1 use super::archive::{ArchiveBuilder, ArchiveConfig};
2 use super::bytecode::RLIB_BYTECODE_EXTENSION;
3 use super::rpath::RPathConfig;
6 use crate::metadata::METADATA_FILENAME;
7 use crate::context::get_reloc_model;
9 use rustc_codegen_ssa::back::linker::Linker;
10 use rustc_codegen_ssa::back::link::{remove, ignored_for_lto, each_linked_rlib, linker_and_flavor,
12 use rustc_codegen_ssa::back::command::Command;
13 use rustc::session::config::{self, DebugInfo, OutputFilenames, OutputType, PrintRequest};
14 use rustc::session::config::{RUST_CGU_EXT, Lto, Sanitizer};
15 use rustc::session::filesearch;
16 use rustc::session::search_paths::PathKind;
17 use rustc::session::Session;
18 use rustc::middle::cstore::{NativeLibrary, NativeLibraryKind};
19 use rustc::middle::dependency_format::Linkage;
20 use rustc_codegen_ssa::CodegenResults;
21 use rustc::util::common::time;
22 use rustc_fs_util::fix_windows_verbatim_for_gcc;
23 use rustc::hir::def_id::CrateNum;
24 use tempfile::{Builder as TempFileBuilder, TempDir};
25 use rustc_target::spec::{PanicStrategy, RelroLevel, LinkerFlavor};
26 use rustc_data_structures::fx::FxHashSet;
35 use std::path::{Path, PathBuf};
36 use std::process::{Output, Stdio};
40 pub use rustc_codegen_utils::link::{find_crate_name, filename_for_input, default_output_for_target,
41 invalid_output_for_target, filename_for_metadata,
42 out_filename, check_file_is_writeable};
45 /// Performs the linkage portion of the compilation phase. This will generate all
46 /// of the requested outputs for this compilation session.
47 pub(crate) fn link_binary(sess: &Session,
48 codegen_results: &CodegenResults,
49 outputs: &OutputFilenames,
50 crate_name: &str) -> Vec<PathBuf> {
51 let mut out_filenames = Vec::new();
52 for &crate_type in sess.crate_types.borrow().iter() {
53 // Ignore executable crates if we have -Z no-codegen, as they will error.
54 let output_metadata = sess.opts.output_types.contains_key(&OutputType::Metadata);
55 if (sess.opts.debugging_opts.no_codegen || !sess.opts.output_types.should_codegen()) &&
57 crate_type == config::CrateType::Executable {
61 if invalid_output_for_target(sess, crate_type) {
62 bug!("invalid output type `{:?}` for target os `{}`",
63 crate_type, sess.opts.target_triple);
65 let out_files = link_binary_output(sess,
70 out_filenames.extend(out_files);
73 // Remove the temporary object file and metadata if we aren't saving temps
74 if !sess.opts.cg.save_temps {
75 if sess.opts.output_types.should_codegen() && !preserve_objects_for_their_debuginfo(sess) {
76 for obj in codegen_results.modules.iter().filter_map(|m| m.object.as_ref()) {
80 for obj in codegen_results.modules.iter().filter_map(|m| m.bytecode_compressed.as_ref()) {
83 if let Some(ref obj) = codegen_results.metadata_module.object {
86 if let Some(ref allocator) = codegen_results.allocator_module {
87 if let Some(ref obj) = allocator.object {
90 if let Some(ref bc) = allocator.bytecode_compressed {
99 /// Returns a boolean indicating whether we should preserve the object files on
100 /// the filesystem for their debug information. This is often useful with
101 /// split-dwarf like schemes.
102 fn preserve_objects_for_their_debuginfo(sess: &Session) -> bool {
103 // If the objects don't have debuginfo there's nothing to preserve.
104 if sess.opts.debuginfo == DebugInfo::None {
108 // If we're only producing artifacts that are archives, no need to preserve
109 // the objects as they're losslessly contained inside the archives.
110 let output_linked = sess.crate_types.borrow()
112 .any(|&x| x != config::CrateType::Rlib && x != config::CrateType::Staticlib);
117 // If we're on OSX then the equivalent of split dwarf is turned on by
118 // default. The final executable won't actually have any debug information
119 // except it'll have pointers to elsewhere. Historically we've always run
120 // `dsymutil` to "link all the dwarf together" but this is actually sort of
121 // a bummer for incremental compilation! (the whole point of split dwarf is
122 // that you don't do this sort of dwarf link).
124 // Basically as a result this just means that if we're on OSX and we're
125 // *not* running dsymutil then the object files are the only source of truth
126 // for debug information, so we must preserve them.
127 if sess.target.target.options.is_like_osx {
128 match sess.opts.debugging_opts.run_dsymutil {
129 // dsymutil is not being run, preserve objects
130 Some(false) => return true,
132 // dsymutil is being run, no need to preserve the objects
133 Some(true) => return false,
135 // The default historical behavior was to always run dsymutil, so
136 // we're preserving that temporarily, but we're likely to switch the
138 None => return false,
145 fn link_binary_output(sess: &Session,
146 codegen_results: &CodegenResults,
147 crate_type: config::CrateType,
148 outputs: &OutputFilenames,
149 crate_name: &str) -> Vec<PathBuf> {
150 for obj in codegen_results.modules.iter().filter_map(|m| m.object.as_ref()) {
151 check_file_is_writeable(obj, sess);
154 let mut out_filenames = vec![];
156 if outputs.outputs.contains_key(&OutputType::Metadata) {
157 let out_filename = filename_for_metadata(sess, crate_name, outputs);
158 // To avoid races with another rustc process scanning the output directory,
159 // we need to write the file somewhere else and atomically move it to its
160 // final destination, with a `fs::rename` call. In order for the rename to
161 // always succeed, the temporary file needs to be on the same filesystem,
162 // which is why we create it inside the output directory specifically.
163 let metadata_tmpdir = TempFileBuilder::new()
165 .tempdir_in(out_filename.parent().unwrap())
166 .unwrap_or_else(|err| sess.fatal(&format!("couldn't create a temp dir: {}", err)));
167 let metadata = emit_metadata(sess, codegen_results, &metadata_tmpdir);
168 if let Err(e) = fs::rename(metadata, &out_filename) {
169 sess.fatal(&format!("failed to write {}: {}", out_filename.display(), e));
171 out_filenames.push(out_filename);
174 let tmpdir = TempFileBuilder::new().prefix("rustc").tempdir().unwrap_or_else(|err|
175 sess.fatal(&format!("couldn't create a temp dir: {}", err)));
177 if outputs.outputs.should_codegen() {
178 let out_filename = out_filename(sess, crate_type, outputs, crate_name);
180 config::CrateType::Rlib => {
187 config::CrateType::Staticlib => {
188 link_staticlib(sess, codegen_results, &out_filename, &tmpdir);
191 link_natively(sess, crate_type, &out_filename, codegen_results, tmpdir.path());
194 out_filenames.push(out_filename);
197 if sess.opts.cg.save_temps {
198 let _ = tmpdir.into_path();
204 fn archive_search_paths(sess: &Session) -> Vec<PathBuf> {
205 sess.target_filesearch(PathKind::Native).search_path_dirs()
208 fn archive_config<'a>(sess: &'a Session,
210 input: Option<&Path>) -> ArchiveConfig<'a> {
213 dst: output.to_path_buf(),
214 src: input.map(|p| p.to_path_buf()),
215 lib_search_paths: archive_search_paths(sess),
219 /// We use a temp directory here to avoid races between concurrent rustc processes,
220 /// such as builds in the same directory using the same filename for metadata while
221 /// building an `.rlib` (stomping over one another), or writing an `.rmeta` into a
222 /// directory being searched for `extern crate` (observing an incomplete file).
223 /// The returned path is the temporary file containing the complete metadata.
224 fn emit_metadata<'a>(
226 codegen_results: &CodegenResults,
229 let out_filename = tmpdir.path().join(METADATA_FILENAME);
230 let result = fs::write(&out_filename, &codegen_results.metadata.raw_data);
232 if let Err(e) = result {
233 sess.fatal(&format!("failed to write {}: {}", out_filename.display(), e));
246 // An rlib in its current incarnation is essentially a renamed .a file. The
247 // rlib primarily contains the object file of the crate, but it also contains
248 // all of the object files from native libraries. This is done by unzipping
249 // native libraries and inserting all of the contents into this archive.
250 fn link_rlib<'a>(sess: &'a Session,
251 codegen_results: &CodegenResults,
254 tmpdir: &TempDir) -> ArchiveBuilder<'a> {
255 info!("preparing rlib to {:?}", out_filename);
256 let mut ab = ArchiveBuilder::new(archive_config(sess, out_filename, None));
258 for obj in codegen_results.modules.iter().filter_map(|m| m.object.as_ref()) {
262 // Note that in this loop we are ignoring the value of `lib.cfg`. That is,
263 // we may not be configured to actually include a static library if we're
264 // adding it here. That's because later when we consume this rlib we'll
265 // decide whether we actually needed the static library or not.
267 // To do this "correctly" we'd need to keep track of which libraries added
268 // which object files to the archive. We don't do that here, however. The
269 // #[link(cfg(..))] feature is unstable, though, and only intended to get
270 // liblibc working. In that sense the check below just indicates that if
271 // there are any libraries we want to omit object files for at link time we
272 // just exclude all custom object files.
274 // Eventually if we want to stabilize or flesh out the #[link(cfg(..))]
275 // feature then we'll need to figure out how to record what objects were
276 // loaded from the libraries found here and then encode that into the
277 // metadata of the rlib we're generating somehow.
278 for lib in codegen_results.crate_info.used_libraries.iter() {
280 NativeLibraryKind::NativeStatic => {}
281 NativeLibraryKind::NativeStaticNobundle |
282 NativeLibraryKind::NativeFramework |
283 NativeLibraryKind::NativeUnknown => continue,
285 if let Some(name) = lib.name {
286 ab.add_native_library(&name.as_str());
290 // After adding all files to the archive, we need to update the
291 // symbol table of the archive.
294 // Note that it is important that we add all of our non-object "magical
295 // files" *after* all of the object files in the archive. The reason for
296 // this is as follows:
298 // * When performing LTO, this archive will be modified to remove
299 // objects from above. The reason for this is described below.
301 // * When the system linker looks at an archive, it will attempt to
302 // determine the architecture of the archive in order to see whether its
305 // The algorithm for this detection is: iterate over the files in the
306 // archive. Skip magical SYMDEF names. Interpret the first file as an
307 // object file. Read architecture from the object file.
309 // * As one can probably see, if "metadata" and "foo.bc" were placed
310 // before all of the objects, then the architecture of this archive would
311 // not be correctly inferred once 'foo.o' is removed.
313 // Basically, all this means is that this code should not move above the
316 RlibFlavor::Normal => {
317 // Instead of putting the metadata in an object file section, rlibs
318 // contain the metadata in a separate file.
319 ab.add_file(&emit_metadata(sess, codegen_results, tmpdir));
321 // For LTO purposes, the bytecode of this library is also inserted
323 for bytecode in codegen_results
326 .filter_map(|m| m.bytecode_compressed.as_ref())
328 ab.add_file(bytecode);
331 // After adding all files to the archive, we need to update the
332 // symbol table of the archive. This currently dies on macOS (see
333 // #11162), and isn't necessary there anyway
334 if !sess.target.target.options.is_like_osx {
339 RlibFlavor::StaticlibBase => {
340 let obj = codegen_results.allocator_module
342 .and_then(|m| m.object.as_ref());
343 if let Some(obj) = obj {
352 // Create a static archive
354 // This is essentially the same thing as an rlib, but it also involves adding
355 // all of the upstream crates' objects into the archive. This will slurp in
356 // all of the native libraries of upstream dependencies as well.
358 // Additionally, there's no way for us to link dynamic libraries, so we warn
359 // about all dynamic library dependencies that they're not linked in.
361 // There's no need to include metadata in a static archive, so ensure to not
362 // link in the metadata object file (and also don't prepare the archive with a
364 fn link_staticlib(sess: &Session,
365 codegen_results: &CodegenResults,
368 let mut ab = link_rlib(sess,
370 RlibFlavor::StaticlibBase,
373 let mut all_native_libs = vec![];
375 let res = each_linked_rlib(sess, &codegen_results.crate_info, &mut |cnum, path| {
376 let name = &codegen_results.crate_info.crate_name[&cnum];
377 let native_libs = &codegen_results.crate_info.native_libraries[&cnum];
379 // Here when we include the rlib into our staticlib we need to make a
380 // decision whether to include the extra object files along the way.
381 // These extra object files come from statically included native
382 // libraries, but they may be cfg'd away with #[link(cfg(..))].
384 // This unstable feature, though, only needs liblibc to work. The only
385 // use case there is where musl is statically included in liblibc.rlib,
386 // so if we don't want the included version we just need to skip it. As
387 // a result the logic here is that if *any* linked library is cfg'd away
388 // we just skip all object files.
390 // Clearly this is not sufficient for a general purpose feature, and
391 // we'd want to read from the library's metadata to determine which
392 // object files come from where and selectively skip them.
393 let skip_object_files = native_libs.iter().any(|lib| {
394 lib.kind == NativeLibraryKind::NativeStatic && !relevant_lib(sess, lib)
398 are_upstream_rust_objects_already_included(sess) &&
399 !ignored_for_lto(sess, &codegen_results.crate_info, cnum),
400 skip_object_files).unwrap();
402 all_native_libs.extend(codegen_results.crate_info.native_libraries[&cnum].iter().cloned());
404 if let Err(e) = res {
411 if !all_native_libs.is_empty() {
412 if sess.opts.prints.contains(&PrintRequest::NativeStaticLibs) {
413 print_native_static_libs(sess, &all_native_libs);
418 fn print_native_static_libs(sess: &Session, all_native_libs: &[NativeLibrary]) {
419 let lib_args: Vec<_> = all_native_libs.iter()
420 .filter(|l| relevant_lib(sess, l))
422 let name = lib.name?;
424 NativeLibraryKind::NativeStaticNobundle |
425 NativeLibraryKind::NativeUnknown => {
426 if sess.target.target.options.is_like_msvc {
427 Some(format!("{}.lib", name))
429 Some(format!("-l{}", name))
432 NativeLibraryKind::NativeFramework => {
433 // ld-only syntax, since there are no frameworks in MSVC
434 Some(format!("-framework {}", name))
436 // These are included, no need to print them
437 NativeLibraryKind::NativeStatic => None,
441 if !lib_args.is_empty() {
442 sess.note_without_error("Link against the following native artifacts when linking \
443 against this static library. The order and any duplication \
444 can be significant on some platforms.");
445 // Prefix for greppability
446 sess.note_without_error(&format!("native-static-libs: {}", &lib_args.join(" ")));
450 fn get_file_path(sess: &Session, name: &str) -> PathBuf {
451 let fs = sess.target_filesearch(PathKind::Native);
452 let file_path = fs.get_lib_path().join(name);
453 if file_path.exists() {
456 for search_path in fs.search_paths() {
457 let file_path = search_path.dir.join(name);
458 if file_path.exists() {
465 // Create a dynamic library or executable
467 // This will invoke the system linker/cc to create the resulting file. This
468 // links to all upstream files as well.
469 fn link_natively(sess: &Session,
470 crate_type: config::CrateType,
472 codegen_results: &CodegenResults,
474 info!("preparing {:?} to {:?}", crate_type, out_filename);
475 let (linker, flavor) = linker_and_flavor(sess);
477 // The invocations of cc share some flags across platforms
478 let (pname, mut cmd) = get_linker(sess, &linker, flavor);
480 if let Some(args) = sess.target.target.options.pre_link_args.get(&flavor) {
483 if let Some(args) = sess.target.target.options.pre_link_args_crt.get(&flavor) {
484 if sess.crt_static() {
488 if let Some(ref args) = sess.opts.debugging_opts.pre_link_args {
491 cmd.args(&sess.opts.debugging_opts.pre_link_arg);
493 if sess.target.target.options.is_like_fuchsia {
494 let prefix = match sess.opts.debugging_opts.sanitizer {
495 Some(Sanitizer::Address) => "asan/",
498 cmd.arg(format!("--dynamic-linker={}ld.so.1", prefix));
501 let pre_link_objects = if crate_type == config::CrateType::Executable {
502 &sess.target.target.options.pre_link_objects_exe
504 &sess.target.target.options.pre_link_objects_dll
506 for obj in pre_link_objects {
507 cmd.arg(get_file_path(sess, obj));
510 if crate_type == config::CrateType::Executable && sess.crt_static() {
511 for obj in &sess.target.target.options.pre_link_objects_exe_crt {
512 cmd.arg(get_file_path(sess, obj));
516 if sess.target.target.options.is_like_emscripten {
518 cmd.arg(if sess.panic_strategy() == PanicStrategy::Abort {
519 "DISABLE_EXCEPTION_CATCHING=1"
521 "DISABLE_EXCEPTION_CATCHING=0"
526 let target_cpu = crate::llvm_util::target_cpu(sess);
527 let mut linker = codegen_results.linker_info.to_linker(cmd, &sess, flavor, target_cpu);
528 link_args(&mut *linker, flavor, sess, crate_type, tmpdir,
529 out_filename, codegen_results);
530 cmd = linker.finalize();
532 if let Some(args) = sess.target.target.options.late_link_args.get(&flavor) {
535 for obj in &sess.target.target.options.post_link_objects {
536 cmd.arg(get_file_path(sess, obj));
538 if sess.crt_static() {
539 for obj in &sess.target.target.options.post_link_objects_crt {
540 cmd.arg(get_file_path(sess, obj));
543 if let Some(args) = sess.target.target.options.post_link_args.get(&flavor) {
546 for &(ref k, ref v) in &sess.target.target.options.link_env {
550 if sess.opts.debugging_opts.print_link_args {
551 println!("{:?}", &cmd);
554 // May have not found libraries in the right formats.
555 sess.abort_if_errors();
557 // Invoke the system linker
559 // Note that there's a terribly awful hack that really shouldn't be present
560 // in any compiler. Here an environment variable is supported to
561 // automatically retry the linker invocation if the linker looks like it
564 // Gee that seems odd, normally segfaults are things we want to know about!
565 // Unfortunately though in rust-lang/rust#38878 we're experiencing the
566 // linker segfaulting on Travis quite a bit which is causing quite a bit of
567 // pain to land PRs when they spuriously fail due to a segfault.
569 // The issue #38878 has some more debugging information on it as well, but
570 // this unfortunately looks like it's just a race condition in macOS's linker
571 // with some thread pool working in the background. It seems that no one
572 // currently knows a fix for this so in the meantime we're left with this...
574 let retry_on_segfault = env::var("RUSTC_RETRY_LINKER_ON_SEGFAULT").is_ok();
579 prog = time(sess, "running linker", || {
580 exec_linker(sess, &mut cmd, out_filename, tmpdir)
582 let output = match prog {
583 Ok(ref output) => output,
586 if output.status.success() {
589 let mut out = output.stderr.clone();
590 out.extend(&output.stdout);
591 let out = String::from_utf8_lossy(&out);
593 // Check to see if the link failed with "unrecognized command line option:
594 // '-no-pie'" for gcc or "unknown argument: '-no-pie'" for clang. If so,
595 // reperform the link step without the -no-pie option. This is safe because
596 // if the linker doesn't support -no-pie then it should not default to
597 // linking executables as pie. Different versions of gcc seem to use
598 // different quotes in the error message so don't check for them.
599 if sess.target.target.options.linker_is_gnu &&
600 flavor != LinkerFlavor::Ld &&
601 (out.contains("unrecognized command line option") ||
602 out.contains("unknown argument")) &&
603 out.contains("-no-pie") &&
604 cmd.get_args().iter().any(|e| e.to_string_lossy() == "-no-pie") {
605 info!("linker output: {:?}", out);
606 warn!("Linker does not support -no-pie command line option. Retrying without.");
607 for arg in cmd.take_args() {
608 if arg.to_string_lossy() != "-no-pie" {
615 if !retry_on_segfault || i > 3 {
618 let msg_segv = "clang: error: unable to execute command: Segmentation fault: 11";
619 let msg_bus = "clang: error: unable to execute command: Bus error: 10";
620 if !(out.contains(msg_segv) || out.contains(msg_bus)) {
625 "looks like the linker segfaulted when we tried to call it, \
626 automatically retrying again. cmd = {:?}, out = {}.",
634 fn escape_string(s: &[u8]) -> String {
635 str::from_utf8(s).map(|s| s.to_owned())
636 .unwrap_or_else(|_| {
637 let mut x = "Non-UTF-8 output: ".to_string();
639 .flat_map(|&b| ascii::escape_default(b))
644 if !prog.status.success() {
645 let mut output = prog.stderr.clone();
646 output.extend_from_slice(&prog.stdout);
647 sess.struct_err(&format!("linking with `{}` failed: {}",
650 .note(&format!("{:?}", &cmd))
651 .note(&escape_string(&output))
653 sess.abort_if_errors();
655 info!("linker stderr:\n{}", escape_string(&prog.stderr));
656 info!("linker stdout:\n{}", escape_string(&prog.stdout));
659 let linker_not_found = e.kind() == io::ErrorKind::NotFound;
661 let mut linker_error = {
662 if linker_not_found {
663 sess.struct_err(&format!("linker `{}` not found", pname.display()))
665 sess.struct_err(&format!("could not exec the linker `{}`", pname.display()))
669 linker_error.note(&e.to_string());
671 if !linker_not_found {
672 linker_error.note(&format!("{:?}", &cmd));
677 if sess.target.target.options.is_like_msvc && linker_not_found {
678 sess.note_without_error("the msvc targets depend on the msvc linker \
679 but `link.exe` was not found");
680 sess.note_without_error("please ensure that VS 2013, VS 2015 or VS 2017 \
681 was installed with the Visual C++ option");
683 sess.abort_if_errors();
688 // On macOS, debuggers need this utility to get run to do some munging of
689 // the symbols. Note, though, that if the object files are being preserved
690 // for their debug information there's no need for us to run dsymutil.
691 if sess.target.target.options.is_like_osx &&
692 sess.opts.debuginfo != DebugInfo::None &&
693 !preserve_objects_for_their_debuginfo(sess)
695 if let Err(e) = Command::new("dsymutil").arg(out_filename).output() {
696 sess.fatal(&format!("failed to run dsymutil: {}", e))
700 if sess.opts.target_triple.triple() == "wasm32-unknown-unknown" {
701 wasm::add_producer_section(
703 &sess.edition().to_string(),
704 option_env!("CFG_VERSION").unwrap_or("unknown"),
709 fn exec_linker(sess: &Session, cmd: &mut Command, out_filename: &Path, tmpdir: &Path)
710 -> io::Result<Output>
712 // When attempting to spawn the linker we run a risk of blowing out the
713 // size limits for spawning a new process with respect to the arguments
714 // we pass on the command line.
716 // Here we attempt to handle errors from the OS saying "your list of
717 // arguments is too big" by reinvoking the linker again with an `@`-file
718 // that contains all the arguments. The theory is that this is then
719 // accepted on all linkers and the linker will read all its options out of
720 // there instead of looking at the command line.
721 if !cmd.very_likely_to_exceed_some_spawn_limit() {
722 match cmd.command().stdout(Stdio::piped()).stderr(Stdio::piped()).spawn() {
724 let output = child.wait_with_output();
725 flush_linked_file(&output, out_filename)?;
728 Err(ref e) if command_line_too_big(e) => {
729 info!("command line to linker was too big: {}", e);
731 Err(e) => return Err(e)
735 info!("falling back to passing arguments to linker via an @-file");
736 let mut cmd2 = cmd.clone();
737 let mut args = String::new();
738 for arg in cmd2.take_args() {
739 args.push_str(&Escape {
740 arg: arg.to_str().unwrap(),
741 is_like_msvc: sess.target.target.options.is_like_msvc,
745 let file = tmpdir.join("linker-arguments");
746 let bytes = if sess.target.target.options.is_like_msvc {
747 let mut out = Vec::with_capacity((1 + args.len()) * 2);
748 // start the stream with a UTF-16 BOM
749 for c in iter::once(0xFEFF).chain(args.encode_utf16()) {
750 // encode in little endian
752 out.push((c >> 8) as u8);
758 fs::write(&file, &bytes)?;
759 cmd2.arg(format!("@{}", file.display()));
760 info!("invoking linker {:?}", cmd2);
761 let output = cmd2.output();
762 flush_linked_file(&output, out_filename)?;
766 fn flush_linked_file(_: &io::Result<Output>, _: &Path) -> io::Result<()> {
771 fn flush_linked_file(command_output: &io::Result<Output>, out_filename: &Path)
774 // On Windows, under high I/O load, output buffers are sometimes not flushed,
775 // even long after process exit, causing nasty, non-reproducible output bugs.
777 // File::sync_all() calls FlushFileBuffers() down the line, which solves the problem.
779 // А full writeup of the original Chrome bug can be found at
780 // randomascii.wordpress.com/2018/02/25/compiler-bug-linker-bug-windows-kernel-bug/amp
782 if let &Ok(ref out) = command_output {
783 if out.status.success() {
784 if let Ok(of) = fs::OpenOptions::new().write(true).open(out_filename) {
794 fn command_line_too_big(err: &io::Error) -> bool {
795 err.raw_os_error() == Some(::libc::E2BIG)
799 fn command_line_too_big(err: &io::Error) -> bool {
800 const ERROR_FILENAME_EXCED_RANGE: i32 = 206;
801 err.raw_os_error() == Some(ERROR_FILENAME_EXCED_RANGE)
809 impl<'a> fmt::Display for Escape<'a> {
810 fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
811 if self.is_like_msvc {
812 // This is "documented" at
813 // https://msdn.microsoft.com/en-us/library/4xdcbak7.aspx
815 // Unfortunately there's not a great specification of the
816 // syntax I could find online (at least) but some local
817 // testing showed that this seemed sufficient-ish to catch
818 // at least a few edge cases.
820 for c in self.arg.chars() {
822 '"' => write!(f, "\\{}", c)?,
823 c => write!(f, "{}", c)?,
828 // This is documented at https://linux.die.net/man/1/ld, namely:
830 // > Options in file are separated by whitespace. A whitespace
831 // > character may be included in an option by surrounding the
832 // > entire option in either single or double quotes. Any
833 // > character (including a backslash) may be included by
834 // > prefixing the character to be included with a backslash.
836 // We put an argument on each line, so all we need to do is
837 // ensure the line is interpreted as one whole argument.
838 for c in self.arg.chars() {
840 '\\' | ' ' => write!(f, "\\{}", c)?,
841 c => write!(f, "{}", c)?,
850 fn link_args(cmd: &mut dyn Linker,
851 flavor: LinkerFlavor,
853 crate_type: config::CrateType,
856 codegen_results: &CodegenResults) {
858 // Linker plugins should be specified early in the list of arguments
859 cmd.linker_plugin_lto();
861 // The default library location, we need this to find the runtime.
862 // The location of crates will be determined as needed.
863 let lib_path = sess.target_filesearch(PathKind::All).get_lib_path();
866 let t = &sess.target.target;
868 cmd.include_path(&fix_windows_verbatim_for_gcc(&lib_path));
869 for obj in codegen_results.modules.iter().filter_map(|m| m.object.as_ref()) {
872 cmd.output_filename(out_filename);
874 if crate_type == config::CrateType::Executable &&
875 sess.target.target.options.is_like_windows {
876 if let Some(ref s) = codegen_results.windows_subsystem {
881 // If we're building a dynamic library then some platforms need to make sure
882 // that all symbols are exported correctly from the dynamic library.
883 if crate_type != config::CrateType::Executable ||
884 sess.target.target.options.is_like_emscripten {
885 cmd.export_symbols(tmpdir, crate_type);
888 // When linking a dynamic library, we put the metadata into a section of the
889 // executable. This metadata is in a separate object file from the main
890 // object file, so we link that in here.
891 if crate_type == config::CrateType::Dylib ||
892 crate_type == config::CrateType::ProcMacro {
893 if let Some(obj) = codegen_results.metadata_module.object.as_ref() {
898 let obj = codegen_results.allocator_module
900 .and_then(|m| m.object.as_ref());
901 if let Some(obj) = obj {
905 // Try to strip as much out of the generated object by removing unused
906 // sections if possible. See more comments in linker.rs
907 if !sess.opts.cg.link_dead_code {
908 let keep_metadata = crate_type == config::CrateType::Dylib;
909 cmd.gc_sections(keep_metadata);
912 let used_link_args = &codegen_results.crate_info.link_args;
914 if crate_type == config::CrateType::Executable {
915 let mut position_independent_executable = false;
917 if t.options.position_independent_executables {
918 let empty_vec = Vec::new();
919 let args = sess.opts.cg.link_args.as_ref().unwrap_or(&empty_vec);
920 let more_args = &sess.opts.cg.link_arg;
921 let mut args = args.iter().chain(more_args.iter()).chain(used_link_args.iter());
923 if get_reloc_model(sess) == llvm::RelocMode::PIC
924 && !sess.crt_static() && !args.any(|x| *x == "-static") {
925 position_independent_executable = true;
929 if position_independent_executable {
930 cmd.position_independent_executable();
932 // recent versions of gcc can be configured to generate position
933 // independent executables by default. We have to pass -no-pie to
934 // explicitly turn that off. Not applicable to ld.
935 if sess.target.target.options.linker_is_gnu
936 && flavor != LinkerFlavor::Ld {
937 cmd.no_position_independent_executable();
942 let relro_level = match sess.opts.debugging_opts.relro_level {
943 Some(level) => level,
944 None => t.options.relro_level,
947 RelroLevel::Full => {
950 RelroLevel::Partial => {
956 RelroLevel::None => {
960 // Pass optimization flags down to the linker.
963 // Pass debuginfo flags down to the linker.
966 // We want to, by default, prevent the compiler from accidentally leaking in
967 // any system libraries, so we may explicitly ask linkers to not link to any
968 // libraries by default. Note that this does not happen for windows because
969 // windows pulls in some large number of libraries and I couldn't quite
970 // figure out which subset we wanted.
972 // This is all naturally configurable via the standard methods as well.
973 if !sess.opts.cg.default_linker_libraries.unwrap_or(false) &&
974 t.options.no_default_libraries
976 cmd.no_default_libraries();
979 // Take careful note of the ordering of the arguments we pass to the linker
980 // here. Linkers will assume that things on the left depend on things to the
981 // right. Things on the right cannot depend on things on the left. This is
982 // all formally implemented in terms of resolving symbols (libs on the right
983 // resolve unknown symbols of libs on the left, but not vice versa).
985 // For this reason, we have organized the arguments we pass to the linker as
988 // 1. The local object that LLVM just generated
989 // 2. Local native libraries
990 // 3. Upstream rust libraries
991 // 4. Upstream native libraries
993 // The rationale behind this ordering is that those items lower down in the
994 // list can't depend on items higher up in the list. For example nothing can
995 // depend on what we just generated (e.g., that'd be a circular dependency).
996 // Upstream rust libraries are not allowed to depend on our local native
997 // libraries as that would violate the structure of the DAG, in that
998 // scenario they are required to link to them as well in a shared fashion.
1000 // Note that upstream rust libraries may contain native dependencies as
1001 // well, but they also can't depend on what we just started to add to the
1002 // link line. And finally upstream native libraries can't depend on anything
1003 // in this DAG so far because they're only dylibs and dylibs can only depend
1004 // on other dylibs (e.g., other native deps).
1005 add_local_native_libraries(cmd, sess, codegen_results);
1006 add_upstream_rust_crates(cmd, sess, codegen_results, crate_type, tmpdir);
1007 add_upstream_native_libraries(cmd, sess, codegen_results, crate_type);
1009 // Tell the linker what we're doing.
1010 if crate_type != config::CrateType::Executable {
1011 cmd.build_dylib(out_filename);
1013 if crate_type == config::CrateType::Executable && sess.crt_static() {
1014 cmd.build_static_executable();
1017 if sess.opts.debugging_opts.pgo_gen.is_some() {
1021 // FIXME (#2397): At some point we want to rpath our guesses as to
1022 // where extern libraries might live, based on the
1023 // addl_lib_search_paths
1024 if sess.opts.cg.rpath {
1025 let target_triple = sess.opts.target_triple.triple();
1026 let mut get_install_prefix_lib_path = || {
1027 let install_prefix = option_env!("CFG_PREFIX").expect("CFG_PREFIX");
1028 let tlib = filesearch::relative_target_lib_path(&sess.sysroot, target_triple);
1029 let mut path = PathBuf::from(install_prefix);
1034 let mut rpath_config = RPathConfig {
1035 used_crates: &codegen_results.crate_info.used_crates_dynamic,
1036 out_filename: out_filename.to_path_buf(),
1037 has_rpath: sess.target.target.options.has_rpath,
1038 is_like_osx: sess.target.target.options.is_like_osx,
1039 linker_is_gnu: sess.target.target.options.linker_is_gnu,
1040 get_install_prefix_lib_path: &mut get_install_prefix_lib_path,
1042 cmd.args(&rpath::get_rpath_flags(&mut rpath_config));
1045 // Finally add all the linker arguments provided on the command line along
1046 // with any #[link_args] attributes found inside the crate
1047 if let Some(ref args) = sess.opts.cg.link_args {
1050 cmd.args(&sess.opts.cg.link_arg);
1051 cmd.args(&used_link_args);
1054 // # Native library linking
1056 // User-supplied library search paths (-L on the command line). These are
1057 // the same paths used to find Rust crates, so some of them may have been
1058 // added already by the previous crate linking code. This only allows them
1059 // to be found at compile time so it is still entirely up to outside
1060 // forces to make sure that library can be found at runtime.
1062 // Also note that the native libraries linked here are only the ones located
1063 // in the current crate. Upstream crates with native library dependencies
1064 // may have their native library pulled in above.
1065 fn add_local_native_libraries(cmd: &mut dyn Linker,
1067 codegen_results: &CodegenResults) {
1068 let filesearch = sess.target_filesearch(PathKind::All);
1069 for search_path in filesearch.search_paths() {
1070 match search_path.kind {
1071 PathKind::Framework => { cmd.framework_path(&search_path.dir); }
1072 _ => { cmd.include_path(&fix_windows_verbatim_for_gcc(&search_path.dir)); }
1076 let relevant_libs = codegen_results.crate_info.used_libraries.iter().filter(|l| {
1077 relevant_lib(sess, l)
1080 let search_path = archive_search_paths(sess);
1081 for lib in relevant_libs {
1082 let name = match lib.name {
1087 NativeLibraryKind::NativeUnknown => cmd.link_dylib(&name.as_str()),
1088 NativeLibraryKind::NativeFramework => cmd.link_framework(&name.as_str()),
1089 NativeLibraryKind::NativeStaticNobundle => cmd.link_staticlib(&name.as_str()),
1090 NativeLibraryKind::NativeStatic => cmd.link_whole_staticlib(&name.as_str(),
1096 // # Rust Crate linking
1098 // Rust crates are not considered at all when creating an rlib output. All
1099 // dependencies will be linked when producing the final output (instead of
1100 // the intermediate rlib version)
1101 fn add_upstream_rust_crates(cmd: &mut dyn Linker,
1103 codegen_results: &CodegenResults,
1104 crate_type: config::CrateType,
1106 // All of the heavy lifting has previously been accomplished by the
1107 // dependency_format module of the compiler. This is just crawling the
1108 // output of that module, adding crates as necessary.
1110 // Linking to a rlib involves just passing it to the linker (the linker
1111 // will slurp up the object files inside), and linking to a dynamic library
1112 // involves just passing the right -l flag.
1114 let formats = sess.dependency_formats.borrow();
1115 let data = formats.get(&crate_type).unwrap();
1117 // Invoke get_used_crates to ensure that we get a topological sorting of
1119 let deps = &codegen_results.crate_info.used_crates_dynamic;
1121 // There's a few internal crates in the standard library (aka libcore and
1122 // libstd) which actually have a circular dependence upon one another. This
1123 // currently arises through "weak lang items" where libcore requires things
1124 // like `rust_begin_unwind` but libstd ends up defining it. To get this
1125 // circular dependence to work correctly in all situations we'll need to be
1126 // sure to correctly apply the `--start-group` and `--end-group` options to
1127 // GNU linkers, otherwise if we don't use any other symbol from the standard
1128 // library it'll get discarded and the whole application won't link.
1130 // In this loop we're calculating the `group_end`, after which crate to
1131 // pass `--end-group` and `group_start`, before which crate to pass
1132 // `--start-group`. We currently do this by passing `--end-group` after
1133 // the first crate (when iterating backwards) that requires a lang item
1134 // defined somewhere else. Once that's set then when we've defined all the
1135 // necessary lang items we'll pass `--start-group`.
1137 // Note that this isn't amazing logic for now but it should do the trick
1138 // for the current implementation of the standard library.
1139 let mut group_end = None;
1140 let mut group_start = None;
1141 let mut end_with = FxHashSet::default();
1142 let info = &codegen_results.crate_info;
1143 for &(cnum, _) in deps.iter().rev() {
1144 if let Some(missing) = info.missing_lang_items.get(&cnum) {
1145 end_with.extend(missing.iter().cloned());
1146 if end_with.len() > 0 && group_end.is_none() {
1147 group_end = Some(cnum);
1150 end_with.retain(|item| info.lang_item_to_crate.get(item) != Some(&cnum));
1151 if end_with.len() == 0 && group_end.is_some() {
1152 group_start = Some(cnum);
1157 // If we didn't end up filling in all lang items from upstream crates then
1158 // we'll be filling it in with our crate. This probably means we're the
1159 // standard library itself, so skip this for now.
1160 if group_end.is_some() && group_start.is_none() {
1164 let mut compiler_builtins = None;
1166 for &(cnum, _) in deps.iter() {
1167 if group_start == Some(cnum) {
1171 // We may not pass all crates through to the linker. Some crates may
1172 // appear statically in an existing dylib, meaning we'll pick up all the
1173 // symbols from the dylib.
1174 let src = &codegen_results.crate_info.used_crate_source[&cnum];
1175 match data[cnum.as_usize() - 1] {
1176 _ if codegen_results.crate_info.profiler_runtime == Some(cnum) => {
1177 add_static_crate(cmd, sess, codegen_results, tmpdir, crate_type, cnum);
1179 _ if codegen_results.crate_info.sanitizer_runtime == Some(cnum) => {
1180 link_sanitizer_runtime(cmd, sess, codegen_results, tmpdir, cnum);
1182 // compiler-builtins are always placed last to ensure that they're
1183 // linked correctly.
1184 _ if codegen_results.crate_info.compiler_builtins == Some(cnum) => {
1185 assert!(compiler_builtins.is_none());
1186 compiler_builtins = Some(cnum);
1188 Linkage::NotLinked |
1189 Linkage::IncludedFromDylib => {}
1190 Linkage::Static => {
1191 add_static_crate(cmd, sess, codegen_results, tmpdir, crate_type, cnum);
1193 Linkage::Dynamic => {
1194 add_dynamic_crate(cmd, sess, &src.dylib.as_ref().unwrap().0)
1198 if group_end == Some(cnum) {
1203 // compiler-builtins are always placed last to ensure that they're
1204 // linked correctly.
1205 // We must always link the `compiler_builtins` crate statically. Even if it
1206 // was already "included" in a dylib (e.g., `libstd` when `-C prefer-dynamic`
1208 if let Some(cnum) = compiler_builtins {
1209 add_static_crate(cmd, sess, codegen_results, tmpdir, crate_type, cnum);
1212 // Converts a library file-stem into a cc -l argument
1213 fn unlib<'a>(config: &config::Config, stem: &'a str) -> &'a str {
1214 if stem.starts_with("lib") && !config.target.options.is_like_windows {
1221 // We must link the sanitizer runtime using -Wl,--whole-archive but since
1222 // it's packed in a .rlib, it contains stuff that are not objects that will
1223 // make the linker error. So we must remove those bits from the .rlib before
1225 fn link_sanitizer_runtime(cmd: &mut dyn Linker,
1227 codegen_results: &CodegenResults,
1230 let src = &codegen_results.crate_info.used_crate_source[&cnum];
1231 let cratepath = &src.rlib.as_ref().unwrap().0;
1233 if sess.target.target.options.is_like_osx {
1234 // On Apple platforms, the sanitizer is always built as a dylib, and
1235 // LLVM will link to `@rpath/*.dylib`, so we need to specify an
1236 // rpath to the library as well (the rpath should be absolute, see
1237 // PR #41352 for details).
1239 // FIXME: Remove this logic into librustc_*san once Cargo supports it
1240 let rpath = cratepath.parent().unwrap();
1241 let rpath = rpath.to_str().expect("non-utf8 component in path");
1242 cmd.args(&["-Wl,-rpath".into(), "-Xlinker".into(), rpath.into()]);
1245 let dst = tmpdir.join(cratepath.file_name().unwrap());
1246 let cfg = archive_config(sess, &dst, Some(cratepath));
1247 let mut archive = ArchiveBuilder::new(cfg);
1248 archive.update_symbols();
1250 for f in archive.src_files() {
1251 if f.ends_with(RLIB_BYTECODE_EXTENSION) || f == METADATA_FILENAME {
1252 archive.remove_file(&f);
1258 cmd.link_whole_rlib(&dst);
1261 // Adds the static "rlib" versions of all crates to the command line.
1262 // There's a bit of magic which happens here specifically related to LTO and
1263 // dynamic libraries. Specifically:
1265 // * For LTO, we remove upstream object files.
1266 // * For dylibs we remove metadata and bytecode from upstream rlibs
1268 // When performing LTO, almost(*) all of the bytecode from the upstream
1269 // libraries has already been included in our object file output. As a
1270 // result we need to remove the object files in the upstream libraries so
1271 // the linker doesn't try to include them twice (or whine about duplicate
1272 // symbols). We must continue to include the rest of the rlib, however, as
1273 // it may contain static native libraries which must be linked in.
1275 // (*) Crates marked with `#![no_builtins]` don't participate in LTO and
1276 // their bytecode wasn't included. The object files in those libraries must
1277 // still be passed to the linker.
1279 // When making a dynamic library, linkers by default don't include any
1280 // object files in an archive if they're not necessary to resolve the link.
1281 // We basically want to convert the archive (rlib) to a dylib, though, so we
1282 // *do* want everything included in the output, regardless of whether the
1283 // linker thinks it's needed or not. As a result we must use the
1284 // --whole-archive option (or the platform equivalent). When using this
1285 // option the linker will fail if there are non-objects in the archive (such
1286 // as our own metadata and/or bytecode). All in all, for rlibs to be
1287 // entirely included in dylibs, we need to remove all non-object files.
1289 // Note, however, that if we're not doing LTO or we're not producing a dylib
1290 // (aka we're making an executable), we can just pass the rlib blindly to
1291 // the linker (fast) because it's fine if it's not actually included as
1292 // we're at the end of the dependency chain.
1293 fn add_static_crate(cmd: &mut dyn Linker,
1295 codegen_results: &CodegenResults,
1297 crate_type: config::CrateType,
1299 let src = &codegen_results.crate_info.used_crate_source[&cnum];
1300 let cratepath = &src.rlib.as_ref().unwrap().0;
1302 // See the comment above in `link_staticlib` and `link_rlib` for why if
1303 // there's a static library that's not relevant we skip all object
1305 let native_libs = &codegen_results.crate_info.native_libraries[&cnum];
1306 let skip_native = native_libs.iter().any(|lib| {
1307 lib.kind == NativeLibraryKind::NativeStatic && !relevant_lib(sess, lib)
1310 if (!are_upstream_rust_objects_already_included(sess) ||
1311 ignored_for_lto(sess, &codegen_results.crate_info, cnum)) &&
1312 crate_type != config::CrateType::Dylib &&
1314 cmd.link_rlib(&fix_windows_verbatim_for_gcc(cratepath));
1318 let dst = tmpdir.join(cratepath.file_name().unwrap());
1319 let name = cratepath.file_name().unwrap().to_str().unwrap();
1320 let name = &name[3..name.len() - 5]; // chop off lib/.rlib
1322 time(sess, &format!("altering {}.rlib", name), || {
1323 let cfg = archive_config(sess, &dst, Some(cratepath));
1324 let mut archive = ArchiveBuilder::new(cfg);
1325 archive.update_symbols();
1327 let mut any_objects = false;
1328 for f in archive.src_files() {
1329 if f.ends_with(RLIB_BYTECODE_EXTENSION) || f == METADATA_FILENAME {
1330 archive.remove_file(&f);
1334 let canonical = f.replace("-", "_");
1335 let canonical_name = name.replace("-", "_");
1337 // Look for `.rcgu.o` at the end of the filename to conclude
1338 // that this is a Rust-related object file.
1339 fn looks_like_rust(s: &str) -> bool {
1340 let path = Path::new(s);
1341 let ext = path.extension().and_then(|s| s.to_str());
1342 if ext != Some(OutputType::Object.extension()) {
1345 let ext2 = path.file_stem()
1346 .and_then(|s| Path::new(s).extension())
1347 .and_then(|s| s.to_str());
1348 ext2 == Some(RUST_CGU_EXT)
1351 let is_rust_object =
1352 canonical.starts_with(&canonical_name) &&
1353 looks_like_rust(&f);
1355 // If we've been requested to skip all native object files
1356 // (those not generated by the rust compiler) then we can skip
1357 // this file. See above for why we may want to do this.
1358 let skip_because_cfg_say_so = skip_native && !is_rust_object;
1360 // If we're performing LTO and this is a rust-generated object
1361 // file, then we don't need the object file as it's part of the
1362 // LTO module. Note that `#![no_builtins]` is excluded from LTO,
1363 // though, so we let that object file slide.
1364 let skip_because_lto = are_upstream_rust_objects_already_included(sess) &&
1366 (sess.target.target.options.no_builtins ||
1367 !codegen_results.crate_info.is_no_builtins.contains(&cnum));
1369 if skip_because_cfg_say_so || skip_because_lto {
1370 archive.remove_file(&f);
1381 // If we're creating a dylib, then we need to include the
1382 // whole of each object in our archive into that artifact. This is
1383 // because a `dylib` can be reused as an intermediate artifact.
1385 // Note, though, that we don't want to include the whole of a
1386 // compiler-builtins crate (e.g., compiler-rt) because it'll get
1387 // repeatedly linked anyway.
1388 if crate_type == config::CrateType::Dylib &&
1389 codegen_results.crate_info.compiler_builtins != Some(cnum) {
1390 cmd.link_whole_rlib(&fix_windows_verbatim_for_gcc(&dst));
1392 cmd.link_rlib(&fix_windows_verbatim_for_gcc(&dst));
1397 // Same thing as above, but for dynamic crates instead of static crates.
1398 fn add_dynamic_crate(cmd: &mut dyn Linker, sess: &Session, cratepath: &Path) {
1399 // If we're performing LTO, then it should have been previously required
1400 // that all upstream rust dependencies were available in an rlib format.
1401 assert!(!are_upstream_rust_objects_already_included(sess));
1403 // Just need to tell the linker about where the library lives and
1405 let parent = cratepath.parent();
1406 if let Some(dir) = parent {
1407 cmd.include_path(&fix_windows_verbatim_for_gcc(dir));
1409 let filestem = cratepath.file_stem().unwrap().to_str().unwrap();
1410 cmd.link_rust_dylib(&unlib(&sess.target, filestem),
1411 parent.unwrap_or(Path::new("")));
1415 // Link in all of our upstream crates' native dependencies. Remember that
1416 // all of these upstream native dependencies are all non-static
1417 // dependencies. We've got two cases then:
1419 // 1. The upstream crate is an rlib. In this case we *must* link in the
1420 // native dependency because the rlib is just an archive.
1422 // 2. The upstream crate is a dylib. In order to use the dylib, we have to
1423 // have the dependency present on the system somewhere. Thus, we don't
1424 // gain a whole lot from not linking in the dynamic dependency to this
1427 // The use case for this is a little subtle. In theory the native
1428 // dependencies of a crate are purely an implementation detail of the crate
1429 // itself, but the problem arises with generic and inlined functions. If a
1430 // generic function calls a native function, then the generic function must
1431 // be instantiated in the target crate, meaning that the native symbol must
1432 // also be resolved in the target crate.
1433 fn add_upstream_native_libraries(cmd: &mut dyn Linker,
1435 codegen_results: &CodegenResults,
1436 crate_type: config::CrateType) {
1437 // Be sure to use a topological sorting of crates because there may be
1438 // interdependencies between native libraries. When passing -nodefaultlibs,
1439 // for example, almost all native libraries depend on libc, so we have to
1440 // make sure that's all the way at the right (liblibc is near the base of
1441 // the dependency chain).
1443 // This passes RequireStatic, but the actual requirement doesn't matter,
1444 // we're just getting an ordering of crate numbers, we're not worried about
1446 let formats = sess.dependency_formats.borrow();
1447 let data = formats.get(&crate_type).unwrap();
1449 let crates = &codegen_results.crate_info.used_crates_static;
1450 for &(cnum, _) in crates {
1451 for lib in codegen_results.crate_info.native_libraries[&cnum].iter() {
1452 let name = match lib.name {
1456 if !relevant_lib(sess, &lib) {
1460 NativeLibraryKind::NativeUnknown => cmd.link_dylib(&name.as_str()),
1461 NativeLibraryKind::NativeFramework => cmd.link_framework(&name.as_str()),
1462 NativeLibraryKind::NativeStaticNobundle => {
1463 // Link "static-nobundle" native libs only if the crate they originate from
1464 // is being linked statically to the current crate. If it's linked dynamically
1465 // or is an rlib already included via some other dylib crate, the symbols from
1466 // native libs will have already been included in that dylib.
1467 if data[cnum.as_usize() - 1] == Linkage::Static {
1468 cmd.link_staticlib(&name.as_str())
1471 // ignore statically included native libraries here as we've
1472 // already included them when we included the rust library
1474 NativeLibraryKind::NativeStatic => {}
1480 fn relevant_lib(sess: &Session, lib: &NativeLibrary) -> bool {
1482 Some(ref cfg) => attr::cfg_matches(cfg, &sess.parse_sess, None),
1487 fn are_upstream_rust_objects_already_included(sess: &Session) -> bool {
1491 // If we defer LTO to the linker, we haven't run LTO ourselves, so
1492 // any upstream object files have not been copied yet.
1493 !sess.opts.cg.linker_plugin_lto.enabled()
1496 Lto::ThinLocal => false,