gdb/gnu-v2-abi.c

   1 /* Abstraction of GNU v2 abi.
   2
   3    Copyright (C) 2001-2023 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 <ctype.h>
  31
  32 static cp_abi_ops gnu_v2_abi_ops;
  33
  34 static int vb_match (struct type *, int, struct type *);
  35
  36 static enum dtor_kinds
  37 gnuv2_is_destructor_name (const char *name)
  38 {
  39   if ((name[0] == '_' && is_cplus_marker (name[1]) && name[2] == '_')
  40       || startswith (name, "__dt__"))
  41     return complete_object_dtor;
  42   else
  43     return (enum dtor_kinds) 0;
  44 }
  45
  46 static enum ctor_kinds
  47 gnuv2_is_constructor_name (const char *name)
  48 {
  49   if ((name[0] == '_' && name[1] == '_'
  50        && (isdigit (name[2]) || strchr ("Qt", name[2])))
  51       || startswith (name, "__ct__"))
  52     return complete_object_ctor;
  53   else
  54     return (enum ctor_kinds) 0;
  55 }
  56
  57 static int
  58 gnuv2_is_vtable_name (const char *name)
  59 {
  60   return (((name)[0] == '_'
  61            && (((name)[1] == 'V' && (name)[2] == 'T')
  62                || ((name)[1] == 'v' && (name)[2] == 't'))
  63            && is_cplus_marker ((name)[3])) ||
  64           ((name)[0] == '_' && (name)[1] == '_'
  65            && (name)[2] == 'v' && (name)[3] == 't' && (name)[4] == '_'));
  66 }
  67
  68 static int
  69 gnuv2_is_operator_name (const char *name)
  70 {
  71   return startswith (name, CP_OPERATOR_STR);
  72 }
  73
  74 \f
  75 /* Return a virtual function as a value.
  76    ARG1 is the object which provides the virtual function
  77    table pointer.  *ARG1P is side-effected in calling this function.
  78    F is the list of member functions which contains the desired virtual
  79    function.
  80    J is an index into F which provides the desired virtual function.
  81
  82    TYPE is the type in which F is located.  */
  83 static struct value *
  84 gnuv2_virtual_fn_field (struct value **arg1p, struct fn_field * f, int j,
  85                         struct type * type, int offset)
  86 {
  87   struct value *arg1 = *arg1p;
  88   struct type *type1 = check_typedef (arg1->type ());
  89   struct type *entry_type;
  90   /* First, get the virtual function table pointer.  That comes
  91      with a strange type, so cast it to type `pointer to long' (which
  92      should serve just fine as a function type).  Then, index into
  93      the table, and convert final value to appropriate function type.  */
  94   struct value *entry;
  95   struct value *vfn;
  96   struct value *vtbl;
  97   LONGEST vi = (LONGEST) TYPE_FN_FIELD_VOFFSET (f, j);
  98   struct type *fcontext = TYPE_FN_FIELD_FCONTEXT (f, j);
  99   struct type *context;
 100   struct type *context_vptr_basetype;
 101   int context_vptr_fieldno;
 102
 103   if (fcontext == NULL)
 104     /* We don't have an fcontext (e.g. the program was compiled with
 105        g++ version 1).  Try to get the vtbl from the TYPE_VPTR_BASETYPE.
 106        This won't work right for multiple inheritance, but at least we
 107        should do as well as GDB 3.x did.  */
 108     fcontext = TYPE_VPTR_BASETYPE (type);
 109   context = lookup_pointer_type (fcontext);
 110   /* Now context is a pointer to the basetype containing the vtbl.  */
 111   if (context->target_type () != type1)
 112     {
 113       struct value *tmp = value_cast (context, value_addr (arg1));
 114
 115       arg1 = value_ind (tmp);
 116       type1 = check_typedef (arg1->type ());
 117     }
 118
 119   context = type1;
 120   /* Now context is the basetype containing the vtbl.  */
 121
 122   /* This type may have been defined before its virtual function table
 123      was.  If so, fill in the virtual function table entry for the
 124      type now.  */
 125   context_vptr_fieldno = get_vptr_fieldno (context, &context_vptr_basetype);
 126   /* FIXME: What to do if vptr_fieldno is still -1?  */
 127
 128   /* The virtual function table is now an array of structures
 129      which have the form { int16 offset, delta; void *pfn; }.  */
 130   vtbl = arg1->primitive_field (0, context_vptr_fieldno,
 131                                 context_vptr_basetype);
 132
 133   /* With older versions of g++, the vtbl field pointed to an array
 134      of structures.  Nowadays it points directly to the structure.  */
 135   if (vtbl->type ()->code () == TYPE_CODE_PTR
 136       && vtbl->type ()->target_type ()->code () == TYPE_CODE_ARRAY)
 137     {
 138       /* Handle the case where the vtbl field points to an
 139          array of structures.  */
 140       vtbl = value_ind (vtbl);
 141
 142       /* Index into the virtual function table.  This is hard-coded because
 143          looking up a field is not cheap, and it may be important to save
 144          time, e.g. if the user has set a conditional breakpoint calling
 145          a virtual function.  */
 146       entry = value_subscript (vtbl, vi);
 147     }
 148   else
 149     {
 150       /* Handle the case where the vtbl field points directly to a
 151          structure.  */
 152       vtbl = value_ptradd (vtbl, vi);
 153       entry = value_ind (vtbl);
 154     }
 155
 156   entry_type = check_typedef (entry->type ());
 157
 158   if (entry_type->code () == TYPE_CODE_STRUCT)
 159     {
 160       /* Move the `this' pointer according to the virtual function table.  */
 161       arg1->set_offset (arg1->offset ()
 162                         + value_as_long (value_field (entry, 0)));
 163
 164       if (!arg1->lazy ())
 165         {
 166           arg1->set_lazy (true);
 167           arg1->fetch_lazy ();
 168         }
 169
 170       vfn = value_field (entry, 2);
 171     }
 172   else if (entry_type->code () == 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   vfn->deprecated_set_type (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, LONGEST *top, int *using_enc)
 186 {
 187   struct type *known_type;
 188   struct type *rtti_type;
 189   CORE_ADDR vtbl;
 190   struct bound_minimal_symbol minsym;
 191   char *p;
 192   const char *linkage_name;
 193   struct type *btype;
 194   struct type *known_type_vptr_basetype;
 195   int known_type_vptr_fieldno;
 196
 197   if (full)
 198     *full = 0;
 199   if (top)
 200     *top = -1;
 201   if (using_enc)
 202     *using_enc = 0;
 203
 204   /* Get declared type.  */
 205   known_type = v->type ();
 206   known_type = check_typedef (known_type);
 207   /* RTTI works only or class objects.  */
 208   if (known_type->code () != TYPE_CODE_STRUCT)
 209     return NULL;
 210
 211   /* Plan on this changing in the future as i get around to setting
 212      the vtables properly for G++ compiled stuff.  Also, I'll be using
 213      the type info functions, which are always right.  Deal with it
 214      until then.  */
 215
 216   /* Try to get the vptr basetype, fieldno.  */
 217   known_type_vptr_fieldno = get_vptr_fieldno (known_type,
 218                                               &known_type_vptr_basetype);
 219
 220   /* If we can't find it, give up.  */
 221   if (known_type_vptr_fieldno < 0)
 222     return NULL;
 223
 224   /* Make sure our basetype and known type match, otherwise, cast
 225      so we can get at the vtable properly.  */
 226   btype = known_type_vptr_basetype;
 227   btype = 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   /* We can't use value_ind here, because it would want to use RTTI, and
 235      we'd waste a bunch of time figuring out we already know the type.
 236      Besides, we don't care about the type, just the actual pointer.  */
 237   if (value_field (v, known_type_vptr_fieldno)->address () == 0)
 238     return NULL;
 239
 240   vtbl = value_as_address (value_field (v, known_type_vptr_fieldno));
 241
 242   /* Try to find a symbol that is the vtable.  */
 243   minsym=lookup_minimal_symbol_by_pc(vtbl);
 244   if (minsym.minsym==NULL
 245       || (linkage_name=minsym.minsym->linkage_name ())==NULL
 246       || !is_vtable_name (linkage_name))
 247     return NULL;
 248
 249   /* If we just skip the prefix, we get screwed by namespaces.  */
 250   gdb::unique_xmalloc_ptr<char> demangled_name
 251     = gdb_demangle(linkage_name,DMGL_PARAMS|DMGL_ANSI);
 252   p = strchr (demangled_name.get (), ' ');
 253   if (p)
 254     *p = '\0';
 255
 256   /* Lookup the type for the name.  */
 257   /* FIXME: chastain/2003-11-26: block=NULL is bogus.  See pr gdb/1465.  */
 258   rtti_type = cp_lookup_rtti_type (demangled_name.get (), NULL);
 259   if (rtti_type == NULL)
 260     return NULL;
 261
 262   if (TYPE_N_BASECLASSES(rtti_type) > 1 &&  full && (*full) != 1)
 263     {
 264       if (top)
 265         *top = TYPE_BASECLASS_BITPOS (rtti_type,
 266                                       TYPE_VPTR_FIELDNO(rtti_type)) / 8;
 267       if (top && ((*top) >0))
 268         {
 269           if (rtti_type->length () > known_type->length ())
 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   const char *name = type->field (index).name ();
 298   const 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 (index).type ();
 316   if (fieldtype == NULL
 317       || fieldtype->code () != 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 (fieldtype->target_type () == basetype)
 326     return 1;
 327
 328   if (basetype->name () != NULL
 329       && fieldtype->target_type ()->name () != NULL
 330       && strcmp (basetype->name (),
 331                  fieldtype->target_type ()->name ()) == 0)
 332     return 1;
 333   return 0;
 334 }
 335
 336 /* Compute the offset of the baseclass which is the INDEXth baseclass
 337    of class TYPE, for value at VALADDR (in host) at ADDRESS (in
 338    target).  The result is the offset of the baseclass value relative
 339    to (the address of)(ARG) + OFFSET.  */
 340
 341 static int
 342 gnuv2_baseclass_offset (struct type *type, int index,
 343                         const bfd_byte *valaddr, LONGEST embedded_offset,
 344                         CORE_ADDR address, const struct value *val)
 345 {
 346   struct type *basetype = TYPE_BASECLASS (type, index);
 347
 348   if (BASETYPE_VIA_VIRTUAL (type, index))
 349     {
 350       /* Must hunt for the pointer to this virtual baseclass.  */
 351       int i, len = type->num_fields ();
 352       int n_baseclasses = TYPE_N_BASECLASSES (type);
 353
 354       /* First look for the virtual baseclass pointer
 355          in the fields.  */
 356       for (i = n_baseclasses; i < len; i++)
 357         {
 358           if (vb_match (type, i, basetype))
 359             {
 360               struct type *field_type;
 361               LONGEST field_offset;
 362               int field_length;
 363               CORE_ADDR addr;
 364
 365               field_type = check_typedef (type->field (i).type ());
 366               field_offset = type->field (i).loc_bitpos () / 8;
 367               field_length = field_type->length ();
 368
 369               if (!val->bytes_available (embedded_offset + field_offset,
 370                                          field_length))
 371                 throw_error (NOT_AVAILABLE_ERROR,
 372                              _("Virtual baseclass pointer is not available"));
 373
 374               addr = unpack_pointer (field_type,
 375                                      valaddr + embedded_offset + field_offset);
 376
 377               return addr - (LONGEST) address + embedded_offset;
 378             }
 379         }
 380       /* Not in the fields, so try looking through the baseclasses.  */
 381       for (i = index + 1; i < n_baseclasses; i++)
 382         {
 383           /* Don't go through baseclass_offset, as that wraps
 384              exceptions, thus, inner exceptions would be wrapped more
 385              than once.  */
 386           int boffset =
 387             gnuv2_baseclass_offset (type, i, valaddr,
 388                                     embedded_offset, address, val);
 389
 390           if (boffset)
 391             return boffset;
 392         }
 393
 394       error (_("Baseclass offset not found"));
 395     }
 396
 397   /* Baseclass is easily computed.  */
 398   return TYPE_BASECLASS_BITPOS (type, index) / 8;
 399 }
 400
 401 static void
 402 init_gnuv2_ops (void)
 403 {
 404   gnu_v2_abi_ops.shortname = "gnu-v2";
 405   gnu_v2_abi_ops.longname = "GNU G++ Version 2 ABI";
 406   gnu_v2_abi_ops.doc = "G++ Version 2 ABI";
 407   gnu_v2_abi_ops.is_destructor_name = gnuv2_is_destructor_name;
 408   gnu_v2_abi_ops.is_constructor_name = gnuv2_is_constructor_name;
 409   gnu_v2_abi_ops.is_vtable_name = gnuv2_is_vtable_name;
 410   gnu_v2_abi_ops.is_operator_name = gnuv2_is_operator_name;
 411   gnu_v2_abi_ops.virtual_fn_field = gnuv2_virtual_fn_field;
 412   gnu_v2_abi_ops.rtti_type = gnuv2_value_rtti_type;
 413   gnu_v2_abi_ops.baseclass_offset = gnuv2_baseclass_offset;
 414 }
 415
 416 void _initialize_gnu_v2_abi ();
 417 void
 418 _initialize_gnu_v2_abi ()
 419 {
 420   init_gnuv2_ops ();
 421   register_cp_abi (&gnu_v2_abi_ops);
 422 }