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       arg1 = value_ind (tmp);
 117       type1 = check_typedef (value_type (arg1));
 118     }
 119
 120   context = type1;
 121   /* Now context is the basetype containing the vtbl.  */
 122
 123   /* This type may have been defined before its virtual function table
 124      was.  If so, fill in the virtual function table entry for the
 125      type now.  */
 126   context_vptr_fieldno = get_vptr_fieldno (context, &context_vptr_basetype);
 127   /* FIXME: What to do if vptr_fieldno is still -1?  */
 128
 129   /* The virtual function table is now an array of structures
 130      which have the form { int16 offset, delta; void *pfn; }.  */
 131   vtbl = value_primitive_field (arg1, 0, context_vptr_fieldno,
 132                                 context_vptr_basetype);
 133
 134   /* With older versions of g++, the vtbl field pointed to an array
 135      of structures.  Nowadays it points directly to the structure. */
 136   if (TYPE_CODE (value_type (vtbl)) == TYPE_CODE_PTR
 137       && TYPE_CODE (TYPE_TARGET_TYPE (value_type (vtbl))) == TYPE_CODE_ARRAY)
 138     {
 139       /* Handle the case where the vtbl field points to an
 140          array of structures. */
 141       vtbl = value_ind (vtbl);
 142
 143       /* Index into the virtual function table.  This is hard-coded because
 144          looking up a field is not cheap, and it may be important to save
 145          time, e.g. if the user has set a conditional breakpoint calling
 146          a virtual function.  */
 147       entry = value_subscript (vtbl, vi);
 148     }
 149   else
 150     {
 151       /* Handle the case where the vtbl field points directly to a 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 (TYPE_CODE (entry_type) == TYPE_CODE_STRUCT)
 159     {
 160       /* Move the `this' pointer according to the virtual function table. */
 161       set_value_offset (arg1, value_offset (arg1) + value_as_long (value_field (entry, 0)));
 162
 163       if (!value_lazy (arg1))
 164         {
 165           set_value_lazy (arg1, 1);
 166           value_fetch_lazy (arg1);
 167         }
 168
 169       vfn = value_field (entry, 2);
 170     }
 171   else if (TYPE_CODE (entry_type) == 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   deprecated_set_value_type (vfn, 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, int *top, int *using_enc)
 185 {
 186   struct type *known_type;
 187   struct type *rtti_type;
 188   CORE_ADDR vtbl;
 189   struct minimal_symbol *minsym;
 190   char *demangled_name, *p;
 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 = value_type (v);
 204   CHECK_TYPEDEF (known_type);
 205   /* RTTI works only or class objects */
 206   if (TYPE_CODE (known_type) != TYPE_CODE_CLASS)
 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   */
 225   btype = known_type_vptr_basetype;
 226   CHECK_TYPEDEF (btype);
 227   if (btype != known_type )
 228     {
 229       v = value_cast (btype, v);
 230       if (using_enc)
 231         *using_enc=1;
 232     }
 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   */
 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==NULL
 246       || (demangled_name=SYMBOL_LINKAGE_NAME (minsym))==NULL
 247       || !is_vtable_name (demangled_name))
 248     return NULL;
 249
 250   /* If we just skip the prefix, we get screwed by namespaces */
 251   demangled_name=cplus_demangle(demangled_name,DMGL_PARAMS|DMGL_ANSI);
 252   p = strchr (demangled_name, ' ');
 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, 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,TYPE_VPTR_FIELDNO(rtti_type))/8;
 266       if (top && ((*top) >0))
 267         {
 268           if (TYPE_LENGTH(rtti_type) > TYPE_LENGTH(known_type))
 269             {
 270               if (full)
 271                 *full=0;
 272             }
 273           else
 274             {
 275               if (full)
 276                 *full=1;
 277             }
 278         }
 279     }
 280   else
 281     {
 282       if (full)
 283         *full=1;
 284     }
 285
 286   return rtti_type;
 287 }
 288
 289 /* Return true if the INDEXth field of TYPE is a virtual baseclass
 290    pointer which is for the base class whose type is BASECLASS.  */
 291
 292 static int
 293 vb_match (struct type *type, int index, struct type *basetype)
 294 {
 295   struct type *fieldtype;
 296   char *name = TYPE_FIELD_NAME (type, index);
 297   char *field_class_name = NULL;
 298
 299   if (*name != '_')
 300     return 0;
 301   /* gcc 2.4 uses _vb$.  */
 302   if (name[1] == 'v' && name[2] == 'b' && is_cplus_marker (name[3]))
 303     field_class_name = name + 4;
 304   /* gcc 2.5 will use __vb_.  */
 305   if (name[1] == '_' && name[2] == 'v' && name[3] == 'b' && name[4] == '_')
 306     field_class_name = name + 5;
 307
 308   if (field_class_name == NULL)
 309     /* This field is not a virtual base class pointer.  */
 310     return 0;
 311
 312   /* It's a virtual baseclass pointer, now we just need to find out whether
 313      it is for this baseclass.  */
 314   fieldtype = TYPE_FIELD_TYPE (type, index);
 315   if (fieldtype == NULL
 316       || TYPE_CODE (fieldtype) != TYPE_CODE_PTR)
 317     /* "Can't happen".  */
 318     return 0;
 319
 320   /* What we check for is that either the types are equal (needed for
 321      nameless types) or have the same name.  This is ugly, and a more
 322      elegant solution should be devised (which would probably just push
 323      the ugliness into symbol reading unless we change the stabs format).  */
 324   if (TYPE_TARGET_TYPE (fieldtype) == basetype)
 325     return 1;
 326
 327   if (TYPE_NAME (basetype) != NULL
 328       && TYPE_NAME (TYPE_TARGET_TYPE (fieldtype)) != NULL
 329       && strcmp (TYPE_NAME (basetype),
 330                  TYPE_NAME (TYPE_TARGET_TYPE (fieldtype))) == 0)
 331     return 1;
 332   return 0;
 333 }
 334
 335 /* Compute the offset of the baseclass which is
 336    the INDEXth baseclass of class TYPE,
 337    for value at VALADDR (in host) at ADDRESS (in target).
 338    The result is the offset of the baseclass value relative
 339    to (the address of)(ARG) + OFFSET.
 340
 341    -1 is returned on error. */
 342
 343 static int
 344 gnuv2_baseclass_offset (struct type *type, int index,
 345                         const bfd_byte *valaddr, CORE_ADDR address)
 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_NFIELDS (type);
 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               CORE_ADDR addr
 362               = unpack_pointer (TYPE_FIELD_TYPE (type, i),
 363                                 valaddr + (TYPE_FIELD_BITPOS (type, i) / 8));
 364
 365               return addr - (LONGEST) address;
 366             }
 367         }
 368       /* Not in the fields, so try looking through the baseclasses.  */
 369       for (i = index + 1; i < n_baseclasses; i++)
 370         {
 371           int boffset =
 372           baseclass_offset (type, i, valaddr, address);
 373           if (boffset)
 374             return boffset;
 375         }
 376       /* Not found.  */
 377       return -1;
 378     }
 379
 380   /* Baseclass is easily computed.  */
 381   return TYPE_BASECLASS_BITPOS (type, index) / 8;
 382 }
 383
 384 static void
 385 init_gnuv2_ops (void)
 386 {
 387   gnu_v2_abi_ops.shortname = "gnu-v2";
 388   gnu_v2_abi_ops.longname = "GNU G++ Version 2 ABI";
 389   gnu_v2_abi_ops.doc = "G++ Version 2 ABI";
 390   gnu_v2_abi_ops.is_destructor_name = gnuv2_is_destructor_name;
 391   gnu_v2_abi_ops.is_constructor_name = gnuv2_is_constructor_name;
 392   gnu_v2_abi_ops.is_vtable_name = gnuv2_is_vtable_name;
 393   gnu_v2_abi_ops.is_operator_name = gnuv2_is_operator_name;
 394   gnu_v2_abi_ops.virtual_fn_field = gnuv2_virtual_fn_field;
 395   gnu_v2_abi_ops.rtti_type = gnuv2_value_rtti_type;
 396   gnu_v2_abi_ops.baseclass_offset = gnuv2_baseclass_offset;
 397 }
 398
 399 extern initialize_file_ftype _initialize_gnu_v2_abi; /* -Wmissing-prototypes */
 400
 401 void
 402 _initialize_gnu_v2_abi (void)
 403 {
 404   init_gnuv2_ops ();
 405   register_cp_abi (&gnu_v2_abi_ops);
 406   set_cp_abi_as_auto_default (gnu_v2_abi_ops.shortname);
 407 }