gdb/dwarf2/abbrev.c

   1 /* DWARF 2 abbreviations
   2
   3    Copyright (C) 1994-2020 Free Software Foundation, Inc.
   4
   5    Adapted by Gary Funck (gary@intrepid.com), Intrepid Technology,
   6    Inc.  with support from Florida State University (under contract
   7    with the Ada Joint Program Office), and Silicon Graphics, Inc.
   8    Initial contribution by Brent Benson, Harris Computer Systems, Inc.,
   9    based on Fred Fish's (Cygnus Support) implementation of DWARF 1
  10    support.
  11
  12    This file is part of GDB.
  13
  14    This program is free software; you can redistribute it and/or modify
  15    it under the terms of the GNU General Public License as published by
  16    the Free Software Foundation; either version 3 of the License, or
  17    (at your option) any later version.
  18
  19    This program is distributed in the hope that it will be useful,
  20    but WITHOUT ANY WARRANTY; without even the implied warranty of
  21    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  22    GNU General Public License for more details.
  23
  24    You should have received a copy of the GNU General Public License
  25    along with this program.  If not, see <http://www.gnu.org/licenses/>.  */
  26
  27 #include "defs.h"
  28 #include "dwarf2/read.h"
  29 #include "dwarf2/abbrev.h"
  30 #include "dwarf2/leb.h"
  31 #include "bfd.h"
  32
  33 /* Abbreviation tables.
  34
  35    In DWARF version 2, the description of the debugging information is
  36    stored in a separate .debug_abbrev section.  Before we read any
  37    dies from a section we read in all abbreviations and install them
  38    in a hash table.  */
  39
  40 /* Allocate space for a struct abbrev_info object in ABBREV_TABLE.  */
  41
  42 struct abbrev_info *
  43 abbrev_table::alloc_abbrev ()
  44 {
  45   struct abbrev_info *abbrev;
  46
  47   abbrev = XOBNEW (&m_abbrev_obstack, struct abbrev_info);
  48   memset (abbrev, 0, sizeof (struct abbrev_info));
  49
  50   return abbrev;
  51 }
  52
  53 /* Add an abbreviation to the table.  */
  54
  55 void
  56 abbrev_table::add_abbrev (unsigned int abbrev_number,
  57                           struct abbrev_info *abbrev)
  58 {
  59   unsigned int hash_number;
  60
  61   hash_number = abbrev_number % ABBREV_HASH_SIZE;
  62   abbrev->next = m_abbrevs[hash_number];
  63   m_abbrevs[hash_number] = abbrev;
  64 }
  65
  66 /* Look up an abbrev in the table.
  67    Returns NULL if the abbrev is not found.  */
  68
  69 struct abbrev_info *
  70 abbrev_table::lookup_abbrev (unsigned int abbrev_number)
  71 {
  72   unsigned int hash_number;
  73   struct abbrev_info *abbrev;
  74
  75   hash_number = abbrev_number % ABBREV_HASH_SIZE;
  76   abbrev = m_abbrevs[hash_number];
  77
  78   while (abbrev)
  79     {
  80       if (abbrev->number == abbrev_number)
  81         return abbrev;
  82       abbrev = abbrev->next;
  83     }
  84   return NULL;
  85 }
  86
  87 /* Read in an abbrev table.  */
  88
  89 abbrev_table_up
  90 abbrev_table::read (struct objfile *objfile,
  91                     struct dwarf2_section_info *section,
  92                     sect_offset sect_off)
  93 {
  94   bfd *abfd = section->get_bfd_owner ();
  95   const gdb_byte *abbrev_ptr;
  96   struct abbrev_info *cur_abbrev;
  97   unsigned int abbrev_number, bytes_read, abbrev_name;
  98   unsigned int abbrev_form;
  99   std::vector<struct attr_abbrev> cur_attrs;
 100
 101   abbrev_table_up abbrev_table (new struct abbrev_table (sect_off));
 102
 103   section->read (objfile);
 104   abbrev_ptr = section->buffer + to_underlying (sect_off);
 105   abbrev_number = read_unsigned_leb128 (abfd, abbrev_ptr, &bytes_read);
 106   abbrev_ptr += bytes_read;
 107
 108   /* Loop until we reach an abbrev number of 0.  */
 109   while (abbrev_number)
 110     {
 111       cur_attrs.clear ();
 112       cur_abbrev = abbrev_table->alloc_abbrev ();
 113
 114       /* read in abbrev header */
 115       cur_abbrev->number = abbrev_number;
 116       cur_abbrev->tag
 117         = (enum dwarf_tag) read_unsigned_leb128 (abfd, abbrev_ptr, &bytes_read);
 118       abbrev_ptr += bytes_read;
 119       cur_abbrev->has_children = read_1_byte (abfd, abbrev_ptr);
 120       abbrev_ptr += 1;
 121
 122       /* now read in declarations */
 123       for (;;)
 124         {
 125           LONGEST implicit_const;
 126
 127           abbrev_name = read_unsigned_leb128 (abfd, abbrev_ptr, &bytes_read);
 128           abbrev_ptr += bytes_read;
 129           abbrev_form = read_unsigned_leb128 (abfd, abbrev_ptr, &bytes_read);
 130           abbrev_ptr += bytes_read;
 131           if (abbrev_form == DW_FORM_implicit_const)
 132             {
 133               implicit_const = read_signed_leb128 (abfd, abbrev_ptr,
 134                                                    &bytes_read);
 135               abbrev_ptr += bytes_read;
 136             }
 137           else
 138             {
 139               /* Initialize it due to a false compiler warning.  */
 140               implicit_const = -1;
 141             }
 142
 143           if (abbrev_name == 0)
 144             break;
 145
 146           cur_attrs.emplace_back ();
 147           struct attr_abbrev &cur_attr = cur_attrs.back ();
 148           cur_attr.name = (enum dwarf_attribute) abbrev_name;
 149           cur_attr.form = (enum dwarf_form) abbrev_form;
 150           cur_attr.implicit_const = implicit_const;
 151           ++cur_abbrev->num_attrs;
 152         }
 153
 154       cur_abbrev->attrs =
 155         XOBNEWVEC (&abbrev_table->m_abbrev_obstack, struct attr_abbrev,
 156                    cur_abbrev->num_attrs);
 157       memcpy (cur_abbrev->attrs, cur_attrs.data (),
 158               cur_abbrev->num_attrs * sizeof (struct attr_abbrev));
 159
 160       abbrev_table->add_abbrev (abbrev_number, cur_abbrev);
 161
 162       /* Get next abbreviation.
 163          Under Irix6 the abbreviations for a compilation unit are not
 164          always properly terminated with an abbrev number of 0.
 165          Exit loop if we encounter an abbreviation which we have
 166          already read (which means we are about to read the abbreviations
 167          for the next compile unit) or if the end of the abbreviation
 168          table is reached.  */
 169       if ((unsigned int) (abbrev_ptr - section->buffer) >= section->size)
 170         break;
 171       abbrev_number = read_unsigned_leb128 (abfd, abbrev_ptr, &bytes_read);
 172       abbrev_ptr += bytes_read;
 173       if (abbrev_table->lookup_abbrev (abbrev_number) != NULL)
 174         break;
 175     }
 176
 177   return abbrev_table;
 178 }