gdb/gnu-v2-abi.c

   1 /* Abstraction of GNU v2 abi.
   2
   3    Copyright (C) 2001-2014 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 modify
  10    it under the terms of the GNU General Public License as published by
  11    the Free Software Foundation; either version 3 of the License, or
  12    (at your option) any later version.
  13
  14    This program is distributed in the hope that it will be useful,
  15    but WITHOUT ANY WARRANTY; without even the implied warranty of
  16    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  17    GNU General Public License for more details.
  18
  19    You should have received a copy of the GNU General Public License
  20    along with this program.  If not, see <http://www.gnu.org/licenses/>.  */
  21
  22 #include "defs.h"
  23 #include "symtab.h"
  24 #include "gdbtypes.h"
  25 #include "value.h"
  26 #include "demangle.h"
  27 #include "gdb-demangle.h"
  28 #include "cp-abi.h"
  29 #include "cp-support.h"
  30 #include "exceptions.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 bound_minimal_symbol minsym;
 194   char *demangled_name, *p;
 195   const char *linkage_name;
 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   btype = known_type_vptr_basetype;
 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   /* We can't use value_ind here, because it would want to use RTTI, and
 238      we'd waste a bunch of time figuring out we already know the type.
 239      Besides, we don't care about the type, just the actual pointer.  */
 240   if (value_address (value_field (v, known_type_vptr_fieldno)) == 0)
 241     return NULL;
 242
 243   vtbl = value_as_address (value_field (v, known_type_vptr_fieldno));
 244
 245   /* Try to find a symbol that is the vtable.  */
 246   minsym=lookup_minimal_symbol_by_pc(vtbl);
 247   if (minsym.minsym==NULL
 248       || (linkage_name=MSYMBOL_LINKAGE_NAME (minsym.minsym))==NULL
 249       || !is_vtable_name (linkage_name))
 250     return NULL;
 251
 252   /* If we just skip the prefix, we get screwed by namespaces.  */
 253   demangled_name=gdb_demangle(linkage_name,DMGL_PARAMS|DMGL_ANSI);
 254   p = strchr (demangled_name, ' ');
 255   if (p)
 256     *p = '\0';
 257
 258   /* Lookup the type for the name.  */
 259   /* FIXME: chastain/2003-11-26: block=NULL is bogus.  See pr gdb/1465.  */
 260   rtti_type = cp_lookup_rtti_type (demangled_name, NULL);
 261   if (rtti_type == NULL)
 262     return NULL;
 263
 264   if (TYPE_N_BASECLASSES(rtti_type) > 1 &&  full && (*full) != 1)
 265     {
 266       if (top)
 267         *top = TYPE_BASECLASS_BITPOS (rtti_type,
 268                                       TYPE_VPTR_FIELDNO(rtti_type)) / 8;
 269       if (top && ((*top) >0))
 270         {
 271           if (TYPE_LENGTH(rtti_type) > TYPE_LENGTH(known_type))
 272             {
 273               if (full)
 274                 *full=0;
 275             }
 276           else
 277             {
 278               if (full)
 279                 *full=1;
 280             }
 281         }
 282     }
 283   else
 284     {
 285       if (full)
 286         *full=1;
 287     }
 288
 289   return rtti_type;
 290 }
 291
 292 /* Return true if the INDEXth field of TYPE is a virtual baseclass
 293    pointer which is for the base class whose type is BASECLASS.  */
 294
 295 static int
 296 vb_match (struct type *type, int index, struct type *basetype)
 297 {
 298   struct type *fieldtype;
 299   const char *name = TYPE_FIELD_NAME (type, index);
 300   const char *field_class_name = NULL;
 301
 302   if (*name != '_')
 303     return 0;
 304   /* gcc 2.4 uses _vb$.  */
 305   if (name[1] == 'v' && name[2] == 'b' && is_cplus_marker (name[3]))
 306     field_class_name = name + 4;
 307   /* gcc 2.5 will use __vb_.  */
 308   if (name[1] == '_' && name[2] == 'v' && name[3] == 'b' && name[4] == '_')
 309     field_class_name = name + 5;
 310
 311   if (field_class_name == NULL)
 312     /* This field is not a virtual base class pointer.  */
 313     return 0;
 314
 315   /* It's a virtual baseclass pointer, now we just need to find out whether
 316      it is for this baseclass.  */
 317   fieldtype = TYPE_FIELD_TYPE (type, index);
 318   if (fieldtype == NULL
 319       || TYPE_CODE (fieldtype) != TYPE_CODE_PTR)
 320     /* "Can't happen".  */
 321     return 0;
 322
 323   /* What we check for is that either the types are equal (needed for
 324      nameless types) or have the same name.  This is ugly, and a more
 325      elegant solution should be devised (which would probably just push
 326      the ugliness into symbol reading unless we change the stabs format).  */
 327   if (TYPE_TARGET_TYPE (fieldtype) == basetype)
 328     return 1;
 329
 330   if (TYPE_NAME (basetype) != NULL
 331       && TYPE_NAME (TYPE_TARGET_TYPE (fieldtype)) != NULL
 332       && strcmp (TYPE_NAME (basetype),
 333                  TYPE_NAME (TYPE_TARGET_TYPE (fieldtype))) == 0)
 334     return 1;
 335   return 0;
 336 }
 337
 338 /* Compute the offset of the baseclass which is the INDEXth baseclass
 339    of class TYPE, for value at VALADDR (in host) at ADDRESS (in
 340    target).  The result is the offset of the baseclass value relative
 341    to (the address of)(ARG) + OFFSET.  */
 342
 343 static int
 344 gnuv2_baseclass_offset (struct type *type, int index,
 345                         const bfd_byte *valaddr, int embedded_offset,
 346                         CORE_ADDR address, const struct value *val)
 347 {
 348   struct type *basetype = TYPE_BASECLASS (type, index);
 349
 350   if (BASETYPE_VIA_VIRTUAL (type, index))
 351     {
 352       /* Must hunt for the pointer to this virtual baseclass.  */
 353       int i, len = TYPE_NFIELDS (type);
 354       int n_baseclasses = TYPE_N_BASECLASSES (type);
 355
 356       /* First look for the virtual baseclass pointer
 357          in the fields.  */
 358       for (i = n_baseclasses; i < len; i++)
 359         {
 360           if (vb_match (type, i, basetype))
 361             {
 362               struct type *field_type;
 363               int field_offset;
 364               int field_length;
 365               CORE_ADDR addr;
 366
 367               field_type = check_typedef (TYPE_FIELD_TYPE (type, i));
 368               field_offset = TYPE_FIELD_BITPOS (type, i) / 8;
 369               field_length = TYPE_LENGTH (field_type);
 370
 371               if (!value_bytes_available (val, embedded_offset + field_offset,
 372                                           field_length))
 373                 throw_error (NOT_AVAILABLE_ERROR,
 374                              _("Virtual baseclass pointer is not available"));
 375
 376               addr = unpack_pointer (field_type,
 377                                      valaddr + embedded_offset + field_offset);
 378
 379               return addr - (LONGEST) address + embedded_offset;
 380             }
 381         }
 382       /* Not in the fields, so try looking through the baseclasses.  */
 383       for (i = index + 1; i < n_baseclasses; i++)
 384         {
 385           /* Don't go through baseclass_offset, as that wraps
 386              exceptions, thus, inner exceptions would be wrapped more
 387              than once.  */
 388           int boffset =
 389             gnuv2_baseclass_offset (type, i, valaddr,
 390                                     embedded_offset, address, val);
 391
 392           if (boffset)
 393             return boffset;
 394         }
 395
 396       error (_("Baseclass offset not found"));
 397     }
 398
 399   /* Baseclass is easily computed.  */
 400   return TYPE_BASECLASS_BITPOS (type, index) / 8;
 401 }
 402
 403 static void
 404 init_gnuv2_ops (void)
 405 {
 406   gnu_v2_abi_ops.shortname = "gnu-v2";
 407   gnu_v2_abi_ops.longname = "GNU G++ Version 2 ABI";
 408   gnu_v2_abi_ops.doc = "G++ Version 2 ABI";
 409   gnu_v2_abi_ops.is_destructor_name = gnuv2_is_destructor_name;
 410   gnu_v2_abi_ops.is_constructor_name = gnuv2_is_constructor_name;
 411   gnu_v2_abi_ops.is_vtable_name = gnuv2_is_vtable_name;
 412   gnu_v2_abi_ops.is_operator_name = gnuv2_is_operator_name;
 413   gnu_v2_abi_ops.virtual_fn_field = gnuv2_virtual_fn_field;
 414   gnu_v2_abi_ops.rtti_type = gnuv2_value_rtti_type;
 415   gnu_v2_abi_ops.baseclass_offset = gnuv2_baseclass_offset;
 416 }
 417
 418 extern initialize_file_ftype _initialize_gnu_v2_abi; /* -Wmissing-prototypes */
 419
 420 void
 421 _initialize_gnu_v2_abi (void)
 422 {
 423   init_gnuv2_ops ();
 424   register_cp_abi (&gnu_v2_abi_ops);
 425 }