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
 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 structure. */
 153       vtbl = value_ptradd (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 vtbl;
 190   struct minimal_symbol *minsym;
 191   char *demangled_name, *p;
 192   struct type *btype;
 193   struct type *known_type_vptr_basetype;
 194   int known_type_vptr_fieldno;
 195
 196   if (full)
 197     *full = 0;
 198   if (top)
 199     *top = -1;
 200   if (using_enc)
 201     *using_enc = 0;
 202
 203   /* Get declared type */
 204   known_type = value_type (v);
 205   CHECK_TYPEDEF (known_type);
 206   /* RTTI works only or class objects */
 207   if (TYPE_CODE (known_type) != TYPE_CODE_CLASS)
 208     return NULL;
 209
 210   /* Plan on this changing in the future as i get around to setting
 211      the vtables properly for G++ compiled stuff.  Also, I'll be using
 212      the type info functions, which are always right.  Deal with it
 213      until then.  */
 214
 215   /* Try to get the vptr basetype, fieldno.  */
 216   known_type_vptr_fieldno = get_vptr_fieldno (known_type,
 217                                               &known_type_vptr_basetype);
 218
 219   /* If we can't find it, give up.  */
 220   if (known_type_vptr_fieldno < 0)
 221     return NULL;
 222
 223   /* Make sure our basetype and known type match, otherwise, cast
 224      so we can get at the vtable properly.
 225   */
 226   btype = known_type_vptr_basetype;
 227   CHECK_TYPEDEF (btype);
 228   if (btype != known_type )
 229     {
 230       v = value_cast (btype, v);
 231       if (using_enc)
 232         *using_enc=1;
 233     }
 234   /*
 235     We can't use value_ind here, because it would want to use RTTI, and
 236     we'd waste a bunch of time figuring out we already know the type.
 237     Besides, we don't care about the type, just the actual pointer
 238   */
 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,TYPE_VPTR_FIELDNO(rtti_type))/8;
 267       if (top && ((*top) >0))
 268         {
 269           if (TYPE_LENGTH(rtti_type) > TYPE_LENGTH(known_type))
 270             {
 271               if (full)
 272                 *full=0;
 273             }
 274           else
 275             {
 276               if (full)
 277                 *full=1;
 278             }
 279         }
 280     }
 281   else
 282     {
 283       if (full)
 284         *full=1;
 285     }
 286
 287   return rtti_type;
 288 }
 289
 290 /* Return true if the INDEXth field of TYPE is a virtual baseclass
 291    pointer which is for the base class whose type is BASECLASS.  */
 292
 293 static int
 294 vb_match (struct type *type, int index, struct type *basetype)
 295 {
 296   struct type *fieldtype;
 297   char *name = TYPE_FIELD_NAME (type, index);
 298   char *field_class_name = NULL;
 299
 300   if (*name != '_')
 301     return 0;
 302   /* gcc 2.4 uses _vb$.  */
 303   if (name[1] == 'v' && name[2] == 'b' && is_cplus_marker (name[3]))
 304     field_class_name = name + 4;
 305   /* gcc 2.5 will use __vb_.  */
 306   if (name[1] == '_' && name[2] == 'v' && name[3] == 'b' && name[4] == '_')
 307     field_class_name = name + 5;
 308
 309   if (field_class_name == NULL)
 310     /* This field is not a virtual base class pointer.  */
 311     return 0;
 312
 313   /* It's a virtual baseclass pointer, now we just need to find out whether
 314      it is for this baseclass.  */
 315   fieldtype = TYPE_FIELD_TYPE (type, index);
 316   if (fieldtype == NULL
 317       || TYPE_CODE (fieldtype) != TYPE_CODE_PTR)
 318     /* "Can't happen".  */
 319     return 0;
 320
 321   /* What we check for is that either the types are equal (needed for
 322      nameless types) or have the same name.  This is ugly, and a more
 323      elegant solution should be devised (which would probably just push
 324      the ugliness into symbol reading unless we change the stabs format).  */
 325   if (TYPE_TARGET_TYPE (fieldtype) == basetype)
 326     return 1;
 327
 328   if (TYPE_NAME (basetype) != NULL
 329       && TYPE_NAME (TYPE_TARGET_TYPE (fieldtype)) != NULL
 330       && strcmp (TYPE_NAME (basetype),
 331                  TYPE_NAME (TYPE_TARGET_TYPE (fieldtype))) == 0)
 332     return 1;
 333   return 0;
 334 }
 335
 336 /* Compute the offset of the baseclass which is
 337    the INDEXth baseclass of class TYPE,
 338    for value at VALADDR (in host) at ADDRESS (in target).
 339    The result is the offset of the baseclass value relative
 340    to (the address of)(ARG) + OFFSET.
 341
 342    -1 is returned on error. */
 343
 344 static int
 345 gnuv2_baseclass_offset (struct type *type, int index,
 346                         const bfd_byte *valaddr, CORE_ADDR address)
 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               CORE_ADDR addr
 363                 = unpack_pointer (TYPE_FIELD_TYPE (type, i),
 364                                   valaddr + (TYPE_FIELD_BITPOS (type, i) / 8));
 365
 366               return addr - (LONGEST) address;
 367             }
 368         }
 369       /* Not in the fields, so try looking through the baseclasses.  */
 370       for (i = index + 1; i < n_baseclasses; i++)
 371         {
 372           int boffset =
 373             baseclass_offset (type, i, valaddr, address);
 374
 375           if (boffset)
 376             return boffset;
 377         }
 378       /* Not found.  */
 379       return -1;
 380     }
 381
 382   /* Baseclass is easily computed.  */
 383   return TYPE_BASECLASS_BITPOS (type, index) / 8;
 384 }
 385
 386 static void
 387 init_gnuv2_ops (void)
 388 {
 389   gnu_v2_abi_ops.shortname = "gnu-v2";
 390   gnu_v2_abi_ops.longname = "GNU G++ Version 2 ABI";
 391   gnu_v2_abi_ops.doc = "G++ Version 2 ABI";
 392   gnu_v2_abi_ops.is_destructor_name = gnuv2_is_destructor_name;
 393   gnu_v2_abi_ops.is_constructor_name = gnuv2_is_constructor_name;
 394   gnu_v2_abi_ops.is_vtable_name = gnuv2_is_vtable_name;
 395   gnu_v2_abi_ops.is_operator_name = gnuv2_is_operator_name;
 396   gnu_v2_abi_ops.virtual_fn_field = gnuv2_virtual_fn_field;
 397   gnu_v2_abi_ops.rtti_type = gnuv2_value_rtti_type;
 398   gnu_v2_abi_ops.baseclass_offset = gnuv2_baseclass_offset;
 399 }
 400
 401 extern initialize_file_ftype _initialize_gnu_v2_abi; /* -Wmissing-prototypes */
 402
 403 void
 404 _initialize_gnu_v2_abi (void)
 405 {
 406   init_gnuv2_ops ();
 407   register_cp_abi (&gnu_v2_abi_ops);
 408   set_cp_abi_as_auto_default (gnu_v2_abi_ops.shortname);
 409 }