| LD: File Commands |
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Several linker script commands deal with files.
INCLUDE filename
Include the linker script filename at this point. The file will
be searched for in the current directory, and in any directory specified
with the -L option. You can nest calls to INCLUDE up to
10 levels deep.
You can place INCLUDE directives at the top level, in MEMORY or
SECTIONS commands, or in output section descriptions.
INPUT(file, file, …)
INPUT(file file …)
The INPUT command directs the linker to include the named files
in the link, as though they were named on the command line.
For example, if you always want to include subr.o any time you do a link, but you can’t be bothered to put it on every link command line, then you can put ‘INPUT (subr.o)’ in your linker script.
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 ‘-T’ option.
In case a sysroot prefix is configured, and the filename starts
with the ‘/’ character, and the script being processed was
located inside the sysroot prefix, the filename will be looked
for in the 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.
The sysroot prefix can also be forced by specifying =
as the first character in the filename path, or prefixing the filename
path with $SYSROOT. See also the description of ‘-L’ in
Command Line Options.
If you use ‘INPUT (-lfile)’, ld will transform the
name to libfile.a, as with the command line argument
‘-l’.
When you use the INPUT command in an implicit linker script, the
files will be included in the link at the point at which the linker
script file is included. This can affect archive searching.
GROUP(file, file, …)
GROUP(file file …)
The GROUP command is like INPUT, except that the named
files should all be archives, and they are searched repeatedly until no
new undefined references are created. See the description of ‘-(’
in Command Line Options.
AS_NEEDED(file, file, …)
AS_NEEDED(file file …)
This construct can appear only inside of the INPUT or GROUP
commands, among other filenames. The files listed will be handled
as if they appear directly in the INPUT or GROUP commands,
with the exception of ELF shared libraries, that will be added only
when they are actually needed. This construct essentially enables
--as-needed option for all the files listed inside of it
and restores previous --as-needed resp. --no-as-needed
setting afterwards.
OUTPUT(filename)
The OUTPUT command names the output file. Using
OUTPUT(filename) in the linker script is exactly like using
‘-o filename
’ on the command line (see Command
Line Options). If both are used, the command line option takes
precedence.
You can use the OUTPUT command to define a default name for the
output file other than the usual default of a.out.
SEARCH_DIR(path)
The SEARCH_DIR command adds path to the list of paths where
ld looks for archive libraries. Using
SEARCH_DIR(path) is exactly like using ‘-L path
’
on the command line (see Command Line Options). If both
are used, then the linker will search both paths. Paths specified using
the command line option are searched first.
STARTUP(filename)
The STARTUP command is just like the INPUT command, except
that filename will become the first input file to be linked, as
though it were specified first on the command line. This may be useful
when using a system in which the entry point is always the start of the
first file.
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