1 use rustc_arena::TypedArena;
2 use rustc_ast::CRATE_NODE_ID;
3 use rustc_data_structures::fx::FxHashSet;
4 use rustc_data_structures::fx::FxIndexMap;
5 use rustc_data_structures::memmap::Mmap;
6 use rustc_data_structures::temp_dir::MaybeTempDir;
7 use rustc_errors::{ErrorGuaranteed, Handler};
8 use rustc_fs_util::fix_windows_verbatim_for_gcc;
9 use rustc_hir::def_id::CrateNum;
10 use rustc_metadata::find_native_static_library;
11 use rustc_metadata::fs::{emit_metadata, METADATA_FILENAME};
12 use rustc_middle::middle::dependency_format::Linkage;
13 use rustc_middle::middle::exported_symbols::SymbolExportKind;
14 use rustc_session::config::{self, CFGuard, CrateType, DebugInfo, LdImpl, Strip};
15 use rustc_session::config::{OutputFilenames, OutputType, PrintRequest, SplitDwarfKind};
16 use rustc_session::cstore::DllImport;
17 use rustc_session::output::{check_file_is_writeable, invalid_output_for_target, out_filename};
18 use rustc_session::search_paths::PathKind;
19 use rustc_session::utils::NativeLibKind;
20 /// For all the linkers we support, and information they might
21 /// need out of the shared crate context before we get rid of it.
22 use rustc_session::{filesearch, Session};
23 use rustc_span::symbol::Symbol;
24 use rustc_span::DebuggerVisualizerFile;
25 use rustc_target::spec::crt_objects::{CrtObjects, LinkSelfContainedDefault};
26 use rustc_target::spec::{Cc, LinkOutputKind, LinkerFlavor, LinkerFlavorCli, Lld, PanicStrategy};
27 use rustc_target::spec::{RelocModel, RelroLevel, SanitizerSet, SplitDebuginfo, Target};
29 use super::archive::{ArchiveBuilder, ArchiveBuilderBuilder};
30 use super::command::Command;
31 use super::linker::{self, Linker};
32 use super::metadata::{create_rmeta_file, MetadataPosition};
33 use super::rpath::{self, RPathConfig};
35 errors, looks_like_rust_object_file, CodegenResults, CompiledModule, CrateInfo, NativeLib,
38 use cc::windows_registry;
40 use tempfile::Builder as TempFileBuilder;
42 use std::borrow::Borrow;
43 use std::cell::OnceCell;
44 use std::collections::BTreeSet;
45 use std::ffi::OsString;
46 use std::fs::{File, OpenOptions};
47 use std::io::{BufWriter, Write};
49 use std::path::{Path, PathBuf};
50 use std::process::{ExitStatus, Output, Stdio};
51 use std::{env, fmt, fs, io, mem, str};
53 pub fn ensure_removed(diag_handler: &Handler, path: &Path) {
54 if let Err(e) = fs::remove_file(path) {
55 if e.kind() != io::ErrorKind::NotFound {
56 diag_handler.err(&format!("failed to remove {}: {}", path.display(), e));
61 /// Performs the linkage portion of the compilation phase. This will generate all
62 /// of the requested outputs for this compilation session.
63 pub fn link_binary<'a>(
65 archive_builder_builder: &dyn ArchiveBuilderBuilder,
66 codegen_results: &CodegenResults,
67 outputs: &OutputFilenames,
68 ) -> Result<(), ErrorGuaranteed> {
69 let _timer = sess.timer("link_binary");
70 let output_metadata = sess.opts.output_types.contains_key(&OutputType::Metadata);
71 for &crate_type in sess.crate_types().iter() {
72 // Ignore executable crates if we have -Z no-codegen, as they will error.
73 if (sess.opts.unstable_opts.no_codegen || !sess.opts.output_types.should_codegen())
75 && crate_type == CrateType::Executable
80 if invalid_output_for_target(sess, crate_type) {
82 "invalid output type `{:?}` for target os `{}`",
84 sess.opts.target_triple
88 sess.time("link_binary_check_files_are_writeable", || {
89 for obj in codegen_results.modules.iter().filter_map(|m| m.object.as_ref()) {
90 check_file_is_writeable(obj, sess);
94 if outputs.outputs.should_link() {
95 let tmpdir = TempFileBuilder::new()
98 .unwrap_or_else(|error| sess.emit_fatal(errors::CreateTempDir { error }));
99 let path = MaybeTempDir::new(tmpdir, sess.opts.cg.save_temps);
100 let out_filename = out_filename(
104 codegen_results.crate_info.local_crate_name.as_str(),
108 let _timer = sess.timer("link_rlib");
109 info!("preparing rlib to {:?}", out_filename);
112 archive_builder_builder,
117 .build(&out_filename);
119 CrateType::Staticlib => {
122 archive_builder_builder,
131 archive_builder_builder,
139 if sess.opts.json_artifact_notifications {
140 sess.parse_sess.span_diagnostic.emit_artifact_notification(&out_filename, "link");
143 if sess.prof.enabled() {
144 if let Some(artifact_name) = out_filename.file_name() {
145 // Record size for self-profiling
146 let file_size = std::fs::metadata(&out_filename).map(|m| m.len()).unwrap_or(0);
148 sess.prof.artifact_size(
150 artifact_name.to_string_lossy(),
158 // Remove the temporary object file and metadata if we aren't saving temps.
159 sess.time("link_binary_remove_temps", || {
160 // If the user requests that temporaries are saved, don't delete any.
161 if sess.opts.cg.save_temps {
165 let maybe_remove_temps_from_module =
166 |preserve_objects: bool, preserve_dwarf_objects: bool, module: &CompiledModule| {
167 if !preserve_objects {
168 if let Some(ref obj) = module.object {
169 ensure_removed(sess.diagnostic(), obj);
173 if !preserve_dwarf_objects {
174 if let Some(ref dwo_obj) = module.dwarf_object {
175 ensure_removed(sess.diagnostic(), dwo_obj);
180 let remove_temps_from_module =
181 |module: &CompiledModule| maybe_remove_temps_from_module(false, false, module);
183 // Otherwise, always remove the metadata and allocator module temporaries.
184 if let Some(ref metadata_module) = codegen_results.metadata_module {
185 remove_temps_from_module(metadata_module);
188 if let Some(ref allocator_module) = codegen_results.allocator_module {
189 remove_temps_from_module(allocator_module);
192 // If no requested outputs require linking, then the object temporaries should
194 if !sess.opts.output_types.should_link() {
198 // Potentially keep objects for their debuginfo.
199 let (preserve_objects, preserve_dwarf_objects) = preserve_objects_for_their_debuginfo(sess);
200 debug!(?preserve_objects, ?preserve_dwarf_objects);
202 for module in &codegen_results.modules {
203 maybe_remove_temps_from_module(preserve_objects, preserve_dwarf_objects, module);
210 pub fn each_linked_rlib(
212 f: &mut dyn FnMut(CrateNum, &Path),
213 ) -> Result<(), errors::LinkRlibError> {
214 let crates = info.used_crates.iter();
216 for (ty, list) in info.dependency_formats.iter() {
218 CrateType::Executable
219 | CrateType::Staticlib
221 | CrateType::ProcMacro => {
228 let Some(fmts) = fmts else {
229 return Err(errors::LinkRlibError::MissingFormat);
231 for &cnum in crates {
232 match fmts.get(cnum.as_usize() - 1) {
233 Some(&Linkage::NotLinked | &Linkage::IncludedFromDylib) => continue,
235 None => return Err(errors::LinkRlibError::MissingFormat),
237 let crate_name = info.crate_name[&cnum];
238 let used_crate_source = &info.used_crate_source[&cnum];
239 if let Some((path, _)) = &used_crate_source.rlib {
242 if used_crate_source.rmeta.is_some() {
243 return Err(errors::LinkRlibError::OnlyRmetaFound { crate_name });
245 return Err(errors::LinkRlibError::NotFound { crate_name });
252 /// Create an 'rlib'.
254 /// An rlib in its current incarnation is essentially a renamed .a file. The rlib primarily contains
255 /// the object file of the crate, but it also contains all of the object files from native
256 /// libraries. This is done by unzipping native libraries and inserting all of the contents into
260 archive_builder_builder: &dyn ArchiveBuilderBuilder,
261 codegen_results: &CodegenResults,
263 tmpdir: &MaybeTempDir,
264 ) -> Result<Box<dyn ArchiveBuilder<'a> + 'a>, ErrorGuaranteed> {
265 let lib_search_paths = archive_search_paths(sess);
267 let mut ab = archive_builder_builder.new_archive_builder(sess);
269 let trailing_metadata = match flavor {
270 RlibFlavor::Normal => {
271 let (metadata, metadata_position) =
272 create_rmeta_file(sess, codegen_results.metadata.raw_data());
273 let metadata = emit_metadata(sess, &metadata, tmpdir);
274 match metadata_position {
275 MetadataPosition::First => {
276 // Most of the time metadata in rlib files is wrapped in a "dummy" object
277 // file for the target platform so the rlib can be processed entirely by
278 // normal linkers for the platform. Sometimes this is not possible however.
279 // If it is possible however, placing the metadata object first improves
280 // performance of getting metadata from rlibs.
281 ab.add_file(&metadata);
284 MetadataPosition::Last => Some(metadata),
288 RlibFlavor::StaticlibBase => None,
291 for m in &codegen_results.modules {
292 if let Some(obj) = m.object.as_ref() {
296 if let Some(dwarf_obj) = m.dwarf_object.as_ref() {
297 ab.add_file(dwarf_obj);
302 RlibFlavor::Normal => {}
303 RlibFlavor::StaticlibBase => {
304 let obj = codegen_results.allocator_module.as_ref().and_then(|m| m.object.as_ref());
305 if let Some(obj) = obj {
311 // Used if packed_bundled_libs flag enabled.
312 let mut packed_bundled_libs = Vec::new();
314 // Note that in this loop we are ignoring the value of `lib.cfg`. That is,
315 // we may not be configured to actually include a static library if we're
316 // adding it here. That's because later when we consume this rlib we'll
317 // decide whether we actually needed the static library or not.
319 // To do this "correctly" we'd need to keep track of which libraries added
320 // which object files to the archive. We don't do that here, however. The
321 // #[link(cfg(..))] feature is unstable, though, and only intended to get
322 // liblibc working. In that sense the check below just indicates that if
323 // there are any libraries we want to omit object files for at link time we
324 // just exclude all custom object files.
326 // Eventually if we want to stabilize or flesh out the #[link(cfg(..))]
327 // feature then we'll need to figure out how to record what objects were
328 // loaded from the libraries found here and then encode that into the
329 // metadata of the rlib we're generating somehow.
330 for lib in codegen_results.crate_info.used_libraries.iter() {
332 NativeLibKind::Static { bundle: None | Some(true), whole_archive: Some(true) }
333 if flavor == RlibFlavor::Normal && sess.opts.unstable_opts.packed_bundled_libs => {}
334 NativeLibKind::Static { bundle: None | Some(true), whole_archive: Some(true) }
335 if flavor == RlibFlavor::Normal =>
337 // Don't allow mixing +bundle with +whole_archive since an rlib may contain
338 // multiple native libs, some of which are +whole-archive and some of which are
339 // -whole-archive and it isn't clear how we can currently handle such a
340 // situation correctly.
341 // See https://github.com/rust-lang/rust/issues/88085#issuecomment-901050897
342 sess.emit_err(errors::IncompatibleLinkingModifiers);
344 NativeLibKind::Static { bundle: None | Some(true), .. } => {}
345 NativeLibKind::Static { bundle: Some(false), .. }
346 | NativeLibKind::Dylib { .. }
347 | NativeLibKind::Framework { .. }
348 | NativeLibKind::RawDylib
349 | NativeLibKind::LinkArg
350 | NativeLibKind::Unspecified => continue,
352 if let Some(name) = lib.name {
354 find_native_static_library(name.as_str(), lib.verbatim, &lib_search_paths, sess);
355 if sess.opts.unstable_opts.packed_bundled_libs && flavor == RlibFlavor::Normal {
356 packed_bundled_libs.push(find_native_static_library(
357 lib.filename.unwrap().as_str(),
364 ab.add_archive(&location, Box::new(|_| false)).unwrap_or_else(|error| {
365 sess.emit_fatal(errors::AddNativeLibrary {
366 library_path: &location.to_string_lossy(),
373 for (raw_dylib_name, raw_dylib_imports) in
374 collate_raw_dylibs(sess, &codegen_results.crate_info.used_libraries)?
376 let output_path = archive_builder_builder.create_dll_import_lib(
383 ab.add_archive(&output_path, Box::new(|_| false)).unwrap_or_else(|error| {
384 sess.emit_fatal(errors::AddNativeLibrary {
385 library_path: &output_path.display().to_string(),
391 if let Some(trailing_metadata) = trailing_metadata {
392 // Note that it is important that we add all of our non-object "magical
393 // files" *after* all of the object files in the archive. The reason for
394 // this is as follows:
396 // * When performing LTO, this archive will be modified to remove
397 // objects from above. The reason for this is described below.
399 // * When the system linker looks at an archive, it will attempt to
400 // determine the architecture of the archive in order to see whether its
403 // The algorithm for this detection is: iterate over the files in the
404 // archive. Skip magical SYMDEF names. Interpret the first file as an
405 // object file. Read architecture from the object file.
407 // * As one can probably see, if "metadata" and "foo.bc" were placed
408 // before all of the objects, then the architecture of this archive would
409 // not be correctly inferred once 'foo.o' is removed.
411 // * Most of the time metadata in rlib files is wrapped in a "dummy" object
412 // file for the target platform so the rlib can be processed entirely by
413 // normal linkers for the platform. Sometimes this is not possible however.
415 // Basically, all this means is that this code should not move above the
417 ab.add_file(&trailing_metadata);
420 // Add all bundled static native library dependencies.
421 // Archives added to the end of .rlib archive, see comment above for the reason.
422 for lib in packed_bundled_libs {
429 /// Extract all symbols defined in raw-dylib libraries, collated by library name.
431 /// If we have multiple extern blocks that specify symbols defined in the same raw-dylib library,
432 /// then the CodegenResults value contains one NativeLib instance for each block. However, the
433 /// linker appears to expect only a single import library for each library used, so we need to
434 /// collate the symbols together by library name before generating the import libraries.
435 fn collate_raw_dylibs(
437 used_libraries: &[NativeLib],
438 ) -> Result<Vec<(String, Vec<DllImport>)>, ErrorGuaranteed> {
439 // Use index maps to preserve original order of imports and libraries.
440 let mut dylib_table = FxIndexMap::<String, FxIndexMap<Symbol, &DllImport>>::default();
442 for lib in used_libraries {
443 if lib.kind == NativeLibKind::RawDylib {
444 let ext = if matches!(lib.verbatim, Some(true)) { "" } else { ".dll" };
445 let name = format!("{}{}", lib.name.expect("unnamed raw-dylib library"), ext);
446 let imports = dylib_table.entry(name.clone()).or_default();
447 for import in &lib.dll_imports {
448 if let Some(old_import) = imports.insert(import.name, import) {
449 // FIXME: when we add support for ordinals, figure out if we need to do anything
450 // if we have two DllImport values with the same name but different ordinals.
451 if import.calling_convention != old_import.calling_convention {
452 sess.emit_err(errors::MultipleExternalFuncDecl {
454 function: import.name,
462 sess.compile_status()?;
465 .map(|(name, imports)| {
466 (name, imports.into_iter().map(|(_, import)| import.clone()).collect())
471 /// Create a static archive.
473 /// This is essentially the same thing as an rlib, but it also involves adding all of the upstream
474 /// crates' objects into the archive. This will slurp in all of the native libraries of upstream
475 /// dependencies as well.
477 /// Additionally, there's no way for us to link dynamic libraries, so we warn about all dynamic
478 /// library dependencies that they're not linked in.
480 /// There's no need to include metadata in a static archive, so ensure to not link in the metadata
481 /// object file (and also don't prepare the archive with a metadata file).
482 fn link_staticlib<'a>(
484 archive_builder_builder: &dyn ArchiveBuilderBuilder,
485 codegen_results: &CodegenResults,
487 tempdir: &MaybeTempDir,
488 ) -> Result<(), ErrorGuaranteed> {
489 info!("preparing staticlib to {:?}", out_filename);
490 let mut ab = link_rlib(
492 archive_builder_builder,
494 RlibFlavor::StaticlibBase,
497 let mut all_native_libs = vec![];
499 let res = each_linked_rlib(&codegen_results.crate_info, &mut |cnum, path| {
500 let name = codegen_results.crate_info.crate_name[&cnum];
501 let native_libs = &codegen_results.crate_info.native_libraries[&cnum];
503 // Here when we include the rlib into our staticlib we need to make a
504 // decision whether to include the extra object files along the way.
505 // These extra object files come from statically included native
506 // libraries, but they may be cfg'd away with #[link(cfg(..))].
508 // This unstable feature, though, only needs liblibc to work. The only
509 // use case there is where musl is statically included in liblibc.rlib,
510 // so if we don't want the included version we just need to skip it. As
511 // a result the logic here is that if *any* linked library is cfg'd away
512 // we just skip all object files.
514 // Clearly this is not sufficient for a general purpose feature, and
515 // we'd want to read from the library's metadata to determine which
516 // object files come from where and selectively skip them.
517 let skip_object_files = native_libs.iter().any(|lib| {
518 matches!(lib.kind, NativeLibKind::Static { bundle: None | Some(true), .. })
519 && !relevant_lib(sess, lib)
522 let lto = are_upstream_rust_objects_already_included(sess)
523 && !ignored_for_lto(sess, &codegen_results.crate_info, cnum);
525 // Ignoring obj file starting with the crate name
526 // as simple comparison is not enough - there
527 // might be also an extra name suffix
528 let obj_start = name.as_str().to_owned();
532 Box::new(move |fname: &str| {
533 // Ignore metadata files, no matter the name.
534 if fname == METADATA_FILENAME {
538 // Don't include Rust objects if LTO is enabled
539 if lto && looks_like_rust_object_file(fname) {
543 // Otherwise if this is *not* a rust object and we're skipping
544 // objects then skip this file
545 if skip_object_files && (!fname.starts_with(&obj_start) || !fname.ends_with(".o")) {
549 // ok, don't skip this
555 all_native_libs.extend(codegen_results.crate_info.native_libraries[&cnum].iter().cloned());
557 if let Err(e) = res {
561 ab.build(out_filename);
563 if !all_native_libs.is_empty() {
564 if sess.opts.prints.contains(&PrintRequest::NativeStaticLibs) {
565 print_native_static_libs(sess, &all_native_libs);
572 /// Use `thorin` (rust implementation of a dwarf packaging utility) to link DWARF objects into a
574 fn link_dwarf_object<'a>(
576 cg_results: &CodegenResults,
577 executable_out_filename: &Path,
579 let dwp_out_filename = executable_out_filename.with_extension("dwp");
580 debug!(?dwp_out_filename, ?executable_out_filename);
583 struct ThorinSession<Relocations> {
584 arena_data: TypedArena<Vec<u8>>,
585 arena_mmap: TypedArena<Mmap>,
586 arena_relocations: TypedArena<Relocations>,
589 impl<Relocations> ThorinSession<Relocations> {
590 fn alloc_mmap<'arena>(&'arena self, data: Mmap) -> &'arena Mmap {
591 (*self.arena_mmap.alloc(data)).borrow()
595 impl<Relocations> thorin::Session<Relocations> for ThorinSession<Relocations> {
596 fn alloc_data<'arena>(&'arena self, data: Vec<u8>) -> &'arena [u8] {
597 (*self.arena_data.alloc(data)).borrow()
600 fn alloc_relocation<'arena>(&'arena self, data: Relocations) -> &'arena Relocations {
601 (*self.arena_relocations.alloc(data)).borrow()
604 fn read_input<'arena>(&'arena self, path: &Path) -> std::io::Result<&'arena [u8]> {
605 let file = File::open(&path)?;
606 let mmap = (unsafe { Mmap::map(file) })?;
607 Ok(self.alloc_mmap(mmap))
611 match sess.time("run_thorin", || -> Result<(), thorin::Error> {
612 let thorin_sess = ThorinSession::default();
613 let mut package = thorin::DwarfPackage::new(&thorin_sess);
615 // Input objs contain .o/.dwo files from the current crate.
616 match sess.opts.unstable_opts.split_dwarf_kind {
617 SplitDwarfKind::Single => {
618 for input_obj in cg_results.modules.iter().filter_map(|m| m.object.as_ref()) {
619 package.add_input_object(input_obj)?;
622 SplitDwarfKind::Split => {
623 for input_obj in cg_results.modules.iter().filter_map(|m| m.dwarf_object.as_ref()) {
624 package.add_input_object(input_obj)?;
629 // Input rlibs contain .o/.dwo files from dependencies.
630 let input_rlibs = cg_results
634 .filter_map(|csource| csource.rlib.as_ref())
635 .map(|(path, _)| path);
636 for input_rlib in input_rlibs {
638 package.add_input_object(input_rlib)?;
641 // Failing to read the referenced objects is expected for dependencies where the path in the
642 // executable will have been cleaned by Cargo, but the referenced objects will be contained
643 // within rlibs provided as inputs.
645 // If paths have been remapped, then .o/.dwo files from the current crate also won't be
646 // found, but are provided explicitly above.
648 // Adding an executable is primarily done to make `thorin` check that all the referenced
649 // dwarf objects are found in the end.
650 package.add_executable(
651 &executable_out_filename,
652 thorin::MissingReferencedObjectBehaviour::Skip,
655 let output = package.finish()?.write()?;
656 let mut output_stream = BufWriter::new(
662 .open(dwp_out_filename)?,
664 output_stream.write_all(&output)?;
665 output_stream.flush()?;
671 let thorin_error = errors::ThorinErrorWrapper(e);
672 sess.emit_err(errors::ThorinDwarfLinking { thorin_error });
673 sess.abort_if_errors();
678 /// Create a dynamic library or executable.
680 /// This will invoke the system linker/cc to create the resulting file. This links to all upstream
682 fn link_natively<'a>(
684 archive_builder_builder: &dyn ArchiveBuilderBuilder,
685 crate_type: CrateType,
687 codegen_results: &CodegenResults,
689 ) -> Result<(), ErrorGuaranteed> {
690 info!("preparing {:?} to {:?}", crate_type, out_filename);
691 let (linker_path, flavor) = linker_and_flavor(sess);
692 let mut cmd = linker_with_args(
696 archive_builder_builder,
703 linker::disable_localization(&mut cmd);
705 for &(ref k, ref v) in sess.target.link_env.as_ref() {
706 cmd.env(k.as_ref(), v.as_ref());
708 for k in sess.target.link_env_remove.as_ref() {
709 cmd.env_remove(k.as_ref());
712 if sess.opts.prints.contains(&PrintRequest::LinkArgs) {
713 println!("{:?}", &cmd);
716 // May have not found libraries in the right formats.
717 sess.abort_if_errors();
719 // Invoke the system linker
721 let retry_on_segfault = env::var("RUSTC_RETRY_LINKER_ON_SEGFAULT").is_ok();
722 let unknown_arg_regex =
723 Regex::new(r"(unknown|unrecognized) (command line )?(option|argument)").unwrap();
728 prog = sess.time("run_linker", || exec_linker(sess, &cmd, out_filename, tmpdir));
729 let Ok(ref output) = prog else {
732 if output.status.success() {
735 let mut out = output.stderr.clone();
736 out.extend(&output.stdout);
737 let out = String::from_utf8_lossy(&out);
739 // Check to see if the link failed with an error message that indicates it
740 // doesn't recognize the -no-pie option. If so, re-perform the link step
741 // without it. This is safe because if the linker doesn't support -no-pie
742 // then it should not default to linking executables as pie. Different
743 // versions of gcc seem to use different quotes in the error message so
744 // don't check for them.
745 if matches!(flavor, LinkerFlavor::Gnu(Cc::Yes, _))
746 && unknown_arg_regex.is_match(&out)
747 && out.contains("-no-pie")
748 && cmd.get_args().iter().any(|e| e.to_string_lossy() == "-no-pie")
750 info!("linker output: {:?}", out);
751 warn!("Linker does not support -no-pie command line option. Retrying without.");
752 for arg in cmd.take_args() {
753 if arg.to_string_lossy() != "-no-pie" {
761 // Detect '-static-pie' used with an older version of gcc or clang not supporting it.
762 // Fallback from '-static-pie' to '-static' in that case.
763 if matches!(flavor, LinkerFlavor::Gnu(Cc::Yes, _))
764 && unknown_arg_regex.is_match(&out)
765 && (out.contains("-static-pie") || out.contains("--no-dynamic-linker"))
766 && cmd.get_args().iter().any(|e| e.to_string_lossy() == "-static-pie")
768 info!("linker output: {:?}", out);
770 "Linker does not support -static-pie command line option. Retrying with -static instead."
772 // Mirror `add_(pre,post)_link_objects` to replace CRT objects.
773 let self_contained = self_contained(sess, crate_type);
774 let opts = &sess.target;
775 let pre_objects = if self_contained {
776 &opts.pre_link_objects_self_contained
778 &opts.pre_link_objects
780 let post_objects = if self_contained {
781 &opts.post_link_objects_self_contained
783 &opts.post_link_objects
785 let get_objects = |objects: &CrtObjects, kind| {
791 .map(|obj| get_object_file_path(sess, obj, self_contained).into_os_string())
794 let pre_objects_static_pie = get_objects(pre_objects, LinkOutputKind::StaticPicExe);
795 let post_objects_static_pie = get_objects(post_objects, LinkOutputKind::StaticPicExe);
796 let mut pre_objects_static = get_objects(pre_objects, LinkOutputKind::StaticNoPicExe);
797 let mut post_objects_static = get_objects(post_objects, LinkOutputKind::StaticNoPicExe);
798 // Assume that we know insertion positions for the replacement arguments from replaced
799 // arguments, which is true for all supported targets.
800 assert!(pre_objects_static.is_empty() || !pre_objects_static_pie.is_empty());
801 assert!(post_objects_static.is_empty() || !post_objects_static_pie.is_empty());
802 for arg in cmd.take_args() {
803 if arg.to_string_lossy() == "-static-pie" {
804 // Replace the output kind.
806 } else if pre_objects_static_pie.contains(&arg) {
807 // Replace the pre-link objects (replace the first and remove the rest).
808 cmd.args(mem::take(&mut pre_objects_static));
809 } else if post_objects_static_pie.contains(&arg) {
810 // Replace the post-link objects (replace the first and remove the rest).
811 cmd.args(mem::take(&mut post_objects_static));
820 // Here's a terribly awful hack that really shouldn't be present in any
821 // compiler. Here an environment variable is supported to automatically
822 // retry the linker invocation if the linker looks like it segfaulted.
824 // Gee that seems odd, normally segfaults are things we want to know
825 // about! Unfortunately though in rust-lang/rust#38878 we're
826 // experiencing the linker segfaulting on Travis quite a bit which is
827 // causing quite a bit of pain to land PRs when they spuriously fail
828 // due to a segfault.
830 // The issue #38878 has some more debugging information on it as well,
831 // but this unfortunately looks like it's just a race condition in
832 // macOS's linker with some thread pool working in the background. It
833 // seems that no one currently knows a fix for this so in the meantime
834 // we're left with this...
835 if !retry_on_segfault || i > 3 {
838 let msg_segv = "clang: error: unable to execute command: Segmentation fault: 11";
839 let msg_bus = "clang: error: unable to execute command: Bus error: 10";
840 if out.contains(msg_segv) || out.contains(msg_bus) {
843 "looks like the linker segfaulted when we tried to call it, \
844 automatically retrying again",
849 if is_illegal_instruction(&output.status) {
851 ?cmd, %out, status = %output.status,
852 "looks like the linker hit an illegal instruction when we \
853 tried to call it, automatically retrying again.",
859 fn is_illegal_instruction(status: &ExitStatus) -> bool {
860 use std::os::unix::prelude::*;
861 status.signal() == Some(libc::SIGILL)
865 fn is_illegal_instruction(_status: &ExitStatus) -> bool {
872 if !prog.status.success() {
873 let mut output = prog.stderr.clone();
874 output.extend_from_slice(&prog.stdout);
875 let escaped_output = escape_string(&output);
876 // FIXME: Add UI tests for this error.
877 let err = errors::LinkingFailed {
878 linker_path: &linker_path,
879 exit_status: prog.status,
881 escaped_output: &escaped_output,
883 sess.diagnostic().emit_err(err);
884 // If MSVC's `link.exe` was expected but the return code
885 // is not a Microsoft LNK error then suggest a way to fix or
886 // install the Visual Studio build tools.
887 if let Some(code) = prog.status.code() {
888 if sess.target.is_like_msvc
889 && flavor == LinkerFlavor::Msvc(Lld::No)
890 // Respect the command line override
891 && sess.opts.cg.linker.is_none()
892 // Match exactly "link.exe"
893 && linker_path.to_str() == Some("link.exe")
894 // All Microsoft `link.exe` linking error codes are
895 // four digit numbers in the range 1000 to 9999 inclusive
896 && (code < 1000 || code > 9999)
898 let is_vs_installed = windows_registry::find_vs_version().is_ok();
899 let has_linker = windows_registry::find_tool(
900 &sess.opts.target_triple.triple(),
905 sess.note_without_error("`link.exe` returned an unexpected error");
906 if is_vs_installed && has_linker {
907 // the linker is broken
908 sess.note_without_error(
909 "the Visual Studio build tools may need to be repaired \
910 using the Visual Studio installer",
912 sess.note_without_error(
913 "or a necessary component may be missing from the \
914 \"C++ build tools\" workload",
916 } else if is_vs_installed {
917 // the linker is not installed
918 sess.note_without_error(
919 "in the Visual Studio installer, ensure the \
920 \"C++ build tools\" workload is selected",
923 // visual studio is not installed
924 sess.note_without_error(
925 "you may need to install Visual Studio build tools with the \
926 \"C++ build tools\" workload",
932 sess.abort_if_errors();
934 info!("linker stderr:\n{}", escape_string(&prog.stderr));
935 info!("linker stdout:\n{}", escape_string(&prog.stdout));
938 let linker_not_found = e.kind() == io::ErrorKind::NotFound;
940 let mut linker_error = {
941 if linker_not_found {
942 sess.struct_err(&format!("linker `{}` not found", linker_path.display()))
944 sess.struct_err(&format!(
945 "could not exec the linker `{}`",
946 linker_path.display()
951 linker_error.note(&e.to_string());
953 if !linker_not_found {
954 linker_error.note(&format!("{:?}", &cmd));
959 if sess.target.is_like_msvc && linker_not_found {
960 sess.note_without_error(
961 "the msvc targets depend on the msvc linker \
962 but `link.exe` was not found",
964 sess.note_without_error(
965 "please ensure that Visual Studio 2017 or later, or Build Tools \
966 for Visual Studio were installed with the Visual C++ option.",
968 sess.note_without_error("VS Code is a different product, and is not sufficient.");
970 sess.abort_if_errors();
974 match sess.split_debuginfo() {
975 // If split debug information is disabled or located in individual files
976 // there's nothing to do here.
977 SplitDebuginfo::Off | SplitDebuginfo::Unpacked => {}
979 // If packed split-debuginfo is requested, but the final compilation
980 // doesn't actually have any debug information, then we skip this step.
981 SplitDebuginfo::Packed if sess.opts.debuginfo == DebugInfo::None => {}
983 // On macOS the external `dsymutil` tool is used to create the packed
984 // debug information. Note that this will read debug information from
985 // the objects on the filesystem which we'll clean up later.
986 SplitDebuginfo::Packed if sess.target.is_like_osx => {
987 let prog = Command::new("dsymutil").arg(out_filename).output();
990 if !prog.status.success() {
991 let mut output = prog.stderr.clone();
992 output.extend_from_slice(&prog.stdout);
993 sess.struct_warn(&format!(
994 "processing debug info with `dsymutil` failed: {}",
997 .note(&escape_string(&output))
1001 Err(e) => sess.fatal(&format!("unable to run `dsymutil`: {}", e)),
1005 // On MSVC packed debug information is produced by the linker itself so
1006 // there's no need to do anything else here.
1007 SplitDebuginfo::Packed if sess.target.is_like_windows => {}
1009 // ... and otherwise we're processing a `*.dwp` packed dwarf file.
1011 // We cannot rely on the .o paths in the executable because they may have been
1012 // remapped by --remap-path-prefix and therefore invalid, so we need to provide
1013 // the .o/.dwo paths explicitly.
1014 SplitDebuginfo::Packed => link_dwarf_object(sess, codegen_results, out_filename),
1017 let strip = strip_value(sess);
1019 if sess.target.is_like_osx {
1020 match (strip, crate_type) {
1021 (Strip::Debuginfo, _) => strip_symbols_in_osx(sess, &out_filename, Some("-S")),
1022 // Per the manpage, `-x` is the maximum safe strip level for dynamic libraries. (#93988)
1023 (Strip::Symbols, CrateType::Dylib | CrateType::Cdylib | CrateType::ProcMacro) => {
1024 strip_symbols_in_osx(sess, &out_filename, Some("-x"))
1026 (Strip::Symbols, _) => strip_symbols_in_osx(sess, &out_filename, None),
1027 (Strip::None, _) => {}
1034 // Temporarily support both -Z strip and -C strip
1035 fn strip_value(sess: &Session) -> Strip {
1036 match (sess.opts.unstable_opts.strip, sess.opts.cg.strip) {
1037 (s, Strip::None) => s,
1042 fn strip_symbols_in_osx<'a>(sess: &'a Session, out_filename: &Path, option: Option<&str>) {
1043 let mut cmd = Command::new("strip");
1044 if let Some(option) = option {
1047 let prog = cmd.arg(out_filename).output();
1050 if !prog.status.success() {
1051 let mut output = prog.stderr.clone();
1052 output.extend_from_slice(&prog.stdout);
1053 sess.struct_warn(&format!(
1054 "stripping debug info with `strip` failed: {}",
1057 .note(&escape_string(&output))
1061 Err(e) => sess.fatal(&format!("unable to run `strip`: {}", e)),
1065 fn escape_string(s: &[u8]) -> String {
1066 match str::from_utf8(s) {
1067 Ok(s) => s.to_owned(),
1068 Err(_) => format!("Non-UTF-8 output: {}", s.escape_ascii()),
1072 fn add_sanitizer_libraries(sess: &Session, crate_type: CrateType, linker: &mut dyn Linker) {
1073 // On macOS the runtimes are distributed as dylibs which should be linked to
1074 // both executables and dynamic shared objects. Everywhere else the runtimes
1075 // are currently distributed as static libraries which should be linked to
1076 // executables only.
1077 let needs_runtime = !sess.target.is_like_android
1078 && match crate_type {
1079 CrateType::Executable => true,
1080 CrateType::Dylib | CrateType::Cdylib | CrateType::ProcMacro => sess.target.is_like_osx,
1081 CrateType::Rlib | CrateType::Staticlib => false,
1088 let sanitizer = sess.opts.unstable_opts.sanitizer;
1089 if sanitizer.contains(SanitizerSet::ADDRESS) {
1090 link_sanitizer_runtime(sess, linker, "asan");
1092 if sanitizer.contains(SanitizerSet::LEAK) {
1093 link_sanitizer_runtime(sess, linker, "lsan");
1095 if sanitizer.contains(SanitizerSet::MEMORY) {
1096 link_sanitizer_runtime(sess, linker, "msan");
1098 if sanitizer.contains(SanitizerSet::THREAD) {
1099 link_sanitizer_runtime(sess, linker, "tsan");
1101 if sanitizer.contains(SanitizerSet::HWADDRESS) {
1102 link_sanitizer_runtime(sess, linker, "hwasan");
1106 fn link_sanitizer_runtime(sess: &Session, linker: &mut dyn Linker, name: &str) {
1107 fn find_sanitizer_runtime(sess: &Session, filename: &str) -> PathBuf {
1109 filesearch::make_target_lib_path(&sess.sysroot, sess.opts.target_triple.triple());
1110 let path = session_tlib.join(filename);
1112 return session_tlib;
1114 let default_sysroot = filesearch::get_or_default_sysroot();
1115 let default_tlib = filesearch::make_target_lib_path(
1117 sess.opts.target_triple.triple(),
1119 return default_tlib;
1123 let channel = option_env!("CFG_RELEASE_CHANNEL")
1124 .map(|channel| format!("-{}", channel))
1125 .unwrap_or_default();
1127 if sess.target.is_like_osx {
1128 // On Apple platforms, the sanitizer is always built as a dylib, and
1129 // LLVM will link to `@rpath/*.dylib`, so we need to specify an
1130 // rpath to the library as well (the rpath should be absolute, see
1131 // PR #41352 for details).
1132 let filename = format!("rustc{}_rt.{}", channel, name);
1133 let path = find_sanitizer_runtime(&sess, &filename);
1134 let rpath = path.to_str().expect("non-utf8 component in path");
1135 linker.args(&["-Wl,-rpath", "-Xlinker", rpath]);
1136 linker.link_dylib(&filename, false, true);
1138 let filename = format!("librustc{}_rt.{}.a", channel, name);
1139 let path = find_sanitizer_runtime(&sess, &filename).join(&filename);
1140 linker.link_whole_rlib(&path);
1144 /// Returns a boolean indicating whether the specified crate should be ignored
1147 /// Crates ignored during LTO are not lumped together in the "massive object
1148 /// file" that we create and are linked in their normal rlib states. See
1149 /// comments below for what crates do not participate in LTO.
1151 /// It's unusual for a crate to not participate in LTO. Typically only
1152 /// compiler-specific and unstable crates have a reason to not participate in
1154 pub fn ignored_for_lto(sess: &Session, info: &CrateInfo, cnum: CrateNum) -> bool {
1155 // If our target enables builtin function lowering in LLVM then the
1156 // crates providing these functions don't participate in LTO (e.g.
1157 // no_builtins or compiler builtins crates).
1158 !sess.target.no_builtins
1159 && (info.compiler_builtins == Some(cnum) || info.is_no_builtins.contains(&cnum))
1162 // This functions tries to determine the appropriate linker (and corresponding LinkerFlavor) to use
1163 pub fn linker_and_flavor(sess: &Session) -> (PathBuf, LinkerFlavor) {
1166 linker: Option<PathBuf>,
1167 flavor: Option<LinkerFlavor>,
1168 ) -> Option<(PathBuf, LinkerFlavor)> {
1169 match (linker, flavor) {
1170 (Some(linker), Some(flavor)) => Some((linker, flavor)),
1171 // only the linker flavor is known; use the default linker for the selected flavor
1172 (None, Some(flavor)) => Some((
1173 PathBuf::from(match flavor {
1174 LinkerFlavor::Gnu(Cc::Yes, _)
1175 | LinkerFlavor::Darwin(Cc::Yes, _)
1176 | LinkerFlavor::WasmLld(Cc::Yes)
1177 | LinkerFlavor::Unix(Cc::Yes) => {
1178 if cfg!(any(target_os = "solaris", target_os = "illumos")) {
1179 // On historical Solaris systems, "cc" may have
1180 // been Sun Studio, which is not flag-compatible
1181 // with "gcc". This history casts a long shadow,
1182 // and many modern illumos distributions today
1183 // ship GCC as "gcc" without also making it
1184 // available as "cc".
1190 LinkerFlavor::Gnu(_, Lld::Yes)
1191 | LinkerFlavor::Darwin(_, Lld::Yes)
1192 | LinkerFlavor::WasmLld(..)
1193 | LinkerFlavor::Msvc(Lld::Yes) => "lld",
1194 LinkerFlavor::Gnu(..) | LinkerFlavor::Darwin(..) | LinkerFlavor::Unix(..) => {
1197 LinkerFlavor::Msvc(..) => "link.exe",
1198 LinkerFlavor::EmCc => {
1205 LinkerFlavor::Bpf => "bpf-linker",
1206 LinkerFlavor::Ptx => "rust-ptx-linker",
1210 (Some(linker), None) => {
1211 let stem = linker.file_stem().and_then(|stem| stem.to_str()).unwrap_or_else(|| {
1212 sess.fatal("couldn't extract file stem from specified linker")
1215 let flavor = if stem == "emcc" {
1217 } else if stem == "gcc"
1218 || stem.ends_with("-gcc")
1220 || stem.ends_with("-clang")
1222 LinkerFlavor::from_cli(LinkerFlavorCli::Gcc, &sess.target)
1223 } else if stem == "wasm-ld" || stem.ends_with("-wasm-ld") {
1224 LinkerFlavor::WasmLld(Cc::No)
1225 } else if stem == "ld" || stem.ends_with("-ld") {
1226 LinkerFlavor::from_cli(LinkerFlavorCli::Ld, &sess.target)
1227 } else if stem == "ld.lld" {
1228 LinkerFlavor::Gnu(Cc::No, Lld::Yes)
1229 } else if stem == "link" {
1230 LinkerFlavor::Msvc(Lld::No)
1231 } else if stem == "lld-link" {
1232 LinkerFlavor::Msvc(Lld::Yes)
1233 } else if stem == "lld" || stem == "rust-lld" {
1234 let lld_flavor = sess.target.linker_flavor.lld_flavor();
1235 LinkerFlavor::from_cli(LinkerFlavorCli::Lld(lld_flavor), &sess.target)
1237 // fall back to the value in the target spec
1238 sess.target.linker_flavor
1241 Some((linker, flavor))
1243 (None, None) => None,
1247 // linker and linker flavor specified via command line have precedence over what the target
1248 // specification specifies
1250 sess.opts.cg.linker_flavor.map(|flavor| LinkerFlavor::from_cli(flavor, &sess.target));
1251 if let Some(ret) = infer_from(sess, sess.opts.cg.linker.clone(), linker_flavor) {
1255 if let Some(ret) = infer_from(
1257 sess.target.linker.as_deref().map(PathBuf::from),
1258 Some(sess.target.linker_flavor),
1263 bug!("Not enough information provided to determine how to invoke the linker");
1266 /// Returns a pair of boolean indicating whether we should preserve the object and
1267 /// dwarf object files on the filesystem for their debug information. This is often
1268 /// useful with split-dwarf like schemes.
1269 fn preserve_objects_for_their_debuginfo(sess: &Session) -> (bool, bool) {
1270 // If the objects don't have debuginfo there's nothing to preserve.
1271 if sess.opts.debuginfo == config::DebugInfo::None {
1272 return (false, false);
1275 // If we're only producing artifacts that are archives, no need to preserve
1276 // the objects as they're losslessly contained inside the archives.
1277 if sess.crate_types().iter().all(|&x| x.is_archive()) {
1278 return (false, false);
1281 match (sess.split_debuginfo(), sess.opts.unstable_opts.split_dwarf_kind) {
1282 // If there is no split debuginfo then do not preserve objects.
1283 (SplitDebuginfo::Off, _) => (false, false),
1284 // If there is packed split debuginfo, then the debuginfo in the objects
1285 // has been packaged and the objects can be deleted.
1286 (SplitDebuginfo::Packed, _) => (false, false),
1287 // If there is unpacked split debuginfo and the current target can not use
1288 // split dwarf, then keep objects.
1289 (SplitDebuginfo::Unpacked, _) if !sess.target_can_use_split_dwarf() => (true, false),
1290 // If there is unpacked split debuginfo and the target can use split dwarf, then
1291 // keep the object containing that debuginfo (whether that is an object file or
1292 // dwarf object file depends on the split dwarf kind).
1293 (SplitDebuginfo::Unpacked, SplitDwarfKind::Single) => (true, false),
1294 (SplitDebuginfo::Unpacked, SplitDwarfKind::Split) => (false, true),
1298 fn archive_search_paths(sess: &Session) -> Vec<PathBuf> {
1299 sess.target_filesearch(PathKind::Native).search_path_dirs()
1302 #[derive(PartialEq)]
1308 fn print_native_static_libs(sess: &Session, all_native_libs: &[NativeLib]) {
1309 let lib_args: Vec<_> = all_native_libs
1311 .filter(|l| relevant_lib(sess, l))
1313 let name = lib.name?;
1315 NativeLibKind::Static { bundle: Some(false), .. }
1316 | NativeLibKind::Dylib { .. }
1317 | NativeLibKind::Unspecified => {
1318 let verbatim = lib.verbatim.unwrap_or(false);
1319 if sess.target.is_like_msvc {
1320 Some(format!("{}{}", name, if verbatim { "" } else { ".lib" }))
1321 } else if sess.target.linker_flavor.is_gnu() {
1322 Some(format!("-l{}{}", if verbatim { ":" } else { "" }, name))
1324 Some(format!("-l{}", name))
1327 NativeLibKind::Framework { .. } => {
1328 // ld-only syntax, since there are no frameworks in MSVC
1329 Some(format!("-framework {}", name))
1331 // These are included, no need to print them
1332 NativeLibKind::Static { bundle: None | Some(true), .. }
1333 | NativeLibKind::LinkArg
1334 | NativeLibKind::RawDylib => None,
1338 if !lib_args.is_empty() {
1339 sess.note_without_error(
1340 "Link against the following native artifacts when linking \
1341 against this static library. The order and any duplication \
1342 can be significant on some platforms.",
1344 // Prefix for greppability
1345 sess.note_without_error(&format!("native-static-libs: {}", &lib_args.join(" ")));
1349 fn get_object_file_path(sess: &Session, name: &str, self_contained: bool) -> PathBuf {
1350 let fs = sess.target_filesearch(PathKind::Native);
1351 let file_path = fs.get_lib_path().join(name);
1352 if file_path.exists() {
1355 // Special directory with objects used only in self-contained linkage mode
1357 let file_path = fs.get_self_contained_lib_path().join(name);
1358 if file_path.exists() {
1362 for search_path in fs.search_paths() {
1363 let file_path = search_path.dir.join(name);
1364 if file_path.exists() {
1374 out_filename: &Path,
1376 ) -> io::Result<Output> {
1377 // When attempting to spawn the linker we run a risk of blowing out the
1378 // size limits for spawning a new process with respect to the arguments
1379 // we pass on the command line.
1381 // Here we attempt to handle errors from the OS saying "your list of
1382 // arguments is too big" by reinvoking the linker again with an `@`-file
1383 // that contains all the arguments. The theory is that this is then
1384 // accepted on all linkers and the linker will read all its options out of
1385 // there instead of looking at the command line.
1386 if !cmd.very_likely_to_exceed_some_spawn_limit() {
1387 match cmd.command().stdout(Stdio::piped()).stderr(Stdio::piped()).spawn() {
1389 let output = child.wait_with_output();
1390 flush_linked_file(&output, out_filename)?;
1393 Err(ref e) if command_line_too_big(e) => {
1394 info!("command line to linker was too big: {}", e);
1396 Err(e) => return Err(e),
1400 info!("falling back to passing arguments to linker via an @-file");
1401 let mut cmd2 = cmd.clone();
1402 let mut args = String::new();
1403 for arg in cmd2.take_args() {
1405 &Escape { arg: arg.to_str().unwrap(), is_like_msvc: sess.target.is_like_msvc }
1410 let file = tmpdir.join("linker-arguments");
1411 let bytes = if sess.target.is_like_msvc {
1412 let mut out = Vec::with_capacity((1 + args.len()) * 2);
1413 // start the stream with a UTF-16 BOM
1414 for c in std::iter::once(0xFEFF).chain(args.encode_utf16()) {
1415 // encode in little endian
1417 out.push((c >> 8) as u8);
1423 fs::write(&file, &bytes)?;
1424 cmd2.arg(format!("@{}", file.display()));
1425 info!("invoking linker {:?}", cmd2);
1426 let output = cmd2.output();
1427 flush_linked_file(&output, out_filename)?;
1430 #[cfg(not(windows))]
1431 fn flush_linked_file(_: &io::Result<Output>, _: &Path) -> io::Result<()> {
1436 fn flush_linked_file(
1437 command_output: &io::Result<Output>,
1438 out_filename: &Path,
1439 ) -> io::Result<()> {
1440 // On Windows, under high I/O load, output buffers are sometimes not flushed,
1441 // even long after process exit, causing nasty, non-reproducible output bugs.
1443 // File::sync_all() calls FlushFileBuffers() down the line, which solves the problem.
1445 // А full writeup of the original Chrome bug can be found at
1446 // randomascii.wordpress.com/2018/02/25/compiler-bug-linker-bug-windows-kernel-bug/amp
1448 if let &Ok(ref out) = command_output {
1449 if out.status.success() {
1450 if let Ok(of) = fs::OpenOptions::new().write(true).open(out_filename) {
1460 fn command_line_too_big(err: &io::Error) -> bool {
1461 err.raw_os_error() == Some(::libc::E2BIG)
1465 fn command_line_too_big(err: &io::Error) -> bool {
1466 const ERROR_FILENAME_EXCED_RANGE: i32 = 206;
1467 err.raw_os_error() == Some(ERROR_FILENAME_EXCED_RANGE)
1470 #[cfg(not(any(unix, windows)))]
1471 fn command_line_too_big(_: &io::Error) -> bool {
1480 impl<'a> fmt::Display for Escape<'a> {
1481 fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
1482 if self.is_like_msvc {
1483 // This is "documented" at
1484 // https://docs.microsoft.com/en-us/cpp/build/reference/at-specify-a-linker-response-file
1486 // Unfortunately there's not a great specification of the
1487 // syntax I could find online (at least) but some local
1488 // testing showed that this seemed sufficient-ish to catch
1489 // at least a few edge cases.
1491 for c in self.arg.chars() {
1493 '"' => write!(f, "\\{}", c)?,
1494 c => write!(f, "{}", c)?,
1499 // This is documented at https://linux.die.net/man/1/ld, namely:
1501 // > Options in file are separated by whitespace. A whitespace
1502 // > character may be included in an option by surrounding the
1503 // > entire option in either single or double quotes. Any
1504 // > character (including a backslash) may be included by
1505 // > prefixing the character to be included with a backslash.
1507 // We put an argument on each line, so all we need to do is
1508 // ensure the line is interpreted as one whole argument.
1509 for c in self.arg.chars() {
1511 '\\' | ' ' => write!(f, "\\{}", c)?,
1512 c => write!(f, "{}", c)?,
1521 fn link_output_kind(sess: &Session, crate_type: CrateType) -> LinkOutputKind {
1522 let kind = match (crate_type, sess.crt_static(Some(crate_type)), sess.relocation_model()) {
1523 (CrateType::Executable, _, _) if sess.is_wasi_reactor() => LinkOutputKind::WasiReactorExe,
1524 (CrateType::Executable, false, RelocModel::Pic | RelocModel::Pie) => {
1525 LinkOutputKind::DynamicPicExe
1527 (CrateType::Executable, false, _) => LinkOutputKind::DynamicNoPicExe,
1528 (CrateType::Executable, true, RelocModel::Pic | RelocModel::Pie) => {
1529 LinkOutputKind::StaticPicExe
1531 (CrateType::Executable, true, _) => LinkOutputKind::StaticNoPicExe,
1532 (_, true, _) => LinkOutputKind::StaticDylib,
1533 (_, false, _) => LinkOutputKind::DynamicDylib,
1536 // Adjust the output kind to target capabilities.
1537 let opts = &sess.target;
1538 let pic_exe_supported = opts.position_independent_executables;
1539 let static_pic_exe_supported = opts.static_position_independent_executables;
1540 let static_dylib_supported = opts.crt_static_allows_dylibs;
1542 LinkOutputKind::DynamicPicExe if !pic_exe_supported => LinkOutputKind::DynamicNoPicExe,
1543 LinkOutputKind::StaticPicExe if !static_pic_exe_supported => LinkOutputKind::StaticNoPicExe,
1544 LinkOutputKind::StaticDylib if !static_dylib_supported => LinkOutputKind::DynamicDylib,
1549 // Returns true if linker is located within sysroot
1550 fn detect_self_contained_mingw(sess: &Session) -> bool {
1551 let (linker, _) = linker_and_flavor(&sess);
1552 // Assume `-C linker=rust-lld` as self-contained mode
1553 if linker == Path::new("rust-lld") {
1556 let linker_with_extension = if cfg!(windows) && linker.extension().is_none() {
1557 linker.with_extension("exe")
1561 for dir in env::split_paths(&env::var_os("PATH").unwrap_or_default()) {
1562 let full_path = dir.join(&linker_with_extension);
1563 // If linker comes from sysroot assume self-contained mode
1564 if full_path.is_file() && !full_path.starts_with(&sess.sysroot) {
1571 /// Various toolchain components used during linking are used from rustc distribution
1572 /// instead of being found somewhere on the host system.
1573 /// We only provide such support for a very limited number of targets.
1574 fn self_contained(sess: &Session, crate_type: CrateType) -> bool {
1575 if let Some(self_contained) = sess.opts.cg.link_self_contained {
1576 return self_contained;
1579 match sess.target.link_self_contained {
1580 LinkSelfContainedDefault::False => false,
1581 LinkSelfContainedDefault::True => true,
1582 // FIXME: Find a better heuristic for "native musl toolchain is available",
1583 // based on host and linker path, for example.
1584 // (https://github.com/rust-lang/rust/pull/71769#issuecomment-626330237).
1585 LinkSelfContainedDefault::Musl => sess.crt_static(Some(crate_type)),
1586 LinkSelfContainedDefault::Mingw => {
1587 sess.host == sess.target
1588 && sess.target.vendor != "uwp"
1589 && detect_self_contained_mingw(&sess)
1594 /// Add pre-link object files defined by the target spec.
1595 fn add_pre_link_objects(
1596 cmd: &mut dyn Linker,
1598 flavor: LinkerFlavor,
1599 link_output_kind: LinkOutputKind,
1600 self_contained: bool,
1602 // FIXME: we are currently missing some infra here (per-linker-flavor CRT objects),
1603 // so Fuchsia has to be special-cased.
1604 let opts = &sess.target;
1605 let empty = Default::default();
1606 let objects = if self_contained {
1607 &opts.pre_link_objects_self_contained
1608 } else if !(sess.target.os == "fuchsia" && matches!(flavor, LinkerFlavor::Gnu(Cc::Yes, _))) {
1609 &opts.pre_link_objects
1613 for obj in objects.get(&link_output_kind).iter().copied().flatten() {
1614 cmd.add_object(&get_object_file_path(sess, obj, self_contained));
1618 /// Add post-link object files defined by the target spec.
1619 fn add_post_link_objects(
1620 cmd: &mut dyn Linker,
1622 link_output_kind: LinkOutputKind,
1623 self_contained: bool,
1625 let objects = if self_contained {
1626 &sess.target.post_link_objects_self_contained
1628 &sess.target.post_link_objects
1630 for obj in objects.get(&link_output_kind).iter().copied().flatten() {
1631 cmd.add_object(&get_object_file_path(sess, obj, self_contained));
1635 /// Add arbitrary "pre-link" args defined by the target spec or from command line.
1636 /// FIXME: Determine where exactly these args need to be inserted.
1637 fn add_pre_link_args(cmd: &mut dyn Linker, sess: &Session, flavor: LinkerFlavor) {
1638 if let Some(args) = sess.target.pre_link_args.get(&flavor) {
1639 cmd.args(args.iter().map(Deref::deref));
1641 cmd.args(&sess.opts.unstable_opts.pre_link_args);
1644 /// Add a link script embedded in the target, if applicable.
1645 fn add_link_script(cmd: &mut dyn Linker, sess: &Session, tmpdir: &Path, crate_type: CrateType) {
1646 match (crate_type, &sess.target.link_script) {
1647 (CrateType::Cdylib | CrateType::Executable, Some(script)) => {
1648 if !sess.target.linker_flavor.is_gnu() {
1649 sess.fatal("can only use link script when linking with GNU-like linker");
1652 let file_name = ["rustc", &sess.target.llvm_target, "linkfile.ld"].join("-");
1654 let path = tmpdir.join(file_name);
1655 if let Err(e) = fs::write(&path, script.as_ref()) {
1656 sess.fatal(&format!("failed to write link script to {}: {}", path.display(), e));
1659 cmd.arg("--script");
1666 /// Add arbitrary "user defined" args defined from command line.
1667 /// FIXME: Determine where exactly these args need to be inserted.
1668 fn add_user_defined_link_args(cmd: &mut dyn Linker, sess: &Session) {
1669 cmd.args(&sess.opts.cg.link_args);
1672 /// Add arbitrary "late link" args defined by the target spec.
1673 /// FIXME: Determine where exactly these args need to be inserted.
1674 fn add_late_link_args(
1675 cmd: &mut dyn Linker,
1677 flavor: LinkerFlavor,
1678 crate_type: CrateType,
1679 codegen_results: &CodegenResults,
1681 let any_dynamic_crate = crate_type == CrateType::Dylib
1682 || codegen_results.crate_info.dependency_formats.iter().any(|(ty, list)| {
1683 *ty == crate_type && list.iter().any(|&linkage| linkage == Linkage::Dynamic)
1685 if any_dynamic_crate {
1686 if let Some(args) = sess.target.late_link_args_dynamic.get(&flavor) {
1687 cmd.args(args.iter().map(Deref::deref));
1690 if let Some(args) = sess.target.late_link_args_static.get(&flavor) {
1691 cmd.args(args.iter().map(Deref::deref));
1694 if let Some(args) = sess.target.late_link_args.get(&flavor) {
1695 cmd.args(args.iter().map(Deref::deref));
1699 /// Add arbitrary "post-link" args defined by the target spec.
1700 /// FIXME: Determine where exactly these args need to be inserted.
1701 fn add_post_link_args(cmd: &mut dyn Linker, sess: &Session, flavor: LinkerFlavor) {
1702 if let Some(args) = sess.target.post_link_args.get(&flavor) {
1703 cmd.args(args.iter().map(Deref::deref));
1707 /// Add a synthetic object file that contains reference to all symbols that we want to expose to
1710 /// Background: we implement rlibs as static library (archives). Linkers treat archives
1711 /// differently from object files: all object files participate in linking, while archives will
1712 /// only participate in linking if they can satisfy at least one undefined reference (version
1713 /// scripts doesn't count). This causes `#[no_mangle]` or `#[used]` items to be ignored by the
1714 /// linker, and since they never participate in the linking, using `KEEP` in the linker scripts
1715 /// can't keep them either. This causes #47384.
1717 /// To keep them around, we could use `--whole-archive` and equivalents to force rlib to
1718 /// participate in linking like object files, but this proves to be expensive (#93791). Therefore
1719 /// we instead just introduce an undefined reference to them. This could be done by `-u` command
1720 /// line option to the linker or `EXTERN(...)` in linker scripts, however they does not only
1721 /// introduce an undefined reference, but also make them the GC roots, preventing `--gc-sections`
1722 /// from removing them, and this is especially problematic for embedded programming where every
1725 /// This method creates a synthetic object file, which contains undefined references to all symbols
1726 /// that are necessary for the linking. They are only present in symbol table but not actually
1727 /// used in any sections, so the linker will therefore pick relevant rlibs for linking, but
1728 /// unused `#[no_mangle]` or `#[used]` can still be discard by GC sections.
1730 /// There's a few internal crates in the standard library (aka libcore and
1731 /// libstd) which actually have a circular dependence upon one another. This
1732 /// currently arises through "weak lang items" where libcore requires things
1733 /// like `rust_begin_unwind` but libstd ends up defining it. To get this
1734 /// circular dependence to work correctly we declare some of these things
1735 /// in this synthetic object.
1736 fn add_linked_symbol_object(
1737 cmd: &mut dyn Linker,
1740 symbols: &[(String, SymbolExportKind)],
1742 if symbols.is_empty() {
1746 let Some(mut file) = super::metadata::create_object_file(sess) else {
1750 // NOTE(nbdd0121): MSVC will hang if the input object file contains no sections,
1751 // so add an empty section.
1752 if file.format() == object::BinaryFormat::Coff {
1753 file.add_section(Vec::new(), ".text".into(), object::SectionKind::Text);
1755 // We handle the name decoration of COFF targets in `symbol_export.rs`, so disable the
1756 // default mangler in `object` crate.
1757 file.set_mangling(object::write::Mangling::None);
1759 // Add feature flags to the object file. On MSVC this is optional but LLD will complain if
1761 let mut feature = 0;
1763 if file.architecture() == object::Architecture::I386 {
1764 // Indicate that all SEH handlers are registered in .sxdata section.
1765 // We don't have generate any code, so we don't need .sxdata section but LLD still
1766 // expects us to set this bit (see #96498).
1767 // Reference: https://docs.microsoft.com/en-us/windows/win32/debug/pe-format
1771 file.add_symbol(object::write::Symbol {
1772 name: "@feat.00".into(),
1775 kind: object::SymbolKind::Data,
1776 scope: object::SymbolScope::Compilation,
1778 section: object::write::SymbolSection::Absolute,
1779 flags: object::SymbolFlags::None,
1783 for (sym, kind) in symbols.iter() {
1784 file.add_symbol(object::write::Symbol {
1785 name: sym.clone().into(),
1789 SymbolExportKind::Text => object::SymbolKind::Text,
1790 SymbolExportKind::Data => object::SymbolKind::Data,
1791 SymbolExportKind::Tls => object::SymbolKind::Tls,
1793 scope: object::SymbolScope::Unknown,
1795 section: object::write::SymbolSection::Undefined,
1796 flags: object::SymbolFlags::None,
1800 let path = tmpdir.join("symbols.o");
1801 let result = std::fs::write(&path, file.write().unwrap());
1802 if let Err(e) = result {
1803 sess.fatal(&format!("failed to write {}: {}", path.display(), e));
1805 cmd.add_object(&path);
1808 /// Add object files containing code from the current crate.
1809 fn add_local_crate_regular_objects(cmd: &mut dyn Linker, codegen_results: &CodegenResults) {
1810 for obj in codegen_results.modules.iter().filter_map(|m| m.object.as_ref()) {
1811 cmd.add_object(obj);
1815 /// Add object files for allocator code linked once for the whole crate tree.
1816 fn add_local_crate_allocator_objects(cmd: &mut dyn Linker, codegen_results: &CodegenResults) {
1817 if let Some(obj) = codegen_results.allocator_module.as_ref().and_then(|m| m.object.as_ref()) {
1818 cmd.add_object(obj);
1822 /// Add object files containing metadata for the current crate.
1823 fn add_local_crate_metadata_objects(
1824 cmd: &mut dyn Linker,
1825 crate_type: CrateType,
1826 codegen_results: &CodegenResults,
1828 // When linking a dynamic library, we put the metadata into a section of the
1829 // executable. This metadata is in a separate object file from the main
1830 // object file, so we link that in here.
1831 if crate_type == CrateType::Dylib || crate_type == CrateType::ProcMacro {
1832 if let Some(obj) = codegen_results.metadata_module.as_ref().and_then(|m| m.object.as_ref())
1834 cmd.add_object(obj);
1839 /// Add sysroot and other globally set directories to the directory search list.
1840 fn add_library_search_dirs(cmd: &mut dyn Linker, sess: &Session, self_contained: bool) {
1841 // The default library location, we need this to find the runtime.
1842 // The location of crates will be determined as needed.
1843 let lib_path = sess.target_filesearch(PathKind::All).get_lib_path();
1844 cmd.include_path(&fix_windows_verbatim_for_gcc(&lib_path));
1846 // Special directory with libraries used only in self-contained linkage mode
1848 let lib_path = sess.target_filesearch(PathKind::All).get_self_contained_lib_path();
1849 cmd.include_path(&fix_windows_verbatim_for_gcc(&lib_path));
1853 /// Add options making relocation sections in the produced ELF files read-only
1854 /// and suppressing lazy binding.
1855 fn add_relro_args(cmd: &mut dyn Linker, sess: &Session) {
1856 match sess.opts.unstable_opts.relro_level.unwrap_or(sess.target.relro_level) {
1857 RelroLevel::Full => cmd.full_relro(),
1858 RelroLevel::Partial => cmd.partial_relro(),
1859 RelroLevel::Off => cmd.no_relro(),
1860 RelroLevel::None => {}
1864 /// Add library search paths used at runtime by dynamic linkers.
1866 cmd: &mut dyn Linker,
1868 codegen_results: &CodegenResults,
1869 out_filename: &Path,
1871 // FIXME (#2397): At some point we want to rpath our guesses as to
1872 // where extern libraries might live, based on the
1873 // add_lib_search_paths
1874 if sess.opts.cg.rpath {
1875 let libs = codegen_results
1879 .filter_map(|cnum| {
1880 codegen_results.crate_info.used_crate_source[cnum]
1883 .map(|(path, _)| &**path)
1885 .collect::<Vec<_>>();
1886 let mut rpath_config = RPathConfig {
1888 out_filename: out_filename.to_path_buf(),
1889 has_rpath: sess.target.has_rpath,
1890 is_like_osx: sess.target.is_like_osx,
1891 linker_is_gnu: sess.target.linker_flavor.is_gnu(),
1893 cmd.args(&rpath::get_rpath_flags(&mut rpath_config));
1897 /// Produce the linker command line containing linker path and arguments.
1899 /// When comments in the function say "order-(in)dependent" they mean order-dependence between
1900 /// options and libraries/object files. For example `--whole-archive` (order-dependent) applies
1901 /// to specific libraries passed after it, and `-o` (output file, order-independent) applies
1902 /// to the linking process as a whole.
1903 /// Order-independent options may still override each other in order-dependent fashion,
1904 /// e.g `--foo=yes --foo=no` may be equivalent to `--foo=no`.
1905 fn linker_with_args<'a>(
1907 flavor: LinkerFlavor,
1909 archive_builder_builder: &dyn ArchiveBuilderBuilder,
1910 crate_type: CrateType,
1912 out_filename: &Path,
1913 codegen_results: &CodegenResults,
1914 ) -> Result<Command, ErrorGuaranteed> {
1915 let self_contained = self_contained(sess, crate_type);
1916 let cmd = &mut *super::linker::get_linker(
1921 &codegen_results.crate_info.target_cpu,
1923 let link_output_kind = link_output_kind(sess, crate_type);
1925 // ------------ Early order-dependent options ------------
1927 // If we're building something like a dynamic library then some platforms
1928 // need to make sure that all symbols are exported correctly from the
1930 // Must be passed before any libraries to prevent the symbols to export from being thrown away,
1931 // at least on some platforms (e.g. windows-gnu).
1935 &codegen_results.crate_info.exported_symbols[&crate_type],
1938 // Can be used for adding custom CRT objects or overriding order-dependent options above.
1939 // FIXME: In practice built-in target specs use this for arbitrary order-independent options,
1940 // introduce a target spec option for order-independent linker options and migrate built-in
1942 add_pre_link_args(cmd, sess, flavor);
1944 // ------------ Object code and libraries, order-dependent ------------
1946 // Pre-link CRT objects.
1947 add_pre_link_objects(cmd, sess, flavor, link_output_kind, self_contained);
1949 add_linked_symbol_object(
1953 &codegen_results.crate_info.linked_symbols[&crate_type],
1956 // Sanitizer libraries.
1957 add_sanitizer_libraries(sess, crate_type, cmd);
1959 // Object code from the current crate.
1960 // Take careful note of the ordering of the arguments we pass to the linker
1961 // here. Linkers will assume that things on the left depend on things to the
1962 // right. Things on the right cannot depend on things on the left. This is
1963 // all formally implemented in terms of resolving symbols (libs on the right
1964 // resolve unknown symbols of libs on the left, but not vice versa).
1966 // For this reason, we have organized the arguments we pass to the linker as
1969 // 1. The local object that LLVM just generated
1970 // 2. Local native libraries
1971 // 3. Upstream rust libraries
1972 // 4. Upstream native libraries
1974 // The rationale behind this ordering is that those items lower down in the
1975 // list can't depend on items higher up in the list. For example nothing can
1976 // depend on what we just generated (e.g., that'd be a circular dependency).
1977 // Upstream rust libraries are not supposed to depend on our local native
1978 // libraries as that would violate the structure of the DAG, in that
1979 // scenario they are required to link to them as well in a shared fashion.
1981 // Note that upstream rust libraries may contain native dependencies as
1982 // well, but they also can't depend on what we just started to add to the
1983 // link line. And finally upstream native libraries can't depend on anything
1984 // in this DAG so far because they can only depend on other native libraries
1985 // and such dependencies are also required to be specified.
1986 add_local_crate_regular_objects(cmd, codegen_results);
1987 add_local_crate_metadata_objects(cmd, crate_type, codegen_results);
1988 add_local_crate_allocator_objects(cmd, codegen_results);
1990 // Avoid linking to dynamic libraries unless they satisfy some undefined symbols
1991 // at the point at which they are specified on the command line.
1992 // Must be passed before any (dynamic) libraries to have effect on them.
1993 // On Solaris-like systems, `-z ignore` acts as both `--as-needed` and `--gc-sections`
1994 // so it will ignore unreferenced ELF sections from relocatable objects.
1995 // For that reason, we put this flag after metadata objects as they would otherwise be removed.
1996 // FIXME: Support more fine-grained dead code removal on Solaris/illumos
1997 // and move this option back to the top.
1998 cmd.add_as_needed();
2000 // Local native libraries of all kinds.
2002 // If `-Zlink-native-libraries=false` is set, then the assumption is that an
2003 // external build system already has the native dependencies defined, and it
2004 // will provide them to the linker itself.
2005 if sess.opts.unstable_opts.link_native_libraries {
2006 add_local_native_libraries(cmd, sess, codegen_results);
2009 // Upstream rust libraries and their (possibly bundled) static native libraries.
2010 add_upstream_rust_crates(
2013 archive_builder_builder,
2019 // Dynamic native libraries from upstream crates.
2021 // FIXME: Merge this to `add_upstream_rust_crates` so that all native libraries are linked
2022 // together with their respective upstream crates, and in their originally specified order.
2023 // This may be slightly breaking due to our use of `--as-needed` and needs a crater run.
2024 if sess.opts.unstable_opts.link_native_libraries {
2025 add_upstream_native_libraries(cmd, sess, codegen_results);
2028 // Link with the import library generated for any raw-dylib functions.
2029 for (raw_dylib_name, raw_dylib_imports) in
2030 collate_raw_dylibs(sess, &codegen_results.crate_info.used_libraries)?
2032 cmd.add_object(&archive_builder_builder.create_dll_import_lib(
2040 // Library linking above uses some global state for things like `-Bstatic`/`-Bdynamic` to make
2041 // command line shorter, reset it to default here before adding more libraries.
2042 cmd.reset_per_library_state();
2044 // FIXME: Built-in target specs occasionally use this for linking system libraries,
2045 // eliminate all such uses by migrating them to `#[link]` attributes in `lib(std,c,unwind)`
2046 // and remove the option.
2047 add_late_link_args(cmd, sess, flavor, crate_type, codegen_results);
2049 // ------------ Arbitrary order-independent options ------------
2051 // Add order-independent options determined by rustc from its compiler options,
2052 // target properties and source code.
2053 add_order_independent_options(
2065 // Can be used for arbitrary order-independent options.
2066 // In practice may also be occasionally used for linking native libraries.
2067 // Passed after compiler-generated options to support manual overriding when necessary.
2068 add_user_defined_link_args(cmd, sess);
2070 // ------------ Object code and libraries, order-dependent ------------
2072 // Post-link CRT objects.
2073 add_post_link_objects(cmd, sess, link_output_kind, self_contained);
2075 // ------------ Late order-dependent options ------------
2077 // Doesn't really make sense.
2078 // FIXME: In practice built-in target specs use this for arbitrary order-independent options,
2079 // introduce a target spec option for order-independent linker options, migrate built-in specs
2080 // to it and remove the option.
2081 add_post_link_args(cmd, sess, flavor);
2086 fn add_order_independent_options(
2087 cmd: &mut dyn Linker,
2089 link_output_kind: LinkOutputKind,
2090 self_contained: bool,
2091 flavor: LinkerFlavor,
2092 crate_type: CrateType,
2093 codegen_results: &CodegenResults,
2094 out_filename: &Path,
2097 add_gcc_ld_path(cmd, sess, flavor);
2099 add_apple_sdk(cmd, sess, flavor);
2101 add_link_script(cmd, sess, tmpdir, crate_type);
2103 if sess.target.os == "fuchsia"
2104 && crate_type == CrateType::Executable
2105 && !matches!(flavor, LinkerFlavor::Gnu(Cc::Yes, _))
2107 let prefix = if sess.opts.unstable_opts.sanitizer.contains(SanitizerSet::ADDRESS) {
2112 cmd.arg(format!("--dynamic-linker={}ld.so.1", prefix));
2115 if sess.target.eh_frame_header {
2116 cmd.add_eh_frame_header();
2119 // Make the binary compatible with data execution prevention schemes.
2123 cmd.no_crt_objects();
2126 if sess.target.os == "emscripten" {
2128 cmd.arg(if sess.panic_strategy() == PanicStrategy::Abort {
2129 "DISABLE_EXCEPTION_CATCHING=1"
2131 "DISABLE_EXCEPTION_CATCHING=0"
2135 if flavor == LinkerFlavor::Ptx {
2136 // Provide the linker with fallback to internal `target-cpu`.
2137 cmd.arg("--fallback-arch");
2138 cmd.arg(&codegen_results.crate_info.target_cpu);
2139 } else if flavor == LinkerFlavor::Bpf {
2141 cmd.arg(&codegen_results.crate_info.target_cpu);
2142 cmd.arg("--cpu-features");
2143 cmd.arg(match &sess.opts.cg.target_feature {
2144 feat if !feat.is_empty() => feat.as_ref(),
2145 _ => sess.target.options.features.as_ref(),
2149 cmd.linker_plugin_lto();
2151 add_library_search_dirs(cmd, sess, self_contained);
2153 cmd.output_filename(out_filename);
2155 if crate_type == CrateType::Executable && sess.target.is_like_windows {
2156 if let Some(ref s) = codegen_results.crate_info.windows_subsystem {
2161 // Try to strip as much out of the generated object by removing unused
2162 // sections if possible. See more comments in linker.rs
2163 if !sess.link_dead_code() {
2164 // If PGO is enabled sometimes gc_sections will remove the profile data section
2165 // as it appears to be unused. This can then cause the PGO profile file to lose
2166 // some functions. If we are generating a profile we shouldn't strip those metadata
2167 // sections to ensure we have all the data for PGO.
2169 crate_type == CrateType::Dylib || sess.opts.cg.profile_generate.enabled();
2170 if crate_type != CrateType::Executable || !sess.opts.unstable_opts.export_executable_symbols
2172 cmd.gc_sections(keep_metadata);
2174 cmd.no_gc_sections();
2178 cmd.set_output_kind(link_output_kind, out_filename);
2180 add_relro_args(cmd, sess);
2182 // Pass optimization flags down to the linker.
2185 // Gather the set of NatVis files, if any, and write them out to a temp directory.
2186 let natvis_visualizers = collect_natvis_visualizers(
2189 &codegen_results.crate_info.local_crate_name,
2190 &codegen_results.crate_info.natvis_debugger_visualizers,
2193 // Pass debuginfo, NatVis debugger visualizers and strip flags down to the linker.
2194 cmd.debuginfo(strip_value(sess), &natvis_visualizers);
2196 // We want to prevent the compiler from accidentally leaking in any system libraries,
2197 // so by default we tell linkers not to link to any default libraries.
2198 if !sess.opts.cg.default_linker_libraries && sess.target.no_default_libraries {
2199 cmd.no_default_libraries();
2202 if sess.opts.cg.profile_generate.enabled() || sess.instrument_coverage() {
2206 if sess.opts.cg.control_flow_guard != CFGuard::Disabled {
2207 cmd.control_flow_guard();
2210 add_rpath_args(cmd, sess, codegen_results, out_filename);
2213 // Write the NatVis debugger visualizer files for each crate to the temp directory and gather the file paths.
2214 fn collect_natvis_visualizers(
2217 crate_name: &Symbol,
2218 natvis_debugger_visualizers: &BTreeSet<DebuggerVisualizerFile>,
2220 let mut visualizer_paths = Vec::with_capacity(natvis_debugger_visualizers.len());
2222 for (index, visualizer) in natvis_debugger_visualizers.iter().enumerate() {
2223 let visualizer_out_file = tmpdir.join(format!("{}-{}.natvis", crate_name.as_str(), index));
2225 match fs::write(&visualizer_out_file, &visualizer.src) {
2227 visualizer_paths.push(visualizer_out_file);
2232 "Unable to write debugger visualizer file `{}`: {} ",
2233 visualizer_out_file.display(),
2244 /// # Native library linking
2246 /// User-supplied library search paths (-L on the command line). These are the same paths used to
2247 /// find Rust crates, so some of them may have been added already by the previous crate linking
2248 /// code. This only allows them to be found at compile time so it is still entirely up to outside
2249 /// forces to make sure that library can be found at runtime.
2251 /// Also note that the native libraries linked here are only the ones located in the current crate.
2252 /// Upstream crates with native library dependencies may have their native library pulled in above.
2253 fn add_local_native_libraries(
2254 cmd: &mut dyn Linker,
2256 codegen_results: &CodegenResults,
2258 let filesearch = sess.target_filesearch(PathKind::All);
2259 for search_path in filesearch.search_paths() {
2260 match search_path.kind {
2261 PathKind::Framework => {
2262 cmd.framework_path(&search_path.dir);
2265 cmd.include_path(&fix_windows_verbatim_for_gcc(&search_path.dir));
2271 codegen_results.crate_info.used_libraries.iter().filter(|l| relevant_lib(sess, l));
2273 let search_path = OnceCell::new();
2274 let mut last = (None, NativeLibKind::Unspecified, None);
2275 for lib in relevant_libs {
2276 let Some(name) = lib.name else {
2279 let name = name.as_str();
2281 // Skip if this library is the same as the last.
2282 last = if (lib.name, lib.kind, lib.verbatim) == last {
2285 (lib.name, lib.kind, lib.verbatim)
2288 let verbatim = lib.verbatim.unwrap_or(false);
2290 NativeLibKind::Dylib { as_needed } => {
2291 cmd.link_dylib(name, verbatim, as_needed.unwrap_or(true))
2293 NativeLibKind::Unspecified => cmd.link_dylib(name, verbatim, true),
2294 NativeLibKind::Framework { as_needed } => {
2295 cmd.link_framework(name, as_needed.unwrap_or(true))
2297 NativeLibKind::Static { whole_archive, bundle, .. } => {
2298 if whole_archive == Some(true)
2299 // Backward compatibility case: this can be a rlib (so `+whole-archive` cannot
2300 // be added explicitly if necessary, see the error in `fn link_rlib`) compiled
2301 // as an executable due to `--test`. Use whole-archive implicitly, like before
2302 // the introduction of native lib modifiers.
2303 || (whole_archive == None && bundle != Some(false) && sess.opts.test)
2305 cmd.link_whole_staticlib(
2308 &search_path.get_or_init(|| archive_search_paths(sess)),
2311 cmd.link_staticlib(name, verbatim)
2314 NativeLibKind::RawDylib => {
2315 // Ignore RawDylib here, they are handled separately in linker_with_args().
2317 NativeLibKind::LinkArg => {
2324 /// # Linking Rust crates and their non-bundled static libraries
2326 /// Rust crates are not considered at all when creating an rlib output. All dependencies will be
2327 /// linked when producing the final output (instead of the intermediate rlib version).
2328 fn add_upstream_rust_crates<'a>(
2329 cmd: &mut dyn Linker,
2331 archive_builder_builder: &dyn ArchiveBuilderBuilder,
2332 codegen_results: &CodegenResults,
2333 crate_type: CrateType,
2336 // All of the heavy lifting has previously been accomplished by the
2337 // dependency_format module of the compiler. This is just crawling the
2338 // output of that module, adding crates as necessary.
2340 // Linking to a rlib involves just passing it to the linker (the linker
2341 // will slurp up the object files inside), and linking to a dynamic library
2342 // involves just passing the right -l flag.
2344 let (_, data) = codegen_results
2348 .find(|(ty, _)| *ty == crate_type)
2349 .expect("failed to find crate type in dependency format list");
2351 // Invoke get_used_crates to ensure that we get a topological sorting of
2353 let deps = &codegen_results.crate_info.used_crates;
2355 let mut compiler_builtins = None;
2356 let search_path = OnceCell::new();
2358 for &cnum in deps.iter() {
2359 // We may not pass all crates through to the linker. Some crates may
2360 // appear statically in an existing dylib, meaning we'll pick up all the
2361 // symbols from the dylib.
2362 let src = &codegen_results.crate_info.used_crate_source[&cnum];
2363 match data[cnum.as_usize() - 1] {
2364 _ if codegen_results.crate_info.profiler_runtime == Some(cnum) => {
2368 archive_builder_builder,
2372 &Default::default(),
2375 // compiler-builtins are always placed last to ensure that they're
2376 // linked correctly.
2377 _ if codegen_results.crate_info.compiler_builtins == Some(cnum) => {
2378 assert!(compiler_builtins.is_none());
2379 compiler_builtins = Some(cnum);
2381 Linkage::NotLinked | Linkage::IncludedFromDylib => {}
2382 Linkage::Static => {
2383 let bundled_libs = if sess.opts.unstable_opts.packed_bundled_libs {
2384 codegen_results.crate_info.native_libraries[&cnum]
2386 .filter_map(|lib| lib.filename)
2387 .collect::<FxHashSet<_>>()
2394 archive_builder_builder,
2401 // Link static native libs with "-bundle" modifier only if the crate they originate from
2402 // is being linked statically to the current crate. If it's linked dynamically
2403 // or is an rlib already included via some other dylib crate, the symbols from
2404 // native libs will have already been included in that dylib.
2406 // If `-Zlink-native-libraries=false` is set, then the assumption is that an
2407 // external build system already has the native dependencies defined, and it
2408 // will provide them to the linker itself.
2409 if sess.opts.unstable_opts.link_native_libraries {
2410 if sess.opts.unstable_opts.packed_bundled_libs {
2411 // If rlib contains native libs as archives, unpack them to tmpdir.
2412 let rlib = &src.rlib.as_ref().unwrap().0;
2413 archive_builder_builder
2414 .extract_bundled_libs(rlib, tmpdir, &bundled_libs)
2415 .unwrap_or_else(|e| sess.fatal(e));
2418 let mut last = (None, NativeLibKind::Unspecified, None);
2419 for lib in &codegen_results.crate_info.native_libraries[&cnum] {
2420 let Some(name) = lib.name else {
2423 let name = name.as_str();
2424 if !relevant_lib(sess, lib) {
2428 // Skip if this library is the same as the last.
2429 last = if (lib.name, lib.kind, lib.verbatim) == last {
2432 (lib.name, lib.kind, lib.verbatim)
2436 NativeLibKind::Static {
2437 bundle: Some(false),
2438 whole_archive: Some(true),
2440 cmd.link_whole_staticlib(
2442 lib.verbatim.unwrap_or(false),
2443 search_path.get_or_init(|| archive_search_paths(sess)),
2446 NativeLibKind::Static {
2447 bundle: Some(false),
2448 whole_archive: Some(false) | None,
2450 // HACK/FIXME: Fixup a circular dependency between libgcc and libc
2451 // with glibc. This logic should be moved to the libc crate.
2452 if sess.target.os == "linux"
2453 && sess.target.env == "gnu"
2456 cmd.link_staticlib("gcc", false);
2458 cmd.link_staticlib(name, lib.verbatim.unwrap_or(false));
2460 NativeLibKind::LinkArg => {
2463 NativeLibKind::Dylib { .. }
2464 | NativeLibKind::Framework { .. }
2465 | NativeLibKind::Unspecified
2466 | NativeLibKind::RawDylib => {}
2467 NativeLibKind::Static { bundle: Some(true) | None, whole_archive } => {
2468 if sess.opts.unstable_opts.packed_bundled_libs {
2469 // If rlib contains native libs as archives, they are unpacked to tmpdir.
2470 let path = tmpdir.join(lib.filename.unwrap().as_str());
2471 if whole_archive == Some(true) {
2472 cmd.link_whole_rlib(&path);
2474 cmd.link_rlib(&path);
2482 Linkage::Dynamic => add_dynamic_crate(cmd, sess, &src.dylib.as_ref().unwrap().0),
2486 // compiler-builtins are always placed last to ensure that they're
2487 // linked correctly.
2488 // We must always link the `compiler_builtins` crate statically. Even if it
2489 // was already "included" in a dylib (e.g., `libstd` when `-C prefer-dynamic`
2491 if let Some(cnum) = compiler_builtins {
2495 archive_builder_builder,
2499 &Default::default(),
2503 // Converts a library file-stem into a cc -l argument
2504 fn unlib<'a>(target: &Target, stem: &'a str) -> &'a str {
2505 if stem.starts_with("lib") && !target.is_like_windows { &stem[3..] } else { stem }
2508 // Adds the static "rlib" versions of all crates to the command line.
2509 // There's a bit of magic which happens here specifically related to LTO,
2510 // namely that we remove upstream object files.
2512 // When performing LTO, almost(*) all of the bytecode from the upstream
2513 // libraries has already been included in our object file output. As a
2514 // result we need to remove the object files in the upstream libraries so
2515 // the linker doesn't try to include them twice (or whine about duplicate
2516 // symbols). We must continue to include the rest of the rlib, however, as
2517 // it may contain static native libraries which must be linked in.
2519 // (*) Crates marked with `#![no_builtins]` don't participate in LTO and
2520 // their bytecode wasn't included. The object files in those libraries must
2521 // still be passed to the linker.
2523 // Note, however, that if we're not doing LTO we can just pass the rlib
2524 // blindly to the linker (fast) because it's fine if it's not actually
2525 // included as we're at the end of the dependency chain.
2526 fn add_static_crate<'a>(
2527 cmd: &mut dyn Linker,
2529 archive_builder_builder: &dyn ArchiveBuilderBuilder,
2530 codegen_results: &CodegenResults,
2533 bundled_lib_file_names: &FxHashSet<Symbol>,
2535 let src = &codegen_results.crate_info.used_crate_source[&cnum];
2536 let cratepath = &src.rlib.as_ref().unwrap().0;
2538 let mut link_upstream = |path: &Path| {
2539 cmd.link_rlib(&fix_windows_verbatim_for_gcc(path));
2542 // See the comment above in `link_staticlib` and `link_rlib` for why if
2543 // there's a static library that's not relevant we skip all object
2545 let native_libs = &codegen_results.crate_info.native_libraries[&cnum];
2546 let skip_native = native_libs.iter().any(|lib| {
2547 matches!(lib.kind, NativeLibKind::Static { bundle: None | Some(true), .. })
2548 && !relevant_lib(sess, lib)
2551 if (!are_upstream_rust_objects_already_included(sess)
2552 || ignored_for_lto(sess, &codegen_results.crate_info, cnum))
2555 link_upstream(cratepath);
2559 let dst = tmpdir.join(cratepath.file_name().unwrap());
2560 let name = cratepath.file_name().unwrap().to_str().unwrap();
2561 let name = &name[3..name.len() - 5]; // chop off lib/.rlib
2562 let bundled_lib_file_names = bundled_lib_file_names.clone();
2564 sess.prof.generic_activity_with_arg("link_altering_rlib", name).run(|| {
2565 let canonical_name = name.replace('-', "_");
2566 let upstream_rust_objects_already_included =
2567 are_upstream_rust_objects_already_included(sess);
2568 let is_builtins = sess.target.no_builtins
2569 || !codegen_results.crate_info.is_no_builtins.contains(&cnum);
2571 let mut archive = archive_builder_builder.new_archive_builder(sess);
2572 if let Err(e) = archive.add_archive(
2575 if f == METADATA_FILENAME {
2579 let canonical = f.replace('-', "_");
2581 let is_rust_object =
2582 canonical.starts_with(&canonical_name) && looks_like_rust_object_file(&f);
2584 // If we've been requested to skip all native object files
2585 // (those not generated by the rust compiler) then we can skip
2586 // this file. See above for why we may want to do this.
2587 let skip_because_cfg_say_so = skip_native && !is_rust_object;
2589 // If we're performing LTO and this is a rust-generated object
2590 // file, then we don't need the object file as it's part of the
2591 // LTO module. Note that `#![no_builtins]` is excluded from LTO,
2592 // though, so we let that object file slide.
2593 let skip_because_lto =
2594 upstream_rust_objects_already_included && is_rust_object && is_builtins;
2596 // We skip native libraries because:
2597 // 1. This native libraries won't be used from the generated rlib,
2598 // so we can throw them away to avoid the copying work.
2599 // 2. We can't allow it to be a single remaining entry in archive
2600 // as some linkers may complain on that.
2601 if bundled_lib_file_names.contains(&Symbol::intern(f)) {
2605 if skip_because_cfg_say_so || skip_because_lto {
2612 sess.fatal(&format!("failed to build archive from rlib: {}", e));
2614 if archive.build(&dst) {
2615 link_upstream(&dst);
2620 // Same thing as above, but for dynamic crates instead of static crates.
2621 fn add_dynamic_crate(cmd: &mut dyn Linker, sess: &Session, cratepath: &Path) {
2622 // Just need to tell the linker about where the library lives and
2624 let parent = cratepath.parent();
2625 if let Some(dir) = parent {
2626 cmd.include_path(&fix_windows_verbatim_for_gcc(dir));
2628 let filestem = cratepath.file_stem().unwrap().to_str().unwrap();
2629 cmd.link_rust_dylib(
2630 &unlib(&sess.target, filestem),
2631 parent.unwrap_or_else(|| Path::new("")),
2636 /// Link in all of our upstream crates' native dependencies. Remember that all of these upstream
2637 /// native dependencies are all non-static dependencies. We've got two cases then:
2639 /// 1. The upstream crate is an rlib. In this case we *must* link in the native dependency because
2640 /// the rlib is just an archive.
2642 /// 2. The upstream crate is a dylib. In order to use the dylib, we have to have the dependency
2643 /// present on the system somewhere. Thus, we don't gain a whole lot from not linking in the
2644 /// dynamic dependency to this crate as well.
2646 /// The use case for this is a little subtle. In theory the native dependencies of a crate are
2647 /// purely an implementation detail of the crate itself, but the problem arises with generic and
2648 /// inlined functions. If a generic function calls a native function, then the generic function
2649 /// must be instantiated in the target crate, meaning that the native symbol must also be resolved
2650 /// in the target crate.
2651 fn add_upstream_native_libraries(
2652 cmd: &mut dyn Linker,
2654 codegen_results: &CodegenResults,
2656 let mut last = (None, NativeLibKind::Unspecified, None);
2657 for &cnum in &codegen_results.crate_info.used_crates {
2658 for lib in codegen_results.crate_info.native_libraries[&cnum].iter() {
2659 let Some(name) = lib.name else {
2662 let name = name.as_str();
2663 if !relevant_lib(sess, &lib) {
2667 // Skip if this library is the same as the last.
2668 last = if (lib.name, lib.kind, lib.verbatim) == last {
2671 (lib.name, lib.kind, lib.verbatim)
2674 let verbatim = lib.verbatim.unwrap_or(false);
2676 NativeLibKind::Dylib { as_needed } => {
2677 cmd.link_dylib(name, verbatim, as_needed.unwrap_or(true))
2679 NativeLibKind::Unspecified => cmd.link_dylib(name, verbatim, true),
2680 NativeLibKind::Framework { as_needed } => {
2681 cmd.link_framework(name, as_needed.unwrap_or(true))
2683 // ignore static native libraries here as we've
2684 // already included them in add_local_native_libraries and
2685 // add_upstream_rust_crates
2686 NativeLibKind::Static { .. } => {}
2687 NativeLibKind::RawDylib | NativeLibKind::LinkArg => {}
2693 fn relevant_lib(sess: &Session, lib: &NativeLib) -> bool {
2695 Some(ref cfg) => rustc_attr::cfg_matches(cfg, &sess.parse_sess, CRATE_NODE_ID, None),
2700 fn are_upstream_rust_objects_already_included(sess: &Session) -> bool {
2702 config::Lto::Fat => true,
2703 config::Lto::Thin => {
2704 // If we defer LTO to the linker, we haven't run LTO ourselves, so
2705 // any upstream object files have not been copied yet.
2706 !sess.opts.cg.linker_plugin_lto.enabled()
2708 config::Lto::No | config::Lto::ThinLocal => false,
2712 fn add_apple_sdk(cmd: &mut dyn Linker, sess: &Session, flavor: LinkerFlavor) {
2713 let arch = &sess.target.arch;
2714 let os = &sess.target.os;
2715 let llvm_target = &sess.target.llvm_target;
2716 if sess.target.vendor != "apple"
2717 || !matches!(os.as_ref(), "ios" | "tvos" | "watchos" | "macos")
2718 || !matches!(flavor, LinkerFlavor::Darwin(..))
2723 if os == "macos" && !matches!(flavor, LinkerFlavor::Darwin(Cc::No, _)) {
2727 let sdk_name = match (arch.as_ref(), os.as_ref()) {
2728 ("aarch64", "tvos") => "appletvos",
2729 ("x86_64", "tvos") => "appletvsimulator",
2730 ("arm", "ios") => "iphoneos",
2731 ("aarch64", "ios") if llvm_target.contains("macabi") => "macosx",
2732 ("aarch64", "ios") if llvm_target.ends_with("-simulator") => "iphonesimulator",
2733 ("aarch64", "ios") => "iphoneos",
2734 ("x86", "ios") => "iphonesimulator",
2735 ("x86_64", "ios") if llvm_target.contains("macabi") => "macosx",
2736 ("x86_64", "ios") => "iphonesimulator",
2737 ("x86_64", "watchos") => "watchsimulator",
2738 ("arm64_32", "watchos") => "watchos",
2739 ("aarch64", "watchos") if llvm_target.ends_with("-simulator") => "watchsimulator",
2740 ("aarch64", "watchos") => "watchos",
2741 ("arm", "watchos") => "watchos",
2742 (_, "macos") => "macosx",
2744 sess.err(&format!("unsupported arch `{}` for os `{}`", arch, os));
2748 let sdk_root = match get_apple_sdk_root(sdk_name) {
2757 LinkerFlavor::Darwin(Cc::Yes, _) => {
2758 cmd.args(&["-isysroot", &sdk_root, "-Wl,-syslibroot", &sdk_root]);
2760 LinkerFlavor::Darwin(Cc::No, _) => {
2761 cmd.args(&["-syslibroot", &sdk_root]);
2763 _ => unreachable!(),
2767 fn get_apple_sdk_root(sdk_name: &str) -> Result<String, String> {
2768 // Following what clang does
2769 // (https://github.com/llvm/llvm-project/blob/
2770 // 296a80102a9b72c3eda80558fb78a3ed8849b341/clang/lib/Driver/ToolChains/Darwin.cpp#L1661-L1678)
2771 // to allow the SDK path to be set. (For clang, xcrun sets
2772 // SDKROOT; for rustc, the user or build system can set it, or we
2773 // can fall back to checking for xcrun on PATH.)
2774 if let Ok(sdkroot) = env::var("SDKROOT") {
2775 let p = Path::new(&sdkroot);
2777 // Ignore `SDKROOT` if it's clearly set for the wrong platform.
2779 if sdkroot.contains("TVSimulator.platform")
2780 || sdkroot.contains("MacOSX.platform") => {}
2782 if sdkroot.contains("TVOS.platform") || sdkroot.contains("MacOSX.platform") => {}
2784 if sdkroot.contains("iPhoneSimulator.platform")
2785 || sdkroot.contains("MacOSX.platform") => {}
2787 if sdkroot.contains("iPhoneOS.platform") || sdkroot.contains("MacOSX.platform") => {
2790 if sdkroot.contains("iPhoneOS.platform")
2791 || sdkroot.contains("iPhoneSimulator.platform") => {}
2793 if sdkroot.contains("WatchSimulator.platform")
2794 || sdkroot.contains("MacOSX.platform") => {}
2796 if sdkroot.contains("WatchOS.platform") || sdkroot.contains("MacOSX.platform") => {}
2797 // Ignore `SDKROOT` if it's not a valid path.
2798 _ if !p.is_absolute() || p == Path::new("/") || !p.exists() => {}
2799 _ => return Ok(sdkroot),
2803 Command::new("xcrun").arg("--show-sdk-path").arg("-sdk").arg(sdk_name).output().and_then(
2805 if output.status.success() {
2806 Ok(String::from_utf8(output.stdout).unwrap())
2808 let error = String::from_utf8(output.stderr);
2809 let error = format!("process exit with error: {}", error.unwrap());
2810 Err(io::Error::new(io::ErrorKind::Other, &error[..]))
2816 Ok(output) => Ok(output.trim().to_string()),
2817 Err(e) => Err(format!("failed to get {} SDK path: {}", sdk_name, e)),
2821 fn add_gcc_ld_path(cmd: &mut dyn Linker, sess: &Session, flavor: LinkerFlavor) {
2822 if let Some(ld_impl) = sess.opts.unstable_opts.gcc_ld {
2823 if let LinkerFlavor::Gnu(Cc::Yes, _)
2824 | LinkerFlavor::Darwin(Cc::Yes, _)
2825 | LinkerFlavor::WasmLld(Cc::Yes) = flavor
2829 // Implement the "self-contained" part of -Zgcc-ld
2830 // by adding rustc distribution directories to the tool search path.
2831 for path in sess.get_tools_search_paths(false) {
2833 let mut arg = OsString::from("-B");
2834 arg.push(path.join("gcc-ld"));
2838 // Implement the "linker flavor" part of -Zgcc-ld
2839 // by asking cc to use some kind of lld.
2840 cmd.arg("-fuse-ld=lld");
2841 if !flavor.is_gnu() {
2842 // Tell clang to use a non-default LLD flavor.
2843 // Gcc doesn't understand the target option, but we currently assume
2844 // that gcc is not used for Apple and Wasm targets (#97402).
2845 cmd.arg(format!("--target={}", sess.target.llvm_target));
2850 sess.fatal("option `-Z gcc-ld` is used even though linker flavor is not gcc");