3.4.2 Commands Dealing with Files

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. 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 a sysroot prefix is not used then the linker will try to open the file in the directory containing the linker script. If it is not found the linker will then search the current directory. If it is still not found the linker will search through the archive library search path.

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.