gdb/dwarf2/read.h

   1 /* DWARF 2 debugging format support for GDB.
   2
   3    Copyright (C) 1994-2020 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 #ifndef DWARF2READ_H
  21 #define DWARF2READ_H
  22
  23 #include <queue>
  24 #include <unordered_map>
  25 #include "dwarf2/comp-unit.h"
  26 #include "dwarf2/index-cache.h"
  27 #include "dwarf2/section.h"
  28 #include "filename-seen-cache.h"
  29 #include "gdb_obstack.h"
  30 #include "gdbsupport/hash_enum.h"
  31 #include "gdbsupport/function-view.h"
  32 #include "psympriv.h"
  33
  34 /* Hold 'maintenance (set|show) dwarf' commands.  */
  35 extern struct cmd_list_element *set_dwarf_cmdlist;
  36 extern struct cmd_list_element *show_dwarf_cmdlist;
  37
  38 struct tu_stats
  39 {
  40   int nr_uniq_abbrev_tables;
  41   int nr_symtabs;
  42   int nr_symtab_sharers;
  43   int nr_stmt_less_type_units;
  44   int nr_all_type_units_reallocs;
  45 };
  46
  47 struct dwarf2_cu;
  48 struct dwarf2_debug_sections;
  49 struct dwarf2_per_cu_data;
  50 struct mapped_index;
  51 struct mapped_debug_names;
  52 struct signatured_type;
  53 struct type_unit_group;
  54
  55 /* One item on the queue of compilation units to read in full symbols
  56    for.  */
  57 struct dwarf2_queue_item
  58 {
  59   dwarf2_queue_item (dwarf2_per_cu_data *cu, dwarf2_per_objfile *per_objfile,
  60                      enum language lang)
  61     : per_cu (cu),
  62       per_objfile (per_objfile),
  63       pretend_language (lang)
  64   {
  65   }
  66
  67   ~dwarf2_queue_item ();
  68
  69   DISABLE_COPY_AND_ASSIGN (dwarf2_queue_item);
  70
  71   dwarf2_per_cu_data *per_cu;
  72   dwarf2_per_objfile *per_objfile;
  73   enum language pretend_language;
  74 };
  75
  76 /* Some DWARF data can be shared across objfiles who share the same BFD,
  77    this data is stored in this object.
  78
  79    Two dwarf2_per_objfile objects representing objfiles sharing the same BFD
  80    will point to the same instance of dwarf2_per_bfd, unless the BFD requires
  81    relocation.  */
  82
  83 struct dwarf2_per_bfd
  84 {
  85   /* Construct a dwarf2_per_bfd for OBFD.  NAMES points to the
  86      dwarf2 section names, or is NULL if the standard ELF names are
  87      used.  CAN_COPY is true for formats where symbol
  88      interposition is possible and so symbol values must follow copy
  89      relocation rules.  */
  90   dwarf2_per_bfd (bfd *obfd, const dwarf2_debug_sections *names, bool can_copy);
  91
  92   ~dwarf2_per_bfd ();
  93
  94   DISABLE_COPY_AND_ASSIGN (dwarf2_per_bfd);
  95
  96   /* Return the CU/TU given its index.
  97
  98      This is intended for loops like:
  99
 100      for (i = 0; i < (dwarf2_per_bfd->n_comp_units
 101                       + dwarf2_per_bfd->n_type_units); ++i)
 102        {
 103          dwarf2_per_cu_data *per_cu = dwarf2_per_bfd->get_cutu (i);
 104
 105          ...;
 106        }
 107   */
 108   dwarf2_per_cu_data *get_cutu (int index);
 109
 110   /* Return the CU given its index.
 111      This differs from get_cutu in that it's for when you know INDEX refers to a
 112      CU.  */
 113   dwarf2_per_cu_data *get_cu (int index);
 114
 115   /* Return the TU given its index.
 116      This differs from get_cutu in that it's for when you know INDEX refers to a
 117      TU.  */
 118   signatured_type *get_tu (int index);
 119
 120   /* A convenience function to allocate a dwarf2_per_cu_data.  The
 121      returned object has its "index" field set properly.  The object
 122      is allocated on the dwarf2_per_bfd obstack.  */
 123   dwarf2_per_cu_data *allocate_per_cu ();
 124
 125   /* A convenience function to allocate a signatured_type.  The
 126      returned object has its "index" field set properly.  The object
 127      is allocated on the dwarf2_per_bfd obstack.  */
 128   signatured_type *allocate_signatured_type ();
 129
 130   /* Return the number of partial symtabs allocated with allocate_per_cu
 131      and allocate_signatured_type so far.  */
 132   int num_psymtabs () const
 133   { return m_num_psymtabs; }
 134
 135 private:
 136   /* This function is mapped across the sections and remembers the
 137      offset and size of each of the debugging sections we are
 138      interested in.  */
 139   void locate_sections (bfd *abfd, asection *sectp,
 140                         const dwarf2_debug_sections &names);
 141
 142 public:
 143   /* The corresponding BFD.  */
 144   bfd *obfd;
 145
 146   /* Objects that can be shared across objfiles are stored in this
 147      obstack or on the psymtab obstack, while objects that are
 148      objfile-specific are stored on the objfile obstack.  */
 149   auto_obstack obstack;
 150
 151   dwarf2_section_info info {};
 152   dwarf2_section_info abbrev {};
 153   dwarf2_section_info line {};
 154   dwarf2_section_info loc {};
 155   dwarf2_section_info loclists {};
 156   dwarf2_section_info macinfo {};
 157   dwarf2_section_info macro {};
 158   dwarf2_section_info str {};
 159   dwarf2_section_info str_offsets {};
 160   dwarf2_section_info line_str {};
 161   dwarf2_section_info ranges {};
 162   dwarf2_section_info rnglists {};
 163   dwarf2_section_info addr {};
 164   dwarf2_section_info frame {};
 165   dwarf2_section_info eh_frame {};
 166   dwarf2_section_info gdb_index {};
 167   dwarf2_section_info debug_names {};
 168   dwarf2_section_info debug_aranges {};
 169
 170   std::vector<dwarf2_section_info> types;
 171
 172   /* Table of all the compilation units.  This is used to locate
 173      the target compilation unit of a particular reference.  */
 174   std::vector<dwarf2_per_cu_data *> all_comp_units;
 175
 176   /* The .debug_types-related CUs (TUs).  */
 177   std::vector<signatured_type *> all_type_units;
 178
 179   /* Table of struct type_unit_group objects.
 180      The hash key is the DW_AT_stmt_list value.  */
 181   htab_up type_unit_groups;
 182
 183   /* A table mapping .debug_types signatures to its signatured_type entry.
 184      This is NULL if the .debug_types section hasn't been read in yet.  */
 185   htab_up signatured_types;
 186
 187   /* Type unit statistics, to see how well the scaling improvements
 188      are doing.  */
 189   struct tu_stats tu_stats {};
 190
 191   /* A table mapping DW_AT_dwo_name values to struct dwo_file objects.
 192      This is NULL if the table hasn't been allocated yet.  */
 193   htab_up dwo_files;
 194
 195   /* True if we've checked for whether there is a DWP file.  */
 196   bool dwp_checked = false;
 197
 198   /* The DWP file if there is one, or NULL.  */
 199   std::unique_ptr<struct dwp_file> dwp_file;
 200
 201   /* The shared '.dwz' file, if one exists.  This is used when the
 202      original data was compressed using 'dwz -m'.  */
 203   std::unique_ptr<struct dwz_file> dwz_file;
 204
 205   /* Whether copy relocations are supported by this object format.  */
 206   bool can_copy;
 207
 208   /* A flag indicating whether this objfile has a section loaded at a
 209      VMA of 0.  */
 210   bool has_section_at_zero = false;
 211
 212   /* True if we are using the mapped index,
 213      or we are faking it for OBJF_READNOW's sake.  */
 214   bool using_index = false;
 215
 216   /* The mapped index, or NULL if .gdb_index is missing or not being used.  */
 217   std::unique_ptr<mapped_index> index_table;
 218
 219   /* The mapped index, or NULL if .debug_names is missing or not being used.  */
 220   std::unique_ptr<mapped_debug_names> debug_names_table;
 221
 222   /* When using index_table, this keeps track of all quick_file_names entries.
 223      TUs typically share line table entries with a CU, so we maintain a
 224      separate table of all line table entries to support the sharing.
 225      Note that while there can be way more TUs than CUs, we've already
 226      sorted all the TUs into "type unit groups", grouped by their
 227      DW_AT_stmt_list value.  Therefore the only sharing done here is with a
 228      CU and its associated TU group if there is one.  */
 229   htab_up quick_file_names_table;
 230
 231   /* Set during partial symbol reading, to prevent queueing of full
 232      symbols.  */
 233   bool reading_partial_symbols = false;
 234
 235   /* The CUs we recently read.  */
 236   std::vector<dwarf2_per_cu_data *> just_read_cus;
 237
 238   /* Table containing all filenames.  This is an optional because the
 239      table is lazily constructed on first access.  */
 240   gdb::optional<filename_seen_cache> filenames_cache;
 241
 242   /* If we loaded the index from an external file, this contains the
 243      resources associated to the open file, memory mapping, etc.  */
 244   std::unique_ptr<index_cache_resource> index_cache_res;
 245
 246   /* Mapping from abstract origin DIE to concrete DIEs that reference it as
 247      DW_AT_abstract_origin.  */
 248   std::unordered_map<sect_offset, std::vector<sect_offset>,
 249                      gdb::hash_enum<sect_offset>>
 250     abstract_to_concrete;
 251
 252   /* CUs that are queued to be read.  */
 253   std::queue<dwarf2_queue_item> queue;
 254
 255   /* We keep a separate reference to the partial symtabs, in case we
 256      are sharing them between objfiles.  This is only set after
 257      partial symbols have been read the first time.  */
 258   std::shared_ptr<psymtab_storage> partial_symtabs;
 259
 260 private:
 261
 262   /* The total number of per_cu and signatured_type objects that have
 263      been created so far for this reader.  */
 264   size_t m_num_psymtabs = 0;
 265 };
 266
 267 /* This is the per-objfile data associated with a type_unit_group.  */
 268
 269 struct type_unit_group_unshareable
 270 {
 271   /* The compunit symtab.
 272      Type units in a group needn't all be defined in the same source file,
 273      so we create an essentially anonymous symtab as the compunit symtab.  */
 274   struct compunit_symtab *compunit_symtab = nullptr;
 275
 276   /* The number of symtabs from the line header.
 277      The value here must match line_header.num_file_names.  */
 278   unsigned int num_symtabs = 0;
 279
 280   /* The symbol tables for this TU (obtained from the files listed in
 281      DW_AT_stmt_list).
 282      WARNING: The order of entries here must match the order of entries
 283      in the line header.  After the first TU using this type_unit_group, the
 284      line header for the subsequent TUs is recreated from this.  This is done
 285      because we need to use the same symtabs for each TU using the same
 286      DW_AT_stmt_list value.  Also note that symtabs may be repeated here,
 287      there's no guarantee the line header doesn't have duplicate entries.  */
 288   struct symtab **symtabs = nullptr;
 289 };
 290
 291 /* Collection of data recorded per objfile.
 292    This hangs off of dwarf2_objfile_data_key.
 293
 294    Some DWARF data cannot (currently) be shared across objfiles.  Such
 295    data is stored in this object.  */
 296
 297 struct dwarf2_per_objfile
 298 {
 299   dwarf2_per_objfile (struct objfile *objfile, dwarf2_per_bfd *per_bfd)
 300     : objfile (objfile), per_bfd (per_bfd)
 301   {}
 302
 303   ~dwarf2_per_objfile ();
 304
 305   /* Return pointer to string at .debug_line_str offset as read from BUF.
 306      BUF is assumed to be in a compilation unit described by CU_HEADER.
 307      Return *BYTES_READ_PTR count of bytes read from BUF.  */
 308   const char *read_line_string (const gdb_byte *buf,
 309                                 const struct comp_unit_head *cu_header,
 310                                 unsigned int *bytes_read_ptr);
 311
 312   /* Resize the M_SYMTABS vector to the needed size (the number of partial
 313      symtabs allocated by the per-bfd).  */
 314   void resize_symtabs ()
 315   {
 316     /* The symtabs vector should only grow, not shrink.  */
 317     gdb_assert (per_bfd->num_psymtabs () >= m_symtabs.size ());
 318
 319     m_symtabs.resize (per_bfd->num_psymtabs ());
 320   }
 321
 322   /* Return true if the symtab corresponding to PER_CU has been set,
 323      false otherwise.  */
 324   bool symtab_set_p (const dwarf2_per_cu_data *per_cu) const;
 325
 326   /* Return the compunit_symtab associated to PER_CU, if it has been created.  */
 327   compunit_symtab *get_symtab (const dwarf2_per_cu_data *per_cu) const;
 328
 329   /* Set the compunit_symtab associated to PER_CU.  */
 330   void set_symtab (const dwarf2_per_cu_data *per_cu, compunit_symtab *symtab);
 331
 332   /* Get the type_unit_group_unshareable corresponding to TU_GROUP.  If one
 333      does not exist, create it.  */
 334   type_unit_group_unshareable *get_type_unit_group_unshareable
 335     (type_unit_group *tu_group);
 336
 337   struct type *get_type_for_signatured_type (signatured_type *sig_type) const;
 338
 339   void set_type_for_signatured_type (signatured_type *sig_type,
 340                                      struct type *type);
 341
 342   /* Find an integer type SIZE_IN_BYTES bytes in size and return it.
 343      UNSIGNED_P controls if the integer is unsigned or not.  */
 344   struct type *int_type (int size_in_bytes, bool unsigned_p) const;
 345
 346   /* Get the dwarf2_cu matching PER_CU for this objfile.  */
 347   dwarf2_cu *get_cu (dwarf2_per_cu_data *per_cu);
 348
 349   /* Set the dwarf2_cu matching PER_CU for this objfile.  */
 350   void set_cu (dwarf2_per_cu_data *per_cu, dwarf2_cu *cu);
 351
 352   /* Remove/free the dwarf2_cu matching PER_CU for this objfile.  */
 353   void remove_cu (dwarf2_per_cu_data *per_cu);
 354
 355   /* Free all cached compilation units.  */
 356   void remove_all_cus ();
 357
 358   /* Increase the age counter on each CU compilation unit and free
 359      any that are too old.  */
 360   void age_comp_units ();
 361
 362   /* Back link.  */
 363   struct objfile *objfile;
 364
 365   /* Pointer to the data that is (possibly) shared between this objfile and
 366      other objfiles backed by the same BFD.  */
 367   struct dwarf2_per_bfd *per_bfd;
 368
 369   /* Table mapping type DIEs to their struct type *.
 370      This is nullptr if not allocated yet.
 371      The mapping is done via (CU/TU + DIE offset) -> type.  */
 372   htab_up die_type_hash;
 373
 374   /* Table containing line_header indexed by offset and offset_in_dwz.  */
 375   htab_up line_header_hash;
 376
 377 private:
 378   /* Hold the corresponding compunit_symtab for each CU or TU.  This
 379      is indexed by dwarf2_per_cu_data::index.  A NULL value means
 380      that the CU/TU has not been expanded yet.  */
 381   std::vector<compunit_symtab *> m_symtabs;
 382
 383   /* Map from a type unit group to the corresponding unshared
 384      structure.  */
 385   typedef std::unique_ptr<type_unit_group_unshareable>
 386     type_unit_group_unshareable_up;
 387
 388   std::unordered_map<type_unit_group *, type_unit_group_unshareable_up>
 389     m_type_units;
 390
 391   /* Map from signatured types to the corresponding struct type.  */
 392   std::unordered_map<signatured_type *, struct type *> m_type_map;
 393
 394   /* Map from the objfile-independent dwarf2_per_cu_data instances to the
 395      corresponding objfile-dependent dwarf2_cu instances.  */
 396   std::unordered_map<dwarf2_per_cu_data *, dwarf2_cu *> m_dwarf2_cus;
 397 };
 398
 399 /* Get the dwarf2_per_objfile associated to OBJFILE.  */
 400
 401 dwarf2_per_objfile *get_dwarf2_per_objfile (struct objfile *objfile);
 402
 403 /* A partial symtab specialized for DWARF.  */
 404 struct dwarf2_psymtab : public partial_symtab
 405 {
 406   dwarf2_psymtab (const char *filename, struct objfile *objfile,
 407                   dwarf2_per_cu_data *per_cu)
 408     : partial_symtab (filename, objfile, 0),
 409       per_cu_data (per_cu)
 410   {
 411   }
 412
 413   void read_symtab (struct objfile *) override;
 414   void expand_psymtab (struct objfile *) override;
 415   bool readin_p (struct objfile *) const override;
 416   compunit_symtab *get_compunit_symtab (struct objfile *) const override;
 417
 418   struct dwarf2_per_cu_data *per_cu_data;
 419 };
 420
 421 /* Persistent data held for a compilation unit, even when not
 422    processing it.  We put a pointer to this structure in the
 423    psymtab.  */
 424
 425 struct dwarf2_per_cu_data
 426 {
 427   /* The start offset and length of this compilation unit.
 428      NOTE: Unlike comp_unit_head.length, this length includes
 429      initial_length_size.
 430      If the DIE refers to a DWO file, this is always of the original die,
 431      not the DWO file.  */
 432   sect_offset sect_off;
 433   unsigned int length;
 434
 435   /* DWARF standard version this data has been read from (such as 4 or 5).  */
 436   short dwarf_version;
 437
 438   /* Flag indicating this compilation unit will be read in before
 439      any of the current compilation units are processed.  */
 440   unsigned int queued : 1;
 441
 442   /* This flag will be set when reading partial DIEs if we need to load
 443      absolutely all DIEs for this compilation unit, instead of just the ones
 444      we think are interesting.  It gets set if we look for a DIE in the
 445      hash table and don't find it.  */
 446   unsigned int load_all_dies : 1;
 447
 448   /* Non-zero if this CU is from .debug_types.
 449      Struct dwarf2_per_cu_data is contained in struct signatured_type iff
 450      this is non-zero.  */
 451   unsigned int is_debug_types : 1;
 452
 453   /* Non-zero if this CU is from the .dwz file.  */
 454   unsigned int is_dwz : 1;
 455
 456   /* Non-zero if reading a TU directly from a DWO file, bypassing the stub.
 457      This flag is only valid if is_debug_types is true.
 458      We can't read a CU directly from a DWO file: There are required
 459      attributes in the stub.  */
 460   unsigned int reading_dwo_directly : 1;
 461
 462   /* Non-zero if the TU has been read.
 463      This is used to assist the "Stay in DWO Optimization" for Fission:
 464      When reading a DWO, it's faster to read TUs from the DWO instead of
 465      fetching them from random other DWOs (due to comdat folding).
 466      If the TU has already been read, the optimization is unnecessary
 467      (and unwise - we don't want to change where gdb thinks the TU lives
 468      "midflight").
 469      This flag is only valid if is_debug_types is true.  */
 470   unsigned int tu_read : 1;
 471
 472   /* Our index in the unshared "symtabs" vector.  */
 473   unsigned index;
 474
 475   /* The section this CU/TU lives in.
 476      If the DIE refers to a DWO file, this is always the original die,
 477      not the DWO file.  */
 478   struct dwarf2_section_info *section;
 479
 480   /* The unit type of this CU.  */
 481   enum dwarf_unit_type unit_type;
 482
 483   /* The language of this CU.  */
 484   enum language lang;
 485
 486   /* Backlink to the owner of this.  */
 487   dwarf2_per_bfd *per_bfd;
 488
 489   /* DWARF header of this CU.  Note that dwarf2_cu reads its own version of the
 490      header, which may differ from this one, since it may pass rcuh_kind::TYPE
 491      to read_comp_unit_head, whereas for dwarf2_per_cu_data we always pass
 492      rcuh_kind::COMPILE.
 493
 494      Don't access this field directly, use the get_header method instead.  It
 495      should be private, but we can't make it private at the moment.  */
 496   mutable comp_unit_head m_header;
 497
 498   /* True if HEADER has been read in.
 499
 500      Don't access this field directly.  It should be private, but we can't make
 501      it private at the moment.  */
 502   mutable bool m_header_read_in;
 503
 504   /* When dwarf2_per_bfd::using_index is true, the 'quick' field
 505      is active.  Otherwise, the 'psymtab' field is active.  */
 506   union
 507   {
 508     /* The partial symbol table associated with this compilation unit,
 509        or NULL for unread partial units.  */
 510     dwarf2_psymtab *psymtab;
 511
 512     /* Data needed by the "quick" functions.  */
 513     struct dwarf2_per_cu_quick_data *quick;
 514   } v;
 515
 516   /* The CUs we import using DW_TAG_imported_unit.  This is filled in
 517      while reading psymtabs, used to compute the psymtab dependencies,
 518      and then cleared.  Then it is filled in again while reading full
 519      symbols, and only deleted when the objfile is destroyed.
 520
 521      This is also used to work around a difference between the way gold
 522      generates .gdb_index version <=7 and the way gdb does.  Arguably this
 523      is a gold bug.  For symbols coming from TUs, gold records in the index
 524      the CU that includes the TU instead of the TU itself.  This breaks
 525      dw2_lookup_symbol: It assumes that if the index says symbol X lives
 526      in CU/TU Y, then one need only expand Y and a subsequent lookup in Y
 527      will find X.  Alas TUs live in their own symtab, so after expanding CU Y
 528      we need to look in TU Z to find X.  Fortunately, this is akin to
 529      DW_TAG_imported_unit, so we just use the same mechanism: For
 530      .gdb_index version <=7 this also records the TUs that the CU referred
 531      to.  Concurrently with this change gdb was modified to emit version 8
 532      indices so we only pay a price for gold generated indices.
 533      http://sourceware.org/bugzilla/show_bug.cgi?id=15021.
 534
 535      This currently needs to be a public member due to how
 536      dwarf2_per_cu_data is allocated and used.  Ideally in future things
 537      could be refactored to make this private.  Until then please try to
 538      avoid direct access to this member, and instead use the helper
 539      functions above.  */
 540   std::vector <dwarf2_per_cu_data *> *imported_symtabs;
 541
 542   /* Return true of IMPORTED_SYMTABS is empty or not yet allocated.  */
 543   bool imported_symtabs_empty () const
 544   {
 545     return (imported_symtabs == nullptr || imported_symtabs->empty ());
 546   }
 547
 548   /* Push P to the back of IMPORTED_SYMTABS, allocated IMPORTED_SYMTABS
 549      first if required.  */
 550   void imported_symtabs_push (dwarf2_per_cu_data *p)
 551   {
 552     if (imported_symtabs == nullptr)
 553       imported_symtabs = new std::vector <dwarf2_per_cu_data *>;
 554     imported_symtabs->push_back (p);
 555   }
 556
 557   /* Return the size of IMPORTED_SYMTABS if it is allocated, otherwise
 558      return 0.  */
 559   size_t imported_symtabs_size () const
 560   {
 561     if (imported_symtabs == nullptr)
 562       return 0;
 563     return imported_symtabs->size ();
 564   }
 565
 566   /* Delete IMPORTED_SYMTABS and set the pointer back to nullptr.  */
 567   void imported_symtabs_free ()
 568   {
 569     delete imported_symtabs;
 570     imported_symtabs = nullptr;
 571   }
 572
 573   /* Get the header of this per_cu, reading it if necessary.  */
 574   const comp_unit_head *get_header () const;
 575
 576   /* Return the address size given in the compilation unit header for
 577      this CU.  */
 578   int addr_size () const;
 579
 580   /* Return the offset size given in the compilation unit header for
 581      this CU.  */
 582   int offset_size () const;
 583
 584   /* Return the DW_FORM_ref_addr size given in the compilation unit
 585      header for this CU.  */
 586   int ref_addr_size () const;
 587
 588   /* Return DWARF version number of this CU.  */
 589   short version () const
 590   {
 591     return dwarf_version;
 592   }
 593
 594   /* A type unit group has a per_cu object that is recognized by
 595      having no section.  */
 596   bool type_unit_group_p () const
 597   {
 598     return section == nullptr;
 599   }
 600 };
 601
 602 /* Entry in the signatured_types hash table.  */
 603
 604 struct signatured_type
 605 {
 606   /* The "per_cu" object of this type.
 607      This struct is used iff per_cu.is_debug_types.
 608      N.B.: This is the first member so that it's easy to convert pointers
 609      between them.  */
 610   struct dwarf2_per_cu_data per_cu;
 611
 612   /* The type's signature.  */
 613   ULONGEST signature;
 614
 615   /* Offset in the TU of the type's DIE, as read from the TU header.
 616      If this TU is a DWO stub and the definition lives in a DWO file
 617      (specified by DW_AT_GNU_dwo_name), this value is unusable.  */
 618   cu_offset type_offset_in_tu;
 619
 620   /* Offset in the section of the type's DIE.
 621      If the definition lives in a DWO file, this is the offset in the
 622      .debug_types.dwo section.
 623      The value is zero until the actual value is known.
 624      Zero is otherwise not a valid section offset.  */
 625   sect_offset type_offset_in_section;
 626
 627   /* Type units are grouped by their DW_AT_stmt_list entry so that they
 628      can share them.  This points to the containing symtab.  */
 629   struct type_unit_group *type_unit_group;
 630
 631   /* Containing DWO unit.
 632      This field is valid iff per_cu.reading_dwo_directly.  */
 633   struct dwo_unit *dwo_unit;
 634 };
 635
 636 /* Open the separate '.dwz' debug file, if needed.  Return NULL if
 637    there is no .gnu_debugaltlink section in the file.  Error if there
 638    is such a section but the file cannot be found.  */
 639
 640 extern dwz_file *dwarf2_get_dwz_file (dwarf2_per_bfd *per_bfd);
 641
 642 /* Return the type of the DIE at DIE_OFFSET in the CU named by
 643    PER_CU.  */
 644
 645 struct type *dwarf2_get_die_type (cu_offset die_offset,
 646                                   dwarf2_per_cu_data *per_cu,
 647                                   dwarf2_per_objfile *per_objfile);
 648
 649 /* Given an index in .debug_addr, fetch the value.
 650    NOTE: This can be called during dwarf expression evaluation,
 651    long after the debug information has been read, and thus per_cu->cu
 652    may no longer exist.  */
 653
 654 CORE_ADDR dwarf2_read_addr_index (dwarf2_per_cu_data *per_cu,
 655                                   dwarf2_per_objfile *per_objfile,
 656                                   unsigned int addr_index);
 657
 658 /* Return DWARF block referenced by DW_AT_location of DIE at SECT_OFF at PER_CU.
 659    Returned value is intended for DW_OP_call*.  Returned
 660    dwarf2_locexpr_baton->data has lifetime of
 661    PER_CU->DWARF2_PER_OBJFILE->OBJFILE.  */
 662
 663 struct dwarf2_locexpr_baton dwarf2_fetch_die_loc_sect_off
 664   (sect_offset sect_off, dwarf2_per_cu_data *per_cu,
 665    dwarf2_per_objfile *per_objfile,
 666    gdb::function_view<CORE_ADDR ()> get_frame_pc,
 667    bool resolve_abstract_p = false);
 668
 669 /* Like dwarf2_fetch_die_loc_sect_off, but take a CU
 670    offset.  */
 671
 672 struct dwarf2_locexpr_baton dwarf2_fetch_die_loc_cu_off
 673   (cu_offset offset_in_cu, dwarf2_per_cu_data *per_cu,
 674    dwarf2_per_objfile *per_objfile,
 675    gdb::function_view<CORE_ADDR ()> get_frame_pc);
 676
 677 /* If the DIE at SECT_OFF in PER_CU has a DW_AT_const_value, return a
 678    pointer to the constant bytes and set LEN to the length of the
 679    data.  If memory is needed, allocate it on OBSTACK.  If the DIE
 680    does not have a DW_AT_const_value, return NULL.  */
 681
 682 extern const gdb_byte *dwarf2_fetch_constant_bytes
 683   (sect_offset sect_off, dwarf2_per_cu_data *per_cu,
 684    dwarf2_per_objfile *per_objfile, obstack *obstack,
 685    LONGEST *len);
 686
 687 /* Return the type of the die at SECT_OFF in PER_CU.  Return NULL if no
 688    valid type for this die is found.  */
 689
 690 struct type *dwarf2_fetch_die_type_sect_off
 691   (sect_offset sect_off, dwarf2_per_cu_data *per_cu,
 692    dwarf2_per_objfile *per_objfile);
 693
 694 /* When non-zero, dump line number entries as they are read in.  */
 695 extern unsigned int dwarf_line_debug;
 696
 697 #endif /* DWARF2READ_H */