1 use rustc::middle::cstore::{EncodedMetadata, LibSource, NativeLibrary, NativeLibraryKind};
2 use rustc::middle::dependency_format::Linkage;
3 use rustc::session::config::{
4 self, DebugInfo, OutputFilenames, OutputType, PrintRequest, Sanitizer,
6 use rustc::session::search_paths::PathKind;
7 /// For all the linkers we support, and information they might
8 /// need out of the shared crate context before we get rid of it.
9 use rustc::session::{filesearch, Session};
10 use rustc_data_structures::fx::FxHashSet;
11 use rustc_fs_util::fix_windows_verbatim_for_gcc;
12 use rustc_hir::def_id::CrateNum;
13 use rustc_span::symbol::Symbol;
14 use rustc_target::spec::{LinkerFlavor, PanicStrategy, RelroLevel};
16 use super::archive::ArchiveBuilder;
17 use super::command::Command;
18 use super::linker::Linker;
19 use super::rpath::{self, RPathConfig};
21 looks_like_rust_object_file, CodegenResults, CrateInfo, METADATA_FILENAME,
22 RLIB_BYTECODE_EXTENSION,
25 use cc::windows_registry;
26 use tempfile::{Builder as TempFileBuilder, TempDir};
31 use std::ffi::OsString;
35 use std::path::{Path, PathBuf};
36 use std::process::{ExitStatus, Output, Stdio};
39 pub use rustc_codegen_utils::link::*;
41 pub fn remove(sess: &Session, path: &Path) {
42 if let Err(e) = fs::remove_file(path) {
43 sess.err(&format!("failed to remove {}: {}", path.display(), e));
47 /// Performs the linkage portion of the compilation phase. This will generate all
48 /// of the requested outputs for this compilation session.
49 pub fn link_binary<'a, B: ArchiveBuilder<'a>>(
51 codegen_results: &CodegenResults,
52 outputs: &OutputFilenames,
56 let _timer = sess.timer("link_binary");
57 let output_metadata = sess.opts.output_types.contains_key(&OutputType::Metadata);
58 for &crate_type in sess.crate_types.borrow().iter() {
59 // Ignore executable crates if we have -Z no-codegen, as they will error.
60 if (sess.opts.debugging_opts.no_codegen || !sess.opts.output_types.should_codegen())
62 && crate_type == config::CrateType::Executable
67 if invalid_output_for_target(sess, crate_type) {
69 "invalid output type `{:?}` for target os `{}`",
71 sess.opts.target_triple
75 sess.time("link_binary_check_files_are_writeable", || {
76 for obj in codegen_results.modules.iter().filter_map(|m| m.object.as_ref()) {
77 check_file_is_writeable(obj, sess);
81 let tmpdir = TempFileBuilder::new()
84 .unwrap_or_else(|err| sess.fatal(&format!("couldn't create a temp dir: {}", err)));
86 if outputs.outputs.should_codegen() {
87 let out_filename = out_filename(sess, crate_type, outputs, crate_name);
89 config::CrateType::Rlib => {
90 let _timer = sess.timer("link_rlib");
100 config::CrateType::Staticlib => {
101 link_staticlib::<B>(sess, codegen_results, &out_filename, &tmpdir);
114 if sess.opts.json_artifact_notifications {
115 sess.parse_sess.span_diagnostic.emit_artifact_notification(&out_filename, "link");
119 if sess.opts.cg.save_temps {
120 let _ = tmpdir.into_path();
124 // Remove the temporary object file and metadata if we aren't saving temps
125 sess.time("link_binary_remove_temps", || {
126 if !sess.opts.cg.save_temps {
127 if sess.opts.output_types.should_codegen()
128 && !preserve_objects_for_their_debuginfo(sess)
130 for obj in codegen_results.modules.iter().filter_map(|m| m.object.as_ref()) {
134 for obj in codegen_results.modules.iter().filter_map(|m| m.bytecode_compressed.as_ref())
138 if let Some(ref metadata_module) = codegen_results.metadata_module {
139 if let Some(ref obj) = metadata_module.object {
143 if let Some(ref allocator_module) = codegen_results.allocator_module {
144 if let Some(ref obj) = allocator_module.object {
147 if let Some(ref bc) = allocator_module.bytecode_compressed {
155 // The third parameter is for env vars, used on windows to set up the
156 // path for MSVC to find its DLLs, and gcc to find its bundled
158 pub fn get_linker(sess: &Session, linker: &Path, flavor: LinkerFlavor) -> (PathBuf, Command) {
159 let msvc_tool = windows_registry::find_tool(&sess.opts.target_triple.triple(), "link.exe");
161 // If our linker looks like a batch script on Windows then to execute this
162 // we'll need to spawn `cmd` explicitly. This is primarily done to handle
163 // emscripten where the linker is `emcc.bat` and needs to be spawned as
164 // `cmd /c emcc.bat ...`.
166 // This worked historically but is needed manually since #42436 (regression
167 // was tagged as #42791) and some more info can be found on #44443 for
168 // emscripten itself.
169 let mut cmd = match linker.to_str() {
170 Some(linker) if cfg!(windows) && linker.ends_with(".bat") => Command::bat_script(linker),
172 LinkerFlavor::Lld(f) => Command::lld(linker, f),
174 if sess.opts.cg.linker.is_none() && sess.target.target.options.linker.is_none() =>
176 Command::new(msvc_tool.as_ref().map(|t| t.path()).unwrap_or(linker))
178 _ => Command::new(linker),
182 // UWP apps have API restrictions enforced during Store submissions.
183 // To comply with the Windows App Certification Kit,
184 // MSVC needs to link with the Store versions of the runtime libraries (vcruntime, msvcrt, etc).
185 let t = &sess.target.target;
186 if flavor == LinkerFlavor::Msvc && t.target_vendor == "uwp" {
187 if let Some(ref tool) = msvc_tool {
188 let original_path = tool.path();
189 if let Some(ref root_lib_path) = original_path.ancestors().skip(4).next() {
190 let arch = match t.arch.as_str() {
191 "x86_64" => Some("x64".to_string()),
192 "x86" => Some("x86".to_string()),
193 "aarch64" => Some("arm64".to_string()),
196 if let Some(ref a) = arch {
197 let mut arg = OsString::from("/LIBPATH:");
198 arg.push(format!("{}\\lib\\{}\\store", root_lib_path.display(), a.to_string()));
201 warn!("arch is not supported");
204 warn!("MSVC root path lib location not found");
207 warn!("link.exe not found");
211 // The compiler's sysroot often has some bundled tools, so add it to the
212 // PATH for the child.
213 let mut new_path = sess.host_filesearch(PathKind::All).get_tools_search_paths();
214 let mut msvc_changed_path = false;
215 if sess.target.target.options.is_like_msvc {
216 if let Some(ref tool) = msvc_tool {
217 cmd.args(tool.args());
218 for &(ref k, ref v) in tool.env() {
220 new_path.extend(env::split_paths(v));
221 msvc_changed_path = true;
229 if !msvc_changed_path {
230 if let Some(path) = env::var_os("PATH") {
231 new_path.extend(env::split_paths(&path));
234 cmd.env("PATH", env::join_paths(new_path).unwrap());
236 (linker.to_path_buf(), cmd)
239 pub fn each_linked_rlib(
241 f: &mut dyn FnMut(CrateNum, &Path),
242 ) -> Result<(), String> {
243 let crates = info.used_crates_static.iter();
245 for (ty, list) in info.dependency_formats.iter() {
247 config::CrateType::Executable
248 | config::CrateType::Staticlib
249 | config::CrateType::Cdylib
250 | config::CrateType::ProcMacro => {
257 let fmts = match fmts {
259 None => return Err("could not find formats for rlibs".to_string()),
261 for &(cnum, ref path) in crates {
262 match fmts.get(cnum.as_usize() - 1) {
263 Some(&Linkage::NotLinked) | Some(&Linkage::IncludedFromDylib) => continue,
265 None => return Err("could not find formats for rlibs".to_string()),
267 let name = &info.crate_name[&cnum];
268 let path = match *path {
269 LibSource::Some(ref p) => p,
270 LibSource::MetadataOnly => {
272 "could not find rlib for: `{}`, found rmeta (metadata) file",
276 LibSource::None => return Err(format!("could not find rlib for: `{}`", name)),
283 /// We use a temp directory here to avoid races between concurrent rustc processes,
284 /// such as builds in the same directory using the same filename for metadata while
285 /// building an `.rlib` (stomping over one another), or writing an `.rmeta` into a
286 /// directory being searched for `extern crate` (observing an incomplete file).
287 /// The returned path is the temporary file containing the complete metadata.
288 pub fn emit_metadata<'a>(
290 metadata: &EncodedMetadata,
293 let out_filename = tmpdir.path().join(METADATA_FILENAME);
294 let result = fs::write(&out_filename, &metadata.raw_data);
296 if let Err(e) = result {
297 sess.fatal(&format!("failed to write {}: {}", out_filename.display(), e));
305 // An rlib in its current incarnation is essentially a renamed .a file. The
306 // rlib primarily contains the object file of the crate, but it also contains
307 // all of the object files from native libraries. This is done by unzipping
308 // native libraries and inserting all of the contents into this archive.
309 fn link_rlib<'a, B: ArchiveBuilder<'a>>(
311 codegen_results: &CodegenResults,
316 info!("preparing rlib to {:?}", out_filename);
317 let mut ab = <B as ArchiveBuilder>::new(sess, out_filename, None);
319 for obj in codegen_results.modules.iter().filter_map(|m| m.object.as_ref()) {
323 // Note that in this loop we are ignoring the value of `lib.cfg`. That is,
324 // we may not be configured to actually include a static library if we're
325 // adding it here. That's because later when we consume this rlib we'll
326 // decide whether we actually needed the static library or not.
328 // To do this "correctly" we'd need to keep track of which libraries added
329 // which object files to the archive. We don't do that here, however. The
330 // #[link(cfg(..))] feature is unstable, though, and only intended to get
331 // liblibc working. In that sense the check below just indicates that if
332 // there are any libraries we want to omit object files for at link time we
333 // just exclude all custom object files.
335 // Eventually if we want to stabilize or flesh out the #[link(cfg(..))]
336 // feature then we'll need to figure out how to record what objects were
337 // loaded from the libraries found here and then encode that into the
338 // metadata of the rlib we're generating somehow.
339 for lib in codegen_results.crate_info.used_libraries.iter() {
341 NativeLibraryKind::NativeStatic => {}
342 NativeLibraryKind::NativeStaticNobundle
343 | NativeLibraryKind::NativeFramework
344 | NativeLibraryKind::NativeRawDylib
345 | NativeLibraryKind::NativeUnknown => continue,
347 if let Some(name) = lib.name {
348 ab.add_native_library(name);
352 // After adding all files to the archive, we need to update the
353 // symbol table of the archive.
356 // Note that it is important that we add all of our non-object "magical
357 // files" *after* all of the object files in the archive. The reason for
358 // this is as follows:
360 // * When performing LTO, this archive will be modified to remove
361 // objects from above. The reason for this is described below.
363 // * When the system linker looks at an archive, it will attempt to
364 // determine the architecture of the archive in order to see whether its
367 // The algorithm for this detection is: iterate over the files in the
368 // archive. Skip magical SYMDEF names. Interpret the first file as an
369 // object file. Read architecture from the object file.
371 // * As one can probably see, if "metadata" and "foo.bc" were placed
372 // before all of the objects, then the architecture of this archive would
373 // not be correctly inferred once 'foo.o' is removed.
375 // Basically, all this means is that this code should not move above the
378 RlibFlavor::Normal => {
379 // Instead of putting the metadata in an object file section, rlibs
380 // contain the metadata in a separate file.
381 ab.add_file(&emit_metadata(sess, &codegen_results.metadata, tmpdir));
383 // For LTO purposes, the bytecode of this library is also inserted
386 codegen_results.modules.iter().filter_map(|m| m.bytecode_compressed.as_ref())
388 ab.add_file(bytecode);
391 // After adding all files to the archive, we need to update the
392 // symbol table of the archive. This currently dies on macOS (see
393 // #11162), and isn't necessary there anyway
394 if !sess.target.target.options.is_like_osx {
399 RlibFlavor::StaticlibBase => {
400 let obj = codegen_results.allocator_module.as_ref().and_then(|m| m.object.as_ref());
401 if let Some(obj) = obj {
410 // Create a static archive
412 // This is essentially the same thing as an rlib, but it also involves adding
413 // all of the upstream crates' objects into the archive. This will slurp in
414 // all of the native libraries of upstream dependencies as well.
416 // Additionally, there's no way for us to link dynamic libraries, so we warn
417 // about all dynamic library dependencies that they're not linked in.
419 // There's no need to include metadata in a static archive, so ensure to not
420 // link in the metadata object file (and also don't prepare the archive with a
422 fn link_staticlib<'a, B: ArchiveBuilder<'a>>(
424 codegen_results: &CodegenResults,
429 link_rlib::<B>(sess, codegen_results, RlibFlavor::StaticlibBase, out_filename, tempdir);
430 let mut all_native_libs = vec![];
432 let res = each_linked_rlib(&codegen_results.crate_info, &mut |cnum, path| {
433 let name = &codegen_results.crate_info.crate_name[&cnum];
434 let native_libs = &codegen_results.crate_info.native_libraries[&cnum];
436 // Here when we include the rlib into our staticlib we need to make a
437 // decision whether to include the extra object files along the way.
438 // These extra object files come from statically included native
439 // libraries, but they may be cfg'd away with #[link(cfg(..))].
441 // This unstable feature, though, only needs liblibc to work. The only
442 // use case there is where musl is statically included in liblibc.rlib,
443 // so if we don't want the included version we just need to skip it. As
444 // a result the logic here is that if *any* linked library is cfg'd away
445 // we just skip all object files.
447 // Clearly this is not sufficient for a general purpose feature, and
448 // we'd want to read from the library's metadata to determine which
449 // object files come from where and selectively skip them.
450 let skip_object_files = native_libs
452 .any(|lib| lib.kind == NativeLibraryKind::NativeStatic && !relevant_lib(sess, lib));
456 are_upstream_rust_objects_already_included(sess)
457 && !ignored_for_lto(sess, &codegen_results.crate_info, cnum),
462 all_native_libs.extend(codegen_results.crate_info.native_libraries[&cnum].iter().cloned());
464 if let Err(e) = res {
471 if !all_native_libs.is_empty() {
472 if sess.opts.prints.contains(&PrintRequest::NativeStaticLibs) {
473 print_native_static_libs(sess, &all_native_libs);
478 // Create a dynamic library or executable
480 // This will invoke the system linker/cc to create the resulting file. This
481 // links to all upstream files as well.
482 fn link_natively<'a, B: ArchiveBuilder<'a>>(
484 crate_type: config::CrateType,
486 codegen_results: &CodegenResults,
490 info!("preparing {:?} to {:?}", crate_type, out_filename);
491 let (linker, flavor) = linker_and_flavor(sess);
493 // The invocations of cc share some flags across platforms
494 let (pname, mut cmd) = get_linker(sess, &linker, flavor);
496 if let Some(args) = sess.target.target.options.pre_link_args.get(&flavor) {
499 if let Some(args) = sess.target.target.options.pre_link_args_crt.get(&flavor) {
500 if sess.crt_static() {
504 if let Some(ref args) = sess.opts.debugging_opts.pre_link_args {
507 cmd.args(&sess.opts.debugging_opts.pre_link_arg);
509 if sess.target.target.options.is_like_fuchsia {
510 let prefix = match sess.opts.debugging_opts.sanitizer {
511 Some(Sanitizer::Address) => "asan/",
514 cmd.arg(format!("--dynamic-linker={}ld.so.1", prefix));
517 let pre_link_objects = if crate_type == config::CrateType::Executable {
518 &sess.target.target.options.pre_link_objects_exe
520 &sess.target.target.options.pre_link_objects_dll
522 for obj in pre_link_objects {
523 cmd.arg(get_file_path(sess, obj));
526 if crate_type == config::CrateType::Executable && sess.crt_static() {
527 for obj in &sess.target.target.options.pre_link_objects_exe_crt {
528 cmd.arg(get_file_path(sess, obj));
532 if sess.target.target.options.is_like_emscripten {
534 cmd.arg(if sess.panic_strategy() == PanicStrategy::Abort {
535 "DISABLE_EXCEPTION_CATCHING=1"
537 "DISABLE_EXCEPTION_CATCHING=0"
542 let mut linker = codegen_results.linker_info.to_linker(cmd, &sess, flavor, target_cpu);
543 link_sanitizer_runtime(sess, crate_type, &mut *linker);
553 cmd = linker.finalize();
555 if let Some(args) = sess.target.target.options.late_link_args.get(&flavor) {
558 for obj in &sess.target.target.options.post_link_objects {
559 cmd.arg(get_file_path(sess, obj));
561 if sess.crt_static() {
562 for obj in &sess.target.target.options.post_link_objects_crt {
563 cmd.arg(get_file_path(sess, obj));
566 if let Some(args) = sess.target.target.options.post_link_args.get(&flavor) {
569 for &(ref k, ref v) in &sess.target.target.options.link_env {
572 for k in &sess.target.target.options.link_env_remove {
576 if sess.opts.debugging_opts.print_link_args {
577 println!("{:?}", &cmd);
580 // May have not found libraries in the right formats.
581 sess.abort_if_errors();
583 // Invoke the system linker
585 let retry_on_segfault = env::var("RUSTC_RETRY_LINKER_ON_SEGFAULT").is_ok();
590 prog = sess.time("run_linker", || exec_linker(sess, &mut cmd, out_filename, tmpdir));
591 let output = match prog {
592 Ok(ref output) => output,
595 if output.status.success() {
598 let mut out = output.stderr.clone();
599 out.extend(&output.stdout);
600 let out = String::from_utf8_lossy(&out);
602 // Check to see if the link failed with "unrecognized command line option:
603 // '-no-pie'" for gcc or "unknown argument: '-no-pie'" for clang. If so,
604 // reperform the link step without the -no-pie option. This is safe because
605 // if the linker doesn't support -no-pie then it should not default to
606 // linking executables as pie. Different versions of gcc seem to use
607 // different quotes in the error message so don't check for them.
608 if sess.target.target.options.linker_is_gnu
609 && flavor != LinkerFlavor::Ld
610 && (out.contains("unrecognized command line option")
611 || out.contains("unknown argument"))
612 && out.contains("-no-pie")
613 && cmd.get_args().iter().any(|e| e.to_string_lossy() == "-no-pie")
615 info!("linker output: {:?}", out);
616 warn!("Linker does not support -no-pie command line option. Retrying without.");
617 for arg in cmd.take_args() {
618 if arg.to_string_lossy() != "-no-pie" {
626 // Here's a terribly awful hack that really shouldn't be present in any
627 // compiler. Here an environment variable is supported to automatically
628 // retry the linker invocation if the linker looks like it segfaulted.
630 // Gee that seems odd, normally segfaults are things we want to know
631 // about! Unfortunately though in rust-lang/rust#38878 we're
632 // experiencing the linker segfaulting on Travis quite a bit which is
633 // causing quite a bit of pain to land PRs when they spuriously fail
634 // due to a segfault.
636 // The issue #38878 has some more debugging information on it as well,
637 // but this unfortunately looks like it's just a race condition in
638 // macOS's linker with some thread pool working in the background. It
639 // seems that no one currently knows a fix for this so in the meantime
640 // we're left with this...
641 if !retry_on_segfault || i > 3 {
644 let msg_segv = "clang: error: unable to execute command: Segmentation fault: 11";
645 let msg_bus = "clang: error: unable to execute command: Bus error: 10";
646 if out.contains(msg_segv) || out.contains(msg_bus) {
648 "looks like the linker segfaulted when we tried to call it, \
649 automatically retrying again. cmd = {:?}, out = {}.",
655 if is_illegal_instruction(&output.status) {
657 "looks like the linker hit an illegal instruction when we \
658 tried to call it, automatically retrying again. cmd = {:?}, ]\
659 out = {}, status = {}.",
660 cmd, out, output.status,
666 fn is_illegal_instruction(status: &ExitStatus) -> bool {
667 use std::os::unix::prelude::*;
668 status.signal() == Some(libc::SIGILL)
672 fn is_illegal_instruction(_status: &ExitStatus) -> bool {
679 fn escape_string(s: &[u8]) -> String {
680 str::from_utf8(s).map(|s| s.to_owned()).unwrap_or_else(|_| {
681 let mut x = "Non-UTF-8 output: ".to_string();
682 x.extend(s.iter().flat_map(|&b| ascii::escape_default(b)).map(char::from));
686 if !prog.status.success() {
687 let mut output = prog.stderr.clone();
688 output.extend_from_slice(&prog.stdout);
689 sess.struct_err(&format!(
690 "linking with `{}` failed: {}",
694 .note(&format!("{:?}", &cmd))
695 .note(&escape_string(&output))
697 sess.abort_if_errors();
699 info!("linker stderr:\n{}", escape_string(&prog.stderr));
700 info!("linker stdout:\n{}", escape_string(&prog.stdout));
703 let linker_not_found = e.kind() == io::ErrorKind::NotFound;
705 let mut linker_error = {
706 if linker_not_found {
707 sess.struct_err(&format!("linker `{}` not found", pname.display()))
709 sess.struct_err(&format!("could not exec the linker `{}`", pname.display()))
713 linker_error.note(&e.to_string());
715 if !linker_not_found {
716 linker_error.note(&format!("{:?}", &cmd));
721 if sess.target.target.options.is_like_msvc && linker_not_found {
722 sess.note_without_error(
723 "the msvc targets depend on the msvc linker \
724 but `link.exe` was not found",
726 sess.note_without_error(
727 "please ensure that VS 2013, VS 2015, VS 2017 or VS 2019 \
728 was installed with the Visual C++ option",
731 sess.abort_if_errors();
735 // On macOS, debuggers need this utility to get run to do some munging of
736 // the symbols. Note, though, that if the object files are being preserved
737 // for their debug information there's no need for us to run dsymutil.
738 if sess.target.target.options.is_like_osx
739 && sess.opts.debuginfo != DebugInfo::None
740 && !preserve_objects_for_their_debuginfo(sess)
742 if let Err(e) = Command::new("dsymutil").arg(out_filename).output() {
743 sess.fatal(&format!("failed to run dsymutil: {}", e))
748 fn link_sanitizer_runtime(sess: &Session, crate_type: config::CrateType, linker: &mut dyn Linker) {
749 let sanitizer = match &sess.opts.debugging_opts.sanitizer {
754 if crate_type != config::CrateType::Executable {
758 let name = match sanitizer {
759 Sanitizer::Address => "asan",
760 Sanitizer::Leak => "lsan",
761 Sanitizer::Memory => "msan",
762 Sanitizer::Thread => "tsan",
765 let default_sysroot = filesearch::get_or_default_sysroot();
767 filesearch::make_target_lib_path(&default_sysroot, sess.opts.target_triple.triple());
769 match sess.opts.target_triple.triple() {
770 "x86_64-apple-darwin" => {
771 // On Apple platforms, the sanitizer is always built as a dylib, and
772 // LLVM will link to `@rpath/*.dylib`, so we need to specify an
773 // rpath to the library as well (the rpath should be absolute, see
774 // PR #41352 for details).
775 let libname = format!("rustc_rt.{}", name);
776 let rpath = default_tlib.to_str().expect("non-utf8 component in path");
777 linker.args(&["-Wl,-rpath".into(), "-Xlinker".into(), rpath.into()]);
778 linker.link_dylib(Symbol::intern(&libname));
780 "x86_64-unknown-linux-gnu" => {
781 let filename = format!("librustc_rt.{}.a", name);
782 let path = default_tlib.join(&filename);
783 linker.link_whole_rlib(&path);
789 /// Returns a boolean indicating whether the specified crate should be ignored
792 /// Crates ignored during LTO are not lumped together in the "massive object
793 /// file" that we create and are linked in their normal rlib states. See
794 /// comments below for what crates do not participate in LTO.
796 /// It's unusual for a crate to not participate in LTO. Typically only
797 /// compiler-specific and unstable crates have a reason to not participate in
799 pub fn ignored_for_lto(sess: &Session, info: &CrateInfo, cnum: CrateNum) -> bool {
800 // If our target enables builtin function lowering in LLVM then the
801 // crates providing these functions don't participate in LTO (e.g.
802 // no_builtins or compiler builtins crates).
803 !sess.target.target.options.no_builtins
804 && (info.compiler_builtins == Some(cnum) || info.is_no_builtins.contains(&cnum))
807 pub fn linker_and_flavor(sess: &Session) -> (PathBuf, LinkerFlavor) {
810 linker: Option<PathBuf>,
811 flavor: Option<LinkerFlavor>,
812 ) -> Option<(PathBuf, LinkerFlavor)> {
813 match (linker, flavor) {
814 (Some(linker), Some(flavor)) => Some((linker, flavor)),
815 // only the linker flavor is known; use the default linker for the selected flavor
816 (None, Some(flavor)) => Some((
817 PathBuf::from(match flavor {
818 LinkerFlavor::Em => {
825 LinkerFlavor::Gcc => "cc",
826 LinkerFlavor::Ld => "ld",
827 LinkerFlavor::Msvc => "link.exe",
828 LinkerFlavor::Lld(_) => "lld",
829 LinkerFlavor::PtxLinker => "rust-ptx-linker",
833 (Some(linker), None) => {
834 let stem = linker.file_stem().and_then(|stem| stem.to_str()).unwrap_or_else(|| {
835 sess.fatal("couldn't extract file stem from specified linker")
838 let flavor = if stem == "emcc" {
840 } else if stem == "gcc"
841 || stem.ends_with("-gcc")
843 || stem.ends_with("-clang")
846 } else if stem == "ld" || stem == "ld.lld" || stem.ends_with("-ld") {
848 } else if stem == "link" || stem == "lld-link" {
850 } else if stem == "lld" || stem == "rust-lld" {
851 LinkerFlavor::Lld(sess.target.target.options.lld_flavor)
853 // fall back to the value in the target spec
854 sess.target.target.linker_flavor
857 Some((linker, flavor))
859 (None, None) => None,
863 // linker and linker flavor specified via command line have precedence over what the target
864 // specification specifies
865 if let Some(ret) = infer_from(sess, sess.opts.cg.linker.clone(), sess.opts.cg.linker_flavor) {
869 if let Some(ret) = infer_from(
871 sess.target.target.options.linker.clone().map(PathBuf::from),
872 Some(sess.target.target.linker_flavor),
877 bug!("Not enough information provided to determine how to invoke the linker");
880 /// Returns a boolean indicating whether we should preserve the object files on
881 /// the filesystem for their debug information. This is often useful with
882 /// split-dwarf like schemes.
883 pub fn preserve_objects_for_their_debuginfo(sess: &Session) -> bool {
884 // If the objects don't have debuginfo there's nothing to preserve.
885 if sess.opts.debuginfo == config::DebugInfo::None {
889 // If we're only producing artifacts that are archives, no need to preserve
890 // the objects as they're losslessly contained inside the archives.
891 let output_linked = sess
895 .any(|&x| x != config::CrateType::Rlib && x != config::CrateType::Staticlib);
900 // If we're on OSX then the equivalent of split dwarf is turned on by
901 // default. The final executable won't actually have any debug information
902 // except it'll have pointers to elsewhere. Historically we've always run
903 // `dsymutil` to "link all the dwarf together" but this is actually sort of
904 // a bummer for incremental compilation! (the whole point of split dwarf is
905 // that you don't do this sort of dwarf link).
907 // Basically as a result this just means that if we're on OSX and we're
908 // *not* running dsymutil then the object files are the only source of truth
909 // for debug information, so we must preserve them.
910 if sess.target.target.options.is_like_osx {
911 match sess.opts.debugging_opts.run_dsymutil {
912 // dsymutil is not being run, preserve objects
913 Some(false) => return true,
915 // dsymutil is being run, no need to preserve the objects
916 Some(true) => return false,
918 // The default historical behavior was to always run dsymutil, so
919 // we're preserving that temporarily, but we're likely to switch the
921 None => return false,
928 pub fn archive_search_paths(sess: &Session) -> Vec<PathBuf> {
929 sess.target_filesearch(PathKind::Native).search_path_dirs()
937 pub fn print_native_static_libs(sess: &Session, all_native_libs: &[NativeLibrary]) {
938 let lib_args: Vec<_> = all_native_libs
940 .filter(|l| relevant_lib(sess, l))
942 let name = lib.name?;
944 NativeLibraryKind::NativeStaticNobundle | NativeLibraryKind::NativeUnknown => {
945 if sess.target.target.options.is_like_msvc {
946 Some(format!("{}.lib", name))
948 Some(format!("-l{}", name))
951 NativeLibraryKind::NativeFramework => {
952 // ld-only syntax, since there are no frameworks in MSVC
953 Some(format!("-framework {}", name))
955 // These are included, no need to print them
956 NativeLibraryKind::NativeStatic | NativeLibraryKind::NativeRawDylib => None,
960 if !lib_args.is_empty() {
961 sess.note_without_error(
962 "Link against the following native artifacts when linking \
963 against this static library. The order and any duplication \
964 can be significant on some platforms.",
966 // Prefix for greppability
967 sess.note_without_error(&format!("native-static-libs: {}", &lib_args.join(" ")));
971 pub fn get_file_path(sess: &Session, name: &str) -> PathBuf {
972 let fs = sess.target_filesearch(PathKind::Native);
973 let file_path = fs.get_lib_path().join(name);
974 if file_path.exists() {
977 for search_path in fs.search_paths() {
978 let file_path = search_path.dir.join(name);
979 if file_path.exists() {
991 ) -> io::Result<Output> {
992 // When attempting to spawn the linker we run a risk of blowing out the
993 // size limits for spawning a new process with respect to the arguments
994 // we pass on the command line.
996 // Here we attempt to handle errors from the OS saying "your list of
997 // arguments is too big" by reinvoking the linker again with an `@`-file
998 // that contains all the arguments. The theory is that this is then
999 // accepted on all linkers and the linker will read all its options out of
1000 // there instead of looking at the command line.
1001 if !cmd.very_likely_to_exceed_some_spawn_limit() {
1002 match cmd.command().stdout(Stdio::piped()).stderr(Stdio::piped()).spawn() {
1004 let output = child.wait_with_output();
1005 flush_linked_file(&output, out_filename)?;
1008 Err(ref e) if command_line_too_big(e) => {
1009 info!("command line to linker was too big: {}", e);
1011 Err(e) => return Err(e),
1015 info!("falling back to passing arguments to linker via an @-file");
1016 let mut cmd2 = cmd.clone();
1017 let mut args = String::new();
1018 for arg in cmd2.take_args() {
1021 arg: arg.to_str().unwrap(),
1022 is_like_msvc: sess.target.target.options.is_like_msvc,
1026 args.push_str("\n");
1028 let file = tmpdir.join("linker-arguments");
1029 let bytes = if sess.target.target.options.is_like_msvc {
1030 let mut out = Vec::with_capacity((1 + args.len()) * 2);
1031 // start the stream with a UTF-16 BOM
1032 for c in std::iter::once(0xFEFF).chain(args.encode_utf16()) {
1033 // encode in little endian
1035 out.push((c >> 8) as u8);
1041 fs::write(&file, &bytes)?;
1042 cmd2.arg(format!("@{}", file.display()));
1043 info!("invoking linker {:?}", cmd2);
1044 let output = cmd2.output();
1045 flush_linked_file(&output, out_filename)?;
1049 fn flush_linked_file(_: &io::Result<Output>, _: &Path) -> io::Result<()> {
1054 fn flush_linked_file(
1055 command_output: &io::Result<Output>,
1056 out_filename: &Path,
1057 ) -> io::Result<()> {
1058 // On Windows, under high I/O load, output buffers are sometimes not flushed,
1059 // even long after process exit, causing nasty, non-reproducible output bugs.
1061 // File::sync_all() calls FlushFileBuffers() down the line, which solves the problem.
1063 // А full writeup of the original Chrome bug can be found at
1064 // randomascii.wordpress.com/2018/02/25/compiler-bug-linker-bug-windows-kernel-bug/amp
1066 if let &Ok(ref out) = command_output {
1067 if out.status.success() {
1068 if let Ok(of) = fs::OpenOptions::new().write(true).open(out_filename) {
1078 fn command_line_too_big(err: &io::Error) -> bool {
1079 err.raw_os_error() == Some(::libc::E2BIG)
1083 fn command_line_too_big(err: &io::Error) -> bool {
1084 const ERROR_FILENAME_EXCED_RANGE: i32 = 206;
1085 err.raw_os_error() == Some(ERROR_FILENAME_EXCED_RANGE)
1093 impl<'a> fmt::Display for Escape<'a> {
1094 fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
1095 if self.is_like_msvc {
1096 // This is "documented" at
1097 // https://docs.microsoft.com/en-us/cpp/build/reference/at-specify-a-linker-response-file
1099 // Unfortunately there's not a great specification of the
1100 // syntax I could find online (at least) but some local
1101 // testing showed that this seemed sufficient-ish to catch
1102 // at least a few edge cases.
1104 for c in self.arg.chars() {
1106 '"' => write!(f, "\\{}", c)?,
1107 c => write!(f, "{}", c)?,
1112 // This is documented at https://linux.die.net/man/1/ld, namely:
1114 // > Options in file are separated by whitespace. A whitespace
1115 // > character may be included in an option by surrounding the
1116 // > entire option in either single or double quotes. Any
1117 // > character (including a backslash) may be included by
1118 // > prefixing the character to be included with a backslash.
1120 // We put an argument on each line, so all we need to do is
1121 // ensure the line is interpreted as one whole argument.
1122 for c in self.arg.chars() {
1124 '\\' | ' ' => write!(f, "\\{}", c)?,
1125 c => write!(f, "{}", c)?,
1134 fn link_args<'a, B: ArchiveBuilder<'a>>(
1135 cmd: &mut dyn Linker,
1136 flavor: LinkerFlavor,
1138 crate_type: config::CrateType,
1140 out_filename: &Path,
1141 codegen_results: &CodegenResults,
1143 // Linker plugins should be specified early in the list of arguments
1144 cmd.linker_plugin_lto();
1146 // The default library location, we need this to find the runtime.
1147 // The location of crates will be determined as needed.
1148 let lib_path = sess.target_filesearch(PathKind::All).get_lib_path();
1150 // target descriptor
1151 let t = &sess.target.target;
1153 cmd.include_path(&fix_windows_verbatim_for_gcc(&lib_path));
1155 for obj in codegen_results.modules.iter().filter_map(|m| m.object.as_ref()) {
1156 cmd.add_object(obj);
1158 cmd.output_filename(out_filename);
1160 if crate_type == config::CrateType::Executable && sess.target.target.options.is_like_windows {
1161 if let Some(ref s) = codegen_results.windows_subsystem {
1166 // If we're building something like a dynamic library then some platforms
1167 // need to make sure that all symbols are exported correctly from the
1169 cmd.export_symbols(tmpdir, crate_type);
1171 // When linking a dynamic library, we put the metadata into a section of the
1172 // executable. This metadata is in a separate object file from the main
1173 // object file, so we link that in here.
1174 if crate_type == config::CrateType::Dylib || crate_type == config::CrateType::ProcMacro {
1175 let obj = codegen_results.metadata_module.as_ref().and_then(|m| m.object.as_ref());
1176 if let Some(obj) = obj {
1177 cmd.add_object(obj);
1181 let obj = codegen_results.allocator_module.as_ref().and_then(|m| m.object.as_ref());
1182 if let Some(obj) = obj {
1183 cmd.add_object(obj);
1186 // Try to strip as much out of the generated object by removing unused
1187 // sections if possible. See more comments in linker.rs
1188 if !sess.opts.cg.link_dead_code {
1189 let keep_metadata = crate_type == config::CrateType::Dylib;
1190 cmd.gc_sections(keep_metadata);
1193 let used_link_args = &codegen_results.crate_info.link_args;
1195 if crate_type == config::CrateType::Executable {
1196 let mut position_independent_executable = false;
1198 if t.options.position_independent_executables {
1199 let empty_vec = Vec::new();
1200 let args = sess.opts.cg.link_args.as_ref().unwrap_or(&empty_vec);
1201 let more_args = &sess.opts.cg.link_arg;
1202 let mut args = args.iter().chain(more_args.iter()).chain(used_link_args.iter());
1204 if is_pic(sess) && !sess.crt_static() && !args.any(|x| *x == "-static") {
1205 position_independent_executable = true;
1209 if position_independent_executable {
1210 cmd.position_independent_executable();
1212 // recent versions of gcc can be configured to generate position
1213 // independent executables by default. We have to pass -no-pie to
1214 // explicitly turn that off. Not applicable to ld.
1215 if sess.target.target.options.linker_is_gnu && flavor != LinkerFlavor::Ld {
1216 cmd.no_position_independent_executable();
1221 let relro_level = match sess.opts.debugging_opts.relro_level {
1222 Some(level) => level,
1223 None => t.options.relro_level,
1226 RelroLevel::Full => {
1229 RelroLevel::Partial => {
1230 cmd.partial_relro();
1232 RelroLevel::Off => {
1235 RelroLevel::None => {}
1238 // Pass optimization flags down to the linker.
1241 // Pass debuginfo flags down to the linker.
1244 // We want to, by default, prevent the compiler from accidentally leaking in
1245 // any system libraries, so we may explicitly ask linkers to not link to any
1246 // libraries by default. Note that this does not happen for windows because
1247 // windows pulls in some large number of libraries and I couldn't quite
1248 // figure out which subset we wanted.
1250 // This is all naturally configurable via the standard methods as well.
1251 if !sess.opts.cg.default_linker_libraries.unwrap_or(false) && t.options.no_default_libraries {
1252 cmd.no_default_libraries();
1255 // Take careful note of the ordering of the arguments we pass to the linker
1256 // here. Linkers will assume that things on the left depend on things to the
1257 // right. Things on the right cannot depend on things on the left. This is
1258 // all formally implemented in terms of resolving symbols (libs on the right
1259 // resolve unknown symbols of libs on the left, but not vice versa).
1261 // For this reason, we have organized the arguments we pass to the linker as
1264 // 1. The local object that LLVM just generated
1265 // 2. Local native libraries
1266 // 3. Upstream rust libraries
1267 // 4. Upstream native libraries
1269 // The rationale behind this ordering is that those items lower down in the
1270 // list can't depend on items higher up in the list. For example nothing can
1271 // depend on what we just generated (e.g., that'd be a circular dependency).
1272 // Upstream rust libraries are not allowed to depend on our local native
1273 // libraries as that would violate the structure of the DAG, in that
1274 // scenario they are required to link to them as well in a shared fashion.
1276 // Note that upstream rust libraries may contain native dependencies as
1277 // well, but they also can't depend on what we just started to add to the
1278 // link line. And finally upstream native libraries can't depend on anything
1279 // in this DAG so far because they're only dylibs and dylibs can only depend
1280 // on other dylibs (e.g., other native deps).
1281 add_local_native_libraries(cmd, sess, codegen_results);
1282 add_upstream_rust_crates::<B>(cmd, sess, codegen_results, crate_type, tmpdir);
1283 add_upstream_native_libraries(cmd, sess, codegen_results, crate_type);
1285 // Tell the linker what we're doing.
1286 if crate_type != config::CrateType::Executable {
1287 cmd.build_dylib(out_filename);
1289 if crate_type == config::CrateType::Executable && sess.crt_static() {
1290 cmd.build_static_executable();
1293 if sess.opts.cg.profile_generate.enabled() {
1297 // FIXME (#2397): At some point we want to rpath our guesses as to
1298 // where extern libraries might live, based on the
1299 // addl_lib_search_paths
1300 if sess.opts.cg.rpath {
1301 let target_triple = sess.opts.target_triple.triple();
1302 let mut get_install_prefix_lib_path = || {
1303 let install_prefix = option_env!("CFG_PREFIX").expect("CFG_PREFIX");
1304 let tlib = filesearch::relative_target_lib_path(&sess.sysroot, target_triple);
1305 let mut path = PathBuf::from(install_prefix);
1310 let mut rpath_config = RPathConfig {
1311 used_crates: &codegen_results.crate_info.used_crates_dynamic,
1312 out_filename: out_filename.to_path_buf(),
1313 has_rpath: sess.target.target.options.has_rpath,
1314 is_like_osx: sess.target.target.options.is_like_osx,
1315 linker_is_gnu: sess.target.target.options.linker_is_gnu,
1316 get_install_prefix_lib_path: &mut get_install_prefix_lib_path,
1318 cmd.args(&rpath::get_rpath_flags(&mut rpath_config));
1321 // Finally add all the linker arguments provided on the command line along
1322 // with any #[link_args] attributes found inside the crate
1323 if let Some(ref args) = sess.opts.cg.link_args {
1326 cmd.args(&sess.opts.cg.link_arg);
1327 cmd.args(&used_link_args);
1330 // # Native library linking
1332 // User-supplied library search paths (-L on the command line). These are
1333 // the same paths used to find Rust crates, so some of them may have been
1334 // added already by the previous crate linking code. This only allows them
1335 // to be found at compile time so it is still entirely up to outside
1336 // forces to make sure that library can be found at runtime.
1338 // Also note that the native libraries linked here are only the ones located
1339 // in the current crate. Upstream crates with native library dependencies
1340 // may have their native library pulled in above.
1341 pub fn add_local_native_libraries(
1342 cmd: &mut dyn Linker,
1344 codegen_results: &CodegenResults,
1346 let filesearch = sess.target_filesearch(PathKind::All);
1347 for search_path in filesearch.search_paths() {
1348 match search_path.kind {
1349 PathKind::Framework => {
1350 cmd.framework_path(&search_path.dir);
1353 cmd.include_path(&fix_windows_verbatim_for_gcc(&search_path.dir));
1359 codegen_results.crate_info.used_libraries.iter().filter(|l| relevant_lib(sess, l));
1361 let search_path = archive_search_paths(sess);
1362 for lib in relevant_libs {
1363 let name = match lib.name {
1368 NativeLibraryKind::NativeUnknown => cmd.link_dylib(name),
1369 NativeLibraryKind::NativeFramework => cmd.link_framework(name),
1370 NativeLibraryKind::NativeStaticNobundle => cmd.link_staticlib(name),
1371 NativeLibraryKind::NativeStatic => cmd.link_whole_staticlib(name, &search_path),
1372 NativeLibraryKind::NativeRawDylib => {
1373 // FIXME(#58713): Proper handling for raw dylibs.
1374 bug!("raw_dylib feature not yet implemented");
1380 // # Rust Crate linking
1382 // Rust crates are not considered at all when creating an rlib output. All
1383 // dependencies will be linked when producing the final output (instead of
1384 // the intermediate rlib version)
1385 fn add_upstream_rust_crates<'a, B: ArchiveBuilder<'a>>(
1386 cmd: &mut dyn Linker,
1388 codegen_results: &CodegenResults,
1389 crate_type: config::CrateType,
1392 // All of the heavy lifting has previously been accomplished by the
1393 // dependency_format module of the compiler. This is just crawling the
1394 // output of that module, adding crates as necessary.
1396 // Linking to a rlib involves just passing it to the linker (the linker
1397 // will slurp up the object files inside), and linking to a dynamic library
1398 // involves just passing the right -l flag.
1400 let (_, data) = codegen_results
1404 .find(|(ty, _)| *ty == crate_type)
1405 .expect("failed to find crate type in dependency format list");
1407 // Invoke get_used_crates to ensure that we get a topological sorting of
1409 let deps = &codegen_results.crate_info.used_crates_dynamic;
1411 // There's a few internal crates in the standard library (aka libcore and
1412 // libstd) which actually have a circular dependence upon one another. This
1413 // currently arises through "weak lang items" where libcore requires things
1414 // like `rust_begin_unwind` but libstd ends up defining it. To get this
1415 // circular dependence to work correctly in all situations we'll need to be
1416 // sure to correctly apply the `--start-group` and `--end-group` options to
1417 // GNU linkers, otherwise if we don't use any other symbol from the standard
1418 // library it'll get discarded and the whole application won't link.
1420 // In this loop we're calculating the `group_end`, after which crate to
1421 // pass `--end-group` and `group_start`, before which crate to pass
1422 // `--start-group`. We currently do this by passing `--end-group` after
1423 // the first crate (when iterating backwards) that requires a lang item
1424 // defined somewhere else. Once that's set then when we've defined all the
1425 // necessary lang items we'll pass `--start-group`.
1427 // Note that this isn't amazing logic for now but it should do the trick
1428 // for the current implementation of the standard library.
1429 let mut group_end = None;
1430 let mut group_start = None;
1431 let mut end_with = FxHashSet::default();
1432 let info = &codegen_results.crate_info;
1433 for &(cnum, _) in deps.iter().rev() {
1434 if let Some(missing) = info.missing_lang_items.get(&cnum) {
1435 end_with.extend(missing.iter().cloned());
1436 if end_with.len() > 0 && group_end.is_none() {
1437 group_end = Some(cnum);
1440 end_with.retain(|item| info.lang_item_to_crate.get(item) != Some(&cnum));
1441 if end_with.len() == 0 && group_end.is_some() {
1442 group_start = Some(cnum);
1447 // If we didn't end up filling in all lang items from upstream crates then
1448 // we'll be filling it in with our crate. This probably means we're the
1449 // standard library itself, so skip this for now.
1450 if group_end.is_some() && group_start.is_none() {
1454 let mut compiler_builtins = None;
1456 for &(cnum, _) in deps.iter() {
1457 if group_start == Some(cnum) {
1461 // We may not pass all crates through to the linker. Some crates may
1462 // appear statically in an existing dylib, meaning we'll pick up all the
1463 // symbols from the dylib.
1464 let src = &codegen_results.crate_info.used_crate_source[&cnum];
1465 match data[cnum.as_usize() - 1] {
1466 _ if codegen_results.crate_info.profiler_runtime == Some(cnum) => {
1467 add_static_crate::<B>(cmd, sess, codegen_results, tmpdir, crate_type, cnum);
1469 // compiler-builtins are always placed last to ensure that they're
1470 // linked correctly.
1471 _ if codegen_results.crate_info.compiler_builtins == Some(cnum) => {
1472 assert!(compiler_builtins.is_none());
1473 compiler_builtins = Some(cnum);
1475 Linkage::NotLinked | Linkage::IncludedFromDylib => {}
1476 Linkage::Static => {
1477 add_static_crate::<B>(cmd, sess, codegen_results, tmpdir, crate_type, cnum);
1479 Linkage::Dynamic => add_dynamic_crate(cmd, sess, &src.dylib.as_ref().unwrap().0),
1482 if group_end == Some(cnum) {
1487 // compiler-builtins are always placed last to ensure that they're
1488 // linked correctly.
1489 // We must always link the `compiler_builtins` crate statically. Even if it
1490 // was already "included" in a dylib (e.g., `libstd` when `-C prefer-dynamic`
1492 if let Some(cnum) = compiler_builtins {
1493 add_static_crate::<B>(cmd, sess, codegen_results, tmpdir, crate_type, cnum);
1496 // Converts a library file-stem into a cc -l argument
1497 fn unlib<'a>(config: &config::Config, stem: &'a str) -> &'a str {
1498 if stem.starts_with("lib") && !config.target.options.is_like_windows {
1505 // Adds the static "rlib" versions of all crates to the command line.
1506 // There's a bit of magic which happens here specifically related to LTO and
1507 // dynamic libraries. Specifically:
1509 // * For LTO, we remove upstream object files.
1510 // * For dylibs we remove metadata and bytecode from upstream rlibs
1512 // When performing LTO, almost(*) all of the bytecode from the upstream
1513 // libraries has already been included in our object file output. As a
1514 // result we need to remove the object files in the upstream libraries so
1515 // the linker doesn't try to include them twice (or whine about duplicate
1516 // symbols). We must continue to include the rest of the rlib, however, as
1517 // it may contain static native libraries which must be linked in.
1519 // (*) Crates marked with `#![no_builtins]` don't participate in LTO and
1520 // their bytecode wasn't included. The object files in those libraries must
1521 // still be passed to the linker.
1523 // When making a dynamic library, linkers by default don't include any
1524 // object files in an archive if they're not necessary to resolve the link.
1525 // We basically want to convert the archive (rlib) to a dylib, though, so we
1526 // *do* want everything included in the output, regardless of whether the
1527 // linker thinks it's needed or not. As a result we must use the
1528 // --whole-archive option (or the platform equivalent). When using this
1529 // option the linker will fail if there are non-objects in the archive (such
1530 // as our own metadata and/or bytecode). All in all, for rlibs to be
1531 // entirely included in dylibs, we need to remove all non-object files.
1533 // Note, however, that if we're not doing LTO or we're not producing a dylib
1534 // (aka we're making an executable), we can just pass the rlib blindly to
1535 // the linker (fast) because it's fine if it's not actually included as
1536 // we're at the end of the dependency chain.
1537 fn add_static_crate<'a, B: ArchiveBuilder<'a>>(
1538 cmd: &mut dyn Linker,
1540 codegen_results: &CodegenResults,
1542 crate_type: config::CrateType,
1545 let src = &codegen_results.crate_info.used_crate_source[&cnum];
1546 let cratepath = &src.rlib.as_ref().unwrap().0;
1548 // See the comment above in `link_staticlib` and `link_rlib` for why if
1549 // there's a static library that's not relevant we skip all object
1551 let native_libs = &codegen_results.crate_info.native_libraries[&cnum];
1552 let skip_native = native_libs
1554 .any(|lib| lib.kind == NativeLibraryKind::NativeStatic && !relevant_lib(sess, lib));
1556 if (!are_upstream_rust_objects_already_included(sess)
1557 || ignored_for_lto(sess, &codegen_results.crate_info, cnum))
1558 && crate_type != config::CrateType::Dylib
1561 cmd.link_rlib(&fix_windows_verbatim_for_gcc(cratepath));
1565 let dst = tmpdir.join(cratepath.file_name().unwrap());
1566 let name = cratepath.file_name().unwrap().to_str().unwrap();
1567 let name = &name[3..name.len() - 5]; // chop off lib/.rlib
1569 sess.prof.extra_verbose_generic_activity(&format!("altering {}.rlib", name)).run(|| {
1570 let mut archive = <B as ArchiveBuilder>::new(sess, &dst, Some(cratepath));
1571 archive.update_symbols();
1573 let mut any_objects = false;
1574 for f in archive.src_files() {
1575 if f.ends_with(RLIB_BYTECODE_EXTENSION) || f == METADATA_FILENAME {
1576 archive.remove_file(&f);
1580 let canonical = f.replace("-", "_");
1581 let canonical_name = name.replace("-", "_");
1583 let is_rust_object =
1584 canonical.starts_with(&canonical_name) && looks_like_rust_object_file(&f);
1586 // If we've been requested to skip all native object files
1587 // (those not generated by the rust compiler) then we can skip
1588 // this file. See above for why we may want to do this.
1589 let skip_because_cfg_say_so = skip_native && !is_rust_object;
1591 // If we're performing LTO and this is a rust-generated object
1592 // file, then we don't need the object file as it's part of the
1593 // LTO module. Note that `#![no_builtins]` is excluded from LTO,
1594 // though, so we let that object file slide.
1595 let skip_because_lto = are_upstream_rust_objects_already_included(sess)
1597 && (sess.target.target.options.no_builtins
1598 || !codegen_results.crate_info.is_no_builtins.contains(&cnum));
1600 if skip_because_cfg_say_so || skip_because_lto {
1601 archive.remove_file(&f);
1612 // If we're creating a dylib, then we need to include the
1613 // whole of each object in our archive into that artifact. This is
1614 // because a `dylib` can be reused as an intermediate artifact.
1616 // Note, though, that we don't want to include the whole of a
1617 // compiler-builtins crate (e.g., compiler-rt) because it'll get
1618 // repeatedly linked anyway.
1619 if crate_type == config::CrateType::Dylib
1620 && codegen_results.crate_info.compiler_builtins != Some(cnum)
1622 cmd.link_whole_rlib(&fix_windows_verbatim_for_gcc(&dst));
1624 cmd.link_rlib(&fix_windows_verbatim_for_gcc(&dst));
1629 // Same thing as above, but for dynamic crates instead of static crates.
1630 fn add_dynamic_crate(cmd: &mut dyn Linker, sess: &Session, cratepath: &Path) {
1631 // Just need to tell the linker about where the library lives and
1633 let parent = cratepath.parent();
1634 if let Some(dir) = parent {
1635 cmd.include_path(&fix_windows_verbatim_for_gcc(dir));
1637 let filestem = cratepath.file_stem().unwrap().to_str().unwrap();
1638 cmd.link_rust_dylib(
1639 Symbol::intern(&unlib(&sess.target, filestem)),
1640 parent.unwrap_or(Path::new("")),
1645 // Link in all of our upstream crates' native dependencies. Remember that
1646 // all of these upstream native dependencies are all non-static
1647 // dependencies. We've got two cases then:
1649 // 1. The upstream crate is an rlib. In this case we *must* link in the
1650 // native dependency because the rlib is just an archive.
1652 // 2. The upstream crate is a dylib. In order to use the dylib, we have to
1653 // have the dependency present on the system somewhere. Thus, we don't
1654 // gain a whole lot from not linking in the dynamic dependency to this
1657 // The use case for this is a little subtle. In theory the native
1658 // dependencies of a crate are purely an implementation detail of the crate
1659 // itself, but the problem arises with generic and inlined functions. If a
1660 // generic function calls a native function, then the generic function must
1661 // be instantiated in the target crate, meaning that the native symbol must
1662 // also be resolved in the target crate.
1663 pub fn add_upstream_native_libraries(
1664 cmd: &mut dyn Linker,
1666 codegen_results: &CodegenResults,
1667 crate_type: config::CrateType,
1669 // Be sure to use a topological sorting of crates because there may be
1670 // interdependencies between native libraries. When passing -nodefaultlibs,
1671 // for example, almost all native libraries depend on libc, so we have to
1672 // make sure that's all the way at the right (liblibc is near the base of
1673 // the dependency chain).
1675 // This passes RequireStatic, but the actual requirement doesn't matter,
1676 // we're just getting an ordering of crate numbers, we're not worried about
1678 let (_, data) = codegen_results
1682 .find(|(ty, _)| *ty == crate_type)
1683 .expect("failed to find crate type in dependency format list");
1685 let crates = &codegen_results.crate_info.used_crates_static;
1686 for &(cnum, _) in crates {
1687 for lib in codegen_results.crate_info.native_libraries[&cnum].iter() {
1688 let name = match lib.name {
1692 if !relevant_lib(sess, &lib) {
1696 NativeLibraryKind::NativeUnknown => cmd.link_dylib(name),
1697 NativeLibraryKind::NativeFramework => cmd.link_framework(name),
1698 NativeLibraryKind::NativeStaticNobundle => {
1699 // Link "static-nobundle" native libs only if the crate they originate from
1700 // is being linked statically to the current crate. If it's linked dynamically
1701 // or is an rlib already included via some other dylib crate, the symbols from
1702 // native libs will have already been included in that dylib.
1703 if data[cnum.as_usize() - 1] == Linkage::Static {
1704 cmd.link_staticlib(name)
1707 // ignore statically included native libraries here as we've
1708 // already included them when we included the rust library
1710 NativeLibraryKind::NativeStatic => {}
1711 NativeLibraryKind::NativeRawDylib => {
1712 // FIXME(#58713): Proper handling for raw dylibs.
1713 bug!("raw_dylib feature not yet implemented");
1720 pub fn relevant_lib(sess: &Session, lib: &NativeLibrary) -> bool {
1722 Some(ref cfg) => syntax::attr::cfg_matches(cfg, &sess.parse_sess, None),
1727 pub fn are_upstream_rust_objects_already_included(sess: &Session) -> bool {
1729 config::Lto::Fat => true,
1730 config::Lto::Thin => {
1731 // If we defer LTO to the linker, we haven't run LTO ourselves, so
1732 // any upstream object files have not been copied yet.
1733 !sess.opts.cg.linker_plugin_lto.enabled()
1735 config::Lto::No | config::Lto::ThinLocal => false,
1739 fn is_pic(sess: &Session) -> bool {
1740 let reloc_model_arg = match sess.opts.cg.relocation_model {
1741 Some(ref s) => &s[..],
1742 None => &sess.target.target.options.relocation_model[..],
1745 reloc_model_arg == "pic"