linker: Factor out more parts of linker_with_args and add some docs
This commit is contained in:
Vadim Petrochenkov
parent
fd6fa686df
commit
379c255eb9
@ -1255,6 +1255,87 @@ fn add_post_link_args(cmd: &mut dyn Linker, sess: &'a Session, flavor: LinkerFla
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}
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}
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/// Add object files containing code from the current crate.
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fn add_local_crate_regular_objects(cmd: &mut dyn Linker, codegen_results: &CodegenResults) {
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for obj in codegen_results.modules.iter().filter_map(|m| m.object.as_ref()) {
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cmd.add_object(obj);
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}
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}
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/// Add object files for allocator code linked once for the whole crate tree.
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fn add_local_crate_allocator_objects(cmd: &mut dyn Linker, codegen_results: &CodegenResults) {
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let obj = codegen_results.allocator_module.as_ref().and_then(|m| m.object.as_ref());
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if let Some(obj) = obj {
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cmd.add_object(obj);
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}
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}
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/// Add object files containing metadata for the current crate.
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fn add_local_crate_metadata_objects(
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cmd: &mut dyn Linker,
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crate_type: config::CrateType,
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codegen_results: &CodegenResults,
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) {
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// When linking a dynamic library, we put the metadata into a section of the
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// executable. This metadata is in a separate object file from the main
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// object file, so we link that in here.
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if crate_type == config::CrateType::Dylib || crate_type == config::CrateType::ProcMacro {
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let obj = codegen_results.metadata_module.as_ref().and_then(|m| m.object.as_ref());
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if let Some(obj) = obj {
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cmd.add_object(obj);
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}
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}
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}
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/// Link native libraries corresponding to the current crate and all libraries corresponding to
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/// all its dependency crates.
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/// FIXME: Consider combining this with the functions above adding object files for the local crate.
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fn link_local_crate_native_libs_and_dependent_crate_libs<'a, B: ArchiveBuilder<'a>>(
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cmd: &mut dyn Linker,
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sess: &'a Session,
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crate_type: config::CrateType,
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codegen_results: &CodegenResults,
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tmpdir: &Path,
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) {
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// Take careful note of the ordering of the arguments we pass to the linker
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// here. Linkers will assume that things on the left depend on things to the
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// right. Things on the right cannot depend on things on the left. This is
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// all formally implemented in terms of resolving symbols (libs on the right
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// resolve unknown symbols of libs on the left, but not vice versa).
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//
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// For this reason, we have organized the arguments we pass to the linker as
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// such:
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//
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// 1. The local object that LLVM just generated
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// 2. Local native libraries
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// 3. Upstream rust libraries
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// 4. Upstream native libraries
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//
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// The rationale behind this ordering is that those items lower down in the
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// list can't depend on items higher up in the list. For example nothing can
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// depend on what we just generated (e.g., that'd be a circular dependency).
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// Upstream rust libraries are not allowed to depend on our local native
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// libraries as that would violate the structure of the DAG, in that
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// scenario they are required to link to them as well in a shared fashion.
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//
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// Note that upstream rust libraries may contain native dependencies as
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// well, but they also can't depend on what we just started to add to the
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// link line. And finally upstream native libraries can't depend on anything
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// in this DAG so far because they're only dylibs and dylibs can only depend
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// on other dylibs (e.g., other native deps).
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//
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// If -Zlink-native-libraries=false is set, then the assumption is that an
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// external build system already has the native dependencies defined, and it
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// will provide them to the linker itself.
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if sess.opts.debugging_opts.link_native_libraries.unwrap_or(true) {
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add_local_native_libraries(cmd, sess, codegen_results);
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}
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add_upstream_rust_crates::<B>(cmd, sess, codegen_results, crate_type, tmpdir);
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if sess.opts.debugging_opts.link_native_libraries.unwrap_or(true) {
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add_upstream_native_libraries(cmd, sess, codegen_results, crate_type);
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}
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}
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/// Add sysroot and other globally set directories to the directory search list.
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fn add_library_search_dirs(cmd: &mut dyn Linker, sess: &'a Session) {
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// The default library location, we need this to find the runtime.
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@ -1271,6 +1352,95 @@ fn add_library_search_dirs(cmd: &mut dyn Linker, sess: &'a Session) {
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cmd.include_path(&fix_windows_verbatim_for_gcc(&lib_path));
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}
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/// Add options requesting executables to be position-independent or not position-independent.
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fn add_position_independent_executable_args(
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cmd: &mut dyn Linker,
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sess: &'a Session,
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flavor: LinkerFlavor,
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crate_type: config::CrateType,
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codegen_results: &CodegenResults,
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) {
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if crate_type != config::CrateType::Executable {
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return;
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}
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let mut position_independent_executable = false;
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if sess.target.target.options.position_independent_executables {
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let attr_link_args = &*codegen_results.crate_info.link_args;
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let mut user_defined_link_args = sess.opts.cg.link_args.iter().chain(attr_link_args);
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if is_pic(sess)
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&& !sess.crt_static(Some(crate_type))
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&& !user_defined_link_args.any(|x| x == "-static")
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{
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position_independent_executable = true;
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}
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}
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if position_independent_executable {
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cmd.position_independent_executable();
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} else {
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// recent versions of gcc can be configured to generate position
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// independent executables by default. We have to pass -no-pie to
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// explicitly turn that off. Not applicable to ld.
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if sess.target.target.options.linker_is_gnu && flavor != LinkerFlavor::Ld {
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cmd.no_position_independent_executable();
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}
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}
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}
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/// Add options making relocation sections in the produced ELF files read-only
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/// and suppressing lazy binding.
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fn add_relro_args(cmd: &mut dyn Linker, sess: &'a Session) {
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let relro_level = match sess.opts.debugging_opts.relro_level {
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Some(level) => level,
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None => sess.target.target.options.relro_level,
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};
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match relro_level {
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RelroLevel::Full => {
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cmd.full_relro();
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}
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RelroLevel::Partial => {
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cmd.partial_relro();
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}
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RelroLevel::Off => {
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cmd.no_relro();
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}
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RelroLevel::None => {}
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}
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}
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/// Add library search paths used at runtime by dynamic linkers.
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fn add_rpath_args(
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cmd: &mut dyn Linker,
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sess: &'a Session,
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codegen_results: &CodegenResults,
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out_filename: &Path,
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) {
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// FIXME (#2397): At some point we want to rpath our guesses as to
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// where extern libraries might live, based on the
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// addl_lib_search_paths
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if sess.opts.cg.rpath {
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let target_triple = sess.opts.target_triple.triple();
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let mut get_install_prefix_lib_path = || {
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let install_prefix = option_env!("CFG_PREFIX").expect("CFG_PREFIX");
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let tlib = filesearch::relative_target_lib_path(&sess.sysroot, target_triple);
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let mut path = PathBuf::from(install_prefix);
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path.push(&tlib);
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path
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};
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let mut rpath_config = RPathConfig {
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used_crates: &codegen_results.crate_info.used_crates_dynamic,
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out_filename: out_filename.to_path_buf(),
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has_rpath: sess.target.target.options.has_rpath,
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is_like_osx: sess.target.target.options.is_like_osx,
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linker_is_gnu: sess.target.target.options.linker_is_gnu,
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get_install_prefix_lib_path: &mut get_install_prefix_lib_path,
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};
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cmd.args(&rpath::get_rpath_flags(&mut rpath_config));
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}
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}
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/// Produce the linker command line containing linker path and arguments.
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/// `NO-OPT-OUT` marks the arguments that cannot be removed from the command line
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/// by the user without creating a custom target specification.
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@ -1332,9 +1502,7 @@ fn linker_with_args<'a, B: ArchiveBuilder<'a>>(
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add_library_search_dirs(cmd, sess);
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// OBJECT-FILES-YES
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for obj in codegen_results.modules.iter().filter_map(|m| m.object.as_ref()) {
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cmd.add_object(obj);
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}
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add_local_crate_regular_objects(cmd, codegen_results);
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// NO-OPT-OUT, OBJECT-FILES-NO, AUDIT-ORDER
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cmd.output_filename(out_filename);
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@ -1353,21 +1521,10 @@ fn linker_with_args<'a, B: ArchiveBuilder<'a>>(
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cmd.export_symbols(tmpdir, crate_type);
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// OBJECT-FILES-YES
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// When linking a dynamic library, we put the metadata into a section of the
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// executable. This metadata is in a separate object file from the main
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// object file, so we link that in here.
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if crate_type == config::CrateType::Dylib || crate_type == config::CrateType::ProcMacro {
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let obj = codegen_results.metadata_module.as_ref().and_then(|m| m.object.as_ref());
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if let Some(obj) = obj {
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cmd.add_object(obj);
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}
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}
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add_local_crate_metadata_objects(cmd, crate_type, codegen_results);
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// OBJECT-FILES-YES
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let obj = codegen_results.allocator_module.as_ref().and_then(|m| m.object.as_ref());
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if let Some(obj) = obj {
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cmd.add_object(obj);
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}
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add_local_crate_allocator_objects(cmd, codegen_results);
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// OBJECT-FILES-NO, AUDIT-ORDER
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// FIXME: Order dependent, applies to the following objects. Where should it be placed?
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@ -1379,53 +1536,10 @@ fn linker_with_args<'a, B: ArchiveBuilder<'a>>(
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}
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// NO-OPT-OUT, OBJECT-FILES-NO, AUDIT-ORDER
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if crate_type == config::CrateType::Executable {
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let mut position_independent_executable = false;
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if sess.target.target.options.position_independent_executables {
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if is_pic(sess)
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&& !sess.crt_static(Some(crate_type))
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&& !sess
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.opts
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.cg
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.link_args
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.iter()
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.chain(&*codegen_results.crate_info.link_args)
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.any(|x| x == "-static")
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{
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position_independent_executable = true;
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}
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}
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if position_independent_executable {
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cmd.position_independent_executable();
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} else {
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// recent versions of gcc can be configured to generate position
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// independent executables by default. We have to pass -no-pie to
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// explicitly turn that off. Not applicable to ld.
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if sess.target.target.options.linker_is_gnu && flavor != LinkerFlavor::Ld {
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cmd.no_position_independent_executable();
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}
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}
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}
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add_position_independent_executable_args(cmd, sess, flavor, crate_type, codegen_results);
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// OBJECT-FILES-NO, AUDIT-ORDER
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let relro_level = match sess.opts.debugging_opts.relro_level {
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Some(level) => level,
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None => sess.target.target.options.relro_level,
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};
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match relro_level {
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RelroLevel::Full => {
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cmd.full_relro();
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}
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RelroLevel::Partial => {
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cmd.partial_relro();
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}
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RelroLevel::Off => {
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cmd.no_relro();
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}
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RelroLevel::None => {}
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}
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add_relro_args(cmd, sess);
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// OBJECT-FILES-NO, AUDIT-ORDER
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// Pass optimization flags down to the linker.
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@ -1450,43 +1564,13 @@ fn linker_with_args<'a, B: ArchiveBuilder<'a>>(
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}
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// OBJECT-FILES-YES
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// Take careful note of the ordering of the arguments we pass to the linker
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// here. Linkers will assume that things on the left depend on things to the
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// right. Things on the right cannot depend on things on the left. This is
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// all formally implemented in terms of resolving symbols (libs on the right
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// resolve unknown symbols of libs on the left, but not vice versa).
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//
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// For this reason, we have organized the arguments we pass to the linker as
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// such:
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//
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// 1. The local object that LLVM just generated
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// 2. Local native libraries
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// 3. Upstream rust libraries
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// 4. Upstream native libraries
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//
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// The rationale behind this ordering is that those items lower down in the
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// list can't depend on items higher up in the list. For example nothing can
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// depend on what we just generated (e.g., that'd be a circular dependency).
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// Upstream rust libraries are not allowed to depend on our local native
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// libraries as that would violate the structure of the DAG, in that
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// scenario they are required to link to them as well in a shared fashion.
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//
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// Note that upstream rust libraries may contain native dependencies as
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// well, but they also can't depend on what we just started to add to the
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// link line. And finally upstream native libraries can't depend on anything
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// in this DAG so far because they're only dylibs and dylibs can only depend
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// on other dylibs (e.g., other native deps).
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//
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// If -Zlink-native-libraries=false is set, then the assumption is that an
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// external build system already has the native dependencies defined, and it
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// will provide them to the linker itself.
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if sess.opts.debugging_opts.link_native_libraries.unwrap_or(true) {
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add_local_native_libraries(cmd, sess, codegen_results);
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}
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add_upstream_rust_crates::<B>(cmd, sess, codegen_results, crate_type, tmpdir);
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if sess.opts.debugging_opts.link_native_libraries.unwrap_or(true) {
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add_upstream_native_libraries(cmd, sess, codegen_results, crate_type);
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}
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link_local_crate_native_libs_and_dependent_crate_libs::<B>(
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cmd,
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sess,
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crate_type,
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codegen_results,
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tmpdir,
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);
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// NO-OPT-OUT, OBJECT-FILES-NO, AUDIT-ORDER
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// Tell the linker what we're doing.
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@ -1508,29 +1592,7 @@ fn linker_with_args<'a, B: ArchiveBuilder<'a>>(
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}
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// OBJECT-FILES-NO, AUDIT-ORDER
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// FIXME (#2397): At some point we want to rpath our guesses as to
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// where extern libraries might live, based on the
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// addl_lib_search_paths
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if sess.opts.cg.rpath {
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let target_triple = sess.opts.target_triple.triple();
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let mut get_install_prefix_lib_path = || {
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let install_prefix = option_env!("CFG_PREFIX").expect("CFG_PREFIX");
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let tlib = filesearch::relative_target_lib_path(&sess.sysroot, target_triple);
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let mut path = PathBuf::from(install_prefix);
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path.push(&tlib);
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path
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};
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let mut rpath_config = RPathConfig {
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used_crates: &codegen_results.crate_info.used_crates_dynamic,
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out_filename: out_filename.to_path_buf(),
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has_rpath: sess.target.target.options.has_rpath,
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is_like_osx: sess.target.target.options.is_like_osx,
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linker_is_gnu: sess.target.target.options.linker_is_gnu,
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get_install_prefix_lib_path: &mut get_install_prefix_lib_path,
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};
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cmd.args(&rpath::get_rpath_flags(&mut rpath_config));
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}
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add_rpath_args(cmd, sess, codegen_results, out_filename);
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// OBJECT-FILES-MAYBE, CUSTOMIZATION-POINT
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add_user_defined_link_args(cmd, sess, codegen_results);
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