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