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[binutils.git] / gold / object.cc

// object.cc -- support for an object file for linking in gold

// Copyright 2006, 2007, 2008 Free Software Foundation, Inc.
// Written by Ian Lance Taylor <iant@google.com>.

// This file is part of gold.

// This program is free software; you can redistribute it and/or modify
// it under the terms of the GNU General Public License as published by
// the Free Software Foundation; either version 3 of the License, or
// (at your option) any later version.

// This program is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
// GNU General Public License for more details.

// You should have received a copy of the GNU General Public License
// along with this program; if not, write to the Free Software
// Foundation, Inc., 51 Franklin Street - Fifth Floor, Boston,
// MA 02110-1301, USA.

#include "gold.h"

#include <cerrno>
#include <cstring>
#include <cstdarg>
#include "demangle.h"
#include "libiberty.h"

#include "target-select.h"
#include "dwarf_reader.h"
#include "layout.h"
#include "output.h"
#include "symtab.h"
#include "reloc.h"
#include "object.h"
#include "dynobj.h"

namespace gold
{

// Class Xindex.

// Initialize the symtab_xindex_ array.  Find the SHT_SYMTAB_SHNDX
// section and read it in.  SYMTAB_SHNDX is the index of the symbol
// table we care about.

template<int size, bool big_endian>
void
Xindex::initialize_symtab_xindex(Object* object, unsigned int symtab_shndx)
{
  if (!this->symtab_xindex_.empty())
    return;

  gold_assert(symtab_shndx != 0);

  // Look through the sections in reverse order, on the theory that it
  // is more likely to be near the end than the beginning.
  unsigned int i = object->shnum();
  while (i > 0)
    {
      --i;
      if (object->section_type(i) == elfcpp::SHT_SYMTAB_SHNDX
          && this->adjust_shndx(object->section_link(i)) == symtab_shndx)
        {
          this->read_symtab_xindex<size, big_endian>(object, i, NULL);
          return;
        }
    }

  object->error(_("missing SHT_SYMTAB_SHNDX section"));
}

// Read in the symtab_xindex_ array, given the section index of the
// SHT_SYMTAB_SHNDX section.  If PSHDRS is not NULL, it points at the
// section headers.

template<int size, bool big_endian>
void
Xindex::read_symtab_xindex(Object* object, unsigned int xindex_shndx,
                           const unsigned char* pshdrs)
{
  section_size_type bytecount;
  const unsigned char* contents;
  if (pshdrs == NULL)
    contents = object->section_contents(xindex_shndx, &bytecount, false);
  else
    {
      const unsigned char* p = (pshdrs
                                + (xindex_shndx
                                   * elfcpp::Elf_sizes<size>::shdr_size));
      typename elfcpp::Shdr<size, big_endian> shdr(p);
      bytecount = convert_to_section_size_type(shdr.get_sh_size());
      contents = object->get_view(shdr.get_sh_offset(), bytecount, true, false);
    }

  gold_assert(this->symtab_xindex_.empty());
  this->symtab_xindex_.reserve(bytecount / 4);
  for (section_size_type i = 0; i < bytecount; i += 4)
    {
      unsigned int shndx = elfcpp::Swap<32, big_endian>::readval(contents + i);
      // We preadjust the section indexes we save.
      this->symtab_xindex_.push_back(this->adjust_shndx(shndx));
    }
}

// Symbol symndx has a section of SHN_XINDEX; return the real section
// index.

unsigned int
Xindex::sym_xindex_to_shndx(Object* object, unsigned int symndx)
{
  if (symndx >= this->symtab_xindex_.size())
    {
      object->error(_("symbol %u out of range for SHT_SYMTAB_SHNDX section"),
                    symndx);
      return elfcpp::SHN_UNDEF;
    }
  unsigned int shndx = this->symtab_xindex_[symndx];
  if (shndx < elfcpp::SHN_LORESERVE || shndx >= object->shnum())
    {
      object->error(_("extended index for symbol %u out of range: %u"),
                    symndx, shndx);
      return elfcpp::SHN_UNDEF;
    }
  return shndx;
}

// Class Object.

// Set the target based on fields in the ELF file header.

void
Object::set_target(int machine, int size, bool big_endian, int osabi,
                   int abiversion)
{
  Target* target = select_target(machine, size, big_endian, osabi, abiversion);
  if (target == NULL)
    gold_fatal(_("%s: unsupported ELF machine number %d"),
               this->name().c_str(), machine);
  this->target_ = target;
}

// Report an error for this object file.  This is used by the
// elfcpp::Elf_file interface, and also called by the Object code
// itself.

void
Object::error(const char* format, ...) const
{
  va_list args;
  va_start(args, format);
  char* buf = NULL;
  if (vasprintf(&buf, format, args) < 0)
    gold_nomem();
  va_end(args);
  gold_error(_("%s: %s"), this->name().c_str(), buf);
  free(buf);
}

// Return a view of the contents of a section.

const unsigned char*
Object::section_contents(unsigned int shndx, section_size_type* plen,
                         bool cache)
{
  Location loc(this->do_section_contents(shndx));
  *plen = convert_to_section_size_type(loc.data_size);
  return this->get_view(loc.file_offset, *plen, true, cache);
}

// Read the section data into SD.  This is code common to Sized_relobj
// and Sized_dynobj, so we put it into Object.

template<int size, bool big_endian>
void
Object::read_section_data(elfcpp::Elf_file<size, big_endian, Object>* elf_file,
                          Read_symbols_data* sd)
{
  const int shdr_size = elfcpp::Elf_sizes<size>::shdr_size;

  // Read the section headers.
  const off_t shoff = elf_file->shoff();
  const unsigned int shnum = this->shnum();
  sd->section_headers = this->get_lasting_view(shoff, shnum * shdr_size,
                                               true, true);

  // Read the section names.
  const unsigned char* pshdrs = sd->section_headers->data();
  const unsigned char* pshdrnames = pshdrs + elf_file->shstrndx() * shdr_size;
  typename elfcpp::Shdr<size, big_endian> shdrnames(pshdrnames);

  if (shdrnames.get_sh_type() != elfcpp::SHT_STRTAB)
    this->error(_("section name section has wrong type: %u"),
                static_cast<unsigned int>(shdrnames.get_sh_type()));

  sd->section_names_size =
    convert_to_section_size_type(shdrnames.get_sh_size());
  sd->section_names = this->get_lasting_view(shdrnames.get_sh_offset(),
                                             sd->section_names_size, false,
                                             false);
}

// If NAME is the name of a special .gnu.warning section, arrange for
// the warning to be issued.  SHNDX is the section index.  Return
// whether it is a warning section.

bool
Object::handle_gnu_warning_section(const char* name, unsigned int shndx,
                                   Symbol_table* symtab)
{
  const char warn_prefix[] = ".gnu.warning.";
  const int warn_prefix_len = sizeof warn_prefix - 1;
  if (strncmp(name, warn_prefix, warn_prefix_len) == 0)
    {
      // Read the section contents to get the warning text.  It would
      // be nicer if we only did this if we have to actually issue a
      // warning.  Unfortunately, warnings are issued as we relocate
      // sections.  That means that we can not lock the object then,
      // as we might try to issue the same warning multiple times
      // simultaneously.
      section_size_type len;
      const unsigned char* contents = this->section_contents(shndx, &len,
                                                             false);
      std::string warning(reinterpret_cast<const char*>(contents), len);
      symtab->add_warning(name + warn_prefix_len, this, warning);
      return true;
    }
  return false;
}

// Class Sized_relobj.

template<int size, bool big_endian>
Sized_relobj<size, big_endian>::Sized_relobj(
    const std::string& name,
    Input_file* input_file,
    off_t offset,
    const elfcpp::Ehdr<size, big_endian>& ehdr)
  : Relobj(name, input_file, offset),
    elf_file_(this, ehdr),
    symtab_shndx_(-1U),
    local_symbol_count_(0),
    output_local_symbol_count_(0),
    output_local_dynsym_count_(0),
    symbols_(),
    local_symbol_offset_(0),
    local_dynsym_offset_(0),
    local_values_(),
    local_got_offsets_(),
    kept_comdat_sections_(),
    comdat_groups_(),
    has_eh_frame_(false)
{
}

template<int size, bool big_endian>
Sized_relobj<size, big_endian>::~Sized_relobj()
{
}

// Set up an object file based on the file header.  This sets up the
// target and reads the section information.

template<int size, bool big_endian>
void
Sized_relobj<size, big_endian>::setup(
    const elfcpp::Ehdr<size, big_endian>& ehdr)
{
  this->set_target(ehdr.get_e_machine(), size, big_endian,
                   ehdr.get_e_ident()[elfcpp::EI_OSABI],
                   ehdr.get_e_ident()[elfcpp::EI_ABIVERSION]);

  const unsigned int shnum = this->elf_file_.shnum();
  this->set_shnum(shnum);
}

// Find the SHT_SYMTAB section, given the section headers.  The ELF
// standard says that maybe in the future there can be more than one
// SHT_SYMTAB section.  Until somebody figures out how that could
// work, we assume there is only one.

template<int size, bool big_endian>
void
Sized_relobj<size, big_endian>::find_symtab(const unsigned char* pshdrs)
{
  const unsigned int shnum = this->shnum();
  this->symtab_shndx_ = 0;
  if (shnum > 0)
    {
      // Look through the sections in reverse order, since gas tends
      // to put the symbol table at the end.
      const unsigned char* p = pshdrs + shnum * This::shdr_size;
      unsigned int i = shnum;
      unsigned int xindex_shndx = 0;
      unsigned int xindex_link = 0;
      while (i > 0)
        {
          --i;
          p -= This::shdr_size;
          typename This::Shdr shdr(p);
          if (shdr.get_sh_type() == elfcpp::SHT_SYMTAB)
            {
              this->symtab_shndx_ = i;
              if (xindex_shndx > 0 && xindex_link == i)
                {
                  Xindex* xindex =
                    new Xindex(this->elf_file_.large_shndx_offset());
                  xindex->read_symtab_xindex<size, big_endian>(this,
                                                               xindex_shndx,
                                                               pshdrs);
                  this->set_xindex(xindex);
                }
              break;
            }

          // Try to pick up the SHT_SYMTAB_SHNDX section, if there is
          // one.  This will work if it follows the SHT_SYMTAB
          // section.
          if (shdr.get_sh_type() == elfcpp::SHT_SYMTAB_SHNDX)
            {
              xindex_shndx = i;
              xindex_link = this->adjust_shndx(shdr.get_sh_link());
            }
        }
    }
}

// Return the Xindex structure to use for object with lots of
// sections.

template<int size, bool big_endian>
Xindex*
Sized_relobj<size, big_endian>::do_initialize_xindex()
{
  gold_assert(this->symtab_shndx_ != -1U);
  Xindex* xindex = new Xindex(this->elf_file_.large_shndx_offset());
  xindex->initialize_symtab_xindex<size, big_endian>(this, this->symtab_shndx_);
  return xindex;
}

// Return whether SHDR has the right type and flags to be a GNU
// .eh_frame section.

template<int size, bool big_endian>
bool
Sized_relobj<size, big_endian>::check_eh_frame_flags(
    const elfcpp::Shdr<size, big_endian>* shdr) const
{
  return (shdr->get_sh_type() == elfcpp::SHT_PROGBITS
          && (shdr->get_sh_flags() & elfcpp::SHF_ALLOC) != 0);
}

// Return whether there is a GNU .eh_frame section, given the section
// headers and the section names.

template<int size, bool big_endian>
bool
Sized_relobj<size, big_endian>::find_eh_frame(
    const unsigned char* pshdrs,
    const char* names,
    section_size_type names_size) const
{
  const unsigned int shnum = this->shnum();
  const unsigned char* p = pshdrs + This::shdr_size;
  for (unsigned int i = 1; i < shnum; ++i, p += This::shdr_size)
    {
      typename This::Shdr shdr(p);
      if (this->check_eh_frame_flags(&shdr))
        {
          if (shdr.get_sh_name() >= names_size)
            {
              this->error(_("bad section name offset for section %u: %lu"),
                          i, static_cast<unsigned long>(shdr.get_sh_name()));
              continue;
            }

          const char* name = names + shdr.get_sh_name();
          if (strcmp(name, ".eh_frame") == 0)
            return true;
        }
    }
  return false;
}

// Read the sections and symbols from an object file.

template<int size, bool big_endian>
void
Sized_relobj<size, big_endian>::do_read_symbols(Read_symbols_data* sd)
{
  this->read_section_data(&this->elf_file_, sd);

  const unsigned char* const pshdrs = sd->section_headers->data();

  this->find_symtab(pshdrs);

  const unsigned char* namesu = sd->section_names->data();
  const char* names = reinterpret_cast<const char*>(namesu);
  if (memmem(names, sd->section_names_size, ".eh_frame", 10) != NULL)
    {
      if (this->find_eh_frame(pshdrs, names, sd->section_names_size))
        this->has_eh_frame_ = true;
    }

  sd->symbols = NULL;
  sd->symbols_size = 0;
  sd->external_symbols_offset = 0;
  sd->symbol_names = NULL;
  sd->symbol_names_size = 0;

  if (this->symtab_shndx_ == 0)
    {
      // No symbol table.  Weird but legal.
      return;
    }

  // Get the symbol table section header.
  typename This::Shdr symtabshdr(pshdrs
                                 + this->symtab_shndx_ * This::shdr_size);
  gold_assert(symtabshdr.get_sh_type() == elfcpp::SHT_SYMTAB);

  // If this object has a .eh_frame section, we need all the symbols.
  // Otherwise we only need the external symbols.  While it would be
  // simpler to just always read all the symbols, I've seen object
  // files with well over 2000 local symbols, which for a 64-bit
  // object file format is over 5 pages that we don't need to read
  // now.

  const int sym_size = This::sym_size;
  const unsigned int loccount = symtabshdr.get_sh_info();
  this->local_symbol_count_ = loccount;
  this->local_values_.resize(loccount);
  section_offset_type locsize = loccount * sym_size;
  off_t dataoff = symtabshdr.get_sh_offset();
  section_size_type datasize =
    convert_to_section_size_type(symtabshdr.get_sh_size());
  off_t extoff = dataoff + locsize;
  section_size_type extsize = datasize - locsize;

  off_t readoff = this->has_eh_frame_ ? dataoff : extoff;
  section_size_type readsize = this->has_eh_frame_ ? datasize : extsize;

  if (readsize == 0)
    {
      // No external symbols.  Also weird but also legal.
      return;
    }

  File_view* fvsymtab = this->get_lasting_view(readoff, readsize, true, false);

  // Read the section header for the symbol names.
  unsigned int strtab_shndx = this->adjust_shndx(symtabshdr.get_sh_link());
  if (strtab_shndx >= this->shnum())
    {
      this->error(_("invalid symbol table name index: %u"), strtab_shndx);
      return;
    }
  typename This::Shdr strtabshdr(pshdrs + strtab_shndx * This::shdr_size);
  if (strtabshdr.get_sh_type() != elfcpp::SHT_STRTAB)
    {
      this->error(_("symbol table name section has wrong type: %u"),
                  static_cast<unsigned int>(strtabshdr.get_sh_type()));
      return;
    }

  // Read the symbol names.
  File_view* fvstrtab = this->get_lasting_view(strtabshdr.get_sh_offset(),
                                               strtabshdr.get_sh_size(),
                                               false, true);

  sd->symbols = fvsymtab;
  sd->symbols_size = readsize;
  sd->external_symbols_offset = this->has_eh_frame_ ? locsize : 0;
  sd->symbol_names = fvstrtab;
  sd->symbol_names_size =
    convert_to_section_size_type(strtabshdr.get_sh_size());
}

// Return the section index of symbol SYM.  Set *VALUE to its value in
// the object file.  Set *IS_ORDINARY if this is an ordinary section
// index.  not a special cod between SHN_LORESERVE and SHN_HIRESERVE.
// Note that for a symbol which is not defined in this object file,
// this will set *VALUE to 0 and return SHN_UNDEF; it will not return
// the final value of the symbol in the link.

template<int size, bool big_endian>
unsigned int
Sized_relobj<size, big_endian>::symbol_section_and_value(unsigned int sym,
                                                         Address* value,
                                                         bool* is_ordinary)
{
  section_size_type symbols_size;
  const unsigned char* symbols = this->section_contents(this->symtab_shndx_,
                                                        &symbols_size,
                                                        false);

  const size_t count = symbols_size / This::sym_size;
  gold_assert(sym < count);

  elfcpp::Sym<size, big_endian> elfsym(symbols + sym * This::sym_size);
  *value = elfsym.get_st_value();

  return this->adjust_sym_shndx(sym, elfsym.get_st_shndx(), is_ordinary);
}

// Return whether to include a section group in the link.  LAYOUT is
// used to keep track of which section groups we have already seen.
// INDEX is the index of the section group and SHDR is the section
// header.  If we do not want to include this group, we set bits in
// OMIT for each section which should be discarded.

template<int size, bool big_endian>
bool
Sized_relobj<size, big_endian>::include_section_group(
    Symbol_table* symtab,
    Layout* layout,
    unsigned int index,
    const char* name,
    const unsigned char* shdrs,
    const char* section_names,
    section_size_type section_names_size,
    std::vector<bool>* omit)
{
  // Read the section contents.
  typename This::Shdr shdr(shdrs + index * This::shdr_size);
  const unsigned char* pcon = this->get_view(shdr.get_sh_offset(),
                                             shdr.get_sh_size(), true, false);
  const elfcpp::Elf_Word* pword =
    reinterpret_cast<const elfcpp::Elf_Word*>(pcon);

  // The first word contains flags.  We only care about COMDAT section
  // groups.  Other section groups are always included in the link
  // just like ordinary sections.
  elfcpp::Elf_Word flags = elfcpp::Swap<32, big_endian>::readval(pword);

  // Look up the group signature, which is the name of a symbol.  This
  // is a lot of effort to go to to read a string.  Why didn't they
  // just have the group signature point into the string table, rather
  // than indirect through a symbol?

  // Get the appropriate symbol table header (this will normally be
  // the single SHT_SYMTAB section, but in principle it need not be).
  const unsigned int link = this->adjust_shndx(shdr.get_sh_link());
  typename This::Shdr symshdr(this, this->elf_file_.section_header(link));

  // Read the symbol table entry.
  unsigned int symndx = shdr.get_sh_info();
  if (symndx >= symshdr.get_sh_size() / This::sym_size)
    {
      this->error(_("section group %u info %u out of range"),
                  index, symndx);
      return false;
    }
  off_t symoff = symshdr.get_sh_offset() + symndx * This::sym_size;
  const unsigned char* psym = this->get_view(symoff, This::sym_size, true,
                                             false);
  elfcpp::Sym<size, big_endian> sym(psym);

  // Read the symbol table names.
  section_size_type symnamelen;
  const unsigned char* psymnamesu;
  psymnamesu = this->section_contents(this->adjust_shndx(symshdr.get_sh_link()),
                                      &symnamelen, true);
  const char* psymnames = reinterpret_cast<const char*>(psymnamesu);

  // Get the section group signature.
  if (sym.get_st_name() >= symnamelen)
    {
      this->error(_("symbol %u name offset %u out of range"),
                  symndx, sym.get_st_name());
      return false;
    }

  std::string signature(psymnames + sym.get_st_name());

  // It seems that some versions of gas will create a section group
  // associated with a section symbol, and then fail to give a name to
  // the section symbol.  In such a case, use the name of the section.
  if (signature[0] == '\0' && sym.get_st_type() == elfcpp::STT_SECTION)
    {
      bool is_ordinary;
      unsigned int sym_shndx = this->adjust_sym_shndx(symndx,
                                                      sym.get_st_shndx(),
                                                      &is_ordinary);
      if (!is_ordinary || sym_shndx >= this->shnum())
        {
          this->error(_("symbol %u invalid section index %u"),
                      symndx, sym_shndx);
          return false;
        }
      typename This::Shdr member_shdr(shdrs + sym_shndx * This::shdr_size);
      if (member_shdr.get_sh_name() < section_names_size)
        signature = section_names + member_shdr.get_sh_name();
    }

  // Record this section group in the layout, and see whether we've already
  // seen one with the same signature.
  bool include_group = ((flags & elfcpp::GRP_COMDAT) == 0
                        || layout->add_comdat(this, index, signature, true));

  Sized_relobj<size, big_endian>* kept_object = NULL;
  Comdat_group* kept_group = NULL;

  if (!include_group)
    {
      // This group is being discarded.  Find the object and group
      // that was kept in its place.
      unsigned int kept_group_index = 0;
      Relobj* kept_relobj = layout->find_kept_object(signature,
                                                     &kept_group_index);
      kept_object = static_cast<Sized_relobj<size, big_endian>*>(kept_relobj);
      if (kept_object != NULL)
        kept_group = kept_object->find_comdat_group(kept_group_index);
    }
  else if (flags & elfcpp::GRP_COMDAT)
    {
      // This group is being kept.  Create the table to map section names
      // to section indexes and add it to the table of groups.
      kept_group = new Comdat_group();
      this->add_comdat_group(index, kept_group);
    }

  size_t count = shdr.get_sh_size() / sizeof(elfcpp::Elf_Word);

  std::vector<unsigned int> shndxes;
  bool relocate_group = include_group && parameters->options().relocatable();
  if (relocate_group)
    shndxes.reserve(count - 1);

  for (size_t i = 1; i < count; ++i)
    {
      elfcpp::Elf_Word secnum =
        this->adjust_shndx(elfcpp::Swap<32, big_endian>::readval(pword + i));

      if (relocate_group)
        shndxes.push_back(secnum);

      if (secnum >= this->shnum())
        {
          this->error(_("section %u in section group %u out of range"),
                      secnum, index);
          continue;
        }

      // Check for an earlier section number, since we're going to get
      // it wrong--we may have already decided to include the section.
      if (secnum < index)
        this->error(_("invalid section group %u refers to earlier section %u"),
                    index, secnum);

      // Get the name of the member section.
      typename This::Shdr member_shdr(shdrs + secnum * This::shdr_size);
      if (member_shdr.get_sh_name() >= section_names_size)
        {
          // This is an error, but it will be diagnosed eventually
          // in do_layout, so we don't need to do anything here but
          // ignore it.
          continue;
        }
      std::string mname(section_names + member_shdr.get_sh_name());

      if (!include_group)
        {
          (*omit)[secnum] = true;
          if (kept_group != NULL)
            {
              // Find the corresponding kept section, and store that info
              // in the discarded section table.
              Comdat_group::const_iterator p = kept_group->find(mname);
              if (p != kept_group->end())
                {
                  Kept_comdat_section* kept =
                    new Kept_comdat_section(kept_object, p->second);
                  this->set_kept_comdat_section(secnum, kept);
                }
            }
        }
      else if (flags & elfcpp::GRP_COMDAT)
        {
          // Add the section to the kept group table.
          gold_assert(kept_group != NULL);
          kept_group->insert(std::make_pair(mname, secnum));
        }
    }

  if (relocate_group)
    layout->layout_group(symtab, this, index, name, signature.c_str(),
                         shdr, flags, &shndxes);

  return include_group;
}

// Whether to include a linkonce section in the link.  NAME is the
// name of the section and SHDR is the section header.

// Linkonce sections are a GNU extension implemented in the original
// GNU linker before section groups were defined.  The semantics are
// that we only include one linkonce section with a given name.  The
// name of a linkonce section is normally .gnu.linkonce.T.SYMNAME,
// where T is the type of section and SYMNAME is the name of a symbol.
// In an attempt to make linkonce sections interact well with section
// groups, we try to identify SYMNAME and use it like a section group
// signature.  We want to block section groups with that signature,
// but not other linkonce sections with that signature.  We also use
// the full name of the linkonce section as a normal section group
// signature.

template<int size, bool big_endian>
bool
Sized_relobj<size, big_endian>::include_linkonce_section(
    Layout* layout,
    unsigned int index,
    const char* name,
    const elfcpp::Shdr<size, big_endian>&)
{
  // In general the symbol name we want will be the string following
  // the last '.'.  However, we have to handle the case of
  // .gnu.linkonce.t.__i686.get_pc_thunk.bx, which was generated by
  // some versions of gcc.  So we use a heuristic: if the name starts
  // with ".gnu.linkonce.t.", we use everything after that.  Otherwise
  // we look for the last '.'.  We can't always simply skip
  // ".gnu.linkonce.X", because we have to deal with cases like
  // ".gnu.linkonce.d.rel.ro.local".
  const char* const linkonce_t = ".gnu.linkonce.t.";
  const char* symname;
  if (strncmp(name, linkonce_t, strlen(linkonce_t)) == 0)
    symname = name + strlen(linkonce_t);
  else
    symname = strrchr(name, '.') + 1;
  std::string sig1(symname);
  std::string sig2(name);
  bool include1 = layout->add_comdat(this, index, sig1, false);
  bool include2 = layout->add_comdat(this, index, sig2, true);

  if (!include2)
    {
      // The section is being discarded on the basis of its section
      // name (i.e., the kept section was also a linkonce section).
      // In this case, the section index stored with the layout object
      // is the linkonce section that was kept.
      unsigned int kept_group_index = 0;
      Relobj* kept_relobj = layout->find_kept_object(sig2, &kept_group_index);
      if (kept_relobj != NULL)
        {
          Sized_relobj<size, big_endian>* kept_object
              = static_cast<Sized_relobj<size, big_endian>*>(kept_relobj);
          Kept_comdat_section* kept =
            new Kept_comdat_section(kept_object, kept_group_index);
          this->set_kept_comdat_section(index, kept);
        }
    }
  else if (!include1)
    {
      // The section is being discarded on the basis of its symbol
      // name.  This means that the corresponding kept section was
      // part of a comdat group, and it will be difficult to identify
      // the specific section within that group that corresponds to
      // this linkonce section.  We'll handle the simple case where
      // the group has only one member section.  Otherwise, it's not
      // worth the effort.
      unsigned int kept_group_index = 0;
      Relobj* kept_relobj = layout->find_kept_object(sig1, &kept_group_index);
      if (kept_relobj != NULL)
        {
          Sized_relobj<size, big_endian>* kept_object =
              static_cast<Sized_relobj<size, big_endian>*>(kept_relobj);
          Comdat_group* kept_group =
            kept_object->find_comdat_group(kept_group_index);
          if (kept_group != NULL && kept_group->size() == 1)
            {
              Comdat_group::const_iterator p = kept_group->begin();
              gold_assert(p != kept_group->end());
              Kept_comdat_section* kept =
                new Kept_comdat_section(kept_object, p->second);
              this->set_kept_comdat_section(index, kept);
            }
        }
    }

  return include1 && include2;
}

// Lay out the input sections.  We walk through the sections and check
// whether they should be included in the link.  If they should, we
// pass them to the Layout object, which will return an output section
// and an offset.

template<int size, bool big_endian>
void
Sized_relobj<size, big_endian>::do_layout(Symbol_table* symtab,
                                          Layout* layout,
                                          Read_symbols_data* sd)
{
  const unsigned int shnum = this->shnum();
  if (shnum == 0)
    return;

  // Get the section headers.
  const unsigned char* shdrs = sd->section_headers->data();
  const unsigned char* pshdrs;

  // Get the section names.
  const unsigned char* pnamesu = sd->section_names->data();
  const char* pnames = reinterpret_cast<const char*>(pnamesu);

  // For each section, record the index of the reloc section if any.
  // Use 0 to mean that there is no reloc section, -1U to mean that
  // there is more than one.
  std::vector<unsigned int> reloc_shndx(shnum, 0);
  std::vector<unsigned int> reloc_type(shnum, elfcpp::SHT_NULL);
  // Skip the first, dummy, section.
  pshdrs = shdrs + This::shdr_size;
  for (unsigned int i = 1; i < shnum; ++i, pshdrs += This::shdr_size)
    {
      typename This::Shdr shdr(pshdrs);

      unsigned int sh_type = shdr.get_sh_type();
      if (sh_type == elfcpp::SHT_REL || sh_type == elfcpp::SHT_RELA)
        {
          unsigned int target_shndx = this->adjust_shndx(shdr.get_sh_info());
          if (target_shndx == 0 || target_shndx >= shnum)
            {
              this->error(_("relocation section %u has bad info %u"),
                          i, target_shndx);
              continue;
            }

          if (reloc_shndx[target_shndx] != 0)
            reloc_shndx[target_shndx] = -1U;
          else
            {
              reloc_shndx[target_shndx] = i;
              reloc_type[target_shndx] = sh_type;
            }
        }
    }

  Output_sections& out_sections(this->output_sections());
  std::vector<Address>& out_section_offsets(this->section_offsets_);

  out_sections.resize(shnum);
  out_section_offsets.resize(shnum);

  // If we are only linking for symbols, then there is nothing else to
  // do here.
  if (this->input_file()->just_symbols())
    {
      delete sd->section_headers;
      sd->section_headers = NULL;
      delete sd->section_names;
      sd->section_names = NULL;
      return;
    }

  // Whether we've seen a .note.GNU-stack section.
  bool seen_gnu_stack = false;
  // The flags of a .note.GNU-stack section.
  uint64_t gnu_stack_flags = 0;

  // Keep track of which sections to omit.
  std::vector<bool> omit(shnum, false);

  // Keep track of reloc sections when emitting relocations.
  const bool relocatable = parameters->options().relocatable();
  const bool emit_relocs = (relocatable
                            || parameters->options().emit_relocs());
  std::vector<unsigned int> reloc_sections;

  // Keep track of .eh_frame sections.
  std::vector<unsigned int> eh_frame_sections;

  // Skip the first, dummy, section.
  pshdrs = shdrs + This::shdr_size;
  for (unsigned int i = 1; i < shnum; ++i, pshdrs += This::shdr_size)
    {
      typename This::Shdr shdr(pshdrs);

      if (shdr.get_sh_name() >= sd->section_names_size)
        {
          this->error(_("bad section name offset for section %u: %lu"),
                      i, static_cast<unsigned long>(shdr.get_sh_name()));
          return;
        }

      const char* name = pnames + shdr.get_sh_name();

      if (this->handle_gnu_warning_section(name, i, symtab))
        {
          if (!relocatable)
            omit[i] = true;
        }

      // The .note.GNU-stack section is special.  It gives the
      // protection flags that this object file requires for the stack
      // in memory.
      if (strcmp(name, ".note.GNU-stack") == 0)
        {
          seen_gnu_stack = true;
          gnu_stack_flags |= shdr.get_sh_flags();
          omit[i] = true;
        }

      bool discard = omit[i];
      if (!discard)
        {
          if (shdr.get_sh_type() == elfcpp::SHT_GROUP)
            {
              if (!this->include_section_group(symtab, layout, i, name, shdrs,
                                               pnames, sd->section_names_size,
                                               &omit))
                discard = true;
            }
          else if ((shdr.get_sh_flags() & elfcpp::SHF_GROUP) == 0
                   && Layout::is_linkonce(name))
            {
              if (!this->include_linkonce_section(layout, i, name, shdr))
                discard = true;
            }
        }

      if (discard)
        {
          // Do not include this section in the link.
          out_sections[i] = NULL;
          out_section_offsets[i] = -1U;
          continue;
        }

      // When doing a relocatable link we are going to copy input
      // reloc sections into the output.  We only want to copy the
      // ones associated with sections which are not being discarded.
      // However, we don't know that yet for all sections.  So save
      // reloc sections and process them later.
      if (emit_relocs
          && (shdr.get_sh_type() == elfcpp::SHT_REL
              || shdr.get_sh_type() == elfcpp::SHT_RELA))
        {
          reloc_sections.push_back(i);
          continue;
        }

      if (relocatable && shdr.get_sh_type() == elfcpp::SHT_GROUP)
        continue;

      // The .eh_frame section is special.  It holds exception frame
      // information that we need to read in order to generate the
      // exception frame header.  We process these after all the other
      // sections so that the exception frame reader can reliably
      // determine which sections are being discarded, and discard the
      // corresponding information.
      if (!relocatable
          && strcmp(name, ".eh_frame") == 0
          && this->check_eh_frame_flags(&shdr))
        {
          eh_frame_sections.push_back(i);
          continue;
        }

      off_t offset;
      Output_section* os = layout->layout(this, i, name, shdr,
                                          reloc_shndx[i], reloc_type[i],
                                          &offset);

      out_sections[i] = os;
      if (offset == -1)
        out_section_offsets[i] = -1U;
      else
        out_section_offsets[i] = convert_types<Address, off_t>(offset);

      // If this section requires special handling, and if there are
      // relocs that apply to it, then we must do the special handling
      // before we apply the relocs.
      if (offset == -1 && reloc_shndx[i] != 0)
        this->set_relocs_must_follow_section_writes();
    }

  layout->layout_gnu_stack(seen_gnu_stack, gnu_stack_flags);

  // When doing a relocatable link handle the reloc sections at the
  // end.
  if (emit_relocs)
    this->size_relocatable_relocs();
  for (std::vector<unsigned int>::const_iterator p = reloc_sections.begin();
       p != reloc_sections.end();
       ++p)
    {
      unsigned int i = *p;
      const unsigned char* pshdr;
      pshdr = sd->section_headers->data() + i * This::shdr_size;
      typename This::Shdr shdr(pshdr);

      unsigned int data_shndx = this->adjust_shndx(shdr.get_sh_info());
      if (data_shndx >= shnum)
        {
          // We already warned about this above.
          continue;
        }

      Output_section* data_section = out_sections[data_shndx];
      if (data_section == NULL)
        {
          out_sections[i] = NULL;
          out_section_offsets[i] = -1U;
          continue;
        }

      Relocatable_relocs* rr = new Relocatable_relocs();
      this->set_relocatable_relocs(i, rr);

      Output_section* os = layout->layout_reloc(this, i, shdr, data_section,
                                                rr);
      out_sections[i] = os;
      out_section_offsets[i] = -1U;
    }

  // Handle the .eh_frame sections at the end.
  for (std::vector<unsigned int>::const_iterator p = eh_frame_sections.begin();
       p != eh_frame_sections.end();
       ++p)
    {
      gold_assert(this->has_eh_frame_);
      gold_assert(sd->external_symbols_offset != 0);

      unsigned int i = *p;
      const unsigned char *pshdr;
      pshdr = sd->section_headers->data() + i * This::shdr_size;
      typename This::Shdr shdr(pshdr);

      off_t offset;
      Output_section* os = layout->layout_eh_frame(this,
                                                   sd->symbols->data(),
                                                   sd->symbols_size,
                                                   sd->symbol_names->data(),
                                                   sd->symbol_names_size,
                                                   i, shdr,
                                                   reloc_shndx[i],
                                                   reloc_type[i],
                                                   &offset);
      out_sections[i] = os;
      if (offset == -1)
        out_section_offsets[i] = -1U;
      else
        out_section_offsets[i] = convert_types<Address, off_t>(offset);

      // If this section requires special handling, and if there are
      // relocs that apply to it, then we must do the special handling
      // before we apply the relocs.
      if (offset == -1 && reloc_shndx[i] != 0)
        this->set_relocs_must_follow_section_writes();
    }

  delete sd->section_headers;
  sd->section_headers = NULL;
  delete sd->section_names;
  sd->section_names = NULL;
}

// Add the symbols to the symbol table.

template<int size, bool big_endian>
void
Sized_relobj<size, big_endian>::do_add_symbols(Symbol_table* symtab,
                                               Read_symbols_data* sd)
{
  if (sd->symbols == NULL)
    {
      gold_assert(sd->symbol_names == NULL);
      return;
    }

  const int sym_size = This::sym_size;
  size_t symcount = ((sd->symbols_size - sd->external_symbols_offset)
                     / sym_size);
  if (symcount * sym_size != sd->symbols_size - sd->external_symbols_offset)
    {
      this->error(_("size of symbols is not multiple of symbol size"));
      return;
    }

  this->symbols_.resize(symcount);

  const char* sym_names =
    reinterpret_cast<const char*>(sd->symbol_names->data());
  symtab->add_from_relobj(this,
                          sd->symbols->data() + sd->external_symbols_offset,
                          symcount, this->local_symbol_count_,
                          sym_names, sd->symbol_names_size,
                          &this->symbols_);

  delete sd->symbols;
  sd->symbols = NULL;
  delete sd->symbol_names;
  sd->symbol_names = NULL;
}

// First pass over the local symbols.  Here we add their names to
// *POOL and *DYNPOOL, and we store the symbol value in
// THIS->LOCAL_VALUES_.  This function is always called from a
// singleton thread.  This is followed by a call to
// finalize_local_symbols.

template<int size, bool big_endian>
void
Sized_relobj<size, big_endian>::do_count_local_symbols(Stringpool* pool,
                                                       Stringpool* dynpool)
{
  gold_assert(this->symtab_shndx_ != -1U);
  if (this->symtab_shndx_ == 0)
    {
      // This object has no symbols.  Weird but legal.
      return;
    }

  // Read the symbol table section header.
  const unsigned int symtab_shndx = this->symtab_shndx_;
  typename This::Shdr symtabshdr(this,
                                 this->elf_file_.section_header(symtab_shndx));
  gold_assert(symtabshdr.get_sh_type() == elfcpp::SHT_SYMTAB);

  // Read the local symbols.
  const int sym_size = This::sym_size;
  const unsigned int loccount = this->local_symbol_count_;
  gold_assert(loccount == symtabshdr.get_sh_info());
  off_t locsize = loccount * sym_size;
  const unsigned char* psyms = this->get_view(symtabshdr.get_sh_offset(),
                                              locsize, true, true);

  // Read the symbol names.
  const unsigned int strtab_shndx =
    this->adjust_shndx(symtabshdr.get_sh_link());
  section_size_type strtab_size;
  const unsigned char* pnamesu = this->section_contents(strtab_shndx,
                                                        &strtab_size,
                                                        true);
  const char* pnames = reinterpret_cast<const char*>(pnamesu);

  // Loop over the local symbols.

  const Output_sections& out_sections(this->output_sections());
  unsigned int shnum = this->shnum();
  unsigned int count = 0;
  unsigned int dyncount = 0;
  // Skip the first, dummy, symbol.
  psyms += sym_size;
  for (unsigned int i = 1; i < loccount; ++i, psyms += sym_size)
    {
      elfcpp::Sym<size, big_endian> sym(psyms);

      Symbol_value<size>& lv(this->local_values_[i]);

      bool is_ordinary;
      unsigned int shndx = this->adjust_sym_shndx(i, sym.get_st_shndx(),
                                                  &is_ordinary);
      lv.set_input_shndx(shndx, is_ordinary);

      if (sym.get_st_type() == elfcpp::STT_SECTION)
        lv.set_is_section_symbol();
      else if (sym.get_st_type() == elfcpp::STT_TLS)
        lv.set_is_tls_symbol();

      // Save the input symbol value for use in do_finalize_local_symbols().
      lv.set_input_value(sym.get_st_value());

      // Decide whether this symbol should go into the output file.

      if (shndx < shnum && out_sections[shndx] == NULL)
        {
          lv.set_no_output_symtab_entry();
          gold_assert(!lv.needs_output_dynsym_entry());
          continue;
        }

      if (sym.get_st_type() == elfcpp::STT_SECTION)
        {
          lv.set_no_output_symtab_entry();
          gold_assert(!lv.needs_output_dynsym_entry());
          continue;
        }

      if (sym.get_st_name() >= strtab_size)
        {
          this->error(_("local symbol %u section name out of range: %u >= %u"),
                      i, sym.get_st_name(),
                      static_cast<unsigned int>(strtab_size));
          lv.set_no_output_symtab_entry();
          continue;
        }

      // Add the symbol to the symbol table string pool.
      const char* name = pnames + sym.get_st_name();
      pool->add(name, true, NULL);
      ++count;

      // If needed, add the symbol to the dynamic symbol table string pool.
      if (lv.needs_output_dynsym_entry())
        {
          dynpool->add(name, true, NULL);
          ++dyncount;
        }
    }

  this->output_local_symbol_count_ = count;
  this->output_local_dynsym_count_ = dyncount;
}

// Finalize the local symbols.  Here we set the final value in
// THIS->LOCAL_VALUES_ and set their output symbol table indexes.
// This function is always called from a singleton thread.  The actual
// output of the local symbols will occur in a separate task.

template<int size, bool big_endian>
unsigned int
Sized_relobj<size, big_endian>::do_finalize_local_symbols(unsigned int index,
                                                          off_t off)
{
  gold_assert(off == static_cast<off_t>(align_address(off, size >> 3)));

  const unsigned int loccount = this->local_symbol_count_;
  this->local_symbol_offset_ = off;

  const Output_sections& out_sections(this->output_sections());
  const std::vector<Address>& out_offsets(this->section_offsets_);
  unsigned int shnum = this->shnum();

  for (unsigned int i = 1; i < loccount; ++i)
    {
      Symbol_value<size>& lv(this->local_values_[i]);

      bool is_ordinary;
      unsigned int shndx = lv.input_shndx(&is_ordinary);

      // Set the output symbol value.

      if (!is_ordinary)
        {
          if (shndx == elfcpp::SHN_ABS || shndx == elfcpp::SHN_COMMON)
            lv.set_output_value(lv.input_value());
          else
            {
              this->error(_("unknown section index %u for local symbol %u"),
                          shndx, i);
              lv.set_output_value(0);
            }
        }
      else
        {
          if (shndx >= shnum)
            {
              this->error(_("local symbol %u section index %u out of range"),
                          i, shndx);
              shndx = 0;
            }

          Output_section* os = out_sections[shndx];

          if (os == NULL)
            {
              // This local symbol belongs to a section we are discarding.
              // In some cases when applying relocations later, we will
              // attempt to match it to the corresponding kept section,
              // so we leave the input value unchanged here.
              continue;
            }
          else if (out_offsets[shndx] == -1U)
            {
              // This is a SHF_MERGE section or one which otherwise
              // requires special handling.  We get the output address
              // of the start of the merged section.  If this is not a
              // section symbol, we can then determine the final
              // value.  If it is a section symbol, we can not, as in
              // that case we have to consider the addend to determine
              // the value to use in a relocation.
              if (!lv.is_section_symbol())
                lv.set_output_value(os->output_address(this, shndx,
                                                       lv.input_value()));
              else
                {
                  section_offset_type start =
                    os->starting_output_address(this, shndx);
                  Merged_symbol_value<size>* msv =
                    new Merged_symbol_value<size>(lv.input_value(), start);
                  lv.set_merged_symbol_value(msv);
                }
            }
          else if (lv.is_tls_symbol())
            lv.set_output_value(os->tls_offset()
                                + out_offsets[shndx]
                                + lv.input_value());
          else
            lv.set_output_value(os->address()
                                + out_offsets[shndx]
                                + lv.input_value());
        }

      if (lv.needs_output_symtab_entry())
        {
          lv.set_output_symtab_index(index);
          ++index;
        }
    }
  return index;
}

// Set the output dynamic symbol table indexes for the local variables.

template<int size, bool big_endian>
unsigned int
Sized_relobj<size, big_endian>::do_set_local_dynsym_indexes(unsigned int index)
{
  const unsigned int loccount = this->local_symbol_count_;
  for (unsigned int i = 1; i < loccount; ++i)
    {
      Symbol_value<size>& lv(this->local_values_[i]);
      if (lv.needs_output_dynsym_entry())
        {
          lv.set_output_dynsym_index(index);
          ++index;
        }
    }
  return index;
}

// Set the offset where local dynamic symbol information will be stored.
// Returns the count of local symbols contributed to the symbol table by
// this object.

template<int size, bool big_endian>
unsigned int
Sized_relobj<size, big_endian>::do_set_local_dynsym_offset(off_t off)
{
  gold_assert(off == static_cast<off_t>(align_address(off, size >> 3)));
  this->local_dynsym_offset_ = off;
  return this->output_local_dynsym_count_;
}

// Write out the local symbols.

template<int size, bool big_endian>
void
Sized_relobj<size, big_endian>::write_local_symbols(
    Output_file* of,
    const Stringpool* sympool,
    const Stringpool* dynpool,
    Output_symtab_xindex* symtab_xindex,
    Output_symtab_xindex* dynsym_xindex)
{
  if (parameters->options().strip_all()
      && this->output_local_dynsym_count_ == 0)
    return;

  gold_assert(this->symtab_shndx_ != -1U);
  if (this->symtab_shndx_ == 0)
    {
      // This object has no symbols.  Weird but legal.
      return;
    }

  // Read the symbol table section header.
  const unsigned int symtab_shndx = this->symtab_shndx_;
  typename This::Shdr symtabshdr(this,
                                 this->elf_file_.section_header(symtab_shndx));
  gold_assert(symtabshdr.get_sh_type() == elfcpp::SHT_SYMTAB);
  const unsigned int loccount = this->local_symbol_count_;
  gold_assert(loccount == symtabshdr.get_sh_info());

  // Read the local symbols.
  const int sym_size = This::sym_size;
  off_t locsize = loccount * sym_size;
  const unsigned char* psyms = this->get_view(symtabshdr.get_sh_offset(),
                                              locsize, true, false);

  // Read the symbol names.
  const unsigned int strtab_shndx =
    this->adjust_shndx(symtabshdr.get_sh_link());
  section_size_type strtab_size;
  const unsigned char* pnamesu = this->section_contents(strtab_shndx,
                                                        &strtab_size,
                                                        false);
  const char* pnames = reinterpret_cast<const char*>(pnamesu);

  // Get views into the output file for the portions of the symbol table
  // and the dynamic symbol table that we will be writing.
  off_t output_size = this->output_local_symbol_count_ * sym_size;
  unsigned char* oview = NULL;
  if (output_size > 0)
    oview = of->get_output_view(this->local_symbol_offset_, output_size);

  off_t dyn_output_size = this->output_local_dynsym_count_ * sym_size;
  unsigned char* dyn_oview = NULL;
  if (dyn_output_size > 0)
    dyn_oview = of->get_output_view(this->local_dynsym_offset_,
                                    dyn_output_size);

  const Output_sections out_sections(this->output_sections());

  gold_assert(this->local_values_.size() == loccount);

  unsigned char* ov = oview;
  unsigned char* dyn_ov = dyn_oview;
  psyms += sym_size;
  for (unsigned int i = 1; i < loccount; ++i, psyms += sym_size)
    {
      elfcpp::Sym<size, big_endian> isym(psyms);

      Symbol_value<size>& lv(this->local_values_[i]);

      bool is_ordinary;
      unsigned int st_shndx = this->adjust_sym_shndx(i, isym.get_st_shndx(),
                                                     &is_ordinary);
      if (is_ordinary)
        {
          gold_assert(st_shndx < out_sections.size());
          if (out_sections[st_shndx] == NULL)
            continue;
          st_shndx = out_sections[st_shndx]->out_shndx();
          if (st_shndx >= elfcpp::SHN_LORESERVE)
            {
              if (lv.needs_output_symtab_entry())
                symtab_xindex->add(lv.output_symtab_index(), st_shndx);
              if (lv.needs_output_dynsym_entry())
                dynsym_xindex->add(lv.output_dynsym_index(), st_shndx);
              st_shndx = elfcpp::SHN_XINDEX;
            }
        }

      // Write the symbol to the output symbol table.
      if (!parameters->options().strip_all()
          && lv.needs_output_symtab_entry())
        {
          elfcpp::Sym_write<size, big_endian> osym(ov);

          gold_assert(isym.get_st_name() < strtab_size);
          const char* name = pnames + isym.get_st_name();
          osym.put_st_name(sympool->get_offset(name));
          osym.put_st_value(this->local_values_[i].value(this, 0));
          osym.put_st_size(isym.get_st_size());
          osym.put_st_info(isym.get_st_info());
          osym.put_st_other(isym.get_st_other());
          osym.put_st_shndx(st_shndx);

          ov += sym_size;
        }

      // Write the symbol to the output dynamic symbol table.
      if (lv.needs_output_dynsym_entry())
        {
          gold_assert(dyn_ov < dyn_oview + dyn_output_size);
          elfcpp::Sym_write<size, big_endian> osym(dyn_ov);

          gold_assert(isym.get_st_name() < strtab_size);
          const char* name = pnames + isym.get_st_name();
          osym.put_st_name(dynpool->get_offset(name));
          osym.put_st_value(this->local_values_[i].value(this, 0));
          osym.put_st_size(isym.get_st_size());
          osym.put_st_info(isym.get_st_info());
          osym.put_st_other(isym.get_st_other());
          osym.put_st_shndx(st_shndx);

          dyn_ov += sym_size;
        }
    }


  if (output_size > 0)
    {
      gold_assert(ov - oview == output_size);
      of->write_output_view(this->local_symbol_offset_, output_size, oview);
    }

  if (dyn_output_size > 0)
    {
      gold_assert(dyn_ov - dyn_oview == dyn_output_size);
      of->write_output_view(this->local_dynsym_offset_, dyn_output_size,
                            dyn_oview);
    }
}

// Set *INFO to symbolic information about the offset OFFSET in the
// section SHNDX.  Return true if we found something, false if we
// found nothing.

template<int size, bool big_endian>
bool
Sized_relobj<size, big_endian>::get_symbol_location_info(
    unsigned int shndx,
    off_t offset,
    Symbol_location_info* info)
{
  if (this->symtab_shndx_ == 0)
    return false;

  section_size_type symbols_size;
  const unsigned char* symbols = this->section_contents(this->symtab_shndx_,
                                                        &symbols_size,
                                                        false);

  unsigned int symbol_names_shndx =
    this->adjust_shndx(this->section_link(this->symtab_shndx_));
  section_size_type names_size;
  const unsigned char* symbol_names_u =
    this->section_contents(symbol_names_shndx, &names_size, false);
  const char* symbol_names = reinterpret_cast<const char*>(symbol_names_u);

  const int sym_size = This::sym_size;
  const size_t count = symbols_size / sym_size;

  const unsigned char* p = symbols;
  for (size_t i = 0; i < count; ++i, p += sym_size)
    {
      elfcpp::Sym<size, big_endian> sym(p);

      if (sym.get_st_type() == elfcpp::STT_FILE)
        {
          if (sym.get_st_name() >= names_size)
            info->source_file = "(invalid)";
          else
            info->source_file = symbol_names + sym.get_st_name();
          continue;
        }

      bool is_ordinary;
      unsigned int st_shndx = this->adjust_sym_shndx(i, sym.get_st_shndx(),
                                                     &is_ordinary);
      if (is_ordinary
          && st_shndx == shndx
          && static_cast<off_t>(sym.get_st_value()) <= offset
          && (static_cast<off_t>(sym.get_st_value() + sym.get_st_size())
              > offset))
        {
          if (sym.get_st_name() > names_size)
            info->enclosing_symbol_name = "(invalid)";
          else
            {
              info->enclosing_symbol_name = symbol_names + sym.get_st_name();
              if (parameters->options().do_demangle())
                {
                  char* demangled_name = cplus_demangle(
                      info->enclosing_symbol_name.c_str(),
                      DMGL_ANSI | DMGL_PARAMS);
                  if (demangled_name != NULL)
                    {
                      info->enclosing_symbol_name.assign(demangled_name);
                      free(demangled_name);
                    }
                }
            }
          return true;
        }
    }

  return false;
}

// Look for a kept section corresponding to the given discarded section,
// and return its output address.  This is used only for relocations in
// debugging sections.  If we can't find the kept section, return 0.

template<int size, bool big_endian>
typename Sized_relobj<size, big_endian>::Address
Sized_relobj<size, big_endian>::map_to_kept_section(
    unsigned int shndx,
    bool* found) const
{
  Kept_comdat_section *kept = this->get_kept_comdat_section(shndx);
  if (kept != NULL)
    {
      gold_assert(kept->object_ != NULL);
      *found = true;
      Output_section* os = kept->object_->output_section(kept->shndx_);
      Address offset = kept->object_->get_output_section_offset(kept->shndx_);
      gold_assert(os != NULL && offset != -1U);
      return os->address() + offset;
    }
  *found = false;
  return 0;
}

// Input_objects methods.

// Add a regular relocatable object to the list.  Return false if this
// object should be ignored.

bool
Input_objects::add_object(Object* obj)
{
  // Set the global target from the first object file we recognize.
  Target* target = obj->target();
  if (!parameters->target_valid())
    set_parameters_target(target);
  else if (target != &parameters->target())
    {
      obj->error(_("incompatible target"));
      return false;
    }

  // Print the filename if the -t/--trace option is selected.
  if (parameters->options().trace())
    gold_info("%s", obj->name().c_str());

  if (!obj->is_dynamic())
    this->relobj_list_.push_back(static_cast<Relobj*>(obj));
  else
    {
      // See if this is a duplicate SONAME.
      Dynobj* dynobj = static_cast<Dynobj*>(obj);
      const char* soname = dynobj->soname();

      std::pair<Unordered_set<std::string>::iterator, bool> ins =
        this->sonames_.insert(soname);
      if (!ins.second)
        {
          // We have already seen a dynamic object with this soname.
          return false;
        }

      this->dynobj_list_.push_back(dynobj);

      // If this is -lc, remember the directory in which we found it.
      // We use this when issuing warnings about undefined symbols: as
      // a heuristic, we don't warn about system libraries found in
      // the same directory as -lc.
      if (strncmp(soname, "libc.so", 7) == 0)
        {
          const char* object_name = dynobj->name().c_str();
          const char* base = lbasename(object_name);
          if (base != object_name)
            this->system_library_directory_.assign(object_name,
                                                   base - 1 - object_name);
        }
    }

  return true;
}

// Return whether an object was found in the system library directory.

bool
Input_objects::found_in_system_library_directory(const Object* object) const
{
  return (!this->system_library_directory_.empty()
          && object->name().compare(0,
                                    this->system_library_directory_.size(),
                                    this->system_library_directory_) == 0);
}

// For each dynamic object, record whether we've seen all of its
// explicit dependencies.

void
Input_objects::check_dynamic_dependencies() const
{
  for (Dynobj_list::const_iterator p = this->dynobj_list_.begin();
       p != this->dynobj_list_.end();
       ++p)
    {
      const Dynobj::Needed& needed((*p)->needed());
      bool found_all = true;
      for (Dynobj::Needed::const_iterator pneeded = needed.begin();
           pneeded != needed.end();
           ++pneeded)
        {
          if (this->sonames_.find(*pneeded) == this->sonames_.end())
            {
              found_all = false;
              break;
            }
        }
      (*p)->set_has_unknown_needed_entries(!found_all);
    }
}

// Relocate_info methods.

// Return a string describing the location of a relocation.  This is
// only used in error messages.

template<int size, bool big_endian>
std::string
Relocate_info<size, big_endian>::location(size_t, off_t offset) const
{
  // See if we can get line-number information from debugging sections.
  std::string filename;
  std::string file_and_lineno;   // Better than filename-only, if available.

  Sized_dwarf_line_info<size, big_endian> line_info(this->object);
  // This will be "" if we failed to parse the debug info for any reason.
  file_and_lineno = line_info.addr2line(this->data_shndx, offset);

  std::string ret(this->object->name());
  ret += ':';
  Symbol_location_info info;
  if (this->object->get_symbol_location_info(this->data_shndx, offset, &info))
    {
      ret += " in function ";
      ret += info.enclosing_symbol_name;
      ret += ":";
      filename = info.source_file;
    }

  if (!file_and_lineno.empty())
    ret += file_and_lineno;
  else
    {
      if (!filename.empty())
        ret += filename;
      ret += "(";
      ret += this->object->section_name(this->data_shndx);
      char buf[100];
      // Offsets into sections have to be positive.
      snprintf(buf, sizeof(buf), "+0x%lx", static_cast<long>(offset));
      ret += buf;
      ret += ")";
    }
  return ret;
}

} // End namespace gold.

namespace
{

using namespace gold;

// Read an ELF file with the header and return the appropriate
// instance of Object.

template<int size, bool big_endian>
Object*
make_elf_sized_object(const std::string& name, Input_file* input_file,
                      off_t offset, const elfcpp::Ehdr<size, big_endian>& ehdr)
{
  int et = ehdr.get_e_type();
  if (et == elfcpp::ET_REL)
    {
      Sized_relobj<size, big_endian>* obj =
        new Sized_relobj<size, big_endian>(name, input_file, offset, ehdr);
      obj->setup(ehdr);
      return obj;
    }
  else if (et == elfcpp::ET_DYN)
    {
      Sized_dynobj<size, big_endian>* obj =
        new Sized_dynobj<size, big_endian>(name, input_file, offset, ehdr);
      obj->setup(ehdr);
      return obj;
    }
  else
    {
      gold_error(_("%s: unsupported ELF file type %d"),
                 name.c_str(), et);
      return NULL;
    }
}

} // End anonymous namespace.

namespace gold
{

// Read an ELF file and return the appropriate instance of Object.

Object*
make_elf_object(const std::string& name, Input_file* input_file, off_t offset,
                const unsigned char* p, section_offset_type bytes)
{
  if (bytes < elfcpp::EI_NIDENT)
    {
      gold_error(_("%s: ELF file too short"), name.c_str());
      return NULL;
    }

  int v = p[elfcpp::EI_VERSION];
  if (v != elfcpp::EV_CURRENT)
    {
      if (v == elfcpp::EV_NONE)
        gold_error(_("%s: invalid ELF version 0"), name.c_str());
      else
        gold_error(_("%s: unsupported ELF version %d"), name.c_str(), v);
      return NULL;
    }

  int c = p[elfcpp::EI_CLASS];
  if (c == elfcpp::ELFCLASSNONE)
    {
      gold_error(_("%s: invalid ELF class 0"), name.c_str());
      return NULL;
    }
  else if (c != elfcpp::ELFCLASS32
           && c != elfcpp::ELFCLASS64)
    {
      gold_error(_("%s: unsupported ELF class %d"), name.c_str(), c);
      return NULL;
    }

  int d = p[elfcpp::EI_DATA];
  if (d == elfcpp::ELFDATANONE)
    {
      gold_error(_("%s: invalid ELF data encoding"), name.c_str());
      return NULL;
    }
  else if (d != elfcpp::ELFDATA2LSB
           && d != elfcpp::ELFDATA2MSB)
    {
      gold_error(_("%s: unsupported ELF data encoding %d"), name.c_str(), d);
      return NULL;
    }

  bool big_endian = d == elfcpp::ELFDATA2MSB;

  if (c == elfcpp::ELFCLASS32)
    {
      if (bytes < elfcpp::Elf_sizes<32>::ehdr_size)
        {
          gold_error(_("%s: ELF file too short"), name.c_str());
          return NULL;
        }
      if (big_endian)
        {
#ifdef HAVE_TARGET_32_BIG
          elfcpp::Ehdr<32, true> ehdr(p);
          return make_elf_sized_object<32, true>(name, input_file,
                                                 offset, ehdr);
#else
          gold_error(_("%s: not configured to support "
                       "32-bit big-endian object"),
                     name.c_str());
          return NULL;
#endif
        }
      else
        {
#ifdef HAVE_TARGET_32_LITTLE
          elfcpp::Ehdr<32, false> ehdr(p);
          return make_elf_sized_object<32, false>(name, input_file,
                                                  offset, ehdr);
#else
          gold_error(_("%s: not configured to support "
                       "32-bit little-endian object"),
                     name.c_str());
          return NULL;
#endif
        }
    }
  else
    {
      if (bytes < elfcpp::Elf_sizes<64>::ehdr_size)
        {
          gold_error(_("%s: ELF file too short"), name.c_str());
          return NULL;
        }
      if (big_endian)
        {
#ifdef HAVE_TARGET_64_BIG
          elfcpp::Ehdr<64, true> ehdr(p);
          return make_elf_sized_object<64, true>(name, input_file,
                                                 offset, ehdr);
#else
          gold_error(_("%s: not configured to support "
                       "64-bit big-endian object"),
                     name.c_str());
          return NULL;
#endif
        }
      else
        {
#ifdef HAVE_TARGET_64_LITTLE
          elfcpp::Ehdr<64, false> ehdr(p);
          return make_elf_sized_object<64, false>(name, input_file,
                                                  offset, ehdr);
#else
          gold_error(_("%s: not configured to support "
                       "64-bit little-endian object"),
                     name.c_str());
          return NULL;
#endif
        }
    }
}

// Instantiate the templates we need.

#ifdef HAVE_TARGET_32_LITTLE
template
void
Object::read_section_data<32, false>(elfcpp::Elf_file<32, false, Object>*,
                                     Read_symbols_data*);
#endif

#ifdef HAVE_TARGET_32_BIG
template
void
Object::read_section_data<32, true>(elfcpp::Elf_file<32, true, Object>*,
                                    Read_symbols_data*);
#endif

#ifdef HAVE_TARGET_64_LITTLE
template
void
Object::read_section_data<64, false>(elfcpp::Elf_file<64, false, Object>*,
                                     Read_symbols_data*);
#endif

#ifdef HAVE_TARGET_64_BIG
template
void
Object::read_section_data<64, true>(elfcpp::Elf_file<64, true, Object>*,
                                    Read_symbols_data*);
#endif

#ifdef HAVE_TARGET_32_LITTLE
template
class Sized_relobj<32, false>;
#endif

#ifdef HAVE_TARGET_32_BIG
template
class Sized_relobj<32, true>;
#endif

#ifdef HAVE_TARGET_64_LITTLE
template
class Sized_relobj<64, false>;
#endif

#ifdef HAVE_TARGET_64_BIG
template
class Sized_relobj<64, true>;
#endif

#ifdef HAVE_TARGET_32_LITTLE
template
struct Relocate_info<32, false>;
#endif

#ifdef HAVE_TARGET_32_BIG
template
struct Relocate_info<32, true>;
#endif

#ifdef HAVE_TARGET_64_LITTLE
template
struct Relocate_info<64, false>;
#endif

#ifdef HAVE_TARGET_64_BIG
template
struct Relocate_info<64, true>;
#endif

} // End namespace gold.