1 // Copyright 2012-2014 The Rust Project Developers. See the COPYRIGHT
2 // file at the top-level directory of this distribution and at
3 // http://rust-lang.org/COPYRIGHT.
5 // Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
6 // http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
7 // <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
8 // option. This file may not be copied, modified, or distributed
9 // except according to those terms.
11 use cc::windows_registry;
12 use super::archive::{ArchiveBuilder, ArchiveConfig};
13 use super::bytecode::RLIB_BYTECODE_EXTENSION;
14 use super::linker::Linker;
15 use super::command::Command;
16 use super::rpath::RPathConfig;
18 use metadata::METADATA_FILENAME;
19 use rustc_back::LinkerFlavor;
20 use rustc::session::config::{self, NoDebugInfo, OutputFilenames, OutputType, PrintRequest};
21 use rustc::session::config::{RUST_CGU_EXT, Lto};
22 use rustc::session::filesearch;
23 use rustc::session::search_paths::PathKind;
24 use rustc::session::Session;
25 use rustc::middle::cstore::{NativeLibrary, LibSource, NativeLibraryKind};
26 use rustc::middle::dependency_format::Linkage;
27 use {CrateTranslation, CrateInfo};
28 use rustc::util::common::time;
29 use rustc::util::fs::fix_windows_verbatim_for_gcc;
30 use rustc::hir::def_id::CrateNum;
32 use rustc_back::{PanicStrategy, RelroLevel};
33 use context::get_reloc_model;
42 use std::path::{Path, PathBuf};
43 use std::process::{Output, Stdio};
47 /// The LLVM module name containing crate-metadata. This includes a `.` on
48 /// purpose, so it cannot clash with the name of a user-defined module.
49 pub const METADATA_MODULE_NAME: &'static str = "crate.metadata";
51 // same as for metadata above, but for allocator shim
52 pub const ALLOCATOR_MODULE_NAME: &'static str = "crate.allocator";
54 pub use rustc_trans_utils::link::{find_crate_name, filename_for_input, default_output_for_target,
55 invalid_output_for_target, build_link_meta, out_filename,
56 check_file_is_writeable};
58 // The third parameter is for env vars, used on windows to set up the
59 // path for MSVC to find its DLLs, and gcc to find its bundled
61 pub fn get_linker(sess: &Session) -> (PathBuf, Command) {
62 // If our linker looks like a batch script on Windows then to execute this
63 // we'll need to spawn `cmd` explicitly. This is primarily done to handle
64 // emscripten where the linker is `emcc.bat` and needs to be spawned as
65 // `cmd /c emcc.bat ...`.
67 // This worked historically but is needed manually since #42436 (regression
68 // was tagged as #42791) and some more info can be found on #44443 for
70 let cmd = |linker: &Path| {
71 if let Some(linker) = linker.to_str() {
72 if cfg!(windows) && linker.ends_with(".bat") {
73 return Command::bat_script(linker)
76 match sess.linker_flavor() {
77 LinkerFlavor::Lld(f) => Command::lld(linker, f),
78 _ => Command::new(linker),
83 let msvc_tool = windows_registry::find_tool(&sess.opts.target_triple, "link.exe");
85 let linker_path = sess.opts.cg.linker.as_ref().map(|s| &**s)
86 .or(sess.target.target.options.linker.as_ref().map(|s| s.as_ref()))
87 .unwrap_or(match sess.linker_flavor() {
88 LinkerFlavor::Msvc => {
89 msvc_tool.as_ref().map(|t| t.path()).unwrap_or("link.exe".as_ref())
91 LinkerFlavor::Em if cfg!(windows) => "emcc.bat".as_ref(),
92 LinkerFlavor::Em => "emcc".as_ref(),
93 LinkerFlavor::Gcc => "cc".as_ref(),
94 LinkerFlavor::Ld => "ld".as_ref(),
95 LinkerFlavor::Lld(_) => "lld".as_ref(),
98 let mut cmd = cmd(linker_path);
100 // The compiler's sysroot often has some bundled tools, so add it to the
101 // PATH for the child.
102 let mut new_path = sess.host_filesearch(PathKind::All)
103 .get_tools_search_paths();
104 let mut msvc_changed_path = false;
105 if sess.target.target.options.is_like_msvc {
106 if let Some(ref tool) = msvc_tool {
107 cmd.args(tool.args());
108 for &(ref k, ref v) in tool.env() {
110 new_path.extend(env::split_paths(v));
111 msvc_changed_path = true;
119 if !msvc_changed_path {
120 if let Some(path) = env::var_os("PATH") {
121 new_path.extend(env::split_paths(&path));
124 cmd.env("PATH", env::join_paths(new_path).unwrap());
126 (linker_path.to_path_buf(), cmd)
129 pub fn remove(sess: &Session, path: &Path) {
130 match fs::remove_file(path) {
133 sess.err(&format!("failed to remove {}: {}",
140 /// Perform the linkage portion of the compilation phase. This will generate all
141 /// of the requested outputs for this compilation session.
142 pub(crate) fn link_binary(sess: &Session,
143 trans: &CrateTranslation,
144 outputs: &OutputFilenames,
145 crate_name: &str) -> Vec<PathBuf> {
146 let mut out_filenames = Vec::new();
147 for &crate_type in sess.crate_types.borrow().iter() {
148 // Ignore executable crates if we have -Z no-trans, as they will error.
149 if (sess.opts.debugging_opts.no_trans ||
150 !sess.opts.output_types.should_trans()) &&
151 crate_type == config::CrateTypeExecutable {
155 if invalid_output_for_target(sess, crate_type) {
156 bug!("invalid output type `{:?}` for target os `{}`",
157 crate_type, sess.opts.target_triple);
159 let mut out_files = link_binary_output(sess,
164 out_filenames.append(&mut out_files);
167 // Remove the temporary object file and metadata if we aren't saving temps
168 if !sess.opts.cg.save_temps {
169 if sess.opts.output_types.should_trans() &&
170 !preserve_objects_for_their_debuginfo(sess)
172 for obj in trans.modules.iter().filter_map(|m| m.object.as_ref()) {
176 for obj in trans.modules.iter().filter_map(|m| m.bytecode_compressed.as_ref()) {
179 if let Some(ref obj) = trans.metadata_module.object {
182 if let Some(ref allocator) = trans.allocator_module {
183 if let Some(ref obj) = allocator.object {
186 if let Some(ref bc) = allocator.bytecode_compressed {
195 /// Returns a boolean indicating whether we should preserve the object files on
196 /// the filesystem for their debug information. This is often useful with
197 /// split-dwarf like schemes.
198 fn preserve_objects_for_their_debuginfo(sess: &Session) -> bool {
199 // If the objects don't have debuginfo there's nothing to preserve.
200 if sess.opts.debuginfo == NoDebugInfo {
204 // If we're only producing artifacts that are archives, no need to preserve
205 // the objects as they're losslessly contained inside the archives.
206 let output_linked = sess.crate_types.borrow()
208 .any(|x| *x != config::CrateTypeRlib && *x != config::CrateTypeStaticlib);
213 // If we're on OSX then the equivalent of split dwarf is turned on by
214 // default. The final executable won't actually have any debug information
215 // except it'll have pointers to elsewhere. Historically we've always run
216 // `dsymutil` to "link all the dwarf together" but this is actually sort of
217 // a bummer for incremental compilation! (the whole point of split dwarf is
218 // that you don't do this sort of dwarf link).
220 // Basically as a result this just means that if we're on OSX and we're
221 // *not* running dsymutil then the object files are the only source of truth
222 // for debug information, so we must preserve them.
223 if sess.target.target.options.is_like_osx {
224 match sess.opts.debugging_opts.run_dsymutil {
225 // dsymutil is not being run, preserve objects
226 Some(false) => return true,
228 // dsymutil is being run, no need to preserve the objects
229 Some(true) => return false,
231 // The default historical behavior was to always run dsymutil, so
232 // we're preserving that temporarily, but we're likely to switch the
234 None => return false,
241 fn filename_for_metadata(sess: &Session, crate_name: &str, outputs: &OutputFilenames) -> PathBuf {
242 let out_filename = outputs.single_output_file.clone()
245 .join(&format!("lib{}{}.rmeta", crate_name, sess.opts.cg.extra_filename)));
246 check_file_is_writeable(&out_filename, sess);
250 pub(crate) fn each_linked_rlib(sess: &Session,
252 f: &mut FnMut(CrateNum, &Path)) -> Result<(), String> {
253 let crates = info.used_crates_static.iter();
254 let fmts = sess.dependency_formats.borrow();
255 let fmts = fmts.get(&config::CrateTypeExecutable)
256 .or_else(|| fmts.get(&config::CrateTypeStaticlib))
257 .or_else(|| fmts.get(&config::CrateTypeCdylib))
258 .or_else(|| fmts.get(&config::CrateTypeProcMacro));
259 let fmts = match fmts {
261 None => return Err(format!("could not find formats for rlibs"))
263 for &(cnum, ref path) in crates {
264 match fmts.get(cnum.as_usize() - 1) {
265 Some(&Linkage::NotLinked) |
266 Some(&Linkage::IncludedFromDylib) => continue,
268 None => return Err(format!("could not find formats for rlibs"))
270 let name = &info.crate_name[&cnum];
271 let path = match *path {
272 LibSource::Some(ref p) => p,
273 LibSource::MetadataOnly => {
274 return Err(format!("could not find rlib for: `{}`, found rmeta (metadata) file",
278 return Err(format!("could not find rlib for: `{}`", name))
286 /// Returns a boolean indicating whether the specified crate should be ignored
289 /// Crates ignored during LTO are not lumped together in the "massive object
290 /// file" that we create and are linked in their normal rlib states. See
291 /// comments below for what crates do not participate in LTO.
293 /// It's unusual for a crate to not participate in LTO. Typically only
294 /// compiler-specific and unstable crates have a reason to not participate in
296 pub(crate) fn ignored_for_lto(sess: &Session, info: &CrateInfo, cnum: CrateNum) -> bool {
297 // If our target enables builtin function lowering in LLVM then the
298 // crates providing these functions don't participate in LTO (e.g.
299 // no_builtins or compiler builtins crates).
300 !sess.target.target.options.no_builtins &&
301 (info.is_no_builtins.contains(&cnum) || info.compiler_builtins == Some(cnum))
304 fn link_binary_output(sess: &Session,
305 trans: &CrateTranslation,
306 crate_type: config::CrateType,
307 outputs: &OutputFilenames,
308 crate_name: &str) -> Vec<PathBuf> {
309 for obj in trans.modules.iter().filter_map(|m| m.object.as_ref()) {
310 check_file_is_writeable(obj, sess);
313 let mut out_filenames = vec![];
315 if outputs.outputs.contains_key(&OutputType::Metadata) {
316 let out_filename = filename_for_metadata(sess, crate_name, outputs);
317 // To avoid races with another rustc process scanning the output directory,
318 // we need to write the file somewhere else and atomically move it to its
319 // final destination, with a `fs::rename` call. In order for the rename to
320 // always succeed, the temporary file needs to be on the same filesystem,
321 // which is why we create it inside the output directory specifically.
322 let metadata_tmpdir = match TempDir::new_in(out_filename.parent().unwrap(), "rmeta") {
323 Ok(tmpdir) => tmpdir,
324 Err(err) => sess.fatal(&format!("couldn't create a temp dir: {}", err)),
326 let metadata = emit_metadata(sess, trans, &metadata_tmpdir);
327 if let Err(e) = fs::rename(metadata, &out_filename) {
328 sess.fatal(&format!("failed to write {}: {}", out_filename.display(), e));
330 out_filenames.push(out_filename);
333 let tmpdir = match TempDir::new("rustc") {
334 Ok(tmpdir) => tmpdir,
335 Err(err) => sess.fatal(&format!("couldn't create a temp dir: {}", err)),
338 if outputs.outputs.should_trans() {
339 let out_filename = out_filename(sess, crate_type, outputs, crate_name);
341 config::CrateTypeRlib => {
348 config::CrateTypeStaticlib => {
349 link_staticlib(sess, trans, &out_filename, &tmpdir);
352 link_natively(sess, crate_type, &out_filename, trans, tmpdir.path());
355 out_filenames.push(out_filename);
358 if sess.opts.cg.save_temps {
359 let _ = tmpdir.into_path();
365 fn archive_search_paths(sess: &Session) -> Vec<PathBuf> {
366 let mut search = Vec::new();
367 sess.target_filesearch(PathKind::Native).for_each_lib_search_path(|path, _| {
368 search.push(path.to_path_buf());
373 fn archive_config<'a>(sess: &'a Session,
375 input: Option<&Path>) -> ArchiveConfig<'a> {
378 dst: output.to_path_buf(),
379 src: input.map(|p| p.to_path_buf()),
380 lib_search_paths: archive_search_paths(sess),
384 /// We use a temp directory here to avoid races between concurrent rustc processes,
385 /// such as builds in the same directory using the same filename for metadata while
386 /// building an `.rlib` (stomping over one another), or writing an `.rmeta` into a
387 /// directory being searched for `extern crate` (observing an incomplete file).
388 /// The returned path is the temporary file containing the complete metadata.
389 fn emit_metadata<'a>(sess: &'a Session, trans: &CrateTranslation, tmpdir: &TempDir)
391 let out_filename = tmpdir.path().join(METADATA_FILENAME);
392 let result = fs::write(&out_filename, &trans.metadata.raw_data);
394 if let Err(e) = result {
395 sess.fatal(&format!("failed to write {}: {}", out_filename.display(), e));
408 // An rlib in its current incarnation is essentially a renamed .a file. The
409 // rlib primarily contains the object file of the crate, but it also contains
410 // all of the object files from native libraries. This is done by unzipping
411 // native libraries and inserting all of the contents into this archive.
412 fn link_rlib<'a>(sess: &'a Session,
413 trans: &CrateTranslation,
416 tmpdir: &TempDir) -> ArchiveBuilder<'a> {
417 info!("preparing rlib to {:?}", out_filename);
418 let mut ab = ArchiveBuilder::new(archive_config(sess, out_filename, None));
420 for obj in trans.modules.iter().filter_map(|m| m.object.as_ref()) {
424 // Note that in this loop we are ignoring the value of `lib.cfg`. That is,
425 // we may not be configured to actually include a static library if we're
426 // adding it here. That's because later when we consume this rlib we'll
427 // decide whether we actually needed the static library or not.
429 // To do this "correctly" we'd need to keep track of which libraries added
430 // which object files to the archive. We don't do that here, however. The
431 // #[link(cfg(..))] feature is unstable, though, and only intended to get
432 // liblibc working. In that sense the check below just indicates that if
433 // there are any libraries we want to omit object files for at link time we
434 // just exclude all custom object files.
436 // Eventually if we want to stabilize or flesh out the #[link(cfg(..))]
437 // feature then we'll need to figure out how to record what objects were
438 // loaded from the libraries found here and then encode that into the
439 // metadata of the rlib we're generating somehow.
440 for lib in trans.crate_info.used_libraries.iter() {
442 NativeLibraryKind::NativeStatic => {}
443 NativeLibraryKind::NativeStaticNobundle |
444 NativeLibraryKind::NativeFramework |
445 NativeLibraryKind::NativeUnknown => continue,
447 ab.add_native_library(&lib.name.as_str());
450 // After adding all files to the archive, we need to update the
451 // symbol table of the archive.
454 // Note that it is important that we add all of our non-object "magical
455 // files" *after* all of the object files in the archive. The reason for
456 // this is as follows:
458 // * When performing LTO, this archive will be modified to remove
459 // objects from above. The reason for this is described below.
461 // * When the system linker looks at an archive, it will attempt to
462 // determine the architecture of the archive in order to see whether its
465 // The algorithm for this detection is: iterate over the files in the
466 // archive. Skip magical SYMDEF names. Interpret the first file as an
467 // object file. Read architecture from the object file.
469 // * As one can probably see, if "metadata" and "foo.bc" were placed
470 // before all of the objects, then the architecture of this archive would
471 // not be correctly inferred once 'foo.o' is removed.
473 // Basically, all this means is that this code should not move above the
476 RlibFlavor::Normal => {
477 // Instead of putting the metadata in an object file section, rlibs
478 // contain the metadata in a separate file.
479 ab.add_file(&emit_metadata(sess, trans, tmpdir));
481 // For LTO purposes, the bytecode of this library is also inserted
483 for bytecode in trans.modules.iter().filter_map(|m| m.bytecode_compressed.as_ref()) {
484 ab.add_file(bytecode);
487 // After adding all files to the archive, we need to update the
488 // symbol table of the archive. This currently dies on macOS (see
489 // #11162), and isn't necessary there anyway
490 if !sess.target.target.options.is_like_osx {
495 RlibFlavor::StaticlibBase => {
496 let obj = trans.allocator_module
498 .and_then(|m| m.object.as_ref());
499 if let Some(obj) = obj {
508 // Create a static archive
510 // This is essentially the same thing as an rlib, but it also involves adding
511 // all of the upstream crates' objects into the archive. This will slurp in
512 // all of the native libraries of upstream dependencies as well.
514 // Additionally, there's no way for us to link dynamic libraries, so we warn
515 // about all dynamic library dependencies that they're not linked in.
517 // There's no need to include metadata in a static archive, so ensure to not
518 // link in the metadata object file (and also don't prepare the archive with a
520 fn link_staticlib(sess: &Session,
521 trans: &CrateTranslation,
524 let mut ab = link_rlib(sess,
526 RlibFlavor::StaticlibBase,
529 let mut all_native_libs = vec![];
531 let res = each_linked_rlib(sess, &trans.crate_info, &mut |cnum, path| {
532 let name = &trans.crate_info.crate_name[&cnum];
533 let native_libs = &trans.crate_info.native_libraries[&cnum];
535 // Here when we include the rlib into our staticlib we need to make a
536 // decision whether to include the extra object files along the way.
537 // These extra object files come from statically included native
538 // libraries, but they may be cfg'd away with #[link(cfg(..))].
540 // This unstable feature, though, only needs liblibc to work. The only
541 // use case there is where musl is statically included in liblibc.rlib,
542 // so if we don't want the included version we just need to skip it. As
543 // a result the logic here is that if *any* linked library is cfg'd away
544 // we just skip all object files.
546 // Clearly this is not sufficient for a general purpose feature, and
547 // we'd want to read from the library's metadata to determine which
548 // object files come from where and selectively skip them.
549 let skip_object_files = native_libs.iter().any(|lib| {
550 lib.kind == NativeLibraryKind::NativeStatic && !relevant_lib(sess, lib)
554 is_full_lto_enabled(sess) &&
555 !ignored_for_lto(sess, &trans.crate_info, cnum),
556 skip_object_files).unwrap();
558 all_native_libs.extend(trans.crate_info.native_libraries[&cnum].iter().cloned());
560 if let Err(e) = res {
567 if !all_native_libs.is_empty() {
568 if sess.opts.prints.contains(&PrintRequest::NativeStaticLibs) {
569 print_native_static_libs(sess, &all_native_libs);
574 fn print_native_static_libs(sess: &Session, all_native_libs: &[NativeLibrary]) {
575 let lib_args: Vec<_> = all_native_libs.iter()
576 .filter(|l| relevant_lib(sess, l))
577 .filter_map(|lib| match lib.kind {
578 NativeLibraryKind::NativeStaticNobundle |
579 NativeLibraryKind::NativeUnknown => {
580 if sess.target.target.options.is_like_msvc {
581 Some(format!("{}.lib", lib.name))
583 Some(format!("-l{}", lib.name))
586 NativeLibraryKind::NativeFramework => {
587 // ld-only syntax, since there are no frameworks in MSVC
588 Some(format!("-framework {}", lib.name))
590 // These are included, no need to print them
591 NativeLibraryKind::NativeStatic => None,
594 if !lib_args.is_empty() {
595 sess.note_without_error("Link against the following native artifacts when linking \
596 against this static library. The order and any duplication \
597 can be significant on some platforms.");
598 // Prefix for greppability
599 sess.note_without_error(&format!("native-static-libs: {}", &lib_args.join(" ")));
603 // Create a dynamic library or executable
605 // This will invoke the system linker/cc to create the resulting file. This
606 // links to all upstream files as well.
607 fn link_natively(sess: &Session,
608 crate_type: config::CrateType,
610 trans: &CrateTranslation,
612 info!("preparing {:?} to {:?}", crate_type, out_filename);
613 let flavor = sess.linker_flavor();
615 // The invocations of cc share some flags across platforms
616 let (pname, mut cmd) = get_linker(sess);
618 let root = sess.target_filesearch(PathKind::Native).get_lib_path();
619 if let Some(args) = sess.target.target.options.pre_link_args.get(&flavor) {
622 if let Some(ref args) = sess.opts.debugging_opts.pre_link_args {
625 cmd.args(&sess.opts.debugging_opts.pre_link_arg);
627 let pre_link_objects = if crate_type == config::CrateTypeExecutable {
628 &sess.target.target.options.pre_link_objects_exe
630 &sess.target.target.options.pre_link_objects_dll
632 for obj in pre_link_objects {
633 cmd.arg(root.join(obj));
636 if sess.target.target.options.is_like_emscripten {
638 cmd.arg(if sess.panic_strategy() == PanicStrategy::Abort {
639 "DISABLE_EXCEPTION_CATCHING=1"
641 "DISABLE_EXCEPTION_CATCHING=0"
646 let mut linker = trans.linker_info.to_linker(cmd, &sess);
647 link_args(&mut *linker, sess, crate_type, tmpdir,
648 out_filename, trans);
649 cmd = linker.finalize();
651 if let Some(args) = sess.target.target.options.late_link_args.get(&flavor) {
654 for obj in &sess.target.target.options.post_link_objects {
655 cmd.arg(root.join(obj));
657 if let Some(args) = sess.target.target.options.post_link_args.get(&flavor) {
660 for &(ref k, ref v) in &sess.target.target.options.link_env {
664 if sess.opts.debugging_opts.print_link_args {
665 println!("{:?}", &cmd);
668 // May have not found libraries in the right formats.
669 sess.abort_if_errors();
671 // Invoke the system linker
673 // Note that there's a terribly awful hack that really shouldn't be present
674 // in any compiler. Here an environment variable is supported to
675 // automatically retry the linker invocation if the linker looks like it
678 // Gee that seems odd, normally segfaults are things we want to know about!
679 // Unfortunately though in rust-lang/rust#38878 we're experiencing the
680 // linker segfaulting on Travis quite a bit which is causing quite a bit of
681 // pain to land PRs when they spuriously fail due to a segfault.
683 // The issue #38878 has some more debugging information on it as well, but
684 // this unfortunately looks like it's just a race condition in macOS's linker
685 // with some thread pool working in the background. It seems that no one
686 // currently knows a fix for this so in the meantime we're left with this...
688 let retry_on_segfault = env::var("RUSTC_RETRY_LINKER_ON_SEGFAULT").is_ok();
693 prog = time(sess.time_passes(), "running linker", || {
694 exec_linker(sess, &mut cmd, tmpdir)
696 let output = match prog {
697 Ok(ref output) => output,
700 if output.status.success() {
703 let mut out = output.stderr.clone();
704 out.extend(&output.stdout);
705 let out = String::from_utf8_lossy(&out);
707 // Check to see if the link failed with "unrecognized command line option:
708 // '-no-pie'" for gcc or "unknown argument: '-no-pie'" for clang. If so,
709 // reperform the link step without the -no-pie option. This is safe because
710 // if the linker doesn't support -no-pie then it should not default to
711 // linking executables as pie. Different versions of gcc seem to use
712 // different quotes in the error message so don't check for them.
713 if sess.target.target.options.linker_is_gnu &&
714 (out.contains("unrecognized command line option") ||
715 out.contains("unknown argument")) &&
716 out.contains("-no-pie") &&
717 cmd.get_args().iter().any(|e| e.to_string_lossy() == "-no-pie") {
718 info!("linker output: {:?}", out);
719 warn!("Linker does not support -no-pie command line option. Retrying without.");
720 for arg in cmd.take_args() {
721 if arg.to_string_lossy() != "-no-pie" {
728 if !retry_on_segfault || i > 3 {
731 let msg_segv = "clang: error: unable to execute command: Segmentation fault: 11";
732 let msg_bus = "clang: error: unable to execute command: Bus error: 10";
733 if !(out.contains(msg_segv) || out.contains(msg_bus)) {
738 "looks like the linker segfaulted when we tried to call it, \
739 automatically retrying again. cmd = {:?}, out = {}.",
747 fn escape_string(s: &[u8]) -> String {
748 str::from_utf8(s).map(|s| s.to_owned())
749 .unwrap_or_else(|_| {
750 let mut x = "Non-UTF-8 output: ".to_string();
752 .flat_map(|&b| ascii::escape_default(b))
753 .map(|b| char::from_u32(b as u32).unwrap()));
757 if !prog.status.success() {
758 let mut output = prog.stderr.clone();
759 output.extend_from_slice(&prog.stdout);
760 sess.struct_err(&format!("linking with `{}` failed: {}",
763 .note(&format!("{:?}", &cmd))
764 .note(&escape_string(&output))
766 sess.abort_if_errors();
768 info!("linker stderr:\n{}", escape_string(&prog.stderr));
769 info!("linker stdout:\n{}", escape_string(&prog.stdout));
772 let linker_not_found = e.kind() == io::ErrorKind::NotFound;
774 let mut linker_error = {
775 if linker_not_found {
776 sess.struct_err(&format!("linker `{}` not found", pname.display()))
778 sess.struct_err(&format!("could not exec the linker `{}`", pname.display()))
782 linker_error.note(&format!("{}", e));
784 if !linker_not_found {
785 linker_error.note(&format!("{:?}", &cmd));
790 if sess.target.target.options.is_like_msvc && linker_not_found {
791 sess.note_without_error("the msvc targets depend on the msvc linker \
792 but `link.exe` was not found");
793 sess.note_without_error("please ensure that VS 2013 or VS 2015 was installed \
794 with the Visual C++ option");
796 sess.abort_if_errors();
801 // On macOS, debuggers need this utility to get run to do some munging of
802 // the symbols. Note, though, that if the object files are being preserved
803 // for their debug information there's no need for us to run dsymutil.
804 if sess.target.target.options.is_like_osx &&
805 sess.opts.debuginfo != NoDebugInfo &&
806 !preserve_objects_for_their_debuginfo(sess)
808 match Command::new("dsymutil").arg(out_filename).output() {
810 Err(e) => sess.fatal(&format!("failed to run dsymutil: {}", e)),
815 fn exec_linker(sess: &Session, cmd: &mut Command, tmpdir: &Path)
816 -> io::Result<Output>
818 // When attempting to spawn the linker we run a risk of blowing out the
819 // size limits for spawning a new process with respect to the arguments
820 // we pass on the command line.
822 // Here we attempt to handle errors from the OS saying "your list of
823 // arguments is too big" by reinvoking the linker again with an `@`-file
824 // that contains all the arguments. The theory is that this is then
825 // accepted on all linkers and the linker will read all its options out of
826 // there instead of looking at the command line.
827 if !cmd.very_likely_to_exceed_some_spawn_limit() {
828 match cmd.command().stdout(Stdio::piped()).stderr(Stdio::piped()).spawn() {
829 Ok(child) => return child.wait_with_output(),
830 Err(ref e) if command_line_too_big(e) => {}
831 Err(e) => return Err(e)
835 let mut cmd2 = cmd.clone();
836 let mut args = String::new();
837 for arg in cmd2.take_args() {
838 args.push_str(&Escape {
839 arg: arg.to_str().unwrap(),
840 is_like_msvc: sess.target.target.options.is_like_msvc,
844 let file = tmpdir.join("linker-arguments");
845 let bytes = if sess.target.target.options.is_like_msvc {
846 let mut out = vec![];
847 // start the stream with a UTF-16 BOM
848 for c in vec![0xFEFF].into_iter().chain(args.encode_utf16()) {
849 // encode in little endian
851 out.push((c >> 8) as u8);
857 fs::write(&file, &bytes)?;
858 cmd2.arg(format!("@{}", file.display()));
859 return cmd2.output();
862 fn command_line_too_big(err: &io::Error) -> bool {
863 err.raw_os_error() == Some(::libc::E2BIG)
867 fn command_line_too_big(err: &io::Error) -> bool {
868 const ERROR_FILENAME_EXCED_RANGE: i32 = 206;
869 err.raw_os_error() == Some(ERROR_FILENAME_EXCED_RANGE)
877 impl<'a> fmt::Display for Escape<'a> {
878 fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
879 if self.is_like_msvc {
880 // This is "documented" at
881 // https://msdn.microsoft.com/en-us/library/4xdcbak7.aspx
883 // Unfortunately there's not a great specification of the
884 // syntax I could find online (at least) but some local
885 // testing showed that this seemed sufficient-ish to catch
886 // at least a few edge cases.
888 for c in self.arg.chars() {
890 '"' => write!(f, "\\{}", c)?,
891 c => write!(f, "{}", c)?,
896 // This is documented at https://linux.die.net/man/1/ld, namely:
898 // > Options in file are separated by whitespace. A whitespace
899 // > character may be included in an option by surrounding the
900 // > entire option in either single or double quotes. Any
901 // > character (including a backslash) may be included by
902 // > prefixing the character to be included with a backslash.
904 // We put an argument on each line, so all we need to do is
905 // ensure the line is interpreted as one whole argument.
906 for c in self.arg.chars() {
909 ' ' => write!(f, "\\{}", c)?,
910 c => write!(f, "{}", c)?,
919 fn link_args(cmd: &mut Linker,
921 crate_type: config::CrateType,
924 trans: &CrateTranslation) {
926 // The default library location, we need this to find the runtime.
927 // The location of crates will be determined as needed.
928 let lib_path = sess.target_filesearch(PathKind::All).get_lib_path();
931 let t = &sess.target.target;
933 cmd.include_path(&fix_windows_verbatim_for_gcc(&lib_path));
934 for obj in trans.modules.iter().filter_map(|m| m.object.as_ref()) {
937 cmd.output_filename(out_filename);
939 if crate_type == config::CrateTypeExecutable &&
940 sess.target.target.options.is_like_windows {
941 if let Some(ref s) = trans.windows_subsystem {
946 // If we're building a dynamic library then some platforms need to make sure
947 // that all symbols are exported correctly from the dynamic library.
948 if crate_type != config::CrateTypeExecutable ||
949 sess.target.target.options.is_like_emscripten {
950 cmd.export_symbols(tmpdir, crate_type);
953 // When linking a dynamic library, we put the metadata into a section of the
954 // executable. This metadata is in a separate object file from the main
955 // object file, so we link that in here.
956 if crate_type == config::CrateTypeDylib ||
957 crate_type == config::CrateTypeProcMacro {
958 if let Some(obj) = trans.metadata_module.object.as_ref() {
963 let obj = trans.allocator_module
965 .and_then(|m| m.object.as_ref());
966 if let Some(obj) = obj {
970 // Try to strip as much out of the generated object by removing unused
971 // sections if possible. See more comments in linker.rs
972 if !sess.opts.cg.link_dead_code {
973 let keep_metadata = crate_type == config::CrateTypeDylib;
974 cmd.gc_sections(keep_metadata);
977 let used_link_args = &trans.crate_info.link_args;
979 if crate_type == config::CrateTypeExecutable {
980 let mut position_independent_executable = false;
982 if t.options.position_independent_executables {
983 let empty_vec = Vec::new();
984 let args = sess.opts.cg.link_args.as_ref().unwrap_or(&empty_vec);
985 let more_args = &sess.opts.cg.link_arg;
986 let mut args = args.iter().chain(more_args.iter()).chain(used_link_args.iter());
988 if get_reloc_model(sess) == llvm::RelocMode::PIC
989 && !sess.crt_static() && !args.any(|x| *x == "-static") {
990 position_independent_executable = true;
994 if position_independent_executable {
995 cmd.position_independent_executable();
997 // recent versions of gcc can be configured to generate position
998 // independent executables by default. We have to pass -no-pie to
999 // explicitly turn that off.
1000 if sess.target.target.options.linker_is_gnu {
1001 cmd.no_position_independent_executable();
1006 let relro_level = match sess.opts.debugging_opts.relro_level {
1007 Some(level) => level,
1008 None => t.options.relro_level,
1011 RelroLevel::Full => {
1014 RelroLevel::Partial => {
1015 cmd.partial_relro();
1017 RelroLevel::Off => {},
1020 // Pass optimization flags down to the linker.
1023 // Pass debuginfo flags down to the linker.
1026 // We want to prevent the compiler from accidentally leaking in any system
1027 // libraries, so we explicitly ask gcc to not link to any libraries by
1028 // default. Note that this does not happen for windows because windows pulls
1029 // in some large number of libraries and I couldn't quite figure out which
1030 // subset we wanted.
1031 if t.options.no_default_libraries {
1032 cmd.no_default_libraries();
1035 // Take careful note of the ordering of the arguments we pass to the linker
1036 // here. Linkers will assume that things on the left depend on things to the
1037 // right. Things on the right cannot depend on things on the left. This is
1038 // all formally implemented in terms of resolving symbols (libs on the right
1039 // resolve unknown symbols of libs on the left, but not vice versa).
1041 // For this reason, we have organized the arguments we pass to the linker as
1044 // 1. The local object that LLVM just generated
1045 // 2. Local native libraries
1046 // 3. Upstream rust libraries
1047 // 4. Upstream native libraries
1049 // The rationale behind this ordering is that those items lower down in the
1050 // list can't depend on items higher up in the list. For example nothing can
1051 // depend on what we just generated (e.g. that'd be a circular dependency).
1052 // Upstream rust libraries are not allowed to depend on our local native
1053 // libraries as that would violate the structure of the DAG, in that
1054 // scenario they are required to link to them as well in a shared fashion.
1056 // Note that upstream rust libraries may contain native dependencies as
1057 // well, but they also can't depend on what we just started to add to the
1058 // link line. And finally upstream native libraries can't depend on anything
1059 // in this DAG so far because they're only dylibs and dylibs can only depend
1060 // on other dylibs (e.g. other native deps).
1061 add_local_native_libraries(cmd, sess, trans);
1062 add_upstream_rust_crates(cmd, sess, trans, crate_type, tmpdir);
1063 add_upstream_native_libraries(cmd, sess, trans, crate_type);
1065 // Tell the linker what we're doing.
1066 if crate_type != config::CrateTypeExecutable {
1067 cmd.build_dylib(out_filename);
1069 if crate_type == config::CrateTypeExecutable && sess.crt_static() {
1070 cmd.build_static_executable();
1073 // FIXME (#2397): At some point we want to rpath our guesses as to
1074 // where extern libraries might live, based on the
1075 // addl_lib_search_paths
1076 if sess.opts.cg.rpath {
1077 let sysroot = sess.sysroot();
1078 let target_triple = &sess.opts.target_triple;
1079 let mut get_install_prefix_lib_path = || {
1080 let install_prefix = option_env!("CFG_PREFIX").expect("CFG_PREFIX");
1081 let tlib = filesearch::relative_target_lib_path(sysroot, target_triple);
1082 let mut path = PathBuf::from(install_prefix);
1087 let mut rpath_config = RPathConfig {
1088 used_crates: &trans.crate_info.used_crates_dynamic,
1089 out_filename: out_filename.to_path_buf(),
1090 has_rpath: sess.target.target.options.has_rpath,
1091 is_like_osx: sess.target.target.options.is_like_osx,
1092 linker_is_gnu: sess.target.target.options.linker_is_gnu,
1093 get_install_prefix_lib_path: &mut get_install_prefix_lib_path,
1095 cmd.args(&rpath::get_rpath_flags(&mut rpath_config));
1098 // Finally add all the linker arguments provided on the command line along
1099 // with any #[link_args] attributes found inside the crate
1100 if let Some(ref args) = sess.opts.cg.link_args {
1103 cmd.args(&sess.opts.cg.link_arg);
1104 cmd.args(&used_link_args);
1107 // # Native library linking
1109 // User-supplied library search paths (-L on the command line). These are
1110 // the same paths used to find Rust crates, so some of them may have been
1111 // added already by the previous crate linking code. This only allows them
1112 // to be found at compile time so it is still entirely up to outside
1113 // forces to make sure that library can be found at runtime.
1115 // Also note that the native libraries linked here are only the ones located
1116 // in the current crate. Upstream crates with native library dependencies
1117 // may have their native library pulled in above.
1118 fn add_local_native_libraries(cmd: &mut Linker,
1120 trans: &CrateTranslation) {
1121 sess.target_filesearch(PathKind::All).for_each_lib_search_path(|path, k| {
1123 PathKind::Framework => { cmd.framework_path(path); }
1124 _ => { cmd.include_path(&fix_windows_verbatim_for_gcc(path)); }
1128 let relevant_libs = trans.crate_info.used_libraries.iter().filter(|l| {
1129 relevant_lib(sess, l)
1132 let search_path = archive_search_paths(sess);
1133 for lib in relevant_libs {
1135 NativeLibraryKind::NativeUnknown => cmd.link_dylib(&lib.name.as_str()),
1136 NativeLibraryKind::NativeFramework => cmd.link_framework(&lib.name.as_str()),
1137 NativeLibraryKind::NativeStaticNobundle => cmd.link_staticlib(&lib.name.as_str()),
1138 NativeLibraryKind::NativeStatic => cmd.link_whole_staticlib(&lib.name.as_str(),
1144 // # Rust Crate linking
1146 // Rust crates are not considered at all when creating an rlib output. All
1147 // dependencies will be linked when producing the final output (instead of
1148 // the intermediate rlib version)
1149 fn add_upstream_rust_crates(cmd: &mut Linker,
1151 trans: &CrateTranslation,
1152 crate_type: config::CrateType,
1154 // All of the heavy lifting has previously been accomplished by the
1155 // dependency_format module of the compiler. This is just crawling the
1156 // output of that module, adding crates as necessary.
1158 // Linking to a rlib involves just passing it to the linker (the linker
1159 // will slurp up the object files inside), and linking to a dynamic library
1160 // involves just passing the right -l flag.
1162 let formats = sess.dependency_formats.borrow();
1163 let data = formats.get(&crate_type).unwrap();
1165 // Invoke get_used_crates to ensure that we get a topological sorting of
1167 let deps = &trans.crate_info.used_crates_dynamic;
1169 let mut compiler_builtins = None;
1171 for &(cnum, _) in deps.iter() {
1172 // We may not pass all crates through to the linker. Some crates may
1173 // appear statically in an existing dylib, meaning we'll pick up all the
1174 // symbols from the dylib.
1175 let src = &trans.crate_info.used_crate_source[&cnum];
1176 match data[cnum.as_usize() - 1] {
1177 _ if trans.crate_info.profiler_runtime == Some(cnum) => {
1178 add_static_crate(cmd, sess, trans, tmpdir, crate_type, cnum);
1180 _ if trans.crate_info.sanitizer_runtime == Some(cnum) => {
1181 link_sanitizer_runtime(cmd, sess, trans, tmpdir, cnum);
1183 // compiler-builtins are always placed last to ensure that they're
1184 // linked correctly.
1185 _ if trans.crate_info.compiler_builtins == Some(cnum) => {
1186 assert!(compiler_builtins.is_none());
1187 compiler_builtins = Some(cnum);
1189 Linkage::NotLinked |
1190 Linkage::IncludedFromDylib => {}
1191 Linkage::Static => {
1192 add_static_crate(cmd, sess, trans, tmpdir, crate_type, cnum);
1194 Linkage::Dynamic => {
1195 add_dynamic_crate(cmd, sess, &src.dylib.as_ref().unwrap().0)
1200 // compiler-builtins are always placed last to ensure that they're
1201 // linked correctly.
1202 // We must always link the `compiler_builtins` crate statically. Even if it
1203 // was already "included" in a dylib (e.g. `libstd` when `-C prefer-dynamic`
1205 if let Some(cnum) = compiler_builtins {
1206 add_static_crate(cmd, sess, trans, tmpdir, crate_type, cnum);
1209 // Converts a library file-stem into a cc -l argument
1210 fn unlib<'a>(config: &config::Config, stem: &'a str) -> &'a str {
1211 if stem.starts_with("lib") && !config.target.options.is_like_windows {
1218 // We must link the sanitizer runtime using -Wl,--whole-archive but since
1219 // it's packed in a .rlib, it contains stuff that are not objects that will
1220 // make the linker error. So we must remove those bits from the .rlib before
1222 fn link_sanitizer_runtime(cmd: &mut Linker,
1224 trans: &CrateTranslation,
1227 let src = &trans.crate_info.used_crate_source[&cnum];
1228 let cratepath = &src.rlib.as_ref().unwrap().0;
1230 if sess.target.target.options.is_like_osx {
1231 // On Apple platforms, the sanitizer is always built as a dylib, and
1232 // LLVM will link to `@rpath/*.dylib`, so we need to specify an
1233 // rpath to the library as well (the rpath should be absolute, see
1234 // PR #41352 for details).
1236 // FIXME: Remove this logic into librustc_*san once Cargo supports it
1237 let rpath = cratepath.parent().unwrap();
1238 let rpath = rpath.to_str().expect("non-utf8 component in path");
1239 cmd.args(&["-Wl,-rpath".into(), "-Xlinker".into(), rpath.into()]);
1242 let dst = tmpdir.join(cratepath.file_name().unwrap());
1243 let cfg = archive_config(sess, &dst, Some(cratepath));
1244 let mut archive = ArchiveBuilder::new(cfg);
1245 archive.update_symbols();
1247 for f in archive.src_files() {
1248 if f.ends_with(RLIB_BYTECODE_EXTENSION) || f == METADATA_FILENAME {
1249 archive.remove_file(&f);
1256 cmd.link_whole_rlib(&dst);
1259 // Adds the static "rlib" versions of all crates to the command line.
1260 // There's a bit of magic which happens here specifically related to LTO and
1261 // dynamic libraries. Specifically:
1263 // * For LTO, we remove upstream object files.
1264 // * For dylibs we remove metadata and bytecode from upstream rlibs
1266 // When performing LTO, almost(*) all of the bytecode from the upstream
1267 // libraries has already been included in our object file output. As a
1268 // result we need to remove the object files in the upstream libraries so
1269 // the linker doesn't try to include them twice (or whine about duplicate
1270 // symbols). We must continue to include the rest of the rlib, however, as
1271 // it may contain static native libraries which must be linked in.
1273 // (*) Crates marked with `#![no_builtins]` don't participate in LTO and
1274 // their bytecode wasn't included. The object files in those libraries must
1275 // still be passed to the linker.
1277 // When making a dynamic library, linkers by default don't include any
1278 // object files in an archive if they're not necessary to resolve the link.
1279 // We basically want to convert the archive (rlib) to a dylib, though, so we
1280 // *do* want everything included in the output, regardless of whether the
1281 // linker thinks it's needed or not. As a result we must use the
1282 // --whole-archive option (or the platform equivalent). When using this
1283 // option the linker will fail if there are non-objects in the archive (such
1284 // as our own metadata and/or bytecode). All in all, for rlibs to be
1285 // entirely included in dylibs, we need to remove all non-object files.
1287 // Note, however, that if we're not doing LTO or we're not producing a dylib
1288 // (aka we're making an executable), we can just pass the rlib blindly to
1289 // the linker (fast) because it's fine if it's not actually included as
1290 // we're at the end of the dependency chain.
1291 fn add_static_crate(cmd: &mut Linker,
1293 trans: &CrateTranslation,
1295 crate_type: config::CrateType,
1297 let src = &trans.crate_info.used_crate_source[&cnum];
1298 let cratepath = &src.rlib.as_ref().unwrap().0;
1300 // See the comment above in `link_staticlib` and `link_rlib` for why if
1301 // there's a static library that's not relevant we skip all object
1303 let native_libs = &trans.crate_info.native_libraries[&cnum];
1304 let skip_native = native_libs.iter().any(|lib| {
1305 lib.kind == NativeLibraryKind::NativeStatic && !relevant_lib(sess, lib)
1308 if (!is_full_lto_enabled(sess) ||
1309 ignored_for_lto(sess, &trans.crate_info, cnum)) &&
1310 crate_type != config::CrateTypeDylib &&
1312 cmd.link_rlib(&fix_windows_verbatim_for_gcc(cratepath));
1316 let dst = tmpdir.join(cratepath.file_name().unwrap());
1317 let name = cratepath.file_name().unwrap().to_str().unwrap();
1318 let name = &name[3..name.len() - 5]; // chop off lib/.rlib
1320 time(sess.time_passes(), &format!("altering {}.rlib", name), || {
1321 let cfg = archive_config(sess, &dst, Some(cratepath));
1322 let mut archive = ArchiveBuilder::new(cfg);
1323 archive.update_symbols();
1325 let mut any_objects = false;
1326 for f in archive.src_files() {
1327 if f.ends_with(RLIB_BYTECODE_EXTENSION) || f == METADATA_FILENAME {
1328 archive.remove_file(&f);
1332 let canonical = f.replace("-", "_");
1333 let canonical_name = name.replace("-", "_");
1335 // Look for `.rcgu.o` at the end of the filename to conclude
1336 // that this is a Rust-related object file.
1337 fn looks_like_rust(s: &str) -> bool {
1338 let path = Path::new(s);
1339 let ext = path.extension().and_then(|s| s.to_str());
1340 if ext != Some(OutputType::Object.extension()) {
1343 let ext2 = path.file_stem()
1344 .and_then(|s| Path::new(s).extension())
1345 .and_then(|s| s.to_str());
1346 ext2 == Some(RUST_CGU_EXT)
1349 let is_rust_object =
1350 canonical.starts_with(&canonical_name) &&
1351 looks_like_rust(&f);
1353 // If we've been requested to skip all native object files
1354 // (those not generated by the rust compiler) then we can skip
1355 // this file. See above for why we may want to do this.
1356 let skip_because_cfg_say_so = skip_native && !is_rust_object;
1358 // If we're performing LTO and this is a rust-generated object
1359 // file, then we don't need the object file as it's part of the
1360 // LTO module. Note that `#![no_builtins]` is excluded from LTO,
1361 // though, so we let that object file slide.
1362 let skip_because_lto = is_full_lto_enabled(sess) &&
1364 (sess.target.target.options.no_builtins ||
1365 !trans.crate_info.is_no_builtins.contains(&cnum));
1367 if skip_because_cfg_say_so || skip_because_lto {
1368 archive.remove_file(&f);
1379 // If we're creating a dylib, then we need to include the
1380 // whole of each object in our archive into that artifact. This is
1381 // because a `dylib` can be reused as an intermediate artifact.
1383 // Note, though, that we don't want to include the whole of a
1384 // compiler-builtins crate (e.g. compiler-rt) because it'll get
1385 // repeatedly linked anyway.
1386 if crate_type == config::CrateTypeDylib &&
1387 trans.crate_info.compiler_builtins != Some(cnum) {
1388 cmd.link_whole_rlib(&fix_windows_verbatim_for_gcc(&dst));
1390 cmd.link_rlib(&fix_windows_verbatim_for_gcc(&dst));
1395 // Same thing as above, but for dynamic crates instead of static crates.
1396 fn add_dynamic_crate(cmd: &mut Linker, sess: &Session, cratepath: &Path) {
1397 // If we're performing LTO, then it should have been previously required
1398 // that all upstream rust dependencies were available in an rlib format.
1399 assert!(!is_full_lto_enabled(sess));
1401 // Just need to tell the linker about where the library lives and
1403 let parent = cratepath.parent();
1404 if let Some(dir) = parent {
1405 cmd.include_path(&fix_windows_verbatim_for_gcc(dir));
1407 let filestem = cratepath.file_stem().unwrap().to_str().unwrap();
1408 cmd.link_rust_dylib(&unlib(&sess.target, filestem),
1409 parent.unwrap_or(Path::new("")));
1413 // Link in all of our upstream crates' native dependencies. Remember that
1414 // all of these upstream native dependencies are all non-static
1415 // dependencies. We've got two cases then:
1417 // 1. The upstream crate is an rlib. In this case we *must* link in the
1418 // native dependency because the rlib is just an archive.
1420 // 2. The upstream crate is a dylib. In order to use the dylib, we have to
1421 // have the dependency present on the system somewhere. Thus, we don't
1422 // gain a whole lot from not linking in the dynamic dependency to this
1425 // The use case for this is a little subtle. In theory the native
1426 // dependencies of a crate are purely an implementation detail of the crate
1427 // itself, but the problem arises with generic and inlined functions. If a
1428 // generic function calls a native function, then the generic function must
1429 // be instantiated in the target crate, meaning that the native symbol must
1430 // also be resolved in the target crate.
1431 fn add_upstream_native_libraries(cmd: &mut Linker,
1433 trans: &CrateTranslation,
1434 crate_type: config::CrateType) {
1435 // Be sure to use a topological sorting of crates because there may be
1436 // interdependencies between native libraries. When passing -nodefaultlibs,
1437 // for example, almost all native libraries depend on libc, so we have to
1438 // make sure that's all the way at the right (liblibc is near the base of
1439 // the dependency chain).
1441 // This passes RequireStatic, but the actual requirement doesn't matter,
1442 // we're just getting an ordering of crate numbers, we're not worried about
1444 let formats = sess.dependency_formats.borrow();
1445 let data = formats.get(&crate_type).unwrap();
1447 let crates = &trans.crate_info.used_crates_static;
1448 for &(cnum, _) in crates {
1449 for lib in trans.crate_info.native_libraries[&cnum].iter() {
1450 if !relevant_lib(sess, &lib) {
1454 NativeLibraryKind::NativeUnknown => cmd.link_dylib(&lib.name.as_str()),
1455 NativeLibraryKind::NativeFramework => cmd.link_framework(&lib.name.as_str()),
1456 NativeLibraryKind::NativeStaticNobundle => {
1457 // Link "static-nobundle" native libs only if the crate they originate from
1458 // is being linked statically to the current crate. If it's linked dynamically
1459 // or is an rlib already included via some other dylib crate, the symbols from
1460 // native libs will have already been included in that dylib.
1461 if data[cnum.as_usize() - 1] == Linkage::Static {
1462 cmd.link_staticlib(&lib.name.as_str())
1465 // ignore statically included native libraries here as we've
1466 // already included them when we included the rust library
1468 NativeLibraryKind::NativeStatic => {}
1474 fn relevant_lib(sess: &Session, lib: &NativeLibrary) -> bool {
1476 Some(ref cfg) => attr::cfg_matches(cfg, &sess.parse_sess, None),
1481 fn is_full_lto_enabled(sess: &Session) -> bool {
1487 Lto::ThinLocal => false,