gdb/c-valprint.c

   1 /* Support for printing C values for GDB, the GNU debugger.
   2
   3    Copyright (C) 1986-2024 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 "symtab.h"
  21 #include "gdbtypes.h"
  22 #include "expression.h"
  23 #include "value.h"
  24 #include "valprint.h"
  25 #include "language.h"
  26 #include "c-lang.h"
  27 #include "cp-abi.h"
  28 #include "target.h"
  29 #include "objfiles.h"
  30 \f
  31
  32 /* A helper for c_textual_element_type.  This checks the name of the
  33    typedef.  This is bogus but it isn't apparent that the compiler
  34    provides us the help we may need.  */
  35
  36 static int
  37 textual_name (const char *name)
  38 {
  39   return (!strcmp (name, "wchar_t")
  40           || !strcmp (name, "char16_t")
  41           || !strcmp (name, "char32_t"));
  42 }
  43
  44 /* Apply a heuristic to decide whether an array of TYPE or a pointer
  45    to TYPE should be printed as a textual string.  Return non-zero if
  46    it should, or zero if it should be treated as an array of integers
  47    or pointer to integers.  FORMAT is the current format letter, or 0
  48    if none.
  49
  50    We guess that "char" is a character.  Explicitly signed and
  51    unsigned character types are also characters.  Integer data from
  52    vector types is not.  The user can override this by using the /s
  53    format letter.  */
  54
  55 int
  56 c_textual_element_type (struct type *type, char format)
  57 {
  58   struct type *true_type, *iter_type;
  59
  60   if (format != 0 && format != 's')
  61     return 0;
  62
  63   /* We also rely on this for its side effect of setting up all the
  64      typedef pointers.  */
  65   true_type = check_typedef (type);
  66
  67   /* TYPE_CODE_CHAR is always textual.  */
  68   if (true_type->code () == TYPE_CODE_CHAR)
  69     return 1;
  70
  71   /* Any other character-like types must be integral.  */
  72   if (true_type->code () != TYPE_CODE_INT)
  73     return 0;
  74
  75   /* We peel typedefs one by one, looking for a match.  */
  76   iter_type = type;
  77   while (iter_type)
  78     {
  79       /* Check the name of the type.  */
  80       if (iter_type->name () && textual_name (iter_type->name ()))
  81         return 1;
  82
  83       if (iter_type->code () != TYPE_CODE_TYPEDEF)
  84         break;
  85
  86       /* Peel a single typedef.  If the typedef doesn't have a target
  87          type, we use check_typedef and hope the result is ok -- it
  88          might be for C++, where wchar_t is a built-in type.  */
  89       if (iter_type->target_type ())
  90         iter_type = iter_type->target_type ();
  91       else
  92         iter_type = check_typedef (iter_type);
  93     }
  94
  95   if (format == 's')
  96     {
  97       /* Print this as a string if we can manage it.  For now, no wide
  98          character support.  */
  99       if (true_type->code () == TYPE_CODE_INT
 100           && true_type->length () == 1)
 101         return 1;
 102     }
 103   else
 104     {
 105       /* If a one-byte TYPE_CODE_INT is missing the not-a-character
 106          flag, then we treat it as text; otherwise, we assume it's
 107          being used as data.  */
 108       if (true_type->code () == TYPE_CODE_INT
 109           && true_type->length () == 1
 110           && !TYPE_NOTTEXT (true_type))
 111         return 1;
 112     }
 113
 114   return 0;
 115 }
 116
 117 /* Decorations for C.  */
 118
 119 static const struct generic_val_print_decorations c_decorations =
 120 {
 121   "",
 122   " + ",
 123   "i",
 124   "true",
 125   "false",
 126   "void",
 127   "{",
 128   "}"
 129 };
 130
 131 /* Print a pointer based on the type of its target.
 132
 133    Arguments to this functions are roughly the same as those in c_val_print.
 134    A difference is that ADDRESS is the address to print, with embedded_offset
 135    already added.  UNRESOLVED_ELTTYPE and ELTTYPE represent the pointed type,
 136    respectively before and after check_typedef.  */
 137
 138 static void
 139 print_unpacked_pointer (struct type *type, struct type *elttype,
 140                         struct type *unresolved_elttype,
 141                         const gdb_byte *valaddr, int embedded_offset,
 142                         CORE_ADDR address, struct ui_file *stream, int recurse,
 143                         const struct value_print_options *options)
 144 {
 145   int want_space = 0;
 146   struct gdbarch *gdbarch = type->arch ();
 147
 148   if (elttype->code () == TYPE_CODE_FUNC)
 149     {
 150       /* Try to print what function it points to.  */
 151       print_function_pointer_address (options, gdbarch, address, stream);
 152       return;
 153     }
 154
 155   if (options->symbol_print)
 156     want_space = print_address_demangle (options, gdbarch, address, stream,
 157                                          demangle);
 158   else if (options->addressprint)
 159     {
 160       gdb_puts (paddress (gdbarch, address), stream);
 161       want_space = 1;
 162     }
 163
 164   /* For a pointer to a textual type, also print the string
 165      pointed to, unless pointer is null.  */
 166
 167   if (c_textual_element_type (unresolved_elttype, options->format)
 168       && address != 0)
 169     {
 170       if (want_space)
 171         gdb_puts (" ", stream);
 172       val_print_string (unresolved_elttype, NULL, address, -1, stream, options);
 173     }
 174   else if (cp_is_vtbl_member (type))
 175     {
 176       /* Print vtbl's nicely.  */
 177       CORE_ADDR vt_address = unpack_pointer (type, valaddr + embedded_offset);
 178       struct bound_minimal_symbol msymbol =
 179         lookup_minimal_symbol_by_pc (vt_address);
 180
 181       /* If 'symbol_print' is set, we did the work above.  */
 182       if (!options->symbol_print
 183           && (msymbol.minsym != NULL)
 184           && (vt_address == msymbol.value_address ()))
 185         {
 186           if (want_space)
 187             gdb_puts (" ", stream);
 188           gdb_puts (" <", stream);
 189           gdb_puts (msymbol.minsym->print_name (), stream);
 190           gdb_puts (">", stream);
 191           want_space = 1;
 192         }
 193
 194       if (vt_address && options->vtblprint)
 195         {
 196           struct value *vt_val;
 197           struct symbol *wsym = NULL;
 198           struct type *wtype;
 199
 200           if (want_space)
 201             gdb_puts (" ", stream);
 202
 203           if (msymbol.minsym != NULL)
 204             {
 205               const char *search_name = msymbol.minsym->search_name ();
 206               wsym = lookup_symbol_search_name (search_name, NULL,
 207                                                 SEARCH_VAR_DOMAIN).symbol;
 208             }
 209
 210           if (wsym)
 211             {
 212               wtype = wsym->type ();
 213             }
 214           else
 215             {
 216               wtype = unresolved_elttype;
 217             }
 218           vt_val = value_at (wtype, vt_address);
 219           common_val_print (vt_val, stream, recurse + 1, options,
 220                             current_language);
 221           if (options->prettyformat)
 222             {
 223               gdb_printf (stream, "\n");
 224               print_spaces (2 + 2 * recurse, stream);
 225             }
 226         }
 227     }
 228 }
 229
 230 /* c_value_print helper for TYPE_CODE_ARRAY.  */
 231
 232 static void
 233 c_value_print_array (struct value *val,
 234                      struct ui_file *stream, int recurse,
 235                      const struct value_print_options *options)
 236 {
 237   struct type *type = check_typedef (val->type ());
 238   CORE_ADDR address = val->address ();
 239   const gdb_byte *valaddr = val->contents_for_printing ().data ();
 240   struct type *unresolved_elttype = type->target_type ();
 241   struct type *elttype = check_typedef (unresolved_elttype);
 242
 243   if (type->length () > 0 && unresolved_elttype->length () > 0)
 244     {
 245       LONGEST low_bound, high_bound;
 246       int eltlen, len;
 247       enum bfd_endian byte_order = type_byte_order (type);
 248
 249       if (!get_array_bounds (type, &low_bound, &high_bound))
 250         error (_("Could not determine the array high bound"));
 251
 252       eltlen = elttype->length ();
 253       len = high_bound - low_bound + 1;
 254
 255       /* Print arrays of textual chars with a string syntax, as
 256          long as the entire array is valid.  */
 257       if (c_textual_element_type (unresolved_elttype,
 258                                   options->format)
 259           && val->bytes_available (0, type->length ())
 260           && !val->bits_any_optimized_out (0,
 261                                            TARGET_CHAR_BIT * type->length ()))
 262         {
 263           int force_ellipses = 0;
 264
 265           /* If requested, look for the first null char and only
 266              print elements up to it.  */
 267           if (options->stop_print_at_null)
 268             {
 269               unsigned int print_max_chars = get_print_max_chars (options);
 270               unsigned int temp_len;
 271
 272               for (temp_len = 0;
 273                    (temp_len < len
 274                     && temp_len < print_max_chars
 275                     && extract_unsigned_integer (valaddr + temp_len * eltlen,
 276                                                  eltlen, byte_order) != 0);
 277                    ++temp_len)
 278                 ;
 279
 280               /* Force printstr to print ellipses if
 281                  we've printed the maximum characters and
 282                  the next character is not \000.  */
 283               if (temp_len == print_max_chars && temp_len < len)
 284                 {
 285                   ULONGEST ival
 286                     = extract_unsigned_integer (valaddr + temp_len * eltlen,
 287                                                 eltlen, byte_order);
 288                   if (ival != 0)
 289                     force_ellipses = 1;
 290                 }
 291
 292               len = temp_len;
 293             }
 294
 295           current_language->printstr (stream, unresolved_elttype, valaddr, len,
 296                                       NULL, force_ellipses, options);
 297         }
 298       else
 299         {
 300           unsigned int i = 0;
 301           gdb_printf (stream, "{");
 302           /* If this is a virtual function table, print the 0th
 303              entry specially, and the rest of the members
 304              normally.  */
 305           if (cp_is_vtbl_ptr_type (elttype))
 306             {
 307               i = 1;
 308               gdb_printf (stream, _("%d vtable entries"),
 309                           len - 1);
 310             }
 311           value_print_array_elements (val, stream, recurse, options, i);
 312           gdb_printf (stream, "}");
 313         }
 314     }
 315   else
 316     {
 317       /* Array of unspecified length: treat like pointer to first elt.  */
 318       print_unpacked_pointer (type, elttype, unresolved_elttype, valaddr,
 319                               0, address, stream, recurse, options);
 320     }
 321 }
 322
 323 /* c_value_print_inner helper for TYPE_CODE_PTR.  */
 324
 325 static void
 326 c_value_print_ptr (struct value *val, struct ui_file *stream, int recurse,
 327                    const struct value_print_options *options)
 328 {
 329   if (options->format && options->format != 's')
 330     {
 331       value_print_scalar_formatted (val, options, 0, stream);
 332       return;
 333     }
 334
 335   struct type *type = check_typedef (val->type ());
 336   const gdb_byte *valaddr = val->contents_for_printing ().data ();
 337
 338   if (options->vtblprint && cp_is_vtbl_ptr_type (type))
 339     {
 340       /* Print the unmangled name if desired.  */
 341       /* Print vtable entry - we only get here if we ARE using
 342          -fvtable_thunks.  (Otherwise, look under
 343          TYPE_CODE_STRUCT.)  */
 344       CORE_ADDR addr = extract_typed_address (valaddr, type);
 345
 346       print_function_pointer_address (options, type->arch (), addr, stream);
 347     }
 348   else
 349     {
 350       struct type *unresolved_elttype = type->target_type ();
 351       struct type *elttype = check_typedef (unresolved_elttype);
 352       CORE_ADDR addr = unpack_pointer (type, valaddr);
 353
 354       print_unpacked_pointer (type, elttype, unresolved_elttype, valaddr,
 355                               0, addr, stream, recurse, options);
 356     }
 357 }
 358
 359 /* c_value_print helper for TYPE_CODE_STRUCT and TYPE_CODE_UNION.  */
 360
 361 static void
 362 c_value_print_struct (struct value *val, struct ui_file *stream, int recurse,
 363                       const struct value_print_options *options)
 364 {
 365   struct type *type = check_typedef (val->type ());
 366
 367   if (type->code () == TYPE_CODE_UNION && recurse && !options->unionprint)
 368     gdb_printf (stream, "{...}");
 369   else if (options->vtblprint && cp_is_vtbl_ptr_type (type))
 370     {
 371       /* Print the unmangled name if desired.  */
 372       /* Print vtable entry - we only get here if NOT using
 373          -fvtable_thunks.  (Otherwise, look under
 374          TYPE_CODE_PTR.)  */
 375       int offset = type->field (VTBL_FNADDR_OFFSET).loc_bitpos () / 8;
 376       struct type *field_type = type->field (VTBL_FNADDR_OFFSET).type ();
 377       const gdb_byte *valaddr = val->contents_for_printing ().data ();
 378       CORE_ADDR addr = extract_typed_address (valaddr + offset, field_type);
 379
 380       print_function_pointer_address (options, type->arch (), addr, stream);
 381     }
 382   else
 383     cp_print_value_fields (val, stream, recurse, options, NULL, 0);
 384 }
 385
 386 /* c_value_print helper for TYPE_CODE_INT.  */
 387
 388 static void
 389 c_value_print_int (struct value *val, struct ui_file *stream,
 390                    const struct value_print_options *options)
 391 {
 392   if (options->format || options->output_format)
 393     {
 394       struct value_print_options opts = *options;
 395
 396       opts.format = (options->format ? options->format
 397                      : options->output_format);
 398       value_print_scalar_formatted (val, &opts, 0, stream);
 399     }
 400   else
 401     {
 402       value_print_scalar_formatted (val, options, 0, stream);
 403       /* C and C++ has no single byte int type, char is used
 404          instead.  Since we don't know whether the value is really
 405          intended to be used as an integer or a character, print
 406          the character equivalent as well.  */
 407       struct type *type = val->type ();
 408       const gdb_byte *valaddr = val->contents_for_printing ().data ();
 409       if (c_textual_element_type (type, options->format))
 410         {
 411           gdb_puts (" ", stream);
 412           current_language->printchar (unpack_long (type, valaddr), type,
 413                                        stream);
 414         }
 415     }
 416 }
 417
 418 /* See c-lang.h.  */
 419
 420 void
 421 c_value_print_inner (struct value *val, struct ui_file *stream, int recurse,
 422                      const struct value_print_options *options)
 423 {
 424   struct type *type = val->type ();
 425
 426   type = check_typedef (type);
 427   switch (type->code ())
 428     {
 429     case TYPE_CODE_ARRAY:
 430       c_value_print_array (val, stream, recurse, options);
 431       break;
 432
 433     case TYPE_CODE_PTR:
 434       c_value_print_ptr (val, stream, recurse, options);
 435       break;
 436
 437     case TYPE_CODE_UNION:
 438     case TYPE_CODE_STRUCT:
 439       c_value_print_struct (val, stream, recurse, options);
 440       break;
 441
 442     case TYPE_CODE_CHAR:
 443     case TYPE_CODE_INT:
 444       c_value_print_int (val, stream, options);
 445       break;
 446
 447     case TYPE_CODE_METHODPTR:
 448     case TYPE_CODE_MEMBERPTR:
 449     case TYPE_CODE_REF:
 450     case TYPE_CODE_RVALUE_REF:
 451     case TYPE_CODE_ENUM:
 452     case TYPE_CODE_FLAGS:
 453     case TYPE_CODE_FUNC:
 454     case TYPE_CODE_METHOD:
 455     case TYPE_CODE_BOOL:
 456     case TYPE_CODE_RANGE:
 457     case TYPE_CODE_FLT:
 458     case TYPE_CODE_DECFLOAT:
 459     case TYPE_CODE_VOID:
 460     case TYPE_CODE_ERROR:
 461     case TYPE_CODE_UNDEF:
 462     case TYPE_CODE_COMPLEX:
 463     default:
 464       generic_value_print (val, stream, recurse, options, &c_decorations);
 465       break;
 466     }
 467 }
 468
 469 \f
 470 void
 471 c_value_print (struct value *val, struct ui_file *stream,
 472                const struct value_print_options *options)
 473 {
 474   struct type *type, *real_type;
 475   int full, using_enc;
 476   LONGEST top;
 477   struct value_print_options opts = *options;
 478
 479   opts.deref_ref = true;
 480
 481   /* If it is a pointer, indicate what it points to.
 482
 483      Print type also if it is a reference.
 484
 485      C++: if it is a member pointer, we will take care
 486      of that when we print it.  */
 487
 488   type = check_typedef (val->type ());
 489
 490   if (type->is_pointer_or_reference ())
 491     {
 492       struct type *original_type = val->type ();
 493
 494       /* Hack:  remove (char *) for char strings.  Their
 495          type is indicated by the quoted string anyway.
 496          (Don't use c_textual_element_type here; quoted strings
 497          are always exactly (char *), (wchar_t *), or the like.  */
 498       if (original_type->code () == TYPE_CODE_PTR
 499           && original_type->name () == NULL
 500           && original_type->target_type ()->name () != NULL
 501           && (strcmp (original_type->target_type ()->name (),
 502                       "char") == 0
 503               || textual_name (original_type->target_type ()->name ())))
 504         {
 505           /* Print nothing.  */
 506         }
 507       else if (options->objectprint
 508                && (type->target_type ()->code () == TYPE_CODE_STRUCT))
 509         {
 510           int is_ref = TYPE_IS_REFERENCE (type);
 511           enum type_code refcode = TYPE_CODE_UNDEF;
 512
 513           if (is_ref)
 514             {
 515               val = value_addr (val);
 516               refcode = type->code ();
 517             }
 518
 519           /* Pointer to class, check real type of object.  */
 520           gdb_printf (stream, "(");
 521
 522           if (val->entirely_available ())
 523             {
 524               real_type = value_rtti_indirect_type (val, &full, &top,
 525                                                     &using_enc);
 526               if (real_type)
 527                 {
 528                   /* RTTI entry found.  */
 529
 530                   /* Need to adjust pointer value.  */
 531                   val = value_from_pointer (real_type,
 532                                             value_as_address (val) - top);
 533
 534                   /* Note: When we look up RTTI entries, we don't get
 535                      any information on const or volatile
 536                      attributes.  */
 537                 }
 538             }
 539
 540           if (is_ref)
 541             val = value_ref (value_ind (val), refcode);
 542
 543           type = val->type ();
 544           type_print (type, "", stream, -1);
 545           gdb_printf (stream, ") ");
 546         }
 547       else
 548         {
 549           /* normal case */
 550           gdb_printf (stream, "(");
 551           type_print (val->type (), "", stream, -1);
 552           gdb_printf (stream, ") ");
 553         }
 554     }
 555
 556   if (!val->initialized ())
 557     gdb_printf (stream, " [uninitialized] ");
 558
 559   if (options->objectprint && (type->code () == TYPE_CODE_STRUCT))
 560     {
 561       /* Attempt to determine real type of object.  */
 562       real_type = value_rtti_type (val, &full, &top, &using_enc);
 563       if (real_type)
 564         {
 565           /* We have RTTI information, so use it.  */
 566           val = value_full_object (val, real_type,
 567                                    full, top, using_enc);
 568           /* In a destructor we might see a real type that is a
 569              superclass of the object's type.  In this case it is
 570              better to leave the object as-is.  */
 571           if (!(full
 572                 && (real_type->length ()
 573                     < val->enclosing_type ()->length ())))
 574             val = value_cast (real_type, val);
 575           gdb_printf (stream, "(%s%s) ",
 576                       real_type->name (),
 577                       full ? "" : _(" [incomplete object]"));
 578         }
 579       else if (type != check_typedef (val->enclosing_type ()))
 580         {
 581           /* No RTTI information, so let's do our best.  */
 582           gdb_printf (stream, "(%s ?) ",
 583                       val->enclosing_type ()->name ());
 584           val = value_cast (val->enclosing_type (), val);
 585         }
 586     }
 587
 588   common_val_print (val, stream, 0, &opts, current_language);
 589 }