/* linker.c -- BFD linker routines

   Copyright (C) 1993-2023 Free Software Foundation, Inc.

   Written by Steve Chamberlain and Ian Lance Taylor, Cygnus Support

   This file is part of BFD, the Binary File Descriptor library.

   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 "sysdep.h"

#include "bfd.h"

#include "libbfd.h"

#include "bfdlink.h"

#include "genlink.h"

/*

SECTION

  Linker Functions

@cindex Linker

  The linker uses three special entry points in the BFD target

  vector.  It is not necessary to write special routines for

  these entry points when creating a new BFD back end, since

  generic versions are provided.  However, writing them can

  speed up linking and make it use significantly less runtime

  memory.

  The first routine creates a hash table used by the other

  routines.  The second routine adds the symbols from an object

  file to the hash table.  The third routine takes all the

  object files and links them together to create the output

  file.  These routines are designed so that the linker proper

  does not need to know anything about the symbols in the object

  files that it is linking.  The linker merely arranges the

  sections as directed by the linker script and lets BFD handle

  the details of symbols and relocs.

  The second routine and third routines are passed a pointer to

  a <<struct bfd_link_info>> structure (defined in

  <<bfdlink.h>>) which holds information relevant to the link,

  including the linker hash table (which was created by the

  first routine) and a set of callback functions to the linker

  proper.

  The generic linker routines are in <<linker.c>>, and use the

  header file <<genlink.h>>.  As of this writing, the only back

  ends which have implemented versions of these routines are

  a.out (in <<aoutx.h>>) and ECOFF (in <<ecoff.c>>).  The a.out

  routines are used as examples throughout this section.

@menu

@* Creating a Linker Hash Table::

@* Adding Symbols to the Hash Table::

@* Performing the Final Link::

@end menu

INODE

Creating a Linker Hash Table, Adding Symbols to the Hash Table, Linker Functions, Linker Functions

SUBSECTION

  Creating a linker hash table

@cindex _bfd_link_hash_table_create in target vector

@cindex target vector (_bfd_link_hash_table_create)

  The linker routines must create a hash table, which must be

  derived from <<struct bfd_link_hash_table>> described in

  <<bfdlink.c>>.  @xref{Hash Tables}, for information on how to

  create a derived hash table.  This entry point is called using

  the target vector of the linker output file.

  The <<_bfd_link_hash_table_create>> entry point must allocate

  and initialize an instance of the desired hash table.  If the

  back end does not require any additional information to be

  stored with the entries in the hash table, the entry point may

  simply create a <<struct bfd_link_hash_table>>.  Most likely,

  however, some additional information will be needed.

  For example, with each entry in the hash table the a.out

  linker keeps the index the symbol has in the final output file

  (this index number is used so that when doing a relocatable

  link the symbol index used in the output file can be quickly

  filled in when copying over a reloc).  The a.out linker code

  defines the required structures and functions for a hash table

  derived from <<struct bfd_link_hash_table>>.  The a.out linker

  hash table is created by the function

  <<NAME(aout,link_hash_table_create)>>; it simply allocates

  space for the hash table, initializes it, and returns a

  pointer to it.

  When writing the linker routines for a new back end, you will

  generally not know exactly which fields will be required until

  you have finished.  You should simply create a new hash table

  which defines no additional fields, and then simply add fields

  as they become necessary.

INODE

Adding Symbols to the Hash Table, Performing the Final Link, Creating a Linker Hash Table, Linker Functions

SUBSECTION

  Adding symbols to the hash table

@cindex _bfd_link_add_symbols in target vector

@cindex target vector (_bfd_link_add_symbols)

  The linker proper will call the <<_bfd_link_add_symbols>>

  entry point for each object file or archive which is to be

  linked (typically these are the files named on the command

  line, but some may also come from the linker script).  The

  entry point is responsible for examining the file.  For an

  object file, BFD must add any relevant symbol information to

  the hash table.  For an archive, BFD must determine which

  elements of the archive should be used and adding them to the

  link.

  The a.out version of this entry point is

  <<NAME(aout,link_add_symbols)>>.

@menu

@* Differing file formats::

@* Adding symbols from an object file::

@* Adding symbols from an archive::

@end menu

INODE

Differing file formats, Adding symbols from an object file, Adding Symbols to the Hash Table, Adding Symbols to the Hash Table

SUBSUBSECTION

  Differing file formats

  Normally all the files involved in a link will be of the same

  format, but it is also possible to link together different

  format object files, and the back end must support that.  The

  <<_bfd_link_add_symbols>> entry point is called via the target

  vector of the file to be added.  This has an important

  consequence: the function may not assume that the hash table

  is the type created by the corresponding

  <<_bfd_link_hash_table_create>> vector.  All the

  <<_bfd_link_add_symbols>> function can assume about the hash

  table is that it is derived from <<struct

  bfd_link_hash_table>>.

  Sometimes the <<_bfd_link_add_symbols>> function must store

  some information in the hash table entry to be used by the

  <<_bfd_final_link>> function.  In such a case the output bfd

  xvec must be checked to make sure that the hash table was

  created by an object file of the same format.

  The <<_bfd_final_link>> routine must be prepared to handle a

  hash entry without any extra information added by the

  <<_bfd_link_add_symbols>> function.  A hash entry without

  extra information will also occur when the linker script

  directs the linker to create a symbol.  Note that, regardless

  of how a hash table entry is added, all the fields will be

  initialized to some sort of null value by the hash table entry

  initialization function.

  See <<ecoff_link_add_externals>> for an example of how to

  check the output bfd before saving information (in this

  case, the ECOFF external symbol debugging information) in a

  hash table entry.

INODE

Adding symbols from an object file, Adding symbols from an archive, Differing file formats, Adding Symbols to the Hash Table

SUBSUBSECTION

  Adding symbols from an object file

  When the <<_bfd_link_add_symbols>> routine is passed an object

  file, it must add all externally visible symbols in that

  object file to the hash table.  The actual work of adding the

  symbol to the hash table is normally handled by the function

  <<_bfd_generic_link_add_one_symbol>>.  The

  <<_bfd_link_add_symbols>> routine is responsible for reading

  all the symbols from the object file and passing the correct

  information to <<_bfd_generic_link_add_one_symbol>>.

  The <<_bfd_link_add_symbols>> routine should not use

  <<bfd_canonicalize_symtab>> to read the symbols.  The point of

  providing this routine is to avoid the overhead of converting

  the symbols into generic <<asymbol>> structures.

@findex _bfd_generic_link_add_one_symbol

  <<_bfd_generic_link_add_one_symbol>> handles the details of

  combining common symbols, warning about multiple definitions,

  and so forth.  It takes arguments which describe the symbol to

  add, notably symbol flags, a section, and an offset.  The

  symbol flags include such things as <<BSF_WEAK>> or

  <<BSF_INDIRECT>>.  The section is a section in the object

  file, or something like <<bfd_und_section_ptr>> for an undefined

  symbol or <<bfd_com_section_ptr>> for a common symbol.

  If the <<_bfd_final_link>> routine is also going to need to

  read the symbol information, the <<_bfd_link_add_symbols>>

  routine should save it somewhere attached to the object file

  BFD.  However, the information should only be saved if the

  <<keep_memory>> field of the <<info>> argument is TRUE, so

  that the <<-no-keep-memory>> linker switch is effective.

  The a.out function which adds symbols from an object file is

  <<aout_link_add_object_symbols>>, and most of the interesting

  work is in <<aout_link_add_symbols>>.  The latter saves

  pointers to the hash tables entries created by

  <<_bfd_generic_link_add_one_symbol>> indexed by symbol number,

  so that the <<_bfd_final_link>> routine does not have to call

  the hash table lookup routine to locate the entry.

INODE

Adding symbols from an archive, , Adding symbols from an object file, Adding Symbols to the Hash Table

SUBSUBSECTION

  Adding symbols from an archive

  When the <<_bfd_link_add_symbols>> routine is passed an

  archive, it must look through the symbols defined by the

  archive and decide which elements of the archive should be

  included in the link.  For each such element it must call the

  <<add_archive_element>> linker callback, and it must add the

  symbols from the object file to the linker hash table.  (The

  callback may in fact indicate that a replacement BFD should be

  used, in which case the symbols from that BFD should be added

  to the linker hash table instead.)

@findex _bfd_generic_link_add_archive_symbols

  In most cases the work of looking through the symbols in the

  archive should be done by the

  <<_bfd_generic_link_add_archive_symbols>> function.

  <<_bfd_generic_link_add_archive_symbols>> is passed a function

  to call to make the final decision about adding an archive

  element to the link and to do the actual work of adding the

  symbols to the linker hash table.  If the element is to

  be included, the <<add_archive_element>> linker callback

  routine must be called with the element as an argument, and

  the element's symbols must be added to the linker hash table

  just as though the element had itself been passed to the

  <<_bfd_link_add_symbols>> function.

  When the a.out <<_bfd_link_add_symbols>> function receives an

  archive, it calls <<_bfd_generic_link_add_archive_symbols>>

  passing <<aout_link_check_archive_element>> as the function

  argument. <<aout_link_check_archive_element>> calls

  <<aout_link_check_ar_symbols>>.  If the latter decides to add

  the element (an element is only added if it provides a real,

  non-common, definition for a previously undefined or common

  symbol) it calls the <<add_archive_element>> callback and then

  <<aout_link_check_archive_element>> calls

  <<aout_link_add_symbols>> to actually add the symbols to the

  linker hash table - possibly those of a substitute BFD, if the

  <<add_archive_element>> callback avails itself of that option.

  The ECOFF back end is unusual in that it does not normally

  call <<_bfd_generic_link_add_archive_symbols>>, because ECOFF

  archives already contain a hash table of symbols.  The ECOFF

  back end searches the archive itself to avoid the overhead of

  creating a new hash table.

INODE

Performing the Final Link, , Adding Symbols to the Hash Table, Linker Functions

SUBSECTION

  Performing the final link

@cindex _bfd_link_final_link in target vector

@cindex target vector (_bfd_final_link)

  When all the input files have been processed, the linker calls

  the <<_bfd_final_link>> entry point of the output BFD.  This

  routine is responsible for producing the final output file,

  which has several aspects.  It must relocate the contents of

  the input sections and copy the data into the output sections.

  It must build an output symbol table including any local

  symbols from the input files and the global symbols from the

  hash table.  When producing relocatable output, it must

  modify the input relocs and write them into the output file.

  There may also be object format dependent work to be done.

  The linker will also call the <<write_object_contents>> entry

  point when the BFD is closed.  The two entry points must work

  together in order to produce the correct output file.

  The details of how this works are inevitably dependent upon

  the specific object file format.  The a.out

  <<_bfd_final_link>> routine is <<NAME(aout,final_link)>>.

@menu

@* Information provided by the linker::

@* Relocating the section contents::

@* Writing the symbol table::

@end menu

INODE

Information provided by the linker, Relocating the section contents, Performing the Final Link, Performing the Final Link

SUBSUBSECTION

  Information provided by the linker

  Before the linker calls the <<_bfd_final_link>> entry point,

  it sets up some data structures for the function to use.

  The <<input_bfds>> field of the <<bfd_link_info>> structure

  will point to a list of all the input files included in the

  link.  These files are linked through the <<link.next>> field

  of the <<bfd>> structure.

  Each section in the output file will have a list of

  <<link_order>> structures attached to the <<map_head.link_order>>

  field (the <<link_order>> structure is defined in

  <<bfdlink.h>>).  These structures describe how to create the

  contents of the output section in terms of the contents of

  various input sections, fill constants, and, eventually, other

  types of information.  They also describe relocs that must be

  created by the BFD backend, but do not correspond to any input

  file; this is used to support -Ur, which builds constructors

  while generating a relocatable object file.

INODE

Relocating the section contents, Writing the symbol table, Information provided by the linker, Performing the Final Link

SUBSUBSECTION

  Relocating the section contents

  The <<_bfd_final_link>> function should look through the

  <<link_order>> structures attached to each section of the

  output file.  Each <<link_order>> structure should either be

  handled specially, or it should be passed to the function

  <<_bfd_default_link_order>> which will do the right thing

  (<<_bfd_default_link_order>> is defined in <<linker.c>>).

  For efficiency, a <<link_order>> of type

  <<bfd_indirect_link_order>> whose associated section belongs

  to a BFD of the same format as the output BFD must be handled

  specially.  This type of <<link_order>> describes part of an

  output section in terms of a section belonging to one of the

  input files.  The <<_bfd_final_link>> function should read the

  contents of the section and any associated relocs, apply the

  relocs to the section contents, and write out the modified

  section contents.  If performing a relocatable link, the

  relocs themselves must also be modified and written out.

@findex _bfd_relocate_contents

@findex _bfd_final_link_relocate

  The functions <<_bfd_relocate_contents>> and

  <<_bfd_final_link_relocate>> provide some general support for

  performing the actual relocations, notably overflow checking.

  Their arguments include information about the symbol the

  relocation is against and a <<reloc_howto_type>> argument

  which describes the relocation to perform.  These functions

  are defined in <<reloc.c>>.

  The a.out function which handles reading, relocating, and

  writing section contents is <<aout_link_input_section>>.  The

  actual relocation is done in <<aout_link_input_section_std>>

  and <<aout_link_input_section_ext>>.

INODE

Writing the symbol table, , Relocating the section contents, Performing the Final Link

SUBSUBSECTION

  Writing the symbol table

  The <<_bfd_final_link>> function must gather all the symbols

  in the input files and write them out.  It must also write out

  all the symbols in the global hash table.  This must be

  controlled by the <<strip>> and <<discard>> fields of the

  <<bfd_link_info>> structure.

  The local symbols of the input files will not have been

  entered into the linker hash table.  The <<_bfd_final_link>>

  routine must consider each input file and include the symbols

  in the output file.  It may be convenient to do this when

  looking through the <<link_order>> structures, or it may be

  done by stepping through the <<input_bfds>> list.

  The <<_bfd_final_link>> routine must also traverse the global

  hash table to gather all the externally visible symbols.  It

  is possible that most of the externally visible symbols may be

  written out when considering the symbols of each input file,

  but it is still necessary to traverse the hash table since the

  linker script may have defined some symbols that are not in

  any of the input files.

  The <<strip>> field of the <<bfd_link_info>> structure

  controls which symbols are written out.  The possible values

  are listed in <<bfdlink.h>>.  If the value is <<strip_some>>,

  then the <<keep_hash>> field of the <<bfd_link_info>>

  structure is a hash table of symbols to keep; each symbol

  should be looked up in this hash table, and only symbols which

  are present should be included in the output file.

  If the <<strip>> field of the <<bfd_link_info>> structure

  permits local symbols to be written out, the <<discard>> field

  is used to further controls which local symbols are included

  in the output file.  If the value is <<discard_l>>, then all

  local symbols which begin with a certain prefix are discarded;

  this is controlled by the <<bfd_is_local_label_name>> entry point.

  The a.out backend handles symbols by calling

  <<aout_link_write_symbols>> on each input BFD and then

  traversing the global hash table with the function

  <<aout_link_write_other_symbol>>.  It builds a string table

  while writing out the symbols, which is written to the output

  file at the end of <<NAME(aout,final_link)>>.

*/

static bool generic_link_add_object_symbols

  (bfd *, struct bfd_link_info *);

static bool generic_link_check_archive_element

  (bfd *, struct bfd_link_info *, struct bfd_link_hash_entry *, const char *,

   bool *);

static bool generic_link_add_symbol_list

  (bfd *, struct bfd_link_info *, bfd_size_type count, asymbol **);

static bool generic_add_output_symbol

  (bfd *, size_t *psymalloc, asymbol *);

static bool default_data_link_order

  (bfd *, struct bfd_link_info *, asection *, struct bfd_link_order *);

static bool default_indirect_link_order

  (bfd *, struct bfd_link_info *, asection *, struct bfd_link_order *,

   bool);

/* The link hash table structure is defined in bfdlink.h.  It provides

   a base hash table which the backend specific hash tables are built

   upon.  */

/* Routine to create an entry in the link hash table.  */

struct bfd_hash_entry *

_bfd_link_hash_newfunc (struct bfd_hash_entry *entry,

      struct bfd_hash_table *table,

      const char *string)

{

  /* Allocate the structure if it has not already been allocated by a

     subclass.  */

  if (entry == NULL)

    {

      entry = (struct bfd_hash_entry *)

    bfd_hash_allocate (table, sizeof (struct bfd_link_hash_entry));

      if (entry == NULL)

  return entry;

    }

  /* Call the allocation method of the superclass.  */

  entry = bfd_hash_newfunc (entry, table, string);

  if (entry)

    {

      struct bfd_link_hash_entry *h = (struct bfd_link_hash_entry *) entry;

      /* Initialize the local fields.  */

      memset ((char *) &h->root + sizeof (h->root), 0,

        sizeof (*h) - sizeof (h->root));

    }

  return entry;

}

/* Initialize a link hash table.  The BFD argument is the one

   responsible for creating this table.  */

bool

_bfd_link_hash_table_init

  (struct bfd_link_hash_table *table,

   bfd *abfd ATTRIBUTE_UNUSED,

   struct bfd_hash_entry *(*newfunc) (struct bfd_hash_entry *,

              struct bfd_hash_table *,

              const char *),

   unsigned int entsize)

{

  bool ret;

  BFD_ASSERT (!abfd->is_linker_output && !abfd->link.hash);

  table->undefs = NULL;

  table->undefs_tail = NULL;

  table->type = bfd_link_generic_hash_table;

  ret = bfd_hash_table_init (&table->table, newfunc, entsize);

  if (ret)

    {

      /* Arrange for destruction of this hash table on closing ABFD.  */

      table->hash_table_free = _bfd_generic_link_hash_table_free;

      abfd->link.hash = table;

      abfd->is_linker_output = true;

    }

  return ret;

}

/* Look up a symbol in a link hash table.  If follow is TRUE, we

   follow bfd_link_hash_indirect and bfd_link_hash_warning links to

   the real symbol.

.{* Return TRUE if the symbol described by a linker hash entry H

.   is going to be absolute.  Linker-script defined symbols can be

.   converted from absolute to section-relative ones late in the

.   link.  Use this macro to correctly determine whether the symbol

.   will actually end up absolute in output.  *}

.#define bfd_is_abs_symbol(H) \

.  (((H)->type == bfd_link_hash_defined \

.    || (H)->type == bfd_link_hash_defweak) \

.   && bfd_is_abs_section ((H)->u.def.section) \

.   && !(H)->rel_from_abs)

.

*/

struct bfd_link_hash_entry *

bfd_link_hash_lookup (struct bfd_link_hash_table *table,

          const char *string,

          bool create,

          bool copy,

          bool follow)

{

  struct bfd_link_hash_entry *ret;

  if (table == NULL || string == NULL)

    return NULL;

  ret = ((struct bfd_link_hash_entry *)

   bfd_hash_lookup (&table->table, string, create, copy));

  if (follow && ret != NULL)

    {

      while (ret->type == bfd_link_hash_indirect

       || ret->type == bfd_link_hash_warning)

  ret = ret->u.i.link;

    }

  return ret;

}

/* Look up a symbol in the main linker hash table if the symbol might

   be wrapped.  This should only be used for references to an

   undefined symbol, not for definitions of a symbol.  */

struct bfd_link_hash_entry *

bfd_wrapped_link_hash_lookup (bfd *abfd,

            struct bfd_link_info *info,

            const char *string,

            bool create,

            bool copy,

            bool follow)

{

  size_t amt;

  if (info->wrap_hash != NULL)

    {

      const char *l;

      char prefix = '\0';

      l = string;

      if (*l

    && (*l == bfd_get_symbol_leading_char (abfd)

        || *l == info->wrap_char))

  {

    prefix = *l;

    ++l;

  }

#undef WRAP

#define WRAP "__wrap_"

      if (bfd_hash_lookup (info->wrap_hash, l, false, false) != NULL)

  {

    char *n;

    struct bfd_link_hash_entry *h;

    /* This symbol is being wrapped.  We want to replace all

       references to SYM with references to __wrap_SYM.  */

    amt = strlen (l) + sizeof WRAP + 1;

    n = (char *) bfd_malloc (amt);

    if (n == NULL)

      return NULL;

    n[0] = prefix;

    n[1] = '\0';

    strcat (n, WRAP);

    strcat (n, l);

    h = bfd_link_hash_lookup (info->hash, n, create, true, follow);

    free (n);

    return h;

  }

#undef  REAL

#define REAL "__real_"

      if (*l == '_'

    && startswith (l, REAL)

    && bfd_hash_lookup (info->wrap_hash, l + sizeof REAL - 1,

            false, false) != NULL)

  {

    char *n;

    struct bfd_link_hash_entry *h;

    /* This is a reference to __real_SYM, where SYM is being

       wrapped.  We want to replace all references to __real_SYM

       with references to SYM.  */

    amt = strlen (l + sizeof REAL - 1) + 2;

    n = (char *) bfd_malloc (amt);

    if (n == NULL)

      return NULL;

    n[0] = prefix;

    n[1] = '\0';

    strcat (n, l + sizeof REAL - 1);

    h = bfd_link_hash_lookup (info->hash, n, create, true, follow);

    if (h != NULL)

      h->ref_real = 1;

    free (n);

    return h;

  }

#undef REAL

    }

  return bfd_link_hash_lookup (info->hash, string, create, copy, follow);

}

/* If H is a wrapped symbol, ie. the symbol name starts with "__wrap_"

   and the remainder is found in wrap_hash, return the real symbol.  */

struct bfd_link_hash_entry *

unwrap_hash_lookup (struct bfd_link_info *info,

        bfd *input_bfd,

        struct bfd_link_hash_entry *h)

{

  const char *l = h->root.string;

  if (*l

      && (*l == bfd_get_symbol_leading_char (input_bfd)

    || *l == info->wrap_char))

    ++l;

  if (startswith (l, WRAP))

    {

      l += sizeof WRAP - 1;

      if (bfd_hash_lookup (info->wrap_hash, l, false, false) != NULL)

  {

    char save = 0;

    if (l - (sizeof WRAP - 1) != h->root.string)

      {

        --l;

        save = *l;

        *(char *) l = *h->root.string;

      }

    h = bfd_link_hash_lookup (info->hash, l, false, false, false);

    if (save)

      *(char *) l = save;

  }

    }

  return h;

}

#undef WRAP

/* Traverse a generic link hash table.  Differs from bfd_hash_traverse

   in the treatment of warning symbols.  When warning symbols are

   created they replace the real symbol, so you don't get to see the

   real symbol in a bfd_hash_traverse.  This traversal calls func with

   the real symbol.  */

void

bfd_link_hash_traverse

  (struct bfd_link_hash_table *htab,

   bool (*func) (struct bfd_link_hash_entry *, void *),

   void *info)

{

  unsigned int i;

  htab->table.frozen = 1;

  for (i = 0; i < htab->table.size; i++)

    {

      struct bfd_link_hash_entry *p;

      p = (struct bfd_link_hash_entry *) htab->table.table[i];

      for (; p != NULL; p = (struct bfd_link_hash_entry *) p->root.next)

  if (!(*func) (p->type == bfd_link_hash_warning ? p->u.i.link : p, info))

    goto out;

    }

 out:

  htab->table.frozen = 0;

}

/* Add a symbol to the linker hash table undefs list.  */

void

bfd_link_add_undef (struct bfd_link_hash_table *table,

        struct bfd_link_hash_entry *h)

{

  BFD_ASSERT (h->u.undef.next == NULL);

  if (table->undefs_tail != NULL)

    table->undefs_tail->u.undef.next = h;

  if (table->undefs == NULL)

    table->undefs = h;

  table->undefs_tail = h;

}

/* The undefs list was designed so that in normal use we don't need to

   remove entries.  However, if symbols on the list are changed from

   bfd_link_hash_undefined to either bfd_link_hash_undefweak or

   bfd_link_hash_new for some reason, then they must be removed from the

   list.  Failure to do so might result in the linker attempting to add

   the symbol to the list again at a later stage.  */

void

bfd_link_repair_undef_list (struct bfd_link_hash_table *table)

{

  struct bfd_link_hash_entry **pun;

  pun = &table->undefs;

  while (*pun != NULL)

    {

      struct bfd_link_hash_entry *h = *pun;

      if (h->type == bfd_link_hash_new

    || h->type == bfd_link_hash_undefweak)

  {

    *pun = h->u.undef.next;

    h->u.undef.next = NULL;

    if (h == table->undefs_tail)

      {

        if (pun == &table->undefs)

    table->undefs_tail = NULL;

        else

    /* pun points at an u.undef.next field.  Go back to

       the start of the link_hash_entry.  */

    table->undefs_tail = (struct bfd_link_hash_entry *)

      ((char *) pun - ((char *) &h->u.undef.next - (char *) h));

        break;

      }

  }

      else

  pun = &h->u.undef.next;

    }

}

/* Routine to create an entry in a generic link hash table.  */

struct bfd_hash_entry *

_bfd_generic_link_hash_newfunc (struct bfd_hash_entry *entry,

        struct bfd_hash_table *table,

        const char *string)

{

  /* Allocate the structure if it has not already been allocated by a

     subclass.  */

  if (entry == NULL)

    {

      entry = (struct bfd_hash_entry *)

  bfd_hash_allocate (table, sizeof (struct generic_link_hash_entry));

      if (entry == NULL)

  return entry;

    }

  /* Call the allocation method of the superclass.  */

  entry = _bfd_link_hash_newfunc (entry, table, string);

  if (entry)

    {

      struct generic_link_hash_entry *ret;

      /* Set local fields.  */

      ret = (struct generic_link_hash_entry *) entry;

      ret->written = false;

      ret->sym = NULL;

    }

  return entry;

}

/* Create a generic link hash table.  */

struct bfd_link_hash_table *

_bfd_generic_link_hash_table_create (bfd *abfd)

{

  struct generic_link_hash_table *ret;

  size_t amt = sizeof (struct generic_link_hash_table);

  ret = (struct generic_link_hash_table *) bfd_malloc (amt);

  if (ret == NULL)

    return NULL;

  if (! _bfd_link_hash_table_init (&ret->root, abfd,

           _bfd_generic_link_hash_newfunc,

           sizeof (struct generic_link_hash_entry)))

    {

      free (ret);

      return NULL;

    }

  return &ret->root;

}

void

_bfd_generic_link_hash_table_free (bfd *obfd)

{

  struct generic_link_hash_table *ret;

  BFD_ASSERT (obfd->is_linker_output && obfd->link.hash);

  ret = (struct generic_link_hash_table *) obfd->link.hash;

  bfd_hash_table_free (&ret->root.table);

  free (ret);

  obfd->link.hash = NULL;

  obfd->is_linker_output = false;

}

/* Grab the symbols for an object file when doing a generic link.  We

   store the symbols in the outsymbols field.  We need to keep them

   around for the entire link to ensure that we only read them once.

   If we read them multiple times, we might wind up with relocs and

   the hash table pointing to different instances of the symbol

   structure.  */

bool

bfd_generic_link_read_symbols (bfd *abfd)

{

  if (bfd_get_outsymbols (abfd) == NULL)

    {

      long symsize;

      long symcount;

      symsize = bfd_get_symtab_upper_bound (abfd);

      if (symsize < 0)

  return false;

      abfd->outsymbols = bfd_alloc (abfd, symsize);

      if (bfd_get_outsymbols (abfd) == NULL && symsize != 0)

  return false;

      symcount = bfd_canonicalize_symtab (abfd, bfd_get_outsymbols (abfd));

      if (symcount < 0)

  return false;

      abfd->symcount = symcount;

    }

  return true;

}

/* Indicate that we are only retrieving symbol values from this

   section.  We want the symbols to act as though the values in the

   file are absolute.  */

void

_bfd_generic_link_just_syms (asection *sec,

           struct bfd_link_info *info ATTRIBUTE_UNUSED)

{

  sec->sec_info_type = SEC_INFO_TYPE_JUST_SYMS;

  sec->output_section = bfd_abs_section_ptr;

  sec->output_offset = sec->vma;

}

/* Copy the symbol type and other attributes for a linker script

   assignment from HSRC to HDEST.

   The default implementation does nothing.  */

void

_bfd_generic_copy_link_hash_symbol_type (bfd *abfd ATTRIBUTE_UNUSED,

    struct bfd_link_hash_entry *hdest ATTRIBUTE_UNUSED,

    struct bfd_link_hash_entry *hsrc ATTRIBUTE_UNUSED)

{

}

/* Generic function to add symbols from an object file to the

   global hash table.  */

bool

_bfd_generic_link_add_symbols (bfd *abfd, struct bfd_link_info *info)

{

  bool ret;

  switch (bfd_get_format (abfd))

    {

    case bfd_object:

      ret = generic_link_add_object_symbols (abfd, info);

      break;

    case bfd_archive:

      ret = (_bfd_generic_link_add_archive_symbols

       (abfd, info, generic_link_check_archive_element));

      break;

    default:

      bfd_set_error (bfd_error_wrong_format);

      ret = false;

    }

  return ret;

}

/* Add symbols from an object file to the global hash table.  */

static bool

generic_link_add_object_symbols (bfd *abfd,

         struct bfd_link_info *info)

{

  bfd_size_type symcount;

  struct bfd_symbol **outsyms;

  if (!bfd_generic_link_read_symbols (abfd))

    return false;

  symcount = _bfd_generic_link_get_symcount (abfd);

  outsyms = _bfd_generic_link_get_symbols (abfd);

  return generic_link_add_symbol_list (abfd, info, symcount, outsyms);

}

/* Generic function to add symbols from an archive file to the global

   hash file.  This function presumes that the archive symbol table

   has already been read in (this is normally done by the

   bfd_check_format entry point).  It looks through the archive symbol

   table for symbols that are undefined or common in the linker global

   symbol hash table.  When one is found, the CHECKFN argument is used

   to see if an object file should be included.  This allows targets

   to customize common symbol behaviour.  CHECKFN should set *PNEEDED

   to TRUE if the object file should be included, and must also call

   the bfd_link_info add_archive_element callback function and handle

   adding the symbols to the global hash table.  CHECKFN must notice

   if the callback indicates a substitute BFD, and arrange to add

   those symbols instead if it does so.  CHECKFN should only return

   FALSE if some sort of error occurs.  */

bool

_bfd_generic_link_add_archive_symbols

  (bfd *abfd,

   struct bfd_link_info *info,

   bool (*checkfn) (bfd *, struct bfd_link_info *,

        struct bfd_link_hash_entry *, const char *, bool *))

{

  bool loop;

  bfd_size_type amt;

  unsigned char *included;

  if (! bfd_has_map (abfd))

    {

      /* An empty archive is a special case.  */

      if (bfd_openr_next_archived_file (abfd, NULL) == NULL)

  return true;

      bfd_set_error (bfd_error_no_armap);

      return false;

    }

  amt = bfd_ardata (abfd)->symdef_count;

  if (amt == 0)

    return true;

  amt *= sizeof (*included);

  included = (unsigned char *) bfd_zmalloc (amt);

  if (included == NULL)

    return false;

  do

    {

      carsym *arsyms;

      carsym *arsym_end;

      carsym *arsym;

      unsigned int indx;

      file_ptr last_ar_offset = -1;

      bool needed = false;

      bfd *element = NULL;

      loop = false;

      arsyms = bfd_ardata (abfd)->symdefs;

      arsym_end = arsyms + bfd_ardata (abfd)->symdef_count;

      for (arsym = arsyms, indx = 0; arsym < arsym_end; arsym++, indx++)

  {

    struct bfd_link_hash_entry *h;

    struct bfd_link_hash_entry *undefs_tail;

    if (included[indx])

      continue;

    if (needed && arsym->file_offset == last_ar_offset)

      {

        included[indx] = 1;

        continue;

      }

    if (arsym->name == NULL)

      goto error_return;

    h = bfd_link_hash_lookup (info->hash, arsym->name,

            false, false, true);

    if (h == NULL

        && info->pei386_auto_import

        && startswith (arsym->name, "__imp_"))

      h = bfd_link_hash_lookup (info->hash, arsym->name + 6,

              false, false, true);

    if (h == NULL)

      continue;

    if (h->type != bfd_link_hash_undefined

        && h->type != bfd_link_hash_common)

      {

        if (h->type != bfd_link_hash_undefweak)

    /* Symbol must be defined.  Don't check it again.  */

    included[indx] = 1;

        continue;

      }

    if (last_ar_offset != arsym->file_offset)

      {

        last_ar_offset = arsym->file_offset;

        element = _bfd_get_elt_at_filepos (abfd, last_ar_offset,

             info);

        if (element == NULL

      || !bfd_check_format (element, bfd_object))

    goto error_return;

      }

    undefs_tail = info->hash->undefs_tail;

    /* CHECKFN will see if this element should be included, and

       go ahead and include it if appropriate.  */

    if (! (*checkfn) (element, info, h, arsym->name, &needed))

      goto error_return;

    if (needed)

      {

        unsigned int mark;

        /* Look backward to mark all symbols from this object file

     which we have already seen in this pass.  */