* config/tc-mn10200.c (md_parse_option <c, arg>): Add ATTRIBUTE_UNUSED.

[binutils.git] / bfd / doc / bfd.texinfo

\input texinfo.tex
@setfilename bfd.info
@c Copyright 1988, 1989, 1990, 1991, 1992, 1993, 1994, 1997, 2000
@c Free Software Foundation, Inc.
@c 
@tex
% NOTE LOCAL KLUGE TO AVOID TOO MUCH WHITESPACE
\global\long\def\example{%
\begingroup
\let\aboveenvbreak=\par
\let\afterenvbreak=\par
\parskip=0pt
\lisp}
\global\long\def\Eexample{%
\Elisp
\endgroup
\vskip -\parskip% to cancel out effect of following \par
}
@end tex
@synindex fn cp

@ifinfo
@format
START-INFO-DIR-ENTRY
* Bfd: (bfd).                   The Binary File Descriptor library.
END-INFO-DIR-ENTRY
@end format
@end ifinfo

@ifinfo
This file documents the BFD library.

Copyright (C) 1991, 2000, 2001 Free Software Foundation, Inc.

      Permission is granted to copy, distribute and/or modify this document
      under the terms of the GNU Free Documentation License, Version 1.1
      or any later version published by the Free Software Foundation;
      with no Invariant Sections, with no Front-Cover Texts, and with no
      Back-Cover Texts.  A copy of the license is included in the
      section entitled "GNU Free Documentation License".

@ignore
Permission is granted to process this file through Tex and print the
results, provided the printed document carries copying permission
notice identical to this one except for the removal of this paragraph
(this paragraph not being relevant to the printed manual).

@end ignore
@end ifinfo
@iftex
@c@finalout
@setchapternewpage on
@c@setchapternewpage odd
@settitle LIB BFD, the Binary File Descriptor Library
@titlepage
@title{libbfd}
@subtitle{The Binary File Descriptor Library}
@sp 1
@subtitle First Edition---BFD version < 3.0  % Since no product is stable berfore version 3.0 :-)
@subtitle Original Document Created: April 1991
@author {Steve Chamberlain}
@author {Cygnus Support}
@page

@tex
\def\$#1${{#1}}  % Kluge: collect RCS revision info without $...$
\xdef\manvers{\1.5}  % For use in headers, footers too
{\parskip=0pt
\hfill Free Software Foundation\par
\hfill sac\@www.gnu.org\par
\hfill {\it BFD}, \manvers\par
\hfill \TeX{}info \texinfoversion\par
}
\global\parindent=0pt % Steve likes it this way
@end tex

@vskip 0pt plus 1filll
Copyright @copyright{} 1991, 2001 Free Software Foundation, Inc.

      Permission is granted to copy, distribute and/or modify this document
      under the terms of the GNU Free Documentation License, Version 1.1
      or any later version published by the Free Software Foundation;
      with no Invariant Sections, with no Front-Cover Texts, and with no
      Back-Cover Texts.  A copy of the license is included in the
      section entitled "GNU Free Documentation License".

@end titlepage
@end iftex

@node Top, Overview, (dir), (dir)
@ifinfo
This file documents the binary file descriptor library libbfd.
@end ifinfo

@menu
* Overview::                    Overview of BFD
* BFD front end::               BFD front end
* BFD back ends::               BFD back ends
* GNU Free Documentation License::  GNU Free Documentation License
* Index::                       Index
@end menu

@node Overview, BFD front end, Top, Top
@chapter Introduction
@cindex BFD
@cindex what is it?
BFD is a package which allows applications to use the
same routines to operate on object files whatever the object file
format.  A new object file format can be supported simply by
creating a new BFD back end and adding it to the library.

BFD is split into two parts: the front end, and the back ends (one for
each object file format).
@itemize @bullet
@item The front end of BFD provides the interface to the user. It manages
memory and various canonical data structures. The front end also
decides which back end to use and when to call back end routines.
@item The back ends provide BFD its view of the real world. Each back
end provides a set of calls which the BFD front end can use to maintain
its canonical form. The back ends also may keep around information for
their own use, for greater efficiency.
@end itemize
@menu
* History::                     History
* How It Works::                How It Works
* What BFD Version 2 Can Do::   What BFD Version 2 Can Do
@end menu

@node History, How It Works, Overview, Overview
@section History

One spur behind BFD was the desire, on the part of the GNU 960 team at
Intel Oregon, for interoperability of applications on their COFF and
b.out file formats.  Cygnus was providing GNU support for the team, and
was contracted to provide the required functionality.

The name came from a conversation David Wallace was having with Richard
Stallman about the library: RMS said that it would be quite hard---David
said ``BFD''.  Stallman was right, but the name stuck.

At the same time, Ready Systems wanted much the same thing, but for
different object file formats: IEEE-695, Oasys, Srecords, a.out and 68k
coff.

BFD was first implemented by members of Cygnus Support; Steve
Chamberlain (@code{sac@@cygnus.com}), John Gilmore
(@code{gnu@@cygnus.com}), K.  Richard Pixley (@code{rich@@cygnus.com})
and David Henkel-Wallace (@code{gumby@@cygnus.com}).



@node How It Works, What BFD Version 2 Can Do, History, Overview
@section How To Use BFD

To use the library, include @file{bfd.h} and link with @file{libbfd.a}. 

BFD provides a common interface to the parts of an object file
for a calling application. 

When an application sucessfully opens a target file (object, archive, or
whatever), a pointer to an internal structure is returned. This pointer
points to a structure called @code{bfd}, described in
@file{bfd.h}.  Our convention is to call this pointer a BFD, and
instances of it within code @code{abfd}.  All operations on
the target object file are applied as methods to the BFD.  The mapping is
defined within @code{bfd.h} in a set of macros, all beginning
with @samp{bfd_} to reduce namespace pollution.

For example, this sequence does what you would probably expect:
return the number of sections in an object file attached to a BFD
@code{abfd}. 

@lisp
@c @cartouche
#include "bfd.h"

unsigned int number_of_sections(abfd)
bfd *abfd;
@{
  return bfd_count_sections(abfd);
@}
@c @end cartouche
@end lisp

The abstraction used within BFD is that an object file has:

@itemize @bullet
@item
a header,
@item
a number of sections containing raw data (@pxref{Sections}),
@item
a set of relocations (@pxref{Relocations}), and
@item
some symbol information (@pxref{Symbols}).
@end itemize
@noindent
Also, BFDs opened for archives have the additional attribute of an index
and contain subordinate BFDs. This approach is fine for a.out and coff,
but loses efficiency when applied to formats such as S-records and
IEEE-695.

@node What BFD Version 2 Can Do,  , How It Works, Overview
@section What BFD Version 2 Can Do
@include bfdsumm.texi

@node BFD front end, BFD back ends, Overview, Top
@chapter BFD front end
@include bfdt.texi
@include bfdio.texi

@menu
* Memory Usage::
* Initialization::
* Sections::
* Symbols::
* Archives::
* Formats::
* Relocations::
* Core Files::
* Targets::
* Architectures::
* Opening and Closing::
* Internal::
* File Caching::
* Linker Functions::
* Hash Tables::
@end menu

@node Memory Usage, Initialization, BFD front end, BFD front end
@section Memory usage
BFD keeps all of its internal structures in obstacks. There is one obstack
per open BFD file, into which the current state is stored. When a BFD is
closed, the obstack is deleted, and so everything which has been
allocated by BFD for the closing file is thrown away.

BFD does not free anything created by an application, but pointers into
@code{bfd} structures become invalid on a @code{bfd_close}; for example,
after a @code{bfd_close} the vector passed to
@code{bfd_canonicalize_symtab} is still around, since it has been
allocated by the application, but the data that it pointed to are
lost.

The general rule is to not close a BFD until all operations dependent
upon data from the BFD have been completed, or all the data from within
the file has been copied. To help with the management of memory, there
is a function (@code{bfd_alloc_size}) which returns the number of bytes
in obstacks associated with the supplied BFD. This could be used to
select the greediest open BFD, close it to reclaim the memory, perform
some operation and reopen the BFD again, to get a fresh copy of the data
structures.

@node Initialization, Sections, Memory Usage, BFD front end
@include  init.texi

@node Sections, Symbols, Initialization, BFD front end
@include  section.texi

@node Symbols, Archives, Sections, BFD front end
@include  syms.texi

@node Archives, Formats, Symbols, BFD front end
@include  archive.texi

@node Formats, Relocations, Archives, BFD front end
@include  format.texi

@node Relocations, Core Files, Formats, BFD front end
@include  reloc.texi

@node Core Files, Targets, Relocations, BFD front end
@include  core.texi

@node Targets, Architectures, Core Files, BFD front end
@include  targets.texi

@node Architectures, Opening and Closing, Targets, BFD front end
@include  archures.texi

@node Opening and Closing, Internal, Architectures, BFD front end
@include  opncls.texi

@node Internal, File Caching, Opening and Closing, BFD front end
@include  libbfd.texi

@node File Caching, Linker Functions, Internal, BFD front end
@include  cache.texi

@node Linker Functions, Hash Tables, File Caching, BFD front end
@include  linker.texi

@node Hash Tables, , Linker Functions, BFD front end
@include  hash.texi

@node BFD back ends, GNU Free Documentation License, BFD front end, Top
@chapter BFD back ends
@menu
* What to Put Where::
* aout ::       a.out backends
* coff ::       coff backends
* elf  ::       elf backends
* mmo  ::       mmo backend
@ignore
* oasys ::      oasys backends
* ieee ::       ieee backend
* srecord ::    s-record backend
@end ignore
@end menu
@node What to Put Where, aout, BFD back ends, BFD back ends
All of BFD lives in one directory.

@node aout, coff, What to Put Where, BFD back ends
@include  aoutx.texi

@node coff, elf, aout, BFD back ends
@include  coffcode.texi

@node elf, mmo, coff, BFD back ends
@include  elf.texi
@c Leave this out until the file has some actual contents...
@c @include  elfcode.texi

@node mmo,  , elf, BFD back ends
@include  mmo.texi

@node GNU Free Documentation License, Index, BFD back ends, Top
@chapter GNU Free Documentation License
@cindex GNU Free Documentation License

                GNU Free Documentation License
                
                   Version 1.1, March 2000

 Copyright (C) 2000  Free Software Foundation, Inc.
  59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
     
 Everyone is permitted to copy and distribute verbatim copies
 of this license document, but changing it is not allowed.


0. PREAMBLE

The purpose of this License is to make a manual, textbook, or other
written document "free" in the sense of freedom: to assure everyone
the effective freedom to copy and redistribute it, with or without
modifying it, either commercially or noncommercially.  Secondarily,
this License preserves for the author and publisher a way to get
credit for their work, while not being considered responsible for
modifications made by others.

This License is a kind of "copyleft", which means that derivative
works of the document must themselves be free in the same sense.  It
complements the GNU General Public License, which is a copyleft
license designed for free software.

We have designed this License in order to use it for manuals for free
software, because free software needs free documentation: a free
program should come with manuals providing the same freedoms that the
software does.  But this License is not limited to software manuals;
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1. APPLICABILITY AND DEFINITIONS

This License applies to any manual or other work that contains a
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The "Invariant Sections" are certain Secondary Sections whose titles
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You may copy and distribute a Modified Version of the Document under
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and modification of the Modified Version to whoever possesses a copy
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A. Use in the Title Page (and on the covers, if any) a title distinct
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B. List on the Title Page, as authors, one or more persons or entities
   responsible for authorship of the modifications in the Modified
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C. State on the Title page the name of the publisher of the
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If the Cover Text requirement of section 3 is applicable to these
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8. TRANSLATION

Translation is considered a kind of modification, so you may
distribute translations of the Document under the terms of section 4.
Replacing Invariant Sections with translations requires special
permission from their copyright holders, but you may include
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original versions of these Invariant Sections.  You may include a
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License, the original English version will prevail.


9. TERMINATION

You may not copy, modify, sublicense, or distribute the Document except
as expressly provided for under this License.  Any other attempt to
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automatically terminate your rights under this License.  However,
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10. FUTURE REVISIONS OF THIS LICENSE

The Free Software Foundation may publish new, revised versions
of the GNU Free Documentation License from time to time.  Such new
versions will be similar in spirit to the present version, but may
differ in detail to address new problems or concerns.  See
http://www.gnu.org/copyleft/.

Each version of the License is given a distinguishing version number.
If the Document specifies that a particular numbered version of this
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following the terms and conditions either of that specified version or
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Free Software Foundation.  If the Document does not specify a version
number of this License, you may choose any version ever published (not
as a draft) by the Free Software Foundation.


ADDENDUM: How to use this License for your documents

To use this License in a document you have written, include a copy of
the License in the document and put the following copyright and
license notices just after the title page:

@smallexample
    Copyright (c)  YEAR  YOUR NAME.
    Permission is granted to copy, distribute and/or modify this document
    under the terms of the GNU Free Documentation License, Version 1.1
    or any later version published by the Free Software Foundation;
    with the Invariant Sections being LIST THEIR TITLES, with the
    Front-Cover Texts being LIST, and with the Back-Cover Texts being LIST.
    A copy of the license is included in the section entitled "GNU
    Free Documentation License".
@end smallexample

If you have no Invariant Sections, write "with no Invariant Sections"
instead of saying which ones are invariant.  If you have no
Front-Cover Texts, write "no Front-Cover Texts" instead of
"Front-Cover Texts being LIST"; likewise for Back-Cover Texts.

If your document contains nontrivial examples of program code, we
recommend releasing these examples in parallel under your choice of
free software license, such as the GNU General Public License,
to permit their use in free software.

@node Index,  , GNU Free Documentation License , Top
@unnumbered Index
@printindex cp

@tex
% I think something like @colophon should be in texinfo.  In the
% meantime:
\long\def\colophon{\hbox to0pt{}\vfill
\centerline{The body of this manual is set in}
\centerline{\fontname\tenrm,}
\centerline{with headings in {\bf\fontname\tenbf}}
\centerline{and examples in {\tt\fontname\tentt}.}
\centerline{{\it\fontname\tenit\/} and}
\centerline{{\sl\fontname\tensl\/}}
\centerline{are used for emphasis.}\vfill}
\page\colophon
% Blame: doc@cygnus.com, 28mar91.
@end tex

@contents
@bye