gold patch committed: Skip incompatible objects

Ian Lance Taylor
Sat Mar 14 06:03:00 GMT 2009

When the GNU linker searches for an input file or an archive, if it
finds an incompatible file, it skips it and keeps searching.  An object
is incompatible if it is built for a target other than the one being
linked.  An archive is incompatible if it contains an incompatible
object.  A script is incompatible if it uses an OUTPUT_FORMAT command to
name a target other than the one being linked.  The GNU linker issues a
warning when it skips a file, unless --no-warn-search-mismatch is used.

I committed this patch to gold to implement the same functionality.  The
approach I used is to assume that the file is OK.  If we find out that
the file is not OK, we queue up a new task to find the next file with
the same name.  This means that this feature will not yield worse
performance for users who set up their builds correctly.

When the GNU linker is checking whether a linker script file is
compatible, it lexes the entire script and looks for an OUTPUT_FORMAT
command.  To avoid penalizing correct cases, gold uses a simpler
approach: the OUTPUT_FORMAT command must be found before anything which
changes the linker's global state.  Hopefully this difference will not
cause any trouble.


2009-03-13  Ian Lance Taylor  <>

	* (Read_symbols::incompatible_warning): New function.
	(Read_symbols::requeue): New function.
	(Read_symbols::do_read_symbols): If make_elf_object fails because
	the target type is not configured, and the file was searched for,
	issue a warning and retry with the next directory.
	(Add_symbols::run): If the file has an incompatible format, and
	it was searched for, requeue the Read_symbols task.  On error,
	release the object.
	* readsyms.h (class Read_symbols): Add dirindex_ field.  Add
	dirindex parameter to constructor.  Change all callers.  Declare
	incompatible_warning and requeue.
	(class Add_symbols): Add dirpath_, dirindex_, mapfile_,
	input_argument_ and input_group_ fields.  Add them to
	constructor.  Change all callers.
	(class Read_script): Add dirindex_ field.  Add it to constructor.
	Change all callers.
	* (Archive::setup): Remove input_objects parameter.
	Change all callers.
	(Archive::get_file_and_offset): Likewise.
	(Archive::read_all_symbols): Likewise.
	(Archive::read_symbols): Likewise.
	(Archive::get_elf_object_for_member): Remove input_objects
	parameter.  Add punconfigured parameter.  Change all callers.
	(Archive::add_symbols): Change return type to bool.  Check return
	value of include_member.
	(Archive::include_all_members): Likewise.
	(Archive::include_member): Change return type to bool.  Return
	false if first included object has incompatible target.  Set
	included_member_ field.
	(Add_archive_symbols::run): If add_symbols returns false, requeue
	Read_symbols task.
	* archive.h (class Archive): Add included_member_ field.
	Initialize it in constructor.  Add input_file and searched_for
	methods.  Update declarations.
	(class Add_archive_symbols): Add dirpath_, dirindex_, and
	input_argument_ fields.  Add them to constructor.  Change all
	* Include "target-select.h".
	(class Parser_closure): Add skip_on_incompatible_target_ and
	found_incompatible_target_ fields.  Add
	skip_on_incompatible_target parameter to constructor.  Change all
	callers.  Add methods skip_on_incompatible_target,
	clear_skip_on_incompatible_target, found_incompatible_target, and
	(read_input_script): Add dirindex parameter.  Change all callers.
	If parser finds an incompatible target, requeue Read_symbols
	(script_set_symbol): Clear skip_on_incompatible_target in
	(script_add_assertion, script_parse_option): Likewise.
	(script_start_sections, script_add_phdr): Likewise.
	(script_check_output_format): New function.
	* script.h (read_input_script): Update declaration.
	* script-c.h (script_check_output_format): Declare.
	* yyscript.y (file_cmd): Handle OUTPUT_FORMAT.
	(ignore_cmd): Remove OUTPUT_FORMAT.
	* (Input_file::Input_file): Add explicit this.
	(Input_file::will_search_for): New function.
	(Input_file::open): Add pindex parameter.  Change all callers.
	* fileread.h (class Input_file): Add input_file_argument method.
	Declare will_search_for.  Update declarations.
	* (make_elf_object): Add punconfigured parameter.
	Change all callers.
	* object.h (class Object): Make input_file public.  Add
	searched_for method.
	(make_elf_object): Update declaration.
	* (Dirsearch::find): Add pindex parameter.  Use it to
	restart search.
	* dirsearch.h (class Dirsearch): Update declaration.
	* options.h (class General_options): Add --warn-search-mismatch.
	* (Parameters::is_compatible_target): New function.
	* parameters.h (class Parameters): Declare is_compatible_target.
	* (Workqueue::add_blocker): New function.
	* workqueue.h (class Workqueue): Declare add_blocker.

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