1 use rustc_arena::TypedArena;
2 use rustc_ast::CRATE_NODE_ID;
3 use rustc_data_structures::fx::FxHashSet;
4 use rustc_data_structures::fx::FxIndexMap;
5 use rustc_data_structures::memmap::Mmap;
6 use rustc_data_structures::temp_dir::MaybeTempDir;
7 use rustc_errors::{ErrorGuaranteed, Handler};
8 use rustc_fs_util::fix_windows_verbatim_for_gcc;
9 use rustc_hir::def_id::{CrateNum, LOCAL_CRATE};
10 use rustc_metadata::find_native_static_library;
11 use rustc_metadata::fs::{emit_wrapper_file, METADATA_FILENAME};
12 use rustc_middle::middle::dependency_format::Linkage;
13 use rustc_middle::middle::exported_symbols::SymbolExportKind;
14 use rustc_session::config::{self, CFGuard, CrateType, DebugInfo, LdImpl, Strip};
15 use rustc_session::config::{OutputFilenames, OutputType, PrintRequest, SplitDwarfKind};
16 use rustc_session::cstore::DllImport;
17 use rustc_session::output::{check_file_is_writeable, invalid_output_for_target, out_filename};
18 use rustc_session::search_paths::PathKind;
19 use rustc_session::utils::NativeLibKind;
20 /// For all the linkers we support, and information they might
21 /// need out of the shared crate context before we get rid of it.
22 use rustc_session::{filesearch, Session};
23 use rustc_span::symbol::Symbol;
24 use rustc_span::DebuggerVisualizerFile;
25 use rustc_target::spec::crt_objects::{CrtObjects, LinkSelfContainedDefault};
26 use rustc_target::spec::{Cc, LinkOutputKind, LinkerFlavor, LinkerFlavorCli, Lld, PanicStrategy};
27 use rustc_target::spec::{RelocModel, RelroLevel, SanitizerSet, SplitDebuginfo};
29 use super::archive::{ArchiveBuilder, ArchiveBuilderBuilder};
30 use super::command::Command;
31 use super::linker::{self, Linker};
32 use super::metadata::{create_wrapper_file, MetadataPosition};
33 use super::rpath::{self, RPathConfig};
35 errors, looks_like_rust_object_file, CodegenResults, CompiledModule, CrateInfo, NativeLib,
38 use cc::windows_registry;
40 use tempfile::Builder as TempFileBuilder;
42 use itertools::Itertools;
43 use std::borrow::Borrow;
44 use std::cell::OnceCell;
45 use std::collections::BTreeSet;
46 use std::ffi::OsString;
47 use std::fs::{read, File, OpenOptions};
48 use std::io::{BufWriter, Write};
50 use std::path::{Path, PathBuf};
51 use std::process::{ExitStatus, Output, Stdio};
52 use std::{env, fmt, fs, io, mem, str};
54 pub fn ensure_removed(diag_handler: &Handler, path: &Path) {
55 if let Err(e) = fs::remove_file(path) {
56 if e.kind() != io::ErrorKind::NotFound {
57 diag_handler.err(&format!("failed to remove {}: {}", path.display(), e));
62 /// Performs the linkage portion of the compilation phase. This will generate all
63 /// of the requested outputs for this compilation session.
64 pub fn link_binary<'a>(
66 archive_builder_builder: &dyn ArchiveBuilderBuilder,
67 codegen_results: &CodegenResults,
68 outputs: &OutputFilenames,
69 ) -> Result<(), ErrorGuaranteed> {
70 let _timer = sess.timer("link_binary");
71 let output_metadata = sess.opts.output_types.contains_key(&OutputType::Metadata);
72 for &crate_type in sess.crate_types().iter() {
73 // Ignore executable crates if we have -Z no-codegen, as they will error.
74 if (sess.opts.unstable_opts.no_codegen || !sess.opts.output_types.should_codegen())
76 && crate_type == CrateType::Executable
81 if invalid_output_for_target(sess, crate_type) {
83 "invalid output type `{:?}` for target os `{}`",
85 sess.opts.target_triple
89 sess.time("link_binary_check_files_are_writeable", || {
90 for obj in codegen_results.modules.iter().filter_map(|m| m.object.as_ref()) {
91 check_file_is_writeable(obj, sess);
95 if outputs.outputs.should_link() {
96 let tmpdir = TempFileBuilder::new()
99 .unwrap_or_else(|error| sess.emit_fatal(errors::CreateTempDir { error }));
100 let path = MaybeTempDir::new(tmpdir, sess.opts.cg.save_temps);
101 let out_filename = out_filename(
105 codegen_results.crate_info.local_crate_name,
109 let _timer = sess.timer("link_rlib");
110 info!("preparing rlib to {:?}", out_filename);
113 archive_builder_builder,
118 .build(&out_filename);
120 CrateType::Staticlib => {
123 archive_builder_builder,
132 archive_builder_builder,
140 if sess.opts.json_artifact_notifications {
141 sess.parse_sess.span_diagnostic.emit_artifact_notification(&out_filename, "link");
144 if sess.prof.enabled() {
145 if let Some(artifact_name) = out_filename.file_name() {
146 // Record size for self-profiling
147 let file_size = std::fs::metadata(&out_filename).map(|m| m.len()).unwrap_or(0);
149 sess.prof.artifact_size(
151 artifact_name.to_string_lossy(),
159 // Remove the temporary object file and metadata if we aren't saving temps.
160 sess.time("link_binary_remove_temps", || {
161 // If the user requests that temporaries are saved, don't delete any.
162 if sess.opts.cg.save_temps {
166 let maybe_remove_temps_from_module =
167 |preserve_objects: bool, preserve_dwarf_objects: bool, module: &CompiledModule| {
168 if !preserve_objects {
169 if let Some(ref obj) = module.object {
170 ensure_removed(sess.diagnostic(), obj);
174 if !preserve_dwarf_objects {
175 if let Some(ref dwo_obj) = module.dwarf_object {
176 ensure_removed(sess.diagnostic(), dwo_obj);
181 let remove_temps_from_module =
182 |module: &CompiledModule| maybe_remove_temps_from_module(false, false, module);
184 // Otherwise, always remove the metadata and allocator module temporaries.
185 if let Some(ref metadata_module) = codegen_results.metadata_module {
186 remove_temps_from_module(metadata_module);
189 if let Some(ref allocator_module) = codegen_results.allocator_module {
190 remove_temps_from_module(allocator_module);
193 // If no requested outputs require linking, then the object temporaries should
195 if !sess.opts.output_types.should_link() {
199 // Potentially keep objects for their debuginfo.
200 let (preserve_objects, preserve_dwarf_objects) = preserve_objects_for_their_debuginfo(sess);
201 debug!(?preserve_objects, ?preserve_dwarf_objects);
203 for module in &codegen_results.modules {
204 maybe_remove_temps_from_module(preserve_objects, preserve_dwarf_objects, module);
211 // Crate type is not passed when calculating the dylibs to include for LTO. In that case all
212 // crate types must use the same dependency formats.
213 pub fn each_linked_rlib(
215 crate_type: Option<CrateType>,
216 f: &mut dyn FnMut(CrateNum, &Path),
217 ) -> Result<(), errors::LinkRlibError> {
218 let crates = info.used_crates.iter();
220 let fmts = if crate_type.is_none() {
221 for combination in info.dependency_formats.iter().combinations(2) {
222 let (ty1, list1) = &combination[0];
223 let (ty2, list2) = &combination[1];
225 return Err(errors::LinkRlibError::IncompatibleDependencyFormats {
226 ty1: format!("{ty1:?}"),
227 ty2: format!("{ty2:?}"),
228 list1: format!("{list1:?}"),
229 list2: format!("{list2:?}"),
233 if info.dependency_formats.is_empty() {
234 return Err(errors::LinkRlibError::MissingFormat);
236 &info.dependency_formats[0].1
241 .find_map(|&(ty, ref list)| if Some(ty) == crate_type { Some(list) } else { None });
243 let Some(fmts) = fmts else {
244 return Err(errors::LinkRlibError::MissingFormat);
250 for &cnum in crates {
251 match fmts.get(cnum.as_usize() - 1) {
252 Some(&Linkage::NotLinked | &Linkage::Dynamic | &Linkage::IncludedFromDylib) => continue,
254 None => return Err(errors::LinkRlibError::MissingFormat),
256 let crate_name = info.crate_name[&cnum];
257 let used_crate_source = &info.used_crate_source[&cnum];
258 if let Some((path, _)) = &used_crate_source.rlib {
261 if used_crate_source.rmeta.is_some() {
262 return Err(errors::LinkRlibError::OnlyRmetaFound { crate_name });
264 return Err(errors::LinkRlibError::NotFound { crate_name });
271 /// Create an 'rlib'.
273 /// An rlib in its current incarnation is essentially a renamed .a file. The rlib primarily contains
274 /// the object file of the crate, but it also contains all of the object files from native
275 /// libraries. This is done by unzipping native libraries and inserting all of the contents into
279 archive_builder_builder: &dyn ArchiveBuilderBuilder,
280 codegen_results: &CodegenResults,
282 tmpdir: &MaybeTempDir,
283 ) -> Result<Box<dyn ArchiveBuilder<'a> + 'a>, ErrorGuaranteed> {
284 let lib_search_paths = archive_search_paths(sess);
286 let mut ab = archive_builder_builder.new_archive_builder(sess);
288 let trailing_metadata = match flavor {
289 RlibFlavor::Normal => {
290 let (metadata, metadata_position) =
291 create_wrapper_file(sess, b".rmeta".to_vec(), codegen_results.metadata.raw_data());
292 let metadata = emit_wrapper_file(sess, &metadata, tmpdir, METADATA_FILENAME);
293 match metadata_position {
294 MetadataPosition::First => {
295 // Most of the time metadata in rlib files is wrapped in a "dummy" object
296 // file for the target platform so the rlib can be processed entirely by
297 // normal linkers for the platform. Sometimes this is not possible however.
298 // If it is possible however, placing the metadata object first improves
299 // performance of getting metadata from rlibs.
300 ab.add_file(&metadata);
303 MetadataPosition::Last => Some(metadata),
307 RlibFlavor::StaticlibBase => None,
310 for m in &codegen_results.modules {
311 if let Some(obj) = m.object.as_ref() {
315 if let Some(dwarf_obj) = m.dwarf_object.as_ref() {
316 ab.add_file(dwarf_obj);
321 RlibFlavor::Normal => {}
322 RlibFlavor::StaticlibBase => {
323 let obj = codegen_results.allocator_module.as_ref().and_then(|m| m.object.as_ref());
324 if let Some(obj) = obj {
330 // Used if packed_bundled_libs flag enabled.
331 let mut packed_bundled_libs = Vec::new();
333 // Note that in this loop we are ignoring the value of `lib.cfg`. That is,
334 // we may not be configured to actually include a static library if we're
335 // adding it here. That's because later when we consume this rlib we'll
336 // decide whether we actually needed the static library or not.
338 // To do this "correctly" we'd need to keep track of which libraries added
339 // which object files to the archive. We don't do that here, however. The
340 // #[link(cfg(..))] feature is unstable, though, and only intended to get
341 // liblibc working. In that sense the check below just indicates that if
342 // there are any libraries we want to omit object files for at link time we
343 // just exclude all custom object files.
345 // Eventually if we want to stabilize or flesh out the #[link(cfg(..))]
346 // feature then we'll need to figure out how to record what objects were
347 // loaded from the libraries found here and then encode that into the
348 // metadata of the rlib we're generating somehow.
349 for lib in codegen_results.crate_info.used_libraries.iter() {
351 NativeLibKind::Static { bundle: None | Some(true), whole_archive: Some(true) }
352 if flavor == RlibFlavor::Normal && sess.opts.unstable_opts.packed_bundled_libs => {}
353 NativeLibKind::Static { bundle: None | Some(true), whole_archive: Some(true) }
354 if flavor == RlibFlavor::Normal =>
356 // Don't allow mixing +bundle with +whole_archive since an rlib may contain
357 // multiple native libs, some of which are +whole-archive and some of which are
358 // -whole-archive and it isn't clear how we can currently handle such a
359 // situation correctly.
360 // See https://github.com/rust-lang/rust/issues/88085#issuecomment-901050897
361 sess.emit_err(errors::IncompatibleLinkingModifiers);
363 NativeLibKind::Static { bundle: None | Some(true), .. } => {}
364 NativeLibKind::Static { bundle: Some(false), .. }
365 | NativeLibKind::Dylib { .. }
366 | NativeLibKind::Framework { .. }
367 | NativeLibKind::RawDylib
368 | NativeLibKind::LinkArg
369 | NativeLibKind::Unspecified => continue,
371 if let Some(name) = lib.name {
373 find_native_static_library(name.as_str(), lib.verbatim, &lib_search_paths, sess);
374 if sess.opts.unstable_opts.packed_bundled_libs && flavor == RlibFlavor::Normal {
375 let filename = lib.filename.unwrap();
377 find_native_static_library(filename.as_str(), true, &lib_search_paths, sess);
378 let src = read(lib_path)
379 .map_err(|e| sess.emit_fatal(errors::ReadFileError { message: e }))?;
380 let (data, _) = create_wrapper_file(sess, b".bundled_lib".to_vec(), &src);
381 let wrapper_file = emit_wrapper_file(sess, &data, tmpdir, filename.as_str());
382 packed_bundled_libs.push(wrapper_file);
385 ab.add_archive(&location, Box::new(|_| false)).unwrap_or_else(|error| {
386 sess.emit_fatal(errors::AddNativeLibrary { library_path: location, error });
391 for (raw_dylib_name, raw_dylib_imports) in
392 collate_raw_dylibs(sess, codegen_results.crate_info.used_libraries.iter())?
394 let output_path = archive_builder_builder.create_dll_import_lib(
402 ab.add_archive(&output_path, Box::new(|_| false)).unwrap_or_else(|error| {
403 sess.emit_fatal(errors::AddNativeLibrary { library_path: output_path, error });
407 if let Some(trailing_metadata) = trailing_metadata {
408 // Note that it is important that we add all of our non-object "magical
409 // files" *after* all of the object files in the archive. The reason for
410 // this is as follows:
412 // * When performing LTO, this archive will be modified to remove
413 // objects from above. The reason for this is described below.
415 // * When the system linker looks at an archive, it will attempt to
416 // determine the architecture of the archive in order to see whether its
419 // The algorithm for this detection is: iterate over the files in the
420 // archive. Skip magical SYMDEF names. Interpret the first file as an
421 // object file. Read architecture from the object file.
423 // * As one can probably see, if "metadata" and "foo.bc" were placed
424 // before all of the objects, then the architecture of this archive would
425 // not be correctly inferred once 'foo.o' is removed.
427 // * Most of the time metadata in rlib files is wrapped in a "dummy" object
428 // file for the target platform so the rlib can be processed entirely by
429 // normal linkers for the platform. Sometimes this is not possible however.
431 // Basically, all this means is that this code should not move above the
433 ab.add_file(&trailing_metadata);
436 // Add all bundled static native library dependencies.
437 // Archives added to the end of .rlib archive, see comment above for the reason.
438 for lib in packed_bundled_libs {
445 /// Extract all symbols defined in raw-dylib libraries, collated by library name.
447 /// If we have multiple extern blocks that specify symbols defined in the same raw-dylib library,
448 /// then the CodegenResults value contains one NativeLib instance for each block. However, the
449 /// linker appears to expect only a single import library for each library used, so we need to
450 /// collate the symbols together by library name before generating the import libraries.
451 fn collate_raw_dylibs<'a, 'b>(
453 used_libraries: impl IntoIterator<Item = &'b NativeLib>,
454 ) -> Result<Vec<(String, Vec<DllImport>)>, ErrorGuaranteed> {
455 // Use index maps to preserve original order of imports and libraries.
456 let mut dylib_table = FxIndexMap::<String, FxIndexMap<Symbol, &DllImport>>::default();
458 for lib in used_libraries {
459 if lib.kind == NativeLibKind::RawDylib {
460 let ext = if lib.verbatim { "" } else { ".dll" };
461 let name = format!("{}{}", lib.name.expect("unnamed raw-dylib library"), ext);
462 let imports = dylib_table.entry(name.clone()).or_default();
463 for import in &lib.dll_imports {
464 if let Some(old_import) = imports.insert(import.name, import) {
465 // FIXME: when we add support for ordinals, figure out if we need to do anything
466 // if we have two DllImport values with the same name but different ordinals.
467 if import.calling_convention != old_import.calling_convention {
468 sess.emit_err(errors::MultipleExternalFuncDecl {
470 function: import.name,
478 sess.compile_status()?;
481 .map(|(name, imports)| {
482 (name, imports.into_iter().map(|(_, import)| import.clone()).collect())
487 /// Create a static archive.
489 /// This is essentially the same thing as an rlib, but it also involves adding all of the upstream
490 /// crates' objects into the archive. This will slurp in all of the native libraries of upstream
491 /// dependencies as well.
493 /// Additionally, there's no way for us to link dynamic libraries, so we warn about all dynamic
494 /// library dependencies that they're not linked in.
496 /// There's no need to include metadata in a static archive, so ensure to not link in the metadata
497 /// object file (and also don't prepare the archive with a metadata file).
498 fn link_staticlib<'a>(
500 archive_builder_builder: &dyn ArchiveBuilderBuilder,
501 codegen_results: &CodegenResults,
503 tempdir: &MaybeTempDir,
504 ) -> Result<(), ErrorGuaranteed> {
505 info!("preparing staticlib to {:?}", out_filename);
506 let mut ab = link_rlib(
508 archive_builder_builder,
510 RlibFlavor::StaticlibBase,
513 let mut all_native_libs = vec![];
515 let res = each_linked_rlib(
516 &codegen_results.crate_info,
517 Some(CrateType::Staticlib),
519 let name = codegen_results.crate_info.crate_name[&cnum];
520 let native_libs = &codegen_results.crate_info.native_libraries[&cnum];
522 // Here when we include the rlib into our staticlib we need to make a
523 // decision whether to include the extra object files along the way.
524 // These extra object files come from statically included native
525 // libraries, but they may be cfg'd away with #[link(cfg(..))].
527 // This unstable feature, though, only needs liblibc to work. The only
528 // use case there is where musl is statically included in liblibc.rlib,
529 // so if we don't want the included version we just need to skip it. As
530 // a result the logic here is that if *any* linked library is cfg'd away
531 // we just skip all object files.
533 // Clearly this is not sufficient for a general purpose feature, and
534 // we'd want to read from the library's metadata to determine which
535 // object files come from where and selectively skip them.
536 let skip_object_files = native_libs.iter().any(|lib| {
537 matches!(lib.kind, NativeLibKind::Static { bundle: None | Some(true), .. })
538 && !relevant_lib(sess, lib)
541 let lto = are_upstream_rust_objects_already_included(sess)
542 && !ignored_for_lto(sess, &codegen_results.crate_info, cnum);
544 // Ignoring obj file starting with the crate name
545 // as simple comparison is not enough - there
546 // might be also an extra name suffix
547 let obj_start = name.as_str().to_owned();
551 Box::new(move |fname: &str| {
552 // Ignore metadata files, no matter the name.
553 if fname == METADATA_FILENAME {
557 // Don't include Rust objects if LTO is enabled
558 if lto && looks_like_rust_object_file(fname) {
562 // Otherwise if this is *not* a rust object and we're skipping
563 // objects then skip this file
565 && (!fname.starts_with(&obj_start) || !fname.ends_with(".o"))
570 // ok, don't skip this
577 .extend(codegen_results.crate_info.native_libraries[&cnum].iter().cloned());
580 if let Err(e) = res {
584 ab.build(out_filename);
586 if !all_native_libs.is_empty() {
587 if sess.opts.prints.contains(&PrintRequest::NativeStaticLibs) {
588 print_native_static_libs(sess, &all_native_libs);
595 /// Use `thorin` (rust implementation of a dwarf packaging utility) to link DWARF objects into a
597 fn link_dwarf_object<'a>(
599 cg_results: &CodegenResults,
600 executable_out_filename: &Path,
602 let dwp_out_filename = executable_out_filename.with_extension("dwp");
603 debug!(?dwp_out_filename, ?executable_out_filename);
606 struct ThorinSession<Relocations> {
607 arena_data: TypedArena<Vec<u8>>,
608 arena_mmap: TypedArena<Mmap>,
609 arena_relocations: TypedArena<Relocations>,
612 impl<Relocations> ThorinSession<Relocations> {
613 fn alloc_mmap(&self, data: Mmap) -> &Mmap {
614 (*self.arena_mmap.alloc(data)).borrow()
618 impl<Relocations> thorin::Session<Relocations> for ThorinSession<Relocations> {
619 fn alloc_data(&self, data: Vec<u8>) -> &[u8] {
620 (*self.arena_data.alloc(data)).borrow()
623 fn alloc_relocation(&self, data: Relocations) -> &Relocations {
624 (*self.arena_relocations.alloc(data)).borrow()
627 fn read_input(&self, path: &Path) -> std::io::Result<&[u8]> {
628 let file = File::open(&path)?;
629 let mmap = (unsafe { Mmap::map(file) })?;
630 Ok(self.alloc_mmap(mmap))
634 match sess.time("run_thorin", || -> Result<(), thorin::Error> {
635 let thorin_sess = ThorinSession::default();
636 let mut package = thorin::DwarfPackage::new(&thorin_sess);
638 // Input objs contain .o/.dwo files from the current crate.
639 match sess.opts.unstable_opts.split_dwarf_kind {
640 SplitDwarfKind::Single => {
641 for input_obj in cg_results.modules.iter().filter_map(|m| m.object.as_ref()) {
642 package.add_input_object(input_obj)?;
645 SplitDwarfKind::Split => {
646 for input_obj in cg_results.modules.iter().filter_map(|m| m.dwarf_object.as_ref()) {
647 package.add_input_object(input_obj)?;
652 // Input rlibs contain .o/.dwo files from dependencies.
653 let input_rlibs = cg_results
657 .filter_map(|csource| csource.rlib.as_ref())
658 .map(|(path, _)| path);
659 for input_rlib in input_rlibs {
661 package.add_input_object(input_rlib)?;
664 // Failing to read the referenced objects is expected for dependencies where the path in the
665 // executable will have been cleaned by Cargo, but the referenced objects will be contained
666 // within rlibs provided as inputs.
668 // If paths have been remapped, then .o/.dwo files from the current crate also won't be
669 // found, but are provided explicitly above.
671 // Adding an executable is primarily done to make `thorin` check that all the referenced
672 // dwarf objects are found in the end.
673 package.add_executable(
674 &executable_out_filename,
675 thorin::MissingReferencedObjectBehaviour::Skip,
678 let output_stream = BufWriter::new(
684 .open(dwp_out_filename)?,
686 let mut output_stream = object::write::StreamingBuffer::new(output_stream);
687 package.finish()?.emit(&mut output_stream)?;
688 output_stream.result()?;
689 output_stream.into_inner().flush()?;
695 sess.emit_err(errors::ThorinErrorWrapper(e));
696 sess.abort_if_errors();
701 /// Create a dynamic library or executable.
703 /// This will invoke the system linker/cc to create the resulting file. This links to all upstream
705 fn link_natively<'a>(
707 archive_builder_builder: &dyn ArchiveBuilderBuilder,
708 crate_type: CrateType,
710 codegen_results: &CodegenResults,
712 ) -> Result<(), ErrorGuaranteed> {
713 info!("preparing {:?} to {:?}", crate_type, out_filename);
714 let (linker_path, flavor) = linker_and_flavor(sess);
715 let mut cmd = linker_with_args(
719 archive_builder_builder,
726 linker::disable_localization(&mut cmd);
728 for (k, v) in sess.target.link_env.as_ref() {
729 cmd.env(k.as_ref(), v.as_ref());
731 for k in sess.target.link_env_remove.as_ref() {
732 cmd.env_remove(k.as_ref());
735 if sess.opts.prints.contains(&PrintRequest::LinkArgs) {
736 println!("{:?}", &cmd);
739 // May have not found libraries in the right formats.
740 sess.abort_if_errors();
742 // Invoke the system linker
744 let retry_on_segfault = env::var("RUSTC_RETRY_LINKER_ON_SEGFAULT").is_ok();
745 let unknown_arg_regex =
746 Regex::new(r"(unknown|unrecognized) (command line )?(option|argument)").unwrap();
751 prog = sess.time("run_linker", || exec_linker(sess, &cmd, out_filename, tmpdir));
752 let Ok(ref output) = prog else {
755 if output.status.success() {
758 let mut out = output.stderr.clone();
759 out.extend(&output.stdout);
760 let out = String::from_utf8_lossy(&out);
762 // Check to see if the link failed with an error message that indicates it
763 // doesn't recognize the -no-pie option. If so, re-perform the link step
764 // without it. This is safe because if the linker doesn't support -no-pie
765 // then it should not default to linking executables as pie. Different
766 // versions of gcc seem to use different quotes in the error message so
767 // don't check for them.
768 if matches!(flavor, LinkerFlavor::Gnu(Cc::Yes, _))
769 && unknown_arg_regex.is_match(&out)
770 && out.contains("-no-pie")
771 && cmd.get_args().iter().any(|e| e.to_string_lossy() == "-no-pie")
773 info!("linker output: {:?}", out);
774 warn!("Linker does not support -no-pie command line option. Retrying without.");
775 for arg in cmd.take_args() {
776 if arg.to_string_lossy() != "-no-pie" {
784 // Detect '-static-pie' used with an older version of gcc or clang not supporting it.
785 // Fallback from '-static-pie' to '-static' in that case.
786 if matches!(flavor, LinkerFlavor::Gnu(Cc::Yes, _))
787 && unknown_arg_regex.is_match(&out)
788 && (out.contains("-static-pie") || out.contains("--no-dynamic-linker"))
789 && cmd.get_args().iter().any(|e| e.to_string_lossy() == "-static-pie")
791 info!("linker output: {:?}", out);
793 "Linker does not support -static-pie command line option. Retrying with -static instead."
795 // Mirror `add_(pre,post)_link_objects` to replace CRT objects.
796 let self_contained = self_contained(sess, crate_type);
797 let opts = &sess.target;
798 let pre_objects = if self_contained {
799 &opts.pre_link_objects_self_contained
801 &opts.pre_link_objects
803 let post_objects = if self_contained {
804 &opts.post_link_objects_self_contained
806 &opts.post_link_objects
808 let get_objects = |objects: &CrtObjects, kind| {
814 .map(|obj| get_object_file_path(sess, obj, self_contained).into_os_string())
817 let pre_objects_static_pie = get_objects(pre_objects, LinkOutputKind::StaticPicExe);
818 let post_objects_static_pie = get_objects(post_objects, LinkOutputKind::StaticPicExe);
819 let mut pre_objects_static = get_objects(pre_objects, LinkOutputKind::StaticNoPicExe);
820 let mut post_objects_static = get_objects(post_objects, LinkOutputKind::StaticNoPicExe);
821 // Assume that we know insertion positions for the replacement arguments from replaced
822 // arguments, which is true for all supported targets.
823 assert!(pre_objects_static.is_empty() || !pre_objects_static_pie.is_empty());
824 assert!(post_objects_static.is_empty() || !post_objects_static_pie.is_empty());
825 for arg in cmd.take_args() {
826 if arg.to_string_lossy() == "-static-pie" {
827 // Replace the output kind.
829 } else if pre_objects_static_pie.contains(&arg) {
830 // Replace the pre-link objects (replace the first and remove the rest).
831 cmd.args(mem::take(&mut pre_objects_static));
832 } else if post_objects_static_pie.contains(&arg) {
833 // Replace the post-link objects (replace the first and remove the rest).
834 cmd.args(mem::take(&mut post_objects_static));
843 // Here's a terribly awful hack that really shouldn't be present in any
844 // compiler. Here an environment variable is supported to automatically
845 // retry the linker invocation if the linker looks like it segfaulted.
847 // Gee that seems odd, normally segfaults are things we want to know
848 // about! Unfortunately though in rust-lang/rust#38878 we're
849 // experiencing the linker segfaulting on Travis quite a bit which is
850 // causing quite a bit of pain to land PRs when they spuriously fail
851 // due to a segfault.
853 // The issue #38878 has some more debugging information on it as well,
854 // but this unfortunately looks like it's just a race condition in
855 // macOS's linker with some thread pool working in the background. It
856 // seems that no one currently knows a fix for this so in the meantime
857 // we're left with this...
858 if !retry_on_segfault || i > 3 {
861 let msg_segv = "clang: error: unable to execute command: Segmentation fault: 11";
862 let msg_bus = "clang: error: unable to execute command: Bus error: 10";
863 if out.contains(msg_segv) || out.contains(msg_bus) {
866 "looks like the linker segfaulted when we tried to call it, \
867 automatically retrying again",
872 if is_illegal_instruction(&output.status) {
874 ?cmd, %out, status = %output.status,
875 "looks like the linker hit an illegal instruction when we \
876 tried to call it, automatically retrying again.",
882 fn is_illegal_instruction(status: &ExitStatus) -> bool {
883 use std::os::unix::prelude::*;
884 status.signal() == Some(libc::SIGILL)
888 fn is_illegal_instruction(_status: &ExitStatus) -> bool {
895 if !prog.status.success() {
896 let mut output = prog.stderr.clone();
897 output.extend_from_slice(&prog.stdout);
898 let escaped_output = escape_string(&output);
899 // FIXME: Add UI tests for this error.
900 let err = errors::LinkingFailed {
901 linker_path: &linker_path,
902 exit_status: prog.status,
904 escaped_output: &escaped_output,
906 sess.diagnostic().emit_err(err);
907 // If MSVC's `link.exe` was expected but the return code
908 // is not a Microsoft LNK error then suggest a way to fix or
909 // install the Visual Studio build tools.
910 if let Some(code) = prog.status.code() {
911 if sess.target.is_like_msvc
912 && flavor == LinkerFlavor::Msvc(Lld::No)
913 // Respect the command line override
914 && sess.opts.cg.linker.is_none()
915 // Match exactly "link.exe"
916 && linker_path.to_str() == Some("link.exe")
917 // All Microsoft `link.exe` linking error codes are
918 // four digit numbers in the range 1000 to 9999 inclusive
919 && (code < 1000 || code > 9999)
921 let is_vs_installed = windows_registry::find_vs_version().is_ok();
922 let has_linker = windows_registry::find_tool(
923 &sess.opts.target_triple.triple(),
928 sess.emit_note(errors::LinkExeUnexpectedError);
929 if is_vs_installed && has_linker {
930 // the linker is broken
931 sess.emit_note(errors::RepairVSBuildTools);
932 sess.emit_note(errors::MissingCppBuildToolComponent);
933 } else if is_vs_installed {
934 // the linker is not installed
935 sess.emit_note(errors::SelectCppBuildToolWorkload);
937 // visual studio is not installed
938 sess.emit_note(errors::VisualStudioNotInstalled);
943 sess.abort_if_errors();
945 info!("linker stderr:\n{}", escape_string(&prog.stderr));
946 info!("linker stdout:\n{}", escape_string(&prog.stdout));
949 let linker_not_found = e.kind() == io::ErrorKind::NotFound;
951 if linker_not_found {
952 sess.emit_err(errors::LinkerNotFound { linker_path, error: e });
954 sess.emit_err(errors::UnableToExeLinker {
957 command_formatted: format!("{:?}", &cmd),
961 if sess.target.is_like_msvc && linker_not_found {
962 sess.emit_note(errors::MsvcMissingLinker);
963 sess.emit_note(errors::CheckInstalledVisualStudio);
964 sess.emit_note(errors::UnsufficientVSCodeProduct);
966 sess.abort_if_errors();
970 match sess.split_debuginfo() {
971 // If split debug information is disabled or located in individual files
972 // there's nothing to do here.
973 SplitDebuginfo::Off | SplitDebuginfo::Unpacked => {}
975 // If packed split-debuginfo is requested, but the final compilation
976 // doesn't actually have any debug information, then we skip this step.
977 SplitDebuginfo::Packed if sess.opts.debuginfo == DebugInfo::None => {}
979 // On macOS the external `dsymutil` tool is used to create the packed
980 // debug information. Note that this will read debug information from
981 // the objects on the filesystem which we'll clean up later.
982 SplitDebuginfo::Packed if sess.target.is_like_osx => {
983 let prog = Command::new("dsymutil").arg(out_filename).output();
986 if !prog.status.success() {
987 let mut output = prog.stderr.clone();
988 output.extend_from_slice(&prog.stdout);
989 sess.emit_warning(errors::ProcessingDymutilFailed {
991 output: escape_string(&output),
995 Err(error) => sess.emit_fatal(errors::UnableToRunDsymutil { error }),
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, _) => {
1016 strip_symbols_with_external_utility(sess, "strip", &out_filename, Some("-S"))
1018 // Per the manpage, `-x` is the maximum safe strip level for dynamic libraries. (#93988)
1019 (Strip::Symbols, CrateType::Dylib | CrateType::Cdylib | CrateType::ProcMacro) => {
1020 strip_symbols_with_external_utility(sess, "strip", &out_filename, Some("-x"))
1022 (Strip::Symbols, _) => {
1023 strip_symbols_with_external_utility(sess, "strip", &out_filename, None)
1025 (Strip::None, _) => {}
1029 if sess.target.os == "illumos" {
1030 // Many illumos systems will have both the native 'strip' utility and
1031 // the GNU one. Use the native version explicitly and do not rely on
1032 // what's in the path.
1033 let stripcmd = "/usr/bin/strip";
1035 // Always preserve the symbol table (-x).
1036 Strip::Debuginfo => {
1037 strip_symbols_with_external_utility(sess, stripcmd, &out_filename, Some("-x"))
1039 // Strip::Symbols is handled via the --strip-all linker option.
1040 Strip::Symbols => {}
1048 // Temporarily support both -Z strip and -C strip
1049 fn strip_value(sess: &Session) -> Strip {
1050 match (sess.opts.unstable_opts.strip, sess.opts.cg.strip) {
1051 (s, Strip::None) => s,
1056 fn strip_symbols_with_external_utility<'a>(
1059 out_filename: &Path,
1060 option: Option<&str>,
1062 let mut cmd = Command::new(util);
1063 if let Some(option) = option {
1066 let prog = cmd.arg(out_filename).output();
1069 if !prog.status.success() {
1070 let mut output = prog.stderr.clone();
1071 output.extend_from_slice(&prog.stdout);
1072 sess.emit_warning(errors::StrippingDebugInfoFailed {
1074 status: prog.status,
1075 output: escape_string(&output),
1079 Err(error) => sess.emit_fatal(errors::UnableToRun { util, error }),
1083 fn escape_string(s: &[u8]) -> String {
1084 match str::from_utf8(s) {
1085 Ok(s) => s.to_owned(),
1086 Err(_) => format!("Non-UTF-8 output: {}", s.escape_ascii()),
1090 fn add_sanitizer_libraries(sess: &Session, crate_type: CrateType, linker: &mut dyn Linker) {
1091 // On macOS the runtimes are distributed as dylibs which should be linked to
1092 // both executables and dynamic shared objects. Everywhere else the runtimes
1093 // are currently distributed as static libraries which should be linked to
1094 // executables only.
1095 let needs_runtime = !sess.target.is_like_android
1096 && match crate_type {
1097 CrateType::Executable => true,
1098 CrateType::Dylib | CrateType::Cdylib | CrateType::ProcMacro => sess.target.is_like_osx,
1099 CrateType::Rlib | CrateType::Staticlib => false,
1106 let sanitizer = sess.opts.unstable_opts.sanitizer;
1107 if sanitizer.contains(SanitizerSet::ADDRESS) {
1108 link_sanitizer_runtime(sess, linker, "asan");
1110 if sanitizer.contains(SanitizerSet::LEAK) {
1111 link_sanitizer_runtime(sess, linker, "lsan");
1113 if sanitizer.contains(SanitizerSet::MEMORY) {
1114 link_sanitizer_runtime(sess, linker, "msan");
1116 if sanitizer.contains(SanitizerSet::THREAD) {
1117 link_sanitizer_runtime(sess, linker, "tsan");
1119 if sanitizer.contains(SanitizerSet::HWADDRESS) {
1120 link_sanitizer_runtime(sess, linker, "hwasan");
1124 fn link_sanitizer_runtime(sess: &Session, linker: &mut dyn Linker, name: &str) {
1125 fn find_sanitizer_runtime(sess: &Session, filename: &str) -> PathBuf {
1127 filesearch::make_target_lib_path(&sess.sysroot, sess.opts.target_triple.triple());
1128 let path = session_tlib.join(filename);
1130 return session_tlib;
1132 let default_sysroot =
1133 filesearch::get_or_default_sysroot().expect("Failed finding sysroot");
1134 let default_tlib = filesearch::make_target_lib_path(
1136 sess.opts.target_triple.triple(),
1138 return default_tlib;
1142 let channel = option_env!("CFG_RELEASE_CHANNEL")
1143 .map(|channel| format!("-{}", channel))
1144 .unwrap_or_default();
1146 if sess.target.is_like_osx {
1147 // On Apple platforms, the sanitizer is always built as a dylib, and
1148 // LLVM will link to `@rpath/*.dylib`, so we need to specify an
1149 // rpath to the library as well (the rpath should be absolute, see
1150 // PR #41352 for details).
1151 let filename = format!("rustc{}_rt.{}", channel, name);
1152 let path = find_sanitizer_runtime(&sess, &filename);
1153 let rpath = path.to_str().expect("non-utf8 component in path");
1154 linker.args(&["-Wl,-rpath", "-Xlinker", rpath]);
1155 linker.link_dylib(&filename, false, true);
1157 let filename = format!("librustc{}_rt.{}.a", channel, name);
1158 let path = find_sanitizer_runtime(&sess, &filename).join(&filename);
1159 linker.link_whole_rlib(&path);
1163 /// Returns a boolean indicating whether the specified crate should be ignored
1166 /// Crates ignored during LTO are not lumped together in the "massive object
1167 /// file" that we create and are linked in their normal rlib states. See
1168 /// comments below for what crates do not participate in LTO.
1170 /// It's unusual for a crate to not participate in LTO. Typically only
1171 /// compiler-specific and unstable crates have a reason to not participate in
1173 pub fn ignored_for_lto(sess: &Session, info: &CrateInfo, cnum: CrateNum) -> bool {
1174 // If our target enables builtin function lowering in LLVM then the
1175 // crates providing these functions don't participate in LTO (e.g.
1176 // no_builtins or compiler builtins crates).
1177 !sess.target.no_builtins
1178 && (info.compiler_builtins == Some(cnum) || info.is_no_builtins.contains(&cnum))
1181 /// This functions tries to determine the appropriate linker (and corresponding LinkerFlavor) to use
1182 pub fn linker_and_flavor(sess: &Session) -> (PathBuf, LinkerFlavor) {
1185 linker: Option<PathBuf>,
1186 flavor: Option<LinkerFlavor>,
1187 ) -> Option<(PathBuf, LinkerFlavor)> {
1188 match (linker, flavor) {
1189 (Some(linker), Some(flavor)) => Some((linker, flavor)),
1190 // only the linker flavor is known; use the default linker for the selected flavor
1191 (None, Some(flavor)) => Some((
1192 PathBuf::from(match flavor {
1193 LinkerFlavor::Gnu(Cc::Yes, _)
1194 | LinkerFlavor::Darwin(Cc::Yes, _)
1195 | LinkerFlavor::WasmLld(Cc::Yes)
1196 | LinkerFlavor::Unix(Cc::Yes) => {
1197 if cfg!(any(target_os = "solaris", target_os = "illumos")) {
1198 // On historical Solaris systems, "cc" may have
1199 // been Sun Studio, which is not flag-compatible
1200 // with "gcc". This history casts a long shadow,
1201 // and many modern illumos distributions today
1202 // ship GCC as "gcc" without also making it
1203 // available as "cc".
1209 LinkerFlavor::Gnu(_, Lld::Yes)
1210 | LinkerFlavor::Darwin(_, Lld::Yes)
1211 | LinkerFlavor::WasmLld(..)
1212 | LinkerFlavor::Msvc(Lld::Yes) => "lld",
1213 LinkerFlavor::Gnu(..) | LinkerFlavor::Darwin(..) | LinkerFlavor::Unix(..) => {
1216 LinkerFlavor::Msvc(..) => "link.exe",
1217 LinkerFlavor::EmCc => {
1224 LinkerFlavor::Bpf => "bpf-linker",
1225 LinkerFlavor::Ptx => "rust-ptx-linker",
1229 (Some(linker), None) => {
1230 let stem = linker.file_stem().and_then(|stem| stem.to_str()).unwrap_or_else(|| {
1231 sess.emit_fatal(errors::LinkerFileStem);
1234 // Remove any version postfix.
1237 .and_then(|(lhs, rhs)| rhs.chars().all(char::is_numeric).then_some(lhs))
1240 // GCC can have an optional target prefix.
1241 let flavor = if stem == "emcc" {
1243 } else if stem == "gcc"
1244 || stem.ends_with("-gcc")
1246 || stem.ends_with("-g++")
1248 || stem == "clang++"
1250 LinkerFlavor::from_cli(LinkerFlavorCli::Gcc, &sess.target)
1251 } else if stem == "wasm-ld" || stem.ends_with("-wasm-ld") {
1252 LinkerFlavor::WasmLld(Cc::No)
1253 } else if stem == "ld" || stem.ends_with("-ld") {
1254 LinkerFlavor::from_cli(LinkerFlavorCli::Ld, &sess.target)
1255 } else if stem == "ld.lld" {
1256 LinkerFlavor::Gnu(Cc::No, Lld::Yes)
1257 } else if stem == "link" {
1258 LinkerFlavor::Msvc(Lld::No)
1259 } else if stem == "lld-link" {
1260 LinkerFlavor::Msvc(Lld::Yes)
1261 } else if stem == "lld" || stem == "rust-lld" {
1262 let lld_flavor = sess.target.linker_flavor.lld_flavor();
1263 LinkerFlavor::from_cli(LinkerFlavorCli::Lld(lld_flavor), &sess.target)
1265 // fall back to the value in the target spec
1266 sess.target.linker_flavor
1269 Some((linker, flavor))
1271 (None, None) => None,
1275 // linker and linker flavor specified via command line have precedence over what the target
1276 // specification specifies
1278 sess.opts.cg.linker_flavor.map(|flavor| LinkerFlavor::from_cli(flavor, &sess.target));
1279 if let Some(ret) = infer_from(sess, sess.opts.cg.linker.clone(), linker_flavor) {
1283 if let Some(ret) = infer_from(
1285 sess.target.linker.as_deref().map(PathBuf::from),
1286 Some(sess.target.linker_flavor),
1291 bug!("Not enough information provided to determine how to invoke the linker");
1294 /// Returns a pair of boolean indicating whether we should preserve the object and
1295 /// dwarf object files on the filesystem for their debug information. This is often
1296 /// useful with split-dwarf like schemes.
1297 fn preserve_objects_for_their_debuginfo(sess: &Session) -> (bool, bool) {
1298 // If the objects don't have debuginfo there's nothing to preserve.
1299 if sess.opts.debuginfo == config::DebugInfo::None {
1300 return (false, false);
1303 // If we're only producing artifacts that are archives, no need to preserve
1304 // the objects as they're losslessly contained inside the archives.
1305 if sess.crate_types().iter().all(|&x| x.is_archive()) {
1306 return (false, false);
1309 match (sess.split_debuginfo(), sess.opts.unstable_opts.split_dwarf_kind) {
1310 // If there is no split debuginfo then do not preserve objects.
1311 (SplitDebuginfo::Off, _) => (false, false),
1312 // If there is packed split debuginfo, then the debuginfo in the objects
1313 // has been packaged and the objects can be deleted.
1314 (SplitDebuginfo::Packed, _) => (false, false),
1315 // If there is unpacked split debuginfo and the current target can not use
1316 // split dwarf, then keep objects.
1317 (SplitDebuginfo::Unpacked, _) if !sess.target_can_use_split_dwarf() => (true, false),
1318 // If there is unpacked split debuginfo and the target can use split dwarf, then
1319 // keep the object containing that debuginfo (whether that is an object file or
1320 // dwarf object file depends on the split dwarf kind).
1321 (SplitDebuginfo::Unpacked, SplitDwarfKind::Single) => (true, false),
1322 (SplitDebuginfo::Unpacked, SplitDwarfKind::Split) => (false, true),
1326 fn archive_search_paths(sess: &Session) -> Vec<PathBuf> {
1327 sess.target_filesearch(PathKind::Native).search_path_dirs()
1330 #[derive(PartialEq)]
1336 fn print_native_static_libs(sess: &Session, all_native_libs: &[NativeLib]) {
1337 let lib_args: Vec<_> = all_native_libs
1339 .filter(|l| relevant_lib(sess, l))
1341 let name = lib.name?;
1343 NativeLibKind::Static { bundle: Some(false), .. }
1344 | NativeLibKind::Dylib { .. }
1345 | NativeLibKind::Unspecified => {
1346 let verbatim = lib.verbatim;
1347 if sess.target.is_like_msvc {
1348 Some(format!("{}{}", name, if verbatim { "" } else { ".lib" }))
1349 } else if sess.target.linker_flavor.is_gnu() {
1350 Some(format!("-l{}{}", if verbatim { ":" } else { "" }, name))
1352 Some(format!("-l{}", name))
1355 NativeLibKind::Framework { .. } => {
1356 // ld-only syntax, since there are no frameworks in MSVC
1357 Some(format!("-framework {}", name))
1359 // These are included, no need to print them
1360 NativeLibKind::Static { bundle: None | Some(true), .. }
1361 | NativeLibKind::LinkArg
1362 | NativeLibKind::RawDylib => None,
1366 if !lib_args.is_empty() {
1367 sess.emit_note(errors::StaticLibraryNativeArtifacts);
1368 // Prefix for greppability
1369 // Note: This must not be translated as tools are allowed to depend on this exact string.
1370 sess.note_without_error(&format!("native-static-libs: {}", &lib_args.join(" ")));
1374 fn get_object_file_path(sess: &Session, name: &str, self_contained: bool) -> PathBuf {
1375 let fs = sess.target_filesearch(PathKind::Native);
1376 let file_path = fs.get_lib_path().join(name);
1377 if file_path.exists() {
1380 // Special directory with objects used only in self-contained linkage mode
1382 let file_path = fs.get_self_contained_lib_path().join(name);
1383 if file_path.exists() {
1387 for search_path in fs.search_paths() {
1388 let file_path = search_path.dir.join(name);
1389 if file_path.exists() {
1399 out_filename: &Path,
1401 ) -> io::Result<Output> {
1402 // When attempting to spawn the linker we run a risk of blowing out the
1403 // size limits for spawning a new process with respect to the arguments
1404 // we pass on the command line.
1406 // Here we attempt to handle errors from the OS saying "your list of
1407 // arguments is too big" by reinvoking the linker again with an `@`-file
1408 // that contains all the arguments. The theory is that this is then
1409 // accepted on all linkers and the linker will read all its options out of
1410 // there instead of looking at the command line.
1411 if !cmd.very_likely_to_exceed_some_spawn_limit() {
1412 match cmd.command().stdout(Stdio::piped()).stderr(Stdio::piped()).spawn() {
1414 let output = child.wait_with_output();
1415 flush_linked_file(&output, out_filename)?;
1418 Err(ref e) if command_line_too_big(e) => {
1419 info!("command line to linker was too big: {}", e);
1421 Err(e) => return Err(e),
1425 info!("falling back to passing arguments to linker via an @-file");
1426 let mut cmd2 = cmd.clone();
1427 let mut args = String::new();
1428 for arg in cmd2.take_args() {
1430 &Escape { arg: arg.to_str().unwrap(), is_like_msvc: sess.target.is_like_msvc }
1435 let file = tmpdir.join("linker-arguments");
1436 let bytes = if sess.target.is_like_msvc {
1437 let mut out = Vec::with_capacity((1 + args.len()) * 2);
1438 // start the stream with a UTF-16 BOM
1439 for c in std::iter::once(0xFEFF).chain(args.encode_utf16()) {
1440 // encode in little endian
1442 out.push((c >> 8) as u8);
1448 fs::write(&file, &bytes)?;
1449 cmd2.arg(format!("@{}", file.display()));
1450 info!("invoking linker {:?}", cmd2);
1451 let output = cmd2.output();
1452 flush_linked_file(&output, out_filename)?;
1455 #[cfg(not(windows))]
1456 fn flush_linked_file(_: &io::Result<Output>, _: &Path) -> io::Result<()> {
1461 fn flush_linked_file(
1462 command_output: &io::Result<Output>,
1463 out_filename: &Path,
1464 ) -> io::Result<()> {
1465 // On Windows, under high I/O load, output buffers are sometimes not flushed,
1466 // even long after process exit, causing nasty, non-reproducible output bugs.
1468 // File::sync_all() calls FlushFileBuffers() down the line, which solves the problem.
1470 // А full writeup of the original Chrome bug can be found at
1471 // randomascii.wordpress.com/2018/02/25/compiler-bug-linker-bug-windows-kernel-bug/amp
1473 if let &Ok(ref out) = command_output {
1474 if out.status.success() {
1475 if let Ok(of) = fs::OpenOptions::new().write(true).open(out_filename) {
1485 fn command_line_too_big(err: &io::Error) -> bool {
1486 err.raw_os_error() == Some(::libc::E2BIG)
1490 fn command_line_too_big(err: &io::Error) -> bool {
1491 const ERROR_FILENAME_EXCED_RANGE: i32 = 206;
1492 err.raw_os_error() == Some(ERROR_FILENAME_EXCED_RANGE)
1495 #[cfg(not(any(unix, windows)))]
1496 fn command_line_too_big(_: &io::Error) -> bool {
1505 impl<'a> fmt::Display for Escape<'a> {
1506 fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
1507 if self.is_like_msvc {
1508 // This is "documented" at
1509 // https://docs.microsoft.com/en-us/cpp/build/reference/at-specify-a-linker-response-file
1511 // Unfortunately there's not a great specification of the
1512 // syntax I could find online (at least) but some local
1513 // testing showed that this seemed sufficient-ish to catch
1514 // at least a few edge cases.
1516 for c in self.arg.chars() {
1518 '"' => write!(f, "\\{}", c)?,
1519 c => write!(f, "{}", c)?,
1524 // This is documented at https://linux.die.net/man/1/ld, namely:
1526 // > Options in file are separated by whitespace. A whitespace
1527 // > character may be included in an option by surrounding the
1528 // > entire option in either single or double quotes. Any
1529 // > character (including a backslash) may be included by
1530 // > prefixing the character to be included with a backslash.
1532 // We put an argument on each line, so all we need to do is
1533 // ensure the line is interpreted as one whole argument.
1534 for c in self.arg.chars() {
1536 '\\' | ' ' => write!(f, "\\{}", c)?,
1537 c => write!(f, "{}", c)?,
1546 fn link_output_kind(sess: &Session, crate_type: CrateType) -> LinkOutputKind {
1547 let kind = match (crate_type, sess.crt_static(Some(crate_type)), sess.relocation_model()) {
1548 (CrateType::Executable, _, _) if sess.is_wasi_reactor() => LinkOutputKind::WasiReactorExe,
1549 (CrateType::Executable, false, RelocModel::Pic | RelocModel::Pie) => {
1550 LinkOutputKind::DynamicPicExe
1552 (CrateType::Executable, false, _) => LinkOutputKind::DynamicNoPicExe,
1553 (CrateType::Executable, true, RelocModel::Pic | RelocModel::Pie) => {
1554 LinkOutputKind::StaticPicExe
1556 (CrateType::Executable, true, _) => LinkOutputKind::StaticNoPicExe,
1557 (_, true, _) => LinkOutputKind::StaticDylib,
1558 (_, false, _) => LinkOutputKind::DynamicDylib,
1561 // Adjust the output kind to target capabilities.
1562 let opts = &sess.target;
1563 let pic_exe_supported = opts.position_independent_executables;
1564 let static_pic_exe_supported = opts.static_position_independent_executables;
1565 let static_dylib_supported = opts.crt_static_allows_dylibs;
1567 LinkOutputKind::DynamicPicExe if !pic_exe_supported => LinkOutputKind::DynamicNoPicExe,
1568 LinkOutputKind::StaticPicExe if !static_pic_exe_supported => LinkOutputKind::StaticNoPicExe,
1569 LinkOutputKind::StaticDylib if !static_dylib_supported => LinkOutputKind::DynamicDylib,
1574 // Returns true if linker is located within sysroot
1575 fn detect_self_contained_mingw(sess: &Session) -> bool {
1576 let (linker, _) = linker_and_flavor(&sess);
1577 // Assume `-C linker=rust-lld` as self-contained mode
1578 if linker == Path::new("rust-lld") {
1581 let linker_with_extension = if cfg!(windows) && linker.extension().is_none() {
1582 linker.with_extension("exe")
1586 for dir in env::split_paths(&env::var_os("PATH").unwrap_or_default()) {
1587 let full_path = dir.join(&linker_with_extension);
1588 // If linker comes from sysroot assume self-contained mode
1589 if full_path.is_file() && !full_path.starts_with(&sess.sysroot) {
1596 /// Various toolchain components used during linking are used from rustc distribution
1597 /// instead of being found somewhere on the host system.
1598 /// We only provide such support for a very limited number of targets.
1599 fn self_contained(sess: &Session, crate_type: CrateType) -> bool {
1600 if let Some(self_contained) = sess.opts.cg.link_self_contained {
1601 if sess.target.link_self_contained == LinkSelfContainedDefault::False {
1602 sess.emit_err(errors::UnsupportedLinkSelfContained);
1604 return self_contained;
1607 match sess.target.link_self_contained {
1608 LinkSelfContainedDefault::False => false,
1609 LinkSelfContainedDefault::True => true,
1610 // FIXME: Find a better heuristic for "native musl toolchain is available",
1611 // based on host and linker path, for example.
1612 // (https://github.com/rust-lang/rust/pull/71769#issuecomment-626330237).
1613 LinkSelfContainedDefault::Musl => sess.crt_static(Some(crate_type)),
1614 LinkSelfContainedDefault::Mingw => {
1615 sess.host == sess.target
1616 && sess.target.vendor != "uwp"
1617 && detect_self_contained_mingw(&sess)
1622 /// Add pre-link object files defined by the target spec.
1623 fn add_pre_link_objects(
1624 cmd: &mut dyn Linker,
1626 flavor: LinkerFlavor,
1627 link_output_kind: LinkOutputKind,
1628 self_contained: bool,
1630 // FIXME: we are currently missing some infra here (per-linker-flavor CRT objects),
1631 // so Fuchsia has to be special-cased.
1632 let opts = &sess.target;
1633 let empty = Default::default();
1634 let objects = if self_contained {
1635 &opts.pre_link_objects_self_contained
1636 } else if !(sess.target.os == "fuchsia" && matches!(flavor, LinkerFlavor::Gnu(Cc::Yes, _))) {
1637 &opts.pre_link_objects
1641 for obj in objects.get(&link_output_kind).iter().copied().flatten() {
1642 cmd.add_object(&get_object_file_path(sess, obj, self_contained));
1646 /// Add post-link object files defined by the target spec.
1647 fn add_post_link_objects(
1648 cmd: &mut dyn Linker,
1650 link_output_kind: LinkOutputKind,
1651 self_contained: bool,
1653 let objects = if self_contained {
1654 &sess.target.post_link_objects_self_contained
1656 &sess.target.post_link_objects
1658 for obj in objects.get(&link_output_kind).iter().copied().flatten() {
1659 cmd.add_object(&get_object_file_path(sess, obj, self_contained));
1663 /// Add arbitrary "pre-link" args defined by the target spec or from command line.
1664 /// FIXME: Determine where exactly these args need to be inserted.
1665 fn add_pre_link_args(cmd: &mut dyn Linker, sess: &Session, flavor: LinkerFlavor) {
1666 if let Some(args) = sess.target.pre_link_args.get(&flavor) {
1667 cmd.args(args.iter().map(Deref::deref));
1669 cmd.args(&sess.opts.unstable_opts.pre_link_args);
1672 /// Add a link script embedded in the target, if applicable.
1673 fn add_link_script(cmd: &mut dyn Linker, sess: &Session, tmpdir: &Path, crate_type: CrateType) {
1674 match (crate_type, &sess.target.link_script) {
1675 (CrateType::Cdylib | CrateType::Executable, Some(script)) => {
1676 if !sess.target.linker_flavor.is_gnu() {
1677 sess.emit_fatal(errors::LinkScriptUnavailable);
1680 let file_name = ["rustc", &sess.target.llvm_target, "linkfile.ld"].join("-");
1682 let path = tmpdir.join(file_name);
1683 if let Err(error) = fs::write(&path, script.as_ref()) {
1684 sess.emit_fatal(errors::LinkScriptWriteFailure { path, error });
1687 cmd.arg("--script");
1694 /// Add arbitrary "user defined" args defined from command line.
1695 /// FIXME: Determine where exactly these args need to be inserted.
1696 fn add_user_defined_link_args(cmd: &mut dyn Linker, sess: &Session) {
1697 cmd.args(&sess.opts.cg.link_args);
1700 /// Add arbitrary "late link" args defined by the target spec.
1701 /// FIXME: Determine where exactly these args need to be inserted.
1702 fn add_late_link_args(
1703 cmd: &mut dyn Linker,
1705 flavor: LinkerFlavor,
1706 crate_type: CrateType,
1707 codegen_results: &CodegenResults,
1709 let any_dynamic_crate = crate_type == CrateType::Dylib
1710 || codegen_results.crate_info.dependency_formats.iter().any(|(ty, list)| {
1711 *ty == crate_type && list.iter().any(|&linkage| linkage == Linkage::Dynamic)
1713 if any_dynamic_crate {
1714 if let Some(args) = sess.target.late_link_args_dynamic.get(&flavor) {
1715 cmd.args(args.iter().map(Deref::deref));
1718 if let Some(args) = sess.target.late_link_args_static.get(&flavor) {
1719 cmd.args(args.iter().map(Deref::deref));
1722 if let Some(args) = sess.target.late_link_args.get(&flavor) {
1723 cmd.args(args.iter().map(Deref::deref));
1727 /// Add arbitrary "post-link" args defined by the target spec.
1728 /// FIXME: Determine where exactly these args need to be inserted.
1729 fn add_post_link_args(cmd: &mut dyn Linker, sess: &Session, flavor: LinkerFlavor) {
1730 if let Some(args) = sess.target.post_link_args.get(&flavor) {
1731 cmd.args(args.iter().map(Deref::deref));
1735 /// Add a synthetic object file that contains reference to all symbols that we want to expose to
1738 /// Background: we implement rlibs as static library (archives). Linkers treat archives
1739 /// differently from object files: all object files participate in linking, while archives will
1740 /// only participate in linking if they can satisfy at least one undefined reference (version
1741 /// scripts doesn't count). This causes `#[no_mangle]` or `#[used]` items to be ignored by the
1742 /// linker, and since they never participate in the linking, using `KEEP` in the linker scripts
1743 /// can't keep them either. This causes #47384.
1745 /// To keep them around, we could use `--whole-archive` and equivalents to force rlib to
1746 /// participate in linking like object files, but this proves to be expensive (#93791). Therefore
1747 /// we instead just introduce an undefined reference to them. This could be done by `-u` command
1748 /// line option to the linker or `EXTERN(...)` in linker scripts, however they does not only
1749 /// introduce an undefined reference, but also make them the GC roots, preventing `--gc-sections`
1750 /// from removing them, and this is especially problematic for embedded programming where every
1753 /// This method creates a synthetic object file, which contains undefined references to all symbols
1754 /// that are necessary for the linking. They are only present in symbol table but not actually
1755 /// used in any sections, so the linker will therefore pick relevant rlibs for linking, but
1756 /// unused `#[no_mangle]` or `#[used]` can still be discard by GC sections.
1758 /// There's a few internal crates in the standard library (aka libcore and
1759 /// libstd) which actually have a circular dependence upon one another. This
1760 /// currently arises through "weak lang items" where libcore requires things
1761 /// like `rust_begin_unwind` but libstd ends up defining it. To get this
1762 /// circular dependence to work correctly we declare some of these things
1763 /// in this synthetic object.
1764 fn add_linked_symbol_object(
1765 cmd: &mut dyn Linker,
1768 symbols: &[(String, SymbolExportKind)],
1770 if symbols.is_empty() {
1774 let Some(mut file) = super::metadata::create_object_file(sess) else {
1778 // NOTE(nbdd0121): MSVC will hang if the input object file contains no sections,
1779 // so add an empty section.
1780 if file.format() == object::BinaryFormat::Coff {
1781 file.add_section(Vec::new(), ".text".into(), object::SectionKind::Text);
1783 // We handle the name decoration of COFF targets in `symbol_export.rs`, so disable the
1784 // default mangler in `object` crate.
1785 file.set_mangling(object::write::Mangling::None);
1787 // Add feature flags to the object file. On MSVC this is optional but LLD will complain if
1789 let mut feature = 0;
1791 if file.architecture() == object::Architecture::I386 {
1792 // Indicate that all SEH handlers are registered in .sxdata section.
1793 // We don't have generate any code, so we don't need .sxdata section but LLD still
1794 // expects us to set this bit (see #96498).
1795 // Reference: https://docs.microsoft.com/en-us/windows/win32/debug/pe-format
1799 file.add_symbol(object::write::Symbol {
1800 name: "@feat.00".into(),
1803 kind: object::SymbolKind::Data,
1804 scope: object::SymbolScope::Compilation,
1806 section: object::write::SymbolSection::Absolute,
1807 flags: object::SymbolFlags::None,
1811 for (sym, kind) in symbols.iter() {
1812 file.add_symbol(object::write::Symbol {
1813 name: sym.clone().into(),
1817 SymbolExportKind::Text => object::SymbolKind::Text,
1818 SymbolExportKind::Data => object::SymbolKind::Data,
1819 SymbolExportKind::Tls => object::SymbolKind::Tls,
1821 scope: object::SymbolScope::Unknown,
1823 section: object::write::SymbolSection::Undefined,
1824 flags: object::SymbolFlags::None,
1828 let path = tmpdir.join("symbols.o");
1829 let result = std::fs::write(&path, file.write().unwrap());
1830 if let Err(error) = result {
1831 sess.emit_fatal(errors::FailedToWrite { path, error });
1833 cmd.add_object(&path);
1836 /// Add object files containing code from the current crate.
1837 fn add_local_crate_regular_objects(cmd: &mut dyn Linker, codegen_results: &CodegenResults) {
1838 for obj in codegen_results.modules.iter().filter_map(|m| m.object.as_ref()) {
1839 cmd.add_object(obj);
1843 /// Add object files for allocator code linked once for the whole crate tree.
1844 fn add_local_crate_allocator_objects(cmd: &mut dyn Linker, codegen_results: &CodegenResults) {
1845 if let Some(obj) = codegen_results.allocator_module.as_ref().and_then(|m| m.object.as_ref()) {
1846 cmd.add_object(obj);
1850 /// Add object files containing metadata for the current crate.
1851 fn add_local_crate_metadata_objects(
1852 cmd: &mut dyn Linker,
1853 crate_type: CrateType,
1854 codegen_results: &CodegenResults,
1856 // When linking a dynamic library, we put the metadata into a section of the
1857 // executable. This metadata is in a separate object file from the main
1858 // object file, so we link that in here.
1859 if crate_type == CrateType::Dylib || crate_type == CrateType::ProcMacro {
1860 if let Some(obj) = codegen_results.metadata_module.as_ref().and_then(|m| m.object.as_ref())
1862 cmd.add_object(obj);
1867 /// Add sysroot and other globally set directories to the directory search list.
1868 fn add_library_search_dirs(cmd: &mut dyn Linker, sess: &Session, self_contained: bool) {
1869 // The default library location, we need this to find the runtime.
1870 // The location of crates will be determined as needed.
1871 let lib_path = sess.target_filesearch(PathKind::All).get_lib_path();
1872 cmd.include_path(&fix_windows_verbatim_for_gcc(&lib_path));
1874 // Special directory with libraries used only in self-contained linkage mode
1876 let lib_path = sess.target_filesearch(PathKind::All).get_self_contained_lib_path();
1877 cmd.include_path(&fix_windows_verbatim_for_gcc(&lib_path));
1881 /// Add options making relocation sections in the produced ELF files read-only
1882 /// and suppressing lazy binding.
1883 fn add_relro_args(cmd: &mut dyn Linker, sess: &Session) {
1884 match sess.opts.unstable_opts.relro_level.unwrap_or(sess.target.relro_level) {
1885 RelroLevel::Full => cmd.full_relro(),
1886 RelroLevel::Partial => cmd.partial_relro(),
1887 RelroLevel::Off => cmd.no_relro(),
1888 RelroLevel::None => {}
1892 /// Add library search paths used at runtime by dynamic linkers.
1894 cmd: &mut dyn Linker,
1896 codegen_results: &CodegenResults,
1897 out_filename: &Path,
1899 // FIXME (#2397): At some point we want to rpath our guesses as to
1900 // where extern libraries might live, based on the
1901 // add_lib_search_paths
1902 if sess.opts.cg.rpath {
1903 let libs = codegen_results
1907 .filter_map(|cnum| {
1908 codegen_results.crate_info.used_crate_source[cnum]
1911 .map(|(path, _)| &**path)
1913 .collect::<Vec<_>>();
1914 let mut rpath_config = RPathConfig {
1916 out_filename: out_filename.to_path_buf(),
1917 has_rpath: sess.target.has_rpath,
1918 is_like_osx: sess.target.is_like_osx,
1919 linker_is_gnu: sess.target.linker_flavor.is_gnu(),
1921 cmd.args(&rpath::get_rpath_flags(&mut rpath_config));
1925 /// Produce the linker command line containing linker path and arguments.
1927 /// When comments in the function say "order-(in)dependent" they mean order-dependence between
1928 /// options and libraries/object files. For example `--whole-archive` (order-dependent) applies
1929 /// to specific libraries passed after it, and `-o` (output file, order-independent) applies
1930 /// to the linking process as a whole.
1931 /// Order-independent options may still override each other in order-dependent fashion,
1932 /// e.g `--foo=yes --foo=no` may be equivalent to `--foo=no`.
1933 fn linker_with_args<'a>(
1935 flavor: LinkerFlavor,
1937 archive_builder_builder: &dyn ArchiveBuilderBuilder,
1938 crate_type: CrateType,
1940 out_filename: &Path,
1941 codegen_results: &CodegenResults,
1942 ) -> Result<Command, ErrorGuaranteed> {
1943 let self_contained = self_contained(sess, crate_type);
1944 let cmd = &mut *super::linker::get_linker(
1949 &codegen_results.crate_info.target_cpu,
1951 let link_output_kind = link_output_kind(sess, crate_type);
1953 // ------------ Early order-dependent options ------------
1955 // If we're building something like a dynamic library then some platforms
1956 // need to make sure that all symbols are exported correctly from the
1958 // Must be passed before any libraries to prevent the symbols to export from being thrown away,
1959 // at least on some platforms (e.g. windows-gnu).
1963 &codegen_results.crate_info.exported_symbols[&crate_type],
1966 // Can be used for adding custom CRT objects or overriding order-dependent options above.
1967 // FIXME: In practice built-in target specs use this for arbitrary order-independent options,
1968 // introduce a target spec option for order-independent linker options and migrate built-in
1970 add_pre_link_args(cmd, sess, flavor);
1972 // ------------ Object code and libraries, order-dependent ------------
1974 // Pre-link CRT objects.
1975 add_pre_link_objects(cmd, sess, flavor, link_output_kind, self_contained);
1977 add_linked_symbol_object(
1981 &codegen_results.crate_info.linked_symbols[&crate_type],
1984 // Sanitizer libraries.
1985 add_sanitizer_libraries(sess, crate_type, cmd);
1987 // Object code from the current crate.
1988 // Take careful note of the ordering of the arguments we pass to the linker
1989 // here. Linkers will assume that things on the left depend on things to the
1990 // right. Things on the right cannot depend on things on the left. This is
1991 // all formally implemented in terms of resolving symbols (libs on the right
1992 // resolve unknown symbols of libs on the left, but not vice versa).
1994 // For this reason, we have organized the arguments we pass to the linker as
1997 // 1. The local object that LLVM just generated
1998 // 2. Local native libraries
1999 // 3. Upstream rust libraries
2000 // 4. Upstream native libraries
2002 // The rationale behind this ordering is that those items lower down in the
2003 // list can't depend on items higher up in the list. For example nothing can
2004 // depend on what we just generated (e.g., that'd be a circular dependency).
2005 // Upstream rust libraries are not supposed to depend on our local native
2006 // libraries as that would violate the structure of the DAG, in that
2007 // scenario they are required to link to them as well in a shared fashion.
2009 // Note that upstream rust libraries may contain native dependencies as
2010 // well, but they also can't depend on what we just started to add to the
2011 // link line. And finally upstream native libraries can't depend on anything
2012 // in this DAG so far because they can only depend on other native libraries
2013 // and such dependencies are also required to be specified.
2014 add_local_crate_regular_objects(cmd, codegen_results);
2015 add_local_crate_metadata_objects(cmd, crate_type, codegen_results);
2016 add_local_crate_allocator_objects(cmd, codegen_results);
2018 // Avoid linking to dynamic libraries unless they satisfy some undefined symbols
2019 // at the point at which they are specified on the command line.
2020 // Must be passed before any (dynamic) libraries to have effect on them.
2021 // On Solaris-like systems, `-z ignore` acts as both `--as-needed` and `--gc-sections`
2022 // so it will ignore unreferenced ELF sections from relocatable objects.
2023 // For that reason, we put this flag after metadata objects as they would otherwise be removed.
2024 // FIXME: Support more fine-grained dead code removal on Solaris/illumos
2025 // and move this option back to the top.
2026 cmd.add_as_needed();
2028 // Local native libraries of all kinds.
2029 add_local_native_libraries(cmd, sess, archive_builder_builder, codegen_results, tmpdir);
2031 // Upstream rust crates and their non-dynamic native libraries.
2032 add_upstream_rust_crates(
2035 archive_builder_builder,
2041 // Dynamic native libraries from upstream crates.
2042 add_upstream_native_libraries(cmd, sess, archive_builder_builder, codegen_results, tmpdir);
2044 // Link with the import library generated for any raw-dylib functions.
2045 for (raw_dylib_name, raw_dylib_imports) in
2046 collate_raw_dylibs(sess, codegen_results.crate_info.used_libraries.iter())?
2048 cmd.add_object(&archive_builder_builder.create_dll_import_lib(
2056 // As with add_upstream_native_libraries, we need to add the upstream raw-dylib symbols in case
2057 // they are used within inlined functions or instantiated generic functions. We do this *after*
2058 // handling the raw-dylib symbols in the current crate to make sure that those are chosen first
2060 let (_, dependency_linkage) = codegen_results
2064 .find(|(ty, _)| *ty == crate_type)
2065 .expect("failed to find crate type in dependency format list");
2066 let native_libraries_from_nonstatics = codegen_results
2070 .filter_map(|(cnum, libraries)| {
2071 (dependency_linkage[cnum.as_usize() - 1] != Linkage::Static).then(|| libraries)
2074 for (raw_dylib_name, raw_dylib_imports) in
2075 collate_raw_dylibs(sess, native_libraries_from_nonstatics)?
2077 cmd.add_object(&archive_builder_builder.create_dll_import_lib(
2086 // Library linking above uses some global state for things like `-Bstatic`/`-Bdynamic` to make
2087 // command line shorter, reset it to default here before adding more libraries.
2088 cmd.reset_per_library_state();
2090 // FIXME: Built-in target specs occasionally use this for linking system libraries,
2091 // eliminate all such uses by migrating them to `#[link]` attributes in `lib(std,c,unwind)`
2092 // and remove the option.
2093 add_late_link_args(cmd, sess, flavor, crate_type, codegen_results);
2095 // ------------ Arbitrary order-independent options ------------
2097 // Add order-independent options determined by rustc from its compiler options,
2098 // target properties and source code.
2099 add_order_independent_options(
2111 // Can be used for arbitrary order-independent options.
2112 // In practice may also be occasionally used for linking native libraries.
2113 // Passed after compiler-generated options to support manual overriding when necessary.
2114 add_user_defined_link_args(cmd, sess);
2116 // ------------ Object code and libraries, order-dependent ------------
2118 // Post-link CRT objects.
2119 add_post_link_objects(cmd, sess, link_output_kind, self_contained);
2121 // ------------ Late order-dependent options ------------
2123 // Doesn't really make sense.
2124 // FIXME: In practice built-in target specs use this for arbitrary order-independent options,
2125 // introduce a target spec option for order-independent linker options, migrate built-in specs
2126 // to it and remove the option.
2127 add_post_link_args(cmd, sess, flavor);
2132 fn add_order_independent_options(
2133 cmd: &mut dyn Linker,
2135 link_output_kind: LinkOutputKind,
2136 self_contained: bool,
2137 flavor: LinkerFlavor,
2138 crate_type: CrateType,
2139 codegen_results: &CodegenResults,
2140 out_filename: &Path,
2143 add_gcc_ld_path(cmd, sess, flavor);
2145 add_apple_sdk(cmd, sess, flavor);
2147 add_link_script(cmd, sess, tmpdir, crate_type);
2149 if sess.target.os == "fuchsia"
2150 && crate_type == CrateType::Executable
2151 && !matches!(flavor, LinkerFlavor::Gnu(Cc::Yes, _))
2153 let prefix = if sess.opts.unstable_opts.sanitizer.contains(SanitizerSet::ADDRESS) {
2158 cmd.arg(format!("--dynamic-linker={}ld.so.1", prefix));
2161 if sess.target.eh_frame_header {
2162 cmd.add_eh_frame_header();
2165 // Make the binary compatible with data execution prevention schemes.
2169 cmd.no_crt_objects();
2172 if sess.target.os == "emscripten" {
2174 cmd.arg(if sess.panic_strategy() == PanicStrategy::Abort {
2175 "DISABLE_EXCEPTION_CATCHING=1"
2177 "DISABLE_EXCEPTION_CATCHING=0"
2181 if flavor == LinkerFlavor::Ptx {
2182 // Provide the linker with fallback to internal `target-cpu`.
2183 cmd.arg("--fallback-arch");
2184 cmd.arg(&codegen_results.crate_info.target_cpu);
2185 } else if flavor == LinkerFlavor::Bpf {
2187 cmd.arg(&codegen_results.crate_info.target_cpu);
2188 cmd.arg("--cpu-features");
2189 cmd.arg(match &sess.opts.cg.target_feature {
2190 feat if !feat.is_empty() => feat.as_ref(),
2191 _ => sess.target.options.features.as_ref(),
2195 cmd.linker_plugin_lto();
2197 add_library_search_dirs(cmd, sess, self_contained);
2199 cmd.output_filename(out_filename);
2201 if crate_type == CrateType::Executable && sess.target.is_like_windows {
2202 if let Some(ref s) = codegen_results.crate_info.windows_subsystem {
2207 // Try to strip as much out of the generated object by removing unused
2208 // sections if possible. See more comments in linker.rs
2209 if !sess.link_dead_code() {
2210 // If PGO is enabled sometimes gc_sections will remove the profile data section
2211 // as it appears to be unused. This can then cause the PGO profile file to lose
2212 // some functions. If we are generating a profile we shouldn't strip those metadata
2213 // sections to ensure we have all the data for PGO.
2215 crate_type == CrateType::Dylib || sess.opts.cg.profile_generate.enabled();
2216 if crate_type != CrateType::Executable || !sess.opts.unstable_opts.export_executable_symbols
2218 cmd.gc_sections(keep_metadata);
2220 cmd.no_gc_sections();
2224 cmd.set_output_kind(link_output_kind, out_filename);
2226 add_relro_args(cmd, sess);
2228 // Pass optimization flags down to the linker.
2231 // Gather the set of NatVis files, if any, and write them out to a temp directory.
2232 let natvis_visualizers = collect_natvis_visualizers(
2235 &codegen_results.crate_info.local_crate_name,
2236 &codegen_results.crate_info.natvis_debugger_visualizers,
2239 // Pass debuginfo, NatVis debugger visualizers and strip flags down to the linker.
2240 cmd.debuginfo(strip_value(sess), &natvis_visualizers);
2242 // We want to prevent the compiler from accidentally leaking in any system libraries,
2243 // so by default we tell linkers not to link to any default libraries.
2244 if !sess.opts.cg.default_linker_libraries && sess.target.no_default_libraries {
2245 cmd.no_default_libraries();
2248 if sess.opts.cg.profile_generate.enabled() || sess.instrument_coverage() {
2252 if sess.opts.cg.control_flow_guard != CFGuard::Disabled {
2253 cmd.control_flow_guard();
2256 add_rpath_args(cmd, sess, codegen_results, out_filename);
2259 // Write the NatVis debugger visualizer files for each crate to the temp directory and gather the file paths.
2260 fn collect_natvis_visualizers(
2263 crate_name: &Symbol,
2264 natvis_debugger_visualizers: &BTreeSet<DebuggerVisualizerFile>,
2266 let mut visualizer_paths = Vec::with_capacity(natvis_debugger_visualizers.len());
2268 for (index, visualizer) in natvis_debugger_visualizers.iter().enumerate() {
2269 let visualizer_out_file = tmpdir.join(format!("{}-{}.natvis", crate_name.as_str(), index));
2271 match fs::write(&visualizer_out_file, &visualizer.src) {
2273 visualizer_paths.push(visualizer_out_file);
2276 sess.emit_warning(errors::UnableToWriteDebuggerVisualizer {
2277 path: visualizer_out_file,
2286 fn add_native_libs_from_crate(
2287 cmd: &mut dyn Linker,
2289 archive_builder_builder: &dyn ArchiveBuilderBuilder,
2290 codegen_results: &CodegenResults,
2292 search_paths: &OnceCell<Vec<PathBuf>>,
2293 bundled_libs: &FxHashSet<Symbol>,
2298 if !sess.opts.unstable_opts.link_native_libraries {
2299 // If `-Zlink-native-libraries=false` is set, then the assumption is that an
2300 // external build system already has the native dependencies defined, and it
2301 // will provide them to the linker itself.
2305 if link_static && cnum != LOCAL_CRATE && !bundled_libs.is_empty() {
2306 // If rlib contains native libs as archives, unpack them to tmpdir.
2307 let rlib = &codegen_results.crate_info.used_crate_source[&cnum].rlib.as_ref().unwrap().0;
2308 archive_builder_builder
2309 .extract_bundled_libs(rlib, tmpdir, &bundled_libs)
2310 .unwrap_or_else(|e| sess.emit_fatal(e));
2313 let native_libs = match cnum {
2314 LOCAL_CRATE => &codegen_results.crate_info.used_libraries,
2315 _ => &codegen_results.crate_info.native_libraries[&cnum],
2318 let mut last = (None, NativeLibKind::Unspecified, false);
2319 for lib in native_libs {
2320 let Some(name) = lib.name else {
2323 if !relevant_lib(sess, lib) {
2327 // Skip if this library is the same as the last.
2328 last = if (lib.name, lib.kind, lib.verbatim) == last {
2331 (lib.name, lib.kind, lib.verbatim)
2334 let name = name.as_str();
2335 let verbatim = lib.verbatim;
2337 NativeLibKind::Static { bundle, whole_archive } => {
2339 let bundle = bundle.unwrap_or(true);
2340 let whole_archive = whole_archive == Some(true)
2341 // Backward compatibility case: this can be a rlib (so `+whole-archive`
2342 // cannot be added explicitly if necessary, see the error in `fn link_rlib`)
2343 // compiled as an executable due to `--test`. Use whole-archive implicitly,
2344 // like before the introduction of native lib modifiers.
2345 || (whole_archive == None
2347 && cnum == LOCAL_CRATE
2350 if bundle && cnum != LOCAL_CRATE {
2351 if let Some(filename) = lib.filename {
2352 // If rlib contains native libs as archives, they are unpacked to tmpdir.
2353 let path = tmpdir.join(filename.as_str());
2355 cmd.link_whole_rlib(&path);
2357 cmd.link_rlib(&path);
2362 cmd.link_whole_staticlib(
2365 &search_paths.get_or_init(|| archive_search_paths(sess)),
2368 cmd.link_staticlib(name, verbatim)
2373 NativeLibKind::Dylib { as_needed } => {
2375 cmd.link_dylib(name, verbatim, as_needed.unwrap_or(true))
2378 NativeLibKind::Unspecified => {
2380 cmd.link_dylib(name, verbatim, true);
2383 NativeLibKind::Framework { as_needed } => {
2385 cmd.link_framework(name, as_needed.unwrap_or(true))
2388 NativeLibKind::RawDylib => {
2389 // Handled separately in `linker_with_args`.
2391 NativeLibKind::LinkArg => {
2400 fn add_local_native_libraries(
2401 cmd: &mut dyn Linker,
2403 archive_builder_builder: &dyn ArchiveBuilderBuilder,
2404 codegen_results: &CodegenResults,
2407 if sess.opts.unstable_opts.link_native_libraries {
2408 // User-supplied library search paths (-L on the command line). These are the same paths
2409 // used to find Rust crates, so some of them may have been added already by the previous
2410 // crate linking code. This only allows them to be found at compile time so it is still
2411 // entirely up to outside forces to make sure that library can be found at runtime.
2412 for search_path in sess.target_filesearch(PathKind::All).search_paths() {
2413 match search_path.kind {
2414 PathKind::Framework => cmd.framework_path(&search_path.dir),
2415 _ => cmd.include_path(&fix_windows_verbatim_for_gcc(&search_path.dir)),
2420 let search_paths = OnceCell::new();
2421 // All static and dynamic native library dependencies are linked to the local crate.
2422 let link_static = true;
2423 let link_dynamic = true;
2424 add_native_libs_from_crate(
2427 archive_builder_builder,
2431 &Default::default(),
2438 fn add_upstream_rust_crates<'a>(
2439 cmd: &mut dyn Linker,
2441 archive_builder_builder: &dyn ArchiveBuilderBuilder,
2442 codegen_results: &CodegenResults,
2443 crate_type: CrateType,
2446 // All of the heavy lifting has previously been accomplished by the
2447 // dependency_format module of the compiler. This is just crawling the
2448 // output of that module, adding crates as necessary.
2450 // Linking to a rlib involves just passing it to the linker (the linker
2451 // will slurp up the object files inside), and linking to a dynamic library
2452 // involves just passing the right -l flag.
2453 let (_, data) = codegen_results
2457 .find(|(ty, _)| *ty == crate_type)
2458 .expect("failed to find crate type in dependency format list");
2460 let search_paths = OnceCell::new();
2461 for &cnum in &codegen_results.crate_info.used_crates {
2462 // We may not pass all crates through to the linker. Some crates may appear statically in
2463 // an existing dylib, meaning we'll pick up all the symbols from the dylib.
2464 // We must always link crates `compiler_builtins` and `profiler_builtins` statically.
2465 // Even if they were already included into a dylib
2466 // (e.g. `libstd` when `-C prefer-dynamic` is used).
2467 // FIXME: `dependency_formats` can report `profiler_builtins` as `NotLinked` for some
2468 // reason, it shouldn't do that because `profiler_builtins` should indeed be linked.
2469 let linkage = data[cnum.as_usize() - 1];
2470 let link_static_crate = linkage == Linkage::Static
2471 || (linkage == Linkage::IncludedFromDylib || linkage == Linkage::NotLinked)
2472 && (codegen_results.crate_info.compiler_builtins == Some(cnum)
2473 || codegen_results.crate_info.profiler_runtime == Some(cnum));
2475 let mut bundled_libs = Default::default();
2477 Linkage::Static | Linkage::IncludedFromDylib | Linkage::NotLinked => {
2478 if link_static_crate {
2479 bundled_libs = codegen_results.crate_info.native_libraries[&cnum]
2481 .filter_map(|lib| lib.filename)
2486 archive_builder_builder,
2494 Linkage::Dynamic => {
2495 let src = &codegen_results.crate_info.used_crate_source[&cnum];
2496 add_dynamic_crate(cmd, sess, &src.dylib.as_ref().unwrap().0);
2500 // Static libraries are linked for a subset of linked upstream crates.
2501 // 1. If the upstream crate is a directly linked rlib then we must link the native library
2502 // because the rlib is just an archive.
2503 // 2. If the upstream crate is a dylib or a rlib linked through dylib, then we do not link
2504 // the native library because it is already linked into the dylib, and even if
2505 // inline/const/generic functions from the dylib can refer to symbols from the native
2506 // library, those symbols should be exported and available from the dylib anyway.
2507 // 3. Libraries bundled into `(compiler,profiler)_builtins` are special, see above.
2508 let link_static = link_static_crate;
2509 // Dynamic libraries are not linked here, see the FIXME in `add_upstream_native_libraries`.
2510 let link_dynamic = false;
2511 add_native_libs_from_crate(
2514 archive_builder_builder,
2526 fn add_upstream_native_libraries(
2527 cmd: &mut dyn Linker,
2529 archive_builder_builder: &dyn ArchiveBuilderBuilder,
2530 codegen_results: &CodegenResults,
2533 let search_path = OnceCell::new();
2534 for &cnum in &codegen_results.crate_info.used_crates {
2535 // Static libraries are not linked here, they are linked in `add_upstream_rust_crates`.
2536 // FIXME: Merge this function to `add_upstream_rust_crates` so that all native libraries
2537 // are linked together with their respective upstream crates, and in their originally
2538 // specified order. This is slightly breaking due to our use of `--as-needed` (see crater
2539 // results in https://github.com/rust-lang/rust/pull/102832#issuecomment-1279772306).
2540 let link_static = false;
2541 // Dynamic libraries are linked for all linked upstream crates.
2542 // 1. If the upstream crate is a directly linked rlib then we must link the native library
2543 // because the rlib is just an archive.
2544 // 2. If the upstream crate is a dylib or a rlib linked through dylib, then we have to link
2545 // the native library too because inline/const/generic functions from the dylib can refer
2546 // to symbols from the native library, so the native library providing those symbols should
2547 // be available when linking our final binary.
2548 let link_dynamic = true;
2549 add_native_libs_from_crate(
2552 archive_builder_builder,
2556 &Default::default(),
2564 // Adds the static "rlib" versions of all crates to the command line.
2565 // There's a bit of magic which happens here specifically related to LTO,
2566 // namely that we remove upstream object files.
2568 // When performing LTO, almost(*) all of the bytecode from the upstream
2569 // libraries has already been included in our object file output. As a
2570 // result we need to remove the object files in the upstream libraries so
2571 // the linker doesn't try to include them twice (or whine about duplicate
2572 // symbols). We must continue to include the rest of the rlib, however, as
2573 // it may contain static native libraries which must be linked in.
2575 // (*) Crates marked with `#![no_builtins]` don't participate in LTO and
2576 // their bytecode wasn't included. The object files in those libraries must
2577 // still be passed to the linker.
2579 // Note, however, that if we're not doing LTO we can just pass the rlib
2580 // blindly to the linker (fast) because it's fine if it's not actually
2581 // included as we're at the end of the dependency chain.
2582 fn add_static_crate<'a>(
2583 cmd: &mut dyn Linker,
2585 archive_builder_builder: &dyn ArchiveBuilderBuilder,
2586 codegen_results: &CodegenResults,
2589 bundled_lib_file_names: &FxHashSet<Symbol>,
2591 let src = &codegen_results.crate_info.used_crate_source[&cnum];
2592 let cratepath = &src.rlib.as_ref().unwrap().0;
2594 let mut link_upstream = |path: &Path| {
2595 cmd.link_rlib(&fix_windows_verbatim_for_gcc(path));
2598 // See the comment above in `link_staticlib` and `link_rlib` for why if
2599 // there's a static library that's not relevant we skip all object
2601 let native_libs = &codegen_results.crate_info.native_libraries[&cnum];
2602 let skip_native = native_libs.iter().any(|lib| {
2603 matches!(lib.kind, NativeLibKind::Static { bundle: None | Some(true), .. })
2604 && !relevant_lib(sess, lib)
2607 if (!are_upstream_rust_objects_already_included(sess)
2608 || ignored_for_lto(sess, &codegen_results.crate_info, cnum))
2611 link_upstream(cratepath);
2615 let dst = tmpdir.join(cratepath.file_name().unwrap());
2616 let name = cratepath.file_name().unwrap().to_str().unwrap();
2617 let name = &name[3..name.len() - 5]; // chop off lib/.rlib
2618 let bundled_lib_file_names = bundled_lib_file_names.clone();
2620 sess.prof.generic_activity_with_arg("link_altering_rlib", name).run(|| {
2621 let canonical_name = name.replace('-', "_");
2622 let upstream_rust_objects_already_included =
2623 are_upstream_rust_objects_already_included(sess);
2625 sess.target.no_builtins || !codegen_results.crate_info.is_no_builtins.contains(&cnum);
2627 let mut archive = archive_builder_builder.new_archive_builder(sess);
2628 if let Err(error) = archive.add_archive(
2631 if f == METADATA_FILENAME {
2635 let canonical = f.replace('-', "_");
2637 let is_rust_object =
2638 canonical.starts_with(&canonical_name) && looks_like_rust_object_file(&f);
2640 // If we've been requested to skip all native object files
2641 // (those not generated by the rust compiler) then we can skip
2642 // this file. See above for why we may want to do this.
2643 let skip_because_cfg_say_so = skip_native && !is_rust_object;
2645 // If we're performing LTO and this is a rust-generated object
2646 // file, then we don't need the object file as it's part of the
2647 // LTO module. Note that `#![no_builtins]` is excluded from LTO,
2648 // though, so we let that object file slide.
2649 let skip_because_lto =
2650 upstream_rust_objects_already_included && is_rust_object && is_builtins;
2652 // We skip native libraries because:
2653 // 1. This native libraries won't be used from the generated rlib,
2654 // so we can throw them away to avoid the copying work.
2655 // 2. We can't allow it to be a single remaining entry in archive
2656 // as some linkers may complain on that.
2657 if bundled_lib_file_names.contains(&Symbol::intern(f)) {
2661 if skip_because_cfg_say_so || skip_because_lto {
2668 sess.emit_fatal(errors::RlibArchiveBuildFailure { error });
2670 if archive.build(&dst) {
2671 link_upstream(&dst);
2676 // Same thing as above, but for dynamic crates instead of static crates.
2677 fn add_dynamic_crate(cmd: &mut dyn Linker, sess: &Session, cratepath: &Path) {
2678 // Just need to tell the linker about where the library lives and
2680 let parent = cratepath.parent();
2681 if let Some(dir) = parent {
2682 cmd.include_path(&fix_windows_verbatim_for_gcc(dir));
2684 let stem = cratepath.file_stem().unwrap().to_str().unwrap();
2685 // Convert library file-stem into a cc -l argument.
2686 let prefix = if stem.starts_with("lib") && !sess.target.is_like_windows { 3 } else { 0 };
2687 cmd.link_rust_dylib(&stem[prefix..], parent.unwrap_or_else(|| Path::new("")));
2690 fn relevant_lib(sess: &Session, lib: &NativeLib) -> bool {
2692 Some(ref cfg) => rustc_attr::cfg_matches(cfg, &sess.parse_sess, CRATE_NODE_ID, None),
2697 pub(crate) fn are_upstream_rust_objects_already_included(sess: &Session) -> bool {
2699 config::Lto::Fat => true,
2700 config::Lto::Thin => {
2701 // If we defer LTO to the linker, we haven't run LTO ourselves, so
2702 // any upstream object files have not been copied yet.
2703 !sess.opts.cg.linker_plugin_lto.enabled()
2705 config::Lto::No | config::Lto::ThinLocal => false,
2709 fn add_apple_sdk(cmd: &mut dyn Linker, sess: &Session, flavor: LinkerFlavor) {
2710 let arch = &sess.target.arch;
2711 let os = &sess.target.os;
2712 let llvm_target = &sess.target.llvm_target;
2713 if sess.target.vendor != "apple"
2714 || !matches!(os.as_ref(), "ios" | "tvos" | "watchos" | "macos")
2715 || !matches!(flavor, LinkerFlavor::Darwin(..))
2720 if os == "macos" && !matches!(flavor, LinkerFlavor::Darwin(Cc::No, _)) {
2724 let sdk_name = match (arch.as_ref(), os.as_ref()) {
2725 ("aarch64", "tvos") => "appletvos",
2726 ("x86_64", "tvos") => "appletvsimulator",
2727 ("arm", "ios") => "iphoneos",
2728 ("aarch64", "ios") if llvm_target.contains("macabi") => "macosx",
2729 ("aarch64", "ios") if llvm_target.ends_with("-simulator") => "iphonesimulator",
2730 ("aarch64", "ios") => "iphoneos",
2731 ("x86", "ios") => "iphonesimulator",
2732 ("x86_64", "ios") if llvm_target.contains("macabi") => "macosx",
2733 ("x86_64", "ios") => "iphonesimulator",
2734 ("x86_64", "watchos") => "watchsimulator",
2735 ("arm64_32", "watchos") => "watchos",
2736 ("aarch64", "watchos") if llvm_target.ends_with("-simulator") => "watchsimulator",
2737 ("aarch64", "watchos") => "watchos",
2738 ("arm", "watchos") => "watchos",
2739 (_, "macos") => "macosx",
2741 sess.emit_err(errors::UnsupportedArch { arch, os });
2745 let sdk_root = match get_apple_sdk_root(sdk_name) {
2754 LinkerFlavor::Darwin(Cc::Yes, _) => {
2755 cmd.args(&["-isysroot", &sdk_root, "-Wl,-syslibroot", &sdk_root]);
2757 LinkerFlavor::Darwin(Cc::No, _) => {
2758 cmd.args(&["-syslibroot", &sdk_root]);
2760 _ => unreachable!(),
2764 fn get_apple_sdk_root(sdk_name: &str) -> Result<String, errors::AppleSdkRootError<'_>> {
2765 // Following what clang does
2766 // (https://github.com/llvm/llvm-project/blob/
2767 // 296a80102a9b72c3eda80558fb78a3ed8849b341/clang/lib/Driver/ToolChains/Darwin.cpp#L1661-L1678)
2768 // to allow the SDK path to be set. (For clang, xcrun sets
2769 // SDKROOT; for rustc, the user or build system can set it, or we
2770 // can fall back to checking for xcrun on PATH.)
2771 if let Ok(sdkroot) = env::var("SDKROOT") {
2772 let p = Path::new(&sdkroot);
2774 // Ignore `SDKROOT` if it's clearly set for the wrong platform.
2776 if sdkroot.contains("TVSimulator.platform")
2777 || sdkroot.contains("MacOSX.platform") => {}
2779 if sdkroot.contains("TVOS.platform") || sdkroot.contains("MacOSX.platform") => {}
2781 if sdkroot.contains("iPhoneSimulator.platform")
2782 || sdkroot.contains("MacOSX.platform") => {}
2784 if sdkroot.contains("iPhoneOS.platform") || sdkroot.contains("MacOSX.platform") => {
2787 if sdkroot.contains("iPhoneOS.platform")
2788 || sdkroot.contains("iPhoneSimulator.platform") => {}
2790 if sdkroot.contains("WatchSimulator.platform")
2791 || sdkroot.contains("MacOSX.platform") => {}
2793 if sdkroot.contains("WatchOS.platform") || sdkroot.contains("MacOSX.platform") => {}
2794 // Ignore `SDKROOT` if it's not a valid path.
2795 _ if !p.is_absolute() || p == Path::new("/") || !p.exists() => {}
2796 _ => return Ok(sdkroot),
2800 Command::new("xcrun").arg("--show-sdk-path").arg("-sdk").arg(sdk_name).output().and_then(
2802 if output.status.success() {
2803 Ok(String::from_utf8(output.stdout).unwrap())
2805 let error = String::from_utf8(output.stderr);
2806 let error = format!("process exit with error: {}", error.unwrap());
2807 Err(io::Error::new(io::ErrorKind::Other, &error[..]))
2813 Ok(output) => Ok(output.trim().to_string()),
2814 Err(error) => Err(errors::AppleSdkRootError::SdkPath { sdk_name, error }),
2818 fn add_gcc_ld_path(cmd: &mut dyn Linker, sess: &Session, flavor: LinkerFlavor) {
2819 if let Some(ld_impl) = sess.opts.unstable_opts.gcc_ld {
2820 if let LinkerFlavor::Gnu(Cc::Yes, _)
2821 | LinkerFlavor::Darwin(Cc::Yes, _)
2822 | LinkerFlavor::WasmLld(Cc::Yes) = flavor
2826 // Implement the "self-contained" part of -Zgcc-ld
2827 // by adding rustc distribution directories to the tool search path.
2828 for path in sess.get_tools_search_paths(false) {
2830 let mut arg = OsString::from("-B");
2831 arg.push(path.join("gcc-ld"));
2835 // Implement the "linker flavor" part of -Zgcc-ld
2836 // by asking cc to use some kind of lld.
2837 cmd.arg("-fuse-ld=lld");
2839 if !flavor.is_gnu() {
2840 // Tell clang to use a non-default LLD flavor.
2841 // Gcc doesn't understand the target option, but we currently assume
2842 // that gcc is not used for Apple and Wasm targets (#97402).
2844 // Note that we don't want to do that by default on macOS: e.g. passing a
2845 // 10.7 target to LLVM works, but not to recent versions of clang/macOS, as
2846 // shown in issue #101653 and the discussion in PR #101792.
2848 // It could be required in some cases of cross-compiling with
2849 // `-Zgcc-ld=lld`, but this is generally unspecified, and we don't know
2850 // which specific versions of clang, macOS SDK, host and target OS
2851 // combinations impact us here.
2853 // So we do a simple first-approximation until we know more of what the
2854 // Apple targets require (and which would be handled prior to hitting this
2855 // `-Zgcc-ld=lld` codepath anyway), but the expectation is that until then
2856 // this should be manually passed if needed. We specify the target when
2857 // targeting a different linker flavor on macOS, and that's also always
2858 // the case when targeting WASM.
2859 if sess.target.linker_flavor != sess.host.linker_flavor {
2860 cmd.arg(format!("--target={}", sess.target.llvm_target));
2866 sess.emit_fatal(errors::OptionGccOnly);