gdb/c-valprint.c

   1 /* Support for printing C values for GDB, the GNU debugger.
   2
   3    Copyright (C) 1986-2023 Free Software Foundation, Inc.
   4
   5    This file is part of GDB.
   6
   7    This program is free software; you can redistribute it and/or modify
   8    it under the terms of the GNU General Public License as published by
   9    the Free Software Foundation; either version 3 of the License, or
  10    (at your option) any later version.
  11
  12    This program is distributed in the hope that it will be useful,
  13    but WITHOUT ANY WARRANTY; without even the implied warranty of
  14    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  15    GNU General Public License for more details.
  16
  17    You should have received a copy of the GNU General Public License
  18    along with this program.  If not, see <http://www.gnu.org/licenses/>.  */
  19
  20 #include "defs.h"
  21 #include "symtab.h"
  22 #include "gdbtypes.h"
  23 #include "expression.h"
  24 #include "value.h"
  25 #include "valprint.h"
  26 #include "language.h"
  27 #include "c-lang.h"
  28 #include "cp-abi.h"
  29 #include "target.h"
  30 #include "objfiles.h"
  31 \f
  32
  33 /* A helper for c_textual_element_type.  This checks the name of the
  34    typedef.  This is bogus but it isn't apparent that the compiler
  35    provides us the help we may need.  */
  36
  37 static int
  38 textual_name (const char *name)
  39 {
  40   return (!strcmp (name, "wchar_t")
  41           || !strcmp (name, "char16_t")
  42           || !strcmp (name, "char32_t"));
  43 }
  44
  45 /* Apply a heuristic to decide whether an array of TYPE or a pointer
  46    to TYPE should be printed as a textual string.  Return non-zero if
  47    it should, or zero if it should be treated as an array of integers
  48    or pointer to integers.  FORMAT is the current format letter, or 0
  49    if none.
  50
  51    We guess that "char" is a character.  Explicitly signed and
  52    unsigned character types are also characters.  Integer data from
  53    vector types is not.  The user can override this by using the /s
  54    format letter.  */
  55
  56 int
  57 c_textual_element_type (struct type *type, char format)
  58 {
  59   struct type *true_type, *iter_type;
  60
  61   if (format != 0 && format != 's')
  62     return 0;
  63
  64   /* We also rely on this for its side effect of setting up all the
  65      typedef pointers.  */
  66   true_type = check_typedef (type);
  67
  68   /* TYPE_CODE_CHAR is always textual.  */
  69   if (true_type->code () == TYPE_CODE_CHAR)
  70     return 1;
  71
  72   /* Any other character-like types must be integral.  */
  73   if (true_type->code () != TYPE_CODE_INT)
  74     return 0;
  75
  76   /* We peel typedefs one by one, looking for a match.  */
  77   iter_type = type;
  78   while (iter_type)
  79     {
  80       /* Check the name of the type.  */
  81       if (iter_type->name () && textual_name (iter_type->name ()))
  82         return 1;
  83
  84       if (iter_type->code () != TYPE_CODE_TYPEDEF)
  85         break;
  86
  87       /* Peel a single typedef.  If the typedef doesn't have a target
  88          type, we use check_typedef and hope the result is ok -- it
  89          might be for C++, where wchar_t is a built-in type.  */
  90       if (iter_type->target_type ())
  91         iter_type = iter_type->target_type ();
  92       else
  93         iter_type = check_typedef (iter_type);
  94     }
  95
  96   if (format == 's')
  97     {
  98       /* Print this as a string if we can manage it.  For now, no wide
  99          character support.  */
 100       if (true_type->code () == TYPE_CODE_INT
 101           && true_type->length () == 1)
 102         return 1;
 103     }
 104   else
 105     {
 106       /* If a one-byte TYPE_CODE_INT is missing the not-a-character
 107          flag, then we treat it as text; otherwise, we assume it's
 108          being used as data.  */
 109       if (true_type->code () == TYPE_CODE_INT
 110           && true_type->length () == 1
 111           && !TYPE_NOTTEXT (true_type))
 112         return 1;
 113     }
 114
 115   return 0;
 116 }
 117
 118 /* Decorations for C.  */
 119
 120 static const struct generic_val_print_decorations c_decorations =
 121 {
 122   "",
 123   " + ",
 124   "i",
 125   "true",
 126   "false",
 127   "void",
 128   "{",
 129   "}"
 130 };
 131
 132 /* Print a pointer based on the type of its target.
 133
 134    Arguments to this functions are roughly the same as those in c_val_print.
 135    A difference is that ADDRESS is the address to print, with embedded_offset
 136    already added.  UNRESOLVED_ELTTYPE and ELTTYPE represent the pointed type,
 137    respectively before and after check_typedef.  */
 138
 139 static void
 140 print_unpacked_pointer (struct type *type, struct type *elttype,
 141                         struct type *unresolved_elttype,
 142                         const gdb_byte *valaddr, int embedded_offset,
 143                         CORE_ADDR address, struct ui_file *stream, int recurse,
 144                         const struct value_print_options *options)
 145 {
 146   int want_space = 0;
 147   struct gdbarch *gdbarch = type->arch ();
 148
 149   if (elttype->code () == TYPE_CODE_FUNC)
 150     {
 151       /* Try to print what function it points to.  */
 152       print_function_pointer_address (options, gdbarch, address, stream);
 153       return;
 154     }
 155
 156   if (options->symbol_print)
 157     want_space = print_address_demangle (options, gdbarch, address, stream,
 158                                          demangle);
 159   else if (options->addressprint)
 160     {
 161       gdb_puts (paddress (gdbarch, address), stream);
 162       want_space = 1;
 163     }
 164
 165   /* For a pointer to a textual type, also print the string
 166      pointed to, unless pointer is null.  */
 167
 168   if (c_textual_element_type (unresolved_elttype, options->format)
 169       && address != 0)
 170     {
 171       if (want_space)
 172         gdb_puts (" ", stream);
 173       val_print_string (unresolved_elttype, NULL, address, -1, stream, options);
 174     }
 175   else if (cp_is_vtbl_member (type))
 176     {
 177       /* Print vtbl's nicely.  */
 178       CORE_ADDR vt_address = unpack_pointer (type, valaddr + embedded_offset);
 179       struct bound_minimal_symbol msymbol =
 180         lookup_minimal_symbol_by_pc (vt_address);
 181
 182       /* If 'symbol_print' is set, we did the work above.  */
 183       if (!options->symbol_print
 184           && (msymbol.minsym != NULL)
 185           && (vt_address == msymbol.value_address ()))
 186         {
 187           if (want_space)
 188             gdb_puts (" ", stream);
 189           gdb_puts (" <", stream);
 190           gdb_puts (msymbol.minsym->print_name (), stream);
 191           gdb_puts (">", stream);
 192           want_space = 1;
 193         }
 194
 195       if (vt_address && options->vtblprint)
 196         {
 197           struct value *vt_val;
 198           struct symbol *wsym = NULL;
 199           struct type *wtype;
 200
 201           if (want_space)
 202             gdb_puts (" ", stream);
 203
 204           if (msymbol.minsym != NULL)
 205             {
 206               const char *search_name = msymbol.minsym->search_name ();
 207               wsym = lookup_symbol_search_name (search_name, NULL,
 208                                                 VAR_DOMAIN).symbol;
 209             }
 210
 211           if (wsym)
 212             {
 213               wtype = wsym->type ();
 214             }
 215           else
 216             {
 217               wtype = unresolved_elttype;
 218             }
 219           vt_val = value_at (wtype, vt_address);
 220           common_val_print (vt_val, stream, recurse + 1, options,
 221                             current_language);
 222           if (options->prettyformat)
 223             {
 224               gdb_printf (stream, "\n");
 225               print_spaces (2 + 2 * recurse, stream);
 226             }
 227         }
 228     }
 229 }
 230
 231 /* c_value_print helper for TYPE_CODE_ARRAY.  */
 232
 233 static void
 234 c_value_print_array (struct value *val,
 235                      struct ui_file *stream, int recurse,
 236                      const struct value_print_options *options)
 237 {
 238   struct type *type = check_typedef (val->type ());
 239   CORE_ADDR address = val->address ();
 240   const gdb_byte *valaddr = value_contents_for_printing (val).data ();
 241   struct type *unresolved_elttype = type->target_type ();
 242   struct type *elttype = check_typedef (unresolved_elttype);
 243
 244   if (type->length () > 0 && unresolved_elttype->length () > 0)
 245     {
 246       LONGEST low_bound, high_bound;
 247       int eltlen, len;
 248       enum bfd_endian byte_order = type_byte_order (type);
 249
 250       if (!get_array_bounds (type, &low_bound, &high_bound))
 251         error (_("Could not determine the array high bound"));
 252
 253       eltlen = elttype->length ();
 254       len = high_bound - low_bound + 1;
 255
 256       /* Print arrays of textual chars with a string syntax, as
 257          long as the entire array is valid.  */
 258       if (c_textual_element_type (unresolved_elttype,
 259                                   options->format)
 260           && value_bytes_available (val, 0, type->length ())
 261           && !value_bits_any_optimized_out (val, 0,
 262                                             TARGET_CHAR_BIT * type->length ()))
 263         {
 264           int force_ellipses = 0;
 265
 266           /* If requested, look for the first null char and only
 267              print elements up to it.  */
 268           if (options->stop_print_at_null)
 269             {
 270               unsigned int print_max_chars = get_print_max_chars (options);
 271               unsigned int temp_len;
 272
 273               for (temp_len = 0;
 274                    (temp_len < len
 275                     && temp_len < print_max_chars
 276                     && extract_unsigned_integer (valaddr + temp_len * eltlen,
 277                                                  eltlen, byte_order) != 0);
 278                    ++temp_len)
 279                 ;
 280
 281               /* Force printstr to print ellipses if
 282                  we've printed the maximum characters and
 283                  the next character is not \000.  */
 284               if (temp_len == print_max_chars && temp_len < len)
 285                 {
 286                   ULONGEST ival
 287                     = extract_unsigned_integer (valaddr + temp_len * eltlen,
 288                                                 eltlen, byte_order);
 289                   if (ival != 0)
 290                     force_ellipses = 1;
 291                 }
 292
 293               len = temp_len;
 294             }
 295
 296           current_language->printstr (stream, unresolved_elttype, valaddr, len,
 297                                       NULL, force_ellipses, options);
 298         }
 299       else
 300         {
 301           unsigned int i = 0;
 302           gdb_printf (stream, "{");
 303           /* If this is a virtual function table, print the 0th
 304              entry specially, and the rest of the members
 305              normally.  */
 306           if (cp_is_vtbl_ptr_type (elttype))
 307             {
 308               i = 1;
 309               gdb_printf (stream, _("%d vtable entries"),
 310                           len - 1);
 311             }
 312           value_print_array_elements (val, stream, recurse, options, i);
 313           gdb_printf (stream, "}");
 314         }
 315     }
 316   else
 317     {
 318       /* Array of unspecified length: treat like pointer to first elt.  */
 319       print_unpacked_pointer (type, elttype, unresolved_elttype, valaddr,
 320                               0, address, stream, recurse, options);
 321     }
 322 }
 323
 324 /* c_value_print_inner helper for TYPE_CODE_PTR.  */
 325
 326 static void
 327 c_value_print_ptr (struct value *val, struct ui_file *stream, int recurse,
 328                    const struct value_print_options *options)
 329 {
 330   if (options->format && options->format != 's')
 331     {
 332       value_print_scalar_formatted (val, options, 0, stream);
 333       return;
 334     }
 335
 336   struct type *type = check_typedef (val->type ());
 337   const gdb_byte *valaddr = value_contents_for_printing (val).data ();
 338
 339   if (options->vtblprint && cp_is_vtbl_ptr_type (type))
 340     {
 341       /* Print the unmangled name if desired.  */
 342       /* Print vtable entry - we only get here if we ARE using
 343          -fvtable_thunks.  (Otherwise, look under
 344          TYPE_CODE_STRUCT.)  */
 345       CORE_ADDR addr = extract_typed_address (valaddr, type);
 346
 347       print_function_pointer_address (options, type->arch (), addr, stream);
 348     }
 349   else
 350     {
 351       struct type *unresolved_elttype = type->target_type ();
 352       struct type *elttype = check_typedef (unresolved_elttype);
 353       CORE_ADDR addr = unpack_pointer (type, valaddr);
 354
 355       print_unpacked_pointer (type, elttype, unresolved_elttype, valaddr,
 356                               0, addr, stream, recurse, options);
 357     }
 358 }
 359
 360 /* c_value_print helper for TYPE_CODE_STRUCT and TYPE_CODE_UNION.  */
 361
 362 static void
 363 c_value_print_struct (struct value *val, struct ui_file *stream, int recurse,
 364                       const struct value_print_options *options)
 365 {
 366   struct type *type = check_typedef (val->type ());
 367
 368   if (type->code () == TYPE_CODE_UNION && recurse && !options->unionprint)
 369     gdb_printf (stream, "{...}");
 370   else if (options->vtblprint && cp_is_vtbl_ptr_type (type))
 371     {
 372       /* Print the unmangled name if desired.  */
 373       /* Print vtable entry - we only get here if NOT using
 374          -fvtable_thunks.  (Otherwise, look under
 375          TYPE_CODE_PTR.)  */
 376       int offset = type->field (VTBL_FNADDR_OFFSET).loc_bitpos () / 8;
 377       struct type *field_type = type->field (VTBL_FNADDR_OFFSET).type ();
 378       const gdb_byte *valaddr = value_contents_for_printing (val).data ();
 379       CORE_ADDR addr = extract_typed_address (valaddr + offset, field_type);
 380
 381       print_function_pointer_address (options, type->arch (), addr, stream);
 382     }
 383   else
 384     cp_print_value_fields (val, stream, recurse, options, NULL, 0);
 385 }
 386
 387 /* c_value_print helper for TYPE_CODE_INT.  */
 388
 389 static void
 390 c_value_print_int (struct value *val, struct ui_file *stream,
 391                    const struct value_print_options *options)
 392 {
 393   if (options->format || options->output_format)
 394     {
 395       struct value_print_options opts = *options;
 396
 397       opts.format = (options->format ? options->format
 398                      : options->output_format);
 399       value_print_scalar_formatted (val, &opts, 0, stream);
 400     }
 401   else
 402     {
 403       value_print_scalar_formatted (val, options, 0, stream);
 404       /* C and C++ has no single byte int type, char is used
 405          instead.  Since we don't know whether the value is really
 406          intended to be used as an integer or a character, print
 407          the character equivalent as well.  */
 408       struct type *type = val->type ();
 409       const gdb_byte *valaddr = value_contents_for_printing (val).data ();
 410       if (c_textual_element_type (type, options->format))
 411         {
 412           gdb_puts (" ", stream);
 413           current_language->printchar (unpack_long (type, valaddr), type,
 414                                        stream);
 415         }
 416     }
 417 }
 418
 419 /* See c-lang.h.  */
 420
 421 void
 422 c_value_print_inner (struct value *val, struct ui_file *stream, int recurse,
 423                      const struct value_print_options *options)
 424 {
 425   struct type *type = val->type ();
 426
 427   type = check_typedef (type);
 428   switch (type->code ())
 429     {
 430     case TYPE_CODE_ARRAY:
 431       c_value_print_array (val, stream, recurse, options);
 432       break;
 433
 434     case TYPE_CODE_PTR:
 435       c_value_print_ptr (val, stream, recurse, options);
 436       break;
 437
 438     case TYPE_CODE_UNION:
 439     case TYPE_CODE_STRUCT:
 440       c_value_print_struct (val, stream, recurse, options);
 441       break;
 442
 443     case TYPE_CODE_CHAR:
 444     case TYPE_CODE_INT:
 445       c_value_print_int (val, stream, options);
 446       break;
 447
 448     case TYPE_CODE_METHODPTR:
 449     case TYPE_CODE_MEMBERPTR:
 450     case TYPE_CODE_REF:
 451     case TYPE_CODE_RVALUE_REF:
 452     case TYPE_CODE_ENUM:
 453     case TYPE_CODE_FLAGS:
 454     case TYPE_CODE_FUNC:
 455     case TYPE_CODE_METHOD:
 456     case TYPE_CODE_BOOL:
 457     case TYPE_CODE_RANGE:
 458     case TYPE_CODE_FLT:
 459     case TYPE_CODE_DECFLOAT:
 460     case TYPE_CODE_VOID:
 461     case TYPE_CODE_ERROR:
 462     case TYPE_CODE_UNDEF:
 463     case TYPE_CODE_COMPLEX:
 464     default:
 465       generic_value_print (val, stream, recurse, options, &c_decorations);
 466       break;
 467     }
 468 }
 469
 470 \f
 471 void
 472 c_value_print (struct value *val, struct ui_file *stream,
 473                const struct value_print_options *options)
 474 {
 475   struct type *type, *real_type;
 476   int full, using_enc;
 477   LONGEST top;
 478   struct value_print_options opts = *options;
 479
 480   opts.deref_ref = true;
 481
 482   /* If it is a pointer, indicate what it points to.
 483
 484      Print type also if it is a reference.
 485
 486      C++: if it is a member pointer, we will take care
 487      of that when we print it.  */
 488
 489   type = check_typedef (val->type ());
 490
 491   if (type->is_pointer_or_reference ())
 492     {
 493       struct type *original_type = val->type ();
 494
 495       /* Hack:  remove (char *) for char strings.  Their
 496          type is indicated by the quoted string anyway.
 497          (Don't use c_textual_element_type here; quoted strings
 498          are always exactly (char *), (wchar_t *), or the like.  */
 499       if (original_type->code () == TYPE_CODE_PTR
 500           && original_type->name () == NULL
 501           && original_type->target_type ()->name () != NULL
 502           && (strcmp (original_type->target_type ()->name (),
 503                       "char") == 0
 504               || textual_name (original_type->target_type ()->name ())))
 505         {
 506           /* Print nothing.  */
 507         }
 508       else if (options->objectprint
 509                && (type->target_type ()->code () == TYPE_CODE_STRUCT))
 510         {
 511           int is_ref = TYPE_IS_REFERENCE (type);
 512           enum type_code refcode = TYPE_CODE_UNDEF;
 513
 514           if (is_ref)
 515             {
 516               val = value_addr (val);
 517               refcode = type->code ();
 518             }
 519
 520           /* Pointer to class, check real type of object.  */
 521           gdb_printf (stream, "(");
 522
 523           if (value_entirely_available (val))
 524             {
 525               real_type = value_rtti_indirect_type (val, &full, &top,
 526                                                     &using_enc);
 527               if (real_type)
 528                 {
 529                   /* RTTI entry found.  */
 530
 531                   /* Need to adjust pointer value.  */
 532                   val = value_from_pointer (real_type,
 533                                             value_as_address (val) - top);
 534
 535                   /* Note: When we look up RTTI entries, we don't get
 536                      any information on const or volatile
 537                      attributes.  */
 538                 }
 539             }
 540
 541           if (is_ref)
 542             val = value_ref (value_ind (val), refcode);
 543
 544           type = val->type ();
 545           type_print (type, "", stream, -1);
 546           gdb_printf (stream, ") ");
 547         }
 548       else
 549         {
 550           /* normal case */
 551           gdb_printf (stream, "(");
 552           type_print (val->type (), "", stream, -1);
 553           gdb_printf (stream, ") ");
 554         }
 555     }
 556
 557   if (!val->initialized ())
 558     gdb_printf (stream, " [uninitialized] ");
 559
 560   if (options->objectprint && (type->code () == TYPE_CODE_STRUCT))
 561     {
 562       /* Attempt to determine real type of object.  */
 563       real_type = value_rtti_type (val, &full, &top, &using_enc);
 564       if (real_type)
 565         {
 566           /* We have RTTI information, so use it.  */
 567           val = value_full_object (val, real_type,
 568                                    full, top, using_enc);
 569           /* In a destructor we might see a real type that is a
 570              superclass of the object's type.  In this case it is
 571              better to leave the object as-is.  */
 572           if (!(full
 573                 && (real_type->length ()
 574                     < val->enclosing_type ()->length ())))
 575             val = value_cast (real_type, val);
 576           gdb_printf (stream, "(%s%s) ",
 577                       real_type->name (),
 578                       full ? "" : _(" [incomplete object]"));
 579         }
 580       else if (type != check_typedef (val->enclosing_type ()))
 581         {
 582           /* No RTTI information, so let's do our best.  */
 583           gdb_printf (stream, "(%s ?) ",
 584                       val->enclosing_type ()->name ());
 585           val = value_cast (val->enclosing_type (), val);
 586         }
 587     }
 588
 589   common_val_print (val, stream, 0, &opts, current_language);
 590 }