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 (value_type (arg1));
  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 (value_type (arg1));
 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 = value_primitive_field (arg1, 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 (value_type (vtbl)->code () == TYPE_CODE_PTR
 136       && value_type (vtbl)->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 (value_type (entry));
 157
 158   if (entry_type->code () == TYPE_CODE_STRUCT)
 159     {
 160       /* Move the `this' pointer according to the virtual function table.  */
 161       set_value_offset (arg1, value_offset (arg1)
 162                         + 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 (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   deprecated_set_value_type (vfn,
 178                              lookup_pointer_type (TYPE_FN_FIELD_TYPE (f, j)));
 179
 180   *arg1p = arg1;
 181   return vfn;
 182 }
 183
 184
 185 static struct type *
 186 gnuv2_value_rtti_type (struct value *v, int *full, LONGEST *top, int *using_enc)
 187 {
 188   struct type *known_type;
 189   struct type *rtti_type;
 190   CORE_ADDR vtbl;
 191   struct bound_minimal_symbol minsym;
 192   char *p;
 193   const char *linkage_name;
 194   struct type *btype;
 195   struct type *known_type_vptr_basetype;
 196   int known_type_vptr_fieldno;
 197
 198   if (full)
 199     *full = 0;
 200   if (top)
 201     *top = -1;
 202   if (using_enc)
 203     *using_enc = 0;
 204
 205   /* Get declared type.  */
 206   known_type = value_type (v);
 207   known_type = check_typedef (known_type);
 208   /* RTTI works only or class objects.  */
 209   if (known_type->code () != TYPE_CODE_STRUCT)
 210     return NULL;
 211
 212   /* Plan on this changing in the future as i get around to setting
 213      the vtables properly for G++ compiled stuff.  Also, I'll be using
 214      the type info functions, which are always right.  Deal with it
 215      until then.  */
 216
 217   /* Try to get the vptr basetype, fieldno.  */
 218   known_type_vptr_fieldno = get_vptr_fieldno (known_type,
 219                                               &known_type_vptr_basetype);
 220
 221   /* If we can't find it, give up.  */
 222   if (known_type_vptr_fieldno < 0)
 223     return NULL;
 224
 225   /* Make sure our basetype and known type match, otherwise, cast
 226      so we can get at the vtable properly.  */
 227   btype = known_type_vptr_basetype;
 228   btype = check_typedef (btype);
 229   if (btype != known_type )
 230     {
 231       v = value_cast (btype, v);
 232       if (using_enc)
 233         *using_enc=1;
 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   if (value_address (value_field (v, known_type_vptr_fieldno)) == 0)
 239     return NULL;
 240
 241   vtbl = value_as_address (value_field (v, known_type_vptr_fieldno));
 242
 243   /* Try to find a symbol that is the vtable.  */
 244   minsym=lookup_minimal_symbol_by_pc(vtbl);
 245   if (minsym.minsym==NULL
 246       || (linkage_name=minsym.minsym->linkage_name ())==NULL
 247       || !is_vtable_name (linkage_name))
 248     return NULL;
 249
 250   /* If we just skip the prefix, we get screwed by namespaces.  */
 251   gdb::unique_xmalloc_ptr<char> demangled_name
 252     = gdb_demangle(linkage_name,DMGL_PARAMS|DMGL_ANSI);
 253   p = strchr (demangled_name.get (), ' ');
 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.get (), 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,
 267                                       TYPE_VPTR_FIELDNO(rtti_type)) / 8;
 268       if (top && ((*top) >0))
 269         {
 270           if (rtti_type->length () > known_type->length ())
 271             {
 272               if (full)
 273                 *full=0;
 274             }
 275           else
 276             {
 277               if (full)
 278                 *full=1;
 279             }
 280         }
 281     }
 282   else
 283     {
 284       if (full)
 285         *full=1;
 286     }
 287
 288   return rtti_type;
 289 }
 290
 291 /* Return true if the INDEXth field of TYPE is a virtual baseclass
 292    pointer which is for the base class whose type is BASECLASS.  */
 293
 294 static int
 295 vb_match (struct type *type, int index, struct type *basetype)
 296 {
 297   struct type *fieldtype;
 298   const char *name = type->field (index).name ();
 299   const char *field_class_name = NULL;
 300
 301   if (*name != '_')
 302     return 0;
 303   /* gcc 2.4 uses _vb$.  */
 304   if (name[1] == 'v' && name[2] == 'b' && is_cplus_marker (name[3]))
 305     field_class_name = name + 4;
 306   /* gcc 2.5 will use __vb_.  */
 307   if (name[1] == '_' && name[2] == 'v' && name[3] == 'b' && name[4] == '_')
 308     field_class_name = name + 5;
 309
 310   if (field_class_name == NULL)
 311     /* This field is not a virtual base class pointer.  */
 312     return 0;
 313
 314   /* It's a virtual baseclass pointer, now we just need to find out whether
 315      it is for this baseclass.  */
 316   fieldtype = type->field (index).type ();
 317   if (fieldtype == NULL
 318       || fieldtype->code () != TYPE_CODE_PTR)
 319     /* "Can't happen".  */
 320     return 0;
 321
 322   /* What we check for is that either the types are equal (needed for
 323      nameless types) or have the same name.  This is ugly, and a more
 324      elegant solution should be devised (which would probably just push
 325      the ugliness into symbol reading unless we change the stabs format).  */
 326   if (fieldtype->target_type () == basetype)
 327     return 1;
 328
 329   if (basetype->name () != NULL
 330       && fieldtype->target_type ()->name () != NULL
 331       && strcmp (basetype->name (),
 332                  fieldtype->target_type ()->name ()) == 0)
 333     return 1;
 334   return 0;
 335 }
 336
 337 /* Compute the offset of the baseclass which is the INDEXth baseclass
 338    of class TYPE, for value at VALADDR (in host) at ADDRESS (in
 339    target).  The result is the offset of the baseclass value relative
 340    to (the address of)(ARG) + OFFSET.  */
 341
 342 static int
 343 gnuv2_baseclass_offset (struct type *type, int index,
 344                         const bfd_byte *valaddr, LONGEST embedded_offset,
 345                         CORE_ADDR address, const struct value *val)
 346 {
 347   struct type *basetype = TYPE_BASECLASS (type, index);
 348
 349   if (BASETYPE_VIA_VIRTUAL (type, index))
 350     {
 351       /* Must hunt for the pointer to this virtual baseclass.  */
 352       int i, len = type->num_fields ();
 353       int n_baseclasses = TYPE_N_BASECLASSES (type);
 354
 355       /* First look for the virtual baseclass pointer
 356          in the fields.  */
 357       for (i = n_baseclasses; i < len; i++)
 358         {
 359           if (vb_match (type, i, basetype))
 360             {
 361               struct type *field_type;
 362               LONGEST field_offset;
 363               int field_length;
 364               CORE_ADDR addr;
 365
 366               field_type = check_typedef (type->field (i).type ());
 367               field_offset = type->field (i).loc_bitpos () / 8;
 368               field_length = field_type->length ();
 369
 370               if (!value_bytes_available (val, embedded_offset + field_offset,
 371                                           field_length))
 372                 throw_error (NOT_AVAILABLE_ERROR,
 373                              _("Virtual baseclass pointer is not available"));
 374
 375               addr = unpack_pointer (field_type,
 376                                      valaddr + embedded_offset + field_offset);
 377
 378               return addr - (LONGEST) address + embedded_offset;
 379             }
 380         }
 381       /* Not in the fields, so try looking through the baseclasses.  */
 382       for (i = index + 1; i < n_baseclasses; i++)
 383         {
 384           /* Don't go through baseclass_offset, as that wraps
 385              exceptions, thus, inner exceptions would be wrapped more
 386              than once.  */
 387           int boffset =
 388             gnuv2_baseclass_offset (type, i, valaddr,
 389                                     embedded_offset, address, val);
 390
 391           if (boffset)
 392             return boffset;
 393         }
 394
 395       error (_("Baseclass offset not found"));
 396     }
 397
 398   /* Baseclass is easily computed.  */
 399   return TYPE_BASECLASS_BITPOS (type, index) / 8;
 400 }
 401
 402 static void
 403 init_gnuv2_ops (void)
 404 {
 405   gnu_v2_abi_ops.shortname = "gnu-v2";
 406   gnu_v2_abi_ops.longname = "GNU G++ Version 2 ABI";
 407   gnu_v2_abi_ops.doc = "G++ Version 2 ABI";
 408   gnu_v2_abi_ops.is_destructor_name = gnuv2_is_destructor_name;
 409   gnu_v2_abi_ops.is_constructor_name = gnuv2_is_constructor_name;
 410   gnu_v2_abi_ops.is_vtable_name = gnuv2_is_vtable_name;
 411   gnu_v2_abi_ops.is_operator_name = gnuv2_is_operator_name;
 412   gnu_v2_abi_ops.virtual_fn_field = gnuv2_virtual_fn_field;
 413   gnu_v2_abi_ops.rtti_type = gnuv2_value_rtti_type;
 414   gnu_v2_abi_ops.baseclass_offset = gnuv2_baseclass_offset;
 415 }
 416
 417 void _initialize_gnu_v2_abi ();
 418 void
 419 _initialize_gnu_v2_abi ()
 420 {
 421   init_gnuv2_ops ();
 422   register_cp_abi (&gnu_v2_abi_ops);
 423 }