 289       if (full)
 290         *full=1;
 291     }
 292
 293   return rtti_type;
 294 }
 295
 296 /* Return true if the INDEXth field of TYPE is a virtual baseclass
 297    pointer which is for the base class whose type is BASECLASS.  */
 298
 299 static int
 300 vb_match (struct type *type, int index, struct type *basetype)
 301 {
 302   struct type *fieldtype;
 303   char *name = TYPE_FIELD_NAME (type, index);
 304   char *field_class_name = NULL;
 305
 306   if (*name != '_')
 307     return 0;
 308   /* gcc 2.4 uses _vb$.  */
 309   if (name[1] == 'v' && name[2] == 'b' && is_cplus_marker (name[3]))
 310     field_class_name = name + 4;
 311   /* gcc 2.5 will use __vb_.  */
 312   if (name[1] == '_' && name[2] == 'v' && name[3] == 'b' && name[4] == '_')
 313     field_class_name = name + 5;
 314
 315   if (field_class_name == NULL)
 316     /* This field is not a virtual base class pointer.  */
 317     return 0;
 318
 319   /* It's a virtual baseclass pointer, now we just need to find out whether
 320      it is for this baseclass.  */
 321   fieldtype = TYPE_FIELD_TYPE (type, index);
 322   if (fieldtype == NULL
 323       || TYPE_CODE (fieldtype) != TYPE_CODE_PTR)
 324     /* "Can't happen".  */
 325     return 0;
 326
 327   /* What we check for is that either the types are equal (needed for
 328      nameless types) or have the same name.  This is ugly, and a more
 329      elegant solution should be devised (which would probably just push
 330      the ugliness into symbol reading unless we change the stabs format).  */
 331   if (TYPE_TARGET_TYPE (fieldtype) == basetype)
 332     return 1;
 333
 334   if (TYPE_NAME (basetype) != NULL
 335       && TYPE_NAME (TYPE_TARGET_TYPE (fieldtype)) != NULL
 336       && strcmp (TYPE_NAME (basetype),
 337                  TYPE_NAME (TYPE_TARGET_TYPE (fieldtype))) == 0)
 338     return 1;
 339   return 0;
 340 }
 341
 342 /* Compute the offset of the baseclass which is
 343    the INDEXth baseclass of class TYPE,
 344    for value at VALADDR (in host) at ADDRESS (in target).
 345    The result is the offset of the baseclass value relative
 346    to (the address of)(ARG) + OFFSET.
 347
 348    -1 is returned on error. */
 349
 350 int
 351 gnuv2_baseclass_offset (struct type *type, int index,
 352                         const bfd_byte *valaddr, CORE_ADDR address)
 353 {
 354   struct type *basetype = TYPE_BASECLASS (type, index);
 355
 356   if (BASETYPE_VIA_VIRTUAL (type, index))
 357     {
 358       /* Must hunt for the pointer to this virtual baseclass.  */
 359       int i, len = TYPE_NFIELDS (type);
 360       int n_baseclasses = TYPE_N_BASECLASSES (type);
 361
 362       /* First look for the virtual baseclass pointer
 363          in the fields.  */
 364       for (i = n_baseclasses; i < len; i++)
 365         {
 366           if (vb_match (type, i, basetype))
 367             {
 368               CORE_ADDR addr
 369               = unpack_pointer (TYPE_FIELD_TYPE (type, i),
 370                                 valaddr + (TYPE_FIELD_BITPOS (type, i) / 8));
 371
 372               return addr - (LONGEST) address;
 373             }
 374         }
 375       /* Not in the fields, so try looking through the baseclasses.  */
 376       for (i = index + 1; i < n_baseclasses; i++)
 377         {
 378           int boffset =
 379           baseclass_offset (type, i, valaddr, address);
 380           if (boffset)
 381             return boffset;
 382         }
 383       /* Not found.  */
 384       return -1;
 385     }
 386
 387   /* Baseclass is easily computed.  */
 388   return TYPE_BASECLASS_BITPOS (type, index) / 8;
 389 }
 390
 391 static void
 392 init_gnuv2_ops (void)
 393 {
 394   gnu_v2_abi_ops.shortname = "gnu-v2";
 395   gnu_v2_abi_ops.longname = "GNU G++ Version 2 ABI";
 396   gnu_v2_abi_ops.doc = "G++ Version 2 ABI";
 397   gnu_v2_abi_ops.is_destructor_name = gnuv2_is_destructor_name;
 398   gnu_v2_abi_ops.is_constructor_name = gnuv2_is_constructor_name;
 399   gnu_v2_abi_ops.is_vtable_name = gnuv2_is_vtable_name;
 400   gnu_v2_abi_ops.is_operator_name = gnuv2_is_operator_name;
 401   gnu_v2_abi_ops.virtual_fn_field = gnuv2_virtual_fn_field;
 402   gnu_v2_abi_ops.rtti_type = gnuv2_value_rtti_type;
 403   gnu_v2_abi_ops.baseclass_offset = gnuv2_baseclass_offset;
 404 }
 405
 406 extern initialize_file_ftype _initialize_gnu_v2_abi; /* -Wmissing-prototypes */
 407
 408 void
 409 _initialize_gnu_v2_abi (void)
 410 {
 411   init_gnuv2_ops ();
 412   register_cp_abi (&gnu_v2_abi_ops);
 413   set_cp_abi_as_auto_default (gnu_v2_abi_ops.shortname);
 414 }