1 use rustc_data_structures::fx::FxHashSet;
2 use rustc_data_structures::temp_dir::MaybeTempDir;
3 use rustc_errors::Handler;
4 use rustc_fs_util::fix_windows_verbatim_for_gcc;
5 use rustc_hir::def_id::CrateNum;
6 use rustc_middle::middle::cstore::{EncodedMetadata, LibSource};
7 use rustc_middle::middle::dependency_format::Linkage;
8 use rustc_session::config::{self, CFGuard, CrateType, DebugInfo};
9 use rustc_session::config::{OutputFilenames, OutputType, PrintRequest, SanitizerSet};
10 use rustc_session::output::{check_file_is_writeable, invalid_output_for_target, out_filename};
11 use rustc_session::search_paths::PathKind;
12 use rustc_session::utils::NativeLibKind;
13 /// For all the linkers we support, and information they might
14 /// need out of the shared crate context before we get rid of it.
15 use rustc_session::{filesearch, Session};
16 use rustc_span::symbol::Symbol;
17 use rustc_target::spec::crt_objects::{CrtObjects, CrtObjectsFallback};
18 use rustc_target::spec::{LinkOutputKind, LinkerFlavor, LldFlavor, SplitDebuginfo};
19 use rustc_target::spec::{PanicStrategy, RelocModel, RelroLevel, Target};
21 use super::archive::ArchiveBuilder;
22 use super::command::Command;
23 use super::linker::{self, Linker};
24 use super::rpath::{self, RPathConfig};
26 looks_like_rust_object_file, CodegenResults, CompiledModule, CrateInfo, NativeLib,
30 use cc::windows_registry;
31 use tempfile::Builder as TempFileBuilder;
33 use std::ffi::OsString;
34 use std::path::{Path, PathBuf};
35 use std::process::{ExitStatus, Output, Stdio};
36 use std::{ascii, char, env, fmt, fs, io, mem, str};
38 pub fn ensure_removed(diag_handler: &Handler, path: &Path) {
39 if let Err(e) = fs::remove_file(path) {
40 if e.kind() != io::ErrorKind::NotFound {
41 diag_handler.err(&format!("failed to remove {}: {}", path.display(), e));
46 /// Performs the linkage portion of the compilation phase. This will generate all
47 /// of the requested outputs for this compilation session.
48 pub fn link_binary<'a, B: ArchiveBuilder<'a>>(
50 codegen_results: &CodegenResults,
51 outputs: &OutputFilenames,
55 let _timer = sess.timer("link_binary");
56 let output_metadata = sess.opts.output_types.contains_key(&OutputType::Metadata);
57 for &crate_type in sess.crate_types().iter() {
58 // Ignore executable crates if we have -Z no-codegen, as they will error.
59 if (sess.opts.debugging_opts.no_codegen || !sess.opts.output_types.should_codegen())
61 && crate_type == CrateType::Executable
66 if invalid_output_for_target(sess, crate_type) {
68 "invalid output type `{:?}` for target os `{}`",
70 sess.opts.target_triple
74 sess.time("link_binary_check_files_are_writeable", || {
75 for obj in codegen_results.modules.iter().filter_map(|m| m.object.as_ref()) {
76 check_file_is_writeable(obj, sess);
80 if outputs.outputs.should_link() {
81 let tmpdir = TempFileBuilder::new()
84 .unwrap_or_else(|err| sess.fatal(&format!("couldn't create a temp dir: {}", err)));
85 let path = MaybeTempDir::new(tmpdir, sess.opts.cg.save_temps);
86 let out_filename = out_filename(sess, crate_type, outputs, crate_name);
89 let _timer = sess.timer("link_rlib");
90 link_rlib::<B>(sess, codegen_results, RlibFlavor::Normal, &out_filename, &path)
93 CrateType::Staticlib => {
94 link_staticlib::<B>(sess, codegen_results, &out_filename, &path);
107 if sess.opts.json_artifact_notifications {
108 sess.parse_sess.span_diagnostic.emit_artifact_notification(&out_filename, "link");
113 // Remove the temporary object file and metadata if we aren't saving temps
114 sess.time("link_binary_remove_temps", || {
115 if !sess.opts.cg.save_temps {
116 let remove_temps_from_module = |module: &CompiledModule| {
117 if let Some(ref obj) = module.object {
118 ensure_removed(sess.diagnostic(), obj);
121 if let Some(ref obj) = module.dwarf_object {
122 ensure_removed(sess.diagnostic(), obj);
126 if sess.opts.output_types.should_link() && !preserve_objects_for_their_debuginfo(sess) {
127 for module in &codegen_results.modules {
128 remove_temps_from_module(module);
132 if let Some(ref metadata_module) = codegen_results.metadata_module {
133 remove_temps_from_module(metadata_module);
136 if let Some(ref allocator_module) = codegen_results.allocator_module {
137 remove_temps_from_module(allocator_module);
143 // The third parameter is for env vars, used on windows to set up the
144 // path for MSVC to find its DLLs, and gcc to find its bundled
149 flavor: LinkerFlavor,
150 self_contained: bool,
152 let msvc_tool = windows_registry::find_tool(&sess.opts.target_triple.triple(), "link.exe");
154 // If our linker looks like a batch script on Windows then to execute this
155 // we'll need to spawn `cmd` explicitly. This is primarily done to handle
156 // emscripten where the linker is `emcc.bat` and needs to be spawned as
157 // `cmd /c emcc.bat ...`.
159 // This worked historically but is needed manually since #42436 (regression
160 // was tagged as #42791) and some more info can be found on #44443 for
161 // emscripten itself.
162 let mut cmd = match linker.to_str() {
163 Some(linker) if cfg!(windows) && linker.ends_with(".bat") => Command::bat_script(linker),
165 LinkerFlavor::Lld(f) => Command::lld(linker, f),
166 LinkerFlavor::Msvc if sess.opts.cg.linker.is_none() && sess.target.linker.is_none() => {
167 Command::new(msvc_tool.as_ref().map_or(linker, |t| t.path()))
169 _ => Command::new(linker),
173 // UWP apps have API restrictions enforced during Store submissions.
174 // To comply with the Windows App Certification Kit,
175 // MSVC needs to link with the Store versions of the runtime libraries (vcruntime, msvcrt, etc).
176 let t = &sess.target;
177 if (flavor == LinkerFlavor::Msvc || flavor == LinkerFlavor::Lld(LldFlavor::Link))
180 if let Some(ref tool) = msvc_tool {
181 let original_path = tool.path();
182 if let Some(ref root_lib_path) = original_path.ancestors().nth(4) {
183 let arch = match t.arch.as_str() {
184 "x86_64" => Some("x64"),
185 "x86" => Some("x86"),
186 "aarch64" => Some("arm64"),
187 "arm" => Some("arm"),
190 if let Some(ref a) = arch {
191 // FIXME: Move this to `fn linker_with_args`.
192 let mut arg = OsString::from("/LIBPATH:");
193 arg.push(format!("{}\\lib\\{}\\store", root_lib_path.display(), a));
196 warn!("arch is not supported");
199 warn!("MSVC root path lib location not found");
202 warn!("link.exe not found");
206 // The compiler's sysroot often has some bundled tools, so add it to the
207 // PATH for the child.
208 let mut new_path = sess.host_filesearch(PathKind::All).get_tools_search_paths(self_contained);
209 let mut msvc_changed_path = false;
210 if sess.target.is_like_msvc {
211 if let Some(ref tool) = msvc_tool {
212 cmd.args(tool.args());
213 for &(ref k, ref v) in tool.env() {
215 new_path.extend(env::split_paths(v));
216 msvc_changed_path = true;
224 if !msvc_changed_path {
225 if let Some(path) = env::var_os("PATH") {
226 new_path.extend(env::split_paths(&path));
229 cmd.env("PATH", env::join_paths(new_path).unwrap());
234 pub fn each_linked_rlib(
236 f: &mut dyn FnMut(CrateNum, &Path),
237 ) -> Result<(), String> {
238 let crates = info.used_crates_static.iter();
240 for (ty, list) in info.dependency_formats.iter() {
242 CrateType::Executable
243 | CrateType::Staticlib
245 | CrateType::ProcMacro => {
252 let fmts = match fmts {
254 None => return Err("could not find formats for rlibs".to_string()),
256 for &(cnum, ref path) in crates {
257 match fmts.get(cnum.as_usize() - 1) {
258 Some(&Linkage::NotLinked | &Linkage::IncludedFromDylib) => continue,
260 None => return Err("could not find formats for rlibs".to_string()),
262 let name = &info.crate_name[&cnum];
263 let path = match *path {
264 LibSource::Some(ref p) => p,
265 LibSource::MetadataOnly => {
267 "could not find rlib for: `{}`, found rmeta (metadata) file",
271 LibSource::None => return Err(format!("could not find rlib for: `{}`", name)),
278 /// We use a temp directory here to avoid races between concurrent rustc processes,
279 /// such as builds in the same directory using the same filename for metadata while
280 /// building an `.rlib` (stomping over one another), or writing an `.rmeta` into a
281 /// directory being searched for `extern crate` (observing an incomplete file).
282 /// The returned path is the temporary file containing the complete metadata.
283 pub fn emit_metadata(sess: &Session, metadata: &EncodedMetadata, tmpdir: &MaybeTempDir) -> PathBuf {
284 let out_filename = tmpdir.as_ref().join(METADATA_FILENAME);
285 let result = fs::write(&out_filename, &metadata.raw_data);
287 if let Err(e) = result {
288 sess.fatal(&format!("failed to write {}: {}", out_filename.display(), e));
294 /// Create an 'rlib'.
296 /// An rlib in its current incarnation is essentially a renamed .a file. The rlib primarily contains
297 /// the object file of the crate, but it also contains all of the object files from native
298 /// libraries. This is done by unzipping native libraries and inserting all of the contents into
300 fn link_rlib<'a, B: ArchiveBuilder<'a>>(
302 codegen_results: &CodegenResults,
305 tmpdir: &MaybeTempDir,
307 info!("preparing rlib to {:?}", out_filename);
308 let mut ab = <B as ArchiveBuilder>::new(sess, out_filename, None);
310 for obj in codegen_results.modules.iter().filter_map(|m| m.object.as_ref()) {
314 // Note that in this loop we are ignoring the value of `lib.cfg`. That is,
315 // we may not be configured to actually include a static library if we're
316 // adding it here. That's because later when we consume this rlib we'll
317 // decide whether we actually needed the static library or not.
319 // To do this "correctly" we'd need to keep track of which libraries added
320 // which object files to the archive. We don't do that here, however. The
321 // #[link(cfg(..))] feature is unstable, though, and only intended to get
322 // liblibc working. In that sense the check below just indicates that if
323 // there are any libraries we want to omit object files for at link time we
324 // just exclude all custom object files.
326 // Eventually if we want to stabilize or flesh out the #[link(cfg(..))]
327 // feature then we'll need to figure out how to record what objects were
328 // loaded from the libraries found here and then encode that into the
329 // metadata of the rlib we're generating somehow.
330 for lib in codegen_results.crate_info.used_libraries.iter() {
332 NativeLibKind::StaticBundle => {}
333 NativeLibKind::StaticNoBundle
334 | NativeLibKind::Dylib
335 | NativeLibKind::Framework
336 | NativeLibKind::RawDylib
337 | NativeLibKind::Unspecified => continue,
339 if let Some(name) = lib.name {
340 ab.add_native_library(name);
344 // After adding all files to the archive, we need to update the
345 // symbol table of the archive.
348 // Note that it is important that we add all of our non-object "magical
349 // files" *after* all of the object files in the archive. The reason for
350 // this is as follows:
352 // * When performing LTO, this archive will be modified to remove
353 // objects from above. The reason for this is described below.
355 // * When the system linker looks at an archive, it will attempt to
356 // determine the architecture of the archive in order to see whether its
359 // The algorithm for this detection is: iterate over the files in the
360 // archive. Skip magical SYMDEF names. Interpret the first file as an
361 // object file. Read architecture from the object file.
363 // * As one can probably see, if "metadata" and "foo.bc" were placed
364 // before all of the objects, then the architecture of this archive would
365 // not be correctly inferred once 'foo.o' is removed.
367 // Basically, all this means is that this code should not move above the
370 RlibFlavor::Normal => {
371 // Instead of putting the metadata in an object file section, rlibs
372 // contain the metadata in a separate file.
373 ab.add_file(&emit_metadata(sess, &codegen_results.metadata, tmpdir));
375 // After adding all files to the archive, we need to update the
376 // symbol table of the archive. This currently dies on macOS (see
377 // #11162), and isn't necessary there anyway
378 if !sess.target.is_like_osx {
383 RlibFlavor::StaticlibBase => {
384 let obj = codegen_results.allocator_module.as_ref().and_then(|m| m.object.as_ref());
385 if let Some(obj) = obj {
394 /// Create a static archive.
396 /// This is essentially the same thing as an rlib, but it also involves adding all of the upstream
397 /// crates' objects into the archive. This will slurp in all of the native libraries of upstream
398 /// dependencies as well.
400 /// Additionally, there's no way for us to link dynamic libraries, so we warn about all dynamic
401 /// library dependencies that they're not linked in.
403 /// There's no need to include metadata in a static archive, so ensure to not link in the metadata
404 /// object file (and also don't prepare the archive with a metadata file).
405 fn link_staticlib<'a, B: ArchiveBuilder<'a>>(
407 codegen_results: &CodegenResults,
409 tempdir: &MaybeTempDir,
412 link_rlib::<B>(sess, codegen_results, RlibFlavor::StaticlibBase, out_filename, tempdir);
413 let mut all_native_libs = vec![];
415 let res = each_linked_rlib(&codegen_results.crate_info, &mut |cnum, path| {
416 let name = &codegen_results.crate_info.crate_name[&cnum];
417 let native_libs = &codegen_results.crate_info.native_libraries[&cnum];
419 // Here when we include the rlib into our staticlib we need to make a
420 // decision whether to include the extra object files along the way.
421 // These extra object files come from statically included native
422 // libraries, but they may be cfg'd away with #[link(cfg(..))].
424 // This unstable feature, though, only needs liblibc to work. The only
425 // use case there is where musl is statically included in liblibc.rlib,
426 // so if we don't want the included version we just need to skip it. As
427 // a result the logic here is that if *any* linked library is cfg'd away
428 // we just skip all object files.
430 // Clearly this is not sufficient for a general purpose feature, and
431 // we'd want to read from the library's metadata to determine which
432 // object files come from where and selectively skip them.
433 let skip_object_files = native_libs
435 .any(|lib| lib.kind == NativeLibKind::StaticBundle && !relevant_lib(sess, lib));
439 are_upstream_rust_objects_already_included(sess)
440 && !ignored_for_lto(sess, &codegen_results.crate_info, cnum),
445 all_native_libs.extend(codegen_results.crate_info.native_libraries[&cnum].iter().cloned());
447 if let Err(e) = res {
454 if !all_native_libs.is_empty() {
455 if sess.opts.prints.contains(&PrintRequest::NativeStaticLibs) {
456 print_native_static_libs(sess, &all_native_libs);
461 fn escape_stdout_stderr_string(s: &[u8]) -> String {
462 str::from_utf8(s).map(|s| s.to_owned()).unwrap_or_else(|_| {
463 let mut x = "Non-UTF-8 output: ".to_string();
464 x.extend(s.iter().flat_map(|&b| ascii::escape_default(b)).map(char::from));
469 const LLVM_DWP_EXECUTABLE: &'static str = "rust-llvm-dwp";
471 /// Invoke `llvm-dwp` (shipped alongside rustc) to link `dwo` files from Split DWARF into a `dwp`
473 fn link_dwarf_object<'a>(sess: &'a Session, executable_out_filename: &Path) {
474 info!("preparing dwp to {}.dwp", executable_out_filename.to_str().unwrap());
476 let dwp_out_filename = executable_out_filename.with_extension("dwp");
477 let mut cmd = Command::new(LLVM_DWP_EXECUTABLE);
479 cmd.arg(executable_out_filename);
481 cmd.arg(&dwp_out_filename);
483 let mut new_path = sess.host_filesearch(PathKind::All).get_tools_search_paths(false);
484 if let Some(path) = env::var_os("PATH") {
485 new_path.extend(env::split_paths(&path));
487 let new_path = env::join_paths(new_path).unwrap();
488 cmd.env("PATH", new_path);
491 match sess.time("run_dwp", || cmd.output()) {
492 Ok(prog) if !prog.status.success() => {
493 sess.struct_err(&format!(
494 "linking dwarf objects with `{}` failed: {}",
495 LLVM_DWP_EXECUTABLE, prog.status
497 .note(&format!("{:?}", &cmd))
498 .note(&escape_stdout_stderr_string(&prog.stdout))
499 .note(&escape_stdout_stderr_string(&prog.stderr))
501 info!("linker stderr:\n{}", escape_stdout_stderr_string(&prog.stderr));
502 info!("linker stdout:\n{}", escape_stdout_stderr_string(&prog.stdout));
506 let dwp_not_found = e.kind() == io::ErrorKind::NotFound;
507 let mut err = if dwp_not_found {
508 sess.struct_err(&format!("linker `{}` not found", LLVM_DWP_EXECUTABLE))
510 sess.struct_err(&format!("could not exec the linker `{}`", LLVM_DWP_EXECUTABLE))
513 err.note(&e.to_string());
516 err.note(&format!("{:?}", &cmd));
524 /// Create a dynamic library or executable.
526 /// This will invoke the system linker/cc to create the resulting file. This links to all upstream
528 fn link_natively<'a, B: ArchiveBuilder<'a>>(
530 crate_type: CrateType,
532 codegen_results: &CodegenResults,
536 info!("preparing {:?} to {:?}", crate_type, out_filename);
537 let (linker_path, flavor) = linker_and_flavor(sess);
538 let mut cmd = linker_with_args::<B>(
549 linker::disable_localization(&mut cmd);
551 for &(ref k, ref v) in &sess.target.link_env {
554 for k in &sess.target.link_env_remove {
558 if sess.opts.debugging_opts.print_link_args {
559 println!("{:?}", &cmd);
562 // May have not found libraries in the right formats.
563 sess.abort_if_errors();
565 // Invoke the system linker
567 let retry_on_segfault = env::var("RUSTC_RETRY_LINKER_ON_SEGFAULT").is_ok();
572 prog = sess.time("run_linker", || exec_linker(sess, &cmd, out_filename, tmpdir));
573 let output = match prog {
574 Ok(ref output) => output,
577 if output.status.success() {
580 let mut out = output.stderr.clone();
581 out.extend(&output.stdout);
582 let out = String::from_utf8_lossy(&out);
584 // Check to see if the link failed with "unrecognized command line option:
585 // '-no-pie'" for gcc or "unknown argument: '-no-pie'" for clang. If so,
586 // reperform the link step without the -no-pie option. This is safe because
587 // if the linker doesn't support -no-pie then it should not default to
588 // linking executables as pie. Different versions of gcc seem to use
589 // different quotes in the error message so don't check for them.
590 if sess.target.linker_is_gnu
591 && flavor != LinkerFlavor::Ld
592 && (out.contains("unrecognized command line option")
593 || out.contains("unknown argument"))
594 && out.contains("-no-pie")
595 && cmd.get_args().iter().any(|e| e.to_string_lossy() == "-no-pie")
597 info!("linker output: {:?}", out);
598 warn!("Linker does not support -no-pie command line option. Retrying without.");
599 for arg in cmd.take_args() {
600 if arg.to_string_lossy() != "-no-pie" {
608 // Detect '-static-pie' used with an older version of gcc or clang not supporting it.
609 // Fallback from '-static-pie' to '-static' in that case.
610 if sess.target.linker_is_gnu
611 && flavor != LinkerFlavor::Ld
612 && (out.contains("unrecognized command line option")
613 || out.contains("unknown argument"))
614 && (out.contains("-static-pie") || out.contains("--no-dynamic-linker"))
615 && cmd.get_args().iter().any(|e| e.to_string_lossy() == "-static-pie")
617 info!("linker output: {:?}", out);
619 "Linker does not support -static-pie command line option. Retrying with -static instead."
621 // Mirror `add_(pre,post)_link_objects` to replace CRT objects.
622 let self_contained = crt_objects_fallback(sess, crate_type);
623 let opts = &sess.target;
624 let pre_objects = if self_contained {
625 &opts.pre_link_objects_fallback
627 &opts.pre_link_objects
629 let post_objects = if self_contained {
630 &opts.post_link_objects_fallback
632 &opts.post_link_objects
634 let get_objects = |objects: &CrtObjects, kind| {
640 .map(|obj| get_object_file_path(sess, obj, self_contained).into_os_string())
643 let pre_objects_static_pie = get_objects(pre_objects, LinkOutputKind::StaticPicExe);
644 let post_objects_static_pie = get_objects(post_objects, LinkOutputKind::StaticPicExe);
645 let mut pre_objects_static = get_objects(pre_objects, LinkOutputKind::StaticNoPicExe);
646 let mut post_objects_static = get_objects(post_objects, LinkOutputKind::StaticNoPicExe);
647 // Assume that we know insertion positions for the replacement arguments from replaced
648 // arguments, which is true for all supported targets.
649 assert!(pre_objects_static.is_empty() || !pre_objects_static_pie.is_empty());
650 assert!(post_objects_static.is_empty() || !post_objects_static_pie.is_empty());
651 for arg in cmd.take_args() {
652 if arg.to_string_lossy() == "-static-pie" {
653 // Replace the output kind.
655 } else if pre_objects_static_pie.contains(&arg) {
656 // Replace the pre-link objects (replace the first and remove the rest).
657 cmd.args(mem::take(&mut pre_objects_static));
658 } else if post_objects_static_pie.contains(&arg) {
659 // Replace the post-link objects (replace the first and remove the rest).
660 cmd.args(mem::take(&mut post_objects_static));
669 // Here's a terribly awful hack that really shouldn't be present in any
670 // compiler. Here an environment variable is supported to automatically
671 // retry the linker invocation if the linker looks like it segfaulted.
673 // Gee that seems odd, normally segfaults are things we want to know
674 // about! Unfortunately though in rust-lang/rust#38878 we're
675 // experiencing the linker segfaulting on Travis quite a bit which is
676 // causing quite a bit of pain to land PRs when they spuriously fail
677 // due to a segfault.
679 // The issue #38878 has some more debugging information on it as well,
680 // but this unfortunately looks like it's just a race condition in
681 // macOS's linker with some thread pool working in the background. It
682 // seems that no one currently knows a fix for this so in the meantime
683 // we're left with this...
684 if !retry_on_segfault || i > 3 {
687 let msg_segv = "clang: error: unable to execute command: Segmentation fault: 11";
688 let msg_bus = "clang: error: unable to execute command: Bus error: 10";
689 if out.contains(msg_segv) || out.contains(msg_bus) {
691 "looks like the linker segfaulted when we tried to call it, \
692 automatically retrying again. cmd = {:?}, out = {}.",
698 if is_illegal_instruction(&output.status) {
700 "looks like the linker hit an illegal instruction when we \
701 tried to call it, automatically retrying again. cmd = {:?}, ]\
702 out = {}, status = {}.",
703 cmd, out, output.status,
709 fn is_illegal_instruction(status: &ExitStatus) -> bool {
710 use std::os::unix::prelude::*;
711 status.signal() == Some(libc::SIGILL)
715 fn is_illegal_instruction(_status: &ExitStatus) -> bool {
720 fn escape_string(s: &[u8]) -> String {
721 str::from_utf8(s).map(|s| s.to_owned()).unwrap_or_else(|_| {
722 let mut x = "Non-UTF-8 output: ".to_string();
723 x.extend(s.iter().flat_map(|&b| ascii::escape_default(b)).map(char::from));
730 if !prog.status.success() {
731 let mut output = prog.stderr.clone();
732 output.extend_from_slice(&prog.stdout);
733 sess.struct_err(&format!(
734 "linking with `{}` failed: {}",
735 linker_path.display(),
738 .note(&format!("{:?}", &cmd))
739 .note(&escape_stdout_stderr_string(&output))
742 // If MSVC's `link.exe` was expected but the return code
743 // is not a Microsoft LNK error then suggest a way to fix or
744 // install the Visual Studio build tools.
745 if let Some(code) = prog.status.code() {
746 if sess.target.is_like_msvc
747 && flavor == LinkerFlavor::Msvc
748 // Respect the command line override
749 && sess.opts.cg.linker.is_none()
750 // Match exactly "link.exe"
751 && linker_path.to_str() == Some("link.exe")
752 // All Microsoft `link.exe` linking error codes are
753 // four digit numbers in the range 1000 to 9999 inclusive
754 && (code < 1000 || code > 9999)
756 let is_vs_installed = windows_registry::find_vs_version().is_ok();
757 let has_linker = windows_registry::find_tool(
758 &sess.opts.target_triple.triple(),
763 sess.note_without_error("`link.exe` returned an unexpected error");
764 if is_vs_installed && has_linker {
765 // the linker is broken
766 sess.note_without_error(
767 "the Visual Studio build tools may need to be repaired \
768 using the Visual Studio installer",
770 sess.note_without_error(
771 "or a necessary component may be missing from the \
772 \"C++ build tools\" workload",
774 } else if is_vs_installed {
775 // the linker is not installed
776 sess.note_without_error(
777 "in the Visual Studio installer, ensure the \
778 \"C++ build tools\" workload is selected",
781 // visual studio is not installed
782 sess.note_without_error(
783 "you may need to install Visual Studio build tools with the \
784 \"C++ build tools\" workload",
790 sess.abort_if_errors();
792 info!("linker stderr:\n{}", escape_stdout_stderr_string(&prog.stderr));
793 info!("linker stdout:\n{}", escape_stdout_stderr_string(&prog.stdout));
796 let linker_not_found = e.kind() == io::ErrorKind::NotFound;
798 let mut linker_error = {
799 if linker_not_found {
800 sess.struct_err(&format!("linker `{}` not found", linker_path.display()))
802 sess.struct_err(&format!(
803 "could not exec the linker `{}`",
804 linker_path.display()
809 linker_error.note(&e.to_string());
811 if !linker_not_found {
812 linker_error.note(&format!("{:?}", &cmd));
817 if sess.target.is_like_msvc && linker_not_found {
818 sess.note_without_error(
819 "the msvc targets depend on the msvc linker \
820 but `link.exe` was not found",
822 sess.note_without_error(
823 "please ensure that VS 2013, VS 2015, VS 2017 or VS 2019 \
824 was installed with the Visual C++ option",
827 sess.abort_if_errors();
831 match sess.split_debuginfo() {
832 // If split debug information is disabled or located in individual files
833 // there's nothing to do here.
834 SplitDebuginfo::Off | SplitDebuginfo::Unpacked => {}
836 // If packed split-debuginfo is requested, but the final compilation
837 // doesn't actually have any debug information, then we skip this step.
838 SplitDebuginfo::Packed if sess.opts.debuginfo == DebugInfo::None => {}
840 // On macOS the external `dsymutil` tool is used to create the packed
841 // debug information. Note that this will read debug information from
842 // the objects on the filesystem which we'll clean up later.
843 SplitDebuginfo::Packed if sess.target.is_like_osx => {
844 let prog = Command::new("dsymutil").arg(out_filename).output();
847 if !prog.status.success() {
848 let mut output = prog.stderr.clone();
849 output.extend_from_slice(&prog.stdout);
850 sess.struct_warn(&format!(
851 "processing debug info with `dsymutil` failed: {}",
854 .note(&escape_string(&output))
858 Err(e) => sess.fatal(&format!("unable to run `dsymutil`: {}", e)),
862 // On MSVC packed debug information is produced by the linker itself so
863 // there's no need to do anything else here.
864 SplitDebuginfo::Packed if sess.target.is_like_msvc => {}
866 // ... and otherwise we're processing a `*.dwp` packed dwarf file.
867 SplitDebuginfo::Packed => link_dwarf_object(sess, &out_filename),
871 fn link_sanitizers(sess: &Session, crate_type: CrateType, linker: &mut dyn Linker) {
872 // On macOS the runtimes are distributed as dylibs which should be linked to
873 // both executables and dynamic shared objects. Everywhere else the runtimes
874 // are currently distributed as static liraries which should be linked to
876 let needs_runtime = match crate_type {
877 CrateType::Executable => true,
878 CrateType::Dylib | CrateType::Cdylib | CrateType::ProcMacro => sess.target.is_like_osx,
879 CrateType::Rlib | CrateType::Staticlib => false,
886 let sanitizer = sess.opts.debugging_opts.sanitizer;
887 if sanitizer.contains(SanitizerSet::ADDRESS) {
888 link_sanitizer_runtime(sess, linker, "asan");
890 if sanitizer.contains(SanitizerSet::LEAK) {
891 link_sanitizer_runtime(sess, linker, "lsan");
893 if sanitizer.contains(SanitizerSet::MEMORY) {
894 link_sanitizer_runtime(sess, linker, "msan");
896 if sanitizer.contains(SanitizerSet::THREAD) {
897 link_sanitizer_runtime(sess, linker, "tsan");
899 if sanitizer.contains(SanitizerSet::HWADDRESS) {
900 link_sanitizer_runtime(sess, linker, "hwasan");
904 fn link_sanitizer_runtime(sess: &Session, linker: &mut dyn Linker, name: &str) {
905 fn find_sanitizer_runtime(sess: &Session, filename: &String) -> PathBuf {
907 filesearch::make_target_lib_path(&sess.sysroot, sess.opts.target_triple.triple());
908 let path = session_tlib.join(&filename);
912 let default_sysroot = filesearch::get_or_default_sysroot();
913 let default_tlib = filesearch::make_target_lib_path(
915 sess.opts.target_triple.triple(),
921 let channel = option_env!("CFG_RELEASE_CHANNEL")
922 .map(|channel| format!("-{}", channel))
923 .unwrap_or_default();
925 match sess.opts.target_triple.triple() {
926 "aarch64-apple-darwin" | "x86_64-apple-darwin" => {
927 // On Apple platforms, the sanitizer is always built as a dylib, and
928 // LLVM will link to `@rpath/*.dylib`, so we need to specify an
929 // rpath to the library as well (the rpath should be absolute, see
930 // PR #41352 for details).
931 let filename = format!("rustc{}_rt.{}", channel, name);
932 let path = find_sanitizer_runtime(&sess, &filename);
933 let rpath = path.to_str().expect("non-utf8 component in path");
934 linker.args(&["-Wl,-rpath", "-Xlinker", rpath]);
935 linker.link_dylib(Symbol::intern(&filename));
938 | "aarch64-unknown-linux-gnu"
940 | "x86_64-unknown-freebsd"
941 | "x86_64-unknown-linux-gnu" => {
942 let filename = format!("librustc{}_rt.{}.a", channel, name);
943 let path = find_sanitizer_runtime(&sess, &filename).join(&filename);
944 linker.link_whole_rlib(&path);
950 /// Returns a boolean indicating whether the specified crate should be ignored
953 /// Crates ignored during LTO are not lumped together in the "massive object
954 /// file" that we create and are linked in their normal rlib states. See
955 /// comments below for what crates do not participate in LTO.
957 /// It's unusual for a crate to not participate in LTO. Typically only
958 /// compiler-specific and unstable crates have a reason to not participate in
960 pub fn ignored_for_lto(sess: &Session, info: &CrateInfo, cnum: CrateNum) -> bool {
961 // If our target enables builtin function lowering in LLVM then the
962 // crates providing these functions don't participate in LTO (e.g.
963 // no_builtins or compiler builtins crates).
964 !sess.target.no_builtins
965 && (info.compiler_builtins == Some(cnum) || info.is_no_builtins.contains(&cnum))
968 fn linker_and_flavor(sess: &Session) -> (PathBuf, LinkerFlavor) {
971 linker: Option<PathBuf>,
972 flavor: Option<LinkerFlavor>,
973 ) -> Option<(PathBuf, LinkerFlavor)> {
974 match (linker, flavor) {
975 (Some(linker), Some(flavor)) => Some((linker, flavor)),
976 // only the linker flavor is known; use the default linker for the selected flavor
977 (None, Some(flavor)) => Some((
978 PathBuf::from(match flavor {
979 LinkerFlavor::Em => {
986 LinkerFlavor::Gcc => {
987 if cfg!(any(target_os = "solaris", target_os = "illumos")) {
988 // On historical Solaris systems, "cc" may have
989 // been Sun Studio, which is not flag-compatible
990 // with "gcc". This history casts a long shadow,
991 // and many modern illumos distributions today
992 // ship GCC as "gcc" without also making it
993 // available as "cc".
999 LinkerFlavor::Ld => "ld",
1000 LinkerFlavor::Msvc => "link.exe",
1001 LinkerFlavor::Lld(_) => "lld",
1002 LinkerFlavor::PtxLinker => "rust-ptx-linker",
1006 (Some(linker), None) => {
1007 let stem = linker.file_stem().and_then(|stem| stem.to_str()).unwrap_or_else(|| {
1008 sess.fatal("couldn't extract file stem from specified linker")
1011 let flavor = if stem == "emcc" {
1013 } else if stem == "gcc"
1014 || stem.ends_with("-gcc")
1016 || stem.ends_with("-clang")
1019 } else if stem == "ld" || stem == "ld.lld" || stem.ends_with("-ld") {
1021 } else if stem == "link" || stem == "lld-link" {
1023 } else if stem == "lld" || stem == "rust-lld" {
1024 LinkerFlavor::Lld(sess.target.lld_flavor)
1026 // fall back to the value in the target spec
1027 sess.target.linker_flavor
1030 Some((linker, flavor))
1032 (None, None) => None,
1036 // linker and linker flavor specified via command line have precedence over what the target
1037 // specification specifies
1038 if let Some(ret) = infer_from(sess, sess.opts.cg.linker.clone(), sess.opts.cg.linker_flavor) {
1042 if let Some(ret) = infer_from(
1044 sess.target.linker.clone().map(PathBuf::from),
1045 Some(sess.target.linker_flavor),
1050 bug!("Not enough information provided to determine how to invoke the linker");
1053 /// Returns a boolean indicating whether we should preserve the object files on
1054 /// the filesystem for their debug information. This is often useful with
1055 /// split-dwarf like schemes.
1056 fn preserve_objects_for_their_debuginfo(sess: &Session) -> bool {
1057 // If the objects don't have debuginfo there's nothing to preserve.
1058 if sess.opts.debuginfo == config::DebugInfo::None {
1062 // If we're only producing artifacts that are archives, no need to preserve
1063 // the objects as they're losslessly contained inside the archives.
1065 sess.crate_types().iter().any(|&x| x != CrateType::Rlib && x != CrateType::Staticlib);
1070 // "unpacked" split debuginfo means that we leave object files as the
1071 // debuginfo is found in the original object files themselves
1072 sess.split_debuginfo() == SplitDebuginfo::Unpacked
1075 pub fn archive_search_paths(sess: &Session) -> Vec<PathBuf> {
1076 sess.target_filesearch(PathKind::Native).search_path_dirs()
1084 fn print_native_static_libs(sess: &Session, all_native_libs: &[NativeLib]) {
1085 let lib_args: Vec<_> = all_native_libs
1087 .filter(|l| relevant_lib(sess, l))
1089 let name = lib.name?;
1091 NativeLibKind::StaticNoBundle
1092 | NativeLibKind::Dylib
1093 | NativeLibKind::Unspecified => {
1094 if sess.target.is_like_msvc {
1095 Some(format!("{}.lib", name))
1097 Some(format!("-l{}", name))
1100 NativeLibKind::Framework => {
1101 // ld-only syntax, since there are no frameworks in MSVC
1102 Some(format!("-framework {}", name))
1104 // These are included, no need to print them
1105 NativeLibKind::StaticBundle | NativeLibKind::RawDylib => None,
1109 if !lib_args.is_empty() {
1110 sess.note_without_error(
1111 "Link against the following native artifacts when linking \
1112 against this static library. The order and any duplication \
1113 can be significant on some platforms.",
1115 // Prefix for greppability
1116 sess.note_without_error(&format!("native-static-libs: {}", &lib_args.join(" ")));
1120 fn get_object_file_path(sess: &Session, name: &str, self_contained: bool) -> PathBuf {
1121 let fs = sess.target_filesearch(PathKind::Native);
1122 let file_path = fs.get_lib_path().join(name);
1123 if file_path.exists() {
1126 // Special directory with objects used only in self-contained linkage mode
1128 let file_path = fs.get_self_contained_lib_path().join(name);
1129 if file_path.exists() {
1133 for search_path in fs.search_paths() {
1134 let file_path = search_path.dir.join(name);
1135 if file_path.exists() {
1145 out_filename: &Path,
1147 ) -> io::Result<Output> {
1148 // When attempting to spawn the linker we run a risk of blowing out the
1149 // size limits for spawning a new process with respect to the arguments
1150 // we pass on the command line.
1152 // Here we attempt to handle errors from the OS saying "your list of
1153 // arguments is too big" by reinvoking the linker again with an `@`-file
1154 // that contains all the arguments. The theory is that this is then
1155 // accepted on all linkers and the linker will read all its options out of
1156 // there instead of looking at the command line.
1157 if !cmd.very_likely_to_exceed_some_spawn_limit() {
1158 match cmd.command().stdout(Stdio::piped()).stderr(Stdio::piped()).spawn() {
1160 let output = child.wait_with_output();
1161 flush_linked_file(&output, out_filename)?;
1164 Err(ref e) if command_line_too_big(e) => {
1165 info!("command line to linker was too big: {}", e);
1167 Err(e) => return Err(e),
1171 info!("falling back to passing arguments to linker via an @-file");
1172 let mut cmd2 = cmd.clone();
1173 let mut args = String::new();
1174 for arg in cmd2.take_args() {
1176 &Escape { arg: arg.to_str().unwrap(), is_like_msvc: sess.target.is_like_msvc }
1181 let file = tmpdir.join("linker-arguments");
1182 let bytes = if sess.target.is_like_msvc {
1183 let mut out = Vec::with_capacity((1 + args.len()) * 2);
1184 // start the stream with a UTF-16 BOM
1185 for c in std::iter::once(0xFEFF).chain(args.encode_utf16()) {
1186 // encode in little endian
1188 out.push((c >> 8) as u8);
1194 fs::write(&file, &bytes)?;
1195 cmd2.arg(format!("@{}", file.display()));
1196 info!("invoking linker {:?}", cmd2);
1197 let output = cmd2.output();
1198 flush_linked_file(&output, out_filename)?;
1201 #[cfg(not(windows))]
1202 fn flush_linked_file(_: &io::Result<Output>, _: &Path) -> io::Result<()> {
1207 fn flush_linked_file(
1208 command_output: &io::Result<Output>,
1209 out_filename: &Path,
1210 ) -> io::Result<()> {
1211 // On Windows, under high I/O load, output buffers are sometimes not flushed,
1212 // even long after process exit, causing nasty, non-reproducible output bugs.
1214 // File::sync_all() calls FlushFileBuffers() down the line, which solves the problem.
1216 // А full writeup of the original Chrome bug can be found at
1217 // randomascii.wordpress.com/2018/02/25/compiler-bug-linker-bug-windows-kernel-bug/amp
1219 if let &Ok(ref out) = command_output {
1220 if out.status.success() {
1221 if let Ok(of) = fs::OpenOptions::new().write(true).open(out_filename) {
1231 fn command_line_too_big(err: &io::Error) -> bool {
1232 err.raw_os_error() == Some(::libc::E2BIG)
1236 fn command_line_too_big(err: &io::Error) -> bool {
1237 const ERROR_FILENAME_EXCED_RANGE: i32 = 206;
1238 err.raw_os_error() == Some(ERROR_FILENAME_EXCED_RANGE)
1241 #[cfg(not(any(unix, windows)))]
1242 fn command_line_too_big(_: &io::Error) -> bool {
1251 impl<'a> fmt::Display for Escape<'a> {
1252 fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
1253 if self.is_like_msvc {
1254 // This is "documented" at
1255 // https://docs.microsoft.com/en-us/cpp/build/reference/at-specify-a-linker-response-file
1257 // Unfortunately there's not a great specification of the
1258 // syntax I could find online (at least) but some local
1259 // testing showed that this seemed sufficient-ish to catch
1260 // at least a few edge cases.
1262 for c in self.arg.chars() {
1264 '"' => write!(f, "\\{}", c)?,
1265 c => write!(f, "{}", c)?,
1270 // This is documented at https://linux.die.net/man/1/ld, namely:
1272 // > Options in file are separated by whitespace. A whitespace
1273 // > character may be included in an option by surrounding the
1274 // > entire option in either single or double quotes. Any
1275 // > character (including a backslash) may be included by
1276 // > prefixing the character to be included with a backslash.
1278 // We put an argument on each line, so all we need to do is
1279 // ensure the line is interpreted as one whole argument.
1280 for c in self.arg.chars() {
1282 '\\' | ' ' => write!(f, "\\{}", c)?,
1283 c => write!(f, "{}", c)?,
1292 fn link_output_kind(sess: &Session, crate_type: CrateType) -> LinkOutputKind {
1293 let kind = match (crate_type, sess.crt_static(Some(crate_type)), sess.relocation_model()) {
1294 (CrateType::Executable, _, _) if sess.is_wasi_reactor() => LinkOutputKind::WasiReactorExe,
1295 (CrateType::Executable, false, RelocModel::Pic) => LinkOutputKind::DynamicPicExe,
1296 (CrateType::Executable, false, _) => LinkOutputKind::DynamicNoPicExe,
1297 (CrateType::Executable, true, RelocModel::Pic) => LinkOutputKind::StaticPicExe,
1298 (CrateType::Executable, true, _) => LinkOutputKind::StaticNoPicExe,
1299 (_, true, _) => LinkOutputKind::StaticDylib,
1300 (_, false, _) => LinkOutputKind::DynamicDylib,
1303 // Adjust the output kind to target capabilities.
1304 let opts = &sess.target;
1305 let pic_exe_supported = opts.position_independent_executables;
1306 let static_pic_exe_supported = opts.static_position_independent_executables;
1307 let static_dylib_supported = opts.crt_static_allows_dylibs;
1309 LinkOutputKind::DynamicPicExe if !pic_exe_supported => LinkOutputKind::DynamicNoPicExe,
1310 LinkOutputKind::StaticPicExe if !static_pic_exe_supported => LinkOutputKind::StaticNoPicExe,
1311 LinkOutputKind::StaticDylib if !static_dylib_supported => LinkOutputKind::DynamicDylib,
1316 // Returns true if linker is located within sysroot
1317 fn detect_self_contained_mingw(sess: &Session) -> bool {
1318 let (linker, _) = linker_and_flavor(&sess);
1319 // Assume `-C linker=rust-lld` as self-contained mode
1320 if linker == Path::new("rust-lld") {
1323 let linker_with_extension = if cfg!(windows) && linker.extension().is_none() {
1324 linker.with_extension("exe")
1328 for dir in env::split_paths(&env::var_os("PATH").unwrap_or_default()) {
1329 let full_path = dir.join(&linker_with_extension);
1330 // If linker comes from sysroot assume self-contained mode
1331 if full_path.is_file() && !full_path.starts_with(&sess.sysroot) {
1338 /// Whether we link to our own CRT objects instead of relying on gcc to pull them.
1339 /// We only provide such support for a very limited number of targets.
1340 fn crt_objects_fallback(sess: &Session, crate_type: CrateType) -> bool {
1341 if let Some(self_contained) = sess.opts.cg.link_self_contained {
1342 return self_contained;
1345 match sess.target.crt_objects_fallback {
1346 // FIXME: Find a better heuristic for "native musl toolchain is available",
1347 // based on host and linker path, for example.
1348 // (https://github.com/rust-lang/rust/pull/71769#issuecomment-626330237).
1349 Some(CrtObjectsFallback::Musl) => sess.crt_static(Some(crate_type)),
1350 Some(CrtObjectsFallback::Mingw) => {
1351 sess.host == sess.target
1352 && sess.target.vendor != "uwp"
1353 && detect_self_contained_mingw(&sess)
1355 // FIXME: Figure out cases in which WASM needs to link with a native toolchain.
1356 Some(CrtObjectsFallback::Wasm) => true,
1361 /// Add pre-link object files defined by the target spec.
1362 fn add_pre_link_objects(
1363 cmd: &mut dyn Linker,
1365 link_output_kind: LinkOutputKind,
1366 self_contained: bool,
1368 let opts = &sess.target;
1370 if self_contained { &opts.pre_link_objects_fallback } else { &opts.pre_link_objects };
1371 for obj in objects.get(&link_output_kind).iter().copied().flatten() {
1372 cmd.add_object(&get_object_file_path(sess, obj, self_contained));
1376 /// Add post-link object files defined by the target spec.
1377 fn add_post_link_objects(
1378 cmd: &mut dyn Linker,
1380 link_output_kind: LinkOutputKind,
1381 self_contained: bool,
1383 let opts = &sess.target;
1385 if self_contained { &opts.post_link_objects_fallback } else { &opts.post_link_objects };
1386 for obj in objects.get(&link_output_kind).iter().copied().flatten() {
1387 cmd.add_object(&get_object_file_path(sess, obj, self_contained));
1391 /// Add arbitrary "pre-link" args defined by the target spec or from command line.
1392 /// FIXME: Determine where exactly these args need to be inserted.
1393 fn add_pre_link_args(cmd: &mut dyn Linker, sess: &Session, flavor: LinkerFlavor) {
1394 if let Some(args) = sess.target.pre_link_args.get(&flavor) {
1397 cmd.args(&sess.opts.debugging_opts.pre_link_args);
1400 /// Add a link script embedded in the target, if applicable.
1401 fn add_link_script(cmd: &mut dyn Linker, sess: &Session, tmpdir: &Path, crate_type: CrateType) {
1402 match (crate_type, &sess.target.link_script) {
1403 (CrateType::Cdylib | CrateType::Executable, Some(script)) => {
1404 if !sess.target.linker_is_gnu {
1405 sess.fatal("can only use link script when linking with GNU-like linker");
1408 let file_name = ["rustc", &sess.target.llvm_target, "linkfile.ld"].join("-");
1410 let path = tmpdir.join(file_name);
1411 if let Err(e) = fs::write(&path, script) {
1412 sess.fatal(&format!("failed to write link script to {}: {}", path.display(), e));
1415 cmd.arg("--script");
1422 /// Add arbitrary "user defined" args defined from command line and by `#[link_args]` attributes.
1423 /// FIXME: Determine where exactly these args need to be inserted.
1424 fn add_user_defined_link_args(
1425 cmd: &mut dyn Linker,
1427 codegen_results: &CodegenResults,
1429 cmd.args(&sess.opts.cg.link_args);
1430 cmd.args(&*codegen_results.crate_info.link_args);
1433 /// Add arbitrary "late link" args defined by the target spec.
1434 /// FIXME: Determine where exactly these args need to be inserted.
1435 fn add_late_link_args(
1436 cmd: &mut dyn Linker,
1438 flavor: LinkerFlavor,
1439 crate_type: CrateType,
1440 codegen_results: &CodegenResults,
1442 let any_dynamic_crate = crate_type == CrateType::Dylib
1443 || codegen_results.crate_info.dependency_formats.iter().any(|(ty, list)| {
1444 *ty == crate_type && list.iter().any(|&linkage| linkage == Linkage::Dynamic)
1446 if any_dynamic_crate {
1447 if let Some(args) = sess.target.late_link_args_dynamic.get(&flavor) {
1451 if let Some(args) = sess.target.late_link_args_static.get(&flavor) {
1455 if let Some(args) = sess.target.late_link_args.get(&flavor) {
1460 /// Add arbitrary "post-link" args defined by the target spec.
1461 /// FIXME: Determine where exactly these args need to be inserted.
1462 fn add_post_link_args(cmd: &mut dyn Linker, sess: &Session, flavor: LinkerFlavor) {
1463 if let Some(args) = sess.target.post_link_args.get(&flavor) {
1468 /// Add object files containing code from the current crate.
1469 fn add_local_crate_regular_objects(cmd: &mut dyn Linker, codegen_results: &CodegenResults) {
1470 for obj in codegen_results.modules.iter().filter_map(|m| m.object.as_ref()) {
1471 cmd.add_object(obj);
1475 /// Add object files for allocator code linked once for the whole crate tree.
1476 fn add_local_crate_allocator_objects(cmd: &mut dyn Linker, codegen_results: &CodegenResults) {
1477 if let Some(obj) = codegen_results.allocator_module.as_ref().and_then(|m| m.object.as_ref()) {
1478 cmd.add_object(obj);
1482 /// Add object files containing metadata for the current crate.
1483 fn add_local_crate_metadata_objects(
1484 cmd: &mut dyn Linker,
1485 crate_type: CrateType,
1486 codegen_results: &CodegenResults,
1488 // When linking a dynamic library, we put the metadata into a section of the
1489 // executable. This metadata is in a separate object file from the main
1490 // object file, so we link that in here.
1491 if crate_type == CrateType::Dylib || crate_type == CrateType::ProcMacro {
1492 if let Some(obj) = codegen_results.metadata_module.as_ref().and_then(|m| m.object.as_ref())
1494 cmd.add_object(obj);
1499 /// Link native libraries corresponding to the current crate and all libraries corresponding to
1500 /// all its dependency crates.
1501 /// FIXME: Consider combining this with the functions above adding object files for the local crate.
1502 fn link_local_crate_native_libs_and_dependent_crate_libs<'a, B: ArchiveBuilder<'a>>(
1503 cmd: &mut dyn Linker,
1505 crate_type: CrateType,
1506 codegen_results: &CodegenResults,
1509 // Take careful note of the ordering of the arguments we pass to the linker
1510 // here. Linkers will assume that things on the left depend on things to the
1511 // right. Things on the right cannot depend on things on the left. This is
1512 // all formally implemented in terms of resolving symbols (libs on the right
1513 // resolve unknown symbols of libs on the left, but not vice versa).
1515 // For this reason, we have organized the arguments we pass to the linker as
1518 // 1. The local object that LLVM just generated
1519 // 2. Local native libraries
1520 // 3. Upstream rust libraries
1521 // 4. Upstream native libraries
1523 // The rationale behind this ordering is that those items lower down in the
1524 // list can't depend on items higher up in the list. For example nothing can
1525 // depend on what we just generated (e.g., that'd be a circular dependency).
1526 // Upstream rust libraries are not allowed to depend on our local native
1527 // libraries as that would violate the structure of the DAG, in that
1528 // scenario they are required to link to them as well in a shared fashion.
1530 // Note that upstream rust libraries may contain native dependencies as
1531 // well, but they also can't depend on what we just started to add to the
1532 // link line. And finally upstream native libraries can't depend on anything
1533 // in this DAG so far because they're only dylibs and dylibs can only depend
1534 // on other dylibs (e.g., other native deps).
1536 // If -Zlink-native-libraries=false is set, then the assumption is that an
1537 // external build system already has the native dependencies defined, and it
1538 // will provide them to the linker itself.
1539 if sess.opts.debugging_opts.link_native_libraries {
1540 add_local_native_libraries(cmd, sess, codegen_results);
1542 add_upstream_rust_crates::<B>(cmd, sess, codegen_results, crate_type, tmpdir);
1543 if sess.opts.debugging_opts.link_native_libraries {
1544 add_upstream_native_libraries(cmd, sess, codegen_results, crate_type);
1548 /// Add sysroot and other globally set directories to the directory search list.
1549 fn add_library_search_dirs(cmd: &mut dyn Linker, sess: &Session, self_contained: bool) {
1550 // The default library location, we need this to find the runtime.
1551 // The location of crates will be determined as needed.
1552 let lib_path = sess.target_filesearch(PathKind::All).get_lib_path();
1553 cmd.include_path(&fix_windows_verbatim_for_gcc(&lib_path));
1555 // Special directory with libraries used only in self-contained linkage mode
1557 let lib_path = sess.target_filesearch(PathKind::All).get_self_contained_lib_path();
1558 cmd.include_path(&fix_windows_verbatim_for_gcc(&lib_path));
1562 /// Add options making relocation sections in the produced ELF files read-only
1563 /// and suppressing lazy binding.
1564 fn add_relro_args(cmd: &mut dyn Linker, sess: &Session) {
1565 match sess.opts.debugging_opts.relro_level.unwrap_or(sess.target.relro_level) {
1566 RelroLevel::Full => cmd.full_relro(),
1567 RelroLevel::Partial => cmd.partial_relro(),
1568 RelroLevel::Off => cmd.no_relro(),
1569 RelroLevel::None => {}
1573 /// Add library search paths used at runtime by dynamic linkers.
1575 cmd: &mut dyn Linker,
1577 codegen_results: &CodegenResults,
1578 out_filename: &Path,
1580 // FIXME (#2397): At some point we want to rpath our guesses as to
1581 // where extern libraries might live, based on the
1582 // addl_lib_search_paths
1583 if sess.opts.cg.rpath {
1584 let target_triple = sess.opts.target_triple.triple();
1585 let mut get_install_prefix_lib_path = || {
1586 let install_prefix = option_env!("CFG_PREFIX").expect("CFG_PREFIX");
1587 let tlib = filesearch::relative_target_lib_path(&sess.sysroot, target_triple);
1588 let mut path = PathBuf::from(install_prefix);
1593 let mut rpath_config = RPathConfig {
1594 used_crates: &codegen_results.crate_info.used_crates_dynamic,
1595 out_filename: out_filename.to_path_buf(),
1596 has_rpath: sess.target.has_rpath,
1597 is_like_osx: sess.target.is_like_osx,
1598 linker_is_gnu: sess.target.linker_is_gnu,
1599 get_install_prefix_lib_path: &mut get_install_prefix_lib_path,
1601 cmd.args(&rpath::get_rpath_flags(&mut rpath_config));
1605 /// Produce the linker command line containing linker path and arguments.
1606 /// `NO-OPT-OUT` marks the arguments that cannot be removed from the command line
1607 /// by the user without creating a custom target specification.
1608 /// `OBJECT-FILES` specify whether the arguments can add object files.
1609 /// `CUSTOMIZATION-POINT` means that arbitrary arguments defined by the user
1610 /// or by the target spec can be inserted here.
1611 /// `AUDIT-ORDER` - need to figure out whether the option is order-dependent or not.
1612 fn linker_with_args<'a, B: ArchiveBuilder<'a>>(
1614 flavor: LinkerFlavor,
1616 crate_type: CrateType,
1618 out_filename: &Path,
1619 codegen_results: &CodegenResults,
1622 let crt_objects_fallback = crt_objects_fallback(sess, crate_type);
1623 let base_cmd = get_linker(sess, path, flavor, crt_objects_fallback);
1624 // FIXME: Move `/LIBPATH` addition for uwp targets from the linker construction
1625 // to the linker args construction.
1626 assert!(base_cmd.get_args().is_empty() || sess.target.vendor == "uwp");
1627 let cmd = &mut *codegen_results.linker_info.to_linker(base_cmd, &sess, flavor, target_cpu);
1628 let link_output_kind = link_output_kind(sess, crate_type);
1630 // NO-OPT-OUT, OBJECT-FILES-MAYBE, CUSTOMIZATION-POINT
1631 add_pre_link_args(cmd, sess, flavor);
1633 // NO-OPT-OUT, OBJECT-FILES-NO
1634 add_apple_sdk(cmd, sess, flavor);
1637 add_link_script(cmd, sess, tmpdir, crate_type);
1639 // NO-OPT-OUT, OBJECT-FILES-NO, AUDIT-ORDER
1640 if sess.target.is_like_fuchsia && crate_type == CrateType::Executable {
1641 let prefix = if sess.opts.debugging_opts.sanitizer.contains(SanitizerSet::ADDRESS) {
1646 cmd.arg(format!("--dynamic-linker={}ld.so.1", prefix));
1649 // NO-OPT-OUT, OBJECT-FILES-NO, AUDIT-ORDER
1650 if sess.target.eh_frame_header {
1651 cmd.add_eh_frame_header();
1654 // NO-OPT-OUT, OBJECT-FILES-NO
1655 if crt_objects_fallback {
1656 cmd.no_crt_objects();
1659 // NO-OPT-OUT, OBJECT-FILES-YES
1660 add_pre_link_objects(cmd, sess, link_output_kind, crt_objects_fallback);
1662 // NO-OPT-OUT, OBJECT-FILES-NO, AUDIT-ORDER
1663 if sess.target.is_like_emscripten {
1665 cmd.arg(if sess.panic_strategy() == PanicStrategy::Abort {
1666 "DISABLE_EXCEPTION_CATCHING=1"
1668 "DISABLE_EXCEPTION_CATCHING=0"
1672 // OBJECT-FILES-YES, AUDIT-ORDER
1673 link_sanitizers(sess, crate_type, cmd);
1675 // OBJECT-FILES-NO, AUDIT-ORDER
1676 // Linker plugins should be specified early in the list of arguments
1677 // FIXME: How "early" exactly?
1678 cmd.linker_plugin_lto();
1680 // NO-OPT-OUT, OBJECT-FILES-NO, AUDIT-ORDER
1681 // FIXME: Order-dependent, at least relatively to other args adding searh directories.
1682 add_library_search_dirs(cmd, sess, crt_objects_fallback);
1685 add_local_crate_regular_objects(cmd, codegen_results);
1687 // NO-OPT-OUT, OBJECT-FILES-NO, AUDIT-ORDER
1688 cmd.output_filename(out_filename);
1690 // OBJECT-FILES-NO, AUDIT-ORDER
1691 if crate_type == CrateType::Executable && sess.target.is_like_windows {
1692 if let Some(ref s) = codegen_results.windows_subsystem {
1697 // NO-OPT-OUT, OBJECT-FILES-NO, AUDIT-ORDER
1698 // If we're building something like a dynamic library then some platforms
1699 // need to make sure that all symbols are exported correctly from the
1701 cmd.export_symbols(tmpdir, crate_type);
1704 add_local_crate_metadata_objects(cmd, crate_type, codegen_results);
1707 add_local_crate_allocator_objects(cmd, codegen_results);
1709 // OBJECT-FILES-NO, AUDIT-ORDER
1710 // FIXME: Order dependent, applies to the following objects. Where should it be placed?
1711 // Try to strip as much out of the generated object by removing unused
1712 // sections if possible. See more comments in linker.rs
1713 if !sess.link_dead_code() {
1714 let keep_metadata = crate_type == CrateType::Dylib;
1715 cmd.gc_sections(keep_metadata);
1718 // NO-OPT-OUT, OBJECT-FILES-NO, AUDIT-ORDER
1719 cmd.set_output_kind(link_output_kind, out_filename);
1721 // OBJECT-FILES-NO, AUDIT-ORDER
1722 add_relro_args(cmd, sess);
1724 // OBJECT-FILES-NO, AUDIT-ORDER
1725 // Pass optimization flags down to the linker.
1728 // OBJECT-FILES-NO, AUDIT-ORDER
1729 // Pass debuginfo and strip flags down to the linker.
1730 cmd.debuginfo(sess.opts.debugging_opts.strip);
1732 // OBJECT-FILES-NO, AUDIT-ORDER
1733 // We want to prevent the compiler from accidentally leaking in any system libraries,
1734 // so by default we tell linkers not to link to any default libraries.
1735 if !sess.opts.cg.default_linker_libraries && sess.target.no_default_libraries {
1736 cmd.no_default_libraries();
1740 link_local_crate_native_libs_and_dependent_crate_libs::<B>(
1748 // OBJECT-FILES-NO, AUDIT-ORDER
1749 if sess.opts.cg.profile_generate.enabled() || sess.instrument_coverage() {
1753 // OBJECT-FILES-NO, AUDIT-ORDER
1754 if sess.opts.cg.control_flow_guard != CFGuard::Disabled {
1755 cmd.control_flow_guard();
1758 // OBJECT-FILES-NO, AUDIT-ORDER
1759 add_rpath_args(cmd, sess, codegen_results, out_filename);
1761 // OBJECT-FILES-MAYBE, CUSTOMIZATION-POINT
1762 add_user_defined_link_args(cmd, sess, codegen_results);
1764 // NO-OPT-OUT, OBJECT-FILES-NO, AUDIT-ORDER
1767 // NO-OPT-OUT, OBJECT-FILES-MAYBE, CUSTOMIZATION-POINT
1768 add_late_link_args(cmd, sess, flavor, crate_type, codegen_results);
1770 // NO-OPT-OUT, OBJECT-FILES-YES
1771 add_post_link_objects(cmd, sess, link_output_kind, crt_objects_fallback);
1773 // NO-OPT-OUT, OBJECT-FILES-MAYBE, CUSTOMIZATION-POINT
1774 add_post_link_args(cmd, sess, flavor);
1779 /// # Native library linking
1781 /// User-supplied library search paths (-L on the command line). These are the same paths used to
1782 /// find Rust crates, so some of them may have been added already by the previous crate linking
1783 /// code. This only allows them to be found at compile time so it is still entirely up to outside
1784 /// forces to make sure that library can be found at runtime.
1786 /// Also note that the native libraries linked here are only the ones located in the current crate.
1787 /// Upstream crates with native library dependencies may have their native library pulled in above.
1788 fn add_local_native_libraries(
1789 cmd: &mut dyn Linker,
1791 codegen_results: &CodegenResults,
1793 let filesearch = sess.target_filesearch(PathKind::All);
1794 for search_path in filesearch.search_paths() {
1795 match search_path.kind {
1796 PathKind::Framework => {
1797 cmd.framework_path(&search_path.dir);
1800 cmd.include_path(&fix_windows_verbatim_for_gcc(&search_path.dir));
1806 codegen_results.crate_info.used_libraries.iter().filter(|l| relevant_lib(sess, l));
1808 let search_path = archive_search_paths(sess);
1809 for lib in relevant_libs {
1810 let name = match lib.name {
1815 NativeLibKind::Dylib | NativeLibKind::Unspecified => cmd.link_dylib(name),
1816 NativeLibKind::Framework => cmd.link_framework(name),
1817 NativeLibKind::StaticNoBundle => cmd.link_staticlib(name),
1818 NativeLibKind::StaticBundle => cmd.link_whole_staticlib(name, &search_path),
1819 NativeLibKind::RawDylib => {
1820 // FIXME(#58713): Proper handling for raw dylibs.
1821 bug!("raw_dylib feature not yet implemented");
1827 /// # Rust Crate linking
1829 /// Rust crates are not considered at all when creating an rlib output. All dependencies will be
1830 /// linked when producing the final output (instead of the intermediate rlib version).
1831 fn add_upstream_rust_crates<'a, B: ArchiveBuilder<'a>>(
1832 cmd: &mut dyn Linker,
1834 codegen_results: &CodegenResults,
1835 crate_type: CrateType,
1838 // All of the heavy lifting has previously been accomplished by the
1839 // dependency_format module of the compiler. This is just crawling the
1840 // output of that module, adding crates as necessary.
1842 // Linking to a rlib involves just passing it to the linker (the linker
1843 // will slurp up the object files inside), and linking to a dynamic library
1844 // involves just passing the right -l flag.
1846 let (_, data) = codegen_results
1850 .find(|(ty, _)| *ty == crate_type)
1851 .expect("failed to find crate type in dependency format list");
1853 // Invoke get_used_crates to ensure that we get a topological sorting of
1855 let deps = &codegen_results.crate_info.used_crates_dynamic;
1857 // There's a few internal crates in the standard library (aka libcore and
1858 // libstd) which actually have a circular dependence upon one another. This
1859 // currently arises through "weak lang items" where libcore requires things
1860 // like `rust_begin_unwind` but libstd ends up defining it. To get this
1861 // circular dependence to work correctly in all situations we'll need to be
1862 // sure to correctly apply the `--start-group` and `--end-group` options to
1863 // GNU linkers, otherwise if we don't use any other symbol from the standard
1864 // library it'll get discarded and the whole application won't link.
1866 // In this loop we're calculating the `group_end`, after which crate to
1867 // pass `--end-group` and `group_start`, before which crate to pass
1868 // `--start-group`. We currently do this by passing `--end-group` after
1869 // the first crate (when iterating backwards) that requires a lang item
1870 // defined somewhere else. Once that's set then when we've defined all the
1871 // necessary lang items we'll pass `--start-group`.
1873 // Note that this isn't amazing logic for now but it should do the trick
1874 // for the current implementation of the standard library.
1875 let mut group_end = None;
1876 let mut group_start = None;
1877 // Crates available for linking thus far.
1878 let mut available = FxHashSet::default();
1879 // Crates required to satisfy dependencies discovered so far.
1880 let mut required = FxHashSet::default();
1882 let info = &codegen_results.crate_info;
1883 for &(cnum, _) in deps.iter().rev() {
1884 if let Some(missing) = info.missing_lang_items.get(&cnum) {
1885 let missing_crates = missing.iter().map(|i| info.lang_item_to_crate.get(i).copied());
1886 required.extend(missing_crates);
1889 required.insert(Some(cnum));
1890 available.insert(Some(cnum));
1892 if required.len() > available.len() && group_end.is_none() {
1893 group_end = Some(cnum);
1895 if required.len() == available.len() && group_end.is_some() {
1896 group_start = Some(cnum);
1901 // If we didn't end up filling in all lang items from upstream crates then
1902 // we'll be filling it in with our crate. This probably means we're the
1903 // standard library itself, so skip this for now.
1904 if group_end.is_some() && group_start.is_none() {
1908 let mut compiler_builtins = None;
1910 for &(cnum, _) in deps.iter() {
1911 if group_start == Some(cnum) {
1915 // We may not pass all crates through to the linker. Some crates may
1916 // appear statically in an existing dylib, meaning we'll pick up all the
1917 // symbols from the dylib.
1918 let src = &codegen_results.crate_info.used_crate_source[&cnum];
1919 match data[cnum.as_usize() - 1] {
1920 _ if codegen_results.crate_info.profiler_runtime == Some(cnum) => {
1921 add_static_crate::<B>(cmd, sess, codegen_results, tmpdir, crate_type, cnum);
1923 // compiler-builtins are always placed last to ensure that they're
1924 // linked correctly.
1925 _ if codegen_results.crate_info.compiler_builtins == Some(cnum) => {
1926 assert!(compiler_builtins.is_none());
1927 compiler_builtins = Some(cnum);
1929 Linkage::NotLinked | Linkage::IncludedFromDylib => {}
1930 Linkage::Static => {
1931 add_static_crate::<B>(cmd, sess, codegen_results, tmpdir, crate_type, cnum);
1933 Linkage::Dynamic => add_dynamic_crate(cmd, sess, &src.dylib.as_ref().unwrap().0),
1936 if group_end == Some(cnum) {
1941 // compiler-builtins are always placed last to ensure that they're
1942 // linked correctly.
1943 // We must always link the `compiler_builtins` crate statically. Even if it
1944 // was already "included" in a dylib (e.g., `libstd` when `-C prefer-dynamic`
1946 if let Some(cnum) = compiler_builtins {
1947 add_static_crate::<B>(cmd, sess, codegen_results, tmpdir, crate_type, cnum);
1950 // Converts a library file-stem into a cc -l argument
1951 fn unlib<'a>(target: &Target, stem: &'a str) -> &'a str {
1952 if stem.starts_with("lib") && !target.is_like_windows { &stem[3..] } else { stem }
1955 // Adds the static "rlib" versions of all crates to the command line.
1956 // There's a bit of magic which happens here specifically related to LTO and
1957 // dynamic libraries. Specifically:
1959 // * For LTO, we remove upstream object files.
1960 // * For dylibs we remove metadata and bytecode from upstream rlibs
1962 // When performing LTO, almost(*) all of the bytecode from the upstream
1963 // libraries has already been included in our object file output. As a
1964 // result we need to remove the object files in the upstream libraries so
1965 // the linker doesn't try to include them twice (or whine about duplicate
1966 // symbols). We must continue to include the rest of the rlib, however, as
1967 // it may contain static native libraries which must be linked in.
1969 // (*) Crates marked with `#![no_builtins]` don't participate in LTO and
1970 // their bytecode wasn't included. The object files in those libraries must
1971 // still be passed to the linker.
1973 // When making a dynamic library, linkers by default don't include any
1974 // object files in an archive if they're not necessary to resolve the link.
1975 // We basically want to convert the archive (rlib) to a dylib, though, so we
1976 // *do* want everything included in the output, regardless of whether the
1977 // linker thinks it's needed or not. As a result we must use the
1978 // --whole-archive option (or the platform equivalent). When using this
1979 // option the linker will fail if there are non-objects in the archive (such
1980 // as our own metadata and/or bytecode). All in all, for rlibs to be
1981 // entirely included in dylibs, we need to remove all non-object files.
1983 // Note, however, that if we're not doing LTO or we're not producing a dylib
1984 // (aka we're making an executable), we can just pass the rlib blindly to
1985 // the linker (fast) because it's fine if it's not actually included as
1986 // we're at the end of the dependency chain.
1987 fn add_static_crate<'a, B: ArchiveBuilder<'a>>(
1988 cmd: &mut dyn Linker,
1990 codegen_results: &CodegenResults,
1992 crate_type: CrateType,
1995 let src = &codegen_results.crate_info.used_crate_source[&cnum];
1996 let cratepath = &src.rlib.as_ref().unwrap().0;
1998 // See the comment above in `link_staticlib` and `link_rlib` for why if
1999 // there's a static library that's not relevant we skip all object
2001 let native_libs = &codegen_results.crate_info.native_libraries[&cnum];
2002 let skip_native = native_libs
2004 .any(|lib| lib.kind == NativeLibKind::StaticBundle && !relevant_lib(sess, lib));
2006 if (!are_upstream_rust_objects_already_included(sess)
2007 || ignored_for_lto(sess, &codegen_results.crate_info, cnum))
2008 && crate_type != CrateType::Dylib
2011 cmd.link_rlib(&fix_windows_verbatim_for_gcc(cratepath));
2015 let dst = tmpdir.join(cratepath.file_name().unwrap());
2016 let name = cratepath.file_name().unwrap().to_str().unwrap();
2017 let name = &name[3..name.len() - 5]; // chop off lib/.rlib
2019 sess.prof.generic_activity_with_arg("link_altering_rlib", name).run(|| {
2020 let mut archive = <B as ArchiveBuilder>::new(sess, &dst, Some(cratepath));
2021 archive.update_symbols();
2023 let mut any_objects = false;
2024 for f in archive.src_files() {
2025 if f == METADATA_FILENAME {
2026 archive.remove_file(&f);
2030 let canonical = f.replace("-", "_");
2031 let canonical_name = name.replace("-", "_");
2033 let is_rust_object =
2034 canonical.starts_with(&canonical_name) && looks_like_rust_object_file(&f);
2036 // If we've been requested to skip all native object files
2037 // (those not generated by the rust compiler) then we can skip
2038 // this file. See above for why we may want to do this.
2039 let skip_because_cfg_say_so = skip_native && !is_rust_object;
2041 // If we're performing LTO and this is a rust-generated object
2042 // file, then we don't need the object file as it's part of the
2043 // LTO module. Note that `#![no_builtins]` is excluded from LTO,
2044 // though, so we let that object file slide.
2045 let skip_because_lto = are_upstream_rust_objects_already_included(sess)
2047 && (sess.target.no_builtins
2048 || !codegen_results.crate_info.is_no_builtins.contains(&cnum));
2050 if skip_because_cfg_say_so || skip_because_lto {
2051 archive.remove_file(&f);
2062 // If we're creating a dylib, then we need to include the
2063 // whole of each object in our archive into that artifact. This is
2064 // because a `dylib` can be reused as an intermediate artifact.
2066 // Note, though, that we don't want to include the whole of a
2067 // compiler-builtins crate (e.g., compiler-rt) because it'll get
2068 // repeatedly linked anyway.
2069 if crate_type == CrateType::Dylib
2070 && codegen_results.crate_info.compiler_builtins != Some(cnum)
2072 cmd.link_whole_rlib(&fix_windows_verbatim_for_gcc(&dst));
2074 cmd.link_rlib(&fix_windows_verbatim_for_gcc(&dst));
2079 // Same thing as above, but for dynamic crates instead of static crates.
2080 fn add_dynamic_crate(cmd: &mut dyn Linker, sess: &Session, cratepath: &Path) {
2081 // Just need to tell the linker about where the library lives and
2083 let parent = cratepath.parent();
2084 if let Some(dir) = parent {
2085 cmd.include_path(&fix_windows_verbatim_for_gcc(dir));
2087 let filestem = cratepath.file_stem().unwrap().to_str().unwrap();
2088 cmd.link_rust_dylib(
2089 Symbol::intern(&unlib(&sess.target, filestem)),
2090 parent.unwrap_or_else(|| Path::new("")),
2095 /// Link in all of our upstream crates' native dependencies. Remember that all of these upstream
2096 /// native dependencies are all non-static dependencies. We've got two cases then:
2098 /// 1. The upstream crate is an rlib. In this case we *must* link in the native dependency because
2099 /// the rlib is just an archive.
2101 /// 2. The upstream crate is a dylib. In order to use the dylib, we have to have the dependency
2102 /// present on the system somewhere. Thus, we don't gain a whole lot from not linking in the
2103 /// dynamic dependency to this crate as well.
2105 /// The use case for this is a little subtle. In theory the native dependencies of a crate are
2106 /// purely an implementation detail of the crate itself, but the problem arises with generic and
2107 /// inlined functions. If a generic function calls a native function, then the generic function
2108 /// must be instantiated in the target crate, meaning that the native symbol must also be resolved
2109 /// in the target crate.
2110 fn add_upstream_native_libraries(
2111 cmd: &mut dyn Linker,
2113 codegen_results: &CodegenResults,
2114 crate_type: CrateType,
2116 // Be sure to use a topological sorting of crates because there may be
2117 // interdependencies between native libraries. When passing -nodefaultlibs,
2118 // for example, almost all native libraries depend on libc, so we have to
2119 // make sure that's all the way at the right (liblibc is near the base of
2120 // the dependency chain).
2122 // This passes RequireStatic, but the actual requirement doesn't matter,
2123 // we're just getting an ordering of crate numbers, we're not worried about
2125 let (_, data) = codegen_results
2129 .find(|(ty, _)| *ty == crate_type)
2130 .expect("failed to find crate type in dependency format list");
2132 let crates = &codegen_results.crate_info.used_crates_static;
2133 for &(cnum, _) in crates {
2134 for lib in codegen_results.crate_info.native_libraries[&cnum].iter() {
2135 let name = match lib.name {
2139 if !relevant_lib(sess, &lib) {
2143 NativeLibKind::Dylib | NativeLibKind::Unspecified => cmd.link_dylib(name),
2144 NativeLibKind::Framework => cmd.link_framework(name),
2145 NativeLibKind::StaticNoBundle => {
2146 // Link "static-nobundle" native libs only if the crate they originate from
2147 // is being linked statically to the current crate. If it's linked dynamically
2148 // or is an rlib already included via some other dylib crate, the symbols from
2149 // native libs will have already been included in that dylib.
2150 if data[cnum.as_usize() - 1] == Linkage::Static {
2151 cmd.link_staticlib(name)
2154 // ignore statically included native libraries here as we've
2155 // already included them when we included the rust library
2157 NativeLibKind::StaticBundle => {}
2158 NativeLibKind::RawDylib => {
2159 // FIXME(#58713): Proper handling for raw dylibs.
2160 bug!("raw_dylib feature not yet implemented");
2167 fn relevant_lib(sess: &Session, lib: &NativeLib) -> bool {
2169 Some(ref cfg) => rustc_attr::cfg_matches(cfg, &sess.parse_sess, None),
2174 fn are_upstream_rust_objects_already_included(sess: &Session) -> bool {
2176 config::Lto::Fat => true,
2177 config::Lto::Thin => {
2178 // If we defer LTO to the linker, we haven't run LTO ourselves, so
2179 // any upstream object files have not been copied yet.
2180 !sess.opts.cg.linker_plugin_lto.enabled()
2182 config::Lto::No | config::Lto::ThinLocal => false,
2186 fn add_apple_sdk(cmd: &mut dyn Linker, sess: &Session, flavor: LinkerFlavor) {
2187 let arch = &sess.target.arch;
2188 let os = &sess.target.os;
2189 let llvm_target = &sess.target.llvm_target;
2190 if sess.target.vendor != "apple"
2191 || !matches!(os.as_str(), "ios" | "tvos")
2192 || flavor != LinkerFlavor::Gcc
2196 let sdk_name = match (arch.as_str(), os.as_str()) {
2197 ("aarch64", "tvos") => "appletvos",
2198 ("x86_64", "tvos") => "appletvsimulator",
2199 ("arm", "ios") => "iphoneos",
2200 ("aarch64", "ios") if llvm_target.contains("macabi") => "macosx",
2201 ("aarch64", "ios") if llvm_target.contains("sim") => "iphonesimulator",
2202 ("aarch64", "ios") => "iphoneos",
2203 ("x86", "ios") => "iphonesimulator",
2204 ("x86_64", "ios") if llvm_target.contains("macabi") => "macosx",
2205 ("x86_64", "ios") => "iphonesimulator",
2207 sess.err(&format!("unsupported arch `{}` for os `{}`", arch, os));
2211 let sdk_root = match get_apple_sdk_root(sdk_name) {
2218 if llvm_target.contains("macabi") {
2219 cmd.args(&["-target", llvm_target])
2221 let arch_name = llvm_target.split('-').next().expect("LLVM target must have a hyphen");
2222 cmd.args(&["-arch", arch_name])
2224 cmd.args(&["-isysroot", &sdk_root, "-Wl,-syslibroot", &sdk_root]);
2227 fn get_apple_sdk_root(sdk_name: &str) -> Result<String, String> {
2228 // Following what clang does
2229 // (https://github.com/llvm/llvm-project/blob/
2230 // 296a80102a9b72c3eda80558fb78a3ed8849b341/clang/lib/Driver/ToolChains/Darwin.cpp#L1661-L1678)
2231 // to allow the SDK path to be set. (For clang, xcrun sets
2232 // SDKROOT; for rustc, the user or build system can set it, or we
2233 // can fall back to checking for xcrun on PATH.)
2234 if let Ok(sdkroot) = env::var("SDKROOT") {
2235 let p = Path::new(&sdkroot);
2237 // Ignore `SDKROOT` if it's clearly set for the wrong platform.
2239 if sdkroot.contains("TVSimulator.platform")
2240 || sdkroot.contains("MacOSX.platform") => {}
2242 if sdkroot.contains("TVOS.platform") || sdkroot.contains("MacOSX.platform") => {}
2244 if sdkroot.contains("iPhoneSimulator.platform")
2245 || sdkroot.contains("MacOSX.platform") => {}
2247 if sdkroot.contains("iPhoneOS.platform") || sdkroot.contains("MacOSX.platform") => {
2250 if sdkroot.contains("iPhoneOS.platform")
2251 || sdkroot.contains("iPhoneSimulator.platform") => {}
2252 // Ignore `SDKROOT` if it's not a valid path.
2253 _ if !p.is_absolute() || p == Path::new("/") || !p.exists() => {}
2254 _ => return Ok(sdkroot),
2258 Command::new("xcrun").arg("--show-sdk-path").arg("-sdk").arg(sdk_name).output().and_then(
2260 if output.status.success() {
2261 Ok(String::from_utf8(output.stdout).unwrap())
2263 let error = String::from_utf8(output.stderr);
2264 let error = format!("process exit with error: {}", error.unwrap());
2265 Err(io::Error::new(io::ErrorKind::Other, &error[..]))
2271 Ok(output) => Ok(output.trim().to_string()),
2272 Err(e) => Err(format!("failed to get {} SDK path: {}", sdk_name, e)),