\input texinfo
@setfilename ld.info
-@c $Id$
@syncodeindex ky cp
-@smallbook
-@c @cropmarks
+@include configdoc.texi
+@c (configdoc.texi is generated by the Makefile)
+
+@c @smallbook
@ifinfo
@format
START-INFO-DIR-ENTRY
-* Ld: (ld). The GNU linker.
+* Ld:: The GNU linker.
END-INFO-DIR-ENTRY
@end format
@end ifinfo
@ifinfo
-This file documents the GNU linker GLD.
+This file documents the GNU linker LD.
-Copyright (C) 1991 Free Software Foundation, Inc.
+Copyright (C) 1991, 1992, 1993, 1994 Free Software Foundation, Inc.
Permission is granted to make and distribute verbatim copies of
this manual provided the copyright notice and this permission notice
are preserved on all copies.
+Permission is granted to copy and distribute modified versions of this
+manual under the conditions for verbatim copying, provided also that
+the entire resulting derived work is distributed under the terms of a
+permission notice identical to this one.
+
+Permission is granted to copy and distribute translations of this manual
+into another language, under the above conditions for modified versions.
+
@ignore
Permission is granted to process this file through Tex and print the
results, provided the printed document carries copying permission
(this paragraph not being relevant to the printed manual).
@end ignore
-Permission is granted to copy and distribute modified versions of this
-manual under the conditions for verbatim copying, provided also that the
-section entitled ``GNU General Public License'' is included exactly as
-in the original, and provided that the entire resulting derived work is
-distributed under the terms of a permission notice identical to this
-one.
-
-Permission is granted to copy and distribute translations of this manual
-into another language, under the above conditions for modified versions,
-except that the section entitled ``GNU General Public License'' may be
-included in a translation approved by the author instead of in the
-original English.
@end ifinfo
@iftex
@finalout
@setchapternewpage odd
-@settitle GLD, the GNU linker
+@settitle Using LD, the GNU linker
@titlepage
-@title gld
+@title Using ld
@subtitle The GNU linker
@sp 1
-@subtitle Second Edition---@code{gld} version 2.0
-@subtitle April 1991
+@subtitle @code{ld} version 2
+@subtitle January 1994
@author Steve Chamberlain and Roland Pesch
@author Cygnus Support
@page
@tex
-\def\$#1${{#1}} % Kluge: collect RCS revision info without $...$
-\xdef\manvers{\$Revision$} % For use in headers, footers too
{\parskip=0pt
\hfill Cygnus Support\par
\hfill steve\@cygnus.com, pesch\@cygnus.com\par
-\hfill {\it GLD, the GNU linker}, \manvers\par
-\hfill \TeX{}info \texinfoversion\par
+\hfill {\it Using LD, the GNU linker}\par
+\hfill Edited by Jeffrey Osier (jeffrey\@cygnus.com)\par
+\hfill and Roland Pesch (pesch\@cygnus.com)\par
}
\global\parindent=0pt % Steve likes it this way.
@end tex
@vskip 0pt plus 1filll
-Copyright @copyright{} 1991 Free Software Foundation, Inc.
+Copyright @copyright{} 1991, 1992, 1993, 1994 Free Software Foundation, Inc.
Permission is granted to make and distribute verbatim copies of
this manual provided the copyright notice and this permission notice
@end iftex
@c FIXME: Talk about importance of *order* of args, cmds to linker!
-@node Top, Overview, (dir), (dir)
@ifinfo
-This file documents the GNU linker gld.
-@end ifinfo
+@node Top
+@top Using ld
+This file documents the GNU linker ld.
@menu
-* Overview:: Overview
-* Invocation:: Invocation
-* Commands:: Command Language
-* Machine Dependent:: Machine Dependent Features
-* BFD:: BFD
-* Index:: Index
-
- --- The Detailed Node Listing ---
-
-Invocation
-
-* Options:: Command Line Options
-* Environment:: Environment Variables
-
-Command Language
-
-* Scripts:: Linker Scripts
-* Expressions:: Expressions
-* MEMORY:: MEMORY Command
-* SECTIONS:: SECTIONS Command
-* Entry Point:: The Entry Point
-* Other Commands:: Other Commands
-
-Expressions
-
-* Integers:: Integers
-* Symbols:: Symbol Names
-* Location Counter:: The Location Counter
-* Operators:: Operators
-* Evaluation:: Evaluation
-* Assignment:: Assignment: Defining Symbols
-* Built-ins:: Built-In Functions
-
-SECTIONS Command
-
-* Section Definition:: Section Definitions
-* Section Contents:: Section Contents
-* Section Options:: Optional Section Attributes
-
-Machine Dependent Features
-
-* H8/300:: @code{gld} and the H8/300
-* i960:: @code{gld} and the Intel 960 family
-* m68k:: @code{gld} and the Motorola 68000 family
-* m88k:: @code{gld} and the Motorola 880x0 family
-
-@code{gld} and the Intel 960 family
-
-* i960-arch:: Linking for a Specific i960 Architecture
-* i960-emulation:: Emulating Other i960 Linkers
-* i960-commands:: Command Language Extensions for i960
-
-BFD
-
-* BFD outline:: How it works: an outline of BFD
-* BFD information loss:: Information Loss
-* Mechanism:: Mechanism
+* Overview:: Overview
+* Invocation:: Invocation
+* Commands:: Command Language
+@ifset GENERIC
+* Machine Dependent:: Machine Dependent Features
+@end ifset
+@ifclear GENERIC
+@ifset H8300
+* H8/300:: ld and the H8/300
+@end ifset
+@ifset I960
+* i960:: ld and the Intel 960 family
+@end ifset
+@end ifclear
+@ifclear SingleFormat
+* BFD:: BFD
+@end ifclear
+@c Following blank line required for remaining bug in makeinfo conds/menus
+
+* MRI:: MRI Compatible Script Files
+* Index:: Index
@end menu
+@end ifinfo
-@node Overview, Invocation, Top, Top
+@node Overview
@chapter Overview
@cindex GNU linker
@cindex what is this?
-@code{gld} combines a number of object and archive files, relocates
-their data and ties up symbol references. Often the last step in
-building a new compiled program to run is a call to @code{gld}.
+@code{ld} combines a number of object and archive files, relocates
+their data and ties up symbol references. Usually the last step in
+compiling a program is to run @code{ld}.
-@code{gld} accepts Linker Command Language files written in
+@code{ld} accepts Linker Command Language files written in
a superset of AT&T's Link Editor Command Language syntax,
to provide explicit and total control over the linking process.
-This version of @code{gld} uses the general purpose BFD libraries
-to operate on object files. This allows @code{gld} to read, combine, and
+@ifclear SingleFormat
+This version of @code{ld} uses the general purpose BFD libraries
+to operate on object files. This allows @code{ld} to read, combine, and
write object files in many different formats---for example, COFF or
@code{a.out}. Different formats may be linked together to produce any
-available kind of object file. @xref{BFD} for a list of formats
-supported on various architectures.
+available kind of object file. @xref{BFD}, for more information.
+@end ifclear
Aside from its flexibility, the GNU linker is more helpful than other
linkers in providing diagnostic information. Many linkers abandon
execution immediately upon encountering an error; whenever possible,
-@code{gld} continues executing, allowing you to identify other errors
+@code{ld} continues executing, allowing you to identify other errors
(or, in some cases, to get an output file in spite of the error).
-@node Invocation, Commands, Overview, Top
+@node Invocation
@chapter Invocation
-The GNU linker @code{gld} is meant to cover a broad range of situations,
+The GNU linker @code{ld} is meant to cover a broad range of situations,
and to be as compatible as possible with other linkers. As a result,
-you have many choices to control its behavior through the command line,
-and through environment variables.
+you have many choices to control its behavior.
+@ifset UsesEnvVars
@menu
-* Options:: Command Line Options
-* Environment:: Environment Variables
+* Options:: Command Line Options
+* Environment:: Environment Variables
@end menu
-@node Options, Environment, Invocation, Invocation
+@node Options
@section Command Line Options
+@end ifset
@cindex command line
@cindex options
-Here is a sketch of the options you can use on the @code{gld} command
+Here is a summary of the options you can use on the @code{ld} command
line:
+@c FIXME! -relax only avail h8/300, i960. Conditionals screwed in examples.
@smallexample
-gld [-o @var{output} ] @var{objfiles}@dots{}
- [ -A@var{architecture} ] [ -b @var{input-format} ] [ -Bstatic ]
- [ -c @var{commandfile} ] [ -d | -dc | -dp ]
- [ -defsym @var{symbol} = @var{expression} ]
- [ -e @var{entry} ] [ -F ] [ -F @var{format} ]
- [ -format @var{input-format} ] [ -g ] [ -i ]
- [ -l@var{ar} ] [ -L@var{searchdir} ] [ -M | -m ]
- [ -n ] [ -noinhibit-exec ] [ -R @var{filename} ] [ -relax ]
- [ -r | -Ur ] [ -S ] [ -s ] [ -T @var{commandfile} ]
- [ -Ttext @var{textorg} ] [ -Tdata @var{dataorg} ] [ -Tbss @var{bssorg} ]
- [ -t ] [ -u @var{sym}] [-v] [ -X ] [ -x ]
- [ @{ @var{script} @} ]
+ld [ -o @var{output} ] @var{objfile}@dots{}
+ [ -A@var{architecture} ] [ -b @var{input-format} ] [ -Bstatic ]
+ [ -c @var{MRI-commandfile} ] [ -d | -dc | -dp ]
+ [ -defsym @var{symbol}=@var{expression} ]
+ [ -e @var{entry} ] [ -F ] [ -F @var{format} ]
+ [ -format @var{input-format} ] [ -g ] [ -G @var{size} ] [ -help ]
+ [ -i ] [ -l@var{archive} ] [ -L@var{searchdir} ] [ -M ]
+ [ -Map @var{mapfile} ] [ -m @var{emulation} ] [ -N | -n ]
+ [ -noinhibit-exec ] [ -oformat @var{output-format} ]
+ [ -R @var{filename} ] [ -relax ] [ -retain-symbols-file @var{filename} ]
+ [ -r | -Ur ] [ -S ] [ -s ] [ -sort-common ] [ -stats ]
+ [ -T @var{commandfile} ]
+ [ -Ttext @var{org} ] [ -Tdata @var{org} ]
+ [ -Tbss @var{org} ] [ -t ] [ -u @var{symbol}] [-V] [-v] [ -version ]
+ [ -warn-common ] [ -y @var{symbol} ] [ -X ] [-x ]
@end smallexample
This plethora of command-line options may seem intimidating, but in
actual practice few of them are used in any particular context.
@cindex standard Unix system
-For instance, a frequent use of @code{gld} is to link standard Unix
+For instance, a frequent use of @code{ld} is to link standard Unix
object files on a standard, supported Unix system. On such a system, to
link a file @code{hello.o}:
+
@example
-$ gld -o output /lib/crt0.o hello.o -lc
+ld -o @var{output} /lib/crt0.o hello.o -lc
@end example
-This tells @code{gld} to produce a file called @code{output} as the
+
+This tells @code{ld} to produce a file called @var{output} as the
result of linking the file @code{/lib/crt0.o} with @code{hello.o} and
-the library @code{libc.a} which will come from the standard search
-directories.
+the library @code{libc.a}, which will come from the standard search
+directories. (See the discussion of the @samp{-l} option below.)
-The command-line options to @code{gld} may be specified in any order, and
-may be repeated at will. For the most part, repeating an option with a
+The command-line options to @code{ld} may be specified in any order, and
+may be repeated at will. Repeating most options with a
different argument will either have no further effect, or override prior
-occurrences (those further to the left on the command line) of an
+occurrences (those further to the left on the command line) of that
option.
+@ifclear SingleFormat
+The exceptions---which may meaningfully be used more than once---are
+@samp{-A}, @samp{-b} (or its synonym @samp{-format}), @samp{-defsym},
+@samp{-L}, @samp{-l}, @samp{-R}, and @samp{-u}.
+@end ifclear
+@ifset SingleFormat
The exceptions---which may meaningfully be used more than once---are
-@code{-A}, @code{-b} (or its synonym @code{-format}), @code{-defsym},
-@code{-L}, @code{-l}, @code{-R}, and @code{-u}.
+@samp{-A}, @samp{-defsym}, @samp{-L}, @samp{-l}, @samp{-R}, and @samp{-u}.
+@end ifset
@cindex object files
-The list of object files to be linked together, shown as @var{objfiles},
-may follow, precede, or be mixed in with command-line options; save that
-an @var{objfiles} argument may not be placed between an option flag and
+The list of object files to be linked together, shown as @var{objfile}@dots{},
+may follow, precede, or be mixed in with command-line options, except that
+an @var{objfile} argument may not be placed between an option and
its argument.
-Usually the linker is invoked with at least one object file, but other
-forms of binary input files can also be specified with @code{-l},
-@code{-R}, and the script command language. If @emph{no} binary input
-files at all are specified, the linker does not produce any output, and
-issues the message @samp{No input files}.
+Usually the linker is invoked with at least one object file, but you can
+specify other forms of binary input files using @samp{-l}, @samp{-R},
+and the script command language. If @emph{no} binary input files at all
+are specified, the linker does not produce any output, and issues the
+message @samp{No input files}.
-Option arguments must either follow the option letter without intervening
+For options whose names are a single letter,
+option arguments must either follow the option letter without intervening
whitespace, or be given as separate arguments immediately following the
option that requires them.
-@table @code
-@item @var{objfiles}@dots{}
-The object files @var{objfiles} to be linked.
+For options whose names are multiple letters, either one dash or two can
+precede the option name; for example, @samp{--oformat} and
+@samp{-oformat} are equivalent. Arguments to multiple-letter options
+must either be separated from the option name by an equals sign, or be
+given as separate arguments immediately following the option that
+requires them. For example, @samp{--oformat srec} and
+@samp{--oformat=srec} are equivalent. Unique abbreviations of the names
+of multiple-letter options are accepted.
+@table @code
+@ifset I960
@cindex architectures
@kindex -A@var{arch}
@item -A@var{architecture}
-In the current release of @code{gld}, this option is useful only for the
-Intel 960 family of architectures. In that @code{gld} configuration, the
+In the current release of @code{ld}, this option is useful only for the
+Intel 960 family of architectures. In that @code{ld} configuration, the
@var{architecture} argument identifies the particular architecture in
the 960 family, enabling some safeguards and modifying the
-archive-library search path. @xref{i960-arch,,,Linking for a Specific
-i960 Architecture}, for details.
+archive-library search path. @xref{i960,,@code{ld} and the Intel 960
+family}, for details.
-Future releases of @code{gld} may support similar functionality for
+Future releases of @code{ld} may support similar functionality for
other architecture families.
+@end ifset
+@ifclear SingleFormat
@cindex binary input format
@kindex -b @var{format}
@cindex input format
@item -b @var{input-format}
@cindex input format
-Specify the binary format for input object files that follow this option
-on the command line. You don't usually need to specify this, as
-@code{gld} is configured to expect as a default input format the most
-usual format on each machine. @var{input-format} is a text string, the
-name of a particular format supported by the BFD libraries. @xref{BFD}.
-@code{-format @var{input-format}} has the same effect.@refill
+@code{ld} may be configured to support more than one kind of object
+file. If your @code{ld} is configured this way, you can use the
+@samp{-b} option to specify the binary format for input object files
+that follow this option on the command line. Even when @code{ld} is
+configured to support alternative object formats, you don't usually need
+to specify this, as @code{ld} should be configured to expect as a
+default input format the most usual format on each machine.
+@var{input-format} is a text string, the name of a particular format
+supported by the BFD libraries. (You can list the available binary
+formats with @samp{objdump -i}.) @w{@samp{-format @var{input-format}}}
+has the same effect, as does the script command @code{TARGET}.
+@xref{BFD}.
You may want to use this option if you are linking files with an unusual
-binary format. You can also use @code{-b} to switch formats explicitly (when
+binary format. You can also use @samp{-b} to switch formats explicitly (when
linking object files of different formats), by including
-@code{-b @var{input-format}} before each group of object files in a
+@samp{-b @var{input-format}} before each group of object files in a
particular format.
The default format is taken from the environment variable
-@code{GNUTARGET}. @xref{Environment}. You can also define the input
-format from a script, using the command @code{TARGET}.
+@code{GNUTARGET}.
+@ifset UsesEnvVars
+@xref{Environment}.
+@end ifset
+You can also define the input
+format from a script, using the command @code{TARGET}; see @ref{Option
+Commands}.
+@end ifclear
@kindex -Bstatic
@item -Bstatic
-This flag is accepted for command-line compatibility with the SunOS linker,
-but has no effect on @code{gld}.
-
-@kindex -c @var{cmdfile}
-@cindex script files
-@item -c @var{commandfile}
-Directs @code{gld} to read link commands from the file
-@var{commandfile}. These commands will completely override @code{gld}'s
-default link format (rather than adding to it); @var{commandfile} must
-specify everything necessary to describe the target format.
-@xref{Commands}.
-
-You may also include a script of link commands directly in the command
-line by bracketing it between @samp{@{} and @samp{@}} characters.
+Ignored. This option is accepted for command-line compatibility with
+the SunOS linker.
+
+@kindex -c @var{MRI-cmdfile}
+@cindex compatibility, MRI
+@item -c @var{MRI-commandfile}
+For compatibility with linkers produced by MRI, @code{ld} accepts script
+files written in an alternate, restricted command language, described in
+@ref{MRI,,MRI Compatible Script Files}. Introduce MRI script files with
+the option @samp{-c}; use the @samp{-T} option to run linker
+scripts written in the general-purpose @code{ld} scripting language.
+If @var{MRI-cmdfile} does not exist, @code{ld} looks for it in the directories
+specified by any @samp{-L} options.
@cindex common allocation
@kindex -d
@kindex -dp
@itemx -dp
These three options are equivalent; multiple forms are supported for
-compatibility with other linkers. Use any of them to make @code{ld}
+compatibility with other linkers. They
assign space to common symbols even if a relocatable output file is
-specified (@code{-r}). The script command
-@code{FORCE_COMMON_ALLOCATION} has the same effect.
+specified (with @samp{-r}). The script command
+@code{FORCE_COMMON_ALLOCATION} has the same effect. @xref{Option
+Commands}.
@cindex symbols, from command line
@kindex -defsym @var{symbol}=@var{exp}
-@item -defsym @var{symbol} = @var{expression}
+@item -defsym @var{symbol}=@var{expression}
Create a global symbol in the output file, containing the absolute
address given by @var{expression}. You may use this option as many
times as necessary to define multiple symbols in the command line. A
context: you may give a hexadecimal constant or the name of an existing
symbol, or use @code{+} and @code{-} to add or subtract hexadecimal
constants or symbols. If you need more elaborate expressions, consider
-using the linker command language from a script.
+using the linker command language from a script (@pxref{Assignment, ,
+Assignment: Symbol Definitions}). @emph{Note:} there should be no
+white space between @var{symbol}, the equals sign (``@key{=}''), and
+@var{expression}.
@cindex entry point, from command line
@kindex -e @var{entry}
discussion of defaults and other ways of specifying the
entry point.
-@ignore
-@cindex fill, from command line
-@kindex -f @var{fill}
-@c -f in older GNU linker, not in new
-@item -f @var{fill}
-Sets the default fill pattern for ``holes'' in the output file to
-the lowest two bytes of the expression specified. Holes are created
-when you advance the location counter (@xref{Location Counter}), or when
-there is a gap between explicitly specified section addresses
-(@xref{Section Options}).
-@end ignore
-
+@ifclear SingleFormat
@kindex -F
@item -F
@itemx -F@var{format}
-Some older linkers used this option throughout a compilation toolchain
-for specifying object-file format for both input and output object
-files. @code{gld}'s mechanisms (the @code{-b} or @code{-format} options
-for input files, the @code{TARGET} command in linker scripts for output
-files, the @code{GNUTARGET} environment variable) are more flexible, but
-but it accepts (and ignores) the @code{-F} option flag for compatibility
-with scripts written to call the old linker.
+Ignored. Some older linkers used this option throughout a compilation
+toolchain for specifying object-file format for both input and output
+object files. The mechanisms @code{ld} uses for this purpose (the
+@samp{-b} or @samp{-format} options for input files, @samp{-oformat}
+option or the @code{TARGET} command in linker scripts for output files,
+the @code{GNUTARGET} environment variable) are more flexible, but
+@code{ld} accepts the @samp{-F} option for compatibility with scripts
+written to call the old linker.
@kindex -format
@item -format @var{input-format}
-Synonym for @code{-b} @var{input-format}.
+Synonym for @samp{-b @var{input-format}}.
+@end ifclear
@kindex -g
@item -g
-Accepted, but ignored; provided for compatibility with other tools.
+Ignored. Provided for compatibility with other tools.
+
+@kindex -G
+@cindex object size
+@item -G@var{value}
+@itemx -G @var{value}
+Set the maximum size of objects to be optimized using the GP register to
+@var{size} under MIPS ECOFF. Ignored for other object file formats.
+
+@cindex help
+@cindex usage
+@kindex -help
+@item -help
+Print a summary of the command-line options on the standard output and exit.
@kindex -i
@cindex incremental link
@item -i
-Perform an incremental link (same as option @code{-r}).
+Perform an incremental link (same as option @samp{-r}).
@cindex archive files, from cmd line
-@kindex -l@var{ar}
+@kindex -l@var{archive}
@item -l@var{ar}
-Add an archive file @var{ar} to the list of files to link. This
+Add archive file @var{archive} to the list of files to link. This
option may be used any number of times. @code{ld} will search its
-path-list for occurrences of @code{lib@var{ar}.a} for every @var{ar}
+path-list for occurrences of @code{lib@var{ar}.a} for every @var{archive}
specified.
@cindex search directory, from cmd line
@kindex -L@var{dir}
@item -L@var{searchdir}
-This command adds path @var{searchdir} to the list of paths that
-@code{gld} will search for archive libraries. You may use this option
-any number of times.
+@itemx -L @var{searchdir}
+Add path @var{searchdir} to the list of paths that @code{ld} will search
+for archive libraries and @code{ld} control scripts. You may use this
+option any number of times.
+@ifset UsesEnvVars
The default set of paths searched (without being specified with
-@code{-L}) depends on what emulation mode @code{gld} is using, and in
-some cases also on how it was configured. @xref{Environment}. The
-paths can also be specified in a link script with the @code{SEARCH_DIR}
-command.
+@samp{-L}) depends on which emulation mode @code{ld} is using, and in
+some cases also on how it was configured. @xref{Environment}.
+@end ifset
+
+The paths can also be specified in a link script with the
+@code{SEARCH_DIR} command.
@cindex link map
@kindex -M
@item -M
-@kindex -m
-@itemx -m
-Print (to the standard output file) a link map---diagnostic information
+Print (to the standard output) a link map---diagnostic information
about where symbols are mapped by @code{ld}, and information on global
common storage allocation.
-@ignore
-@c -N in older GNU linker, not in new
+@cindex link map
+@kindex -Map
+@item -Map @var{mapfile}
+Print to the file @var{mapfile} a link map---diagnostic information
+about where symbols are mapped by @code{ld}, and information on global
+common storage allocation.
+
+@cindex emulation
+@kindex -m @var{emulation}
+@item -m@var{emulation}
+@itemx -m @var{emulation}
+Emulate the @var{emulation} linker. You can list the available
+emulations with the @samp{-V} option. The
+default depends on how your @code{ld} was configured.
+
@kindex -N
@cindex read/write from cmd line
@kindex OMAGIC
@item -N
-specifies readable and writable @code{text} and @code{data} sections. If
-the output format supports Unix style magic numbers, the output is
-marked as @code{OMAGIC}.
-@end ignore
+Set the text and data sections to be readable and writable. Also, do
+not page-align the data segment. If the output format supports Unix
+style magic numbers, mark the output as @code{OMAGIC}.
-@item -n
@kindex -n
@cindex read-only text
@kindex NMAGIC
-sets the text segment to be read only, and @code{NMAGIC} is written
-if possible.
+@item -n
+Set the text segment to be read only, and mark the output as
+@code{NMAGIC} if possible.
@item -noinhibit-exec
@cindex output file after errors
@kindex -noinhibit-exec
+Retain the executable output file whenever it is still usable.
Normally, the linker will not produce an output file if it encounters
-errors during the link process. With this flag, you can specify that
-you wish the output file retained even after non-fatal errors.
+errors during the link process; it exits without writing an output file
+when it issues any error whatsoever.
@item -o @var{output}
@kindex -o @var{output}
@cindex naming the output file
-@var{output} is a name for the program produced by @code{ld}; if this
-option is not specified, the name @samp{a.out} is used by default. The
+Use @var{output} as the name for the program produced by @code{ld}; if this
+option is not specified, the name @file{a.out} is used by default. The
script command @code{OUTPUT} can also specify the output file name.
+@ifclear SingleFormat
+@kindex -oformat
+@item -oformat @var{output-format}
+@code{ld} may be configured to support more than one kind of object
+file. If your @code{ld} is configured this way, you can use the
+@samp{-oformat} option to specify the binary format for the output
+object file. Even when @code{ld} is configured to support alternative
+object formats, you don't usually need to specify this, as @code{ld}
+should be configured to produce as a default output format the most
+usual format on each machine. @var{output-format} is a text string, the
+name of a particular format supported by the BFD libraries. (You can
+list the available binary formats with @samp{objdump -i}.) The script
+command @code{OUTPUT_FORMAT} can also specify the output format, but
+this option overrides it. @xref{BFD}.
+@end ifclear
+
@item -R @var{filename}
@kindex -R @var{file}
@cindex symbol-only input
relocate it or include it in the output. This allows your output file
to refer symbolically to absolute locations of memory defined in other
programs.
-
-@item -relax
+
@kindex -relax
@cindex synthesizing linker
@cindex relaxing addressing modes
-An option with machine dependent effects. Currently this option is only
-supported on the H8/300; see @ref{H8/300,,@code{gld} and the H8/300}.
-
-On some platforms, use this option to perform global optimizations that
-become possible when the linker resolves addressing in your program, such
+@item -relax
+An option with machine dependent effects.
+@ifset GENERIC
+Currently this option is only supported on the H8/300 and the Intel 960.
+@end ifset
+@ifset H8300
+@xref{H8/300,,@code{ld} and the H8/300}.
+@end ifset
+@ifset I960
+@xref{i960,, @code{ld} and the Intel 960 family}.
+@end ifset
+
+On some platforms, the @samp{-relax} option performs global optimizations that
+become possible when the linker resolves addressing in the program, such
as relaxing address modes and synthesizing new instructions in the
output object file.
+@ifset GENERIC
On platforms where this is not supported, @samp{-relax} is accepted, but
-has no effect.
+ignored.
+@end ifset
+
+@item -retain-symbols-file @var{filename}
+@cindex retaining specified symbols
+@cindex stripping all but some symbols
+@cindex symbols, retaining selectively
+Retain @emph{only} the symbols listed in the file @var{filename},
+discarding all others. @var{filename} is simply a flat file, with one
+symbol name per line. This option is especially useful in environments
+@ifset GENERIC
+(such as VxWorks)
+@end ifset
+where a large global symbol table is accumulated gradually, to conserve
+run-time memory.
+
+@samp{-retain-symbols-file} does @emph{not} discard undefined symbols,
+or symbols needed for relocations.
+
+You may only specify @samp{-retain-symbols-file} once in the command
+line. It overrides @samp{-s} and @samp{-S}.
-@item -r
@cindex partial link
@cindex relocatable output
@kindex -r
-Generates relocatable output---i.e., generate an output file that can in
-turn serve as input to @code{gld}. This is often called @dfn{partial
+@item -r
+Generate relocatable output---i.e., generate an output file that can in
+turn serve as input to @code{ld}. This is often called @dfn{partial
linking}. As a side effect, in environments that support standard Unix
magic numbers, this option also sets the output file's magic number to
@code{OMAGIC}.
@c ; see @code{-N}.
If this option is not specified, an absolute file is produced. When
linking C++ programs, this option @emph{will not} resolve references to
-constructors; @code{-Ur} is an alternative. @refill
+constructors; to do that, use @samp{-Ur}.
-This option does the same as @code{-i}.
+This option does the same thing as @samp{-i}.
-@item -S
@kindex -S
@cindex strip debugger symbols
-Omits debugger symbol information (but not all symbols) from the output file.
+@item -S
+Omit debugger symbol information (but not all symbols) from the output file.
-@item -s
@kindex -s
@cindex strip all symbols
-Omits all symbol information from the output file.
-
-@item @{ @var{script} @}
-@kindex @{ @var{script} @}
-@cindex scripts on command line
-You can, if you wish, include a script of linker commands directly in
-the command line instead of referring to it via an input file. When the
-character @samp{@{} occurs on the command line, the linker switches to
-interpreting the command language until the end of the list of commands
-is reached---flagged with a closing brace @samp{@}}. Other command-line
-options will not be recognized while parsing the script.
-@xref{Commands} for a description of the command language.
+@item -s
+Omit all symbol information from the output file.
+
+@item -sort-common
+Normally, when @code{ld} places the global common symbols in the
+appropriate output sections, it sorts them by size. First come all the
+one byte symbols, then all the two bytes, then all the four bytes, and
+then everything else. This is to prevent gaps between symbols due to
+alignment constraints. This option disables that sorting.
+
+@item -stats
+Compute and display statistics about the operation of the linker,
+such as execution time and memory usage.
@item -Tbss @var{org}
@kindex -Tbss @var{org}
@cindex segment origins, cmd line
Use @var{org} as the starting address for---respectively---the
@code{bss}, @code{data}, or the @code{text} segment of the output file.
-@var{textorg} must be a hexadecimal integer.
+@var{org} must be a single hexadecimal integer;
+for compatibility with other linkers, you may omit the leading
+@samp{0x} usually associated with hexadecimal values.
@item -T @var{commandfile}
@itemx -T@var{commandfile}
@kindex -T @var{script}
-Equivalent to @code{-c @var{commandfile}}; supported for compatibility with
-other tools.
+@cindex script files
+Read link commands from the file @var{commandfile}. These commands
+replace @code{ld}'s default link script (rather than adding
+to it), so @var{commandfile} must specify everything necessary to describe
+the target format. @xref{Commands}. If @var{commandfile} does not
+exist, @code{ld} looks for it in the directories specified by any
+preceding @samp{-L} options. Multiple @samp{-T} options accumulate.
-@item -t
@kindex -t
@cindex verbose
@cindex input files, displaying
-Prints names of input files as @code{ld} processes them.
+@item -t
+Print the names of the input files as @code{ld} processes them.
-@item -u @var{sym}
-@kindex -u @var{sym}
+@item -u @var{symbol}
+@kindex -u @var{symbol}
@cindex undefined symbol
-Forces @var{sym} to be entered in the output file as an undefined symbol.
-This may, for example, trigger linking of additional modules from
-standard libraries. @code{-u} may be repeated with different option
+Force @var{symbol} to be entered in the output file as an undefined symbol.
+Doing this may, for example, trigger linking of additional modules from
+standard libraries. @samp{-u} may be repeated with different option
arguments to enter additional undefined symbols.
@c Nice idea, but no such command: This option is equivalent
@c to the @code{EXTERN} linker command.
-@item -Ur
@kindex -Ur
@cindex constructors
+@item -Ur
For anything other than C++ programs, this option is equivalent to
-@code{-r}: it generates relocatable output---i.e., an output file that can in
-turn serve as input to @code{gld}. When linking C++ programs, @code{-Ur}
-@emph{will} resolve references to constructors, unlike @code{-r}.
+@samp{-r}: it generates relocatable output---i.e., an output file that can in
+turn serve as input to @code{ld}. When linking C++ programs, @samp{-Ur}
+@emph{does} resolve references to constructors, unlike @samp{-r}.
+It does not work to use @samp{-Ur} on files that were themselves linked
+with @samp{-Ur}; once the constructor table has been built, it cannot
+be added to. Use @samp{-Ur} only for the last partial link, and
+@samp{-r} for the others.
+
+@kindex -V
+@cindex version
+@item -V
+Display the version number for @code{ld} and list the linker emulations
+supported. Display which input files can and cannot be opened.
-@item -v
@kindex -v
@cindex version
-Display the version number for @code{gld}.
+@item -v
+Display the version number for @code{ld}.
+
+@item -version
+@kindex -version
+Display the version number for @code{ld} and exit.
+
+@item -warn-common
+@kindex -warn-comon
+@cindex warnings, on combining symbols
+@cindex combining symbols, warnings on
+Warn when a common symbol is combined with another common symbol or with
+a symbol definition. Unix linkers allow this somewhat sloppy practice,
+but linkers on some other operating systems do not. This option allows
+you to find potential problems from combining global symbols.
+Unfortunately, some C libraries use this practice, so you may get some
+warnings about symbols in the libraries as well as in your programs.
+
+There are three kinds of global symbols, illustrated here by C examples:
+
+@table @samp
+@item int i = 1;
+A definition, which goes in the initialized data section of the output
+file.
+
+@item extern int i;
+An undefined reference, which does not allocate space.
+There must be either a definition or a common symbol for the
+variable somewhere.
+
+@item int i;
+A common symbol. If there are only (one or more) common symbols for a
+variable, it goes in the uninitialized data area of the output file.
+The linker merges multiple common symbols for the same variable into a
+single symbol. If they are of different sizes, it picks the largest
+size. The linker turns a common symbol into a declaration, if there is
+a definition of the same variable.
+@end table
+
+The @samp{-warn-common} option can produce five kinds of warnings. Each
+warning consists of a pair of lines: the first describes the symbol just
+encountered, and the second describes the previous symbol encountered
+with the same name. One or both of the two symbols will be a common
+symbol.
+
+@enumerate
+@item
+Turning a common symbol into a reference, because there is already a
+definition for the symbol.
+@smallexample
+@var{file}(@var{section}): warning: common of `@var{symbol}'
+ overridden by definition
+@var{file}(@var{section}): warning: defined here
+@end smallexample
+
+@item
+Turning a common symbol into a reference, because a later definition for
+the symbol is encountered. This is the same as the previous case,
+except that the symbols are encountered in a different order.
+@smallexample
+@var{file}(@var{section}): warning: definition of `@var{symbol}'
+ overriding common
+@var{file}(@var{section}): warning: common is here
+@end smallexample
+
+@item
+Merging a common symbol with a previous same-sized common symbol.
+@smallexample
+@var{file}(@var{section}): warning: multiple common
+ of `@var{symbol}'
+@var{file}(@var{section}): warning: previous common is here
+@end smallexample
+
+@item
+Merging a common symbol with a previous larger common symbol.
+@smallexample
+@var{file}(@var{section}): warning: common of `@var{symbol}'
+ overridden by larger common
+@var{file}(@var{section}): warning: larger common is here
+@end smallexample
+
+@item
+Merging a common symbol with a previous smaller common symbol. This is
+the same as the previous case, except that the symbols are
+encountered in a different order.
+@smallexample
+@var{file}(@var{section}): warning: common of `@var{symbol}'
+ overriding smaller common
+@var{file}(@var{section}): warning: smaller common is here
+@end smallexample
+@end enumerate
-@item -X
@kindex -X
@cindex local symbols, deleting
@cindex L, deleting symbols beginning
-If @code{-s} or @code{-S} is also specified, delete only local symbols
+@item -X
+If @samp{-s} or @samp{-S} is also specified, delete only local symbols
beginning with @samp{L}.
-@item -x
@kindex -x
@cindex deleting local symbols
-If @code{-s} or @code{-S} is also specified, delete all local symbols,
+@item -x
+If @samp{-s} or @samp{-S} is also specified, delete all local symbols,
not just those beginning with @samp{L}.
-@ignore
-@c -z in older GNU linker, not in new
-@item -z
-@kindex -z
-@cindex read-only text
-Specifies a read-only, demand pageable, and shared @code{text} segment.
-If the output format supports Unix-style magic numbers, @code{-z} also
-marks the output as @code{ZMAGIC}, the default.
-
-@c why was following here?. Is it useful to say '-z -r' for
-@c instance, or is this just a ref to other ways of setting
-@c magic no?
-Specifying a relocatable output file (@code{-r}) will also set the magic
-number to @code{OMAGIC}.
-
-See description of @code{-N}.
-@end ignore
+@item -y @var{symbol}
+@kindex -y @var{symbol}
+@cindex symbol tracing
+Print the name of each linked file in which @var{symbol} appears. This
+option may be given any number of times. On many systems it is necessary
+to prepend an underscore.
+This option is useful when you have an undefined symbol in your link but
+don't know where the reference is coming from.
@end table
-@node Environment, , Options, Invocation
+@ifset UsesEnvVars
+@node Environment
@section Environment Variables
-You can condition the behavior of @code{gld} with two environment
-variables: @code{GNUTARGET} and @code{LDEMULATION}. Depending on the
-setting of the latter, other environment variables may be used as well.
+You can change the behavior of @code{ld} with the environment
+variable @code{GNUTARGET}.
@kindex GNUTARGET
@cindex default input format
@code{GNUTARGET} determines the input-file object format if you don't
-use @code{-b} (or its synonym @code{-format}). Its value should be one
+use @samp{-b} (or its synonym @samp{-format}). Its value should be one
of the BFD names for an input format (@pxref{BFD}). If there is no
-@code{GNUTARGET} in the environment, @code{gld} uses the natural format
-of the host. If @code{GNUTARGET} is set to @code{default} then BFD attempts to discover the
+@code{GNUTARGET} in the environment, @code{ld} uses the natural format
+of the target. If @code{GNUTARGET} is set to @code{default} then BFD attempts to discover the
input format by examining binary input files; this method often
succeeds, but there are potential ambiguities, since there is no method
-of ensuring that the magic number used to flag object-file formats is
+of ensuring that the magic number used to specify object-file formats is
unique. However, the configuration procedure for BFD on each system
places the conventional format for that system first in the search-list,
so ambiguities are resolved in favor of convention.
+@end ifset
-@kindex LDEMULATION
-@cindex emulation
-@cindex environment vars
-@code{LDEMULATION} controls some aspects of @code{gld}'s dominant
-personality. Although @code{gld} is flexible enough to permit its use
-in many contexts regardless of configuration, you can use this variable
-to make it act more like one or another older linker by default.
-
-@cindex defaults
-@cindex library paths, default
-In particular, the value of @code{LDEMULATION} controls what default
-linker script is used (thereby controlling the default input and output
-formats; @pxref{BFD}); what default paths are searched for
-archive libraries; and in some cases whether additional linker script
-commands are available.
-
-Here is the current set of emulations available:
-@table @code
-
-@item LDEMULATION=gld
-@kindex gld
-@cindex emulating old GNU linker
-Emulate the older GNU linker. When this emulation is selected, the
-default library search paths are
-@example
-/lib
-/usr/lib
-/usr/local/lib/lib
-@end example
-@noindent
-The default output format is set to @code{a.out-generic-big}, and the
-default machine is the system's configured BFD default.
-
-@item LDEMULATION=gld68k
-@kindex gld68k
-@cindex m68k
-A variant of the @code{gld} emulation; only differs in specifically
-setting the default BFD machine as @code{m68k}.
-
-@item LDEMULATION=gld960
-@itemx LDEMULATION=lnk960
-Emulate older linkers for the i960 family; see @ref{i960,,@code{gld} and
-the Intel 960 family}, for details.
-
-@item LDEMULATION=gldm88kbcs
-Configure the linker for the Motorola 88K family.
-@xref{m88k,,@code{gld} and the Motorola 880x0 family}, for details.
-
-@item LDEMULATION=vanilla
-@kindex vanilla
-@cindex emulation, disabling
-@cindex disabling emulation
-This is the least specific setting for @code{gld}. You can set
-@code{LDEMULATION=vanilla} to disable emulation of other linkers. This
-setting makes @code{gld} take the default machine from the BFD
-configuration on your system; @code{a.out-generic-big} is the default
-target. No other defaults are specified.
-@end table
-
-@node Commands, Machine Dependent, Invocation, Top
+@node Commands
@chapter Command Language
@cindex command files
-The command language allows explicit control over the link process,
+The command language provides explicit control over the link process,
allowing complete specification of the mapping between the linker's
-input files and its output. This includes:
+input files and its output. It controls:
@itemize @bullet
@item
input files
@item
file formats
@item
-output file format
+output file layout
@item
addresses of sections
@item
@end itemize
You may supply a command file (also known as a link script) to the
-linker either explicitly through the @code{-c} option, or implicitly as
+linker either explicitly through the @samp{-T} option, or implicitly as
an ordinary file. If the linker opens a file which it cannot recognize
-as a supported object or archive format, it tries to interpret the file
-as a command file.
-
-You can also include a script directly on the @code{gld} command line,
-delimited by the characters @samp{@{} and @samp{@}}.
+as a supported object or archive format, it reports an error.
@menu
-* Scripts:: Linker Scripts
-* Expressions:: Expressions
-* MEMORY:: MEMORY Command
-* SECTIONS:: SECTIONS Command
-* Entry Point:: The Entry Point
-* Other Commands:: Other Commands
+* Scripts:: Linker Scripts
+* Expressions:: Expressions
+* MEMORY:: MEMORY Command
+* SECTIONS:: SECTIONS Command
+* Entry Point:: The Entry Point
+* Option Commands:: Option Commands
@end menu
-@node Scripts, Expressions, Commands, Commands
+@node Scripts
@section Linker Scripts
-The @code{gld} command language is a collection of statements; some are
-simple keywords setting a particular flag, some are used to select and
-group input files or name output files; and two particular statement
+The @code{ld} command language is a collection of statements; some are
+simple keywords setting a particular option, some are used to select and
+group input files or name output files; and two statement
types have a fundamental and pervasive impact on the linking process.
@cindex fundamental script commands
@cindex commands, fundamental
@cindex output file layout
@cindex layout of output file
-The most fundamental command of the @code{gld} command language is the
+The most fundamental command of the @code{ld} command language is the
@code{SECTIONS} command (@pxref{SECTIONS}). Every meaningful command
script must have a @code{SECTIONS} command: it specifies a
``picture'' of the output file's layout, in varying degrees of detail.
The @code{MEMORY} command complements @code{SECTIONS} by describing the
available memory in the target architecture. This command is optional;
-if you don't use a @code{MEMORY} command, @code{gld} assumes sufficient
+if you don't use a @code{MEMORY} command, @code{ld} assumes sufficient
memory is available in a contiguous block for all output.
@xref{MEMORY}.
by @samp{/*} and @samp{*/}. As in C, comments are syntactically
equivalent to whitespace.
-@node Expressions, MEMORY, Scripts, Commands
+@node Expressions
@section Expressions
@cindex expression syntax
@cindex arithmetic
@end itemize
@menu
-* Integers:: Integers
-* Symbols:: Symbol Names
-* Location Counter:: The Location Counter
-* Operators:: Operators
-* Evaluation:: Evaluation
-* Assignment:: Assignment: Defining Symbols
-* Built-ins:: Built-In Functions
+* Integers:: Integers
+* Symbols:: Symbol Names
+* Location Counter:: The Location Counter
+* Operators:: Operators
+* Evaluation:: Evaluation
+* Assignment:: Assignment: Defining Symbols
+* Arithmetic Functions:: Built-In Functions
@end menu
-@node Integers, Symbols, Expressions, Expressions
+@node Integers
@subsection Integers
@cindex integer notation
@cindex octal integers
@end example
@cindex negative integers
-Decimal integers have the usual values. To write a negative integer, use
+To write a negative integer, use
the prefix operator @samp{-}; @pxref{Operators}.
@example
_as_neg = -57005;
${\rm 1024}$ or ${\rm 1024}^2$
@end tex
@c END TEXI2ROFF-KILL
-respectively. For example, the following all refer to the same quantity:@refill
+respectively. For example, the following all refer to the same quantity:
@example
_fourk_1 = 4K;
_fourk_3 = 0x1000;
@end example
-@node Symbols, Location Counter, Integers, Expressions
+@node Symbols
@subsection Symbol Names
@cindex symbol names
@cindex names
@cindex quoted symbol names
@kindex "
-Unless quoted, symbol names start with a letter, underscore, point or
-hyphen and may include any letters, underscores, digits, points,
-and minus signs. Unquoted symbol names must not conflict with any
+Unless quoted, symbol names start with a letter, underscore, or point
+and may include any letters, underscores, digits, points,
+and hyphens. Unquoted symbol names must not conflict with any
keywords. You can specify a symbol which contains odd characters or has
the same name as a keyword, by surrounding the symbol name in double quotes:
@example
"with a space" = "also with a space" + 10;
@end example
-@node Location Counter, Operators, Symbols, Expressions
+Since symbols can contain many non-alphabetic characters, it is safest
+to delimit symbols with spaces. For example, @samp{A-B} is one symbol,
+whereas @samp{A - B} is an expression involving subtraction.
+
+@node Location Counter
@subsection The Location Counter
@kindex .
@cindex dot
@example
SECTIONS
@{
- output :
- @{
- file1(.text)
- . = . + 1000;
- file2(.text)
- . += 1000;
- file3(.text)
- @} = 0x1234;
+ output :
+ @{
+ file1(.text)
+ . = . + 1000;
+ file2(.text)
+ . += 1000;
+ file3(.text)
+ @} = 0x1234;
@}
@end example
@noindent
loaded. The notation @samp{= 0x1234} specifies what data to write in
the gaps (@pxref{Section Options}).
-@node Operators, Evaluation, Location Counter, Expressions
+@iftex
+@vfill
+@end iftex
+
+@need 5000
+@node Operators
@subsection Operators
@cindex Operators for arithmetic
@cindex arithmetic operators
@end iftex
@c END TEXI2ROFF-KILL
-@node Evaluation, Assignment, Operators, Expressions
+@node Evaluation
@subsection Evaluation
@cindex lazy evaluation
output sections) is available for use in the symbol assignment
expression.
-@node Assignment, Built-ins, Evaluation, Expressions
+@node Assignment
@subsection Assignment: Defining Symbols
@cindex assignment in scripts
@cindex symbol definition, scripts
@itemx @var{symbol} /= @var{expression} ;
@end table
-Two things distinguish assignment from other operators in @code{gld}
+Two things distinguish assignment from other operators in @code{ld}
expressions.
@itemize @bullet
@item
@kindex ;
@cindex semicolon
@item
-A trailing semicolon is required at the end of an assignment
-statement.
+You must place a trailing semicolon (``@key{;}'') at the end of an
+assignment statement.
@end itemize
Assignment statements may appear:
@itemize @bullet
@item
-as commands in their own right in a @code{gld} script; or
+as commands in their own right in an @code{ld} script; or
@item
as independent statements within a @code{SECTIONS} command; or
@item
@end itemize
The first two cases are equivalent in effect---both define a symbol with
-an absolute address; the last case defines a symbol whose address is
+an absolute address. The last case defines a symbol whose address is
relative to a particular section (@pxref{SECTIONS}).
@cindex absolute and relocatable symbols
When a linker expression is evaluated and assigned to a variable, it is
given either an absolute or a relocatable type. An absolute expression
type is one in which the symbol contains the value that it will have in
-the output file, a relocateable expression type is one in which the
+the output file; a relocatable expression type is one in which the
value is expressed as a fixed offset from the base of a section.
The type of the expression is controlled by its position in the script
is the last byte of an output section named @code{.data}:
@example
SECTIONS@{ @dots{}
-.data :
- @{
- *(.data)
- _edata = ABSOLUTE(.) ;
- @}
+ .data :
+ @{
+ *(.data)
+ _edata = ABSOLUTE(.) ;
+ @}
@dots{} @}
@end example
The linker tries to put off the evaluation of an assignment until all
the terms in the source expression are known (@pxref{Evaluation}). For
-instance the sizes of sections cannot be known until after allocation,
+instance, the sizes of sections cannot be known until after allocation,
so assignments dependent upon these are not performed until after
allocation. Some expressions, such as those depending upon the location
counter @dfn{dot}, @samp{.} must be evaluated during allocation. If the
then an error results. For example, a script like the following
@example
SECTIONS @{ @dots{}
- text 9+this_isnt_constant:
- @{ @dots{}
- @}
+ text 9+this_isnt_constant :
+ @{ @dots{}
+ @}
@dots{} @}
@end example
@kindex Non constant expression
will cause the error message ``@code{Non constant expression for initial
address}''.
-@node Built-ins, , Assignment, Expressions
-@subsection Built-In Functions
+@node Arithmetic Functions
+@subsection Arithmetic Functions
@cindex functions in expression language
-The command language includes a number of special purpose built-in
+The command language includes a number of built-in
functions for use in link script expressions.
@table @code
@item ABSOLUTE(@var{exp})
@kindex ABSOLUTE(@var{exp})
@cindex expression, absolute
-returns the absolute value of the expression @var{exp}. Primarily
-useful to assign an absolute value to a symbol within a section
-definition, where symbol values are normally section-relative.
+Return the absolute (non-relocatable, as opposed to non-negative) value
+of the expression @var{exp}. Primarily useful to assign an absolute
+value to a symbol within a section definition, where symbol values are
+normally section-relative.
@item ADDR(@var{section})
@kindex ADDR(@var{section})
@cindex section address
-returns the absolute address of the named @var{section}. Your script must
+Return the absolute address of the named @var{section}. Your script must
previously have defined the location of that section. In the following
-example the @code{symbol_1} and @code{symbol_2} are assigned identical
+example, @code{symbol_1} and @code{symbol_2} are assigned identical
values:
@example
SECTIONS@{ @dots{}
- .output1:
- @{
- start_of_output_1 = ABSOLUTE(.);
- @dots{}
- @}
- .output:
- @{
- symbol_1 = ADDR(.output1);
- symbol_2 = start_of_output_1;
- @}
+ .output1 :
+ @{
+ start_of_output_1 = ABSOLUTE(.);
+ @dots{}
+ @}
+ .output :
+ @{
+ symbol_1 = ADDR(.output1);
+ symbol_2 = start_of_output_1;
+ @}
@dots{} @}
@end example
@item ALIGN(@var{exp})
@kindex ALIGN(@var{exp})
@cindex rounding up location counter
-returns the result of the current location counter (@code{.}) aligned to
+Return the result of the current location counter (@code{.}) aligned to
the next @var{exp} boundary. @var{exp} must be an expression whose
value is a power of two. This is equivalent to
@example
-(. + @var{exp} -1) & ~(@var{exp}-1)
+(. + @var{exp} - 1) & ~(@var{exp} - 1)
@end example
@code{ALIGN} doesn't change the value of the location counter---it just
@code{0x8000} boundary after the input sections:
@example
SECTIONS@{ @dots{}
- .data ALIGN(0x2000): @{
- *(.data)
- variable = ALIGN(0x8000);
- @}
+ .data ALIGN(0x2000): @{
+ *(.data)
+ variable = ALIGN(0x8000);
+ @}
@dots{} @}
@end example
@noindent
@item DEFINED(@var{symbol})
@kindex DEFINED(@var{symbol})
@cindex symbol defaults
-Returns @code{1} if @var{symbol} is in the linker global symbol table and is
-defined, otherwise it returns @code{0}. You can use this to provide default
-values for symbols. For example, this command-file fragment shows how
+Return 1 if @var{symbol} is in the linker global symbol table and is
+defined, otherwise return 0. You can use this function to provide default
+values for symbols. For example, the following command-file fragment shows how
to set a global symbol @code{begin} to the first location in the
@code{.text} section---but if a symbol called @code{begin} already
existed, its value is preserved:
+
@smallexample
SECTIONS@{ @dots{}
- .text: @{
- begin = DEFINED(begin) ? begin : . ;
- @dots{}
- @}
+ .text : @{
+ begin = DEFINED(begin) ? begin : . ;
+ @dots{}
+ @}
@dots{} @}
@end smallexample
@item NEXT(@var{exp})
@kindex NEXT(@var{exp})
@cindex unallocated address, next
-Returns the next unallocated address that is a multiple of @var{exp}.
-This command is closely related to @code{ALIGN(@var{exp})}; unless you
+Return the next unallocated address that is a multiple of @var{exp}.
+This function is closely related to @code{ALIGN(@var{exp})}; unless you
use the @code{MEMORY} command to define discontinuous memory for the
-output file, the two commands are equivalent.
+output file, the two functions are equivalent.
@item SIZEOF(@var{section})
@kindex SIZEOF(@var{section})
@cindex section size
-returns the size in bytes of the named @var{section}, if the section has
-been allocated. In the following example the @code{symbol_1} and
+Return the size in bytes of the named @var{section}, if that section has
+been allocated. In the following example, @code{symbol_1} and
@code{symbol_2} are assigned identical values:
+@c What does it return if the section hasn't been allocated? 0?
@example
SECTIONS@{ @dots{}
- .output @{
- .start = . ;
- @dots{}
- .end = .;
- @}
- symbol_1 = .end - .start;
- symbol_2 = SIZEOF(.output);
+ .output @{
+ .start = . ;
+ @dots{}
+ .end = . ;
+ @}
+ symbol_1 = .end - .start ;
+ symbol_2 = SIZEOF(.output);
@dots{} @}
@end example
@cindex header size
@itemx sizeof_headers
@kindex sizeof_headers
-the size in bytes of the output file's headers. You can use this number
+Return the size in bytes of the output file's headers. You can use this number
as the start address of the first section, if you choose, to facilitate
paging.
@end table
-@node MEMORY, SECTIONS, Expressions, Commands
-@section MEMORY Command
+@node MEMORY
+@section Memory Layout
@kindex MEMORY
@cindex regions of memory
@cindex discontinuous memory
@cindex allocating memory
-The linker's default configuration permits allocation of all memory.
-You can override this by using the @code{MEMORY} command. The
+The linker's default configuration permits allocation of all available memory.
+You can override this configuration by using the @code{MEMORY} command. The
@code{MEMORY} command describes the location and size of blocks of
memory in the target. By using it carefully, you can describe which
memory regions may be used by the linker, and which memory regions it
available regions, but does move the requested sections into the correct
regions and issue errors when the regions become too full.
-Command files may contain at most one use of the @code{MEMORY}
+A command file may contain at most one use of the @code{MEMORY}
command; however, you can define as many blocks of memory within it as
you wish. The syntax is:
@example
MEMORY
- @{
- @var{name} (@var{attr}): ORIGIN = @var{origin}, LENGTH = @var{len}
- @dots{}
- @}
+ @{
+ @var{name} (@var{attr}) : ORIGIN = @var{origin}, LENGTH = @var{len}
+ @dots{}
+ @}
@end example
@table @code
-@item @var{name}
@cindex naming memory regions
+@item @var{name}
is a name used internally by the linker to refer to the region. Any
symbol name may be used. The region names are stored in a separate
-name space, and will not conflict with symbols, filenames or section
+name space, and will not conflict with symbols, file names or section
names. Use distinct names to specify multiple regions.
-@item (@var{attr})
+
@cindex memory region attributes
+@item (@var{attr})
is an optional list of attributes, permitted for compatibility with the
-AT&T linker but not used by @code{gld} beyond checking that the
+AT&T linker but not used by @code{ld} beyond checking that the
attribute list is valid. Valid attribute lists must be made up of the
characters ``@code{LIRWX}''. If you omit the attribute list, you may
omit the parentheses around it as well.
+
+@kindex ORIGIN =
+@kindex o =
+@kindex org =
@item @var{origin}
-@kindex ORIGIN=
-@kindex o=
-@kindex org=
-is the start address of the region in physical memory. It is expressed as
-an expression, which must evaluate to a constant before
+is the start address of the region in physical memory. It is
+an expression that must evaluate to a constant before
memory allocation is performed. The keyword @code{ORIGIN} may be
-abbreviated to @code{org} or @code{o}.
+abbreviated to @code{org} or @code{o} (but not, for example, @samp{ORG}).
+
+@kindex LENGTH =
+@kindex len =
+@kindex l =
@item @var{len}
-@kindex LENGTH=
-@kindex len=
-@kindex l=
is the size in bytes of the region (an expression).
The keyword @code{LENGTH} may be abbreviated to @code{len} or @code{l}.
@end table
For example, to specify that memory has two regions available for
-allocation---one starting at @code{0} for 256 kilobytes, and the other
+allocation---one starting at 0 for 256 kilobytes, and the other
starting at @code{0x40000000} for four megabytes:
@example
MEMORY
- @{
- rom : ORIGIN= 0, LENGTH = 256K
- ram : org= 0x40000000, l = 4M
- @}
+ @{
+ rom : ORIGIN = 0, LENGTH = 256K
+ ram : org = 0x40000000, l = 4M
+ @}
@end example
Once you have defined a region of memory named @var{mem}, you can direct
Options}). If the combined output sections directed to a region are too
big for the region, the linker will issue an error message.
-@node SECTIONS, Entry Point, MEMORY, Commands
-@section SECTIONS Command
+@node SECTIONS
+@section Specifying Output Sections
+
@kindex SECTIONS
The @code{SECTIONS} command controls exactly where input sections are
-placed into output sections, their order and to which output sections
-they are allocated.
+placed into output sections, their order in the output file, and to
+which output sections they are allocated.
-You may use at most one @code{SECTIONS} command in a commands file,
+You may use at most one @code{SECTIONS} command in a script file,
but you can have as many statements within it as you wish. Statements
within the @code{SECTIONS} command can do one of three things:
+
@itemize @bullet
@item
define the entry point;
+
@item
assign a value to a symbol;
+
@item
-describe the placement of a named output section, and what input
-sections make it up.
+describe the placement of a named output section, and which input
+sections go into it.
@end itemize
-The first two possibilities---defining the entry point, and defining
-symbols---can also be done outside the @code{SECTIONS} command:
-@pxref{Entry Point}, @pxref{Assignment}. They are permitted here as
-well for your convenience in reading the script, so that symbols or the
-entry point can be defined at meaningful points in your output-file
-layout.
+You can also use the first two operations---defining the entry point and
+defining symbols---outside the @code{SECTIONS} command: @pxref{Entry
+Point}, and @pxref{Assignment}. They are permitted here as well for
+your convenience in reading the script, so that symbols and the entry
+point can be defined at meaningful points in your output-file layout.
-When no @code{SECTIONS} command is specified, the default action
-of the linker is to place each input section into an identically named
-output section in the order that the sections are first encountered in
-the input files; if all input sections are present in the first file,
-for example, the order of sections in the output file will match the
-order in the first input file.
+If you do not use a @code{SECTIONS} command, the linker places each input
+section into an identically named output section in the order that the
+sections are first encountered in the input files. If all input sections
+are present in the first file, for example, the order of sections in the
+output file will match the order in the first input file.
@menu
-* Section Definition:: Section Definitions
-* Section Contents:: Section Contents
-* Section Options:: Optional Section Attributes
+* Section Definition:: Section Definitions
+* Section Placement:: Section Placement
+* Section Data Expressions:: Section Data Expressions
+* Section Options:: Optional Section Attributes
@end menu
-@node Section Definition, Section Contents, SECTIONS, SECTIONS
+@node Section Definition
@subsection Section Definitions
@cindex section definition
The most frequently used statement in the @code{SECTIONS} command is
-the @dfn{section definition}, which you can use to specify the
+the @dfn{section definition}, which specifies the
properties of an output section: its location, alignment, contents,
-fill pattern, and target memory region can all be specified. Most of
+fill pattern, and target memory region. Most of
these specifications are optional; the simplest form of a section
definition is
@example
SECTIONS @{ @dots{}
-@var{secname} : @{
- @var{contents}
- @}
+ @var{secname} : @{
+ @var{contents}
+ @}
@dots{} @}
@end example
@cindex naming output sections
@noindent
@var{secname} is the name of the output section, and @var{contents} a
-specification of what goes there---for example a list of input files or
-sections of input files. As you might assume, the whitespace shown is
-optional; you do need the colon @samp{:} and the braces @samp{@{@}},
-however.
+specification of what goes there---for example, a list of input files or
+sections of input files (@pxref{Section Placement}). As you might
+assume, the whitespace shown is optional. You do need the colon
+@samp{:} and the braces @samp{@{@}}, however.
@var{secname} must meet the constraints of your output format. In
formats which only support a limited number of sections, such as
@code{.bss}). If the output format supports any number of sections, but
with numbers and not names (as is the case for Oasys), the name should be
supplied as a quoted numeric string. A section name may consist of any
-sequence characters, but any name which does not conform to the standard
-@code{gld} symbol name syntax must be quoted.
+sequence of characters, but any name which does not conform to the standard
+@code{ld} symbol name syntax must be quoted.
+@xref{Symbols, , Symbol Names}.
+
+@node Section Placement
+@subsection Section Placement
-@node Section Contents, Section Options, Section Definition, SECTIONS
-@subsection Section Contents
@cindex contents of a section
-In a section definition, you can specify the contents of an output section by
-listing particular object files; by listing particular input-file
-sections; or a combination of the two. You can also place arbitrary
-data in the section, and define symbols relative to the beginning of the
-section.
+In a section definition, you can specify the contents of an output
+section by listing particular input files, by listing particular
+input-file sections, or by a combination of the two. You can also place
+arbitrary data in the section, and define symbols relative to the
+beginning of the section.
The @var{contents} of a section definition may include any of the
following kinds of statement. You can include as many of these as you
whitespace.
@table @code
-@item @var{filename}
@kindex @var{filename}
@cindex input files, section defn
@cindex files, including in output sections
+@item @var{filename}
You may simply name a particular input file to be placed in the current
output section; @emph{all} sections from that file are placed in the
-current section definition. To specify a list of particular files by
-name:
+current section definition. If the file name has already been mentioned
+in another section definition, with an explicit section name list, then
+only those sections which have not yet been allocated are used.
+
+To specify a list of particular files by name:
@example
-.data: @{ afile.o bfile.o cfile.o @}
+.data : @{ afile.o bfile.o cfile.o @}
@end example
@noindent
The example also illustrates that multiple statements can be included in
-the contents of a section definition, since each filename is a separate
+the contents of a section definition, since each file name is a separate
statement.
-If the file name has already been mentioned in another section
-definition, with an explicit section name list, then only those sections
-which have not yet been allocated are used.
-
+@kindex @var{filename}(@var{section})
+@cindex files and sections, section defn
@item @var{filename}( @var{section} )
@itemx @var{filename}( @var{section}, @var{section}, @dots{} )
@itemx @var{filename}( @var{section} @var{section} @dots{} )
-@kindex @var{filename}(@var{section})
-@cindex files and sections, section defn
You can name one or more sections from your input files, for
insertion in the current output section. If you wish to specify a list
of input-file sections inside the parentheses, you may separate the
section names by either commas or whitespace.
-@item * (@var{section})
-@itemx * (@var{section}, @var{section}, @dots{})
-@itemx * (@var{section} @var{section} @dots{}
@cindex input sections to output section
@kindex *(@var{section})
+@item * (@var{section})
+@itemx * (@var{section}, @var{section}, @dots{})
+@itemx * (@var{section} @var{section} @dots{})
Instead of explicitly naming particular input files in a link control
-script, you can refer to @emph{all} files from the @code{gld} command
-line: use @samp{*} instead of a particular filename before the
+script, you can refer to @emph{all} files from the @code{ld} command
+line: use @samp{*} instead of a particular file name before the
parenthesized input-file section list.
-For example, to copy sections @code{1} through @code{4} from a Oasys file
+If you have already explicitly included some files by name, @samp{*}
+refers to all @emph{remaining} files---those whose places in the output
+file have not yet been defined.
+
+For example, to copy sections @code{1} through @code{4} from an Oasys file
into the @code{.text} section of an @code{a.out} file, and sections @code{13}
and @code{14} into the @code{.data} section:
@example
SECTIONS @{
- .text :@{
- *("1" "2" "3" "4")
- @}
-
- .data :@{
- *("13" "14")
- @}
+ .text :@{
+ *("1" "2" "3" "4")
+ @}
+
+ .data :@{
+ *("13" "14")
+ @}
@}
@end example
-If you have already explicitly included some files by name, @samp{*}
-refers to all @emph{remaining} files---those whose places in the output
-file have not yet been defined.
-
-@item [ @var{section} ]
-@itemx [ @var{section}, @var{section}, @dots{} ]
-@itemx [ @var{section} @var{section} @dots{} ]
-@kindex [ @var{sections} ]
-This is an alternate notation to specify named sections from all
-unallocated input files; its effect is exactly the same as that of
-@samp{* (@var{section}@dots{})}
+@cindex @code{[@var{section}@dots{}]}, not supported
+@samp{[ @var{section} @dots{} ]} used to be accepted as an alternate way
+to specify named sections from all unallocated input files. Because
+some operating systems (VMS) allow brackets in file names, that notation
+is no longer supported.
-@item @var{filename}@code{( COMMON )}
-@itemx [ COMMON ]
-@kindex [COMMON]
@cindex uninitialized data
@cindex commons in output
+@kindex *( COMMON )
+@item @var{filename}@code{( COMMON )}
+@itemx *( COMMON )
Specify where in your output file to place uninitialized data
-with this notation. @code{[COMMON]} by itself refers to all
+with this notation. @code{*(COMMON)} by itself refers to all
uninitialized data from all input files (so far as it is not yet
allocated); @var{filename}@code{(COMMON)} refers to uninitialized data
from a particular file. Both are special cases of the general
mechanisms for specifying where to place input-file sections:
-@code{gld} permits you to refer to uninitialized data as if it
+@code{ld} permits you to refer to uninitialized data as if it
were in an input-file section named @code{COMMON}, regardless of the
input file's format.
@end table
three consecutive sections, named @code{.text}, @code{.data}, and
@code{.bss}, taking the input for each from the correspondingly named
sections of all the input files:
+
@example
SECTIONS @{
- .text: @{ *(.text) @}
- .data: @{ *(.data) @}
- .bss: @{ *(.bss) [COMMON] @}
+ .text : @{ *(.text) @}
+ .data : @{ *(.data) @}
+ .bss : @{ *(.bss) *(COMMON) @}
@}
@end example
@example
SECTIONS @{
- outputa 0x10000 :
- @{
- all.o
- foo.o (.input1)
- @}
- outputb :
- @{
- foo.o (.input2)
- foo1.o (.input1)
- @}
- outputc :
- @{
- *(.input1)
- *(.input2)
- @}
+ outputa 0x10000 :
+ @{
+ all.o
+ foo.o (.input1)
+ @}
+ outputb :
+ @{
+ foo.o (.input2)
+ foo1.o (.input1)
+ @}
+ outputc :
+ @{
+ *(.input1)
+ *(.input2)
+ @}
@}
@end example
-There are still more kinds of statements permitted in the contents of
-output section definitions. The foregoing statements permitted you to
-arrange, in your output file, data originating from your input files.
-You can also place data directly in an output section from the link
-command script. Most of these additional statements involve
-expressions; @pxref{Expressions}. Although these statements are shown
-separately here for ease of presentation, no such segregation is needed
-within a section definition in the @code{SECTIONS} command; you can
-intermix them freely with any of the statements we've just described.
+@node Section Data Expressions
+@subsection Section Data Expressions
+
+@cindex expressions in a section
+The foregoing statements arrange, in your output file, data originating
+from your input files. You can also place data directly in an output
+section from the link command script. Most of these additional
+statements involve expressions; @pxref{Expressions}. Although these
+statements are shown separately here for ease of presentation, no such
+segregation is needed within a section definition in the @code{SECTIONS}
+command; you can intermix them freely with any of the statements we've
+just described.
@table @code
-@item CREATE_OBJECT_SYMBOLS
-@kindex CREATE_OBJECT_SYMBOLS
@cindex input filename symbols
@cindex filename symbols
-instructs the linker to create a symbol for each input file
-in the current section, set with the address of the first byte of
-data written from the input file. For instance, with @code{a.out}
+@kindex CREATE_OBJECT_SYMBOLS
+@item CREATE_OBJECT_SYMBOLS
+Create a symbol for each input file
+in the current section, set to the address of the first byte of
+data written from that input file. For instance, with @code{a.out}
files it is conventional to have a symbol for each input file. You can
accomplish this by defining the output @code{.text} section as follows:
@example
SECTIONS @{
- .text 0x2020 :
- @{
- CREATE_OBJECT_SYMBOLS
- *(.text)
- _etext = ALIGN(0x2000);
- @}
- @dots{}
+ .text 0x2020 :
+ @{
+ CREATE_OBJECT_SYMBOLS
+ *(.text)
+ _etext = ALIGN(0x2000);
+ @}
+ @dots{}
@}
@end example
-If @code{objsym} is a file containing this script, and @code{a.o},
+If @code{sample.ld} is a file containing this script, and @code{a.o},
@code{b.o}, @code{c.o}, and @code{d.o} are four input files with
contents like the following---
@example
@end example
@noindent
-@samp{gld -M sample a.o b.o c.o d.o} would create a map like this,
+@samp{ld -M -T sample.ld a.o b.o c.o d.o} would create a map like this,
containing symbols matching the object file names:
@example
00000000 A __DYNAMIC
00002068 t d.o
@end example
-@item @var{symbol} = @var{expression} ;
@kindex @var{symbol} = @var{expression} ;
-@itemx @var{symbol} @var{f}= @var{expression} ;
@kindex @var{symbol} @var{f}= @var{expression} ;
+@item @var{symbol} = @var{expression} ;
+@itemx @var{symbol} @var{f}= @var{expression} ;
@var{symbol} is any symbol name (@pxref{Symbols}). ``@var{f}=''
refers to any of the operators @code{&= += -= *= /=} which combine
arithmetic and assignment.
When you assign a value to a symbol within a particular section
definition, the value is relative to the beginning of the section
(@pxref{Assignment}). If you write
+
@example
SECTIONS @{
abs = 14 ;
@dots{}
- .data: @{ @dots{} rel = 14 ; @dots{} @}
+ .data : @{ @dots{} rel = 14 ; @dots{} @}
abs2 = 14 + ADDR(.data);
@dots{}
@}
@end example
+
@c FIXME: Try above example!
@noindent
-@code{abs} and @var{rel} do not have the same value; @code{rel} has the
+@code{abs} and @code{rel} do not have the same value; @code{rel} has the
same value as @code{abs2}.
-@item BYTE(@var{expression})
@kindex BYTE(@var{expression})
-@itemx SHORT(@var{expression})
@kindex SHORT(@var{expression})
-@itemx LONG(@var{expression})
@kindex LONG(@var{expression})
+@kindex QUAD(@var{expression})
@cindex direct output
-By including one of these three statements in a section definition, you
-can explicitly place one, two, or four bytes (respectively) at the
-current address of that section. Multiple-byte quantities are
-represented in whatever byte order is appropriate for the output file
-format (@pxref{BFD}).
+@item BYTE(@var{expression})
+@itemx SHORT(@var{expression})
+@itemx LONG(@var{expression})
+@itemx QUAD(@var{expression})
+By including one of these four statements in a section definition, you
+can explicitly place one, two, four, or eight bytes (respectively) at
+the current address of that section. @code{QUAD} is only supported when
+using a 64 bit host or target.
+
+@ifclear SingleFormat
+Multiple-byte quantities are represented in whatever byte order is
+appropriate for the output file format (@pxref{BFD}).
+@end ifclear
@item FILL(@var{expression})
@kindex FILL(@var{expression})
@cindex holes, filling
@cindex unspecified memory
-Specifies the ``fill pattern'' for the current section. Any otherwise
+Specify the ``fill pattern'' for the current section. Any otherwise
unspecified regions of memory within the section (for example, regions
you skip over by assigning a new value to the location counter @samp{.})
are filled with the two least significant bytes from the
fill patterns in different parts of an output section.
@end table
-@node Section Options, , Section Contents, SECTIONS
+@node Section Options
@subsection Optional Section Attributes
@cindex section defn, full syntax
Here is the full syntax of a section definition, including all the
optional portions:
-@example
+@smallexample
SECTIONS @{
@dots{}
-@var{secname} @var{start} BLOCK(@var{align}) : @{ @var{contents} @} =@var{fill} >@var{region}
+@var{secname} @var{start} BLOCK(@var{align}) (NOLOAD) : AT ( @var{ldadr} )
+ @{ @var{contents} @} =@var{fill} >@var{region}
@dots{}
@}
-@end example
+@end smallexample
@var{secname} and @var{contents} are required. @xref{Section
-Definition}, and @pxref{Section Contents} for details on @var{contents}.
-The remaining elements---@var{start}, @code{BLOCK(@var{align)}},
+Definition}, and @pxref{Section Placement} for details on
+@var{contents}. The remaining elements---@var{start},
+@code{BLOCK(@var{align)}}, @code{(NOLOAD)}, @code{AT ( @var{ldadr} )},
@code{=@var{fill}}, and @code{>@var{region}}---are all optional.
@table @code
-@item @var{start}
@cindex start address, section
@cindex section start
@cindex section address
+@item @var{start}
You can force the output section to be loaded at a specified address by
specifying @var{start} immediately following the section name.
@var{start} can be represented as any expression. The following
example generates section @var{output} at location
@code{0x40000000}:
+
@example
SECTIONS @{
- @dots{}
- output 0x40000000: @{
- @dots{}
- @}
- @dots{}
+ @dots{}
+ output 0x40000000: @{
+ @dots{}
+ @}
+ @dots{}
@}
@end example
-@item BLOCK(@var{align})
@kindex BLOCK(@var{align})
@cindex section alignment
@cindex aligning sections
-You can include @code{BLOCK()} specification to advance the location of
+@item BLOCK(@var{align})
+You can include @code{BLOCK()} specification to advance
the location counter @code{.} prior to the beginning of the section, so
that the section will begin at the specified alignment. @var{align} is
an expression.
-@item =@var{fill}
+@kindex NOLOAD
+@cindex prevent unnecessary loading
+@cindex loading, preventing
+@item (NOLOAD)
+Use @samp{(NOLOAD)} to prevent a section from being loaded into memory
+each time it is accessed. For example, in the script sample below, the
+@code{ROM} segment is addressed at memory location @samp{0} and does not
+need to be loaded into each object file:
+
+@example
+SECTIONS @{
+ ROM 0 (NOLOAD) : @{ @dots{} @}
+ @dots{}
+@}
+@end example
+
+@kindex AT ( @var{ldadr} )
+@cindex specify load address
+@cindex load address, specifying
+@item AT ( @var{ldadr} )
+The expression @var{ldadr} that follows the @code{AT} keyword specifies
+the load address of the section. The default (if you do not use the
+@code{AT} keyword) is to make the load address the same as the
+relocation address. This feature is designed to make it easy to build a
+ROM image. For example, this @code{SECTIONS} definition creates two
+output sections: one called @samp{.text}, which starts at @code{0x1000},
+and one called @samp{.mdata}, which is loaded at the end of the
+@samp{.text} section even though its relocation address is
+@code{0x2000}. The symbol @code{_data} is defined with the value
+@code{0x2000}:
+
+@smallexample
+SECTIONS
+ @{
+ .text 0x1000 : @{ *(.text) _etext = . ; @}
+ .mdata 0x2000 :
+ AT ( ADDR(.text) + SIZEOF ( .text ) )
+ @{ _data = . ; *(.data); _edata = . ; @}
+ .bss 0x3000 :
+ @{ _bstart = . ; *(.bss) *(COMMON) ; _bend = . ;@}
+@}
+@end smallexample
+
+The run-time initialization code (for C programs, usually @code{crt0})
+for use with a ROM generated this way has to include something like
+the following, to copy the initialized data from the ROM image to its runtime
+address:
+
+@smallexample
+char *src = _etext;
+char *dst = _data;
+
+/* ROM has data at end of text; copy it. */
+while (dst < _edata) @{
+ *dst++ = *src++;
+@}
+
+/* Zero bss */
+for (dst = _bstart; dst< _bend; dst++)
+ *dst = 0;
+@end smallexample
+
@kindex =@var{fill}
@cindex section fill pattern
@cindex fill pattern, entire section
-You may use any expression to specify @var{fill}. Including
-@code{=@var{fill}} in a section definition specifies the initial fill
-value for that section. Any unallocated holes in the current output
-section when written to the output file will be filled with the two
-least significant bytes of the value, repeated as necessary. You can
-also change the fill value with a @code{FILL} statement in the
-@var{contents} of a section definition.
+@item =@var{fill}
+Including @code{=@var{fill}} in a section definition specifies the
+initial fill value for that section. You may use any expression to
+specify @var{fill}. Any unallocated holes in the current output section
+when written to the output file will be filled with the two least
+significant bytes of the value, repeated as necessary. You can also
+change the fill value with a @code{FILL} statement in the @var{contents}
+of a section definition.
-@item >@var{region}
@kindex >@var{region}
@cindex section, assigning to memory region
@cindex memory regions and sections
+@item >@var{region}
Assign this section to a previously defined region of memory.
@xref{MEMORY}.
@end table
-@node Entry Point, Other Commands, SECTIONS, Commands
+@node Entry Point
@section The Entry Point
@kindex ENTRY(@var{symbol})
@cindex start of execution
order of priority: methods higher in the list override methods lower down).
@itemize @bullet
@item
-the @code{-e} @var{entry} command-line option;
+the @samp{-e} @var{entry} command-line option;
@item
-the @code{ENTRY(@var{symbol}} command in a linker control script;
+the @code{ENTRY(@var{symbol})} command in a linker control script;
@item
the value of the symbol @code{start}, if present;
@item
assignment statement: if no symbol @code{start} is defined within your
input files, you can simply define it, assigning it an appropriate
value---
+
@example
start = 0x2020;
@end example
For example, if your input object files use some other symbol-name
convention for the entry point, you can just assign the value of
whatever symbol contains the start address to @code{start}:
+
@example
-start = other_symbol;
+start = other_symbol ;
@end example
-@node Other Commands, , Entry Point, Commands
-@section Other Commands
+@node Option Commands
+@section Option Commands
The command language includes a number of other commands that you can
use for specialized purposes. They are similar in purpose to
command-line options.
@table @code
-@item FLOAT
+@kindex CONSTRUCTORS
+@cindex C++ constructors, arranging in link
+@cindex constructors, arranging in link
+@item CONSTRUCTORS
+This command ties up C++ style constructor and destructor records. The
+details of the constructor representation vary from one object format to
+another, but usually lists of constructors and destructors appear as
+special sections. The @code{CONSTRUCTORS} command specifies where the
+linker is to place the data from these sections, relative to the rest of
+the linked output. Constructor data is marked by the symbol
+@w{@code{__CTOR_LIST__}} at the start, and @w{@code{__CTOR_LIST_END}} at
+the end; destructor data is bracketed similarly, between
+@w{@code{__DTOR_LIST__}} and @w{@code{__DTOR_LIST_END}}. (The compiler
+must arrange to actually run this code; GNU C++ calls constructors from
+a subroutine @code{__main}, which it inserts automatically into the
+startup code for @code{main}, and destructors from @code{_exit}.)
+
+@need 1000
@kindex FLOAT
-@itemx NOFLOAT
@kindex NOFLOAT
+@item FLOAT
+@itemx NOFLOAT
These keywords were used in some older linkers to request a particular
-math subroutine library. @code{gld} doesn't use the keywords, assuming
+math subroutine library. @code{ld} doesn't use the keywords, assuming
instead that any necessary subroutines are in libraries specified using
the general mechanisms for linking to archives; but to permit the use of
scripts that were written for the older linkers, the keywords
@code{FLOAT} and @code{NOFLOAT} are accepted and ignored.
-@item FORCE_COMMON_ALLOCATION
@kindex FORCE_COMMON_ALLOCATION
@cindex common allocation
-This command has the same effect as the @code{-d} command-line option:
+@item FORCE_COMMON_ALLOCATION
+This command has the same effect as the @samp{-d} command-line option:
to make @code{ld} assign space to common symbols even if a relocatable
-output file is specified (@code{-r}).
+output file is specified (@samp{-r}).
-@item INPUT ( @var{file}, @var{file}, @dots{} )
@kindex INPUT ( @var{files} )
-@itemx INPUT ( @var{file} @var{file} @dots{} )
@cindex binary input files
+@item INPUT ( @var{file}, @var{file}, @dots{} )
+@itemx INPUT ( @var{file} @var{file} @dots{} )
Use this command to include binary input files in the link, without
-including them in a particular section definition. Files specified this
-way are treated identically to object files listed on the command line.
+including them in a particular section definition.
+Specify the full name for each @var{file}, including @samp{.a} if
+required.
+
+@code{ld} searches for each @var{file} through the archive-library
+search path, just as for files you specify on the command line.
+See the description of @samp{-L} in @ref{Options,,Command Line
+Options}.
@ignore
@item MAP ( @var{name} )
@item OUTPUT ( @var{filename} )
@kindex OUTPUT ( @var{filename} )
@cindex naming the output file
-Name the link output file @var{filename}. The effect of
-@code{OUTPUT(@var{filename})} is identical to the effect of
-@w{@code{-o @var{filename}}}, and whichever is encountered last will
-control the name actually used to name the output file. In particular,
-you can use this command to supply a default output-file name other than
-@code{a.out}.
+Use this command to name the link output file @var{filename}. The
+effect of @code{OUTPUT(@var{filename})} is identical to the effect of
+@w{@samp{-o @var{filename}}}, which overrides it. You can use this
+command to supply a default output-file name other than @code{a.out}.
+@ifclear SingleFormat
@item OUTPUT_ARCH ( @var{bfdname} )
@kindex OUTPUT_ARCH ( @var{bfdname} )
@cindex machine architecture, output
used by the BFD back-end routines (@pxref{BFD}). This command is often
unnecessary; the architecture is most often set implicitly by either the
system BFD configuration or as a side effect of the @code{OUTPUT_FORMAT}
-command. @refill
+command.
@item OUTPUT_FORMAT ( @var{bfdname} )
@kindex OUTPUT_FORMAT ( @var{bfdname} )
@cindex format, output file
-Specify a particular output format, with one of the names used by the
-BFD back-end routines (@pxref{BFD}). This selection will only affect
+When @code{ld} is configured to support multiple object code formats,
+you can use this command to specify a particular output format.
+@var{bfdname} is one of the names used by the BFD back-end routines
+(@pxref{BFD}). The effect is identical to the effect of the
+@samp{-oformat} command-line option. This selection affects only
the output file; the related command @code{TARGET} affects primarily
-input files.@refill
+input files.
+@end ifclear
@item SEARCH_DIR ( @var{path} )
@kindex SEARCH_DIR ( @var{path} )
@cindex path for libraries
@cindex search path, libraries
-Add @var{path} to the list of paths where @code{gld} looks for
+Add @var{path} to the list of paths where @code{ld} looks for
archive libraries. @code{SEARCH_DIR(@var{path})} has the same
-effect as @code{-L@var{path})} on the command line.
+effect as @samp{-L@var{path}} on the command line.
@item STARTUP ( @var{filename} )
@kindex STARTUP ( @var{filename} )
Ensure that @var{filename} is the first input file used in the link
process.
+@ifclear SingleFormat
@item TARGET ( @var{format} )
@cindex input file format
@kindex TARGET ( @var{format} )
-Change the input-file object code format (like the command-line option
-@code{-b} or its synonym @code{-format}). The argument @var{format} is
-one of the strings used by BFD to name binary formats. In the current
-@code{gld} implementation, if @code{TARGET} is specified but
-@code{OUTPUT_FORMAT} is not, the last @code{TARGET} argument is also
-used as the default format for the @code{gld} output file.
-@xref{BFD}.@refill
+When @code{ld} is configured to support multiple object code formats,
+you can use this command to change the input-file object code format
+(like the command-line option @samp{-b} or its synonym @samp{-format}).
+The argument @var{format} is one of the strings used by BFD to name
+binary formats. If @code{TARGET} is specified but @code{OUTPUT_FORMAT}
+is not, the last @code{TARGET} argument is also used as the default
+format for the @code{ld} output file. @xref{BFD}.
@kindex GNUTARGET
-If you don't use the @code{TARGET} command, @code{gld} uses the value of
+If you don't use the @code{TARGET} command, @code{ld} uses the value of
the environment variable @code{GNUTARGET}, if available, to select the
-output file format. If that variable is also absent, @code{gld} uses
+output file format. If that variable is also absent, @code{ld} uses
the default format configured for your machine in the BFD libraries.
-
+@end ifclear
@end table
-@node Machine Dependent, BFD, Commands, Top
+@ifset GENERIC
+@node Machine Dependent
@chapter Machine Dependent Features
@cindex machine dependencies
-@code{gld} has additional features on some platforms; the following
-sections describe them. Machines where @code{gld} has no additional
+@code{ld} has additional features on some platforms; the following
+sections describe them. Machines where @code{ld} has no additional
functionality are not listed.
@menu
-* H8/300:: @code{gld} and the H8/300
-* i960:: @code{gld} and the Intel 960 family
-* m68k:: @code{gld} and the Motorola 68000 family
-* m88k:: @code{gld} and the Motorola 880x0 family
+* H8/300:: @code{ld} and the H8/300
+* i960:: @code{ld} and the Intel 960 family
@end menu
+@end ifset
-@node H8/300, i960, Machine Dependent, Machine Dependent
-@section @code{gld} and the H8/300
+@c FIXME! This could use @raisesections/@lowersections, but there seems to be a conflict
+@c between those and node-defaulting.
+@ifset H8300
+@ifclear GENERIC
+@raisesections
+@end ifclear
+@node H8/300
+@section @code{ld} and the H8/300
@cindex H8/300 support
-For the H8/300, @code{gld} can perform these global optimizations when
+For the H8/300, @code{ld} can perform these global optimizations when
you specify the @samp{-relax} command-line option.
@table @emph
@item relaxing address modes
-@cindex relaxing on i960
-@code{gld} finds all @code{jsr} and @code{jmp} instructions whose
+@cindex relaxing on H8/300
+@code{ld} finds all @code{jsr} and @code{jmp} instructions whose
targets are within eight bits, and turns them into eight-bit
program-counter relative @code{bsr} and @code{bra} instructions,
respectively.
@item synthesizing instructions
-@cindex synthesizing on i960
+@cindex synthesizing on H8/300
@c FIXME: specifically mov.b, or any mov instructions really?
-@code{gld} finds all @code{mov.b} instructions which use the
+@code{ld} finds all @code{mov.b} instructions which use the
sixteen-bit absolute address form, but refer to the top
page of memory, and changes them to use the eight-bit address form.
(That is: the linker turns @samp{mov.b @code{@@}@var{aa}:16} into
@samp{mov.b @code{@@}@var{aa}:8} whenever the address @var{aa} is in the
top page of memory).
@end table
-
-@node i960, m68k, H8/300, Machine Dependent
-@section @code{gld} and the Intel 960 family
+@ifclear GENERIC
+@lowersections
+@end ifclear
+@end ifset
+
+@ifset I960
+@ifclear GENERIC
+@raisesections
+@end ifclear
+@node i960
+@section @code{ld} and the Intel 960 family
@cindex i960 support
-@menu
-* i960-arch:: Linking for a Specific i960 Architecture
-* i960-emulation:: Emulating Other i960 Linkers
-* i960-commands:: Command Language Extensions for i960
-@end menu
-@node i960-arch, i960-emulation, i960, i960
-@subsection Linking for a Specific i960 Architecture
You can use the @samp{-A@var{architecture}} command line option to
specify one of the two-letter names identifying members of the 960
family; the option specifies the desired output target, and warns of any
libraries specific to each particular architecture, by including in the
search loop names suffixed with the string identifying the architecture.
-For example, if your @code{gld} command line included @w{@samp{-ACA}} as
+For example, if your @code{ld} command line included @w{@samp{-ACA}} as
well as @w{@samp{-ltry}}, the linker would look (in its built-in search
-paths, and in any paths you specify with @code{-L}) for a library with
+paths, and in any paths you specify with @samp{-L}) for a library with
the names
+
@example
try
libtry.a
tryca
libtryca.a
@end example
+
@noindent
The first two possibilities would be considered in any event; the last
two are due to the use of @w{@samp{-ACA}}.
-You can meaningfully use @code{-A} more than once on a command line, since
+You can meaningfully use @samp{-A} more than once on a command line, since
the 960 architecture family allows combination of target architectures; each
-use will add another pair of name variants to search for when @w{@code{-l}}
+use will add another pair of name variants to search for when @w{@samp{-l}}
specifies a library.
-@node i960-emulation, i960-commands, i960-arch, i960
-@subsection Emulating Other i960 Linkers
-You can set the @code{LDEMULATION} environment variable
-(@pxref{Environment,,Environment Variables}) to make
-@code{gld} more compatible with two older Intel 960 linkers:
-
-@table @code
-@item LDEMULATION=gld960
-@kindex gld960
-@kindex G960LIB
-@kindex G960BASE
-@cindex i960
-Emulate the Intel port of the older @code{gld} for the i960
-architectures. The default library search paths are taken from two
-other environment variables, @code{G960LIB} and @code{G960BASE}. The
-default architecture is @code{i960}. The default output format is set
-to @code{b.out.big}, and in fact the default output file name (if
-@code{-o} is not specified) is @code{b.out}, to reflect this variant
-format, for this emulation.
-
-@kindex GNU960
-This emulation can behave slightly differently depending on the setting
-of the @code{gld} compile-time switch @code{GNU960}. If @code{gld} is
-compiled with @code{GNU960} defined, then an additional environment
-variable---@code{GNUTARGET}---is available; its value, if available,
-specifies some other default output format than @code{b.out.big}.
-
-@item LDEMULATION=lnk960
-@kindex lnk960
-@cindex i960
-@cindex Architectures, i960 family
-Emulate the Intel linker @code{lnk960}. The default output format is
-@code{coff-Intel-big}. With this emulation, @code{gld}
-supports the additional script commands @code{HLL} and @code{SYSLIB} for
-specification of library archives. This is the only emulation with
-extensive support for the @code{-A} (architecture) command-line option.
-By default, the architecture @code{CORE} is assumed, but you can choose
-additional features from the i960 architecture family by using one of
-the following with @code{-A} (or by using the @code{OUTPUT_ARCH} command
-from a script):
-@example
-CORE
-KB
-SB
-MC
-XA
-CA
-KA
-SA
-@end example
-
-The default libraries are chosen with some attention to the architecture
-selected; the core library @file{cg} is always included, but the library
-@code{fpg} is also used if you've specified any of the architectures
-@code{KA}, @code{SA}, or @code{CA}.
-
-@kindex GNU960
-Like @code{gld960}, this emulation uses additional environment variables
-to set the default library search paths. Also like @code{gld960}, the
-behavior of this emulation is slightly different depending on whether
-@code{gld} itself was compiled with @code{GNU960} defined.
-
-@kindex G960BASE
-@kindex G960LIB
-@kindex I960BASE
-If your @code{gld} was compiled with @code{GNU960} defined, the default
-paths are taken from all three of @code{G960LIB}, @code{G960BASE}, and
-@code{I960BASE}. For the first two, paths you supply are automatically
-suffixed with @samp{/lib/libcoff}; for the last, your path is
-automatically suffixed with @samp{/lib}.
-
-If your @code{gld} was @emph{not} compiled with @code{GNU960} defined,
-the default paths are taken from @code{I960BASE}, and @code{G960BASE} is
-only consulted if @code{I960BASE} is undefined. In this case
-@code{G960LIB} is not used at all.
-@end table
-
-@node i960-commands, , i960-emulation, i960
-@subsection Command Language Extensions for i960
-
-@code{gld} understands the following additional commands when
-@code{LDEMULATION} is set to @samp{lnk960}:
-
-@table @code
-@item HLL ( @var{file}, @var{file}, @dots{} )
-@itemx HLL ( @var{file} @var{file} @dots{} )
-@itemx HLL ( )
-@kindex HLL ( @var{files} )
-Include ``high-level libraries'' or archives as input files in the link.
-Using @code{HLL(@var{file}} in a linker script is equivalent to
-including @code{-l}@var{file} on the command line.
-
-@cindex @code{lnk960} command @code{HLL}
-The @code{HLL} command is only supported when @code{gld} emulates
-@code{lnk960}, as specified by the @code{LDEMULATION} environment
-variable.
-
-@item SYSLIB ( @var{file}, @var{file}, @dots{} )
-@itemx SYSLIB ( @var{file} @var{file} @dots{} )
-@kindex SYSLIB ( @var{file}, @var{file}, @dots{} )
-Use the named @var{file}s as binary input files, searching for them in
-the same list of paths as archives.
-
-@cindex @code{lnk960} command @code{SYSLIB}
-The @code{SYSLIB} command is only supported when @code{gld} emulates
-@code{lnk960}, as specified by the @code{LDEMULATION} environment
-variable.
-
-@end table
-
-@node m68k, m88k, i960, Machine Dependent
-@section @code{gld} and the Motorola 680x0 family
-
-@cindex m68k support
-You can set the environment variable @code{LDEMULATION} to @samp{gld68k}
-for closer compatibility with the older GNU linker on Motorola 680x0
-platforms. This emulation is a variant of the @code{gld} emulation; it
-only differs in specifically setting the default BFD machine as
-@code{m68k}. @xref{Environment,,Environment Variables}.
-
-@node m88k, , m68k, Machine Dependent
-@section @code{gld} and the Motorola 880x0 family
-
-@cindex m88k support
-@kindex gldm88kbcs
-You can configure the linker to conform to the Motorola 88K BCS by
-setting the environment variable @code{LDEMULATION} to @samp{gldm88kbcs}.
-This sets the output format to @code{m88kbcs} and the architecture to
-@code{m88k}. Default library search paths are
-@example
-/lib
-/usr/lib
-/usr/local/lib
-@end example
-
-For other settings of @code{LDEMULATION}, consult
-@ref{Environment,,Environment Variables}.
-
-@node BFD, Index, Machine Dependent, Top
+@cindex @code{-relax} on i960
+@cindex relaxing on i960
+@code{ld} supports the @samp{-relax} option for the i960 family. If you
+specify @samp{-relax}, @code{ld} finds all @code{balx} and @code{calx}
+instructions whose targets are within 24 bits, and turns them into
+24-bit program-counter relative @code{bal} and @code{cal}
+instructions, respectively. @code{ld} also turns @code{cal}
+instructions into @code{bal} instructions when it determines that the
+target subroutine is a leaf routine (that is, the target subroutine does
+not itself call any subroutines).
+
+@ifclear GENERIC
+@lowersections
+@end ifclear
+@end ifset
+
+@ifclear SingleFormat
+@node BFD
@chapter BFD
@cindex back end
@cindex object file management
+@cindex object formats available
+@kindex objdump -i
The linker accesses object and archive files using the BFD libraries.
These libraries allow the linker to use the same routines to operate on
object files whatever the object file format. A different object file
format can be supported simply by creating a new BFD back end and adding
-it to the library. You can use @code{objdump -i}
+it to the library. To conserve runtime memory, however, the linker and
+associated tools are usually configured to support only a subset of the
+object file formats available. You can use @code{objdump -i}
(@pxref{objdump,,objdump,binutils.info,The GNU Binary Utilities}) to
-list all the formats available for each architecture under BFD. This
-was the list of formats, and of architectures supported for each format,
-as of the time this manual was prepared:
-@cindex formats available
-@cindex architectures available
-@example
-BFD header file version 0.18
-a.out-i386
- (header big endian, data big endian)
- m68k:68020
- a29k
- sparc
- i386
-a.out-sunos-big
- (header big endian, data big endian)
- m68k:68020
- a29k
- sparc
- i386
-b.out.big
- (header big endian, data little endian)
- i960:core
-b.out.little
- (header little endian, data little endian)
- i960:core
-coff-a29k-big
- (header big endian, data big endian)
- a29k
-coff-h8300
- (header big endian, data big endian)
- H8/300
-coff-i386
- (header little endian, data little endian)
- i386
-coff-Intel-big
- (header big endian, data little endian)
- i960:core
-coff-Intel-little
- (header little endian, data little endian)
- i960:core
-coff-m68k
- (header big endian, data big endian)
- m68k:68020
-coff-m88kbcs
- (header big endian, data big endian)
- m88k:88100
-ecoff-bigmips
- (header big endian, data big endian)
- mips
-ecoff-littlemips
- (header little endian, data little endian)
- mips
-elf-big
- (header big endian, data big endian)
- m68k:68020
- vax
- i960:core
- a29k
- sparc
- mips
- i386
- m88k:88100
- H8/300
- rs6000:6000
-elf-little
- (header little endian, data little endian)
- m68k:68020
- vax
- i960:core
- a29k
- sparc
- mips
- i386
- m88k:88100
- H8/300
- rs6000:6000
-ieee
- (header big endian, data big endian)
- m68k:68020
- vax
- i960:core
- a29k
- sparc
- mips
- i386
- m88k:88100
- H8/300
- rs6000:6000
-srec
- (header big endian, data big endian)
- m68k:68020
- vax
- i960:core
- a29k
- sparc
- mips
- i386
- m88k:88100
- H8/300
- rs6000:6000
-@end example
+list all the formats available for your configuration.
@cindex BFD requirements
@cindex requirements for BFD
One minor artifact of the BFD solution which you should bear in
mind is the potential for information loss. There are two places where
-useful information can be lost using the BFD mechanism; during
+useful information can be lost using the BFD mechanism: during
conversion and during output. @xref{BFD information loss}.
@menu
-* BFD outline:: How it works: an outline of BFD
-* BFD information loss:: Information Loss
-* Mechanism:: Mechanism
+* BFD outline:: How it works: an outline of BFD
@end menu
-@node BFD outline, BFD information loss, BFD, BFD
+@node BFD outline
@section How it works: an outline of BFD
@cindex opening object files
-When an object file is opened, BFD subroutines automatically
-determine the format of the input object file, and build a descriptor in
-memory with pointers to routines that will be used to access elements of
-the object file's data structures.
-
-As different information from the the object files is required
-BFD reads from different sections of the file and processes them.
-For example a very common operation for the linker is processing symbol
-tables. Each BFD back end provides a routine for converting
-between the object file's representation of symbols and an internal
-canonical format. When the linker asks for the symbol table of an object
-file, it calls through the memory pointer to the relevant BFD
-back end routine which reads and converts the table into a canonical
-form. The linker then operates upon the common form. When the link is
-finished and the linker writes the symbol table of the output file,
-another BFD back end routine is called which takes the newly
-created symbol table and converts it into the chosen output format.
-
-@node BFD information loss, Mechanism, BFD outline, BFD
-@section Information Loss
-@emph{Information can be lost during output.} The output formats
-supported by BFD do not provide identical facilities, and
-information which may be described in one form has nowhere to go in
-another format. One example of this is alignment information in
-@code{b.out}. There is nowhere in an @code{a.out} format file to store
-alignment information on the contained data, so when a file is linked
-from @code{b.out} and an @code{a.out} image is produced, alignment
-information will not propagate to the output file. (The linker will
-still use the alignment information internally, so the link is performed
-correctly).
-
-Another example is COFF section names. COFF files may contain an
-unlimited number of sections, each one with a textual section name. If
-the target of the link is a format which does not have many sections (eg
-@code{a.out}) or has sections without names (eg the Oasys format) the
-link cannot be done simply. You can circumvent this problem by
-describing the desired input-to-output section mapping with the command
-language.
-
-@emph{Information can be lost during canonicalization.} The BFD
-internal canonical form of the external formats is not exhaustive; there
-are structures in input formats for which there is no direct
-representation internally. This means that the BFD back ends
-cannot maintain all possible data richness through the transformation
-between external to internal and back to external formats.
-
-This limitation is only a problem when using the linker to read one
-format and write another. Each BFD back end is responsible for
-maintaining as much data as possible, and the internal BFD
-canonical form has structures which are opaque to the BFD core,
-and exported only to the back ends. When a file is read in one format,
-the canonical form is generated for BFD and the linker. At the
-same time, the back end saves away any information which may otherwise
-be lost. If the data is then written back in the same format, the back
-end routine will be able to use the canonical form provided by the
-BFD core as well as the information it prepared earlier. Since
-there is a great deal of commonality between back ends, this mechanism
-is very useful. There is no information lost for this reason when
-linking big endian COFF to little endian COFF, or from @code{a.out} to
-@code{b.out}. When a mixture of formats is linked, the information is
-only lost from the files whose format differs from the destination.
-
-@node Mechanism, , BFD information loss, BFD
-@section Mechanism
-The greatest potential for loss of information is when there is least
-overlap between the information provided by the source format, that
-stored by the canonical format, and the information needed by the
-destination format. A brief description of the canonical form may help
-you appreciate what kinds of data you can count on preserving across
-conversions.
-@cindex BFD canonical format
-@cindex internal object-file format
+@include bfdsumm.texi
+@end ifclear
+
+@node MRI
+@appendix MRI Compatible Script Files
+@cindex MRI compatibility
+To aid users making the transition to @sc{gnu} @code{ld} from the MRI
+linker, @code{ld} can use MRI compatible linker scripts as an
+alternative to the more general-purpose linker scripting language
+described in @ref{Commands,,Command Language}. MRI compatible linker
+scripts have a much simpler command set than the scripting language
+otherwise used with @code{ld}. @sc{gnu} @code{ld} supports the most
+commonly used MRI linker commands; these commands are described here.
+
+In general, MRI scripts aren't of much use with the @code{a.out} object
+file format, since it only has three sections and MRI scripts lack some
+features to make use of them.
+
+You can specify a file containing an MRI-compatible script using the
+@samp{-c} command-line option.
+
+Each command in an MRI-compatible script occupies its own line; each
+command line starts with the keyword that identifies the command (though
+blank lines are also allowed for punctuation). If a line of an
+MRI-compatible script begins with an unrecognized keyword, @code{ld}
+issues a warning message, but continues processing the script.
+
+Lines beginning with @samp{*} are comments.
+
+You can write these commands using all upper-case letters, or all
+lower case; for example, @samp{chip} is the same as @samp{CHIP}.
+The following list shows only the upper-case form of each command.
-@table @emph
-@item files
-Information on target machine architecture, particular implementation
-and format type are stored on a per-file basis. Other information
-includes a demand pageable bit and a write protected bit. Note that
-information like Unix magic numbers is not stored here---only the magic
-numbers' meaning, so a @code{ZMAGIC} file would have both the demand pageable
-bit and the write protected text bit set.
-
-The byte order of the target is stored on a per-file basis, so that big-
-and little-endian object files may be linked with one another.
-
-@item sections
-Each section in the input file contains the name of the section, the
-original address in the object file, various flags, size and alignment
-information and pointers into other BFD data structures.
-
-@item symbols
-Each symbol contains a pointer to the object file which originally
-defined it, its name, its value, and various flag bits. When a
-BFD back end reads in a symbol table, the back end relocates all
-symbols to make them relative to the base of the section where they were
-defined. This ensures that each symbol points to its containing
-section. Each symbol also has a varying amount of hidden data to contain
-private data for the BFD back end. Since the symbol points to the
-original file, the private data format for that symbol is accessible.
-@code{gld} can operate on a collection of symbols of wildly different
-formats without problems.
-
-Normal global and simple local symbols are maintained on output, so an
-output file (no matter its format) will retain symbols pointing to
-functions and to global, static, and common variables. Some symbol
-information is not worth retaining; in @code{a.out} type information is
-stored in the symbol table as long symbol names. This information would
-be useless to most COFF debuggers and may be thrown away with
-appropriate command line switches. (The GNU debugger @code{gdb} does
-support @code{a.out} style debugging information in COFF).
-
-There is one word of type information within the symbol, so if the
-format supports symbol type information within symbols (for example COFF,
-IEEE, Oasys) and the type is simple enough to fit within one word
-(nearly everything but aggregates) the information will be preserved.
-
-@item relocation level
-Each canonical BFD relocation record contains a pointer to the symbol to
-relocate to, the offset of the data to relocate, the section the data
-is in and a pointer to a relocation type descriptor. Relocation is
-performed effectively by message passing through the relocation type
-descriptor and symbol pointer. It allows relocations to be performed
-on output data using a relocation method only available in one of the
-input formats. For instance, Oasys provides a byte relocation format.
-A relocation record requesting this relocation type would point
-indirectly to a routine to perform this, so the relocation may be
-performed on a byte being written to a COFF file, even though 68k COFF
-has no such relocation type.
-@c FIXME why specific reference to 68K above?
-
-@item line numbers
-Object formats can contain, for debugging purposes, some form of mapping
-between symbols, source line numbers, and addresses in the output file.
-These addresses have to be relocated along with the symbol information.
-Each symbol with an associated list of line number records points to the
-first record of the list. The head of a line number list consists of a
-pointer to the symbol, which allows divination of the address of the
-function whose line number is being described. The rest of the list is
-made up of pairs: offsets into the section and line numbers. Any format
-which can simply derive this information can pass it successfully
-between formats (COFF, IEEE and Oasys).
+@table @code
+@cindex @code{ABSOLUTE} (MRI)
+@item ABSOLUTE @var{secname}
+@item ABSOLUTE @var{secname}, @var{secname}, @dots{} @var{secname}
+Normally, @code{ld} includes in the output file all sections from all
+the input files. However, in an MRI-compatible script, you can use the
+@code{ABSOLUTE} command to restrict the sections that will be present in
+your output program. If the @code{ABSOLUTE} command is used at all in a
+script, then only the sections named explicitly in @code{ABSOLUTE}
+commands will appear in the linker output. You can still use other
+input sections (whatever you select on the command line, or using
+@code{LOAD}) to resolve addresses in the output file.
+
+@cindex @code{ALIAS} (MRI)
+@item ALIAS @var{out-secname}, @var{in-secname}
+Use this command to place the data from input section @var{in-secname}
+in a section called @var{out-secname} in the linker output file.
+
+@var{in-secname} may be an integer.
+
+@cindex @code{BASE} (MRI)
+@item BASE @var{expression}
+Use the value of @var{expression} as the lowest address (other than
+absolute addresses) in the output file.
+
+@cindex @code{CHIP} (MRI)
+@item CHIP @var{expression}
+@itemx CHIP @var{expression}, @var{expression}
+This command does nothing; it is accepted only for compatibility.
+
+@cindex @code{END} (MRI)
+@item END
+This command does nothing whatever; it's only accepted for compatibility.
+
+@cindex @code{FORMAT} (MRI)
+@item FORMAT @var{output-format}
+Similar to the @code{OUTPUT_FORMAT} command in the more general linker
+language, but restricted to one of these output formats:
+
+@enumerate
+@item
+S-records, if @var{output-format} is @samp{S}
+
+@item
+IEEE, if @var{output-format} is @samp{IEEE}
+
+@item
+COFF (the @samp{coff-m68k} variant in BFD), if @var{output-format} is
+@samp{COFF}
+@end enumerate
+
+@cindex @code{LIST} (MRI)
+@item LIST @var{anything}@dots{}
+Print (to the standard output file) a link map, as produced by the
+@code{ld} command-line option @samp{-M}.
+
+The keyword @code{LIST} may be followed by anything on the
+same line, with no change in its effect.
+
+@cindex @code{LOAD} (MRI)
+@item LOAD @var{filename}
+@item LOAD @var{filename}, @var{filename}, @dots{} @var{filename}
+Include one or more object file @var{filename} in the link; this has the
+same effect as specifying @var{filename} directly on the @code{ld}
+command line.
+
+@cindex @code{NAME} (MRI)
+@item NAME @var{output-name}
+@var{output-name} is the name for the program produced by @code{ld}; the
+MRI-compatible command @code{NAME} is equivalent to the command-line
+option @samp{-o} or the general script language command @code{OUTPUT}.
+
+@cindex @code{ORDER} (MRI)
+@item ORDER @var{secname}, @var{secname}, @dots{} @var{secname}
+@itemx ORDER @var{secname} @var{secname} @var{secname}
+Normally, @code{ld} orders the sections in its output file in the
+order in which they first appear in the input files. In an MRI-compatible
+script, you can override this ordering with the @code{ORDER} command. The
+sections you list with @code{ORDER} will appear first in your output
+file, in the order specified.
+
+@cindex @code{PUBLIC} (MRI)
+@item PUBLIC @var{name}=@var{expression}
+@itemx PUBLIC @var{name},@var{expression}
+@itemx PUBLIC @var{name} @var{expression}
+Supply a value (@var{expression}) for external symbol
+@var{name} used in the linker input files.
+
+@cindex @code{SECT} (MRI)
+@item SECT @var{secname}, @var{expression}
+@itemx SECT @var{secname}=@var{expression}
+@itemx SECT @var{secname} @var{expression}
+You can use any of these three forms of the @code{SECT} command to
+specify the start address (@var{expression}) for section @var{secname}.
+If you have more than one @code{SECT} statement for the same
+@var{secname}, only the @emph{first} sets the start address.
@end table
-@node Index, , BFD, Top
+
+@node Index
@unnumbered Index
@printindex cp
projects / deliverable / binutils-gdb.git / blobdiff