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 /* Hash function for an abbrev.  */
  34
  35 static hashval_t
  36 hash_abbrev (const void *item)
  37 {
  38   const struct abbrev_info *info = (const struct abbrev_info *) item;
  39   return info->number;
  40 }
  41
  42 /* Comparison function for abbrevs.  */
  43
  44 static int
  45 eq_abbrev (const void *lhs, const void *rhs)
  46 {
  47   const struct abbrev_info *l_info = (const struct abbrev_info *) lhs;
  48   const struct abbrev_info *r_info = (const struct abbrev_info *) rhs;
  49   return l_info->number == r_info->number;
  50 }
  51
  52 /* Abbreviation tables.
  53
  54    In DWARF version 2, the description of the debugging information is
  55    stored in a separate .debug_abbrev section.  Before we read any
  56    dies from a section we read in all abbreviations and install them
  57    in a hash table.  */
  58
  59 abbrev_table::abbrev_table (sect_offset off)
  60   : sect_off (off),
  61     m_abbrevs (htab_create_alloc (20, hash_abbrev, eq_abbrev,
  62                                   nullptr, xcalloc, xfree))
  63 {
  64 }
  65
  66 /* Allocate space for a struct abbrev_info object in ABBREV_TABLE.  */
  67
  68 struct abbrev_info *
  69 abbrev_table::alloc_abbrev ()
  70 {
  71   struct abbrev_info *abbrev;
  72
  73   abbrev = XOBNEW (&m_abbrev_obstack, struct abbrev_info);
  74   memset (abbrev, 0, sizeof (struct abbrev_info));
  75
  76   return abbrev;
  77 }
  78
  79 /* Add an abbreviation to the table.  */
  80
  81 void
  82 abbrev_table::add_abbrev (unsigned int abbrev_number,
  83                           struct abbrev_info *abbrev)
  84 {
  85   void **slot = htab_find_slot (m_abbrevs.get (), abbrev, INSERT);
  86   *slot = abbrev;
  87 }
  88
  89 /* Look up an abbrev in the table.
  90    Returns NULL if the abbrev is not found.  */
  91
  92 struct abbrev_info *
  93 abbrev_table::lookup_abbrev (unsigned int abbrev_number)
  94 {
  95   struct abbrev_info search;
  96   search.number = abbrev_number;
  97
  98   return (struct abbrev_info *) htab_find (m_abbrevs.get (), &search);
  99 }
 100
 101 /* Read in an abbrev table.  */
 102
 103 abbrev_table_up
 104 abbrev_table::read (struct objfile *objfile,
 105                     struct dwarf2_section_info *section,
 106                     sect_offset sect_off)
 107 {
 108   bfd *abfd = section->get_bfd_owner ();
 109   const gdb_byte *abbrev_ptr;
 110   struct abbrev_info *cur_abbrev;
 111   unsigned int abbrev_number, bytes_read, abbrev_name;
 112   unsigned int abbrev_form;
 113   std::vector<struct attr_abbrev> cur_attrs;
 114
 115   abbrev_table_up abbrev_table (new struct abbrev_table (sect_off));
 116
 117   section->read (objfile);
 118   abbrev_ptr = section->buffer + to_underlying (sect_off);
 119   abbrev_number = read_unsigned_leb128 (abfd, abbrev_ptr, &bytes_read);
 120   abbrev_ptr += bytes_read;
 121
 122   /* Loop until we reach an abbrev number of 0.  */
 123   while (abbrev_number)
 124     {
 125       cur_attrs.clear ();
 126       cur_abbrev = abbrev_table->alloc_abbrev ();
 127
 128       /* read in abbrev header */
 129       cur_abbrev->number = abbrev_number;
 130       cur_abbrev->tag
 131         = (enum dwarf_tag) read_unsigned_leb128 (abfd, abbrev_ptr, &bytes_read);
 132       abbrev_ptr += bytes_read;
 133       cur_abbrev->has_children = read_1_byte (abfd, abbrev_ptr);
 134       abbrev_ptr += 1;
 135
 136       /* now read in declarations */
 137       for (;;)
 138         {
 139           LONGEST implicit_const;
 140
 141           abbrev_name = read_unsigned_leb128 (abfd, abbrev_ptr, &bytes_read);
 142           abbrev_ptr += bytes_read;
 143           abbrev_form = read_unsigned_leb128 (abfd, abbrev_ptr, &bytes_read);
 144           abbrev_ptr += bytes_read;
 145           if (abbrev_form == DW_FORM_implicit_const)
 146             {
 147               implicit_const = read_signed_leb128 (abfd, abbrev_ptr,
 148                                                    &bytes_read);
 149               abbrev_ptr += bytes_read;
 150             }
 151           else
 152             {
 153               /* Initialize it due to a false compiler warning.  */
 154               implicit_const = -1;
 155             }
 156
 157           if (abbrev_name == 0)
 158             break;
 159
 160           cur_attrs.emplace_back ();
 161           struct attr_abbrev &cur_attr = cur_attrs.back ();
 162           cur_attr.name = (enum dwarf_attribute) abbrev_name;
 163           cur_attr.form = (enum dwarf_form) abbrev_form;
 164           cur_attr.implicit_const = implicit_const;
 165         }
 166
 167       cur_abbrev->num_attrs = cur_attrs.size ();
 168       cur_abbrev->attrs =
 169         XOBNEWVEC (&abbrev_table->m_abbrev_obstack, struct attr_abbrev,
 170                    cur_abbrev->num_attrs);
 171       if (!cur_attrs.empty ())
 172         memcpy (cur_abbrev->attrs, cur_attrs.data (),
 173                 cur_abbrev->num_attrs * sizeof (struct attr_abbrev));
 174
 175       abbrev_table->add_abbrev (abbrev_number, cur_abbrev);
 176
 177       /* Get next abbreviation.
 178          Under Irix6 the abbreviations for a compilation unit are not
 179          always properly terminated with an abbrev number of 0.
 180          Exit loop if we encounter an abbreviation which we have
 181          already read (which means we are about to read the abbreviations
 182          for the next compile unit) or if the end of the abbreviation
 183          table is reached.  */
 184       if ((unsigned int) (abbrev_ptr - section->buffer) >= section->size)
 185         break;
 186       abbrev_number = read_unsigned_leb128 (abfd, abbrev_ptr, &bytes_read);
 187       abbrev_ptr += bytes_read;
 188       if (abbrev_table->lookup_abbrev (abbrev_number) != NULL)
 189         break;
 190     }
 191
 192   return abbrev_table;
 193 }