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   LONGEST vi = (LONGEST) TYPE_FN_FIELD_VOFFSET (f, j);
 101   struct type *fcontext = TYPE_FN_FIELD_FCONTEXT (f, j);
 102   struct type *context;
 103   struct type *context_vptr_basetype;
 104   int context_vptr_fieldno;
 105
 106   if (fcontext == NULL)
 107     /* We don't have an fcontext (e.g. the program was compiled with
 108        g++ version 1).  Try to get the vtbl from the TYPE_VPTR_BASETYPE.
 109        This won't work right for multiple inheritance, but at least we
 110        should do as well as GDB 3.x did.  */
 111     fcontext = TYPE_VPTR_BASETYPE (type);
 112   context = lookup_pointer_type (fcontext);
 113   /* Now context is a pointer to the basetype containing the vtbl.  */
 114   if (TYPE_TARGET_TYPE (context) != type1)
 115     {
 116       struct value *tmp = value_cast (context, value_addr (arg1));
 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 coreptr;
 190   struct value *vp;
 191   long top_offset = 0;
 192   char rtti_type_name[256];
 193   CORE_ADDR vtbl;
 194   struct minimal_symbol *minsym;
 195   struct symbol *sym;
 196   char *demangled_name, *p;
 197   struct type *btype;
 198   struct type *known_type_vptr_basetype;
 199   int known_type_vptr_fieldno;
 200
 201   if (full)
 202     *full = 0;
 203   if (top)
 204     *top = -1;
 205   if (using_enc)
 206     *using_enc = 0;
 207
 208   /* Get declared type */
 209   known_type = value_type (v);
 210   CHECK_TYPEDEF (known_type);
 211   /* RTTI works only or class objects */
 212   if (TYPE_CODE (known_type) != TYPE_CODE_CLASS)
 213     return NULL;
 214
 215   /* Plan on this changing in the future as i get around to setting
 216      the vtables properly for G++ compiled stuff.  Also, I'll be using
 217      the type info functions, which are always right.  Deal with it
 218      until then.  */
 219
 220   /* Try to get the vptr basetype, fieldno.  */
 221   known_type_vptr_fieldno = get_vptr_fieldno (known_type,
 222                                               &known_type_vptr_basetype);
 223
 224   /* If we can't find it, give up.  */
 225   if (known_type_vptr_fieldno < 0)
 226     return NULL;
 227
 228   /* Make sure our basetype and known type match, otherwise, cast
 229      so we can get at the vtable properly.
 230   */
 231   btype = known_type_vptr_basetype;
 232   CHECK_TYPEDEF (btype);
 233   if (btype != known_type )
 234     {
 235       v = value_cast (btype, v);
 236       if (using_enc)
 237         *using_enc=1;
 238     }
 239   /*
 240     We can't use value_ind here, because it would want to use RTTI, and
 241     we'd waste a bunch of time figuring out we already know the type.
 242     Besides, we don't care about the type, just the actual pointer
 243   */
 244   if (value_address (value_field (v, known_type_vptr_fieldno)) == 0)
 245     return NULL;
 246
 247   vtbl = value_as_address (value_field (v, known_type_vptr_fieldno));
 248
 249   /* Try to find a symbol that is the vtable */
 250   minsym=lookup_minimal_symbol_by_pc(vtbl);
 251   if (minsym==NULL
 252       || (demangled_name=SYMBOL_LINKAGE_NAME (minsym))==NULL
 253       || !is_vtable_name (demangled_name))
 254     return NULL;
 255
 256   /* If we just skip the prefix, we get screwed by namespaces */
 257   demangled_name=cplus_demangle(demangled_name,DMGL_PARAMS|DMGL_ANSI);
 258   p = strchr (demangled_name, ' ');
 259   if (p)
 260     *p = '\0';
 261
 262   /* Lookup the type for the name */
 263   /* FIXME: chastain/2003-11-26: block=NULL is bogus.  See pr gdb/1465. */
 264   rtti_type = cp_lookup_rtti_type (demangled_name, NULL);
 265   if (rtti_type == NULL)
 266     return NULL;
 267
 268   if (TYPE_N_BASECLASSES(rtti_type) > 1 &&  full && (*full) != 1)
 269     {
 270       if (top)
 271         *top=TYPE_BASECLASS_BITPOS(rtti_type,TYPE_VPTR_FIELDNO(rtti_type))/8;
 272       if (top && ((*top) >0))
 273         {
 274           if (TYPE_LENGTH(rtti_type) > TYPE_LENGTH(known_type))
 275             {
 276               if (full)
 277                 *full=0;
 278             }
 279           else
 280             {
 281               if (full)
 282                 *full=1;
 283             }
 284         }
 285     }
 286   else
 287     {
 288       if (full)
 289         *full=1;
 290     }
 291
 292   return rtti_type;
 293 }
 294
 295 /* Return true if the INDEXth field of TYPE is a virtual baseclass
 296    pointer which is for the base class whose type is BASECLASS.  */
 297
 298 static int
 299 vb_match (struct type *type, int index, struct type *basetype)
 300 {
 301   struct type *fieldtype;
 302   char *name = TYPE_FIELD_NAME (type, index);
 303   char *field_class_name = NULL;
 304
 305   if (*name != '_')
 306     return 0;
 307   /* gcc 2.4 uses _vb$.  */
 308   if (name[1] == 'v' && name[2] == 'b' && is_cplus_marker (name[3]))
 309     field_class_name = name + 4;
 310   /* gcc 2.5 will use __vb_.  */
 311   if (name[1] == '_' && name[2] == 'v' && name[3] == 'b' && name[4] == '_')
 312     field_class_name = name + 5;
 313
 314   if (field_class_name == NULL)
 315     /* This field is not a virtual base class pointer.  */
 316     return 0;
 317
 318   /* It's a virtual baseclass pointer, now we just need to find out whether
 319      it is for this baseclass.  */
 320   fieldtype = TYPE_FIELD_TYPE (type, index);
 321   if (fieldtype == NULL
 322       || TYPE_CODE (fieldtype) != TYPE_CODE_PTR)
 323     /* "Can't happen".  */
 324     return 0;
 325
 326   /* What we check for is that either the types are equal (needed for
 327      nameless types) or have the same name.  This is ugly, and a more
 328      elegant solution should be devised (which would probably just push
 329      the ugliness into symbol reading unless we change the stabs format).  */
 330   if (TYPE_TARGET_TYPE (fieldtype) == basetype)
 331     return 1;
 332
 333   if (TYPE_NAME (basetype) != NULL
 334       && TYPE_NAME (TYPE_TARGET_TYPE (fieldtype)) != NULL
 335       && strcmp (TYPE_NAME (basetype),
 336                  TYPE_NAME (TYPE_TARGET_TYPE (fieldtype))) == 0)
 337     return 1;
 338   return 0;
 339 }
 340
 341 /* Compute the offset of the baseclass which is
 342    the INDEXth baseclass of class TYPE,
 343    for value at VALADDR (in host) at ADDRESS (in target).
 344    The result is the offset of the baseclass value relative
 345    to (the address of)(ARG) + OFFSET.
 346
 347    -1 is returned on error. */
 348
 349 int
 350 gnuv2_baseclass_offset (struct type *type, int index,
 351                         const bfd_byte *valaddr, CORE_ADDR address)
 352 {
 353   struct type *basetype = TYPE_BASECLASS (type, index);
 354
 355   if (BASETYPE_VIA_VIRTUAL (type, index))
 356     {
 357       /* Must hunt for the pointer to this virtual baseclass.  */
 358       int i, len = TYPE_NFIELDS (type);
 359       int n_baseclasses = TYPE_N_BASECLASSES (type);
 360
 361       /* First look for the virtual baseclass pointer
 362          in the fields.  */
 363       for (i = n_baseclasses; i < len; i++)
 364         {
 365           if (vb_match (type, i, basetype))
 366             {
 367               CORE_ADDR addr
 368               = unpack_pointer (TYPE_FIELD_TYPE (type, i),
 369                                 valaddr + (TYPE_FIELD_BITPOS (type, i) / 8));
 370
 371               return addr - (LONGEST) address;
 372             }
 373         }
 374       /* Not in the fields, so try looking through the baseclasses.  */
 375       for (i = index + 1; i < n_baseclasses; i++)
 376         {
 377           int boffset =
 378           baseclass_offset (type, i, valaddr, address);
 379           if (boffset)
 380             return boffset;
 381         }
 382       /* Not found.  */
 383       return -1;
 384     }
 385
 386   /* Baseclass is easily computed.  */
 387   return TYPE_BASECLASS_BITPOS (type, index) / 8;
 388 }
 389
 390 static void
 391 init_gnuv2_ops (void)
 392 {
 393   gnu_v2_abi_ops.shortname = "gnu-v2";
 394   gnu_v2_abi_ops.longname = "GNU G++ Version 2 ABI";
 395   gnu_v2_abi_ops.doc = "G++ Version 2 ABI";
 396   gnu_v2_abi_ops.is_destructor_name = gnuv2_is_destructor_name;
 397   gnu_v2_abi_ops.is_constructor_name = gnuv2_is_constructor_name;
 398   gnu_v2_abi_ops.is_vtable_name = gnuv2_is_vtable_name;
 399   gnu_v2_abi_ops.is_operator_name = gnuv2_is_operator_name;
 400   gnu_v2_abi_ops.virtual_fn_field = gnuv2_virtual_fn_field;
 401   gnu_v2_abi_ops.rtti_type = gnuv2_value_rtti_type;
 402   gnu_v2_abi_ops.baseclass_offset = gnuv2_baseclass_offset;
 403 }
 404
 405 extern initialize_file_ftype _initialize_gnu_v2_abi; /* -Wmissing-prototypes */
 406
 407 void
 408 _initialize_gnu_v2_abi (void)
 409 {
 410   init_gnuv2_ops ();
 411   register_cp_abi (&gnu_v2_abi_ops);
 412   set_cp_abi_as_auto_default (gnu_v2_abi_ops.shortname);
 413 }