gdb/gnu-v2-abi.c

   1 /* Abstraction of GNU v2 abi.
   2
   3    Copyright (C) 2001, 2002, 2003, 2005, 2007, 2008, 2009, 2010, 2011
   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
 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   context_vptr_fieldno = get_vptr_fieldno (context, &context_vptr_basetype);
 128   /* FIXME: What to do if vptr_fieldno is still -1?  */
 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, context_vptr_fieldno,
 133                                 context_vptr_basetype);
 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
 153          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)
 164                         + value_as_long (value_field (entry, 0)));
 165
 166       if (!value_lazy (arg1))
 167         {
 168           set_value_lazy (arg1, 1);
 169           value_fetch_lazy (arg1);
 170         }
 171
 172       vfn = value_field (entry, 2);
 173     }
 174   else if (TYPE_CODE (entry_type) == TYPE_CODE_PTR)
 175     vfn = entry;
 176   else
 177     error (_("I'm confused:  virtual function table has bad type"));
 178   /* Reinstantiate the function pointer with the correct type.  */
 179   deprecated_set_value_type (vfn,
 180                              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 vtbl;
 193   struct minimal_symbol *minsym;
 194   char *demangled_name, *p;
 195   struct type *btype;
 196   struct type *known_type_vptr_basetype;
 197   int known_type_vptr_fieldno;
 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   /* Try to get the vptr basetype, fieldno.  */
 219   known_type_vptr_fieldno = get_vptr_fieldno (known_type,
 220                                               &known_type_vptr_basetype);
 221
 222   /* If we can't find it, give up.  */
 223   if (known_type_vptr_fieldno < 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   btype = known_type_vptr_basetype;
 229   CHECK_TYPEDEF (btype);
 230   if (btype != known_type )
 231     {
 232       v = value_cast (btype, v);
 233       if (using_enc)
 234         *using_enc=1;
 235     }
 236   /* We can't use value_ind here, because it would want to use RTTI, and
 237      we'd waste a bunch of time figuring out we already know the type.
 238      Besides, we don't care about the type, just the actual pointer.  */
 239   if (value_address (value_field (v, known_type_vptr_fieldno)) == 0)
 240     return NULL;
 241
 242   vtbl = value_as_address (value_field (v, known_type_vptr_fieldno));
 243
 244   /* Try to find a symbol that is the vtable.  */
 245   minsym=lookup_minimal_symbol_by_pc(vtbl);
 246   if (minsym==NULL
 247       || (demangled_name=SYMBOL_LINKAGE_NAME (minsym))==NULL
 248       || !is_vtable_name (demangled_name))
 249     return NULL;
 250
 251   /* If we just skip the prefix, we get screwed by namespaces.  */
 252   demangled_name=cplus_demangle(demangled_name,DMGL_PARAMS|DMGL_ANSI);
 253   p = strchr (demangled_name, ' ');
 254   if (p)
 255     *p = '\0';
 256
 257   /* Lookup the type for the name.  */
 258   /* FIXME: chastain/2003-11-26: block=NULL is bogus.  See pr gdb/1465.  */
 259   rtti_type = cp_lookup_rtti_type (demangled_name, NULL);
 260   if (rtti_type == NULL)
 261     return NULL;
 262
 263   if (TYPE_N_BASECLASSES(rtti_type) > 1 &&  full && (*full) != 1)
 264     {
 265       if (top)
 266         *top = TYPE_BASECLASS_BITPOS (rtti_type,
 267                                       TYPE_VPTR_FIELDNO(rtti_type)) / 8;
 268       if (top && ((*top) >0))
 269         {
 270           if (TYPE_LENGTH(rtti_type) > TYPE_LENGTH(known_type))
 271             {
 272               if (full)
 273                 *full=0;
 274             }
 275           else
 276             {
 277               if (full)
 278                 *full=1;
 279             }
 280         }
 281     }
 282   else
 283     {
 284       if (full)
 285         *full=1;
 286     }
 287
 288   return rtti_type;
 289 }
 290
 291 /* Return true if the INDEXth field of TYPE is a virtual baseclass
 292    pointer which is for the base class whose type is BASECLASS.  */
 293
 294 static int
 295 vb_match (struct type *type, int index, struct type *basetype)
 296 {
 297   struct type *fieldtype;
 298   char *name = TYPE_FIELD_NAME (type, index);
 299   char *field_class_name = NULL;
 300
 301   if (*name != '_')
 302     return 0;
 303   /* gcc 2.4 uses _vb$.  */
 304   if (name[1] == 'v' && name[2] == 'b' && is_cplus_marker (name[3]))
 305     field_class_name = name + 4;
 306   /* gcc 2.5 will use __vb_.  */
 307   if (name[1] == '_' && name[2] == 'v' && name[3] == 'b' && name[4] == '_')
 308     field_class_name = name + 5;
 309
 310   if (field_class_name == NULL)
 311     /* This field is not a virtual base class pointer.  */
 312     return 0;
 313
 314   /* It's a virtual baseclass pointer, now we just need to find out whether
 315      it is for this baseclass.  */
 316   fieldtype = TYPE_FIELD_TYPE (type, index);
 317   if (fieldtype == NULL
 318       || TYPE_CODE (fieldtype) != TYPE_CODE_PTR)
 319     /* "Can't happen".  */
 320     return 0;
 321
 322   /* What we check for is that either the types are equal (needed for
 323      nameless types) or have the same name.  This is ugly, and a more
 324      elegant solution should be devised (which would probably just push
 325      the ugliness into symbol reading unless we change the stabs format).  */
 326   if (TYPE_TARGET_TYPE (fieldtype) == basetype)
 327     return 1;
 328
 329   if (TYPE_NAME (basetype) != NULL
 330       && TYPE_NAME (TYPE_TARGET_TYPE (fieldtype)) != NULL
 331       && strcmp (TYPE_NAME (basetype),
 332                  TYPE_NAME (TYPE_TARGET_TYPE (fieldtype))) == 0)
 333     return 1;
 334   return 0;
 335 }
 336
 337 /* Compute the offset of the baseclass which is
 338    the INDEXth baseclass of class TYPE,
 339    for value at VALADDR (in host) at ADDRESS (in target).
 340    The result is the offset of the baseclass value relative
 341    to (the address of)(ARG) + OFFSET.
 342
 343    -1 is returned on error.  */
 344
 345 static int
 346 gnuv2_baseclass_offset (struct type *type, int index,
 347                         const bfd_byte *valaddr, CORE_ADDR address)
 348 {
 349   struct type *basetype = TYPE_BASECLASS (type, index);
 350
 351   if (BASETYPE_VIA_VIRTUAL (type, index))
 352     {
 353       /* Must hunt for the pointer to this virtual baseclass.  */
 354       int i, len = TYPE_NFIELDS (type);
 355       int n_baseclasses = TYPE_N_BASECLASSES (type);
 356
 357       /* First look for the virtual baseclass pointer
 358          in the fields.  */
 359       for (i = n_baseclasses; i < len; i++)
 360         {
 361           if (vb_match (type, i, basetype))
 362             {
 363               CORE_ADDR addr
 364                 = unpack_pointer (TYPE_FIELD_TYPE (type, i),
 365                                   valaddr + (TYPE_FIELD_BITPOS (type, i) / 8));
 366
 367               return addr - (LONGEST) address;
 368             }
 369         }
 370       /* Not in the fields, so try looking through the baseclasses.  */
 371       for (i = index + 1; i < n_baseclasses; i++)
 372         {
 373           int boffset =
 374             baseclass_offset (type, i, valaddr, address);
 375
 376           if (boffset)
 377             return boffset;
 378         }
 379       /* Not found.  */
 380       return -1;
 381     }
 382
 383   /* Baseclass is easily computed.  */
 384   return TYPE_BASECLASS_BITPOS (type, index) / 8;
 385 }
 386
 387 static void
 388 init_gnuv2_ops (void)
 389 {
 390   gnu_v2_abi_ops.shortname = "gnu-v2";
 391   gnu_v2_abi_ops.longname = "GNU G++ Version 2 ABI";
 392   gnu_v2_abi_ops.doc = "G++ Version 2 ABI";
 393   gnu_v2_abi_ops.is_destructor_name = gnuv2_is_destructor_name;
 394   gnu_v2_abi_ops.is_constructor_name = gnuv2_is_constructor_name;
 395   gnu_v2_abi_ops.is_vtable_name = gnuv2_is_vtable_name;
 396   gnu_v2_abi_ops.is_operator_name = gnuv2_is_operator_name;
 397   gnu_v2_abi_ops.virtual_fn_field = gnuv2_virtual_fn_field;
 398   gnu_v2_abi_ops.rtti_type = gnuv2_value_rtti_type;
 399   gnu_v2_abi_ops.baseclass_offset = gnuv2_baseclass_offset;
 400 }
 401
 402 extern initialize_file_ftype _initialize_gnu_v2_abi; /* -Wmissing-prototypes */
 403
 404 void
 405 _initialize_gnu_v2_abi (void)
 406 {
 407   init_gnuv2_ops ();
 408   register_cp_abi (&gnu_v2_abi_ops);
 409   set_cp_abi_as_auto_default (gnu_v2_abi_ops.shortname);
 410 }