1 use rustc_arena::TypedArena;
2 use rustc_ast::CRATE_NODE_ID;
3 use rustc_data_structures::fx::{FxHashSet, FxIndexMap};
4 use rustc_data_structures::memmap::Mmap;
5 use rustc_data_structures::temp_dir::MaybeTempDir;
6 use rustc_errors::{ErrorGuaranteed, Handler};
7 use rustc_fs_util::fix_windows_verbatim_for_gcc;
8 use rustc_hir::def_id::CrateNum;
9 use rustc_metadata::fs::{emit_metadata, METADATA_FILENAME};
10 use rustc_middle::middle::dependency_format::Linkage;
11 use rustc_middle::middle::exported_symbols::SymbolExportKind;
12 use rustc_session::config::{self, CFGuard, CrateType, DebugInfo, LdImpl, Strip};
13 use rustc_session::config::{OutputFilenames, OutputType, PrintRequest, SplitDwarfKind};
14 use rustc_session::cstore::DllImport;
15 use rustc_session::output::{check_file_is_writeable, invalid_output_for_target, out_filename};
16 use rustc_session::search_paths::PathKind;
17 use rustc_session::utils::NativeLibKind;
18 /// For all the linkers we support, and information they might
19 /// need out of the shared crate context before we get rid of it.
20 use rustc_session::{filesearch, Session};
21 use rustc_span::symbol::Symbol;
22 use rustc_span::DebuggerVisualizerFile;
23 use rustc_target::spec::crt_objects::{CrtObjects, LinkSelfContainedDefault};
24 use rustc_target::spec::{LinkOutputKind, LinkerFlavor, LldFlavor, SplitDebuginfo};
25 use rustc_target::spec::{PanicStrategy, RelocModel, RelroLevel, SanitizerSet, Target};
27 use super::archive::{find_library, ArchiveBuilder, ArchiveBuilderBuilder};
28 use super::command::Command;
29 use super::linker::{self, Linker};
30 use super::metadata::{create_rmeta_file, MetadataPosition};
31 use super::rpath::{self, RPathConfig};
32 use crate::{looks_like_rust_object_file, CodegenResults, CompiledModule, CrateInfo, NativeLib};
34 use cc::windows_registry;
36 use tempfile::Builder as TempFileBuilder;
38 use std::borrow::Borrow;
39 use std::cell::OnceCell;
40 use std::collections::BTreeSet;
41 use std::ffi::OsString;
42 use std::fs::{File, OpenOptions};
43 use std::io::{BufWriter, Write};
45 use std::path::{Path, PathBuf};
46 use std::process::{ExitStatus, Output, Stdio};
47 use std::{env, fmt, fs, io, mem, str};
49 pub fn ensure_removed(diag_handler: &Handler, path: &Path) {
50 if let Err(e) = fs::remove_file(path) {
51 if e.kind() != io::ErrorKind::NotFound {
52 diag_handler.err(&format!("failed to remove {}: {}", path.display(), e));
57 /// Performs the linkage portion of the compilation phase. This will generate all
58 /// of the requested outputs for this compilation session.
59 pub fn link_binary<'a>(
61 archive_builder_builder: &dyn ArchiveBuilderBuilder,
62 codegen_results: &CodegenResults,
63 outputs: &OutputFilenames,
64 ) -> Result<(), ErrorGuaranteed> {
65 let _timer = sess.timer("link_binary");
66 let output_metadata = sess.opts.output_types.contains_key(&OutputType::Metadata);
67 for &crate_type in sess.crate_types().iter() {
68 // Ignore executable crates if we have -Z no-codegen, as they will error.
69 if (sess.opts.unstable_opts.no_codegen || !sess.opts.output_types.should_codegen())
71 && crate_type == CrateType::Executable
76 if invalid_output_for_target(sess, crate_type) {
78 "invalid output type `{:?}` for target os `{}`",
80 sess.opts.target_triple
84 sess.time("link_binary_check_files_are_writeable", || {
85 for obj in codegen_results.modules.iter().filter_map(|m| m.object.as_ref()) {
86 check_file_is_writeable(obj, sess);
90 if outputs.outputs.should_link() {
91 let tmpdir = TempFileBuilder::new()
94 .unwrap_or_else(|err| sess.fatal(&format!("couldn't create a temp dir: {}", err)));
95 let path = MaybeTempDir::new(tmpdir, sess.opts.cg.save_temps);
96 let out_filename = out_filename(
100 codegen_results.crate_info.local_crate_name.as_str(),
104 let _timer = sess.timer("link_rlib");
105 info!("preparing rlib to {:?}", out_filename);
108 archive_builder_builder,
113 .build(&out_filename);
115 CrateType::Staticlib => {
118 archive_builder_builder,
127 archive_builder_builder,
135 if sess.opts.json_artifact_notifications {
136 sess.parse_sess.span_diagnostic.emit_artifact_notification(&out_filename, "link");
139 if sess.prof.enabled() {
140 if let Some(artifact_name) = out_filename.file_name() {
141 // Record size for self-profiling
142 let file_size = std::fs::metadata(&out_filename).map(|m| m.len()).unwrap_or(0);
144 sess.prof.artifact_size(
146 artifact_name.to_string_lossy(),
154 // Remove the temporary object file and metadata if we aren't saving temps.
155 sess.time("link_binary_remove_temps", || {
156 // If the user requests that temporaries are saved, don't delete any.
157 if sess.opts.cg.save_temps {
161 let maybe_remove_temps_from_module =
162 |preserve_objects: bool, preserve_dwarf_objects: bool, module: &CompiledModule| {
163 if !preserve_objects {
164 if let Some(ref obj) = module.object {
165 ensure_removed(sess.diagnostic(), obj);
169 if !preserve_dwarf_objects {
170 if let Some(ref dwo_obj) = module.dwarf_object {
171 ensure_removed(sess.diagnostic(), dwo_obj);
176 let remove_temps_from_module =
177 |module: &CompiledModule| maybe_remove_temps_from_module(false, false, module);
179 // Otherwise, always remove the metadata and allocator module temporaries.
180 if let Some(ref metadata_module) = codegen_results.metadata_module {
181 remove_temps_from_module(metadata_module);
184 if let Some(ref allocator_module) = codegen_results.allocator_module {
185 remove_temps_from_module(allocator_module);
188 // If no requested outputs require linking, then the object temporaries should
190 if !sess.opts.output_types.should_link() {
194 // Potentially keep objects for their debuginfo.
195 let (preserve_objects, preserve_dwarf_objects) = preserve_objects_for_their_debuginfo(sess);
196 debug!(?preserve_objects, ?preserve_dwarf_objects);
198 for module in &codegen_results.modules {
199 maybe_remove_temps_from_module(preserve_objects, preserve_dwarf_objects, module);
206 pub fn each_linked_rlib(
208 f: &mut dyn FnMut(CrateNum, &Path),
209 ) -> Result<(), String> {
210 let crates = info.used_crates.iter();
212 for (ty, list) in info.dependency_formats.iter() {
214 CrateType::Executable
215 | CrateType::Staticlib
217 | CrateType::ProcMacro => {
224 let Some(fmts) = fmts else {
225 return Err("could not find formats for rlibs".to_string());
227 for &cnum in crates {
228 match fmts.get(cnum.as_usize() - 1) {
229 Some(&Linkage::NotLinked | &Linkage::IncludedFromDylib) => continue,
231 None => return Err("could not find formats for rlibs".to_string()),
233 let name = info.crate_name[&cnum];
234 let used_crate_source = &info.used_crate_source[&cnum];
235 if let Some((path, _)) = &used_crate_source.rlib {
238 if used_crate_source.rmeta.is_some() {
240 "could not find rlib for: `{}`, found rmeta (metadata) file",
244 return Err(format!("could not find rlib for: `{}`", name));
251 /// Create an 'rlib'.
253 /// An rlib in its current incarnation is essentially a renamed .a file. The rlib primarily contains
254 /// the object file of the crate, but it also contains all of the object files from native
255 /// libraries. This is done by unzipping native libraries and inserting all of the contents into
259 archive_builder_builder: &dyn ArchiveBuilderBuilder,
260 codegen_results: &CodegenResults,
262 tmpdir: &MaybeTempDir,
263 ) -> Result<Box<dyn ArchiveBuilder<'a> + 'a>, ErrorGuaranteed> {
264 let lib_search_paths = archive_search_paths(sess);
266 let mut ab = archive_builder_builder.new_archive_builder(sess);
268 let trailing_metadata = match flavor {
269 RlibFlavor::Normal => {
270 let (metadata, metadata_position) =
271 create_rmeta_file(sess, codegen_results.metadata.raw_data());
272 let metadata = emit_metadata(sess, &metadata, tmpdir);
273 match metadata_position {
274 MetadataPosition::First => {
275 // Most of the time metadata in rlib files is wrapped in a "dummy" object
276 // file for the target platform so the rlib can be processed entirely by
277 // normal linkers for the platform. Sometimes this is not possible however.
278 // If it is possible however, placing the metadata object first improves
279 // performance of getting metadata from rlibs.
280 ab.add_file(&metadata);
283 MetadataPosition::Last => Some(metadata),
287 RlibFlavor::StaticlibBase => None,
290 for m in &codegen_results.modules {
291 if let Some(obj) = m.object.as_ref() {
295 if let Some(dwarf_obj) = m.dwarf_object.as_ref() {
296 ab.add_file(dwarf_obj);
301 RlibFlavor::Normal => {}
302 RlibFlavor::StaticlibBase => {
303 let obj = codegen_results.allocator_module.as_ref().and_then(|m| m.object.as_ref());
304 if let Some(obj) = obj {
310 // Note that in this loop we are ignoring the value of `lib.cfg`. That is,
311 // we may not be configured to actually include a static library if we're
312 // adding it here. That's because later when we consume this rlib we'll
313 // decide whether we actually needed the static library or not.
315 // To do this "correctly" we'd need to keep track of which libraries added
316 // which object files to the archive. We don't do that here, however. The
317 // #[link(cfg(..))] feature is unstable, though, and only intended to get
318 // liblibc working. In that sense the check below just indicates that if
319 // there are any libraries we want to omit object files for at link time we
320 // just exclude all custom object files.
322 // Eventually if we want to stabilize or flesh out the #[link(cfg(..))]
323 // feature then we'll need to figure out how to record what objects were
324 // loaded from the libraries found here and then encode that into the
325 // metadata of the rlib we're generating somehow.
326 for lib in codegen_results.crate_info.used_libraries.iter() {
328 NativeLibKind::Static { bundle: None | Some(true), whole_archive: Some(true) }
329 if flavor == RlibFlavor::Normal =>
331 // Don't allow mixing +bundle with +whole_archive since an rlib may contain
332 // multiple native libs, some of which are +whole-archive and some of which are
333 // -whole-archive and it isn't clear how we can currently handle such a
334 // situation correctly.
335 // See https://github.com/rust-lang/rust/issues/88085#issuecomment-901050897
337 "the linking modifiers `+bundle` and `+whole-archive` are not compatible \
338 with each other when generating rlibs",
341 NativeLibKind::Static { bundle: None | Some(true), .. } => {}
342 NativeLibKind::Static { bundle: Some(false), .. }
343 | NativeLibKind::Dylib { .. }
344 | NativeLibKind::Framework { .. }
345 | NativeLibKind::RawDylib
346 | NativeLibKind::LinkArg
347 | NativeLibKind::Unspecified => continue,
349 if let Some(name) = lib.name {
351 find_library(name.as_str(), lib.verbatim.unwrap_or(false), &lib_search_paths, sess);
352 ab.add_archive(&location, Box::new(|_| false)).unwrap_or_else(|e| {
354 "failed to add native library {}: {}",
355 location.to_string_lossy(),
362 for (raw_dylib_name, raw_dylib_imports) in
363 collate_raw_dylibs(sess, &codegen_results.crate_info.used_libraries)?
365 let output_path = archive_builder_builder.create_dll_import_lib(
372 ab.add_archive(&output_path, Box::new(|_| false)).unwrap_or_else(|e| {
373 sess.fatal(&format!("failed to add native library {}: {}", output_path.display(), e));
377 if let Some(trailing_metadata) = trailing_metadata {
378 // Note that it is important that we add all of our non-object "magical
379 // files" *after* all of the object files in the archive. The reason for
380 // this is as follows:
382 // * When performing LTO, this archive will be modified to remove
383 // objects from above. The reason for this is described below.
385 // * When the system linker looks at an archive, it will attempt to
386 // determine the architecture of the archive in order to see whether its
389 // The algorithm for this detection is: iterate over the files in the
390 // archive. Skip magical SYMDEF names. Interpret the first file as an
391 // object file. Read architecture from the object file.
393 // * As one can probably see, if "metadata" and "foo.bc" were placed
394 // before all of the objects, then the architecture of this archive would
395 // not be correctly inferred once 'foo.o' is removed.
397 // * Most of the time metadata in rlib files is wrapped in a "dummy" object
398 // file for the target platform so the rlib can be processed entirely by
399 // normal linkers for the platform. Sometimes this is not possible however.
401 // Basically, all this means is that this code should not move above the
403 ab.add_file(&trailing_metadata);
409 /// Extract all symbols defined in raw-dylib libraries, collated by library name.
411 /// If we have multiple extern blocks that specify symbols defined in the same raw-dylib library,
412 /// then the CodegenResults value contains one NativeLib instance for each block. However, the
413 /// linker appears to expect only a single import library for each library used, so we need to
414 /// collate the symbols together by library name before generating the import libraries.
415 fn collate_raw_dylibs(
417 used_libraries: &[NativeLib],
418 ) -> Result<Vec<(String, Vec<DllImport>)>, ErrorGuaranteed> {
419 // Use index maps to preserve original order of imports and libraries.
420 let mut dylib_table = FxIndexMap::<String, FxIndexMap<Symbol, &DllImport>>::default();
422 for lib in used_libraries {
423 if lib.kind == NativeLibKind::RawDylib {
424 let ext = if matches!(lib.verbatim, Some(true)) { "" } else { ".dll" };
425 let name = format!("{}{}", lib.name.expect("unnamed raw-dylib library"), ext);
426 let imports = dylib_table.entry(name.clone()).or_default();
427 for import in &lib.dll_imports {
428 if let Some(old_import) = imports.insert(import.name, import) {
429 // FIXME: when we add support for ordinals, figure out if we need to do anything
430 // if we have two DllImport values with the same name but different ordinals.
431 if import.calling_convention != old_import.calling_convention {
435 "multiple declarations of external function `{}` from \
436 library `{}` have different calling conventions",
445 sess.compile_status()?;
448 .map(|(name, imports)| {
449 (name, imports.into_iter().map(|(_, import)| import.clone()).collect())
454 /// Create a static archive.
456 /// This is essentially the same thing as an rlib, but it also involves adding all of the upstream
457 /// crates' objects into the archive. This will slurp in all of the native libraries of upstream
458 /// dependencies as well.
460 /// Additionally, there's no way for us to link dynamic libraries, so we warn about all dynamic
461 /// library dependencies that they're not linked in.
463 /// There's no need to include metadata in a static archive, so ensure to not link in the metadata
464 /// object file (and also don't prepare the archive with a metadata file).
465 fn link_staticlib<'a>(
467 archive_builder_builder: &dyn ArchiveBuilderBuilder,
468 codegen_results: &CodegenResults,
470 tempdir: &MaybeTempDir,
471 ) -> Result<(), ErrorGuaranteed> {
472 info!("preparing staticlib to {:?}", out_filename);
473 let mut ab = link_rlib(
475 archive_builder_builder,
477 RlibFlavor::StaticlibBase,
480 let mut all_native_libs = vec![];
482 let res = each_linked_rlib(&codegen_results.crate_info, &mut |cnum, path| {
483 let name = codegen_results.crate_info.crate_name[&cnum];
484 let native_libs = &codegen_results.crate_info.native_libraries[&cnum];
486 // Here when we include the rlib into our staticlib we need to make a
487 // decision whether to include the extra object files along the way.
488 // These extra object files come from statically included native
489 // libraries, but they may be cfg'd away with #[link(cfg(..))].
491 // This unstable feature, though, only needs liblibc to work. The only
492 // use case there is where musl is statically included in liblibc.rlib,
493 // so if we don't want the included version we just need to skip it. As
494 // a result the logic here is that if *any* linked library is cfg'd away
495 // we just skip all object files.
497 // Clearly this is not sufficient for a general purpose feature, and
498 // we'd want to read from the library's metadata to determine which
499 // object files come from where and selectively skip them.
500 let skip_object_files = native_libs.iter().any(|lib| {
501 matches!(lib.kind, NativeLibKind::Static { bundle: None | Some(true), .. })
502 && !relevant_lib(sess, lib)
505 let lto = are_upstream_rust_objects_already_included(sess)
506 && !ignored_for_lto(sess, &codegen_results.crate_info, cnum);
508 // Ignoring obj file starting with the crate name
509 // as simple comparison is not enough - there
510 // might be also an extra name suffix
511 let obj_start = name.as_str().to_owned();
515 Box::new(move |fname: &str| {
516 // Ignore metadata files, no matter the name.
517 if fname == METADATA_FILENAME {
521 // Don't include Rust objects if LTO is enabled
522 if lto && looks_like_rust_object_file(fname) {
526 // Otherwise if this is *not* a rust object and we're skipping
527 // objects then skip this file
528 if skip_object_files && (!fname.starts_with(&obj_start) || !fname.ends_with(".o")) {
532 // ok, don't skip this
538 all_native_libs.extend(codegen_results.crate_info.native_libraries[&cnum].iter().cloned());
540 if let Err(e) = res {
544 ab.build(out_filename);
546 if !all_native_libs.is_empty() {
547 if sess.opts.prints.contains(&PrintRequest::NativeStaticLibs) {
548 print_native_static_libs(sess, &all_native_libs);
555 /// Use `thorin` (rust implementation of a dwarf packaging utility) to link DWARF objects into a
557 fn link_dwarf_object<'a>(
559 cg_results: &CodegenResults,
560 executable_out_filename: &Path,
562 let dwp_out_filename = executable_out_filename.with_extension("dwp");
563 debug!(?dwp_out_filename, ?executable_out_filename);
566 struct ThorinSession<Relocations> {
567 arena_data: TypedArena<Vec<u8>>,
568 arena_mmap: TypedArena<Mmap>,
569 arena_relocations: TypedArena<Relocations>,
572 impl<Relocations> ThorinSession<Relocations> {
573 fn alloc_mmap<'arena>(&'arena self, data: Mmap) -> &'arena Mmap {
574 (*self.arena_mmap.alloc(data)).borrow()
578 impl<Relocations> thorin::Session<Relocations> for ThorinSession<Relocations> {
579 fn alloc_data<'arena>(&'arena self, data: Vec<u8>) -> &'arena [u8] {
580 (*self.arena_data.alloc(data)).borrow()
583 fn alloc_relocation<'arena>(&'arena self, data: Relocations) -> &'arena Relocations {
584 (*self.arena_relocations.alloc(data)).borrow()
587 fn read_input<'arena>(&'arena self, path: &Path) -> std::io::Result<&'arena [u8]> {
588 let file = File::open(&path)?;
589 let mmap = (unsafe { Mmap::map(file) })?;
590 Ok(self.alloc_mmap(mmap))
594 match sess.time("run_thorin", || -> Result<(), thorin::Error> {
595 let thorin_sess = ThorinSession::default();
596 let mut package = thorin::DwarfPackage::new(&thorin_sess);
598 // Input objs contain .o/.dwo files from the current crate.
599 match sess.opts.unstable_opts.split_dwarf_kind {
600 SplitDwarfKind::Single => {
601 for input_obj in cg_results.modules.iter().filter_map(|m| m.object.as_ref()) {
602 package.add_input_object(input_obj)?;
605 SplitDwarfKind::Split => {
606 for input_obj in cg_results.modules.iter().filter_map(|m| m.dwarf_object.as_ref()) {
607 package.add_input_object(input_obj)?;
612 // Input rlibs contain .o/.dwo files from dependencies.
613 let input_rlibs = cg_results
617 .filter_map(|csource| csource.rlib.as_ref())
618 .map(|(path, _)| path);
619 for input_rlib in input_rlibs {
621 package.add_input_object(input_rlib)?;
624 // Failing to read the referenced objects is expected for dependencies where the path in the
625 // executable will have been cleaned by Cargo, but the referenced objects will be contained
626 // within rlibs provided as inputs.
628 // If paths have been remapped, then .o/.dwo files from the current crate also won't be
629 // found, but are provided explicitly above.
631 // Adding an executable is primarily done to make `thorin` check that all the referenced
632 // dwarf objects are found in the end.
633 package.add_executable(
634 &executable_out_filename,
635 thorin::MissingReferencedObjectBehaviour::Skip,
638 let output = package.finish()?.write()?;
639 let mut output_stream = BufWriter::new(
645 .open(dwp_out_filename)?,
647 output_stream.write_all(&output)?;
648 output_stream.flush()?;
654 sess.struct_err("linking dwarf objects with thorin failed")
655 .note(&format!("{:?}", e))
657 sess.abort_if_errors();
662 /// Create a dynamic library or executable.
664 /// This will invoke the system linker/cc to create the resulting file. This links to all upstream
666 fn link_natively<'a>(
668 archive_builder_builder: &dyn ArchiveBuilderBuilder,
669 crate_type: CrateType,
671 codegen_results: &CodegenResults,
673 ) -> Result<(), ErrorGuaranteed> {
674 info!("preparing {:?} to {:?}", crate_type, out_filename);
675 let (linker_path, flavor) = linker_and_flavor(sess);
676 let mut cmd = linker_with_args(
680 archive_builder_builder,
687 linker::disable_localization(&mut cmd);
689 for &(ref k, ref v) in sess.target.link_env.as_ref() {
690 cmd.env(k.as_ref(), v.as_ref());
692 for k in sess.target.link_env_remove.as_ref() {
693 cmd.env_remove(k.as_ref());
696 if sess.opts.prints.contains(&PrintRequest::LinkArgs) {
697 println!("{:?}", &cmd);
700 // May have not found libraries in the right formats.
701 sess.abort_if_errors();
703 // Invoke the system linker
705 let retry_on_segfault = env::var("RUSTC_RETRY_LINKER_ON_SEGFAULT").is_ok();
706 let unknown_arg_regex =
707 Regex::new(r"(unknown|unrecognized) (command line )?(option|argument)").unwrap();
712 prog = sess.time("run_linker", || exec_linker(sess, &cmd, out_filename, tmpdir));
713 let Ok(ref output) = prog else {
716 if output.status.success() {
719 let mut out = output.stderr.clone();
720 out.extend(&output.stdout);
721 let out = String::from_utf8_lossy(&out);
723 // Check to see if the link failed with an error message that indicates it
724 // doesn't recognize the -no-pie option. If so, re-perform the link step
725 // without it. This is safe because if the linker doesn't support -no-pie
726 // then it should not default to linking executables as pie. Different
727 // versions of gcc seem to use different quotes in the error message so
728 // don't check for them.
729 if sess.target.linker_is_gnu
730 && flavor != LinkerFlavor::Ld
731 && unknown_arg_regex.is_match(&out)
732 && out.contains("-no-pie")
733 && cmd.get_args().iter().any(|e| e.to_string_lossy() == "-no-pie")
735 info!("linker output: {:?}", out);
736 warn!("Linker does not support -no-pie command line option. Retrying without.");
737 for arg in cmd.take_args() {
738 if arg.to_string_lossy() != "-no-pie" {
746 // Detect '-static-pie' used with an older version of gcc or clang not supporting it.
747 // Fallback from '-static-pie' to '-static' in that case.
748 if sess.target.linker_is_gnu
749 && flavor != LinkerFlavor::Ld
750 && unknown_arg_regex.is_match(&out)
751 && (out.contains("-static-pie") || out.contains("--no-dynamic-linker"))
752 && cmd.get_args().iter().any(|e| e.to_string_lossy() == "-static-pie")
754 info!("linker output: {:?}", out);
756 "Linker does not support -static-pie command line option. Retrying with -static instead."
758 // Mirror `add_(pre,post)_link_objects` to replace CRT objects.
759 let self_contained = self_contained(sess, crate_type);
760 let opts = &sess.target;
761 let pre_objects = if self_contained {
762 &opts.pre_link_objects_self_contained
764 &opts.pre_link_objects
766 let post_objects = if self_contained {
767 &opts.post_link_objects_self_contained
769 &opts.post_link_objects
771 let get_objects = |objects: &CrtObjects, kind| {
777 .map(|obj| get_object_file_path(sess, obj, self_contained).into_os_string())
780 let pre_objects_static_pie = get_objects(pre_objects, LinkOutputKind::StaticPicExe);
781 let post_objects_static_pie = get_objects(post_objects, LinkOutputKind::StaticPicExe);
782 let mut pre_objects_static = get_objects(pre_objects, LinkOutputKind::StaticNoPicExe);
783 let mut post_objects_static = get_objects(post_objects, LinkOutputKind::StaticNoPicExe);
784 // Assume that we know insertion positions for the replacement arguments from replaced
785 // arguments, which is true for all supported targets.
786 assert!(pre_objects_static.is_empty() || !pre_objects_static_pie.is_empty());
787 assert!(post_objects_static.is_empty() || !post_objects_static_pie.is_empty());
788 for arg in cmd.take_args() {
789 if arg.to_string_lossy() == "-static-pie" {
790 // Replace the output kind.
792 } else if pre_objects_static_pie.contains(&arg) {
793 // Replace the pre-link objects (replace the first and remove the rest).
794 cmd.args(mem::take(&mut pre_objects_static));
795 } else if post_objects_static_pie.contains(&arg) {
796 // Replace the post-link objects (replace the first and remove the rest).
797 cmd.args(mem::take(&mut post_objects_static));
806 // Here's a terribly awful hack that really shouldn't be present in any
807 // compiler. Here an environment variable is supported to automatically
808 // retry the linker invocation if the linker looks like it segfaulted.
810 // Gee that seems odd, normally segfaults are things we want to know
811 // about! Unfortunately though in rust-lang/rust#38878 we're
812 // experiencing the linker segfaulting on Travis quite a bit which is
813 // causing quite a bit of pain to land PRs when they spuriously fail
814 // due to a segfault.
816 // The issue #38878 has some more debugging information on it as well,
817 // but this unfortunately looks like it's just a race condition in
818 // macOS's linker with some thread pool working in the background. It
819 // seems that no one currently knows a fix for this so in the meantime
820 // we're left with this...
821 if !retry_on_segfault || i > 3 {
824 let msg_segv = "clang: error: unable to execute command: Segmentation fault: 11";
825 let msg_bus = "clang: error: unable to execute command: Bus error: 10";
826 if out.contains(msg_segv) || out.contains(msg_bus) {
829 "looks like the linker segfaulted when we tried to call it, \
830 automatically retrying again",
835 if is_illegal_instruction(&output.status) {
837 ?cmd, %out, status = %output.status,
838 "looks like the linker hit an illegal instruction when we \
839 tried to call it, automatically retrying again.",
845 fn is_illegal_instruction(status: &ExitStatus) -> bool {
846 use std::os::unix::prelude::*;
847 status.signal() == Some(libc::SIGILL)
851 fn is_illegal_instruction(_status: &ExitStatus) -> bool {
858 if !prog.status.success() {
859 let mut output = prog.stderr.clone();
860 output.extend_from_slice(&prog.stdout);
861 let escaped_output = escape_string(&output);
862 let mut err = sess.struct_err(&format!(
863 "linking with `{}` failed: {}",
864 linker_path.display(),
867 err.note(&format!("{:?}", &cmd)).note(&escaped_output);
868 if escaped_output.contains("undefined reference to") {
870 "some `extern` functions couldn't be found; some native libraries may \
871 need to be installed or have their path specified",
873 err.note("use the `-l` flag to specify native libraries to link");
874 err.note("use the `cargo:rustc-link-lib` directive to specify the native \
875 libraries to link with Cargo (see https://doc.rust-lang.org/cargo/reference/build-scripts.html#cargorustc-link-libkindname)");
879 // If MSVC's `link.exe` was expected but the return code
880 // is not a Microsoft LNK error then suggest a way to fix or
881 // install the Visual Studio build tools.
882 if let Some(code) = prog.status.code() {
883 if sess.target.is_like_msvc
884 && flavor == LinkerFlavor::Msvc
885 // Respect the command line override
886 && sess.opts.cg.linker.is_none()
887 // Match exactly "link.exe"
888 && linker_path.to_str() == Some("link.exe")
889 // All Microsoft `link.exe` linking error codes are
890 // four digit numbers in the range 1000 to 9999 inclusive
891 && (code < 1000 || code > 9999)
893 let is_vs_installed = windows_registry::find_vs_version().is_ok();
894 let has_linker = windows_registry::find_tool(
895 &sess.opts.target_triple.triple(),
900 sess.note_without_error("`link.exe` returned an unexpected error");
901 if is_vs_installed && has_linker {
902 // the linker is broken
903 sess.note_without_error(
904 "the Visual Studio build tools may need to be repaired \
905 using the Visual Studio installer",
907 sess.note_without_error(
908 "or a necessary component may be missing from the \
909 \"C++ build tools\" workload",
911 } else if is_vs_installed {
912 // the linker is not installed
913 sess.note_without_error(
914 "in the Visual Studio installer, ensure the \
915 \"C++ build tools\" workload is selected",
918 // visual studio is not installed
919 sess.note_without_error(
920 "you may need to install Visual Studio build tools with the \
921 \"C++ build tools\" workload",
927 sess.abort_if_errors();
929 info!("linker stderr:\n{}", escape_string(&prog.stderr));
930 info!("linker stdout:\n{}", escape_string(&prog.stdout));
933 let linker_not_found = e.kind() == io::ErrorKind::NotFound;
935 let mut linker_error = {
936 if linker_not_found {
937 sess.struct_err(&format!("linker `{}` not found", linker_path.display()))
939 sess.struct_err(&format!(
940 "could not exec the linker `{}`",
941 linker_path.display()
946 linker_error.note(&e.to_string());
948 if !linker_not_found {
949 linker_error.note(&format!("{:?}", &cmd));
954 if sess.target.is_like_msvc && linker_not_found {
955 sess.note_without_error(
956 "the msvc targets depend on the msvc linker \
957 but `link.exe` was not found",
959 sess.note_without_error(
960 "please ensure that VS 2013, VS 2015, VS 2017, VS 2019 or VS 2022 \
961 was installed with the Visual C++ option",
964 sess.abort_if_errors();
968 match sess.split_debuginfo() {
969 // If split debug information is disabled or located in individual files
970 // there's nothing to do here.
971 SplitDebuginfo::Off | SplitDebuginfo::Unpacked => {}
973 // If packed split-debuginfo is requested, but the final compilation
974 // doesn't actually have any debug information, then we skip this step.
975 SplitDebuginfo::Packed if sess.opts.debuginfo == DebugInfo::None => {}
977 // On macOS the external `dsymutil` tool is used to create the packed
978 // debug information. Note that this will read debug information from
979 // the objects on the filesystem which we'll clean up later.
980 SplitDebuginfo::Packed if sess.target.is_like_osx => {
981 let prog = Command::new("dsymutil").arg(out_filename).output();
984 if !prog.status.success() {
985 let mut output = prog.stderr.clone();
986 output.extend_from_slice(&prog.stdout);
987 sess.struct_warn(&format!(
988 "processing debug info with `dsymutil` failed: {}",
991 .note(&escape_string(&output))
995 Err(e) => sess.fatal(&format!("unable to run `dsymutil`: {}", e)),
999 // On MSVC packed debug information is produced by the linker itself so
1000 // there's no need to do anything else here.
1001 SplitDebuginfo::Packed if sess.target.is_like_windows => {}
1003 // ... and otherwise we're processing a `*.dwp` packed dwarf file.
1005 // We cannot rely on the .o paths in the executable because they may have been
1006 // remapped by --remap-path-prefix and therefore invalid, so we need to provide
1007 // the .o/.dwo paths explicitly.
1008 SplitDebuginfo::Packed => link_dwarf_object(sess, codegen_results, out_filename),
1011 let strip = strip_value(sess);
1013 if sess.target.is_like_osx {
1014 match (strip, crate_type) {
1015 (Strip::Debuginfo, _) => strip_symbols_in_osx(sess, &out_filename, Some("-S")),
1016 // Per the manpage, `-x` is the maximum safe strip level for dynamic libraries. (#93988)
1017 (Strip::Symbols, CrateType::Dylib | CrateType::Cdylib | CrateType::ProcMacro) => {
1018 strip_symbols_in_osx(sess, &out_filename, Some("-x"))
1020 (Strip::Symbols, _) => strip_symbols_in_osx(sess, &out_filename, None),
1021 (Strip::None, _) => {}
1028 // Temporarily support both -Z strip and -C strip
1029 fn strip_value(sess: &Session) -> Strip {
1030 match (sess.opts.unstable_opts.strip, sess.opts.cg.strip) {
1031 (s, Strip::None) => s,
1036 fn strip_symbols_in_osx<'a>(sess: &'a Session, out_filename: &Path, option: Option<&str>) {
1037 let mut cmd = Command::new("strip");
1038 if let Some(option) = option {
1041 let prog = cmd.arg(out_filename).output();
1044 if !prog.status.success() {
1045 let mut output = prog.stderr.clone();
1046 output.extend_from_slice(&prog.stdout);
1047 sess.struct_warn(&format!(
1048 "stripping debug info with `strip` failed: {}",
1051 .note(&escape_string(&output))
1055 Err(e) => sess.fatal(&format!("unable to run `strip`: {}", e)),
1059 fn escape_string(s: &[u8]) -> String {
1060 match str::from_utf8(s) {
1061 Ok(s) => s.to_owned(),
1062 Err(_) => format!("Non-UTF-8 output: {}", s.escape_ascii()),
1066 fn add_sanitizer_libraries(sess: &Session, crate_type: CrateType, linker: &mut dyn Linker) {
1067 // On macOS the runtimes are distributed as dylibs which should be linked to
1068 // both executables and dynamic shared objects. Everywhere else the runtimes
1069 // are currently distributed as static libraries which should be linked to
1070 // executables only.
1071 let needs_runtime = match crate_type {
1072 CrateType::Executable => true,
1073 CrateType::Dylib | CrateType::Cdylib | CrateType::ProcMacro => sess.target.is_like_osx,
1074 CrateType::Rlib | CrateType::Staticlib => false,
1081 let sanitizer = sess.opts.unstable_opts.sanitizer;
1082 if sanitizer.contains(SanitizerSet::ADDRESS) {
1083 link_sanitizer_runtime(sess, linker, "asan");
1085 if sanitizer.contains(SanitizerSet::LEAK) {
1086 link_sanitizer_runtime(sess, linker, "lsan");
1088 if sanitizer.contains(SanitizerSet::MEMORY) {
1089 link_sanitizer_runtime(sess, linker, "msan");
1091 if sanitizer.contains(SanitizerSet::THREAD) {
1092 link_sanitizer_runtime(sess, linker, "tsan");
1094 if sanitizer.contains(SanitizerSet::HWADDRESS) {
1095 link_sanitizer_runtime(sess, linker, "hwasan");
1099 fn link_sanitizer_runtime(sess: &Session, linker: &mut dyn Linker, name: &str) {
1100 fn find_sanitizer_runtime(sess: &Session, filename: &str) -> PathBuf {
1102 filesearch::make_target_lib_path(&sess.sysroot, sess.opts.target_triple.triple());
1103 let path = session_tlib.join(filename);
1105 return session_tlib;
1107 let default_sysroot = filesearch::get_or_default_sysroot();
1108 let default_tlib = filesearch::make_target_lib_path(
1110 sess.opts.target_triple.triple(),
1112 return default_tlib;
1116 let channel = option_env!("CFG_RELEASE_CHANNEL")
1117 .map(|channel| format!("-{}", channel))
1118 .unwrap_or_default();
1120 if sess.target.is_like_osx {
1121 // On Apple platforms, the sanitizer is always built as a dylib, and
1122 // LLVM will link to `@rpath/*.dylib`, so we need to specify an
1123 // rpath to the library as well (the rpath should be absolute, see
1124 // PR #41352 for details).
1125 let filename = format!("rustc{}_rt.{}", channel, name);
1126 let path = find_sanitizer_runtime(&sess, &filename);
1127 let rpath = path.to_str().expect("non-utf8 component in path");
1128 linker.args(&["-Wl,-rpath", "-Xlinker", rpath]);
1129 linker.link_dylib(&filename, false, true);
1131 let filename = format!("librustc{}_rt.{}.a", channel, name);
1132 let path = find_sanitizer_runtime(&sess, &filename).join(&filename);
1133 linker.link_whole_rlib(&path);
1137 /// Returns a boolean indicating whether the specified crate should be ignored
1140 /// Crates ignored during LTO are not lumped together in the "massive object
1141 /// file" that we create and are linked in their normal rlib states. See
1142 /// comments below for what crates do not participate in LTO.
1144 /// It's unusual for a crate to not participate in LTO. Typically only
1145 /// compiler-specific and unstable crates have a reason to not participate in
1147 pub fn ignored_for_lto(sess: &Session, info: &CrateInfo, cnum: CrateNum) -> bool {
1148 // If our target enables builtin function lowering in LLVM then the
1149 // crates providing these functions don't participate in LTO (e.g.
1150 // no_builtins or compiler builtins crates).
1151 !sess.target.no_builtins
1152 && (info.compiler_builtins == Some(cnum) || info.is_no_builtins.contains(&cnum))
1155 // This functions tries to determine the appropriate linker (and corresponding LinkerFlavor) to use
1156 pub fn linker_and_flavor(sess: &Session) -> (PathBuf, LinkerFlavor) {
1159 linker: Option<PathBuf>,
1160 flavor: Option<LinkerFlavor>,
1161 ) -> Option<(PathBuf, LinkerFlavor)> {
1162 match (linker, flavor) {
1163 (Some(linker), Some(flavor)) => Some((linker, flavor)),
1164 // only the linker flavor is known; use the default linker for the selected flavor
1165 (None, Some(flavor)) => Some((
1166 PathBuf::from(match flavor {
1167 LinkerFlavor::Em => {
1174 LinkerFlavor::Gcc => {
1175 if cfg!(any(target_os = "solaris", target_os = "illumos")) {
1176 // On historical Solaris systems, "cc" may have
1177 // been Sun Studio, which is not flag-compatible
1178 // with "gcc". This history casts a long shadow,
1179 // and many modern illumos distributions today
1180 // ship GCC as "gcc" without also making it
1181 // available as "cc".
1187 LinkerFlavor::Ld => "ld",
1188 LinkerFlavor::Msvc => "link.exe",
1189 LinkerFlavor::Lld(_) => "lld",
1190 LinkerFlavor::PtxLinker => "rust-ptx-linker",
1191 LinkerFlavor::BpfLinker => "bpf-linker",
1192 LinkerFlavor::L4Bender => "l4-bender",
1196 (Some(linker), None) => {
1197 let stem = linker.file_stem().and_then(|stem| stem.to_str()).unwrap_or_else(|| {
1198 sess.fatal("couldn't extract file stem from specified linker")
1201 let flavor = if stem == "emcc" {
1203 } else if stem == "gcc"
1204 || stem.ends_with("-gcc")
1206 || stem.ends_with("-clang")
1209 } else if stem == "wasm-ld" || stem.ends_with("-wasm-ld") {
1210 LinkerFlavor::Lld(LldFlavor::Wasm)
1211 } else if stem == "ld" || stem == "ld.lld" || stem.ends_with("-ld") {
1213 } else if stem == "link" || stem == "lld-link" {
1215 } else if stem == "lld" || stem == "rust-lld" {
1216 LinkerFlavor::Lld(sess.target.lld_flavor)
1218 // fall back to the value in the target spec
1219 sess.target.linker_flavor
1222 Some((linker, flavor))
1224 (None, None) => None,
1228 // linker and linker flavor specified via command line have precedence over what the target
1229 // specification specifies
1230 if let Some(ret) = infer_from(sess, sess.opts.cg.linker.clone(), sess.opts.cg.linker_flavor) {
1234 if let Some(ret) = infer_from(
1236 sess.target.linker.as_deref().map(PathBuf::from),
1237 Some(sess.target.linker_flavor),
1242 bug!("Not enough information provided to determine how to invoke the linker");
1245 /// Returns a pair of boolean indicating whether we should preserve the object and
1246 /// dwarf object files on the filesystem for their debug information. This is often
1247 /// useful with split-dwarf like schemes.
1248 fn preserve_objects_for_their_debuginfo(sess: &Session) -> (bool, bool) {
1249 // If the objects don't have debuginfo there's nothing to preserve.
1250 if sess.opts.debuginfo == config::DebugInfo::None {
1251 return (false, false);
1254 // If we're only producing artifacts that are archives, no need to preserve
1255 // the objects as they're losslessly contained inside the archives.
1256 if sess.crate_types().iter().all(|&x| x.is_archive()) {
1257 return (false, false);
1260 match (sess.split_debuginfo(), sess.opts.unstable_opts.split_dwarf_kind) {
1261 // If there is no split debuginfo then do not preserve objects.
1262 (SplitDebuginfo::Off, _) => (false, false),
1263 // If there is packed split debuginfo, then the debuginfo in the objects
1264 // has been packaged and the objects can be deleted.
1265 (SplitDebuginfo::Packed, _) => (false, false),
1266 // If there is unpacked split debuginfo and the current target can not use
1267 // split dwarf, then keep objects.
1268 (SplitDebuginfo::Unpacked, _) if !sess.target_can_use_split_dwarf() => (true, false),
1269 // If there is unpacked split debuginfo and the target can use split dwarf, then
1270 // keep the object containing that debuginfo (whether that is an object file or
1271 // dwarf object file depends on the split dwarf kind).
1272 (SplitDebuginfo::Unpacked, SplitDwarfKind::Single) => (true, false),
1273 (SplitDebuginfo::Unpacked, SplitDwarfKind::Split) => (false, true),
1277 fn archive_search_paths(sess: &Session) -> Vec<PathBuf> {
1278 sess.target_filesearch(PathKind::Native).search_path_dirs()
1281 #[derive(PartialEq)]
1287 fn print_native_static_libs(sess: &Session, all_native_libs: &[NativeLib]) {
1288 let lib_args: Vec<_> = all_native_libs
1290 .filter(|l| relevant_lib(sess, l))
1292 let name = lib.name?;
1294 NativeLibKind::Static { bundle: Some(false), .. }
1295 | NativeLibKind::Dylib { .. }
1296 | NativeLibKind::Unspecified => {
1297 let verbatim = lib.verbatim.unwrap_or(false);
1298 if sess.target.is_like_msvc {
1299 Some(format!("{}{}", name, if verbatim { "" } else { ".lib" }))
1300 } else if sess.target.linker_is_gnu {
1301 Some(format!("-l{}{}", if verbatim { ":" } else { "" }, name))
1303 Some(format!("-l{}", name))
1306 NativeLibKind::Framework { .. } => {
1307 // ld-only syntax, since there are no frameworks in MSVC
1308 Some(format!("-framework {}", name))
1310 // These are included, no need to print them
1311 NativeLibKind::Static { bundle: None | Some(true), .. }
1312 | NativeLibKind::LinkArg
1313 | NativeLibKind::RawDylib => None,
1317 if !lib_args.is_empty() {
1318 sess.note_without_error(
1319 "Link against the following native artifacts when linking \
1320 against this static library. The order and any duplication \
1321 can be significant on some platforms.",
1323 // Prefix for greppability
1324 sess.note_without_error(&format!("native-static-libs: {}", &lib_args.join(" ")));
1328 fn get_object_file_path(sess: &Session, name: &str, self_contained: bool) -> PathBuf {
1329 let fs = sess.target_filesearch(PathKind::Native);
1330 let file_path = fs.get_lib_path().join(name);
1331 if file_path.exists() {
1334 // Special directory with objects used only in self-contained linkage mode
1336 let file_path = fs.get_self_contained_lib_path().join(name);
1337 if file_path.exists() {
1341 for search_path in fs.search_paths() {
1342 let file_path = search_path.dir.join(name);
1343 if file_path.exists() {
1353 out_filename: &Path,
1355 ) -> io::Result<Output> {
1356 // When attempting to spawn the linker we run a risk of blowing out the
1357 // size limits for spawning a new process with respect to the arguments
1358 // we pass on the command line.
1360 // Here we attempt to handle errors from the OS saying "your list of
1361 // arguments is too big" by reinvoking the linker again with an `@`-file
1362 // that contains all the arguments. The theory is that this is then
1363 // accepted on all linkers and the linker will read all its options out of
1364 // there instead of looking at the command line.
1365 if !cmd.very_likely_to_exceed_some_spawn_limit() {
1366 match cmd.command().stdout(Stdio::piped()).stderr(Stdio::piped()).spawn() {
1368 let output = child.wait_with_output();
1369 flush_linked_file(&output, out_filename)?;
1372 Err(ref e) if command_line_too_big(e) => {
1373 info!("command line to linker was too big: {}", e);
1375 Err(e) => return Err(e),
1379 info!("falling back to passing arguments to linker via an @-file");
1380 let mut cmd2 = cmd.clone();
1381 let mut args = String::new();
1382 for arg in cmd2.take_args() {
1384 &Escape { arg: arg.to_str().unwrap(), is_like_msvc: sess.target.is_like_msvc }
1389 let file = tmpdir.join("linker-arguments");
1390 let bytes = if sess.target.is_like_msvc {
1391 let mut out = Vec::with_capacity((1 + args.len()) * 2);
1392 // start the stream with a UTF-16 BOM
1393 for c in std::iter::once(0xFEFF).chain(args.encode_utf16()) {
1394 // encode in little endian
1396 out.push((c >> 8) as u8);
1402 fs::write(&file, &bytes)?;
1403 cmd2.arg(format!("@{}", file.display()));
1404 info!("invoking linker {:?}", cmd2);
1405 let output = cmd2.output();
1406 flush_linked_file(&output, out_filename)?;
1409 #[cfg(not(windows))]
1410 fn flush_linked_file(_: &io::Result<Output>, _: &Path) -> io::Result<()> {
1415 fn flush_linked_file(
1416 command_output: &io::Result<Output>,
1417 out_filename: &Path,
1418 ) -> io::Result<()> {
1419 // On Windows, under high I/O load, output buffers are sometimes not flushed,
1420 // even long after process exit, causing nasty, non-reproducible output bugs.
1422 // File::sync_all() calls FlushFileBuffers() down the line, which solves the problem.
1424 // А full writeup of the original Chrome bug can be found at
1425 // randomascii.wordpress.com/2018/02/25/compiler-bug-linker-bug-windows-kernel-bug/amp
1427 if let &Ok(ref out) = command_output {
1428 if out.status.success() {
1429 if let Ok(of) = fs::OpenOptions::new().write(true).open(out_filename) {
1439 fn command_line_too_big(err: &io::Error) -> bool {
1440 err.raw_os_error() == Some(::libc::E2BIG)
1444 fn command_line_too_big(err: &io::Error) -> bool {
1445 const ERROR_FILENAME_EXCED_RANGE: i32 = 206;
1446 err.raw_os_error() == Some(ERROR_FILENAME_EXCED_RANGE)
1449 #[cfg(not(any(unix, windows)))]
1450 fn command_line_too_big(_: &io::Error) -> bool {
1459 impl<'a> fmt::Display for Escape<'a> {
1460 fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
1461 if self.is_like_msvc {
1462 // This is "documented" at
1463 // https://docs.microsoft.com/en-us/cpp/build/reference/at-specify-a-linker-response-file
1465 // Unfortunately there's not a great specification of the
1466 // syntax I could find online (at least) but some local
1467 // testing showed that this seemed sufficient-ish to catch
1468 // at least a few edge cases.
1470 for c in self.arg.chars() {
1472 '"' => write!(f, "\\{}", c)?,
1473 c => write!(f, "{}", c)?,
1478 // This is documented at https://linux.die.net/man/1/ld, namely:
1480 // > Options in file are separated by whitespace. A whitespace
1481 // > character may be included in an option by surrounding the
1482 // > entire option in either single or double quotes. Any
1483 // > character (including a backslash) may be included by
1484 // > prefixing the character to be included with a backslash.
1486 // We put an argument on each line, so all we need to do is
1487 // ensure the line is interpreted as one whole argument.
1488 for c in self.arg.chars() {
1490 '\\' | ' ' => write!(f, "\\{}", c)?,
1491 c => write!(f, "{}", c)?,
1500 fn link_output_kind(sess: &Session, crate_type: CrateType) -> LinkOutputKind {
1501 let kind = match (crate_type, sess.crt_static(Some(crate_type)), sess.relocation_model()) {
1502 (CrateType::Executable, _, _) if sess.is_wasi_reactor() => LinkOutputKind::WasiReactorExe,
1503 (CrateType::Executable, false, RelocModel::Pic | RelocModel::Pie) => {
1504 LinkOutputKind::DynamicPicExe
1506 (CrateType::Executable, false, _) => LinkOutputKind::DynamicNoPicExe,
1507 (CrateType::Executable, true, RelocModel::Pic | RelocModel::Pie) => {
1508 LinkOutputKind::StaticPicExe
1510 (CrateType::Executable, true, _) => LinkOutputKind::StaticNoPicExe,
1511 (_, true, _) => LinkOutputKind::StaticDylib,
1512 (_, false, _) => LinkOutputKind::DynamicDylib,
1515 // Adjust the output kind to target capabilities.
1516 let opts = &sess.target;
1517 let pic_exe_supported = opts.position_independent_executables;
1518 let static_pic_exe_supported = opts.static_position_independent_executables;
1519 let static_dylib_supported = opts.crt_static_allows_dylibs;
1521 LinkOutputKind::DynamicPicExe if !pic_exe_supported => LinkOutputKind::DynamicNoPicExe,
1522 LinkOutputKind::StaticPicExe if !static_pic_exe_supported => LinkOutputKind::StaticNoPicExe,
1523 LinkOutputKind::StaticDylib if !static_dylib_supported => LinkOutputKind::DynamicDylib,
1528 // Returns true if linker is located within sysroot
1529 fn detect_self_contained_mingw(sess: &Session) -> bool {
1530 let (linker, _) = linker_and_flavor(&sess);
1531 // Assume `-C linker=rust-lld` as self-contained mode
1532 if linker == Path::new("rust-lld") {
1535 let linker_with_extension = if cfg!(windows) && linker.extension().is_none() {
1536 linker.with_extension("exe")
1540 for dir in env::split_paths(&env::var_os("PATH").unwrap_or_default()) {
1541 let full_path = dir.join(&linker_with_extension);
1542 // If linker comes from sysroot assume self-contained mode
1543 if full_path.is_file() && !full_path.starts_with(&sess.sysroot) {
1550 /// Various toolchain components used during linking are used from rustc distribution
1551 /// instead of being found somewhere on the host system.
1552 /// We only provide such support for a very limited number of targets.
1553 fn self_contained(sess: &Session, crate_type: CrateType) -> bool {
1554 if let Some(self_contained) = sess.opts.cg.link_self_contained {
1555 return self_contained;
1558 match sess.target.link_self_contained {
1559 LinkSelfContainedDefault::False => false,
1560 LinkSelfContainedDefault::True => true,
1561 // FIXME: Find a better heuristic for "native musl toolchain is available",
1562 // based on host and linker path, for example.
1563 // (https://github.com/rust-lang/rust/pull/71769#issuecomment-626330237).
1564 LinkSelfContainedDefault::Musl => sess.crt_static(Some(crate_type)),
1565 LinkSelfContainedDefault::Mingw => {
1566 sess.host == sess.target
1567 && sess.target.vendor != "uwp"
1568 && detect_self_contained_mingw(&sess)
1573 /// Add pre-link object files defined by the target spec.
1574 fn add_pre_link_objects(
1575 cmd: &mut dyn Linker,
1577 flavor: LinkerFlavor,
1578 link_output_kind: LinkOutputKind,
1579 self_contained: bool,
1581 // FIXME: we are currently missing some infra here (per-linker-flavor CRT objects),
1582 // so Fuchsia has to be special-cased.
1583 let opts = &sess.target;
1584 let empty = Default::default();
1585 let objects = if self_contained {
1586 &opts.pre_link_objects_self_contained
1587 } else if !(sess.target.os == "fuchsia" && flavor == LinkerFlavor::Gcc) {
1588 &opts.pre_link_objects
1592 for obj in objects.get(&link_output_kind).iter().copied().flatten() {
1593 cmd.add_object(&get_object_file_path(sess, obj, self_contained));
1597 /// Add post-link object files defined by the target spec.
1598 fn add_post_link_objects(
1599 cmd: &mut dyn Linker,
1601 link_output_kind: LinkOutputKind,
1602 self_contained: bool,
1604 let objects = if self_contained {
1605 &sess.target.post_link_objects_self_contained
1607 &sess.target.post_link_objects
1609 for obj in objects.get(&link_output_kind).iter().copied().flatten() {
1610 cmd.add_object(&get_object_file_path(sess, obj, self_contained));
1614 /// Add arbitrary "pre-link" args defined by the target spec or from command line.
1615 /// FIXME: Determine where exactly these args need to be inserted.
1616 fn add_pre_link_args(cmd: &mut dyn Linker, sess: &Session, flavor: LinkerFlavor) {
1617 if let Some(args) = sess.target.pre_link_args.get(&flavor) {
1618 cmd.args(args.iter().map(Deref::deref));
1620 cmd.args(&sess.opts.unstable_opts.pre_link_args);
1623 /// Add a link script embedded in the target, if applicable.
1624 fn add_link_script(cmd: &mut dyn Linker, sess: &Session, tmpdir: &Path, crate_type: CrateType) {
1625 match (crate_type, &sess.target.link_script) {
1626 (CrateType::Cdylib | CrateType::Executable, Some(script)) => {
1627 if !sess.target.linker_is_gnu {
1628 sess.fatal("can only use link script when linking with GNU-like linker");
1631 let file_name = ["rustc", &sess.target.llvm_target, "linkfile.ld"].join("-");
1633 let path = tmpdir.join(file_name);
1634 if let Err(e) = fs::write(&path, script.as_ref()) {
1635 sess.fatal(&format!("failed to write link script to {}: {}", path.display(), e));
1638 cmd.arg("--script");
1645 /// Add arbitrary "user defined" args defined from command line.
1646 /// FIXME: Determine where exactly these args need to be inserted.
1647 fn add_user_defined_link_args(cmd: &mut dyn Linker, sess: &Session) {
1648 cmd.args(&sess.opts.cg.link_args);
1651 /// Add arbitrary "late link" args defined by the target spec.
1652 /// FIXME: Determine where exactly these args need to be inserted.
1653 fn add_late_link_args(
1654 cmd: &mut dyn Linker,
1656 flavor: LinkerFlavor,
1657 crate_type: CrateType,
1658 codegen_results: &CodegenResults,
1660 let any_dynamic_crate = crate_type == CrateType::Dylib
1661 || codegen_results.crate_info.dependency_formats.iter().any(|(ty, list)| {
1662 *ty == crate_type && list.iter().any(|&linkage| linkage == Linkage::Dynamic)
1664 if any_dynamic_crate {
1665 if let Some(args) = sess.target.late_link_args_dynamic.get(&flavor) {
1666 cmd.args(args.iter().map(Deref::deref));
1669 if let Some(args) = sess.target.late_link_args_static.get(&flavor) {
1670 cmd.args(args.iter().map(Deref::deref));
1673 if let Some(args) = sess.target.late_link_args.get(&flavor) {
1674 cmd.args(args.iter().map(Deref::deref));
1678 /// Add arbitrary "post-link" args defined by the target spec.
1679 /// FIXME: Determine where exactly these args need to be inserted.
1680 fn add_post_link_args(cmd: &mut dyn Linker, sess: &Session, flavor: LinkerFlavor) {
1681 if let Some(args) = sess.target.post_link_args.get(&flavor) {
1682 cmd.args(args.iter().map(Deref::deref));
1686 /// Add a synthetic object file that contains reference to all symbols that we want to expose to
1689 /// Background: we implement rlibs as static library (archives). Linkers treat archives
1690 /// differently from object files: all object files participate in linking, while archives will
1691 /// only participate in linking if they can satisfy at least one undefined reference (version
1692 /// scripts doesn't count). This causes `#[no_mangle]` or `#[used]` items to be ignored by the
1693 /// linker, and since they never participate in the linking, using `KEEP` in the linker scripts
1694 /// can't keep them either. This causes #47384.
1696 /// To keep them around, we could use `--whole-archive` and equivalents to force rlib to
1697 /// participate in linking like object files, but this proves to be expensive (#93791). Therefore
1698 /// we instead just introduce an undefined reference to them. This could be done by `-u` command
1699 /// line option to the linker or `EXTERN(...)` in linker scripts, however they does not only
1700 /// introduce an undefined reference, but also make them the GC roots, preventing `--gc-sections`
1701 /// from removing them, and this is especially problematic for embedded programming where every
1704 /// This method creates a synthetic object file, which contains undefined references to all symbols
1705 /// that are necessary for the linking. They are only present in symbol table but not actually
1706 /// used in any sections, so the linker will therefore pick relevant rlibs for linking, but
1707 /// unused `#[no_mangle]` or `#[used]` can still be discard by GC sections.
1708 fn add_linked_symbol_object(
1709 cmd: &mut dyn Linker,
1712 symbols: &[(String, SymbolExportKind)],
1714 if symbols.is_empty() {
1718 let Some(mut file) = super::metadata::create_object_file(sess) else {
1722 // NOTE(nbdd0121): MSVC will hang if the input object file contains no sections,
1723 // so add an empty section.
1724 if file.format() == object::BinaryFormat::Coff {
1725 file.add_section(Vec::new(), ".text".into(), object::SectionKind::Text);
1727 // We handle the name decoration of COFF targets in `symbol_export.rs`, so disable the
1728 // default mangler in `object` crate.
1729 file.set_mangling(object::write::Mangling::None);
1731 // Add feature flags to the object file. On MSVC this is optional but LLD will complain if
1733 let mut feature = 0;
1735 if file.architecture() == object::Architecture::I386 {
1736 // Indicate that all SEH handlers are registered in .sxdata section.
1737 // We don't have generate any code, so we don't need .sxdata section but LLD still
1738 // expects us to set this bit (see #96498).
1739 // Reference: https://docs.microsoft.com/en-us/windows/win32/debug/pe-format
1743 file.add_symbol(object::write::Symbol {
1744 name: "@feat.00".into(),
1747 kind: object::SymbolKind::Data,
1748 scope: object::SymbolScope::Compilation,
1750 section: object::write::SymbolSection::Absolute,
1751 flags: object::SymbolFlags::None,
1755 for (sym, kind) in symbols.iter() {
1756 file.add_symbol(object::write::Symbol {
1757 name: sym.clone().into(),
1761 SymbolExportKind::Text => object::SymbolKind::Text,
1762 SymbolExportKind::Data => object::SymbolKind::Data,
1763 SymbolExportKind::Tls => object::SymbolKind::Tls,
1765 scope: object::SymbolScope::Unknown,
1767 section: object::write::SymbolSection::Undefined,
1768 flags: object::SymbolFlags::None,
1772 let path = tmpdir.join("symbols.o");
1773 let result = std::fs::write(&path, file.write().unwrap());
1774 if let Err(e) = result {
1775 sess.fatal(&format!("failed to write {}: {}", path.display(), e));
1777 cmd.add_object(&path);
1780 /// Add object files containing code from the current crate.
1781 fn add_local_crate_regular_objects(cmd: &mut dyn Linker, codegen_results: &CodegenResults) {
1782 for obj in codegen_results.modules.iter().filter_map(|m| m.object.as_ref()) {
1783 cmd.add_object(obj);
1787 /// Add object files for allocator code linked once for the whole crate tree.
1788 fn add_local_crate_allocator_objects(cmd: &mut dyn Linker, codegen_results: &CodegenResults) {
1789 if let Some(obj) = codegen_results.allocator_module.as_ref().and_then(|m| m.object.as_ref()) {
1790 cmd.add_object(obj);
1794 /// Add object files containing metadata for the current crate.
1795 fn add_local_crate_metadata_objects(
1796 cmd: &mut dyn Linker,
1797 crate_type: CrateType,
1798 codegen_results: &CodegenResults,
1800 // When linking a dynamic library, we put the metadata into a section of the
1801 // executable. This metadata is in a separate object file from the main
1802 // object file, so we link that in here.
1803 if crate_type == CrateType::Dylib || crate_type == CrateType::ProcMacro {
1804 if let Some(obj) = codegen_results.metadata_module.as_ref().and_then(|m| m.object.as_ref())
1806 cmd.add_object(obj);
1811 /// Add sysroot and other globally set directories to the directory search list.
1812 fn add_library_search_dirs(cmd: &mut dyn Linker, sess: &Session, self_contained: bool) {
1813 // The default library location, we need this to find the runtime.
1814 // The location of crates will be determined as needed.
1815 let lib_path = sess.target_filesearch(PathKind::All).get_lib_path();
1816 cmd.include_path(&fix_windows_verbatim_for_gcc(&lib_path));
1818 // Special directory with libraries used only in self-contained linkage mode
1820 let lib_path = sess.target_filesearch(PathKind::All).get_self_contained_lib_path();
1821 cmd.include_path(&fix_windows_verbatim_for_gcc(&lib_path));
1825 /// Add options making relocation sections in the produced ELF files read-only
1826 /// and suppressing lazy binding.
1827 fn add_relro_args(cmd: &mut dyn Linker, sess: &Session) {
1828 match sess.opts.unstable_opts.relro_level.unwrap_or(sess.target.relro_level) {
1829 RelroLevel::Full => cmd.full_relro(),
1830 RelroLevel::Partial => cmd.partial_relro(),
1831 RelroLevel::Off => cmd.no_relro(),
1832 RelroLevel::None => {}
1836 /// Add library search paths used at runtime by dynamic linkers.
1838 cmd: &mut dyn Linker,
1840 codegen_results: &CodegenResults,
1841 out_filename: &Path,
1843 // FIXME (#2397): At some point we want to rpath our guesses as to
1844 // where extern libraries might live, based on the
1845 // add_lib_search_paths
1846 if sess.opts.cg.rpath {
1847 let libs = codegen_results
1851 .filter_map(|cnum| {
1852 codegen_results.crate_info.used_crate_source[cnum]
1855 .map(|(path, _)| &**path)
1857 .collect::<Vec<_>>();
1858 let mut rpath_config = RPathConfig {
1860 out_filename: out_filename.to_path_buf(),
1861 has_rpath: sess.target.has_rpath,
1862 is_like_osx: sess.target.is_like_osx,
1863 linker_is_gnu: sess.target.linker_is_gnu,
1865 cmd.args(&rpath::get_rpath_flags(&mut rpath_config));
1869 /// Produce the linker command line containing linker path and arguments.
1871 /// When comments in the function say "order-(in)dependent" they mean order-dependence between
1872 /// options and libraries/object files. For example `--whole-archive` (order-dependent) applies
1873 /// to specific libraries passed after it, and `-o` (output file, order-independent) applies
1874 /// to the linking process as a whole.
1875 /// Order-independent options may still override each other in order-dependent fashion,
1876 /// e.g `--foo=yes --foo=no` may be equivalent to `--foo=no`.
1877 fn linker_with_args<'a>(
1879 flavor: LinkerFlavor,
1881 archive_builder_builder: &dyn ArchiveBuilderBuilder,
1882 crate_type: CrateType,
1884 out_filename: &Path,
1885 codegen_results: &CodegenResults,
1886 ) -> Result<Command, ErrorGuaranteed> {
1887 let self_contained = self_contained(sess, crate_type);
1888 let cmd = &mut *super::linker::get_linker(
1893 &codegen_results.crate_info.target_cpu,
1895 let link_output_kind = link_output_kind(sess, crate_type);
1897 // ------------ Early order-dependent options ------------
1899 // If we're building something like a dynamic library then some platforms
1900 // need to make sure that all symbols are exported correctly from the
1902 // Must be passed before any libraries to prevent the symbols to export from being thrown away,
1903 // at least on some platforms (e.g. windows-gnu).
1907 &codegen_results.crate_info.exported_symbols[&crate_type],
1910 // Can be used for adding custom CRT objects or overriding order-dependent options above.
1911 // FIXME: In practice built-in target specs use this for arbitrary order-independent options,
1912 // introduce a target spec option for order-independent linker options and migrate built-in
1914 add_pre_link_args(cmd, sess, flavor);
1916 // ------------ Object code and libraries, order-dependent ------------
1918 // Pre-link CRT objects.
1919 add_pre_link_objects(cmd, sess, flavor, link_output_kind, self_contained);
1921 add_linked_symbol_object(
1925 &codegen_results.crate_info.linked_symbols[&crate_type],
1928 // Sanitizer libraries.
1929 add_sanitizer_libraries(sess, crate_type, cmd);
1931 // Object code from the current crate.
1932 // Take careful note of the ordering of the arguments we pass to the linker
1933 // here. Linkers will assume that things on the left depend on things to the
1934 // right. Things on the right cannot depend on things on the left. This is
1935 // all formally implemented in terms of resolving symbols (libs on the right
1936 // resolve unknown symbols of libs on the left, but not vice versa).
1938 // For this reason, we have organized the arguments we pass to the linker as
1941 // 1. The local object that LLVM just generated
1942 // 2. Local native libraries
1943 // 3. Upstream rust libraries
1944 // 4. Upstream native libraries
1946 // The rationale behind this ordering is that those items lower down in the
1947 // list can't depend on items higher up in the list. For example nothing can
1948 // depend on what we just generated (e.g., that'd be a circular dependency).
1949 // Upstream rust libraries are not supposed to depend on our local native
1950 // libraries as that would violate the structure of the DAG, in that
1951 // scenario they are required to link to them as well in a shared fashion.
1952 // (The current implementation still doesn't prevent it though, see the FIXME below.)
1954 // Note that upstream rust libraries may contain native dependencies as
1955 // well, but they also can't depend on what we just started to add to the
1956 // link line. And finally upstream native libraries can't depend on anything
1957 // in this DAG so far because they can only depend on other native libraries
1958 // and such dependencies are also required to be specified.
1959 add_local_crate_regular_objects(cmd, codegen_results);
1960 add_local_crate_metadata_objects(cmd, crate_type, codegen_results);
1961 add_local_crate_allocator_objects(cmd, codegen_results);
1963 // Avoid linking to dynamic libraries unless they satisfy some undefined symbols
1964 // at the point at which they are specified on the command line.
1965 // Must be passed before any (dynamic) libraries to have effect on them.
1966 // On Solaris-like systems, `-z ignore` acts as both `--as-needed` and `--gc-sections`
1967 // so it will ignore unreferenced ELF sections from relocatable objects.
1968 // For that reason, we put this flag after metadata objects as they would otherwise be removed.
1969 // FIXME: Support more fine-grained dead code removal on Solaris/illumos
1970 // and move this option back to the top.
1971 cmd.add_as_needed();
1973 // FIXME: Move this below to other native libraries
1974 // (or alternatively link all native libraries after their respective crates).
1975 // This change is somewhat breaking in practice due to local static libraries being linked
1976 // as whole-archive (#85144), so removing whole-archive may be a pre-requisite.
1977 if sess.opts.unstable_opts.link_native_libraries {
1978 add_local_native_libraries(cmd, sess, codegen_results);
1981 // Upstream rust libraries and their non-bundled static libraries
1982 add_upstream_rust_crates(
1985 archive_builder_builder,
1991 // Upstream dynamic native libraries linked with `#[link]` attributes at and `-l`
1992 // command line options.
1993 // If -Zlink-native-libraries=false is set, then the assumption is that an
1994 // external build system already has the native dependencies defined, and it
1995 // will provide them to the linker itself.
1996 if sess.opts.unstable_opts.link_native_libraries {
1997 add_upstream_native_libraries(cmd, sess, codegen_results);
2000 // Link with the import library generated for any raw-dylib functions.
2001 for (raw_dylib_name, raw_dylib_imports) in
2002 collate_raw_dylibs(sess, &codegen_results.crate_info.used_libraries)?
2004 cmd.add_object(&archive_builder_builder.create_dll_import_lib(
2012 // Library linking above uses some global state for things like `-Bstatic`/`-Bdynamic` to make
2013 // command line shorter, reset it to default here before adding more libraries.
2014 cmd.reset_per_library_state();
2016 // FIXME: Built-in target specs occasionally use this for linking system libraries,
2017 // eliminate all such uses by migrating them to `#[link]` attributes in `lib(std,c,unwind)`
2018 // and remove the option.
2019 add_late_link_args(cmd, sess, flavor, crate_type, codegen_results);
2021 // ------------ Arbitrary order-independent options ------------
2023 // Add order-independent options determined by rustc from its compiler options,
2024 // target properties and source code.
2025 add_order_independent_options(
2037 // Can be used for arbitrary order-independent options.
2038 // In practice may also be occasionally used for linking native libraries.
2039 // Passed after compiler-generated options to support manual overriding when necessary.
2040 add_user_defined_link_args(cmd, sess);
2042 // ------------ Object code and libraries, order-dependent ------------
2044 // Post-link CRT objects.
2045 add_post_link_objects(cmd, sess, link_output_kind, self_contained);
2047 // ------------ Late order-dependent options ------------
2049 // Doesn't really make sense.
2050 // FIXME: In practice built-in target specs use this for arbitrary order-independent options,
2051 // introduce a target spec option for order-independent linker options, migrate built-in specs
2052 // to it and remove the option.
2053 add_post_link_args(cmd, sess, flavor);
2058 fn add_order_independent_options(
2059 cmd: &mut dyn Linker,
2061 link_output_kind: LinkOutputKind,
2062 self_contained: bool,
2063 flavor: LinkerFlavor,
2064 crate_type: CrateType,
2065 codegen_results: &CodegenResults,
2066 out_filename: &Path,
2069 add_gcc_ld_path(cmd, sess, flavor);
2071 add_apple_sdk(cmd, sess, flavor);
2073 add_link_script(cmd, sess, tmpdir, crate_type);
2075 if sess.target.os == "fuchsia"
2076 && crate_type == CrateType::Executable
2077 && flavor != LinkerFlavor::Gcc
2079 let prefix = if sess.opts.unstable_opts.sanitizer.contains(SanitizerSet::ADDRESS) {
2084 cmd.arg(format!("--dynamic-linker={}ld.so.1", prefix));
2087 if sess.target.eh_frame_header {
2088 cmd.add_eh_frame_header();
2091 // Make the binary compatible with data execution prevention schemes.
2095 cmd.no_crt_objects();
2098 if sess.target.os == "emscripten" {
2100 cmd.arg(if sess.panic_strategy() == PanicStrategy::Abort {
2101 "DISABLE_EXCEPTION_CATCHING=1"
2103 "DISABLE_EXCEPTION_CATCHING=0"
2107 if flavor == LinkerFlavor::PtxLinker {
2108 // Provide the linker with fallback to internal `target-cpu`.
2109 cmd.arg("--fallback-arch");
2110 cmd.arg(&codegen_results.crate_info.target_cpu);
2111 } else if flavor == LinkerFlavor::BpfLinker {
2113 cmd.arg(&codegen_results.crate_info.target_cpu);
2114 cmd.arg("--cpu-features");
2115 cmd.arg(match &sess.opts.cg.target_feature {
2116 feat if !feat.is_empty() => feat.as_ref(),
2117 _ => sess.target.options.features.as_ref(),
2121 cmd.linker_plugin_lto();
2123 add_library_search_dirs(cmd, sess, self_contained);
2125 cmd.output_filename(out_filename);
2127 if crate_type == CrateType::Executable && sess.target.is_like_windows {
2128 if let Some(ref s) = codegen_results.crate_info.windows_subsystem {
2133 // Try to strip as much out of the generated object by removing unused
2134 // sections if possible. See more comments in linker.rs
2135 if !sess.link_dead_code() {
2136 // If PGO is enabled sometimes gc_sections will remove the profile data section
2137 // as it appears to be unused. This can then cause the PGO profile file to lose
2138 // some functions. If we are generating a profile we shouldn't strip those metadata
2139 // sections to ensure we have all the data for PGO.
2141 crate_type == CrateType::Dylib || sess.opts.cg.profile_generate.enabled();
2142 if crate_type != CrateType::Executable || !sess.opts.unstable_opts.export_executable_symbols
2144 cmd.gc_sections(keep_metadata);
2146 cmd.no_gc_sections();
2150 cmd.set_output_kind(link_output_kind, out_filename);
2152 add_relro_args(cmd, sess);
2154 // Pass optimization flags down to the linker.
2157 // Gather the set of NatVis files, if any, and write them out to a temp directory.
2158 let natvis_visualizers = collect_natvis_visualizers(
2161 &codegen_results.crate_info.local_crate_name,
2162 &codegen_results.crate_info.natvis_debugger_visualizers,
2165 // Pass debuginfo, NatVis debugger visualizers and strip flags down to the linker.
2166 cmd.debuginfo(strip_value(sess), &natvis_visualizers);
2168 // We want to prevent the compiler from accidentally leaking in any system libraries,
2169 // so by default we tell linkers not to link to any default libraries.
2170 if !sess.opts.cg.default_linker_libraries && sess.target.no_default_libraries {
2171 cmd.no_default_libraries();
2174 if sess.opts.cg.profile_generate.enabled() || sess.instrument_coverage() {
2178 if sess.opts.cg.control_flow_guard != CFGuard::Disabled {
2179 cmd.control_flow_guard();
2182 add_rpath_args(cmd, sess, codegen_results, out_filename);
2185 // Write the NatVis debugger visualizer files for each crate to the temp directory and gather the file paths.
2186 fn collect_natvis_visualizers(
2189 crate_name: &Symbol,
2190 natvis_debugger_visualizers: &BTreeSet<DebuggerVisualizerFile>,
2192 let mut visualizer_paths = Vec::with_capacity(natvis_debugger_visualizers.len());
2194 for (index, visualizer) in natvis_debugger_visualizers.iter().enumerate() {
2195 let visualizer_out_file = tmpdir.join(format!("{}-{}.natvis", crate_name.as_str(), index));
2197 match fs::write(&visualizer_out_file, &visualizer.src) {
2199 visualizer_paths.push(visualizer_out_file);
2204 "Unable to write debugger visualizer file `{}`: {} ",
2205 visualizer_out_file.display(),
2216 /// # Native library linking
2218 /// User-supplied library search paths (-L on the command line). These are the same paths used to
2219 /// find Rust crates, so some of them may have been added already by the previous crate linking
2220 /// code. This only allows them to be found at compile time so it is still entirely up to outside
2221 /// forces to make sure that library can be found at runtime.
2223 /// Also note that the native libraries linked here are only the ones located in the current crate.
2224 /// Upstream crates with native library dependencies may have their native library pulled in above.
2225 fn add_local_native_libraries(
2226 cmd: &mut dyn Linker,
2228 codegen_results: &CodegenResults,
2230 let filesearch = sess.target_filesearch(PathKind::All);
2231 for search_path in filesearch.search_paths() {
2232 match search_path.kind {
2233 PathKind::Framework => {
2234 cmd.framework_path(&search_path.dir);
2237 cmd.include_path(&fix_windows_verbatim_for_gcc(&search_path.dir));
2243 codegen_results.crate_info.used_libraries.iter().filter(|l| relevant_lib(sess, l));
2245 let search_path = OnceCell::new();
2246 let mut last = (None, NativeLibKind::Unspecified, None);
2247 for lib in relevant_libs {
2248 let Some(name) = lib.name else {
2251 let name = name.as_str();
2253 // Skip if this library is the same as the last.
2254 last = if (lib.name, lib.kind, lib.verbatim) == last {
2257 (lib.name, lib.kind, lib.verbatim)
2260 let verbatim = lib.verbatim.unwrap_or(false);
2262 NativeLibKind::Dylib { as_needed } => {
2263 cmd.link_dylib(name, verbatim, as_needed.unwrap_or(true))
2265 NativeLibKind::Unspecified => cmd.link_dylib(name, verbatim, true),
2266 NativeLibKind::Framework { as_needed } => {
2267 cmd.link_framework(name, as_needed.unwrap_or(true))
2269 NativeLibKind::Static { whole_archive, bundle, .. } => {
2270 if whole_archive == Some(true)
2271 // Backward compatibility case: this can be a rlib (so `+whole-archive` cannot
2272 // be added explicitly if necessary, see the error in `fn link_rlib`) compiled
2273 // as an executable due to `--test`. Use whole-archive implicitly, like before
2274 // the introduction of native lib modifiers.
2275 || (whole_archive == None && bundle != Some(false) && sess.opts.test)
2277 cmd.link_whole_staticlib(
2280 &search_path.get_or_init(|| archive_search_paths(sess)),
2283 cmd.link_staticlib(name, verbatim)
2286 NativeLibKind::RawDylib => {
2287 // Ignore RawDylib here, they are handled separately in linker_with_args().
2289 NativeLibKind::LinkArg => {
2296 /// # Linking Rust crates and their non-bundled static libraries
2298 /// Rust crates are not considered at all when creating an rlib output. All dependencies will be
2299 /// linked when producing the final output (instead of the intermediate rlib version).
2300 fn add_upstream_rust_crates<'a>(
2301 cmd: &mut dyn Linker,
2303 archive_builder_builder: &dyn ArchiveBuilderBuilder,
2304 codegen_results: &CodegenResults,
2305 crate_type: CrateType,
2308 // All of the heavy lifting has previously been accomplished by the
2309 // dependency_format module of the compiler. This is just crawling the
2310 // output of that module, adding crates as necessary.
2312 // Linking to a rlib involves just passing it to the linker (the linker
2313 // will slurp up the object files inside), and linking to a dynamic library
2314 // involves just passing the right -l flag.
2316 let (_, data) = codegen_results
2320 .find(|(ty, _)| *ty == crate_type)
2321 .expect("failed to find crate type in dependency format list");
2323 // Invoke get_used_crates to ensure that we get a topological sorting of
2325 let deps = &codegen_results.crate_info.used_crates;
2327 // There's a few internal crates in the standard library (aka libcore and
2328 // libstd) which actually have a circular dependence upon one another. This
2329 // currently arises through "weak lang items" where libcore requires things
2330 // like `rust_begin_unwind` but libstd ends up defining it. To get this
2331 // circular dependence to work correctly in all situations we'll need to be
2332 // sure to correctly apply the `--start-group` and `--end-group` options to
2333 // GNU linkers, otherwise if we don't use any other symbol from the standard
2334 // library it'll get discarded and the whole application won't link.
2336 // In this loop we're calculating the `group_end`, after which crate to
2337 // pass `--end-group` and `group_start`, before which crate to pass
2338 // `--start-group`. We currently do this by passing `--end-group` after
2339 // the first crate (when iterating backwards) that requires a lang item
2340 // defined somewhere else. Once that's set then when we've defined all the
2341 // necessary lang items we'll pass `--start-group`.
2343 // Note that this isn't amazing logic for now but it should do the trick
2344 // for the current implementation of the standard library.
2345 let mut group_end = None;
2346 let mut group_start = None;
2347 // Crates available for linking thus far.
2348 let mut available = FxHashSet::default();
2349 // Crates required to satisfy dependencies discovered so far.
2350 let mut required = FxHashSet::default();
2352 let info = &codegen_results.crate_info;
2353 for &cnum in deps.iter().rev() {
2354 if let Some(missing) = info.missing_lang_items.get(&cnum) {
2355 let missing_crates = missing.iter().map(|i| info.lang_item_to_crate.get(i).copied());
2356 required.extend(missing_crates);
2359 required.insert(Some(cnum));
2360 available.insert(Some(cnum));
2362 if required.len() > available.len() && group_end.is_none() {
2363 group_end = Some(cnum);
2365 if required.len() == available.len() && group_end.is_some() {
2366 group_start = Some(cnum);
2371 // If we didn't end up filling in all lang items from upstream crates then
2372 // we'll be filling it in with our crate. This probably means we're the
2373 // standard library itself, so skip this for now.
2374 if group_end.is_some() && group_start.is_none() {
2378 let mut compiler_builtins = None;
2379 let search_path = OnceCell::new();
2381 for &cnum in deps.iter() {
2382 if group_start == Some(cnum) {
2386 // We may not pass all crates through to the linker. Some crates may
2387 // appear statically in an existing dylib, meaning we'll pick up all the
2388 // symbols from the dylib.
2389 let src = &codegen_results.crate_info.used_crate_source[&cnum];
2390 match data[cnum.as_usize() - 1] {
2391 _ if codegen_results.crate_info.profiler_runtime == Some(cnum) => {
2392 add_static_crate(cmd, sess, archive_builder_builder, codegen_results, tmpdir, cnum);
2394 // compiler-builtins are always placed last to ensure that they're
2395 // linked correctly.
2396 _ if codegen_results.crate_info.compiler_builtins == Some(cnum) => {
2397 assert!(compiler_builtins.is_none());
2398 compiler_builtins = Some(cnum);
2400 Linkage::NotLinked | Linkage::IncludedFromDylib => {}
2401 Linkage::Static => {
2402 add_static_crate(cmd, sess, archive_builder_builder, codegen_results, tmpdir, cnum);
2404 // Link static native libs with "-bundle" modifier only if the crate they originate from
2405 // is being linked statically to the current crate. If it's linked dynamically
2406 // or is an rlib already included via some other dylib crate, the symbols from
2407 // native libs will have already been included in that dylib.
2409 // If -Zlink-native-libraries=false is set, then the assumption is that an
2410 // external build system already has the native dependencies defined, and it
2411 // will provide them to the linker itself.
2412 if sess.opts.unstable_opts.link_native_libraries {
2413 let mut last = (None, NativeLibKind::Unspecified, None);
2414 for lib in &codegen_results.crate_info.native_libraries[&cnum] {
2415 let Some(name) = lib.name else {
2418 let name = name.as_str();
2419 if !relevant_lib(sess, lib) {
2423 // Skip if this library is the same as the last.
2424 last = if (lib.name, lib.kind, lib.verbatim) == last {
2427 (lib.name, lib.kind, lib.verbatim)
2431 NativeLibKind::Static {
2432 bundle: Some(false),
2433 whole_archive: Some(true),
2435 cmd.link_whole_staticlib(
2437 lib.verbatim.unwrap_or(false),
2438 search_path.get_or_init(|| archive_search_paths(sess)),
2441 NativeLibKind::Static {
2442 bundle: Some(false),
2443 whole_archive: Some(false) | None,
2445 cmd.link_staticlib(name, lib.verbatim.unwrap_or(false));
2447 NativeLibKind::LinkArg => {
2450 NativeLibKind::Dylib { .. }
2451 | NativeLibKind::Framework { .. }
2452 | NativeLibKind::Unspecified
2453 | NativeLibKind::RawDylib => {}
2454 NativeLibKind::Static {
2455 bundle: Some(true) | None,
2462 Linkage::Dynamic => add_dynamic_crate(cmd, sess, &src.dylib.as_ref().unwrap().0),
2465 if group_end == Some(cnum) {
2470 // compiler-builtins are always placed last to ensure that they're
2471 // linked correctly.
2472 // We must always link the `compiler_builtins` crate statically. Even if it
2473 // was already "included" in a dylib (e.g., `libstd` when `-C prefer-dynamic`
2475 if let Some(cnum) = compiler_builtins {
2476 add_static_crate(cmd, sess, archive_builder_builder, codegen_results, tmpdir, cnum);
2479 // Converts a library file-stem into a cc -l argument
2480 fn unlib<'a>(target: &Target, stem: &'a str) -> &'a str {
2481 if stem.starts_with("lib") && !target.is_like_windows { &stem[3..] } else { stem }
2484 // Adds the static "rlib" versions of all crates to the command line.
2485 // There's a bit of magic which happens here specifically related to LTO,
2486 // namely that we remove upstream object files.
2488 // When performing LTO, almost(*) all of the bytecode from the upstream
2489 // libraries has already been included in our object file output. As a
2490 // result we need to remove the object files in the upstream libraries so
2491 // the linker doesn't try to include them twice (or whine about duplicate
2492 // symbols). We must continue to include the rest of the rlib, however, as
2493 // it may contain static native libraries which must be linked in.
2495 // (*) Crates marked with `#![no_builtins]` don't participate in LTO and
2496 // their bytecode wasn't included. The object files in those libraries must
2497 // still be passed to the linker.
2499 // Note, however, that if we're not doing LTO we can just pass the rlib
2500 // blindly to the linker (fast) because it's fine if it's not actually
2501 // included as we're at the end of the dependency chain.
2502 fn add_static_crate<'a>(
2503 cmd: &mut dyn Linker,
2505 archive_builder_builder: &dyn ArchiveBuilderBuilder,
2506 codegen_results: &CodegenResults,
2510 let src = &codegen_results.crate_info.used_crate_source[&cnum];
2511 let cratepath = &src.rlib.as_ref().unwrap().0;
2513 let mut link_upstream = |path: &Path| {
2514 cmd.link_rlib(&fix_windows_verbatim_for_gcc(path));
2517 // See the comment above in `link_staticlib` and `link_rlib` for why if
2518 // there's a static library that's not relevant we skip all object
2520 let native_libs = &codegen_results.crate_info.native_libraries[&cnum];
2521 let skip_native = native_libs.iter().any(|lib| {
2522 matches!(lib.kind, NativeLibKind::Static { bundle: None | Some(true), .. })
2523 && !relevant_lib(sess, lib)
2526 if (!are_upstream_rust_objects_already_included(sess)
2527 || ignored_for_lto(sess, &codegen_results.crate_info, cnum))
2530 link_upstream(cratepath);
2534 let dst = tmpdir.join(cratepath.file_name().unwrap());
2535 let name = cratepath.file_name().unwrap().to_str().unwrap();
2536 let name = &name[3..name.len() - 5]; // chop off lib/.rlib
2538 sess.prof.generic_activity_with_arg("link_altering_rlib", name).run(|| {
2539 let canonical_name = name.replace('-', "_");
2540 let upstream_rust_objects_already_included =
2541 are_upstream_rust_objects_already_included(sess);
2542 let is_builtins = sess.target.no_builtins
2543 || !codegen_results.crate_info.is_no_builtins.contains(&cnum);
2545 let mut archive = archive_builder_builder.new_archive_builder(sess);
2546 if let Err(e) = archive.add_archive(
2549 if f == METADATA_FILENAME {
2553 let canonical = f.replace('-', "_");
2555 let is_rust_object =
2556 canonical.starts_with(&canonical_name) && looks_like_rust_object_file(&f);
2558 // If we've been requested to skip all native object files
2559 // (those not generated by the rust compiler) then we can skip
2560 // this file. See above for why we may want to do this.
2561 let skip_because_cfg_say_so = skip_native && !is_rust_object;
2563 // If we're performing LTO and this is a rust-generated object
2564 // file, then we don't need the object file as it's part of the
2565 // LTO module. Note that `#![no_builtins]` is excluded from LTO,
2566 // though, so we let that object file slide.
2567 let skip_because_lto =
2568 upstream_rust_objects_already_included && is_rust_object && is_builtins;
2570 if skip_because_cfg_say_so || skip_because_lto {
2577 sess.fatal(&format!("failed to build archive from rlib: {}", e));
2579 if archive.build(&dst) {
2580 link_upstream(&dst);
2585 // Same thing as above, but for dynamic crates instead of static crates.
2586 fn add_dynamic_crate(cmd: &mut dyn Linker, sess: &Session, cratepath: &Path) {
2587 // Just need to tell the linker about where the library lives and
2589 let parent = cratepath.parent();
2590 if let Some(dir) = parent {
2591 cmd.include_path(&fix_windows_verbatim_for_gcc(dir));
2593 let filestem = cratepath.file_stem().unwrap().to_str().unwrap();
2594 cmd.link_rust_dylib(
2595 &unlib(&sess.target, filestem),
2596 parent.unwrap_or_else(|| Path::new("")),
2601 /// Link in all of our upstream crates' native dependencies. Remember that all of these upstream
2602 /// native dependencies are all non-static dependencies. We've got two cases then:
2604 /// 1. The upstream crate is an rlib. In this case we *must* link in the native dependency because
2605 /// the rlib is just an archive.
2607 /// 2. The upstream crate is a dylib. In order to use the dylib, we have to have the dependency
2608 /// present on the system somewhere. Thus, we don't gain a whole lot from not linking in the
2609 /// dynamic dependency to this crate as well.
2611 /// The use case for this is a little subtle. In theory the native dependencies of a crate are
2612 /// purely an implementation detail of the crate itself, but the problem arises with generic and
2613 /// inlined functions. If a generic function calls a native function, then the generic function
2614 /// must be instantiated in the target crate, meaning that the native symbol must also be resolved
2615 /// in the target crate.
2616 fn add_upstream_native_libraries(
2617 cmd: &mut dyn Linker,
2619 codegen_results: &CodegenResults,
2621 let mut last = (None, NativeLibKind::Unspecified, None);
2622 for &cnum in &codegen_results.crate_info.used_crates {
2623 for lib in codegen_results.crate_info.native_libraries[&cnum].iter() {
2624 let Some(name) = lib.name else {
2627 let name = name.as_str();
2628 if !relevant_lib(sess, &lib) {
2632 // Skip if this library is the same as the last.
2633 last = if (lib.name, lib.kind, lib.verbatim) == last {
2636 (lib.name, lib.kind, lib.verbatim)
2639 let verbatim = lib.verbatim.unwrap_or(false);
2641 NativeLibKind::Dylib { as_needed } => {
2642 cmd.link_dylib(name, verbatim, as_needed.unwrap_or(true))
2644 NativeLibKind::Unspecified => cmd.link_dylib(name, verbatim, true),
2645 NativeLibKind::Framework { as_needed } => {
2646 cmd.link_framework(name, as_needed.unwrap_or(true))
2648 // ignore static native libraries here as we've
2649 // already included them in add_local_native_libraries and
2650 // add_upstream_rust_crates
2651 NativeLibKind::Static { .. } => {}
2652 NativeLibKind::RawDylib | NativeLibKind::LinkArg => {}
2658 fn relevant_lib(sess: &Session, lib: &NativeLib) -> bool {
2660 Some(ref cfg) => rustc_attr::cfg_matches(cfg, &sess.parse_sess, CRATE_NODE_ID, None),
2665 fn are_upstream_rust_objects_already_included(sess: &Session) -> bool {
2667 config::Lto::Fat => true,
2668 config::Lto::Thin => {
2669 // If we defer LTO to the linker, we haven't run LTO ourselves, so
2670 // any upstream object files have not been copied yet.
2671 !sess.opts.cg.linker_plugin_lto.enabled()
2673 config::Lto::No | config::Lto::ThinLocal => false,
2677 fn add_apple_sdk(cmd: &mut dyn Linker, sess: &Session, flavor: LinkerFlavor) {
2678 let arch = &sess.target.arch;
2679 let os = &sess.target.os;
2680 let llvm_target = &sess.target.llvm_target;
2681 if sess.target.vendor != "apple"
2682 || !matches!(os.as_ref(), "ios" | "tvos" | "watchos" | "macos")
2683 || (flavor != LinkerFlavor::Gcc && flavor != LinkerFlavor::Lld(LldFlavor::Ld64))
2688 if os == "macos" && flavor != LinkerFlavor::Lld(LldFlavor::Ld64) {
2692 let sdk_name = match (arch.as_ref(), os.as_ref()) {
2693 ("aarch64", "tvos") => "appletvos",
2694 ("x86_64", "tvos") => "appletvsimulator",
2695 ("arm", "ios") => "iphoneos",
2696 ("aarch64", "ios") if llvm_target.contains("macabi") => "macosx",
2697 ("aarch64", "ios") if llvm_target.ends_with("-simulator") => "iphonesimulator",
2698 ("aarch64", "ios") => "iphoneos",
2699 ("x86", "ios") => "iphonesimulator",
2700 ("x86_64", "ios") if llvm_target.contains("macabi") => "macosx",
2701 ("x86_64", "ios") => "iphonesimulator",
2702 ("x86_64", "watchos") => "watchsimulator",
2703 ("arm64_32", "watchos") => "watchos",
2704 ("aarch64", "watchos") if llvm_target.ends_with("-simulator") => "watchsimulator",
2705 ("aarch64", "watchos") => "watchos",
2706 ("arm", "watchos") => "watchos",
2707 (_, "macos") => "macosx",
2709 sess.err(&format!("unsupported arch `{}` for os `{}`", arch, os));
2713 let sdk_root = match get_apple_sdk_root(sdk_name) {
2722 LinkerFlavor::Gcc => {
2723 cmd.args(&["-isysroot", &sdk_root, "-Wl,-syslibroot", &sdk_root]);
2725 LinkerFlavor::Lld(LldFlavor::Ld64) => {
2726 cmd.args(&["-syslibroot", &sdk_root]);
2728 _ => unreachable!(),
2732 fn get_apple_sdk_root(sdk_name: &str) -> Result<String, String> {
2733 // Following what clang does
2734 // (https://github.com/llvm/llvm-project/blob/
2735 // 296a80102a9b72c3eda80558fb78a3ed8849b341/clang/lib/Driver/ToolChains/Darwin.cpp#L1661-L1678)
2736 // to allow the SDK path to be set. (For clang, xcrun sets
2737 // SDKROOT; for rustc, the user or build system can set it, or we
2738 // can fall back to checking for xcrun on PATH.)
2739 if let Ok(sdkroot) = env::var("SDKROOT") {
2740 let p = Path::new(&sdkroot);
2742 // Ignore `SDKROOT` if it's clearly set for the wrong platform.
2744 if sdkroot.contains("TVSimulator.platform")
2745 || sdkroot.contains("MacOSX.platform") => {}
2747 if sdkroot.contains("TVOS.platform") || sdkroot.contains("MacOSX.platform") => {}
2749 if sdkroot.contains("iPhoneSimulator.platform")
2750 || sdkroot.contains("MacOSX.platform") => {}
2752 if sdkroot.contains("iPhoneOS.platform") || sdkroot.contains("MacOSX.platform") => {
2755 if sdkroot.contains("iPhoneOS.platform")
2756 || sdkroot.contains("iPhoneSimulator.platform") => {}
2758 if sdkroot.contains("WatchSimulator.platform")
2759 || sdkroot.contains("MacOSX.platform") => {}
2761 if sdkroot.contains("WatchOS.platform") || sdkroot.contains("MacOSX.platform") => {}
2762 // Ignore `SDKROOT` if it's not a valid path.
2763 _ if !p.is_absolute() || p == Path::new("/") || !p.exists() => {}
2764 _ => return Ok(sdkroot),
2768 Command::new("xcrun").arg("--show-sdk-path").arg("-sdk").arg(sdk_name).output().and_then(
2770 if output.status.success() {
2771 Ok(String::from_utf8(output.stdout).unwrap())
2773 let error = String::from_utf8(output.stderr);
2774 let error = format!("process exit with error: {}", error.unwrap());
2775 Err(io::Error::new(io::ErrorKind::Other, &error[..]))
2781 Ok(output) => Ok(output.trim().to_string()),
2782 Err(e) => Err(format!("failed to get {} SDK path: {}", sdk_name, e)),
2786 fn add_gcc_ld_path(cmd: &mut dyn Linker, sess: &Session, flavor: LinkerFlavor) {
2787 if let Some(ld_impl) = sess.opts.unstable_opts.gcc_ld {
2788 if let LinkerFlavor::Gcc = flavor {
2791 let tools_path = sess.get_tools_search_paths(false);
2792 let gcc_ld_dir = tools_path
2794 .map(|p| p.join("gcc-ld"))
2796 p.join(if sess.host.is_like_windows { "ld.exe" } else { "ld" }).exists()
2798 .unwrap_or_else(|| sess.fatal("rust-lld (as ld) not found"));
2800 let mut arg = OsString::from("-B");
2801 arg.push(gcc_ld_dir);
2804 cmd.arg(format!("-Wl,-rustc-lld-flavor={}", sess.target.lld_flavor.as_str()));
2808 sess.fatal("option `-Z gcc-ld` is used even though linker flavor is not gcc");