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man_ld
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LD(1) GNU Development Tools LD(1)
NAME
ld - The GNU linker
SYNOPSIS
ld [options] objfile ...
DESCRIPTION
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 ld.
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 man page does not describe the command language; see the ld entry in "info" for
full details on the command language and on other aspects of the GNU linker.
This version of ld uses the general purpose BFD libraries to operate on object files.
This allows ld to read, combine, and write object files in many different formats---for
example, COFF or "a.out". Different formats may be linked together to produce any
available kind of object file.
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, ld continues executing, allowing you to
identify other errors (or, in some cases, to get an output file in spite of the error).
The GNU linker 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.
OPTIONS
The linker supports a plethora of command-line options, but in actual practice few of
them are used in any particular context. For instance, a frequent use of ld is to link
standard Unix object files on a standard, supported Unix system. On such a system, to
link a file "hello.o":
ld -o <output> /lib/crt0.o hello.o -lc
This tells ld to produce a file called output as the result of linking the file
"/lib/crt0.o" with "hello.o" and the library "libc.a", which will come from the standard
search directories. (See the discussion of the -l option below.)
Some of the command-line options to ld may be specified at any point in the command
line. However, options which refer to files, such as -l or -T, cause the file to be
read at the point at which the option appears in the command line, relative to the
object files and other file options. Repeating non-file 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 that option. Options which may be
meaningfully specified more than once are noted in the descriptions below.
Non-option arguments are object files or archives which are to be linked together. They
may follow, precede, or be mixed in with command-line options, except that an object
file argument may not be placed between an option and its argument.
Usually the linker is invoked with at least one object file, but you can specify other
forms of binary input files using -l, -R, and the script command language. If no binary
input files at all are specified, the linker does not produce any output, and issues the
message No input files.
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 -T). This
feature permits the linker to link against a file which appears to be an object or an
archive, but actually merely defines some symbol values, or uses "INPUT" or "GROUP" to
load other objects. Specifying a script in this way merely augments the main linker
script, with the extra commands placed after the main script; use the -T option to
replace the default linker script entirely, but note the effect of the "INSERT" command.
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.
For options whose names are multiple letters, either one dash or two can precede the
option name; for example, -trace-symbol and --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 preceded by two dashes. This is to reduce confusion with the -o option. So
for example -omagic sets the output file name to magic whereas --omagic sets the NMAGIC
flag on the output.
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, --trace-symbol foo and --trace-symbol=foo are equivalent.
Unique abbreviations of the names of multiple-letter options are accepted.
Note---if the linker is being invoked indirectly, via a compiler driver (e.g. gcc) then
all the linker command line options should be prefixed by -Wl, (or whatever is
appropriate for the particular compiler driver) like this:
gcc -Wl,--start-group foo.o bar.o -Wl,--end-group
This is important, because otherwise the compiler driver program may silently drop the
linker options, resulting in a bad link. Confusion may also arise when passing options
that require values through a driver, as the use of a space between option and argument
acts as a separator, and causes the driver to pass only the option to the linker and the
argument to the compiler. In this case, it is simplest to use the joined forms of both
single- and multiple-letter options, such as:
gcc foo.o bar.o -Wl,-eENTRY -Wl,-Map=a.map
Here is a table of the generic command line switches accepted by the GNU linker:
@file
Read command-line options from file. The options read are inserted in place of the
original @file option. If file does not exist, or cannot be read, then the option
will be treated literally, and not removed.
Options in file are separated by whitespace. A whitespace character may be included
in an option by surrounding the entire option in either single or double quotes.
Any character (including a backslash) may be included by prefixing the character to
be included with a backslash. The file may itself contain additional @file options;
any such options will be processed recursively.
-a keyword
This option is supported for HP/UX compatibility. The keyword argument must be one
of the strings archive, shared, or default. -aarchive is functionally equivalent to
-Bstatic, and the other two keywords are functionally equivalent to -Bdynamic. This
option may be used any number of times.
--audit AUDITLIB
Adds AUDITLIB to the "DT_AUDIT" entry of the dynamic section. AUDITLIB is not
checked for existence, nor will it use the DT_SONAME specified in the library. If
specified multiple times "DT_AUDIT" will contain a colon separated list of audit
interfaces to use. If the linker finds an object with an audit entry while searching
for shared libraries, it will add a corresponding "DT_DEPAUDIT" entry in the output
file. This option is only meaningful on ELF platforms supporting the rtld-audit
interface.
-A architecture
--architecture=architecture
In the current release of ld, this option is useful only for the Intel 960 family of
architectures. In that ld configuration, the architecture argument identifies the
particular architecture in the 960 family, enabling some safeguards and modifying
the archive-library search path.
Future releases of ld may support similar functionality for other architecture
families.
-b input-format
--format=input-format
ld may be configured to support more than one kind of object file. If your ld is
configured this way, you can use the -b option to specify the binary format for
input object files that follow this option on the command line. Even when ld is
configured to support alternative object formats, you don't usually need to specify
this, as ld should be configured to expect as a default input format the most usual
format on each machine. 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 objdump -i.)
You may want to use this option if you are linking files with an unusual binary
format. You can also use -b to switch formats explicitly (when linking object files
of different formats), by including -b input-format before each group of object
files in a particular format.
The default format is taken from the environment variable "GNUTARGET".
You can also define the input format from a script, using the command "TARGET";
-c MRI-commandfile
--mri-script=MRI-commandfile
For compatibility with linkers produced by MRI, ld accepts script files written in
an alternate, restricted command language, described in the MRI Compatible Script
Files section of GNU ld documentation. Introduce MRI script files with the option
-c; use the -T option to run linker scripts written in the general-purpose ld
scripting language. If MRI-cmdfile does not exist, ld looks for it in the
directories specified by any -L options.
-d
-dc
-dp These three options are equivalent; multiple forms are supported for compatibility
with other linkers. They assign space to common symbols even if a relocatable
output file is specified (with -r). The script command "FORCE_COMMON_ALLOCATION"
has the same effect.
--depaudit AUDITLIB
-P AUDITLIB
Adds AUDITLIB to the "DT_DEPAUDIT" entry of the dynamic section. AUDITLIB is not
checked for existence, nor will it use the DT_SONAME specified in the library. If
specified multiple times "DT_DEPAUDIT" will contain a colon separated list of audit
interfaces to use. This option is only meaningful on ELF platforms supporting the
rtld-audit interface. The -P option is provided for Solaris compatibility.
-e entry
--entry=entry
Use entry as the explicit symbol for beginning execution of your program, rather
than the default entry point. If there is no symbol named entry, the linker will
try to parse entry as a number, and use that as the entry address (the number will
be interpreted in base 10; you may use a leading 0x for base 16, or a leading 0 for
base 8).
--exclude-libs lib,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
"--exclude-libs ALL" excludes symbols in all archive libraries from automatic
export. This option is available only for the i386 PE targeted port of the linker
and for ELF targeted ports. For i386 PE, symbols explicitly listed in a .def file
are still exported, regardless of this option. For ELF targeted ports, symbols
affected by this option will be treated as hidden.
--exclude-modules-for-implib module,module,...
Specifies a list of object files or archive members, from which symbols should not
be automatically exported, but which should be copied wholesale into the import
library being generated during the link. The module names may be delimited by
commas or colons, and must match exactly the filenames used by ld to open the files;
for archive members, this is simply the member name, but for object files the name
listed must include and match precisely any path used to specify the input file on
the linker's command-line. This option is available only for the i386 PE targeted
port of the linker. Symbols explicitly listed in a .def file are still exported,
regardless of this option.
-E
--export-dynamic
--no-export-dynamic
When creating a dynamically linked executable, using the -E option or the
--export-dynamic option causes the linker to add all symbols to the dynamic symbol
table. The dynamic symbol table is the set of symbols which are visible from
dynamic objects at run time.
If you do not use either of these options (or use the --no-export-dynamic option to
restore the default behavior), the dynamic symbol table will normally contain only
those symbols which are referenced by some dynamic object mentioned in the link.
If you use "dlopen" to load a dynamic object which needs to refer back to the
symbols defined by the program, rather than some other dynamic object, then you will
probably need to use this option when linking the program itself.
You can also use the dynamic list to control what symbols should be added to the
dynamic symbol table if the output format supports it. See the description of
--dynamic-list.
Note that this option is specific to ELF targeted ports. PE targets support a
similar function to export all symbols from a DLL or EXE; see the description of
--export-all-symbols below.
-EB Link big-endian objects. This affects the default output format.
-EL Link little-endian objects. This affects the default output format.
-f name
--auxiliary=name
When creating an ELF shared object, set the internal DT_AUXILIARY field to the
specified name. This tells the dynamic linker that the symbol table of the shared
object should be used as an auxiliary filter on the symbol table of the shared
object name.
If you later link a program against this filter object, then, when you run the
program, the dynamic linker will see the DT_AUXILIARY field. If the dynamic linker
resolves any symbols from the filter object, it will first check whether there is a
definition in the shared object name. If there is one, it will be used instead of
the definition in the filter object. The shared object name need not exist. Thus
the shared object name may be used to provide an alternative implementation of
certain functions, perhaps for debugging or for machine specific performance.
This option may be specified more than once. The DT_AUXILIARY entries will be
created in the order in which they appear on the command line.
-F name
--filter=name
When creating an ELF shared object, set the internal DT_FILTER field to the
specified name. This tells the dynamic linker that the symbol table of the shared
object which is being created should be used as a filter on the symbol table of the
shared object name.
If you later link a program against this filter object, then, when you run the
program, the dynamic linker will see the DT_FILTER field. The dynamic linker will
resolve symbols according to the symbol table of the filter object as usual, but it
will actually link to the definitions found in the shared object name. Thus the
filter object can be used to select a subset of the symbols provided by the object
name.
Some older linkers used the -F option throughout a compilation toolchain for
specifying object-file format for both input and output object files. The GNU
linker uses other mechanisms for this purpose: the -b, --format, --oformat options,
the "TARGET" command in linker scripts, and the "GNUTARGET" environment variable.
The GNU linker will ignore the -F option when not creating an ELF shared object.
-fini=name
When creating an ELF executable or shared object, call NAME when the executable or
shared object is unloaded, by setting DT_FINI to the address of the function. By
default, the linker uses "_fini" as the function to call.
-g Ignored. Provided for compatibility with other tools.
-G value
--gpsize=value
Set the maximum size of objects to be optimized using the GP register to size. This
is only meaningful for object file formats such as MIPS ELF that support putting
large and small objects into different sections. This is ignored for other object
file formats.
-h name
-soname=name
When creating an ELF shared object, set the internal DT_SONAME field to the
specified name. When an executable is linked with a shared object which has a
DT_SONAME field, then when the executable is run the dynamic linker will attempt to
load the shared object specified by the DT_SONAME field rather than the using the
file name given to the linker.
-i Perform an incremental link (same as option -r).
-init=name
When creating an ELF executable or shared object, call NAME when the executable or
shared object is loaded, by setting DT_INIT to the address of the function. By
default, the linker uses "_init" as the function to call.
-l namespec
--library=namespec
Add the archive or object file specified by namespec to the list of files to link.
This option may be used any number of times. If namespec is of the form :filename,
ld will search the library path for a file called filename, otherwise it will search
the library path for a file called libnamespec.a.
On systems which support shared libraries, ld may also search for files other than
libnamespec.a. Specifically, on ELF and SunOS systems, ld will search a directory
for a library called libnamespec.so before searching for one called libnamespec.a.
(By convention, a ".so" extension indicates a shared library.) Note that this
behavior does not apply to :filename, which always specifies a file called filename.
The linker will search an archive only once, at the location where it is specified
on the command line. If the archive defines a symbol which was undefined in some
object which appeared before the archive on the command line, the linker will
include the appropriate file(s) from the archive. However, an undefined symbol in
an object appearing later on the command line will not cause the linker to search
the archive again.
See the -( option for a way to force the linker to search archives multiple times.
You may list the same archive multiple times on the command line.
This type of archive searching is standard for Unix linkers. However, if you are
using ld on AIX, note that it is different from the behaviour of the AIX linker.
-L searchdir
--library-path=searchdir
Add path searchdir to the list of paths that ld will search for archive libraries
and ld control scripts. You may use this option any number of times. The
directories are searched in the order in which they are specified on the command
line. Directories specified on the command line are searched before the default
directories. All -L options apply to all -l options, regardless of the order in
which the options appear. -L options do not affect how ld searches for a linker
script unless -T option is specified.
If searchdir begins with "=" or $SYSROOT, then this prefix will be replaced by the
sysroot prefix, controlled by the --sysroot option, or specified when the linker is
configured.
The default set of paths searched (without being specified with -L) depends on which
emulation mode ld is using, and in some cases also on how it was configured.
The paths can also be specified in a link script with the "SEARCH_DIR" command.
Directories specified this way are searched at the point in which the linker script
appears in the command line.
-m emulation
Emulate the emulation linker. You can list the available emulations with the
--verbose or -V options.
If the -m option is not used, the emulation is taken from the "LDEMULATION"
environment variable, if that is defined.
Otherwise, the default emulation depends upon how the linker was configured.
-M
--print-map
Print a link map to the standard output. A link map provides information about the
link, including the following:
· Where object files are mapped into memory.
· How common symbols are allocated.
· All archive members included in the link, with a mention of the symbol which
caused the archive member to be brought in.
· The values assigned to symbols.
Note - symbols whose values are computed by an expression which involves a
reference to a previous value of the same symbol may not have correct result
displayed in the link map. This is because the linker discards intermediate
results and only retains the final value of an expression. Under such
circumstances the linker will display the final value enclosed by square
brackets. Thus for example a linker script containing:
foo = 1
foo = foo * 4
foo = foo + 8
will produce the following output in the link map if the -M option is used:
0x00000001 foo = 0x1
[0x0000000c] foo = (foo * 0x4)
[0x0000000c] foo = (foo + 0x8)
See Expressions for more information about expressions in linker scripts.
-n
--nmagic
Turn off page alignment of sections, and disable linking against shared libraries.
If the output format supports Unix style magic numbers, mark the output as "NMAGIC".
-N
--omagic
Set the text and data sections to be readable and writable. Also, do 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 "OMAGIC". Note:
Although a writable text section is allowed for PE-COFF targets, it does not conform
to the format specification published by Microsoft.
--no-omagic
This option negates most of the effects of the -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 -Bdynamic for this.
-o output
--output=output
Use output as the name for the program produced by ld; if this option is not
specified, the name a.out is used by default. The script command "OUTPUT" can also
specify the output file name.
-O level
If level is a numeric values greater than zero ld optimizes the output. This might
take significantly longer and therefore probably should only be enabled for the
final binary. At the moment this option only affects ELF shared library generation.
Future releases of the linker may make more use of this option. Also currently
there is no difference in the linker's behaviour for different non-zero values of
this option. Again this may change with future releases.
-plugin name
Involve a plugin in the linking process. The name parameter is the absolute
filename of the plugin. Usually this parameter is automatically added by the
complier, when using link time optimization, but users can also add their own
plugins if they so wish.
Note that the location of the compiler originated plugins is different from the
place where the ar, nm and ranlib programs search for their plugins. In order for
those commands to make use of a compiler based plugin it must first be copied into
the ${libdir}/bfd-plugins directory. All gcc based linker plugins are backward
compatible, so it is sufficient to just copy in the newest one.
--push-state
The --push-state allows to preserve the current state of the flags which govern the
input file handling so that they can all be restored with one corresponding
--pop-state option.
The option which are covered are: -Bdynamic, -Bstatic, -dn, -dy, -call_shared,
-non_shared, -static, -N, -n, --whole-archive, --no-whole-archive, -r, -Ur,
--copy-dt-needed-entries, --no-copy-dt-needed-entries, --as-needed, --no-as-needed,
and -a.
One target for this option are specifications for pkg-config. When used with the
--libs option all possibly needed libraries are listed and then possibly linked with
all the time. It is better to return something as follows:
-Wl,--push-state,--as-needed -libone -libtwo -Wl,--pop-state
--pop-state
Undoes the effect of --push-state, restores the previous values of the flags
governing input file handling.
-q
--emit-relocs
Leave relocation sections and contents in fully linked executables. Post link
analysis and optimization tools may need this information in order to perform
correct modifications of executables. This results in larger executables.
This option is currently only supported on ELF platforms.
--force-dynamic
Force the output file to have dynamic sections. This option is specific to VxWorks
targets.
-r
--relocatable
Generate relocatable output---i.e., generate an output file that can in turn serve
as input to ld. This is often called 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 "OMAGIC". If this option is not specified, an
absolute file is produced. When linking C++ programs, this option will not resolve
references to constructors; to do that, use -Ur.
When an input file does not have the same format as the output file, partial linking
is only supported if that input file does not contain any relocations. Different
output formats can have further restrictions; for example some "a.out"-based formats
do not support partial linking with input files in other formats at all.
This option does the same thing as -i.
-R filename
--just-symbols=filename
Read symbol names and their addresses from filename, but do not 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. You may use this option
more than once.
For compatibility with other ELF linkers, if the -R option is followed by a
directory name, rather than a file name, it is treated as the -rpath option.
-s
--strip-all
Omit all symbol information from the output file.
-S
--strip-debug
Omit debugger symbol information (but not all symbols) from the output file.
--strip-discarded
--no-strip-discarded
Omit (or do not omit) global symbols defined in discarded sections. Enabled by
default.
-t
--trace
Print the names of the input files as ld processes them.
-T scriptfile
--script=scriptfile
Use scriptfile as the linker script. This script replaces ld's default linker
script (rather than adding to it), so commandfile must specify everything necessary
to describe the output file. If scriptfile does not exist in the current
directory, "ld" looks for it in the directories specified by any preceding -L
options. Multiple -T options accumulate.
-dT scriptfile
--default-script=scriptfile
Use scriptfile as the default linker script.
This option is similar to the --script option except that processing of the script
is delayed until after the rest of the command line has been processed. This allows
options placed after the --default-script option on the command line to affect the
behaviour of the linker script, which can be important when the linker command line
cannot be directly controlled by the user. (eg because the command line is being
constructed by another tool, such as gcc).
-u symbol
--undefined=symbol
Force 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. -u
may be repeated with different option arguments to enter additional undefined
symbols. This option is equivalent to the "EXTERN" linker script command.
If this option is being used to force additional modules to be pulled into the link,
and if it is an error for the symbol to remain undefined, then the option
--require-defined should be used instead.
--require-defined=symbol
Require that symbol is defined in the output file. This option is the same as
option --undefined except that if symbol is not defined in the output file then the
linker will issue an error and exit. The same effect can be achieved in a linker
script by using "EXTERN", "ASSERT" and "DEFINED" together. This option can be used
multiple times to require additional symbols.
-Ur For anything other than C++ programs, this option is equivalent to -r: it generates
relocatable output---i.e., an output file that can in turn serve as input to ld.
When linking C++ programs, -Ur does resolve references to constructors, unlike -r.
It does not work to use -Ur on files that were themselves linked with -Ur; once the
constructor table has been built, it cannot be added to. Use -Ur only for the last
partial link, and -r for the others.
--orphan-handling=MODE
Control how orphan sections are handled. An orphan section is one not specifically
mentioned in a linker script.
MODE can have any of the following values:
"place"
Orphan sections are placed into a suitable output section following the strategy
described in Orphan Sections. The option --unique also affects how sections are
placed.
"discard"
All orphan sections are discarded, by placing them in the /DISCARD/ section.
"warn"
The linker will place the orphan section as for "place" and also issue a
warning.
"error"
The linker will exit with an error if any orphan section is found.
The default if --orphan-handling is not given is "place".
--unique[=SECTION]
Creates a separate output section for every input section matching SECTION, or if
the optional wildcard SECTION argument is missing, for every orphan input section.
An orphan section is one not specifically mentioned in a linker script. You may use
this option multiple times on the command line; It prevents the normal merging of
input sections with the same name, overriding output section assignments in a linker
script.
-v
--version
-V Display the version number for ld. The -V option also lists the supported
emulations.
-x
--discard-all
Delete all local symbols.
-X
--discard-locals
Delete all temporary local symbols. (These symbols start with system-specific local
label prefixes, typically .L for ELF systems or L for traditional a.out systems.)
-y symbol
--trace-symbol=symbol
Print the name of each linked file in which 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.
-Y path
Add path to the default library search path. This option exists for Solaris
compatibility.
-z keyword
The recognized keywords are:
bndplt
Always generate BND prefix in PLT entries. Supported for Linux/x86_64.
call-nop=prefix-addr
call-nop=suffix-nop
call-nop=prefix-byte
call-nop=suffix-byte
Specify the 1-byte "NOP" padding when transforming indirect call to a locally
defined function, foo, via its GOT slot. call-nop=prefix-addr generates "0x67
call foo". call-nop=suffix-nop generates "call foo 0x90". call-nop=prefix-byte
generates "byte call foo". call-nop=suffix-byte generates "call foo byte".
Supported for i386 and x86_64.
combreloc
nocombreloc
Combine multiple dynamic relocation sections and sort to improve dynamic symbol
lookup caching. Do not do this if nocombreloc.
common
nocommon
Generate common symbols with STT_COMMON type during a relocatable link. Use
STT_OBJECT type if nocommon.
common-page-size=value
Set the page size most commonly used to value. Memory image layout will be
optimized to minimize memory pages if the system is using pages of this size.
defs
Report unresolved symbol references from regular object files. This is done
even if the linker is creating a non-symbolic shared library. This option is
the inverse of -z undefs.
dynamic-undefined-weak
nodynamic-undefined-weak
Make undefined weak symbols dynamic when building a dynamic object, if they are
referenced from a regular object file and not forced local by symbol visibility
or versioning. Do not make them dynamic if nodynamic-undefined-weak. If
neither option is given, a target may default to either option being in force,
or make some other selection of undefined weak symbols dynamic. Not all targets
support these options.
execstack
Marks the object as requiring executable stack.
global
This option is only meaningful when building a shared object. It makes the
symbols defined by this shared object available for symbol resolution of
subsequently loaded libraries.
globalaudit
This option is only meaningful when building a dynamic executable. This option
marks the executable as requiring global auditing by setting the
"DF_1_GLOBAUDIT" bit in the "DT_FLAGS_1" dynamic tag. Global auditing requires
that any auditing library defined via the --depaudit or -P command line options
be run for all dynamic objects loaded by the application.
ibtplt
Generate Intel Indirect Branch Tracking (IBT) enabled PLT entries. Supported
for Linux/i386 and Linux/x86_64.
ibt Generate GNU_PROPERTY_X86_FEATURE_1_IBT in .note.gnu.property section to
indicate compatibility with IBT. This also implies ibtplt. Supported for
Linux/i386 and Linux/x86_64.
initfirst
This option is only meaningful when building a shared object. It marks the
object so that its runtime initialization will occur before the runtime
initialization of any other objects brought into the process at the same time.
Similarly the runtime finalization of the object will occur after the runtime
finalization of any other objects.
interpose
Specify that the dynamic loader should modify its symbol search order so that
symbols in this shared library interpose all other shared libraries not so
marked.
lazy
When generating an executable or shared library, mark it to tell the dynamic
linker to defer function call resolution to the point when the function is
called (lazy binding), rather than at load time. Lazy binding is the default.
loadfltr
Specify that the object's filters be processed immediately at runtime.
max-page-size=value
Set the maximum memory page size supported to value.
muldefs
Allow multiple definitions.
nocopyreloc
Disable linker generated .dynbss variables used in place of variables defined in
shared libraries. May result in dynamic text relocations.
nodefaultlib
Specify that the dynamic loader search for dependencies of this object should
ignore any default library search paths.
nodelete
Specify that the object shouldn't be unloaded at runtime.
nodlopen
Specify that the object is not available to "dlopen".
nodump
Specify that the object can not be dumped by "dldump".
noexecstack
Marks the object as not requiring executable stack.
noextern-protected-data
Don't treat protected data symbols as external when building a shared library.
This option overrides the linker backend default. It can be used to work around
incorrect relocations against protected data symbols generated by compiler.
Updates on protected data symbols by another module aren't visible to the
resulting shared library. Supported for i386 and x86-64.
noreloc-overflow
Disable relocation overflow check. This can be used to disable relocation
overflow check if there will be no dynamic relocation overflow at run-time.
Supported for x86_64.
now When generating an executable or shared library, mark it to tell the dynamic
linker to resolve all symbols when the program is started, or when the shared
library is loaded by dlopen, instead of deferring function call resolution to
the point when the function is first called.
origin
Specify that the object requires $ORIGIN handling in paths.
relro
norelro
Create an ELF "PT_GNU_RELRO" segment header in the object. This specifies a
memory segment that should be made read-only after relocation, if supported.
Specifying common-page-size smaller than the system page size will render this
protection ineffective. Don't create an ELF "PT_GNU_RELRO" segment if norelro.
separate-code
noseparate-code
Create separate code "PT_LOAD" segment header in the object. This specifies a
memory segment that should contain only instructions and must be in wholly
disjoint pages from any other data. Don't create separate code "PT_LOAD"
segment if noseparate-code is used.
shstk
Generate GNU_PROPERTY_X86_FEATURE_1_SHSTK in .note.gnu.property section to
indicate compatibility with Intel Shadow Stack. Supported for Linux/i386 and
Linux/x86_64.
stack-size=value
Specify a stack size for an ELF "PT_GNU_STACK" segment. Specifying zero will
override any default non-zero sized "PT_GNU_STACK" segment creation.
text
notext
textoff
Report an error if DT_TEXTREL is set, i.e., if the binary has dynamic
relocations in read-only sections. Don't report an error if notext or textoff.
undefs
Do not report unresolved symbol references from regular object files, either
when creating an executable, or when creating a shared library. This option is
the inverse of -z defs.
Other keywords are ignored for Solaris compatibility.
-( archives -)
--start-group archives --end-group
The archives should be a list of archive files. They may be either explicit file
names, or -l options.
The specified archives are searched repeatedly until no new undefined references are
created. Normally, an archive is searched only once in the order that it is
specified on the command line. If a symbol in that archive is needed to resolve an
undefined symbol referred to by an object in an archive that appears later on the
command line, the linker would not be able to resolve that reference. By grouping
the archives, they all be searched repeatedly until all possible references are
resolved.
Using this option has a significant performance cost. It is best to use it only
when there are unavoidable circular references between two or more archives.
--accept-unknown-input-arch
--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 --accept-unknown-input-arch option has been added to restore
the old behaviour.
--as-needed
--no-as-needed
This option affects ELF DT_NEEDED tags for dynamic libraries mentioned on the
command line after the --as-needed option. Normally the linker will add a DT_NEEDED
tag for each dynamic library mentioned on the command line, regardless of whether
the library is actually needed or not. --as-needed causes a DT_NEEDED tag to only
be emitted for a library that at that point in the link satisfies a non-weak
undefined symbol reference from a regular object file or, if the library is not
found in the DT_NEEDED lists of other needed libraries, a non-weak undefined symbol
reference from another needed dynamic library. Object files or libraries appearing
on the command line after the library in question do not affect whether the library
is seen as needed. This is similar to the rules for extraction of object files from
archives. --no-as-needed restores the default behaviour.
--add-needed
--no-add-needed
These two options have been deprecated because of the similarity of their names to
the --as-needed and --no-as-needed options. They have been replaced by
--copy-dt-needed-entries and --no-copy-dt-needed-entries.
-assert keyword
This option is ignored for SunOS compatibility.
-Bdynamic
-dy
-call_shared
Link against dynamic libraries. This is only meaningful on platforms for which
shared libraries are supported. This option is normally the default on such
platforms. The different variants of this option are for compatibility with various
systems. You may use this option multiple times on the command line: it affects
library searching for -l options which follow it.
-Bgroup
Set the "DF_1_GROUP" flag in the "DT_FLAGS_1" entry in the dynamic section. This
causes the runtime linker to handle lookups in this object and its dependencies to
be performed only inside the group. --unresolved-symbols=report-all is implied.
This option is only meaningful on ELF platforms which support shared libraries.
-Bstatic
-dn
-non_shared
-static
Do not link against shared libraries. This is only meaningful on platforms for
which shared libraries are supported. The different variants of this option are for
compatibility with various systems. You may use this option multiple times on the
command line: it affects library searching for -l options which follow it. This
option also implies --unresolved-symbols=report-all. This option can be used with
-shared. Doing so means that a shared library is being created but that all of the
library's external references must be resolved by pulling in entries from static
libraries.
-Bsymbolic
When creating a shared library, bind references to global symbols to the definition
within the shared library, if any. Normally, it is possible for a program linked
against a shared library to override the definition within the shared library. This
option can also be used with the --export-dynamic option, when creating a position
independent executable, to bind references to global symbols to the definition
within the executable. This option is only meaningful on ELF platforms which
support shared libraries and position independent executables.
-Bsymbolic-functions
When creating a shared library, bind references to global function symbols to the
definition within the shared library, if any. This option can also be used with the
--export-dynamic option, when creating a position independent executable, to bind
references to global function symbols to the definition within the executable. This
option is only meaningful on ELF platforms which support shared libraries and
position independent executables.
--dynamic-list=dynamic-list-file
Specify the name of a dynamic list file to the linker. This is typically used when
creating shared libraries to specify a list of global symbols whose references
shouldn't be bound to the definition within the shared library, or creating
dynamically linked executables to specify a list of symbols which should be added to
the symbol table in the executable. This option is only meaningful on ELF platforms
which support shared libraries.
The format of the dynamic list is the same as the version node without scope and
node name. See VERSION for more information.
--dynamic-list-data
Include all global data symbols to the dynamic list.
--dynamic-list-cpp-new
Provide the builtin dynamic list for C++ operator new and delete. It is mainly
useful for building shared libstdc++.
--dynamic-list-cpp-typeinfo
Provide the builtin dynamic list for C++ runtime type identification.
--check-sections
--no-check-sections
Asks the linker not to check section addresses after they have been assigned to see
if there are any overlaps. Normally the linker will perform this check, and if it
finds any overlaps it will produce suitable error messages. The linker does know
about, and does make allowances for sections in overlays. The default behaviour can
be restored by using the command line switch --check-sections. Section overlap is
not usually checked for relocatable links. You can force checking in that case by
using the --check-sections option.
--copy-dt-needed-entries
--no-copy-dt-needed-entries
This option affects the treatment of dynamic libraries referred to by DT_NEEDED tags
inside ELF dynamic libraries mentioned on the command line. Normally the linker
won't add a DT_NEEDED tag to the output binary for each library mentioned in a
DT_NEEDED tag in an input dynamic library. With --copy-dt-needed-entries specified
on the command line however any dynamic libraries that follow it will have their
DT_NEEDED entries added. The default behaviour can be restored with
--no-copy-dt-needed-entries.
This option also has an effect on the resolution of symbols in dynamic libraries.
With --copy-dt-needed-entries dynamic libraries mentioned on the command line will
be recursively searched, following their DT_NEEDED tags to other libraries, in order
to resolve symbols required by the output binary. With the default setting however
the searching of dynamic libraries that follow it will stop with the dynamic library
itself. No DT_NEEDED links will be traversed to resolve symbols.
--cref
Output a cross reference table. If a linker map file is being generated, the cross
reference table is printed to the map file. Otherwise, it is printed on the
standard output.
The format of the table is intentionally simple, so that it may be easily processed
by a script if necessary. The symbols are printed out, sorted by name. For each
symbol, a list of file names is given. If the symbol is defined, the first file
listed is the location of the definition. If the symbol is defined as a common
value then any files where this happens appear next. Finally any files that
reference the symbol are listed.
--no-define-common
This option inhibits the assignment of addresses to common symbols. The script
command "INHIBIT_COMMON_ALLOCATION" has the same effect.
The --no-define-common option allows decoupling the decision to assign addresses to
Common symbols from the choice of the output file type; otherwise a non-Relocatable
output type forces assigning addresses to Common symbols. Using --no-define-common
allows Common symbols that are referenced from a shared library to be assigned
addresses only in the main program. This eliminates the unused duplicate space in
the shared library, and also prevents any possible confusion over resolving to the
wrong duplicate when there are many dynamic modules with specialized search paths
for runtime symbol resolution.
--force-group-allocation
This option causes the linker to place section group members like normal input
sections, and to delete the section groups. This is the default behaviour for a
final link but this option can be used to change the behaviour of a relocatable link
(-r). The script command "FORCE_GROUP_ALLOCATION" has the same effect.
--defsym=symbol=expression
Create a global symbol in the output file, containing the absolute address given by
expression. You may use this option as many times as necessary to define multiple
symbols in the command line. A limited form of arithmetic is supported for the
expression in this context: you may give a hexadecimal constant or the name of an
existing symbol, or use "+" and "-" to add or subtract hexadecimal constants or
symbols. If you need more elaborate expressions, consider using the linker command
language from a script. Note: there should be no white space between symbol, the
equals sign ("="), and expression.
--demangle[=style]
--no-demangle
These options control whether to demangle symbol names in error messages and other
output. When the linker is told to demangle, it tries to present symbol names in a
readable fashion: it strips leading underscores if they are used by the object file
format, and converts C++ mangled symbol names into user readable names. Different
compilers have different mangling styles. The optional demangling style argument
can be used to choose an appropriate demangling style for your compiler. The linker
will demangle by default unless the environment variable COLLECT_NO_DEMANGLE is set.
These options may be used to override the default.
-Ifile
--dynamic-linker=file
Set the name of the dynamic linker. This is only meaningful when generating
dynamically linked ELF executables. The default dynamic linker is normally correct;
don't use this unless you know what you are doing.
--no-dynamic-linker
When producing an executable file, omit the request for a dynamic linker to be used
at load-time. This is only meaningful for ELF executables that contain dynamic
relocations, and usually requires entry point code that is capable of processing
these relocations.
--embedded-relocs
This option is similar to the --emit-relocs option except that the relocs are stored
in a target specific section. This option is only supported by the BFIN, CR16 and
M68K targets.
--fatal-warnings
--no-fatal-warnings
Treat all warnings as errors. The default behaviour can be restored with the option
--no-fatal-warnings.