gdb/gnu-v2-abi.c

   1 /* Abstraction of GNU v2 abi.
   2
   3    Copyright (C) 2001, 2002, 2003, 2005, 2007, 2008, 2009, 2010
   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
  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   struct type *entry_type;
  92   /* First, get the virtual function table pointer.  That comes
  93      with a strange type, so cast it to type `pointer to long' (which
  94      should serve just fine as a function type).  Then, index into
  95      the table, and convert final value to appropriate function type.  */
  96   struct value *entry;
  97   struct value *vfn;
  98   struct value *vtbl;
  99   LONGEST vi = (LONGEST) TYPE_FN_FIELD_VOFFSET (f, j);
 100   struct type *fcontext = TYPE_FN_FIELD_FCONTEXT (f, j);
 101   struct type *context;
 102   struct type *context_vptr_basetype;
 103   int context_vptr_fieldno;
 104
 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   context_vptr_fieldno = get_vptr_fieldno (context, &context_vptr_basetype);
 127   /* FIXME: What to do if vptr_fieldno is still -1?  */
 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, context_vptr_fieldno,
 132                                 context_vptr_basetype);
 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_ptradd (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   struct type *known_type_vptr_basetype;
 198   int known_type_vptr_fieldno;
 199
 200   if (full)
 201     *full = 0;
 202   if (top)
 203     *top = -1;
 204   if (using_enc)
 205     *using_enc = 0;
 206
 207   /* Get declared type */
 208   known_type = value_type (v);
 209   CHECK_TYPEDEF (known_type);
 210   /* RTTI works only or class objects */
 211   if (TYPE_CODE (known_type) != TYPE_CODE_CLASS)
 212     return NULL;
 213
 214   /* Plan on this changing in the future as i get around to setting
 215      the vtables properly for G++ compiled stuff.  Also, I'll be using
 216      the type info functions, which are always right.  Deal with it
 217      until then.  */
 218
 219   /* Try to get the vptr basetype, fieldno.  */
 220   known_type_vptr_fieldno = get_vptr_fieldno (known_type,
 221                                               &known_type_vptr_basetype);
 222
 223   /* If we can't find it, give up.  */
 224   if (known_type_vptr_fieldno < 0)
 225     return NULL;
 226
 227   /* Make sure our basetype and known type match, otherwise, cast
 228      so we can get at the vtable properly.
 229   */
 230   btype = known_type_vptr_basetype;
 231   CHECK_TYPEDEF (btype);
 232   if (btype != known_type )
 233     {
 234       v = value_cast (btype, v);
 235       if (using_enc)
 236         *using_enc=1;
 237     }
 238   /*
 239     We can't use value_ind here, because it would want to use RTTI, and
 240     we'd waste a bunch of time figuring out we already know the type.
 241     Besides, we don't care about the type, just the actual pointer
 242   */
 243   if (value_address (value_field (v, known_type_vptr_fieldno)) == 0)
 244     return NULL;
 245
 246   vtbl = value_as_address (value_field (v, known_type_vptr_fieldno));
 247
 248   /* Try to find a symbol that is the vtable */
 249   minsym=lookup_minimal_symbol_by_pc(vtbl);
 250   if (minsym==NULL
 251       || (demangled_name=SYMBOL_LINKAGE_NAME (minsym))==NULL
 252       || !is_vtable_name (demangled_name))
 253     return NULL;
 254
 255   /* If we just skip the prefix, we get screwed by namespaces */
 256   demangled_name=cplus_demangle(demangled_name,DMGL_PARAMS|DMGL_ANSI);
 257   p = strchr (demangled_name, ' ');
 258   if (p)
 259     *p = '\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 static 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 }