gdb/cp-valprint.c

   1 /* Support for printing C++ values for GDB, the GNU debugger.
   2
   3    Copyright (C) 1986, 1988, 1989, 1991, 1992, 1993, 1994, 1995, 1996, 1997,
   4    2000, 2001, 2002, 2003, 2005, 2006, 2007, 2008, 2009
   5    Free Software Foundation, Inc.
   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 "gdb_obstack.h"
  24 #include "symtab.h"
  25 #include "gdbtypes.h"
  26 #include "expression.h"
  27 #include "value.h"
  28 #include "command.h"
  29 #include "gdbcmd.h"
  30 #include "demangle.h"
  31 #include "annotate.h"
  32 #include "gdb_string.h"
  33 #include "c-lang.h"
  34 #include "target.h"
  35 #include "cp-abi.h"
  36 #include "valprint.h"
  37 #include "cp-support.h"
  38 #include "language.h"
  39 #include "python/python.h"
  40
  41 /* Controls printing of vtbl's */
  42 static void
  43 show_vtblprint (struct ui_file *file, int from_tty,
  44                 struct cmd_list_element *c, const char *value)
  45 {
  46   fprintf_filtered (file, _("\
  47 Printing of C++ virtual function tables is %s.\n"),
  48                     value);
  49 }
  50
  51 /* Controls looking up an object's derived type using what we find in
  52    its vtables.  */
  53 static void
  54 show_objectprint (struct ui_file *file, int from_tty,
  55                   struct cmd_list_element *c,
  56                   const char *value)
  57 {
  58   fprintf_filtered (file, _("\
  59 Printing of object's derived type based on vtable info is %s.\n"),
  60                     value);
  61 }
  62
  63 static void
  64 show_static_field_print (struct ui_file *file, int from_tty,
  65                          struct cmd_list_element *c, const char *value)
  66 {
  67   fprintf_filtered (file, _("Printing of C++ static members is %s.\n"),
  68                     value);
  69 }
  70
  71
  72 static struct obstack dont_print_vb_obstack;
  73 static struct obstack dont_print_statmem_obstack;
  74
  75 extern void _initialize_cp_valprint (void);
  76
  77 static void cp_print_static_field (struct type *, struct value *,
  78                                    struct ui_file *, int,
  79                                    const struct value_print_options *);
  80
  81 static void cp_print_value (struct type *, struct type *, const gdb_byte *,
  82                             int, CORE_ADDR, struct ui_file *, int,
  83                             const struct value_print_options *, struct type **);
  84
  85
  86 /* GCC versions after 2.4.5 use this.  */
  87 const char vtbl_ptr_name[] = "__vtbl_ptr_type";
  88
  89 /* Return truth value for assertion that TYPE is of the type
  90    "pointer to virtual function".  */
  91
  92 int
  93 cp_is_vtbl_ptr_type (struct type *type)
  94 {
  95   char *typename = type_name_no_tag (type);
  96
  97   return (typename != NULL && !strcmp (typename, vtbl_ptr_name));
  98 }
  99
 100 /* Return truth value for the assertion that TYPE is of the type
 101    "pointer to virtual function table".  */
 102
 103 int
 104 cp_is_vtbl_member (struct type *type)
 105 {
 106   /* With older versions of g++, the vtbl field pointed to an array
 107      of structures.  Nowadays it points directly to the structure. */
 108   if (TYPE_CODE (type) == TYPE_CODE_PTR)
 109     {
 110       type = TYPE_TARGET_TYPE (type);
 111       if (TYPE_CODE (type) == TYPE_CODE_ARRAY)
 112         {
 113           type = TYPE_TARGET_TYPE (type);
 114           if (TYPE_CODE (type) == TYPE_CODE_STRUCT      /* if not using thunks */
 115               || TYPE_CODE (type) == TYPE_CODE_PTR)     /* if using thunks */
 116             {
 117               /* Virtual functions tables are full of pointers
 118                  to virtual functions. */
 119               return cp_is_vtbl_ptr_type (type);
 120             }
 121         }
 122       else if (TYPE_CODE (type) == TYPE_CODE_STRUCT)  /* if not using thunks */
 123         {
 124           return cp_is_vtbl_ptr_type (type);
 125         }
 126       else if (TYPE_CODE (type) == TYPE_CODE_PTR)     /* if using thunks */
 127         {
 128           /* The type name of the thunk pointer is NULL when using dwarf2.
 129              We could test for a pointer to a function, but there is
 130              no type info for the virtual table either, so it wont help.  */
 131           return cp_is_vtbl_ptr_type (type);
 132         }
 133     }
 134   return 0;
 135 }
 136
 137 /* Mutually recursive subroutines of cp_print_value and c_val_print to
 138    print out a structure's fields: cp_print_value_fields and cp_print_value.
 139
 140    TYPE, VALADDR, ADDRESS, STREAM, RECURSE, and OPTIONS have the
 141    same meanings as in cp_print_value and c_val_print.
 142
 143    2nd argument REAL_TYPE is used to carry over the type of the derived
 144    class across the recursion to base classes.
 145
 146    DONT_PRINT is an array of baseclass types that we
 147    should not print, or zero if called from top level.  */
 148
 149 void
 150 cp_print_value_fields (struct type *type, struct type *real_type,
 151                        const gdb_byte *valaddr, int offset, CORE_ADDR address,
 152                        struct ui_file *stream, int recurse,
 153                        const struct value_print_options *options,
 154                        struct type **dont_print_vb, int dont_print_statmem)
 155 {
 156   int i, len, n_baseclasses;
 157   char *last_dont_print = obstack_next_free (&dont_print_statmem_obstack);
 158   int fields_seen = 0;
 159
 160   CHECK_TYPEDEF (type);
 161
 162   fprintf_filtered (stream, "{");
 163   len = TYPE_NFIELDS (type);
 164   n_baseclasses = TYPE_N_BASECLASSES (type);
 165
 166   /* First, print out baseclasses such that we don't print
 167      duplicates of virtual baseclasses.  */
 168
 169   if (n_baseclasses > 0)
 170     cp_print_value (type, real_type, valaddr, offset, address, stream,
 171                     recurse + 1, options, dont_print_vb);
 172
 173   /* Second, print out data fields */
 174
 175   /* If there are no data fields, skip this part */
 176   if (len == n_baseclasses || !len)
 177     fprintf_filtered (stream, "<No data fields>");
 178   else
 179     {
 180       struct obstack tmp_obstack = dont_print_statmem_obstack;
 181
 182       if (dont_print_statmem == 0)
 183         {
 184           /* If we're at top level, carve out a completely fresh
 185              chunk of the obstack and use that until this particular
 186              invocation returns.  */
 187           obstack_finish (&dont_print_statmem_obstack);
 188         }
 189
 190       for (i = n_baseclasses; i < len; i++)
 191         {
 192           /* If requested, skip printing of static fields.  */
 193           if (!options->static_field_print
 194               && field_is_static (&TYPE_FIELD (type, i)))
 195             continue;
 196
 197           if (fields_seen)
 198             fprintf_filtered (stream, ", ");
 199           else if (n_baseclasses > 0)
 200             {
 201               if (options->pretty)
 202                 {
 203                   fprintf_filtered (stream, "\n");
 204                   print_spaces_filtered (2 + 2 * recurse, stream);
 205                   fputs_filtered ("members of ", stream);
 206                   fputs_filtered (type_name_no_tag (type), stream);
 207                   fputs_filtered (": ", stream);
 208                 }
 209             }
 210           fields_seen = 1;
 211
 212           if (options->pretty)
 213             {
 214               fprintf_filtered (stream, "\n");
 215               print_spaces_filtered (2 + 2 * recurse, stream);
 216             }
 217           else
 218             {
 219               wrap_here (n_spaces (2 + 2 * recurse));
 220             }
 221           if (options->inspect_it)
 222             {
 223               if (TYPE_CODE (TYPE_FIELD_TYPE (type, i)) == TYPE_CODE_PTR)
 224                 fputs_filtered ("\"( ptr \"", stream);
 225               else
 226                 fputs_filtered ("\"( nodef \"", stream);
 227               if (field_is_static (&TYPE_FIELD (type, i)))
 228                 fputs_filtered ("static ", stream);
 229               fprintf_symbol_filtered (stream, TYPE_FIELD_NAME (type, i),
 230                                        current_language->la_language,
 231                                        DMGL_PARAMS | DMGL_ANSI);
 232               fputs_filtered ("\" \"", stream);
 233               fprintf_symbol_filtered (stream, TYPE_FIELD_NAME (type, i),
 234                                        current_language->la_language,
 235                                        DMGL_PARAMS | DMGL_ANSI);
 236               fputs_filtered ("\") \"", stream);
 237             }
 238           else
 239             {
 240               annotate_field_begin (TYPE_FIELD_TYPE (type, i));
 241
 242               if (field_is_static (&TYPE_FIELD (type, i)))
 243                 fputs_filtered ("static ", stream);
 244               fprintf_symbol_filtered (stream, TYPE_FIELD_NAME (type, i),
 245                                        current_language->la_language,
 246                                        DMGL_PARAMS | DMGL_ANSI);
 247               annotate_field_name_end ();
 248               /* do not print leading '=' in case of anonymous unions */
 249               if (strcmp (TYPE_FIELD_NAME (type, i), ""))
 250                 fputs_filtered (" = ", stream);
 251               annotate_field_value ();
 252             }
 253
 254           if (!field_is_static (&TYPE_FIELD (type, i))
 255               && TYPE_FIELD_PACKED (type, i))
 256             {
 257               struct value *v;
 258
 259               /* Bitfields require special handling, especially due to byte
 260                  order problems.  */
 261               if (TYPE_FIELD_IGNORE (type, i))
 262                 {
 263                   fputs_filtered ("<optimized out or zero length>", stream);
 264                 }
 265               else
 266                 {
 267                   struct value_print_options opts = *options;
 268                   opts.deref_ref = 0;
 269                   v = value_from_longest
 270                     (TYPE_FIELD_TYPE (type, i),
 271                      unpack_field_as_long (type, valaddr + offset, i));
 272
 273                   common_val_print (v, stream, recurse + 1, &opts,
 274                                     current_language);
 275                 }
 276             }
 277           else
 278             {
 279               if (TYPE_FIELD_IGNORE (type, i))
 280                 {
 281                   fputs_filtered ("<optimized out or zero length>", stream);
 282                 }
 283               else if (field_is_static (&TYPE_FIELD (type, i)))
 284                 {
 285                   struct value *v = value_static_field (type, i);
 286                   if (v == NULL)
 287                     fputs_filtered ("<optimized out>", stream);
 288                   else
 289                     cp_print_static_field (TYPE_FIELD_TYPE (type, i), v,
 290                                            stream, recurse + 1, options);
 291                 }
 292               else
 293                 {
 294                   struct value_print_options opts = *options;
 295                   opts.deref_ref = 0;
 296                   val_print (TYPE_FIELD_TYPE (type, i),
 297                              valaddr, offset + TYPE_FIELD_BITPOS (type, i) / 8,
 298                              address + TYPE_FIELD_BITPOS (type, i) / 8,
 299                              stream, recurse + 1, &opts,
 300                              current_language);
 301                 }
 302             }
 303           annotate_field_end ();
 304         }
 305
 306       if (dont_print_statmem == 0)
 307         {
 308           /* Free the space used to deal with the printing
 309              of the members from top level.  */
 310           obstack_free (&dont_print_statmem_obstack, last_dont_print);
 311           dont_print_statmem_obstack = tmp_obstack;
 312         }
 313
 314       if (options->pretty)
 315         {
 316           fprintf_filtered (stream, "\n");
 317           print_spaces_filtered (2 * recurse, stream);
 318         }
 319     }                           /* if there are data fields */
 320
 321   fprintf_filtered (stream, "}");
 322 }
 323
 324 /* Special val_print routine to avoid printing multiple copies of virtual
 325    baseclasses.  */
 326
 327 static void
 328 cp_print_value (struct type *type, struct type *real_type,
 329                 const gdb_byte *valaddr, int offset, CORE_ADDR address,
 330                 struct ui_file *stream, int recurse,
 331                 const struct value_print_options *options,
 332                 struct type **dont_print_vb)
 333 {
 334   struct type **last_dont_print
 335     = (struct type **) obstack_next_free (&dont_print_vb_obstack);
 336   struct obstack tmp_obstack = dont_print_vb_obstack;
 337   int i, n_baseclasses = TYPE_N_BASECLASSES (type);
 338   int thisoffset;
 339   struct type *thistype;
 340
 341   if (dont_print_vb == 0)
 342     {
 343       /* If we're at top level, carve out a completely fresh
 344          chunk of the obstack and use that until this particular
 345          invocation returns.  */
 346       /* Bump up the high-water mark.  Now alpha is omega.  */
 347       obstack_finish (&dont_print_vb_obstack);
 348     }
 349
 350   for (i = 0; i < n_baseclasses; i++)
 351     {
 352       int boffset;
 353       int skip;
 354       struct type *baseclass = check_typedef (TYPE_BASECLASS (type, i));
 355       char *basename = TYPE_NAME (baseclass);
 356       const gdb_byte *base_valaddr;
 357
 358       if (BASETYPE_VIA_VIRTUAL (type, i))
 359         {
 360           struct type **first_dont_print
 361             = (struct type **) obstack_base (&dont_print_vb_obstack);
 362
 363           int j = (struct type **) obstack_next_free (&dont_print_vb_obstack)
 364             - first_dont_print;
 365
 366           while (--j >= 0)
 367             if (baseclass == first_dont_print[j])
 368               goto flush_it;
 369
 370           obstack_ptr_grow (&dont_print_vb_obstack, baseclass);
 371         }
 372
 373       thisoffset = offset;
 374       thistype = real_type;
 375
 376       boffset = baseclass_offset (type, i, valaddr + offset, address);
 377       skip = ((boffset == -1) || (boffset + offset) < 0) ? 1 : -1;
 378
 379       if (BASETYPE_VIA_VIRTUAL (type, i))
 380         {
 381           /* The virtual base class pointer might have been
 382              clobbered by the user program. Make sure that it
 383              still points to a valid memory location.  */
 384
 385           if (boffset != -1
 386               && ((boffset + offset) < 0
 387                   || (boffset + offset) >= TYPE_LENGTH (type)))
 388             {
 389               /* FIXME (alloca): unsafe if baseclass is really really large. */
 390               gdb_byte *buf = alloca (TYPE_LENGTH (baseclass));
 391               base_valaddr = buf;
 392               if (target_read_memory (address + boffset, buf,
 393                                       TYPE_LENGTH (baseclass)) != 0)
 394                 skip = 1;
 395               address = address + boffset;
 396               thisoffset = 0;
 397               boffset = 0;
 398               thistype = baseclass;
 399             }
 400           else
 401             base_valaddr = valaddr;
 402         }
 403       else
 404         base_valaddr = valaddr;
 405
 406       /* now do the printing */
 407       if (options->pretty)
 408         {
 409           fprintf_filtered (stream, "\n");
 410           print_spaces_filtered (2 * recurse, stream);
 411         }
 412       fputs_filtered ("<", stream);
 413       /* Not sure what the best notation is in the case where there is no
 414          baseclass name.  */
 415       fputs_filtered (basename ? basename : "", stream);
 416       fputs_filtered ("> = ", stream);
 417
 418
 419       if (skip >= 1)
 420         fprintf_filtered (stream, "<invalid address>");
 421       else
 422         {
 423           int result = 0;
 424
 425           /* Attempt to run the Python pretty-printers on the
 426              baseclass if possible.  */
 427           if (!options->raw)
 428             result = apply_val_pretty_printer (baseclass, base_valaddr,
 429                                                thisoffset + boffset,
 430                                                address + boffset,
 431                                                stream, recurse,
 432                                                options,
 433                                                current_language);
 434
 435           if (!result)
 436             cp_print_value_fields (baseclass, thistype, base_valaddr,
 437                                    thisoffset + boffset, address + boffset,
 438                                    stream, recurse, options,
 439                                    ((struct type **)
 440                                     obstack_base (&dont_print_vb_obstack)),
 441                                    0);
 442         }
 443       fputs_filtered (", ", stream);
 444
 445     flush_it:
 446       ;
 447     }
 448
 449   if (dont_print_vb == 0)
 450     {
 451       /* Free the space used to deal with the printing
 452          of this type from top level.  */
 453       obstack_free (&dont_print_vb_obstack, last_dont_print);
 454       /* Reset watermark so that we can continue protecting
 455          ourselves from whatever we were protecting ourselves.  */
 456       dont_print_vb_obstack = tmp_obstack;
 457     }
 458 }
 459
 460 /* Print value of a static member.
 461    To avoid infinite recursion when printing a class that contains
 462    a static instance of the class, we keep the addresses of all printed
 463    static member classes in an obstack and refuse to print them more
 464    than once.
 465
 466    VAL contains the value to print, TYPE, STREAM, RECURSE, and OPTIONS
 467    have the same meanings as in c_val_print.  */
 468
 469 static void
 470 cp_print_static_field (struct type *type,
 471                        struct value *val,
 472                        struct ui_file *stream,
 473                        int recurse,
 474                        const struct value_print_options *options)
 475 {
 476   struct value_print_options opts;
 477   if (TYPE_CODE (type) == TYPE_CODE_STRUCT)
 478     {
 479       CORE_ADDR *first_dont_print;
 480       CORE_ADDR addr;
 481       int i;
 482
 483       first_dont_print
 484         = (CORE_ADDR *) obstack_base (&dont_print_statmem_obstack);
 485       i = (CORE_ADDR *) obstack_next_free (&dont_print_statmem_obstack)
 486         - first_dont_print;
 487
 488       while (--i >= 0)
 489         {
 490           if (value_address (val) == first_dont_print[i])
 491             {
 492               fputs_filtered ("<same as static member of an already"
 493                               " seen type>",
 494                               stream);
 495               return;
 496             }
 497         }
 498
 499       addr = value_address (val);
 500       obstack_grow (&dont_print_statmem_obstack, (char *) &addr,
 501                     sizeof (CORE_ADDR));
 502
 503       CHECK_TYPEDEF (type);
 504       cp_print_value_fields (type, type, value_contents_all (val),
 505                              value_embedded_offset (val), addr,
 506                              stream, recurse, options, NULL, 1);
 507       return;
 508     }
 509
 510   opts = *options;
 511   opts.deref_ref = 0;
 512   val_print (type, value_contents_all (val),
 513              value_embedded_offset (val), value_address (val),
 514              stream, recurse, &opts, current_language);
 515 }
 516
 517
 518 /* Find the field in *DOMAIN, or its non-virtual base classes, with bit offset
 519    OFFSET.  Set *DOMAIN to the containing type and *FIELDNO to the containing
 520    field number.  If OFFSET is not exactly at the start of some field, set
 521    *DOMAIN to NULL.  */
 522
 523 static void
 524 cp_find_class_member (struct type **domain_p, int *fieldno,
 525                       LONGEST offset)
 526 {
 527   struct type *domain;
 528   unsigned int i;
 529   unsigned len;
 530
 531   *domain_p = check_typedef (*domain_p);
 532   domain = *domain_p;
 533   len = TYPE_NFIELDS (domain);
 534
 535   for (i = TYPE_N_BASECLASSES (domain); i < len; i++)
 536     {
 537       LONGEST bitpos = TYPE_FIELD_BITPOS (domain, i);
 538
 539       QUIT;
 540       if (offset == bitpos)
 541         {
 542           *fieldno = i;
 543           return;
 544         }
 545     }
 546
 547   for (i = 0; i < TYPE_N_BASECLASSES (domain); i++)
 548     {
 549       LONGEST bitpos = TYPE_FIELD_BITPOS (domain, i);
 550       LONGEST bitsize = 8 * TYPE_LENGTH (TYPE_FIELD_TYPE (domain, i));
 551
 552       if (offset >= bitpos && offset < bitpos + bitsize)
 553         {
 554           *domain_p = TYPE_FIELD_TYPE (domain, i);
 555           cp_find_class_member (domain_p, fieldno, offset - bitpos);
 556           return;
 557         }
 558     }
 559
 560   *domain_p = NULL;
 561 }
 562
 563 void
 564 cp_print_class_member (const gdb_byte *valaddr, struct type *type,
 565                        struct ui_file *stream, char *prefix)
 566 {
 567   enum bfd_endian byte_order = gdbarch_byte_order (get_type_arch (type));
 568
 569   /* VAL is a byte offset into the structure type DOMAIN.
 570      Find the name of the field for that offset and
 571      print it.  */
 572   struct type *domain = TYPE_DOMAIN_TYPE (type);
 573   LONGEST val;
 574   unsigned int fieldno;
 575
 576   val = extract_signed_integer (valaddr, TYPE_LENGTH (type), byte_order);
 577
 578   /* Pointers to data members are usually byte offsets into an object.
 579      Because a data member can have offset zero, and a NULL pointer to
 580      member must be distinct from any valid non-NULL pointer to
 581      member, either the value is biased or the NULL value has a
 582      special representation; both are permitted by ISO C++.  HP aCC
 583      used a bias of 0x20000000; HP cfront used a bias of 1; g++ 3.x
 584      and other compilers which use the Itanium ABI use -1 as the NULL
 585      value.  GDB only supports that last form; to add support for
 586      another form, make this into a cp-abi hook.  */
 587
 588   if (val == -1)
 589     {
 590       fprintf_filtered (stream, "NULL");
 591       return;
 592     }
 593
 594   cp_find_class_member (&domain, &fieldno, val << 3);
 595
 596   if (domain != NULL)
 597     {
 598       char *name;
 599       fputs_filtered (prefix, stream);
 600       name = type_name_no_tag (domain);
 601       if (name)
 602         fputs_filtered (name, stream);
 603       else
 604         c_type_print_base (domain, stream, 0, 0);
 605       fprintf_filtered (stream, "::");
 606       fputs_filtered (TYPE_FIELD_NAME (domain, fieldno), stream);
 607     }
 608   else
 609     fprintf_filtered (stream, "%ld", (long) val);
 610 }
 611
 612
 613 void
 614 _initialize_cp_valprint (void)
 615 {
 616   add_setshow_boolean_cmd ("static-members", class_support,
 617                            &user_print_options.static_field_print, _("\
 618 Set printing of C++ static members."), _("\
 619 Show printing of C++ static members."), NULL,
 620                            NULL,
 621                            show_static_field_print,
 622                            &setprintlist, &showprintlist);
 623
 624   add_setshow_boolean_cmd ("vtbl", class_support,
 625                            &user_print_options.vtblprint, _("\
 626 Set printing of C++ virtual function tables."), _("\
 627 Show printing of C++ virtual function tables."), NULL,
 628                            NULL,
 629                            show_vtblprint,
 630                            &setprintlist, &showprintlist);
 631
 632   add_setshow_boolean_cmd ("object", class_support,
 633                            &user_print_options.objectprint, _("\
 634 Set printing of object's derived type based on vtable info."), _("\
 635 Show printing of object's derived type based on vtable info."), NULL,
 636                            NULL,
 637                            show_objectprint,
 638                            &setprintlist, &showprintlist);
 639
 640   obstack_begin (&dont_print_vb_obstack, 32 * sizeof (struct type *));
 641   obstack_specify_allocation (&dont_print_statmem_obstack,
 642                               32 * sizeof (CORE_ADDR), sizeof (CORE_ADDR),
 643                               xmalloc, xfree);
 644 }