1 /* DWARF 2 debugging format support for GDB.
2 
3    Copyright (C) 1994-2021 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-head.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   int nr_tus;
46 };
47 
48 struct dwarf2_cu;
49 struct dwarf2_debug_sections;
50 struct dwarf2_per_bfd;
51 struct dwarf2_per_cu_data;
52 struct dwarf2_psymtab;
53 struct mapped_index;
54 struct mapped_debug_names;
55 struct signatured_type;
56 struct type_unit_group;
57 
58 /* One item on the queue of compilation units to read in full symbols
59    for.  */
60 struct dwarf2_queue_item
61 {
dwarf2_queue_itemdwarf2_queue_item62   dwarf2_queue_item (dwarf2_per_cu_data *cu, dwarf2_per_objfile *per_objfile,
63 		     enum language lang)
64     : per_cu (cu),
65       per_objfile (per_objfile),
66       pretend_language (lang)
67   {
68   }
69 
70   ~dwarf2_queue_item ();
71 
72   DISABLE_COPY_AND_ASSIGN (dwarf2_queue_item);
73 
74   dwarf2_per_cu_data *per_cu;
75   dwarf2_per_objfile *per_objfile;
76   enum language pretend_language;
77 };
78 
79 /* A deleter for dwarf2_per_cu_data that knows to downcast to
80    signatured_type as appropriate.  This approach lets us avoid a
81    virtual destructor, which saves a bit of space.  */
82 
83 struct dwarf2_per_cu_data_deleter
84 {
85   void operator() (dwarf2_per_cu_data *data);
86 };
87 
88 /* A specialization of unique_ptr for dwarf2_per_cu_data and
89    subclasses.  */
90 typedef std::unique_ptr<dwarf2_per_cu_data, dwarf2_per_cu_data_deleter>
91     dwarf2_per_cu_data_up;
92 
93 /* Persistent data held for a compilation unit, even when not
94    processing it.  We put a pointer to this structure in the
95    psymtab.  */
96 
97 struct dwarf2_per_cu_data
98 {
dwarf2_per_cu_datadwarf2_per_cu_data99   dwarf2_per_cu_data ()
100     : queued (false),
101       is_debug_types (false),
102       is_dwz (false),
103       reading_dwo_directly (false),
104       tu_read (false),
105       m_header_read_in (false),
106       unit_type {},
107       lang (language_unknown)
108   {
109   }
110 
111   /* The start offset and length of this compilation unit.
112      NOTE: Unlike comp_unit_head.length, this length includes
113      initial_length_size.
114      If the DIE refers to a DWO file, this is always of the original die,
115      not the DWO file.  */
116   sect_offset sect_off {};
117   unsigned int length = 0;
118 
119   /* DWARF standard version this data has been read from (such as 4 or 5).  */
120   unsigned char dwarf_version = 0;
121 
122   /* Flag indicating this compilation unit will be read in before
123      any of the current compilation units are processed.  */
124   unsigned int queued : 1;
125 
126   /* Non-zero if this CU is from .debug_types.
127      Struct dwarf2_per_cu_data is contained in struct signatured_type iff
128      this is non-zero.  */
129   unsigned int is_debug_types : 1;
130 
131   /* Non-zero if this CU is from the .dwz file.  */
132   unsigned int is_dwz : 1;
133 
134   /* Non-zero if reading a TU directly from a DWO file, bypassing the stub.
135      This flag is only valid if is_debug_types is true.
136      We can't read a CU directly from a DWO file: There are required
137      attributes in the stub.  */
138   unsigned int reading_dwo_directly : 1;
139 
140   /* Non-zero if the TU has been read.
141      This is used to assist the "Stay in DWO Optimization" for Fission:
142      When reading a DWO, it's faster to read TUs from the DWO instead of
143      fetching them from random other DWOs (due to comdat folding).
144      If the TU has already been read, the optimization is unnecessary
145      (and unwise - we don't want to change where gdb thinks the TU lives
146      "midflight").
147      This flag is only valid if is_debug_types is true.  */
148   unsigned int tu_read : 1;
149 
150   /* True if HEADER has been read in.
151 
152      Don't access this field directly.  It should be private, but we can't make
153      it private at the moment.  */
154   mutable bool m_header_read_in : 1;
155 
156   /* The unit type of this CU.  */
157   ENUM_BITFIELD (dwarf_unit_type) unit_type : 8;
158 
159   /* The language of this CU.  */
160   ENUM_BITFIELD (language) lang : LANGUAGE_BITS;
161 
162   /* Our index in the unshared "symtabs" vector.  */
163   unsigned index = 0;
164 
165   /* The section this CU/TU lives in.
166      If the DIE refers to a DWO file, this is always the original die,
167      not the DWO file.  */
168   struct dwarf2_section_info *section = nullptr;
169 
170   /* Backlink to the owner of this.  */
171   dwarf2_per_bfd *per_bfd = nullptr;
172 
173   /* DWARF header of this CU.  Note that dwarf2_cu reads its own version of the
174      header, which may differ from this one, since it may pass rcuh_kind::TYPE
175      to read_comp_unit_head, whereas for dwarf2_per_cu_data we always pass
176      rcuh_kind::COMPILE.
177 
178      Don't access this field directly, use the get_header method instead.  It
179      should be private, but we can't make it private at the moment.  */
180   mutable comp_unit_head m_header {};
181 
182   /* When dwarf2_per_bfd::using_index is true, the 'quick' field
183      is active.  Otherwise, the 'psymtab' field is active.  */
184   union
185   {
186     /* The partial symbol table associated with this compilation unit,
187        or NULL for unread partial units.  */
188     dwarf2_psymtab *psymtab;
189 
190     /* Data needed by the "quick" functions.  */
191     struct dwarf2_per_cu_quick_data *quick;
192   } v {};
193 
194   /* The CUs we import using DW_TAG_imported_unit.  This is filled in
195      while reading psymtabs, used to compute the psymtab dependencies,
196      and then cleared.  Then it is filled in again while reading full
197      symbols, and only deleted when the objfile is destroyed.
198 
199      This is also used to work around a difference between the way gold
200      generates .gdb_index version <=7 and the way gdb does.  Arguably this
201      is a gold bug.  For symbols coming from TUs, gold records in the index
202      the CU that includes the TU instead of the TU itself.  This breaks
203      dw2_lookup_symbol: It assumes that if the index says symbol X lives
204      in CU/TU Y, then one need only expand Y and a subsequent lookup in Y
205      will find X.  Alas TUs live in their own symtab, so after expanding CU Y
206      we need to look in TU Z to find X.  Fortunately, this is akin to
207      DW_TAG_imported_unit, so we just use the same mechanism: For
208      .gdb_index version <=7 this also records the TUs that the CU referred
209      to.  Concurrently with this change gdb was modified to emit version 8
210      indices so we only pay a price for gold generated indices.
211      http://sourceware.org/bugzilla/show_bug.cgi?id=15021.
212 
213      This currently needs to be a public member due to how
214      dwarf2_per_cu_data is allocated and used.  Ideally in future things
215      could be refactored to make this private.  Until then please try to
216      avoid direct access to this member, and instead use the helper
217      functions above.  */
218   std::vector <dwarf2_per_cu_data *> *imported_symtabs = nullptr;
219 
220   /* Return true of IMPORTED_SYMTABS is empty or not yet allocated.  */
imported_symtabs_emptydwarf2_per_cu_data221   bool imported_symtabs_empty () const
222   {
223     return (imported_symtabs == nullptr || imported_symtabs->empty ());
224   }
225 
226   /* Push P to the back of IMPORTED_SYMTABS, allocated IMPORTED_SYMTABS
227      first if required.  */
imported_symtabs_pushdwarf2_per_cu_data228   void imported_symtabs_push (dwarf2_per_cu_data *p)
229   {
230     if (imported_symtabs == nullptr)
231       imported_symtabs = new std::vector <dwarf2_per_cu_data *>;
232     imported_symtabs->push_back (p);
233   }
234 
235   /* Return the size of IMPORTED_SYMTABS if it is allocated, otherwise
236      return 0.  */
imported_symtabs_sizedwarf2_per_cu_data237   size_t imported_symtabs_size () const
238   {
239     if (imported_symtabs == nullptr)
240       return 0;
241     return imported_symtabs->size ();
242   }
243 
244   /* Delete IMPORTED_SYMTABS and set the pointer back to nullptr.  */
imported_symtabs_freedwarf2_per_cu_data245   void imported_symtabs_free ()
246   {
247     delete imported_symtabs;
248     imported_symtabs = nullptr;
249   }
250 
251   /* Get the header of this per_cu, reading it if necessary.  */
252   const comp_unit_head *get_header () const;
253 
254   /* Return the address size given in the compilation unit header for
255      this CU.  */
256   int addr_size () const;
257 
258   /* Return the offset size given in the compilation unit header for
259      this CU.  */
260   int offset_size () const;
261 
262   /* Return the DW_FORM_ref_addr size given in the compilation unit
263      header for this CU.  */
264   int ref_addr_size () const;
265 
266   /* Return DWARF version number of this CU.  */
versiondwarf2_per_cu_data267   short version () const
268   {
269     return dwarf_version;
270   }
271 
272   /* A type unit group has a per_cu object that is recognized by
273      having no section.  */
type_unit_group_pdwarf2_per_cu_data274   bool type_unit_group_p () const
275   {
276     return section == nullptr;
277   }
278 };
279 
280 /* Entry in the signatured_types hash table.  */
281 
282 struct signatured_type : public dwarf2_per_cu_data
283 {
signatured_typesignatured_type284   signatured_type (ULONGEST signature)
285     : signature (signature)
286   {}
287 
288   /* The type's signature.  */
289   ULONGEST signature;
290 
291   /* Offset in the TU of the type's DIE, as read from the TU header.
292      If this TU is a DWO stub and the definition lives in a DWO file
293      (specified by DW_AT_GNU_dwo_name), this value is unusable.  */
294   cu_offset type_offset_in_tu {};
295 
296   /* Offset in the section of the type's DIE.
297      If the definition lives in a DWO file, this is the offset in the
298      .debug_types.dwo section.
299      The value is zero until the actual value is known.
300      Zero is otherwise not a valid section offset.  */
301   sect_offset type_offset_in_section {};
302 
303   /* Type units are grouped by their DW_AT_stmt_list entry so that they
304      can share them.  This points to the containing symtab.  */
305   struct type_unit_group *type_unit_group = nullptr;
306 
307   /* Containing DWO unit.
308      This field is valid iff per_cu.reading_dwo_directly.  */
309   struct dwo_unit *dwo_unit = nullptr;
310 };
311 
312 using signatured_type_up = std::unique_ptr<signatured_type>;
313 
314 /* Some DWARF data can be shared across objfiles who share the same BFD,
315    this data is stored in this object.
316 
317    Two dwarf2_per_objfile objects representing objfiles sharing the same BFD
318    will point to the same instance of dwarf2_per_bfd, unless the BFD requires
319    relocation.  */
320 
321 struct dwarf2_per_bfd
322 {
323   /* Construct a dwarf2_per_bfd for OBFD.  NAMES points to the
324      dwarf2 section names, or is NULL if the standard ELF names are
325      used.  CAN_COPY is true for formats where symbol
326      interposition is possible and so symbol values must follow copy
327      relocation rules.  */
328   dwarf2_per_bfd (bfd *obfd, const dwarf2_debug_sections *names, bool can_copy);
329 
330   ~dwarf2_per_bfd ();
331 
332   DISABLE_COPY_AND_ASSIGN (dwarf2_per_bfd);
333 
334   /* Return the CU given its index.  */
get_cudwarf2_per_bfd335   dwarf2_per_cu_data *get_cu (int index) const
336   {
337     return this->all_comp_units[index].get ();
338   }
339 
340   /* A convenience function to allocate a dwarf2_per_cu_data.  The
341      returned object has its "index" field set properly.  The object
342      is allocated on the dwarf2_per_bfd obstack.  */
343   dwarf2_per_cu_data_up allocate_per_cu ();
344 
345   /* A convenience function to allocate a signatured_type.  The
346      returned object has its "index" field set properly.  The object
347      is allocated on the dwarf2_per_bfd obstack.  */
348   signatured_type_up allocate_signatured_type (ULONGEST signature);
349 
350 private:
351   /* This function is mapped across the sections and remembers the
352      offset and size of each of the debugging sections we are
353      interested in.  */
354   void locate_sections (bfd *abfd, asection *sectp,
355 			const dwarf2_debug_sections &names);
356 
357 public:
358   /* The corresponding BFD.  */
359   bfd *obfd;
360 
361   /* Objects that can be shared across objfiles are stored in this
362      obstack or on the psymtab obstack, while objects that are
363      objfile-specific are stored on the objfile obstack.  */
364   auto_obstack obstack;
365 
366   dwarf2_section_info info {};
367   dwarf2_section_info abbrev {};
368   dwarf2_section_info line {};
369   dwarf2_section_info loc {};
370   dwarf2_section_info loclists {};
371   dwarf2_section_info macinfo {};
372   dwarf2_section_info macro {};
373   dwarf2_section_info str {};
374   dwarf2_section_info str_offsets {};
375   dwarf2_section_info line_str {};
376   dwarf2_section_info ranges {};
377   dwarf2_section_info rnglists {};
378   dwarf2_section_info addr {};
379   dwarf2_section_info frame {};
380   dwarf2_section_info eh_frame {};
381   dwarf2_section_info gdb_index {};
382   dwarf2_section_info debug_names {};
383   dwarf2_section_info debug_aranges {};
384 
385   std::vector<dwarf2_section_info> types;
386 
387   /* Table of all the compilation units.  This is used to locate
388      the target compilation unit of a particular reference.  */
389   std::vector<dwarf2_per_cu_data_up> all_comp_units;
390 
391   /* Table of struct type_unit_group objects.
392      The hash key is the DW_AT_stmt_list value.  */
393   htab_up type_unit_groups;
394 
395   /* A table mapping .debug_types signatures to its signatured_type entry.
396      This is NULL if the .debug_types section hasn't been read in yet.  */
397   htab_up signatured_types;
398 
399   /* Type unit statistics, to see how well the scaling improvements
400      are doing.  */
401   struct tu_stats tu_stats {};
402 
403   /* A table mapping DW_AT_dwo_name values to struct dwo_file objects.
404      This is NULL if the table hasn't been allocated yet.  */
405   htab_up dwo_files;
406 
407   /* True if we've checked for whether there is a DWP file.  */
408   bool dwp_checked = false;
409 
410   /* The DWP file if there is one, or NULL.  */
411   std::unique_ptr<struct dwp_file> dwp_file;
412 
413   /* The shared '.dwz' file, if one exists.  This is used when the
414      original data was compressed using 'dwz -m'.  */
415   std::unique_ptr<struct dwz_file> dwz_file;
416 
417   /* Whether copy relocations are supported by this object format.  */
418   bool can_copy;
419 
420   /* A flag indicating whether this objfile has a section loaded at a
421      VMA of 0.  */
422   bool has_section_at_zero = false;
423 
424   /* True if we are using the mapped index,
425      or we are faking it for OBJF_READNOW's sake.  */
426   bool using_index = false;
427 
428   /* The mapped index, or NULL if .gdb_index is missing or not being used.  */
429   std::unique_ptr<mapped_index> index_table;
430 
431   /* The mapped index, or NULL if .debug_names is missing or not being used.  */
432   std::unique_ptr<mapped_debug_names> debug_names_table;
433 
434   /* When using index_table, this keeps track of all quick_file_names entries.
435      TUs typically share line table entries with a CU, so we maintain a
436      separate table of all line table entries to support the sharing.
437      Note that while there can be way more TUs than CUs, we've already
438      sorted all the TUs into "type unit groups", grouped by their
439      DW_AT_stmt_list value.  Therefore the only sharing done here is with a
440      CU and its associated TU group if there is one.  */
441   htab_up quick_file_names_table;
442 
443   /* Set during partial symbol reading, to prevent queueing of full
444      symbols.  */
445   bool reading_partial_symbols = false;
446 
447   /* The CUs we recently read.  */
448   std::vector<dwarf2_per_cu_data *> just_read_cus;
449 
450   /* If we loaded the index from an external file, this contains the
451      resources associated to the open file, memory mapping, etc.  */
452   std::unique_ptr<index_cache_resource> index_cache_res;
453 
454   /* Mapping from abstract origin DIE to concrete DIEs that reference it as
455      DW_AT_abstract_origin.  */
456   std::unordered_map<sect_offset, std::vector<sect_offset>,
457 		     gdb::hash_enum<sect_offset>>
458     abstract_to_concrete;
459 
460   /* CUs that are queued to be read.  */
461   gdb::optional<std::queue<dwarf2_queue_item>> queue;
462 
463   /* We keep a separate reference to the partial symtabs, in case we
464      are sharing them between objfiles.  This is only set after
465      partial symbols have been read the first time.  */
466   std::shared_ptr<psymtab_storage> partial_symtabs;
467 
468   /* The address map that is used by the DWARF index code.  */
469   struct addrmap *index_addrmap = nullptr;
470 };
471 
472 /* This is the per-objfile data associated with a type_unit_group.  */
473 
474 struct type_unit_group_unshareable
475 {
476   /* The compunit symtab.
477      Type units in a group needn't all be defined in the same source file,
478      so we create an essentially anonymous symtab as the compunit symtab.  */
479   struct compunit_symtab *compunit_symtab = nullptr;
480 
481   /* The number of symtabs from the line header.
482      The value here must match line_header.num_file_names.  */
483   unsigned int num_symtabs = 0;
484 
485   /* The symbol tables for this TU (obtained from the files listed in
486      DW_AT_stmt_list).
487      WARNING: The order of entries here must match the order of entries
488      in the line header.  After the first TU using this type_unit_group, the
489      line header for the subsequent TUs is recreated from this.  This is done
490      because we need to use the same symtabs for each TU using the same
491      DW_AT_stmt_list value.  Also note that symtabs may be repeated here,
492      there's no guarantee the line header doesn't have duplicate entries.  */
493   struct symtab **symtabs = nullptr;
494 };
495 
496 /* Collection of data recorded per objfile.
497    This hangs off of dwarf2_objfile_data_key.
498 
499    Some DWARF data cannot (currently) be shared across objfiles.  Such
500    data is stored in this object.  */
501 
502 struct dwarf2_per_objfile
503 {
dwarf2_per_objfiledwarf2_per_objfile504   dwarf2_per_objfile (struct objfile *objfile, dwarf2_per_bfd *per_bfd)
505     : objfile (objfile), per_bfd (per_bfd)
506   {}
507 
508   ~dwarf2_per_objfile ();
509 
510   /* Return pointer to string at .debug_line_str offset as read from BUF.
511      BUF is assumed to be in a compilation unit described by CU_HEADER.
512      Return *BYTES_READ_PTR count of bytes read from BUF.  */
513   const char *read_line_string (const gdb_byte *buf,
514 				const struct comp_unit_head *cu_header,
515 				unsigned int *bytes_read_ptr);
516 
517   /* Return true if the symtab corresponding to PER_CU has been set,
518      false otherwise.  */
519   bool symtab_set_p (const dwarf2_per_cu_data *per_cu) const;
520 
521   /* Return the compunit_symtab associated to PER_CU, if it has been created.  */
522   compunit_symtab *get_symtab (const dwarf2_per_cu_data *per_cu) const;
523 
524   /* Set the compunit_symtab associated to PER_CU.  */
525   void set_symtab (const dwarf2_per_cu_data *per_cu, compunit_symtab *symtab);
526 
527   /* Get the type_unit_group_unshareable corresponding to TU_GROUP.  If one
528      does not exist, create it.  */
529   type_unit_group_unshareable *get_type_unit_group_unshareable
530     (type_unit_group *tu_group);
531 
532   struct type *get_type_for_signatured_type (signatured_type *sig_type) const;
533 
534   void set_type_for_signatured_type (signatured_type *sig_type,
535 				     struct type *type);
536 
537   /* Find an integer type SIZE_IN_BYTES bytes in size and return it.
538      UNSIGNED_P controls if the integer is unsigned or not.  */
539   struct type *int_type (int size_in_bytes, bool unsigned_p) const;
540 
541   /* Get the dwarf2_cu matching PER_CU for this objfile.  */
542   dwarf2_cu *get_cu (dwarf2_per_cu_data *per_cu);
543 
544   /* Set the dwarf2_cu matching PER_CU for this objfile.  */
545   void set_cu (dwarf2_per_cu_data *per_cu, dwarf2_cu *cu);
546 
547   /* Remove/free the dwarf2_cu matching PER_CU for this objfile.  */
548   void remove_cu (dwarf2_per_cu_data *per_cu);
549 
550   /* Free all cached compilation units.  */
551   void remove_all_cus ();
552 
553   /* Increase the age counter on each CU compilation unit and free
554      any that are too old.  */
555   void age_comp_units ();
556 
557   /* Back link.  */
558   struct objfile *objfile;
559 
560   /* Pointer to the data that is (possibly) shared between this objfile and
561      other objfiles backed by the same BFD.  */
562   struct dwarf2_per_bfd *per_bfd;
563 
564   /* Table mapping type DIEs to their struct type *.
565      This is nullptr if not allocated yet.
566      The mapping is done via (CU/TU + DIE offset) -> type.  */
567   htab_up die_type_hash;
568 
569   /* Table containing line_header indexed by offset and offset_in_dwz.  */
570   htab_up line_header_hash;
571 
572   /* The CU containing the m_builder in scope.  */
573   dwarf2_cu *sym_cu = nullptr;
574 
575 private:
576   /* Hold the corresponding compunit_symtab for each CU or TU.  This
577      is indexed by dwarf2_per_cu_data::index.  A NULL value means
578      that the CU/TU has not been expanded yet.  */
579   std::vector<compunit_symtab *> m_symtabs;
580 
581   /* Map from a type unit group to the corresponding unshared
582      structure.  */
583   typedef std::unique_ptr<type_unit_group_unshareable>
584     type_unit_group_unshareable_up;
585 
586   std::unordered_map<type_unit_group *, type_unit_group_unshareable_up>
587     m_type_units;
588 
589   /* Map from signatured types to the corresponding struct type.  */
590   std::unordered_map<signatured_type *, struct type *> m_type_map;
591 
592   /* Map from the objfile-independent dwarf2_per_cu_data instances to the
593      corresponding objfile-dependent dwarf2_cu instances.  */
594   std::unordered_map<dwarf2_per_cu_data *, dwarf2_cu *> m_dwarf2_cus;
595 };
596 
597 /* Get the dwarf2_per_objfile associated to OBJFILE.  */
598 
599 dwarf2_per_objfile *get_dwarf2_per_objfile (struct objfile *objfile);
600 
601 /* A partial symtab specialized for DWARF.  */
602 struct dwarf2_psymtab : public partial_symtab
603 {
dwarf2_psymtabdwarf2_psymtab604   dwarf2_psymtab (const char *filename,
605 		  psymtab_storage *partial_symtabs,
606 		  objfile_per_bfd_storage *objfile_per_bfd,
607 		  dwarf2_per_cu_data *per_cu)
608     : partial_symtab (filename, partial_symtabs, objfile_per_bfd, 0),
609       per_cu_data (per_cu)
610   {
611   }
612 
613   void read_symtab (struct objfile *) override;
614   void expand_psymtab (struct objfile *) override;
615   bool readin_p (struct objfile *) const override;
616   compunit_symtab *get_compunit_symtab (struct objfile *) const override;
617 
618   struct dwarf2_per_cu_data *per_cu_data;
619 };
620 
621 /* Return the type of the DIE at DIE_OFFSET in the CU named by
622    PER_CU.  */
623 
624 struct type *dwarf2_get_die_type (cu_offset die_offset,
625 				  dwarf2_per_cu_data *per_cu,
626 				  dwarf2_per_objfile *per_objfile);
627 
628 /* Given an index in .debug_addr, fetch the value.
629    NOTE: This can be called during dwarf expression evaluation,
630    long after the debug information has been read, and thus per_cu->cu
631    may no longer exist.  */
632 
633 CORE_ADDR dwarf2_read_addr_index (dwarf2_per_cu_data *per_cu,
634 				  dwarf2_per_objfile *per_objfile,
635 				  unsigned int addr_index);
636 
637 /* Return DWARF block referenced by DW_AT_location of DIE at SECT_OFF at PER_CU.
638    Returned value is intended for DW_OP_call*.  Returned
639    dwarf2_locexpr_baton->data has lifetime of
640    PER_CU->DWARF2_PER_OBJFILE->OBJFILE.  */
641 
642 struct dwarf2_locexpr_baton dwarf2_fetch_die_loc_sect_off
643   (sect_offset sect_off, dwarf2_per_cu_data *per_cu,
644    dwarf2_per_objfile *per_objfile,
645    gdb::function_view<CORE_ADDR ()> get_frame_pc,
646    bool resolve_abstract_p = false);
647 
648 /* Like dwarf2_fetch_die_loc_sect_off, but take a CU
649    offset.  */
650 
651 struct dwarf2_locexpr_baton dwarf2_fetch_die_loc_cu_off
652   (cu_offset offset_in_cu, dwarf2_per_cu_data *per_cu,
653    dwarf2_per_objfile *per_objfile,
654    gdb::function_view<CORE_ADDR ()> get_frame_pc);
655 
656 /* If the DIE at SECT_OFF in PER_CU has a DW_AT_const_value, return a
657    pointer to the constant bytes and set LEN to the length of the
658    data.  If memory is needed, allocate it on OBSTACK.  If the DIE
659    does not have a DW_AT_const_value, return NULL.  */
660 
661 extern const gdb_byte *dwarf2_fetch_constant_bytes
662   (sect_offset sect_off, dwarf2_per_cu_data *per_cu,
663    dwarf2_per_objfile *per_objfile, obstack *obstack,
664    LONGEST *len);
665 
666 /* Return the type of the die at SECT_OFF in PER_CU.  Return NULL if no
667    valid type for this die is found.  If VAR_NAME is non-null, and if
668    the DIE in question is a variable declaration (definitions are
669    excluded), then *VAR_NAME is set to the variable's name.  */
670 
671 struct type *dwarf2_fetch_die_type_sect_off
672   (sect_offset sect_off, dwarf2_per_cu_data *per_cu,
673    dwarf2_per_objfile *per_objfile,
674    const char **var_name = nullptr);
675 
676 /* When non-zero, dump line number entries as they are read in.  */
677 extern unsigned int dwarf_line_debug;
678 
679 /* Dwarf2 sections that can be accessed by dwarf2_get_section_info.  */
680 enum dwarf2_section_enum {
681   DWARF2_DEBUG_FRAME,
682   DWARF2_EH_FRAME
683 };
684 
685 extern void dwarf2_get_section_info (struct objfile *,
686                                      enum dwarf2_section_enum,
687 				     asection **, const gdb_byte **,
688 				     bfd_size_type *);
689 
690 #endif /* DWARF2READ_H */
691