bfdlink.h

MinGW+MSYS必备的开发工具链

/* bfdlink.h -- header file for BFD link routines
   Copyright 1993, 1994, 1995, 1996, 1997, 1998, 1999, 2000, 2001, 2002,
   2003, 2004, 2005 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 2 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.  */

#ifndef BFDLINK_H
#define BFDLINK_H

/* Which symbols to strip during a link.  */
enum bfd_link_strip
{
  strip_none,		/* Don't strip any symbols.  */
  strip_debugger,	/* Strip debugging symbols.  */
  strip_some,		/* keep_hash is the list of symbols to keep.  */
  strip_all		/* Strip all symbols.  */
};

/* Which local symbols to discard during a link.  This is irrelevant
   if strip_all is used.  */
enum bfd_link_discard
{
  discard_sec_merge,	/* Discard local temporary symbols in SEC_MERGE
			   sections.  */
  discard_none,		/* Don't discard any locals.  */
  discard_l,		/* Discard local temporary symbols.  */
  discard_all		/* Discard all locals.  */
};

/* Describes the type of hash table entry structure being used.
   Different hash table structure have different fields and so
   support different linking features.  */
enum bfd_link_hash_table_type
  {
    bfd_link_generic_hash_table,
    bfd_link_elf_hash_table
  };

/* These are the possible types of an entry in the BFD link hash
   table.  */

enum bfd_link_hash_type
{
  bfd_link_hash_new,		/* Symbol is new.  */
  bfd_link_hash_undefined,	/* Symbol seen before, but undefined.  */
  bfd_link_hash_undefweak,	/* Symbol is weak and undefined.  */
  bfd_link_hash_defined,	/* Symbol is defined.  */
  bfd_link_hash_defweak,	/* Symbol is weak and defined.  */
  bfd_link_hash_common,		/* Symbol is common.  */
  bfd_link_hash_indirect,	/* Symbol is an indirect link.  */
  bfd_link_hash_warning		/* Like indirect, but warn if referenced.  */
};

enum bfd_link_common_skip_ar_aymbols
{
  bfd_link_common_skip_none,
  bfd_link_common_skip_text,
  bfd_link_common_skip_data,
  bfd_link_common_skip_all
};

/* The linking routines use a hash table which uses this structure for
   its elements.  */

struct bfd_link_hash_entry
{
  /* Base hash table entry structure.  */
  struct bfd_hash_entry root;

  /* Type of this entry.  */
  enum bfd_link_hash_type type;

  /* A union of information depending upon the type.  */
  union
    {
      /* Nothing is kept for bfd_hash_new.  */
      /* bfd_link_hash_undefined, bfd_link_hash_undefweak.  */
      struct
	{
	  /* Undefined and common symbols are kept in a linked list through
	     this field.  This field is present in all of the union element
	     so that we don't need to remove entries from the list when we
	     change their type.  Removing entries would either require the
	     list to be doubly linked, which would waste more memory, or
	     require a traversal.  When an undefined or common symbol is
	     created, it should be added to this list, the head of which is in
	     the link hash table itself.  As symbols are defined, they need
	     not be removed from the list; anything which reads the list must
	     doublecheck the symbol type.

	     Weak symbols are not kept on this list.

	     Defined and defweak symbols use this field as a reference marker.
	     If the field is not NULL, or this structure is the tail of the
	     undefined symbol list, the symbol has been referenced.  If the
	     symbol is undefined and becomes defined, this field will
	     automatically be non-NULL since the symbol will have been on the
	     undefined symbol list.  */
	  struct bfd_link_hash_entry *next;
	  bfd *abfd;		/* BFD symbol was found in.  */
	  bfd *weak;		/* BFD weak symbol was found in.  */
	} undef;
      /* bfd_link_hash_defined, bfd_link_hash_defweak.  */
      struct
	{
	  struct bfd_link_hash_entry *next;
	  asection *section;	/* Symbol section.  */
	  bfd_vma value;	/* Symbol value.  */
	} def;
      /* bfd_link_hash_indirect, bfd_link_hash_warning.  */
      struct
	{
	  struct bfd_link_hash_entry *next;
	  struct bfd_link_hash_entry *link;	/* Real symbol.  */
	  const char *warning;	/* Warning (bfd_link_hash_warning only).  */
	} i;
      /* bfd_link_hash_common.  */
      struct
	{
	  struct bfd_link_hash_entry *next;
	  /* The linker needs to know three things about common
	     symbols: the size, the alignment, and the section in
	     which the symbol should be placed.  We store the size
	     here, and we allocate a small structure to hold the
	     section and the alignment.  The alignment is stored as a
	     power of two.  We don't store all the information
	     directly because we don't want to increase the size of
	     the union; this structure is a major space user in the
	     linker.  */
	  struct bfd_link_hash_common_entry
	    {
	      unsigned int alignment_power;	/* Alignment.  */
	      asection *section;		/* Symbol section.  */
	    } *p;
	  bfd_size_type size;	/* Common symbol size.  */
	} c;
    } u;
};

/* This is the link hash table.  It is a derived class of
   bfd_hash_table.  */

struct bfd_link_hash_table
{
  /* The hash table itself.  */
  struct bfd_hash_table table;
  /* The back end which created this hash table.  This indicates the
     type of the entries in the hash table, which is sometimes
     important information when linking object files of different
     types together.  */
  const bfd_target *creator;
  /* A linked list of undefined and common symbols, linked through the
     next field in the bfd_link_hash_entry structure.  */
  struct bfd_link_hash_entry *undefs;
  /* Entries are added to the tail of the undefs list.  */
  struct bfd_link_hash_entry *undefs_tail;
  /* The type of the link hash table.  */
  enum bfd_link_hash_table_type type;
};

/* Look up an entry in a link hash table.  If FOLLOW is TRUE, this
   follows bfd_link_hash_indirect and bfd_link_hash_warning links to
   the real symbol.  */
extern struct bfd_link_hash_entry *bfd_link_hash_lookup
  (struct bfd_link_hash_table *, const char *, bfd_boolean create,
   bfd_boolean copy, bfd_boolean follow);

/* Look up an entry 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.  */

extern struct bfd_link_hash_entry *bfd_wrapped_link_hash_lookup
  (bfd *, struct bfd_link_info *, const char *, bfd_boolean,
   bfd_boolean, bfd_boolean);

/* Traverse a link hash table.  */
extern void bfd_link_hash_traverse
  (struct bfd_link_hash_table *,
    bfd_boolean (*) (struct bfd_link_hash_entry *, void *),
    void *);

/* Add an entry to the undefs list.  */
extern void bfd_link_add_undef
  (struct bfd_link_hash_table *, struct bfd_link_hash_entry *);

/* Remove symbols from the undefs list that don't belong there.  */
extern void bfd_link_repair_undef_list
  (struct bfd_link_hash_table *table);

struct bfd_sym_chain
{
  struct bfd_sym_chain *next;
  const char *name;
};

/* How to handle unresolved symbols.
   There are four possibilities which are enumerated below:  */
enum report_method
{
  /* This is the initial value when then link_info structure is created.
     It allows the various stages of the linker to determine whether they
     allowed to set the value.  */
  RM_NOT_YET_SET = 0,
  RM_IGNORE,
  RM_GENERATE_WARNING,
  RM_GENERATE_ERROR
};

/* This structure holds all the information needed to communicate
   between BFD and the linker when doing a link.  */

struct bfd_link_info
{
  /* TRUE if BFD should generate a relocatable object file.  */
  unsigned int relocatable: 1;

  /* TRUE if BFD should generate relocation information in the final
     executable.  */
  unsigned int emitrelocations: 1;

  /* TRUE if BFD should generate a "task linked" object file,
     similar to relocatable but also with globals converted to
     statics.  */
  unsigned int task_link: 1;

  /* TRUE if BFD should generate a shared object.  */
  unsigned int shared: 1;

  /* TRUE if BFD should pre-bind symbols in a shared object.  */
  unsigned int symbolic: 1;

  /* TRUE if BFD should export all symbols in the dynamic symbol table
     of an executable, rather than only those used.  */
  unsigned int export_dynamic: 1;

  /* TRUE if shared objects should be linked directly, not shared.  */
  unsigned int static_link: 1;

  /* TRUE if the output file should be in a traditional format.  This
     is equivalent to the setting of the BFD_TRADITIONAL_FORMAT flag
     on the output file, but may be checked when reading the input
     files.  */
  unsigned int traditional_format: 1;

  /* TRUE if we want to produced optimized output files.  This might
     need much more time and therefore must be explicitly selected.  */
  unsigned int optimize: 1;

  /* TRUE if ok to have multiple definition.  */
  unsigned int allow_multiple_definition: 1;

  /* TRUE if ok to have version with no definition.  */
  unsigned int allow_undefined_version: 1;

  /* TRUE if a default symbol version should be created and used for
     exported symbols.  */
  unsigned int create_default_symver: 1;

  /* TRUE if a default symbol version should be created and used for
     imported symbols.  */
  unsigned int default_imported_symver: 1;

  /* TRUE if symbols should be retained in memory, FALSE if they
     should be freed and reread.  */
  unsigned int keep_memory: 1;

  /* TRUE if every symbol should be reported back via the notice
     callback.  */
  unsigned int notice_all: 1;

  /* TRUE if executable should not contain copy relocs.
     Setting this true may result in a non-sharable text segment.  */
  unsigned int nocopyreloc: 1;

  /* TRUE if the new ELF dynamic tags are enabled. */
  unsigned int new_dtags: 1;

  /* TRUE if non-PLT relocs should be merged into one reloc section
     and sorted so that relocs against the same symbol come together.  */
  unsigned int combreloc: 1;

  /* TRUE if .eh_frame_hdr section and PT_GNU_EH_FRAME ELF segment
     should be created.  */
  unsigned int eh_frame_hdr: 1;

  /* TRUE if global symbols in discarded sections should be stripped.  */
  unsigned int strip_discarded: 1;

  /* TRUE if generating a position independent executable.  */
  unsigned int pie: 1;

  /* TRUE if generating an executable, position independent or not.  */
  unsigned int executable : 1;

  /* TRUE if PT_GNU_STACK segment should be created with PF_R|PF_W|PF_X
     flags.  */
  unsigned int execstack: 1;

  /* TRUE if PT_GNU_STACK segment should be created with PF_R|PF_W
     flags.  */
  unsigned int noexecstack: 1;

  /* TRUE if PT_GNU_RELRO segment should be created.  */
  unsigned int relro: 1;

  /* TRUE if we should warn when adding a DT_TEXTREL to a shared object.  */
  unsigned int warn_shared_textrel: 1;

  /* TRUE if unreferenced sections should be removed.  */
  unsigned int gc_sections: 1;

  /* TRUE if user shoudl be informed of removed unreferenced sections.  */
  unsigned int print_gc_sections: 1;

  /* TRUE if .hash section should be created.  */
  unsigned int emit_hash: 1;

  /* TRUE if .gnu.hash section should be created.  */
  unsigned int emit_gnu_hash: 1;

  /* What to do with unresolved symbols in an object file.
     When producing executables the default is GENERATE_ERROR.
     When producing shared libraries the default is IGNORE.  The
     assumption with shared libraries is that the reference will be
     resolved at load/execution time.  */
  enum report_method unresolved_syms_in_objects;

  /* What to do with unresolved symbols in a shared library.
     The same defaults apply.  */
  enum report_method unresolved_syms_in_shared_libs;

  /* Which symbols to strip.  */
  enum bfd_link_strip strip;

  /* Which local symbols to discard.  */
  enum bfd_link_discard discard;

  /* Criteria for skipping symbols when detemining
     whether to include an object from an archive. */
  enum bfd_link_common_skip_ar_aymbols common_skip_ar_aymbols;

  /* Char that may appear as the first char of a symbol, but should be
     skipped (like symbol_leading_char) when looking up symbols in
     wrap_hash.  Used by PowerPC Linux for 'dot' symbols.  */
  char wrap_char;

  /* Function callbacks.  */
  const struct bfd_link_callbacks *callbacks;