\input texinfo
@setfilename ld.info
@c Copyright 1991, 1992, 1993, 1994, 1995, 1996, 1997, 1998, 1999, 2000,
-@c 2001, 2002 Free Software Foundation, Inc.
+@c 2001, 2002, 2003 Free Software Foundation, Inc.
@syncodeindex ky cp
@include configdoc.texi
@c (configdoc.texi is generated by the Makefile)
@set MCORE
@set MIPS
@set MMIX
+@set MSP430
@set PDP11
@set PJ
@set SH
@set SPARC
-@set C54X
+@set TIC54X
@set V850
@set VAX
+@set WIN32
+@set XTENSA
@end ifset
@c man end
This file documents the @sc{gnu} linker LD version @value{VERSION}.
Copyright (C) 1991, 92, 93, 94, 95, 96, 97, 98, 99, 2000,
-2001, 2002 Free Software Foundation, Inc.
+2001, 2002, 2003 Free Software Foundation, Inc.
@ignore
or any later version published by the Free Software Foundation;
with no Invariant Sections, with no Front-Cover Texts, and with no
Back-Cover Texts. A copy of the license is included in the
-section entitled "GNU Free Documentation License".
+section entitled ``GNU Free Documentation License''.
Permission is granted to process this file through Tex and print the
results, provided the printed document carries copying permission
@vskip 0pt plus 1filll
@c man begin COPYRIGHT
-Copyright @copyright{} 1991, 92, 93, 94, 95, 96, 97, 98, 99, 2000, 2001 Free Software Foundation, Inc.
+Copyright @copyright{} 1991, 92, 93, 94, 95, 96, 97, 98, 99, 2000, 2001,
+2002, 2003 Free Software Foundation, Inc.
Permission is granted to copy, distribute and/or modify this document
under the terms of the GNU Free Documentation License, Version 1.1
or any later version published by the Free Software Foundation;
with no Invariant Sections, with no Front-Cover Texts, and with no
Back-Cover Texts. A copy of the license is included in the
-section entitled "GNU Free Documentation License".
+section entitled ``GNU Free Documentation License''.
@c man end
@end titlepage
@end iftex
@c FIXME: Talk about importance of *order* of args, cmds to linker!
-@ifinfo
+@ifnottex
@node Top
@top Using ld
This file documents the @sc{gnu} linker ld version @value{VERSION}.
This document is distributed under the terms of the GNU Free
Documentation License. A copy of the license is included in the
-section entitled "GNU Free Documentation License".
+section entitled ``GNU Free Documentation License''.
@menu
* Overview:: Overview
@ifset H8300
* H8/300:: ld and the H8/300
@end ifset
-@ifset Hitachi
-* Hitachi:: ld and other Hitachi micros
+@ifset Renesas
+* Renesas:: ld and other Renesas micros
@end ifset
@ifset I960
* i960:: ld and the Intel 960 family
@end ifset
+@ifset ARM
+* ARM:: ld and the ARM family
+@end ifset
+@ifset HPPA
+* HPPA ELF32:: ld and HPPA 32-bit ELF
+@end ifset
@ifset TICOFF
* TI COFF:: ld and the TI COFF
@end ifset
+@ifset WIN32
+* Win32:: ld and WIN32 (cygwin/mingw)
+@end ifset
+@ifset XTENSA
+* Xtensa:: ld and Xtensa Processors
+@end ifset
@end ifclear
@ifclear SingleFormat
* BFD:: BFD
* GNU Free Documentation License:: GNU Free Documentation License
* Index:: Index
@end menu
-@end ifinfo
+@end ifnottex
@node Overview
@chapter Overview
are specified, the linker does not produce any output, and issues the
message @samp{No input files}.
-If the linker can not recognize the format of an object file, it will
+If the linker cannot recognize the format of an object file, it will
assume that it is a linker script. A script specified in this way
augments the main linker script used for the link (either the default
linker script or the one specified by using @samp{-T}). This feature
For options whose names are multiple letters, either one dash or two can
precede the option name; for example, @samp{-trace-symbol} and
-@samp{--trace-symbol} are equivalent. Note - there is one exception to
+@samp{--trace-symbol} are equivalent. Note---there is one exception to
this rule. Multiple letter options that start with a lower case 'o' can
only be preceeded by two dashes. This is to reduce confusion with the
@samp{-o} option. So for example @samp{-omagic} sets the output file
Unique abbreviations of the names of multiple-letter options are
accepted.
-Note - if the linker is being invoked indirectly, via a compiler driver
-(eg @samp{gcc}) then all the linker command line options should be
+Note---if the linker is being invoked indirectly, via a compiler driver
+(e.g. @samp{gcc}) then all the linker command line options should be
prefixed by @samp{-Wl,} (or whatever is appropriate for the particular
compiler driver) like this:
be added to the dynamic symbol table if the output format supports it.
See the description of @samp{--version-script} in @ref{VERSION}.
+@ifclear SingleFormat
@cindex big-endian objects
@cindex endianness
@kindex -EB
@kindex -EL
@item -EL
Link little-endian objects. This affects the default output format.
+@end ifclear
@kindex -f
@kindex --auxiliary
Some older linkers used the @option{-F} option throughout a compilation
toolchain for specifying object-file format for both input and output
-object files. The @sc{gnu} linker uses other mechanisms for this
-purpose: the @option{-b}, @option{--format}, @option{--oformat} options, the
+object files.
+@ifclear SingleFormat
+The @sc{gnu} linker uses other mechanisms for this purpose: the
+@option{-b}, @option{--format}, @option{--oformat} options, the
@code{TARGET} command in linker scripts, and the @code{GNUTARGET}
-environment variable. The @sc{gnu} linker will ignore the @option{-F}
-option when not creating an ELF shared object.
+environment variable.
+@end ifclear
+The @sc{gnu} linker will ignore the @option{-F} option when not
+creating an ELF shared object.
@cindex finalization function
@kindex -fini
@option{-L} options apply to all @option{-l} options, regardless of the
order in which the options appear.
+If @var{searchdir} begins with @code{=}, then the @code{=} will be replaced
+by the @dfn{sysroot prefix}, a path specified when the linker is configured.
+
@ifset UsesEnvVars
The default set of paths searched (without being specified with
@samp{-L}) depends on which emulation mode @command{ld} is using, and in
@item -N
@itemx --omagic
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}.
+not page-align the data segment, and disable linking against shared
+libraries. If the output format supports Unix style magic numbers,
+mark the output as @code{OMAGIC}.
+
+@kindex --no-omagic
+@cindex OMAGIC
+@item --no-omagic
+This option negates most of the effects of the @option{-N} option. It
+sets the text section to be read-only, and forces the data segment to
+be page-aligned. Note - this option does not enable linking against
+shared libraries. Use @option{-Bdynamic} for this.
@kindex -o @var{output}
@kindex --output=@var{output}
@cindex partial link
@cindex relocatable output
@kindex -r
-@kindex --relocateable
+@kindex --relocatable
@item -r
-@itemx --relocateable
+@itemx --relocatable
Generate relocatable output---i.e., generate an output file that can in
turn serve as input to @command{ld}. This is often called @dfn{partial
linking}. As a side effect, in environments that support standard Unix
@code{now} marks the object with the non-lazy runtime binding.
@code{origin} marks the object may contain $ORIGIN.
@code{defs} disallows undefined symbols.
+@code{muldefs} allows multiple definitions.
@code{combreloc} combines multiple reloc sections and sorts them
to make dynamic symbol lookup caching possible.
@code{nocombreloc} disables multiple reloc sections combining.
it only when there are unavoidable circular references between two or
more archives.
+@kindex --accept-unknown-input-arch
+@kindex --no-accept-unknown-input-arch
+@item --accept-unknown-input-arch
+@itemx --no-accept-unknown-input-arch
+Tells the linker to accept input files whose architecture cannot be
+recognised. The assumption is that the user knows what they are doing
+and deliberately wants to link in these unknown input files. This was
+the default behaviour of the linker, before release 2.14. The default
+behaviour from release 2.14 onwards is to reject such input files, and
+so the @samp{--accept-unknown-input-arch} option has been added to
+restore the old behaviour.
+
@kindex -assert @var{keyword}
@item -assert @var{keyword}
This option is ignored for SunOS compatibility.
@item --no-undefined
@itemx -z defs
Normally when creating a non-symbolic shared library, undefined symbols
-are allowed and left to be resolved by the runtime loader. These options
-disallows such undefined symbols.
+are allowed and left to be resolved by the runtime loader. This option
+disallows such undefined symbols if they come from regular object
+files. The switch @samp{--no-allow-shlib-undefined} controls the
+behaviour for shared objects being linked into the shared library.
+
+@kindex --allow-multiple-definition
+@kindex -z muldefs
+@item --allow-multiple-definition
+@itemx -z muldefs
+Normally when a symbol is defined multiple times, the linker will
+report a fatal error. These options allow multiple definitions and the
+first definition will be used.
@kindex --allow-shlib-undefined
+@kindex --no-allow-shlib-undefined
@item --allow-shlib-undefined
-Allow undefined symbols in shared objects even when --no-undefined is
-set. The net result will be that undefined symbols in regular objects
-will still trigger an error, but undefined symbols in shared objects
-will be ignored. The implementation of no_undefined makes the
-assumption that the runtime linker will choke on undefined symbols.
-However there is at least one system (BeOS) where undefined symbols in
-shared libraries is normal since the kernel patches them at load time to
-select which function is most appropriate for the current architecture.
-I.E. dynamically select an appropriate memset function. Apparently it
-is also normal for HPPA shared libraries to have undefined symbols.
+@itemx --no-allow-shlib-undefined
+Allow (the default) or disallow undefined symbols in shared objects.
+The setting of this switch overrides @samp{--no-undefined} where
+shared objects are concerned. Thus if @samp{--no-undefined} is set
+but @samp{--no-allow-shlib-undefined} is not, the net result will be
+that undefined symbols in regular object files will trigger an error,
+but undefined symbols in shared objects will be ignored.
+
+The reason that @samp{--allow-shlib-undefined} is the default is that
+the shared object being specified at link time may not be the same one
+that is available at load time, so the symbols might actually be
+resolvable at load time. Plus there are some systems, (eg BeOS) where
+undefined symbols in shared libraries is normal since the kernel
+patches them at load time to select which function is most appropriate
+for the current architecture. eg. to dynamically select an appropriate
+memset function. Apparently it is also normal for HPPA shared
+libraries to have undefined symbols.
+
+@kindex --no-undefined-version
+@item --no-undefined-version
+Normally when a symbol has an undefined version, the linker will ignore
+it. This option disallows symbols with undefined version and a fatal error
+will be issued instead.
@kindex --no-warn-mismatch
@item --no-warn-mismatch
this option overrides it. @xref{BFD}.
@end ifclear
+@kindex -pie
+@kindex --pic-executable
+@item -pie
+@itemx --pic-executable
+@cindex position independent executables
+Create a position independent executable. This is currently only supported on
+ELF platforms. Position independent executables are similar to shared
+libraries in that they are relocated by the dynamic linker to the virtual
+address OS chooses for them (which can varry between invocations), like
+normal dynamically linked executables they can be executed and symbols
+defined in the executable cannot be overridden by shared libraries.
+
@kindex -qmagic
@item -qmagic
This option is ignored for Linux compatibility.
@ifset I960
@xref{i960,, @command{ld} and the Intel 960 family}.
@end ifset
-
+@ifset XTENSA
+@xref{Xtensa,, @command{ld} and Xtensa Processors}.
+@end ifset
On some platforms, the @samp{--relax} option performs global
optimizations that become possible when the linker resolves addressing
@item -Tbss @var{org}
@itemx -Tdata @var{org}
@itemx -Ttext @var{org}
-Use @var{org} as the starting address for---respectively---the
-@code{bss}, @code{data}, or the @code{text} segment of the output file.
-@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.
+Same as --section-start, with @code{.bss}, @code{.data} or
+@code{.text} as the @var{sectionname}.
@kindex --verbose
@cindex verbose
@itemx --version-script=@var{version-scriptfile}
Specify the name of a version script to the linker. This is typically
used when creating shared libraries to specify additional information
-about the version heirarchy for the library being created. This option
+about the version hierarchy for the library being created. This option
is only meaningful on ELF platforms which support shared libraries.
@xref{VERSION}.
@c man end
-@subsection Options specific to i386 PE targets
+@subsection Options Specific to i386 PE Targets
@c man begin OPTIONS
@item --add-stdcall-alias
If given, symbols with a stdcall suffix (@@@var{nn}) will be exported
as-is and also with the suffix stripped.
+[This option is specific to the i386 PE targeted port of the linker]
@kindex --base-file
@item --base-file @var{file}
Use @var{file} as the name of a file in which to save the base
addresses of all the relocations needed for generating DLLs with
@file{dlltool}.
+[This is an i386 PE specific option]
@kindex --dll
@item --dll
Create a DLL instead of a regular executable. You may also use
@option{-shared} or specify a @code{LIBRARY} in a given @code{.def}
file.
+[This option is specific to the i386 PE targeted port of the linker]
@kindex --enable-stdcall-fixup
@kindex --disable-stdcall-fixup
@item --enable-stdcall-fixup
@itemx --disable-stdcall-fixup
If the link finds a symbol that it cannot resolve, it will attempt to
-do "fuzzy linking" by looking for another defined symbol that differs
+do ``fuzzy linking'' by looking for another defined symbol that differs
only in the format of the symbol name (cdecl vs stdcall) and will
resolve that symbol by linking to the match. For example, the
undefined symbol @code{_foo} might be linked to the function
feature is fully enabled and warnings are not printed. If you specify
@option{--disable-stdcall-fixup}, this feature is disabled and such
mismatches are considered to be errors.
+[This option is specific to the i386 PE targeted port of the linker]
@cindex DLLs, creating
@kindex --export-all-symbols
@code{_fmode}, @code{_impure_ptr}, @code{cygwin_attach_dll},
@code{cygwin_premain0}, @code{cygwin_premain1}, @code{cygwin_premain2},
@code{cygwin_premain3}, and @code{environ}.
+[This option is specific to the i386 PE targeted port of the linker]
@kindex --exclude-symbols
@item --exclude-symbols @var{symbol},@var{symbol},...
Specifies a list of symbols which should not be automatically
exported. The symbol names may be delimited by commas or colons.
+[This option is specific to the i386 PE targeted port of the linker]
+
+@kindex --exclude-libs
+@item --exclude-libs @var{lib},@var{lib},...
+Specifies a list of archive libraries from which symbols should not be automatically
+exported. The library names may be delimited by commas or colons. Specifying
+@code{--exclude-libs ALL} excludes symbols in all archive libraries from
+automatic export. Symbols explicitly listed in a .def file are still exported,
+regardless of this option.
+[This option is specific to the i386 PE targeted port of the linker]
@kindex --file-alignment
@item --file-alignment
Specify the file alignment. Sections in the file will always begin at
file offsets which are multiples of this number. This defaults to
512.
+[This option is specific to the i386 PE targeted port of the linker]
@cindex heap size
@kindex --heap
Specify the amount of memory to reserve (and optionally commit) to be
used as heap for this program. The default is 1Mb reserved, 4K
committed.
+[This option is specific to the i386 PE targeted port of the linker]
@cindex image base
@kindex --image-base
your dlls, each should have a unique base address and not overlap any
other dlls. The default is 0x400000 for executables, and 0x10000000
for dlls.
+[This option is specific to the i386 PE targeted port of the linker]
@kindex --kill-at
@item --kill-at
If given, the stdcall suffixes (@@@var{nn}) will be stripped from
symbols before they are exported.
+[This option is specific to the i386 PE targeted port of the linker]
@kindex --major-image-version
@item --major-image-version @var{value}
-Sets the major number of the "image version". Defaults to 1.
+Sets the major number of the ``image version''. Defaults to 1.
+[This option is specific to the i386 PE targeted port of the linker]
@kindex --major-os-version
@item --major-os-version @var{value}
-Sets the major number of the "os version". Defaults to 4.
+Sets the major number of the ``os version''. Defaults to 4.
+[This option is specific to the i386 PE targeted port of the linker]
@kindex --major-subsystem-version
@item --major-subsystem-version @var{value}
-Sets the major number of the "subsystem version". Defaults to 4.
+Sets the major number of the ``subsystem version''. Defaults to 4.
+[This option is specific to the i386 PE targeted port of the linker]
@kindex --minor-image-version
@item --minor-image-version @var{value}
-Sets the minor number of the "image version". Defaults to 0.
+Sets the minor number of the ``image version''. Defaults to 0.
+[This option is specific to the i386 PE targeted port of the linker]
@kindex --minor-os-version
@item --minor-os-version @var{value}
-Sets the minor number of the "os version". Defaults to 0.
+Sets the minor number of the ``os version''. Defaults to 0.
+[This option is specific to the i386 PE targeted port of the linker]
@kindex --minor-subsystem-version
@item --minor-subsystem-version @var{value}
-Sets the minor number of the "subsystem version". Defaults to 0.
+Sets the minor number of the ``subsystem version''. Defaults to 0.
+[This option is specific to the i386 PE targeted port of the linker]
@cindex DEF files, creating
@cindex DLLs, creating
(which should be called @code{*.def}) may be used to create an import
library with @code{dlltool} or may be used as a reference to
automatically or implicitly exported symbols.
+[This option is specific to the i386 PE targeted port of the linker]
@cindex DLLs, creating
@kindex --out-implib
may be used to link clients against the generated DLL; this behavior
makes it possible to skip a separate @code{dlltool} import library
creation step.
+[This option is specific to the i386 PE targeted port of the linker]
@kindex --enable-auto-image-base
@item --enable-auto-image-base
from the dllname to create unique image bases for each DLL, in-memory
collisions and relocations which can delay program execution are
avoided.
+[This option is specific to the i386 PE targeted port of the linker]
@kindex --disable-auto-image-base
@item --disable-auto-image-base
Do not automatically generate a unique image base. If there is no
user-specified image base (@code{--image-base}) then use the platform
default.
+[This option is specific to the i386 PE targeted port of the linker]
@cindex DLLs, linking to
@kindex --dll-search-prefix
@item --dll-search-prefix @var{string}
-When linking dynamically to a dll without an import library, i
+When linking dynamically to a dll without an import library,
search for @code{<string><basename>.dll} in preference to
@code{lib<basename>.dll}. This behavior allows easy distinction
between DLLs built for the various "subplatforms": native, cygwin,
uwin, pw, etc. For instance, cygwin DLLs typically use
@code{--dll-search-prefix=cyg}.
+[This option is specific to the i386 PE targeted port of the linker]
@kindex --enable-auto-import
@item --enable-auto-import
Do sophisticated linking of @code{_symbol} to @code{__imp__symbol} for
DATA imports from DLLs, and create the necessary thunking symbols when
-building the DLLs with those DATA exports. This generally will 'just
-work' -- but sometimes you may see this message:
+building the import libraries with those DATA exports. This generally
+will 'just work' -- but sometimes you may see this message:
"variable '<var>' can't be auto-imported. Please read the
documentation for ld's @code{--enable-auto-import} for details."
There are several ways to address this difficulty, regardless of the
data type of the exported variable:
-One solution is to force one of the 'constants' to be a variable --
+One way is to use --enable-runtime-pseudo-reloc switch. This leaves the task
+of adjusting references in your client code for runtime environment, so
+this method works only when runtime environtment supports this feature.
+
+A second solution is to force one of the 'constants' to be a variable --
that is, unknown and un-optimizable at compile time. For arrays,
there are two possibilities: a) make the indexee (the array's address)
a variable, or b) make the 'constant' index a variable. Thus:
@{ volatile long long * local_ll=&extern_ll; *local_ll @}
@end example
-A second method of dealing with this difficulty is to abandon
+A third method of dealing with this difficulty is to abandon
'auto-import' for the offending symbol and mark it with
@code{__declspec(dllimport)}. However, in practice that
requires using compile-time #defines to indicate whether you are
@}
@end example
-A third way to avoid this problem is to re-code your
+A fourth way to avoid this problem is to re-code your
library to use a functional interface rather than a data interface
for the offending variables (e.g. set_foo() and get_foo() accessor
functions).
+[This option is specific to the i386 PE targeted port of the linker]
@kindex --disable-auto-import
@item --disable-auto-import
Do not attempt to do sophisticalted linking of @code{_symbol} to
@code{__imp__symbol} for DATA imports from DLLs.
+[This option is specific to the i386 PE targeted port of the linker]
+
+@kindex --enable-runtime-pseudo-reloc
+@item --enable-runtime-pseudo-reloc
+If your code contains expressions described in --enable-auto-import section,
+that is, DATA imports from DLL with non-zero offset, this switch will create
+a vector of 'runtime pseudo relocations' which can be used by runtime
+environment to adjust references to such data in your client code.
+[This option is specific to the i386 PE targeted port of the linker]
+
+@kindex --disable-runtime-pseudo-reloc
+@item --disable-runtime-pseudo-reloc
+Do not create pseudo relocations for non-zero offset DATA imports from
+DLLs. This is the default.
+[This option is specific to the i386 PE targeted port of the linker]
@kindex --enable-extra-pe-debug
@item --enable-extra-pe-debug
Show additional debug info related to auto-import symbol thunking.
+[This option is specific to the i386 PE targeted port of the linker]
@kindex --section-alignment
@item --section-alignment
Sets the section alignment. Sections in memory will always begin at
addresses which are a multiple of this number. Defaults to 0x1000.
+[This option is specific to the i386 PE targeted port of the linker]
@cindex stack size
@kindex --stack
Specify the amount of memory to reserve (and optionally commit) to be
used as stack for this program. The default is 2Mb reserved, 4K
committed.
+[This option is specific to the i386 PE targeted port of the linker]
@kindex --subsystem
@item --subsystem @var{which}
legal values for @var{which} are @code{native}, @code{windows},
@code{console}, and @code{posix}. You may optionally set the
subsystem version also.
+[This option is specific to the i386 PE targeted port of the linker]
@end table
@c man begin ENVIRONMENT
You can change the behavior of @command{ld} with the environment variables
-@code{GNUTARGET}, @code{LDEMULATION}, and @code{COLLECT_NO_DEMANGLE}.
+@ifclear SingleFormat
+@code{GNUTARGET},
+@end ifclear
+@code{LDEMULATION} and @code{COLLECT_NO_DEMANGLE}.
+@ifclear SingleFormat
@kindex GNUTARGET
@cindex default input format
@code{GNUTARGET} determines the input-file object format if you don't
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 ifclear
@kindex LDEMULATION
@cindex default emulation
@end menu
@node Entry Point
-@subsection Setting the entry point
+@subsection Setting the Entry Point
@kindex ENTRY(@var{symbol})
@cindex start of execution
@cindex first instruction
@end itemize
@node File Commands
-@subsection Commands dealing with files
+@subsection Commands Dealing with Files
@cindex linker script file commands
Several linker script commands deal with files.
In fact, if you like, you can list all of your input files in the linker
script, and then invoke the linker with nothing but a @samp{-T} option.
-The linker will first try to open the file in the current directory. If
-it is not found, the linker will search through the archive library
-search path. See the description of @samp{-L} in @ref{Options,,Command
-Line Options}.
+In case a @dfn{sysroot prefix} is configured, and the filename starts
+with the @samp{/} character, and the script being processed was
+located inside the @dfn{sysroot prefix}, the filename will be looked
+for in the @dfn{sysroot prefix}. Otherwise, the linker will try to
+open the file in the current directory. If it is not found, the
+linker will search through the archive library search path. See the
+description of @samp{-L} in @ref{Options,,Command Line Options}.
If you use @samp{INPUT (-l@var{file})}, @command{ld} will transform the
name to @code{lib@var{file}.a}, as with the command line argument
@ifclear SingleFormat
@node Format Commands
-@subsection Commands dealing with object file formats
+@subsection Commands Dealing with Object File Formats
A couple of linker script commands deal with object file formats.
@table @code
@cindex output file format in linker script
The @code{OUTPUT_FORMAT} command names the BFD format to use for the
output file (@pxref{BFD}). Using @code{OUTPUT_FORMAT(@var{bfdname})} is
-exactly like using @samp{-oformat @var{bfdname}} on the command line
+exactly like using @samp{--oformat @var{bfdname}} on the command line
(@pxref{Options,,Command Line Options}). If both are used, the command
line option takes precedence.
@end ifclear
@node Miscellaneous Commands
-@subsection Other linker script commands
+@subsection Other Linker Script Commands
There are a few other linker scripts commands.
@table @code
linker will use the definition in the linker script.
@node SECTIONS
-@section SECTIONS command
+@section SECTIONS Command
@kindex SECTIONS
The @code{SECTIONS} command tells the linker how to map input sections
into output sections, and how to place the output sections in memory.
@end menu
@node Output Section Description
-@subsection Output section description
+@subsection Output Section Description
The full description of an output section looks like this:
@smallexample
@group
@end itemize
@node Output Section Name
-@subsection Output section name
+@subsection Output Section Name
@cindex name, section
@cindex section name
The name of the output section is @var{section}. @var{section} must
Discarding}.
@node Output Section Address
-@subsection Output section address
+@subsection Output Section Description
@cindex address, section
@cindex section address
The @var{address} is an expression for the VMA (the virtual memory
location counter.
@node Input Section
-@subsection Input section description
+@subsection Input Section Description
@cindex input sections
@cindex mapping input sections to output sections
The most common output section command is an input section description.
@end menu
@node Input Section Basics
-@subsubsection Input section basics
+@subsubsection Input Section Basics
@cindex input section basics
An input section description consists of a file name optionally followed
by a list of section names in parentheses.
the archive search path.
@node Input Section Wildcards
-@subsubsection Input section wildcard patterns
+@subsubsection Input Section Wildcard Patterns
@cindex input section wildcards
@cindex wildcard file name patterns
@cindex file name wildcard patterns
@end smallexample
@node Input Section Common
-@subsubsection Input section for common symbols
+@subsubsection Input Section for Common Symbols
@cindex common symbol placement
@cindex uninitialized data placement
A special notation is needed for common symbols, because in many object
@samp{*(COMMON)}.
@node Input Section Keep
-@subsubsection Input section and garbage collection
+@subsubsection Input Section and Garbage Collection
@cindex KEEP
@cindex garbage collection
When link-time garbage collection is in use (@samp{--gc-sections}),
@code{KEEP(SORT(*)(.ctors))}.
@node Input Section Example
-@subsubsection Input section example
+@subsubsection Input Section Example
The following example is a complete linker script. It tells the linker
to read all of the sections from file @file{all.o} and place them at the
start of output section @samp{outputa} which starts at location
all.o
foo.o (.input1)
@}
+@end group
+@group
outputb :
@{
foo.o (.input2)
foo1.o (.input1)
@}
+@end group
+@group
outputc :
@{
*(.input1)
@end smallexample
@node Output Section Data
-@subsection Output section data
+@subsection Output Section Data
@cindex data
@cindex section data
@cindex output section data
true of, for example, S-records, the value will be stored in the
endianness of the first input object file.
-Note - these commands only work inside a section description and not
+Note---these commands only work inside a section description and not
between them, so the following will produce an error from the linker:
@smallexample
SECTIONS @{@ .text : @{@ *(.text) @}@ LONG(1) .data : @{@ *(.data) @}@ @}@
@end smallexample
The @code{FILL} command is similar to the @samp{=@var{fillexp}} output
-section attribute (@pxref{Output Section Fill}), but it only affects the
+section attribute, but it only affects the
part of the section following the @code{FILL} command, rather than the
entire section. If both are used, the @code{FILL} command takes
-precedence. See (@pxref{Output Section Fill}) for details on the fill
+precedence. @xref{Output Section Fill}, for details on the fill
expression.
@node Output Section Keywords
-@subsection Output section keywords
+@subsection Output Section Keywords
There are a couple of keywords which can appear as output section
commands.
@end table
@node Output Section Discarding
-@subsection Output section discarding
+@subsection Output Section Discarding
@cindex discarding sections
@cindex sections, discarding
@cindex removing sections
section named @samp{/DISCARD/} are not included in the output file.
@node Output Section Attributes
-@subsection Output section attributes
+@subsection Output Section Attributes
@cindex output section attributes
We showed above that the full description of an output section looked
like this:
@end menu
@node Output Section Type
-@subsubsection Output section type
+@subsubsection Output Section Type
Each output section may have a type. The type is a keyword in
parentheses. The following types are defined:
@end smallexample
@node Output Section LMA
-@subsubsection Output section LMA
+@subsubsection Output Section LMA
@kindex AT>@var{lma_region}
@kindex AT(@var{lma})
@cindex load address
@end smallexample
@node Output Section Region
-@subsubsection Output section region
+@subsubsection Output Section Region
@kindex >@var{region}
@cindex section, assigning to memory region
@cindex memory regions and sections
@end smallexample
@node Output Section Phdr
-@subsubsection Output section phdr
+@subsubsection Output Section Phdr
@kindex :@var{phdr}
@cindex section, assigning to program header
@cindex program headers and sections
@end smallexample
@node Output Section Fill
-@subsubsection Output section fill
+@subsubsection Output Section Fill
@kindex =@var{fillexp}
@cindex section fill pattern
@cindex fill pattern, entire section
within the output section (for example, gaps left due to the required
alignment of input sections) will be filled with the value, repeated as
necessary. If the fill expression is a simple hex number, ie. a string
-of hex digit starting with "0x" and without a trailing "k" or "M", then
+of hex digit starting with @samp{0x} and without a trailing @samp{k} or @samp{M}, then
an arbitrarily long sequence of hex digits can be used to specify the
fill pattern; Leading zeros become part of the pattern too. For all
-other cases, including extra parentheses or a unary '+', the fill
+other cases, including extra parentheses or a unary @code{+}, the fill
pattern is the four least significant bytes of the value of the
expression. In all cases, the number is big-endian.
You can also change the fill value with a @code{FILL} command in the
-output section commands; see @ref{Output Section Data}.
+output section commands; (@pxref{Output Section Data}).
Here is a simple example:
@smallexample
@end smallexample
@node Overlay Description
-@subsection Overlay description
+@subsection Overlay Description
@kindex OVERLAY
@cindex overlays
An overlay description provides an easy way to describe sections which
@end smallexample
@node MEMORY
-@section MEMORY command
+@section MEMORY Command
@kindex MEMORY
@cindex memory regions
@cindex regions of memory
When the linker finds a symbol defined in a library which is not
specifically bound to a version node, it will effectively bind it to an
unspecified base version of the library. You can bind all otherwise
-unspecified symbols to a given version node by using @samp{global: *}
+unspecified symbols to a given version node by using @samp{global: *;}
somewhere in the version script.
The names of the version nodes have no specific meaning other than what
won't.
@smallexample
-@{ global: foo; bar; local: *; @}
+@{ global: foo; bar; local: *; @};
@end smallexample
When you link an application against a shared library that has versioned
in the C source file. This renames the function @samp{original_foo} to
be an alias for @samp{foo} bound to the version node @samp{VERS_1.1}.
The @samp{local:} directive can be used to prevent the symbol
-@samp{original_foo} from being exported.
+@samp{original_foo} from being exported. A @samp{.symver} directive
+takes precedence over a version script.
The second GNU extension is to allow multiple versions of the same
function to appear in a given shared library. In this way you can make
If you wish to bind a reference to a specific version of the symbol
within the shared library, you can use the aliases of convenience
-(i.e. @samp{old_foo}), or you can use the @samp{.symver} directive to
+(i.e., @samp{old_foo}), or you can use the @samp{.symver} directive to
specifically bind to an external version of the function in question.
You can also specify the language in the version script:
In addition, you can use the suffixes @code{K} and @code{M} to scale a
constant by
@c TEXI2ROFF-KILL
-@ifinfo
+@ifnottex
@c END TEXI2ROFF-KILL
@code{1024} or @code{1024*1024}
@c TEXI2ROFF-KILL
-@end ifinfo
+@end ifnottex
@tex
${\rm 1024}$ or ${\rm 1024}^2$
@end tex
@c END TEXI2ROFF-KILL
respectively. For example, the following all refer to the same quantity:
@smallexample
- _fourk_1 = 4K;
- _fourk_2 = 4096;
- _fourk_3 = 0x1000;
+_fourk_1 = 4K;
+_fourk_2 = 4096;
+_fourk_3 = 0x1000;
@end smallexample
@node Symbols
specify a symbol which contains odd characters or has the same name as a
keyword by surrounding the symbol name in double quotes:
@smallexample
- "SECTION" = 9;
- "with a space" = "also with a space" + 10;
+"SECTION" = 9;
+"with a space" = "also with a space" + 10;
@end smallexample
Since symbols can contain many non-alphabetic characters, it is safest
@cindex dot inside sections
Note: @code{.} actually refers to the byte offset from the start of the
current containing object. Normally this is the @code{SECTIONS}
-statement, whoes start address is 0, hence @code{.} can be used as an
+statement, whose start address is 0, hence @code{.} can be used as an
absolute address. If @code{.} is used inside a section description
however, it refers to the byte offset from the start of that section,
not an absolute address. Thus in a script like this:
The linker recognizes the standard C set of arithmetic operators, with
the standard bindings and precedence levels:
@c TEXI2ROFF-KILL
-@ifinfo
+@ifnottex
@c END TEXI2ROFF-KILL
@smallexample
precedence associativity Operators Notes
(1) Prefix operators
(2) @xref{Assignments}.
@c TEXI2ROFF-KILL
-@end ifinfo
+@end ifnottex
@tex
\vskip \baselineskip
%"lispnarrowing" is the extra indent used generally for smallexample
@cindex round up location counter
@cindex align location counter
Return the 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
-@smallexample
-(. + @var{exp} - 1) & ~(@var{exp} - 1)
-@end smallexample
-
+boundary.
@code{ALIGN} doesn't change the value of the location counter---it just
does arithmetic on it. Here is an example which aligns the output
@code{.data} section to the next @code{0x2000} byte boundary after the
functionality are not listed.
@menu
-* H8/300:: @code{ld} and the H8/300
-* i960:: @code{ld} and the Intel 960 family
-* ARM:: @code{ld} and the ARM family
-* HPPA ELF32:: @code{ld} and HPPA 32-bit ELF
+@ifset H8300
+* H8/300:: @command{ld} and the H8/300
+@end ifset
+@ifset I960
+* i960:: @command{ld} and the Intel 960 family
+@end ifset
+@ifset ARM
+* ARM:: @command{ld} and the ARM family
+@end ifset
+@ifset HPPA
+* HPPA ELF32:: @command{ld} and HPPA 32-bit ELF
+@end ifset
@ifset MMIX
-* MMIX:: @code{ld} and MMIX
+* MMIX:: @command{ld} and MMIX
+@end ifset
+@ifset MSP430
+* MSP430:: @command{ld} and MSP430
@end ifset
@ifset TICOFF
* TI COFF:: @command{ld} and TI COFF
@end ifset
+@ifset WIN32
+* WIN32:: @command{ld} and WIN32 (cygwin/mingw)
+@end ifset
+@ifset XTENSA
+* Xtensa:: @command{ld} and Xtensa Processors
+@end ifset
@end menu
@end ifset
-@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 ifset
@ifclear GENERIC
-@ifset Hitachi
+@ifset Renesas
@c This stuff is pointless to say unless you're especially concerned
-@c with Hitachi chips; don't enable it for generic case, please.
-@node Hitachi
-@chapter @command{ld} and other Hitachi chips
+@c with Renesas chips; don't enable it for generic case, please.
+@node Renesas
+@chapter @command{ld} and Other Renesas Chips
-@command{ld} also supports the H8/300H, the H8/500, and the Hitachi SH. No
-special features, commands, or command-line options are required for
-these chips.
+@command{ld} also supports the Renesas (formerly Hitachi) H8/300H,
+H8/500, and SH chips. No special features, commands, or command-line
+options are required for these chips.
@end ifset
@end ifclear
@end ifclear
@node i960
-@section @command{ld} and the Intel 960 family
+@section @command{ld} and the Intel 960 Family
@cindex i960 support
@end ifclear
@end ifset
+@ifset ARM
@ifclear GENERIC
@raisesections
@end ifclear
@node ARM
-@section @command{ld}'s support for interworking between ARM and Thumb code
+@section @command{ld}'s Support for Interworking Between ARM and Thumb Code
@cindex ARM interworking support
@kindex --support-old-code
branched to using a BX instruction, and the program will start
executing in Thumb mode straight away.
+@ifclear GENERIC
+@lowersections
+@end ifclear
+@end ifset
+
+@ifset HPPA
+@ifclear GENERIC
+@raisesections
+@end ifclear
+
@node HPPA ELF32
-@section @command{ld} and HPPA 32-bit ELF support
+@section @command{ld} and HPPA 32-bit ELF Support
@cindex HPPA multiple sub-space stubs
@kindex --multi-subspace
When generating a shared library, @command{ld} will by default generate
create a larger group (of one section). If input sections are too
large, it may not be possible for a branch to reach its stub.
+@ifclear GENERIC
+@lowersections
+@end ifclear
+@end ifset
+
@ifset MMIX
+@ifclear GENERIC
+@raisesections
+@end ifclear
+
@node MMIX
@section @code{ld} and MMIX
-For MMIX, there is choice of generating @code{ELF} object files or
+For MMIX, there is a choice of generating @code{ELF} object files or
@code{mmo} object files when linking. The simulator @code{mmix}
understands the @code{mmo} format. The binutils @code{objcopy} utility
can translate between the two formats.
Initial and trailing multiples of zero-valued 32-bit words in a section,
are left out from an mmo file.
+
+@ifclear GENERIC
+@lowersections
+@end ifclear
+@end ifset
+
+@ifset MSP430
+@ifclear GENERIC
+@raisesections
+@end ifclear
+
+@node MSP430
+@section @code{ld} and MSP430
+For the MSP430 it is possible to select the MPU architecture. The flag @samp{-m [mpu type]}
+will select an appropriate linker script for selected MPU type. (To get a list of known MPUs
+just pass @samp{-m help} option to the linker).
+
+@cindex MSP430 extra sections
+The linker will recognize some extra sections which are MSP430 specific:
+
+@table @code
+@item @samp{.vectors}
+Defines a portion of ROM where interrupt vectors located.
+
+@item @samp{.bootloader}
+Defines the bootloader portion of the ROM (if applicable). Any code
+in this section will be uploaded to the MPU.
+
+@item @samp{.infomem}
+Defines an information memory section (if applicable). Any code in
+this section will be uploaded to the MPU.
+
+@item @samp{.infomemnobits}
+This is the same as the @samp{.infomem} section except that any code
+in this section will not be uploaded to the MPU.
+
+@item @samp{.noinit}
+Denotes a portion of RAM located above @samp{.bss} section.
+
+The last two sections are used by gcc.
+@end table
+
+@ifclear GENERIC
+@lowersections
+@end ifclear
@end ifset
@ifset TICOFF
+@ifclear GENERIC
+@raisesections
+@end ifclear
+
@node TI COFF
-@section @command{ld}'s support for various TI COFF versions
+@section @command{ld}'s Support for Various TI COFF Versions
@cindex TI COFF versions
@kindex --format=@var{version}
The @samp{--format} switch allows selection of one of the various
also supported. The TI COFF versions also vary in header byte-order
format; @command{ld} will read any version or byte order, but the output
header format depends on the default specified by the specific target.
+
+@ifclear GENERIC
+@lowersections
+@end ifclear
@end ifset
+@ifset WIN32
+@ifclear GENERIC
+@raisesections
+@end ifclear
+
+@node WIN32
+@section @command{ld} and WIN32 (cygwin/mingw)
+
+This section describes some of the win32 specific @command{ld} issues.
+See @ref{Options,,Command Line Options} for detailed decription of the
+command line options mentioned here.
+
+@table @emph
+@cindex import libraries
+@item import libraries
+The standard Windows linker creates and uses so-called import
+libraries, which contains information for linking to dll's. They are
+regular static archives and are handled as any other static
+archive. The cygwin and mingw ports of @command{ld} have specific
+support for creating such libraries provided with the
+@samp{--out-implib} command line option.
+
+@item exporting DLL symbols
+@cindex exporting DLL symbols
+The cygwin/mingw @command{ld} has several ways to export symbols for dll's.
+
+@table @emph
+@item using auto-export functionality
+@cindex using auto-export functionality
+By default @command{ld} exports symbols with the auto-export functionality,
+which is controlled by the following command line options:
+
+@itemize
+@item --export-all-symbols [This is the default]
+@item --exclude-symbols
+@item --exclude-libs
+@end itemize
+
+If, however, @samp{--export-all-symbols} is not given explicitly on the
+command line, then the default auto-export behavior will be @emph{disabled}
+if either of the following are true:
+
+@itemize
+@item A DEF file is used.
+@item Any symbol in any object file was marked with the __declspec(dllexport) attribute.
+@end itemize
+
+@item using a DEF file
+@cindex using a DEF file
+Another way of exporting symbols is using a DEF file. A DEF file is
+an ASCII file containing definitions of symbols which should be
+exported when a dll is created. Usually it is named @samp{<dll
+name>.def} and is added as any other object file to the linker's
+command line. The file's name must end in @samp{.def} or @samp{.DEF}.
+
+@example
+gcc -o <output> <objectfiles> <dll name>.def
+@end example
+
+Using a DEF file turns off the normal auto-export behavior, unless the
+@samp{--export-all-symbols} option is also used.
+
+Here is an example of a DEF file for a shared library called @samp{xyz.dll}:
+
+@example
+LIBRARY "xyz.dll" BASE=0x10000000
+
+EXPORTS
+foo
+bar
+_bar = bar
+@end example
+
+This example defines a base address and three symbols. The third
+symbol is an alias for the second. For the complete format
+specification see ld/deffilep.y in the binutils sources.
+
+@cindex creating a DEF file
+While linking a shared dll, @command{ld} is able to create a DEF file
+with the @samp{--output-def <file>} command line option.
+
+@item Using decorations
+@cindex Using decorations
+Another way of marking symbols for export is to modify the source code
+itself, so that when building the DLL each symbol to be exported is
+declared as:
+
+@example
+__declspec(dllexport) int a_variable
+__declspec(dllexport) void a_function(int with_args)
+@end example
+
+All such symbols will be exported from the DLL. If, however,
+any of the object files in the DLL contain symbols decorated in
+this way, then the normal auto-export behavior is disabled, unless
+the @samp{--export-all-symbols} option is also used.
+
+Note that object files that wish to access these symbols must @emph{not}
+decorate them with dllexport. Instead, they should use dllimport,
+instead:
+
+@example
+__declspec(dllimport) int a_variable
+__declspec(dllimport) void a_function(int with_args)
+@end example
+
+This complicates the structure of library header files, because
+when included by the library itself the header must declare the
+variables and functions as dllexport, but when included by client
+code the header must declare them as dllimport. There are a number
+of idioms that are typically used to do this; often client code can
+omit the __declspec() declaration completely. See
+@samp{--enable-auto-import} and @samp{automatic data imports} for more
+imformation.
+@end table
+
+@cindex automatic data imports
+@item automatic data imports
+The standard Windows dll format supports data imports from dlls only
+by adding special decorations (dllimport/dllexport), which let the
+compiler produce specific assembler instructions to deal with this
+issue. This increases the effort necessary to port existing Un*x
+code to these platforms, especially for large
+c++ libraries and applications. The auto-import feature, which was
+initially provided by Paul Sokolovsky, allows one to omit the
+decorations to archieve a behavior that conforms to that on POSIX/Un*x
+platforms. This feature is enabled with the @samp{--enable-auto-import}
+command-line option, although it is enabled by default on cygwin/mingw.
+The @samp{--enable-auto-import} option itself now serves mainly to
+suppress any warnings that are ordinarily emitted when linked objects
+trigger the feature's use.
+
+auto-import of variables does not always work flawlessly without
+additional assistance. Sometimes, you will see this message
+
+"variable '<var>' can't be auto-imported. Please read the
+documentation for ld's @code{--enable-auto-import} for details."
+
+The @samp{--enable-auto-import} documentation explains why this error
+occurs, and several methods that can be used to overcome this difficulty.
+One of these methods is the @emph{runtime pseudo-relocs} feature, described
+below.
+
+@cindex runtime pseudo-relocation
+For complex variables imported from DLLs (such as structs or classes),
+object files typically contain a base address for the variable and an
+offset (@emph{addend}) within the variable--to specify a particular
+field or public member, for instance. Unfortunately, the runtime loader used
+in win32 environments is incapable of fixing these references at runtime
+without the additional information supplied by dllimport/dllexport decorations.
+The standard auto-import feature described above is unable to resolve these
+references.
+
+The @samp{--enable-runtime-pseudo-relocs} switch allows these references to
+be resolved without error, while leaving the task of adjusting the references
+themselves (with their non-zero addends) to specialized code provided by the
+runtime environment. Recent versions of the cygwin and mingw environments and
+compilers provide this runtime support; older versions do not. However, the
+support is only necessary on the developer's platform; the compiled result will
+run without error on an older system.
+
+@samp{--enable-runtime-pseudo-relocs} is not the default; it must be explicitly
+enabled as needed.
+
+@cindex direct linking to a dll
+@item direct linking to a dll
+The cygwin/mingw ports of @command{ld} support the direct linking,
+including data symbols, to a dll without the usage of any import
+libraries. This is much faster and uses much less memory than does the
+traditional import library method, expecially when linking large
+libraries or applications. When @command{ld} creates an import lib, each
+function or variable exported from the dll is stored in its own bfd, even
+though a single bfd could contain many exports. The overhead involved in
+storing, loading, and processing so many bfd's is quite large, and explains the
+tremendous time, memory, and storage needed to link against particularly
+large or complex libraries when using import libs.
+
+Linking directly to a dll uses no extra command-line switches other than
+@samp{-L} and @samp{-l}, because @command{ld} already searches for a number
+of names to match each library. All that is needed from the developer's
+perspective is an understanding of this search, in order to force ld to
+select the dll instead of an import library.
+
+
+For instance, when ld is called with the argument @samp{-lxxx} it will attempt
+to find, in the first directory of its search path,
+
+@example
+libxxx.dll.a
+xxx.dll.a
+libxxx.a
+cygxxx.dll (*)
+libxxx.dll
+xxx.dll
+@end example
+
+before moving on to the next directory in the search path.
+
+(*) Actually, this is not @samp{cygxxx.dll} but in fact is @samp{<prefix>xxx.dll},
+where @samp{<prefix>} is set by the @command{ld} option
+@samp{--dll-search-prefix=<prefix>}. In the case of cygwin, the standard gcc spec
+file includes @samp{--dll-search-prefix=cyg}, so in effect we actually search for
+@samp{cygxxx.dll}.
+
+Other win32-based unix environments, such as mingw or pw32, may use other
+@samp{<prefix>}es, although at present only cygwin makes use of this feature. It
+was originally intended to help avoid name conflicts among dll's built for the
+various win32/un*x environments, so that (for example) two versions of a zlib dll
+could coexist on the same machine.
+
+The generic cygwin/mingw path layout uses a @samp{bin} directory for
+applications and dll's and a @samp{lib} directory for the import
+libraries (using cygwin nomenclature):
+
+@example
+bin/
+ cygxxx.dll
+lib/
+ libxxx.dll.a (in case of dll's)
+ libxxx.a (in case of static archive)
+@end example
+
+Linking directly to a dll without using the import library can be
+done two ways:
+
+1. Use the dll directly by adding the @samp{bin} path to the link line
+@example
+gcc -Wl,-verbose -o a.exe -L../bin/ -lxxx
+@end example
+
+However, as the dll's often have version numbers appended to their names
+(@samp{cygncurses-5.dll}) this will often fail, unless one specifies
+@samp{-L../bin -lncurses-5} to include the version. Import libs are generally
+not versioned, and do not have this difficulty.
+
+2. Create a symbolic link from the dll to a file in the @samp{lib}
+directory according to the above mentioned search pattern. This
+should be used to avoid unwanted changes in the tools needed for
+making the app/dll.
+
+@example
+ln -s bin/cygxxx.dll lib/[cyg|lib|]xxx.dll[.a]
+@end example
+
+Then you can link without any make environment changes.
+
+@example
+gcc -Wl,-verbose -o a.exe -L../lib/ -lxxx
+@end example
+
+This technique also avoids the version number problems, because the following is
+perfectly legal
+
+@example
+bin/
+ cygxxx-5.dll
+lib/
+ libxxx.dll.a -> ../bin/cygxxx-5.dll
+@end example
+
+Linking directly to a dll without using an import lib will work
+even when auto-import features are exercised, and even when
+@samp{--enable-runtime-pseudo-relocs} is used.
+
+Given the improvements in speed and memory usage, one might justifiably
+wonder why import libraries are used at all. There are two reasons:
+
+1. Until recently, the link-directly-to-dll functionality did @emph{not}
+work with auto-imported data.
+
+2. Sometimes it is necessary to include pure static objects within the
+import library (which otherwise contains only bfd's for indirection
+symbols that point to the exports of a dll). Again, the import lib
+for the cygwin kernel makes use of this ability, and it is not
+possible to do this without an import lib.
+
+So, import libs are not going away. But the ability to replace
+true import libs with a simple symbolic link to (or a copy of)
+a dll, in most cases, is a useful addition to the suite of tools
+binutils makes available to the win32 developer. Given the
+massive improvements in memory requirements during linking, storage
+requirements, and linking speed, we expect that many developers
+will soon begin to use this feature whenever possible.
+
+@item symbol aliasing
+@table @emph
+@item adding additional names
+Sometimes, it is useful to export symbols with additional names.
+A symbol @samp{foo} will be exported as @samp{foo}, but it can also be
+exported as @samp{_foo} by using special directives in the DEF file
+when creating the dll. This will affect also the optional created
+import library. Consider the following DEF file:
+
+@example
+LIBRARY "xyz.dll" BASE=0x61000000
+
+EXPORTS
+foo
+_foo = foo
+@end example
+
+The line @samp{_foo = foo} maps the symbol @samp{foo} to @samp{_foo}.
+
+Another method for creating a symbol alias is to create it in the
+source code using the "weak" attribute:
+
+@example
+void foo () @{ /* Do something. */; @}
+void _foo () __attribute__ ((weak, alias ("foo")));
+@end example
+
+See the gcc manual for more information about attributes and weak
+symbols.
+
+@item renaming symbols
+Sometimes it is useful to rename exports. For instance, the cygwin
+kernel does this regularly. A symbol @samp{_foo} can be exported as
+@samp{foo} but not as @samp{_foo} by using special directives in the
+DEF file. (This will also affect the import library, if it is
+created). In the following example:
+
+@example
+LIBRARY "xyz.dll" BASE=0x61000000
+
+EXPORTS
+_foo = foo
+@end example
+
+The line @samp{_foo = foo} maps the exported symbol @samp{foo} to
+@samp{_foo}.
+@end table
+
+Note: using a DEF file disables the default auto-export behavior,
+unless the @samp{--export-all-symbols} command line option is used.
+If, however, you are trying to rename symbols, then you should list
+@emph{all} desired exports in the DEF file, including the symbols
+that are not being renamed, and do @emph{not} use the
+@samp{--export-all-symbols} option. If you list only the
+renamed symbols in the DEF file, and use @samp{--export-all-symbols}
+to handle the other symbols, then the both the new names @emph{and}
+the original names for the the renamed symbols will be exported.
+In effect, you'd be aliasing those symbols, not renaming them,
+which is probably not what you wanted.
+@end table
+
@ifclear GENERIC
@lowersections
@end ifclear
+@end ifset
+
+@ifset XTENSA
+@ifclear GENERIC
+@raisesections
+@end ifclear
+
+@node Xtensa
+@section @code{ld} and Xtensa Processors
+
+@cindex Xtensa processors
+The default @command{ld} behavior for Xtensa processors is to interpret
+@code{SECTIONS} commands so that lists of explicitly named sections in a
+specification with a wildcard file will be interleaved when necessary to
+keep literal pools within the range of PC-relative load offsets. For
+example, with the command:
+
+@smallexample
+SECTIONS
+@{
+ .text : @{
+ *(.literal .text)
+ @}
+@}
+@end smallexample
+
+@noindent
+@command{ld} may interleave some of the @code{.literal}
+and @code{.text} sections from different object files to ensure that the
+literal pools are within the range of PC-relative load offsets. A valid
+interleaving might place the @code{.literal} sections from an initial
+group of files followed by the @code{.text} sections of that group of
+files. Then, the @code{.literal} sections from the rest of the files
+and the @code{.text} sections from the rest of the files would follow.
+The non-interleaved order can still be specified as:
+
+@smallexample
+SECTIONS
+@{
+ .text : @{
+ *(.literal) *(.text)
+ @}
+@}
+@end smallexample
+
+@cindex @code{--relax} on Xtensa
+@cindex relaxing on Xtensa
+@kindex --no-relax
+The Xtensa version of @command{ld} enables the @option{--relax} option by
+default to attempt to reduce space in the output image by combining
+literals with identical values. It also provides the
+@option{--no-relax} option to disable this optimization. When enabled,
+the relaxation algorithm ensures that a literal will only be merged with
+another literal when the new merged literal location is within the
+offset range of all of its uses.
+
+The relaxation mechanism will also attempt to optimize
+assembler-generated ``longcall'' sequences of
+@code{L32R}/@code{CALLX@var{n}} when the target is known to fit into a
+@code{CALL@var{n}} instruction encoding. The current optimization
+converts the sequence into @code{NOP}/@code{CALL@var{n}} and removes the
+literal referenced by the @code{L32R} instruction.
+
+@ifclear GENERIC
+@lowersections
+@end ifclear
+@end ifset
@ifclear SingleFormat
@node BFD
@end menu
@node BFD outline
-@section How it works: an outline of BFD
+@section How It Works: An Outline of BFD
@cindex opening object files
@include bfdsumm.texi
@end ifclear
@end menu
@node Bug Criteria
-@section Have you found a bug?
+@section Have You Found a Bug?
@cindex bug criteria
If you are not sure whether you have found a bug, here are some guidelines:
@end itemize
@node Bug Reporting
-@section How to report bugs
+@section How to Report Bugs
@cindex bug reports
@cindex @command{ld} bugs, reporting
Often people omit facts because they think they know what causes the
problem and assume that some details do not matter. Thus, you might
-assume that the name of a symbol you use in an example does not matter.
-Well, probably it does not, but one cannot be sure. Perhaps the bug is
-a stray memory reference which happens to fetch from the location where
-that name is stored in memory; perhaps, if the name were different, the
-contents of that location would fool the linker into doing the right
-thing despite the bug. Play it safe and give a specific, complete
-example. That is the easiest thing for you to do, and the most helpful.
-
-Keep in mind that the purpose of a bug report is to enable us to fix the bug if
-it is new to us. Therefore, always write your bug reports on the assumption
-that the bug has not been reported previously.
+assume that the name of a symbol you use in an example does not
+matter. Well, probably it does not, but one cannot be sure. Perhaps
+the bug is a stray memory reference which happens to fetch from the
+location where that name is stored in memory; perhaps, if the name
+were different, the contents of that location would fool the linker
+into doing the right thing despite the bug. Play it safe and give a
+specific, complete example. That is the easiest thing for you to do,
+and the most helpful.
+
+Keep in mind that the purpose of a bug report is to enable us to fix
+the bug if it is new to us. Therefore, always write your bug reports
+on the assumption that the bug has not been reported previously.
Sometimes people give a few sketchy facts and ask, ``Does this ring a
-bell?'' Those bug reports are useless, and we urge everyone to
-@emph{refuse to respond to them} except to chide the sender to report
-bugs properly.
+bell?'' This cannot help us fix a bug, so it is basically useless. We
+respond by asking for enough details to enable us to investigate.
+You might as well expedite matters by sending them to begin with.
To enable us to fix the bug, you should include all these things:
@item
A complete input file, or set of input files, that will reproduce the
-bug. It is generally most helpful to send the actual object files,
-uuencoded if necessary to get them through the mail system. Making them
-available for anonymous FTP is not as good, but may be the only
-reasonable choice for large object files.
+bug. It is generally most helpful to send the actual object files
+provided that they are reasonably small. Say no more than 10K. For
+bigger files you can either make them available by FTP or HTTP or else
+state that you are willing to send the object file(s) to whomever
+requests them. (Note - your email will be going to a mailing list, so
+we do not want to clog it up with large attachments). But small
+attachments are best.
If the source files were assembled using @code{gas} or compiled using
@code{gcc}, then it may be OK to send the source files rather than the
@var{secname}, only the @emph{first} sets the start address.
@end table
-@node GNU Free Documentation License
-@appendix GNU Free Documentation License
-@cindex GNU Free Documentation License
-
- GNU Free Documentation License
-
- Version 1.1, March 2000
-
- Copyright (C) 2000 Free Software Foundation, Inc.
- 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
-
- Everyone is permitted to copy and distribute verbatim copies
- of this license document, but changing it is not allowed.
-
-
-0. PREAMBLE
-
-The purpose of this License is to make a manual, textbook, or other
-written document "free" in the sense of freedom: to assure everyone
-the effective freedom to copy and redistribute it, with or without
-modifying it, either commercially or noncommercially. Secondarily,
-this License preserves for the author and publisher a way to get
-credit for their work, while not being considered responsible for
-modifications made by others.
-
-This License is a kind of "copyleft", which means that derivative
-works of the document must themselves be free in the same sense. It
-complements the GNU General Public License, which is a copyleft
-license designed for free software.
-
-We have designed this License in order to use it for manuals for free
-software, because free software needs free documentation: a free
-program should come with manuals providing the same freedoms that the
-software does. But this License is not limited to software manuals;
-it can be used for any textual work, regardless of subject matter or
-whether it is published as a printed book. We recommend this License
-principally for works whose purpose is instruction or reference.
-
-
-1. APPLICABILITY AND DEFINITIONS
-
-This License applies to any manual or other work that contains a
-notice placed by the copyright holder saying it can be distributed
-under the terms of this License. The "Document", below, refers to any
-such manual or work. Any member of the public is a licensee, and is
-addressed as "you".
-
-A "Modified Version" of the Document means any work containing the
-Document or a portion of it, either copied verbatim, or with
-modifications and/or translated into another language.
-
-A "Secondary Section" is a named appendix or a front-matter section of
-the Document that deals exclusively with the relationship of the
-publishers or authors of the Document to the Document's overall subject
-(or to related matters) and contains nothing that could fall directly
-within that overall subject. (For example, if the Document is in part a
-textbook of mathematics, a Secondary Section may not explain any
-mathematics.) The relationship could be a matter of historical
-connection with the subject or with related matters, or of legal,
-commercial, philosophical, ethical or political position regarding
-them.
-
-The "Invariant Sections" are certain Secondary Sections whose titles
-are designated, as being those of Invariant Sections, in the notice
-that says that the Document is released under this License.
-
-The "Cover Texts" are certain short passages of text that are listed,
-as Front-Cover Texts or Back-Cover Texts, in the notice that says that
-the Document is released under this License.
-
-A "Transparent" copy of the Document means a machine-readable copy,
-represented in a format whose specification is available to the
-general public, whose contents can be viewed and edited directly and
-straightforwardly with generic text editors or (for images composed of
-pixels) generic paint programs or (for drawings) some widely available
-drawing editor, and that is suitable for input to text formatters or
-for automatic translation to a variety of formats suitable for input
-to text formatters. A copy made in an otherwise Transparent file
-format whose markup has been designed to thwart or discourage
-subsequent modification by readers is not Transparent. A copy that is
-not "Transparent" is called "Opaque".
-
-Examples of suitable formats for Transparent copies include plain
-ASCII without markup, Texinfo input format, LaTeX input format, SGML
-or XML using a publicly available DTD, and standard-conforming simple
-HTML designed for human modification. Opaque formats include
-PostScript, PDF, proprietary formats that can be read and edited only
-by proprietary word processors, SGML or XML for which the DTD and/or
-processing tools are not generally available, and the
-machine-generated HTML produced by some word processors for output
-purposes only.
-
-The "Title Page" means, for a printed book, the title page itself,
-plus such following pages as are needed to hold, legibly, the material
-this License requires to appear in the title page. For works in
-formats which do not have any title page as such, "Title Page" means
-the text near the most prominent appearance of the work's title,
-preceding the beginning of the body of the text.
-
-
-2. VERBATIM COPYING
-
-You may copy and distribute the Document in any medium, either
-commercially or noncommercially, provided that this License, the
-copyright notices, and the license notice saying this License applies
-to the Document are reproduced in all copies, and that you add no other
-conditions whatsoever to those of this License. You may not use
-technical measures to obstruct or control the reading or further
-copying of the copies you make or distribute. However, you may accept
-compensation in exchange for copies. If you distribute a large enough
-number of copies you must also follow the conditions in section 3.
-
-You may also lend copies, under the same conditions stated above, and
-you may publicly display copies.
-
-
-3. COPYING IN QUANTITY
-
-If you publish printed copies of the Document numbering more than 100,
-and the Document's license notice requires Cover Texts, you must enclose
-the copies in covers that carry, clearly and legibly, all these Cover
-Texts: Front-Cover Texts on the front cover, and Back-Cover Texts on
-the back cover. Both covers must also clearly and legibly identify
-you as the publisher of these copies. The front cover must present
-the full title with all words of the title equally prominent and
-visible. You may add other material on the covers in addition.
-Copying with changes limited to the covers, as long as they preserve
-the title of the Document and satisfy these conditions, can be treated
-as verbatim copying in other respects.
-
-If the required texts for either cover are too voluminous to fit
-legibly, you should put the first ones listed (as many as fit
-reasonably) on the actual cover, and continue the rest onto adjacent
-pages.
-
-If you publish or distribute Opaque copies of the Document numbering
-more than 100, you must either include a machine-readable Transparent
-copy along with each Opaque copy, or state in or with each Opaque copy
-a publicly-accessible computer-network location containing a complete
-Transparent copy of the Document, free of added material, which the
-general network-using public has access to download anonymously at no
-charge using public-standard network protocols. If you use the latter
-option, you must take reasonably prudent steps, when you begin
-distribution of Opaque copies in quantity, to ensure that this
-Transparent copy will remain thus accessible at the stated location
-until at least one year after the last time you distribute an Opaque
-copy (directly or through your agents or retailers) of that edition to
-the public.
-
-It is requested, but not required, that you contact the authors of the
-Document well before redistributing any large number of copies, to give
-them a chance to provide you with an updated version of the Document.
-
-
-4. MODIFICATIONS
-
-You may copy and distribute a Modified Version of the Document under
-the conditions of sections 2 and 3 above, provided that you release
-the Modified Version under precisely this License, with the Modified
-Version filling the role of the Document, thus licensing distribution
-and modification of the Modified Version to whoever possesses a copy
-of it. In addition, you must do these things in the Modified Version:
-
-A. Use in the Title Page (and on the covers, if any) a title distinct
- from that of the Document, and from those of previous versions
- (which should, if there were any, be listed in the History section
- of the Document). You may use the same title as a previous version
- if the original publisher of that version gives permission.
-B. List on the Title Page, as authors, one or more persons or entities
- responsible for authorship of the modifications in the Modified
- Version, together with at least five of the principal authors of the
- Document (all of its principal authors, if it has less than five).
-C. State on the Title page the name of the publisher of the
- Modified Version, as the publisher.
-D. Preserve all the copyright notices of the Document.
-E. Add an appropriate copyright notice for your modifications
- adjacent to the other copyright notices.
-F. Include, immediately after the copyright notices, a license notice
- giving the public permission to use the Modified Version under the
- terms of this License, in the form shown in the Addendum below.
-G. Preserve in that license notice the full lists of Invariant Sections
- and required Cover Texts given in the Document's license notice.
-H. Include an unaltered copy of this License.
-I. Preserve the section entitled "History", and its title, and add to
- it an item stating at least the title, year, new authors, and
- publisher of the Modified Version as given on the Title Page. If
- there is no section entitled "History" in the Document, create one
- stating the title, year, authors, and publisher of the Document as
- given on its Title Page, then add an item describing the Modified
- Version as stated in the previous sentence.
-J. Preserve the network location, if any, given in the Document for
- public access to a Transparent copy of the Document, and likewise
- the network locations given in the Document for previous versions
- it was based on. These may be placed in the "History" section.
- You may omit a network location for a work that was published at
- least four years before the Document itself, or if the original
- publisher of the version it refers to gives permission.
-K. In any section entitled "Acknowledgements" or "Dedications",
- preserve the section's title, and preserve in the section all the
- substance and tone of each of the contributor acknowledgements
- and/or dedications given therein.
-L. Preserve all the Invariant Sections of the Document,
- unaltered in their text and in their titles. Section numbers
- or the equivalent are not considered part of the section titles.
-M. Delete any section entitled "Endorsements". Such a section
- may not be included in the Modified Version.
-N. Do not retitle any existing section as "Endorsements"
- or to conflict in title with any Invariant Section.
-
-If the Modified Version includes new front-matter sections or
-appendices that qualify as Secondary Sections and contain no material
-copied from the Document, you may at your option designate some or all
-of these sections as invariant. To do this, add their titles to the
-list of Invariant Sections in the Modified Version's license notice.
-These titles must be distinct from any other section titles.
-
-You may add a section entitled "Endorsements", provided it contains
-nothing but endorsements of your Modified Version by various
-parties--for example, statements of peer review or that the text has
-been approved by an organization as the authoritative definition of a
-standard.
-
-You may add a passage of up to five words as a Front-Cover Text, and a
-passage of up to 25 words as a Back-Cover Text, to the end of the list
-of Cover Texts in the Modified Version. Only one passage of
-Front-Cover Text and one of Back-Cover Text may be added by (or
-through arrangements made by) any one entity. If the Document already
-includes a cover text for the same cover, previously added by you or
-by arrangement made by the same entity you are acting on behalf of,
-you may not add another; but you may replace the old one, on explicit
-permission from the previous publisher that added the old one.
-
-The author(s) and publisher(s) of the Document do not by this License
-give permission to use their names for publicity for or to assert or
-imply endorsement of any Modified Version.
-
-
-5. COMBINING DOCUMENTS
-
-You may combine the Document with other documents released under this
-License, under the terms defined in section 4 above for modified
-versions, provided that you include in the combination all of the
-Invariant Sections of all of the original documents, unmodified, and
-list them all as Invariant Sections of your combined work in its
-license notice.
-
-The combined work need only contain one copy of this License, and
-multiple identical Invariant Sections may be replaced with a single
-copy. If there are multiple Invariant Sections with the same name but
-different contents, make the title of each such section unique by
-adding at the end of it, in parentheses, the name of the original
-author or publisher of that section if known, or else a unique number.
-Make the same adjustment to the section titles in the list of
-Invariant Sections in the license notice of the combined work.
-
-In the combination, you must combine any sections entitled "History"
-in the various original documents, forming one section entitled
-"History"; likewise combine any sections entitled "Acknowledgements",
-and any sections entitled "Dedications". You must delete all sections
-entitled "Endorsements."
-
-
-6. COLLECTIONS OF DOCUMENTS
-
-You may make a collection consisting of the Document and other documents
-released under this License, and replace the individual copies of this
-License in the various documents with a single copy that is included in
-the collection, provided that you follow the rules of this License for
-verbatim copying of each of the documents in all other respects.
-
-You may extract a single document from such a collection, and distribute
-it individually under this License, provided you insert a copy of this
-License into the extracted document, and follow this License in all
-other respects regarding verbatim copying of that document.
-
-
-7. AGGREGATION WITH INDEPENDENT WORKS
-
-A compilation of the Document or its derivatives with other separate
-and independent documents or works, in or on a volume of a storage or
-distribution medium, does not as a whole count as a Modified Version
-of the Document, provided no compilation copyright is claimed for the
-compilation. Such a compilation is called an "aggregate", and this
-License does not apply to the other self-contained works thus compiled
-with the Document, on account of their being thus compiled, if they
-are not themselves derivative works of the Document.
-
-If the Cover Text requirement of section 3 is applicable to these
-copies of the Document, then if the Document is less than one quarter
-of the entire aggregate, the Document's Cover Texts may be placed on
-covers that surround only the Document within the aggregate.
-Otherwise they must appear on covers around the whole aggregate.
-
-
-8. TRANSLATION
-
-Translation is considered a kind of modification, so you may
-distribute translations of the Document under the terms of section 4.
-Replacing Invariant Sections with translations requires special
-permission from their copyright holders, but you may include
-translations of some or all Invariant Sections in addition to the
-original versions of these Invariant Sections. You may include a
-translation of this License provided that you also include the
-original English version of this License. In case of a disagreement
-between the translation and the original English version of this
-License, the original English version will prevail.
-
-
-9. TERMINATION
-
-You may not copy, modify, sublicense, or distribute the Document except
-as expressly provided for under this License. Any other attempt to
-copy, modify, sublicense or distribute the Document is void, and will
-automatically terminate your rights under this License. However,
-parties who have received copies, or rights, from you under this
-License will not have their licenses terminated so long as such
-parties remain in full compliance.
-
-
-10. FUTURE REVISIONS OF THIS LICENSE
-
-The Free Software Foundation may publish new, revised versions
-of the GNU Free Documentation License from time to time. Such new
-versions will be similar in spirit to the present version, but may
-differ in detail to address new problems or concerns. See
-http://www.gnu.org/copyleft/.
-
-Each version of the License is given a distinguishing version number.
-If the Document specifies that a particular numbered version of this
-License "or any later version" applies to it, you have the option of
-following the terms and conditions either of that specified version or
-of any later version that has been published (not as a draft) by the
-Free Software Foundation. If the Document does not specify a version
-number of this License, you may choose any version ever published (not
-as a draft) by the Free Software Foundation.
-
-
-ADDENDUM: How to use this License for your documents
-
-To use this License in a document you have written, include a copy of
-the License in the document and put the following copyright and
-license notices just after the title page:
-
-@smallexample
- Copyright (c) YEAR YOUR NAME.
- Permission is granted to copy, distribute and/or modify this document
- under the terms of the GNU Free Documentation License, Version 1.1
- or any later version published by the Free Software Foundation;
- with the Invariant Sections being LIST THEIR TITLES, with the
- Front-Cover Texts being LIST, and with the Back-Cover Texts being LIST.
- A copy of the license is included in the section entitled "GNU
- Free Documentation License".
-@end smallexample
-
-If you have no Invariant Sections, write "with no Invariant Sections"
-instead of saying which ones are invariant. If you have no
-Front-Cover Texts, write "no Front-Cover Texts" instead of
-"Front-Cover Texts being LIST"; likewise for Back-Cover Texts.
-
-If your document contains nontrivial examples of program code, we
-recommend releasing these examples in parallel under your choice of
-free software license, such as the GNU General Public License,
-to permit their use in free software.
+@include fdl.texi
@node Index
@unnumbered Index