gdb/gnu-v2-abi.c

   1 /* Abstraction of GNU v2 abi.
   2
   3    Copyright (C) 2001-2024 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 "symtab.h"
  23 #include "gdbtypes.h"
  24 #include "value.h"
  25 #include "demangle.h"
  26 #include "gdb-demangle.h"
  27 #include "cp-abi.h"
  28 #include "cp-support.h"
  29 #include <ctype.h>
  30
  31 static cp_abi_ops gnu_v2_abi_ops;
  32
  33 static int vb_match (struct type *, int, struct type *);
  34
  35 static enum dtor_kinds
  36 gnuv2_is_destructor_name (const char *name)
  37 {
  38   if ((name[0] == '_' && is_cplus_marker (name[1]) && name[2] == '_')
  39       || startswith (name, "__dt__"))
  40     return complete_object_dtor;
  41   else
  42     return (enum dtor_kinds) 0;
  43 }
  44
  45 static enum ctor_kinds
  46 gnuv2_is_constructor_name (const char *name)
  47 {
  48   if ((name[0] == '_' && name[1] == '_'
  49        && (isdigit (name[2]) || strchr ("Qt", name[2])))
  50       || startswith (name, "__ct__"))
  51     return complete_object_ctor;
  52   else
  53     return (enum ctor_kinds) 0;
  54 }
  55
  56 static int
  57 gnuv2_is_vtable_name (const char *name)
  58 {
  59   return (((name)[0] == '_'
  60            && (((name)[1] == 'V' && (name)[2] == 'T')
  61                || ((name)[1] == 'v' && (name)[2] == 't'))
  62            && is_cplus_marker ((name)[3])) ||
  63           ((name)[0] == '_' && (name)[1] == '_'
  64            && (name)[2] == 'v' && (name)[3] == 't' && (name)[4] == '_'));
  65 }
  66
  67 static int
  68 gnuv2_is_operator_name (const char *name)
  69 {
  70   return startswith (name, CP_OPERATOR_STR);
  71 }
  72
  73 \f
  74 /* Return a virtual function as a value.
  75    ARG1 is the object which provides the virtual function
  76    table pointer.  *ARG1P is side-effected in calling this function.
  77    F is the list of member functions which contains the desired virtual
  78    function.
  79    J is an index into F which provides the desired virtual function.
  80
  81    TYPE is the type in which F is located.  */
  82 static struct value *
  83 gnuv2_virtual_fn_field (struct value **arg1p, struct fn_field * f, int j,
  84                         struct type * type, int offset)
  85 {
  86   struct value *arg1 = *arg1p;
  87   struct type *type1 = check_typedef (arg1->type ());
  88   struct type *entry_type;
  89   /* First, get the virtual function table pointer.  That comes
  90      with a strange type, so cast it to type `pointer to long' (which
  91      should serve just fine as a function type).  Then, index into
  92      the table, and convert final value to appropriate function type.  */
  93   struct value *entry;
  94   struct value *vfn;
  95   struct value *vtbl;
  96   LONGEST vi = (LONGEST) TYPE_FN_FIELD_VOFFSET (f, j);
  97   struct type *fcontext = TYPE_FN_FIELD_FCONTEXT (f, j);
  98   struct type *context;
  99   struct type *context_vptr_basetype;
 100   int context_vptr_fieldno;
 101
 102   if (fcontext == NULL)
 103     /* We don't have an fcontext (e.g. the program was compiled with
 104        g++ version 1).  Try to get the vtbl from the TYPE_VPTR_BASETYPE.
 105        This won't work right for multiple inheritance, but at least we
 106        should do as well as GDB 3.x did.  */
 107     fcontext = TYPE_VPTR_BASETYPE (type);
 108   context = lookup_pointer_type (fcontext);
 109   /* Now context is a pointer to the basetype containing the vtbl.  */
 110   if (context->target_type () != type1)
 111     {
 112       struct value *tmp = value_cast (context, value_addr (arg1));
 113
 114       arg1 = value_ind (tmp);
 115       type1 = check_typedef (arg1->type ());
 116     }
 117
 118   context = type1;
 119   /* Now context is the basetype containing the vtbl.  */
 120
 121   /* This type may have been defined before its virtual function table
 122      was.  If so, fill in the virtual function table entry for the
 123      type now.  */
 124   context_vptr_fieldno = get_vptr_fieldno (context, &context_vptr_basetype);
 125   /* FIXME: What to do if vptr_fieldno is still -1?  */
 126
 127   /* The virtual function table is now an array of structures
 128      which have the form { int16 offset, delta; void *pfn; }.  */
 129   vtbl = arg1->primitive_field (0, context_vptr_fieldno,
 130                                 context_vptr_basetype);
 131
 132   /* With older versions of g++, the vtbl field pointed to an array
 133      of structures.  Nowadays it points directly to the structure.  */
 134   if (vtbl->type ()->code () == TYPE_CODE_PTR
 135       && vtbl->type ()->target_type ()->code () == TYPE_CODE_ARRAY)
 136     {
 137       /* Handle the case where the vtbl field points to an
 138          array of structures.  */
 139       vtbl = value_ind (vtbl);
 140
 141       /* Index into the virtual function table.  This is hard-coded because
 142          looking up a field is not cheap, and it may be important to save
 143          time, e.g. if the user has set a conditional breakpoint calling
 144          a virtual function.  */
 145       entry = value_subscript (vtbl, vi);
 146     }
 147   else
 148     {
 149       /* Handle the case where the vtbl field points directly to a
 150          structure.  */
 151       vtbl = value_ptradd (vtbl, vi);
 152       entry = value_ind (vtbl);
 153     }
 154
 155   entry_type = check_typedef (entry->type ());
 156
 157   if (entry_type->code () == TYPE_CODE_STRUCT)
 158     {
 159       /* Move the `this' pointer according to the virtual function table.  */
 160       arg1->set_offset (arg1->offset ()
 161                         + value_as_long (value_field (entry, 0)));
 162
 163       if (!arg1->lazy ())
 164         {
 165           arg1->set_lazy (true);
 166           arg1->fetch_lazy ();
 167         }
 168
 169       vfn = value_field (entry, 2);
 170     }
 171   else if (entry_type->code () == TYPE_CODE_PTR)
 172     vfn = entry;
 173   else
 174     error (_("I'm confused:  virtual function table has bad type"));
 175   /* Reinstantiate the function pointer with the correct type.  */
 176   vfn->deprecated_set_type (lookup_pointer_type (TYPE_FN_FIELD_TYPE (f, j)));
 177
 178   *arg1p = arg1;
 179   return vfn;
 180 }
 181
 182
 183 static struct type *
 184 gnuv2_value_rtti_type (struct value *v, int *full, LONGEST *top, int *using_enc)
 185 {
 186   struct type *known_type;
 187   struct type *rtti_type;
 188   CORE_ADDR vtbl;
 189   char *p;
 190   const char *linkage_name;
 191   struct type *btype;
 192   struct type *known_type_vptr_basetype;
 193   int known_type_vptr_fieldno;
 194
 195   if (full)
 196     *full = 0;
 197   if (top)
 198     *top = -1;
 199   if (using_enc)
 200     *using_enc = 0;
 201
 202   /* Get declared type.  */
 203   known_type = v->type ();
 204   known_type = check_typedef (known_type);
 205   /* RTTI works only or class objects.  */
 206   if (known_type->code () != TYPE_CODE_STRUCT)
 207     return NULL;
 208
 209   /* Plan on this changing in the future as i get around to setting
 210      the vtables properly for G++ compiled stuff.  Also, I'll be using
 211      the type info functions, which are always right.  Deal with it
 212      until then.  */
 213
 214   /* Try to get the vptr basetype, fieldno.  */
 215   known_type_vptr_fieldno = get_vptr_fieldno (known_type,
 216                                               &known_type_vptr_basetype);
 217
 218   /* If we can't find it, give up.  */
 219   if (known_type_vptr_fieldno < 0)
 220     return NULL;
 221
 222   /* Make sure our basetype and known type match, otherwise, cast
 223      so we can get at the vtable properly.  */
 224   btype = known_type_vptr_basetype;
 225   btype = check_typedef (btype);
 226   if (btype != known_type )
 227     {
 228       v = value_cast (btype, v);
 229       if (using_enc)
 230         *using_enc=1;
 231     }
 232   /* We can't use value_ind here, because it would want to use RTTI, and
 233      we'd waste a bunch of time figuring out we already know the type.
 234      Besides, we don't care about the type, just the actual pointer.  */
 235   if (value_field (v, known_type_vptr_fieldno)->address () == 0)
 236     return NULL;
 237
 238   vtbl = value_as_address (value_field (v, known_type_vptr_fieldno));
 239
 240   /* Try to find a symbol that is the vtable.  */
 241   bound_minimal_symbol minsym = lookup_minimal_symbol_by_pc (vtbl);
 242   if (minsym.minsym==NULL
 243       || (linkage_name=minsym.minsym->linkage_name ())==NULL
 244       || !is_vtable_name (linkage_name))
 245     return NULL;
 246
 247   /* If we just skip the prefix, we get screwed by namespaces.  */
 248   gdb::unique_xmalloc_ptr<char> demangled_name
 249     = gdb_demangle(linkage_name,DMGL_PARAMS|DMGL_ANSI);
 250   p = strchr (demangled_name.get (), ' ');
 251   if (p)
 252     *p = '\0';
 253
 254   /* Lookup the type for the name.  */
 255   /* FIXME: chastain/2003-11-26: block=NULL is bogus.  See pr gdb/1465.  */
 256   rtti_type = cp_lookup_rtti_type (demangled_name.get (), NULL);
 257   if (rtti_type == NULL)
 258     return NULL;
 259
 260   if (TYPE_N_BASECLASSES(rtti_type) > 1 &&  full && (*full) != 1)
 261     {
 262       if (top)
 263         *top = TYPE_BASECLASS_BITPOS (rtti_type,
 264                                       TYPE_VPTR_FIELDNO(rtti_type)) / 8;
 265       if (top && ((*top) >0))
 266         {
 267           if (rtti_type->length () > known_type->length ())
 268             {
 269               if (full)
 270                 *full=0;
 271             }
 272           else
 273             {
 274               if (full)
 275                 *full=1;
 276             }
 277         }
 278     }
 279   else
 280     {
 281       if (full)
 282         *full=1;
 283     }
 284
 285   return rtti_type;
 286 }
 287
 288 /* Return true if the INDEXth field of TYPE is a virtual baseclass
 289    pointer which is for the base class whose type is BASECLASS.  */
 290
 291 static int
 292 vb_match (struct type *type, int index, struct type *basetype)
 293 {
 294   struct type *fieldtype;
 295   const char *name = type->field (index).name ();
 296   const char *field_class_name = NULL;
 297
 298   if (*name != '_')
 299     return 0;
 300   /* gcc 2.4 uses _vb$.  */
 301   if (name[1] == 'v' && name[2] == 'b' && is_cplus_marker (name[3]))
 302     field_class_name = name + 4;
 303   /* gcc 2.5 will use __vb_.  */
 304   if (name[1] == '_' && name[2] == 'v' && name[3] == 'b' && name[4] == '_')
 305     field_class_name = name + 5;
 306
 307   if (field_class_name == NULL)
 308     /* This field is not a virtual base class pointer.  */
 309     return 0;
 310
 311   /* It's a virtual baseclass pointer, now we just need to find out whether
 312      it is for this baseclass.  */
 313   fieldtype = type->field (index).type ();
 314   if (fieldtype == NULL
 315       || fieldtype->code () != TYPE_CODE_PTR)
 316     /* "Can't happen".  */
 317     return 0;
 318
 319   /* What we check for is that either the types are equal (needed for
 320      nameless types) or have the same name.  This is ugly, and a more
 321      elegant solution should be devised (which would probably just push
 322      the ugliness into symbol reading unless we change the stabs format).  */
 323   if (fieldtype->target_type () == basetype)
 324     return 1;
 325
 326   if (basetype->name () != NULL
 327       && fieldtype->target_type ()->name () != NULL
 328       && strcmp (basetype->name (),
 329                  fieldtype->target_type ()->name ()) == 0)
 330     return 1;
 331   return 0;
 332 }
 333
 334 /* Compute the offset of the baseclass which is the INDEXth baseclass
 335    of class TYPE, for value at VALADDR (in host) at ADDRESS (in
 336    target).  The result is the offset of the baseclass value relative
 337    to (the address of)(ARG) + OFFSET.  */
 338
 339 static int
 340 gnuv2_baseclass_offset (struct type *type, int index,
 341                         const bfd_byte *valaddr, LONGEST embedded_offset,
 342                         CORE_ADDR address, const struct value *val)
 343 {
 344   struct type *basetype = TYPE_BASECLASS (type, index);
 345
 346   if (BASETYPE_VIA_VIRTUAL (type, index))
 347     {
 348       /* Must hunt for the pointer to this virtual baseclass.  */
 349       int i, len = type->num_fields ();
 350       int n_baseclasses = TYPE_N_BASECLASSES (type);
 351
 352       /* First look for the virtual baseclass pointer
 353          in the fields.  */
 354       for (i = n_baseclasses; i < len; i++)
 355         {
 356           if (vb_match (type, i, basetype))
 357             {
 358               struct type *field_type;
 359               LONGEST field_offset;
 360               int field_length;
 361               CORE_ADDR addr;
 362
 363               field_type = check_typedef (type->field (i).type ());
 364               field_offset = type->field (i).loc_bitpos () / 8;
 365               field_length = field_type->length ();
 366
 367               if (!val->bytes_available (embedded_offset + field_offset,
 368                                          field_length))
 369                 throw_error (NOT_AVAILABLE_ERROR,
 370                              _("Virtual baseclass pointer is not available"));
 371
 372               addr = unpack_pointer (field_type,
 373                                      valaddr + embedded_offset + field_offset);
 374
 375               return addr - (LONGEST) address + embedded_offset;
 376             }
 377         }
 378       /* Not in the fields, so try looking through the baseclasses.  */
 379       for (i = index + 1; i < n_baseclasses; i++)
 380         {
 381           /* Don't go through baseclass_offset, as that wraps
 382              exceptions, thus, inner exceptions would be wrapped more
 383              than once.  */
 384           int boffset =
 385             gnuv2_baseclass_offset (type, i, valaddr,
 386                                     embedded_offset, address, val);
 387
 388           if (boffset)
 389             return boffset;
 390         }
 391
 392       error (_("Baseclass offset not found"));
 393     }
 394
 395   /* Baseclass is easily computed.  */
 396   return TYPE_BASECLASS_BITPOS (type, index) / 8;
 397 }
 398
 399 static void
 400 init_gnuv2_ops (void)
 401 {
 402   gnu_v2_abi_ops.shortname = "gnu-v2";
 403   gnu_v2_abi_ops.longname = "GNU G++ Version 2 ABI";
 404   gnu_v2_abi_ops.doc = "G++ Version 2 ABI";
 405   gnu_v2_abi_ops.is_destructor_name = gnuv2_is_destructor_name;
 406   gnu_v2_abi_ops.is_constructor_name = gnuv2_is_constructor_name;
 407   gnu_v2_abi_ops.is_vtable_name = gnuv2_is_vtable_name;
 408   gnu_v2_abi_ops.is_operator_name = gnuv2_is_operator_name;
 409   gnu_v2_abi_ops.virtual_fn_field = gnuv2_virtual_fn_field;
 410   gnu_v2_abi_ops.rtti_type = gnuv2_value_rtti_type;
 411   gnu_v2_abi_ops.baseclass_offset = gnuv2_baseclass_offset;
 412 }
 413
 414 void _initialize_gnu_v2_abi ();
 415 void
 416 _initialize_gnu_v2_abi ()
 417 {
 418   init_gnuv2_ops ();
 419   register_cp_abi (&gnu_v2_abi_ops);
 420 }