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.
12 use cc::windows_registry;
13 use super::archive::{ArchiveBuilder, ArchiveConfig};
14 use super::bytecode::RLIB_BYTECODE_EXTENSION;
15 use super::linker::Linker;
16 use super::command::Command;
17 use super::rpath::RPathConfig;
19 use metadata::METADATA_FILENAME;
20 use rustc::session::config::{self, DebugInfo, 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 {CodegenResults, CrateInfo};
28 use rustc::util::common::time;
29 use rustc::util::fs::fix_windows_verbatim_for_gcc;
30 use rustc::hir::def_id::CrateNum;
31 use tempfile::{Builder as TempFileBuilder, TempDir};
32 use rustc_target::spec::{PanicStrategy, RelroLevel, LinkerFlavor};
33 use rustc_data_structures::fx::FxHashSet;
34 use context::get_reloc_model;
44 use std::path::{Path, PathBuf};
45 use std::process::{Output, Stdio};
49 /// The LLVM module name containing crate-metadata. This includes a `.` on
50 /// purpose, so it cannot clash with the name of a user-defined module.
51 pub const METADATA_MODULE_NAME: &'static str = "crate.metadata";
53 // same as for metadata above, but for allocator shim
54 pub const ALLOCATOR_MODULE_NAME: &'static str = "crate.allocator";
56 pub use rustc_codegen_utils::link::{find_crate_name, filename_for_input, default_output_for_target,
57 invalid_output_for_target, build_link_meta, out_filename,
58 check_file_is_writeable};
60 // The third parameter is for env vars, used on windows to set up the
61 // path for MSVC to find its DLLs, and gcc to find its bundled
63 pub fn get_linker(sess: &Session, linker: &Path, flavor: LinkerFlavor) -> (PathBuf, Command) {
64 // If our linker looks like a batch script on Windows then to execute this
65 // we'll need to spawn `cmd` explicitly. This is primarily done to handle
66 // emscripten where the linker is `emcc.bat` and needs to be spawned as
67 // `cmd /c emcc.bat ...`.
69 // This worked historically but is needed manually since #42436 (regression
70 // was tagged as #42791) and some more info can be found on #44443 for
72 let mut cmd = match linker.to_str() {
73 Some(linker) if cfg!(windows) && linker.ends_with(".bat") => Command::bat_script(linker),
75 LinkerFlavor::Lld(f) => Command::lld(linker, f),
76 _ => Command::new(linker),
80 let msvc_tool = windows_registry::find_tool(&sess.opts.target_triple.triple(), "link.exe");
82 // The compiler's sysroot often has some bundled tools, so add it to the
83 // PATH for the child.
84 let mut new_path = sess.host_filesearch(PathKind::All)
85 .get_tools_search_paths();
86 let mut msvc_changed_path = false;
87 if sess.target.target.options.is_like_msvc {
88 if let Some(ref tool) = msvc_tool {
89 cmd.args(tool.args());
90 for &(ref k, ref v) in tool.env() {
92 new_path.extend(env::split_paths(v));
93 msvc_changed_path = true;
101 if !msvc_changed_path {
102 if let Some(path) = env::var_os("PATH") {
103 new_path.extend(env::split_paths(&path));
106 cmd.env("PATH", env::join_paths(new_path).unwrap());
108 (linker.to_path_buf(), cmd)
111 pub fn remove(sess: &Session, path: &Path) {
112 match fs::remove_file(path) {
115 sess.err(&format!("failed to remove {}: {}",
122 /// Perform the linkage portion of the compilation phase. This will generate all
123 /// of the requested outputs for this compilation session.
124 pub(crate) fn link_binary(sess: &Session,
125 codegen_results: &CodegenResults,
126 outputs: &OutputFilenames,
127 crate_name: &str) -> Vec<PathBuf> {
128 let mut out_filenames = Vec::new();
129 for &crate_type in sess.crate_types.borrow().iter() {
130 // Ignore executable crates if we have -Z no-codegen, as they will error.
131 let output_metadata = sess.opts.output_types.contains_key(&OutputType::Metadata);
132 if (sess.opts.debugging_opts.no_codegen || !sess.opts.output_types.should_codegen()) &&
134 crate_type == config::CrateType::Executable {
138 if invalid_output_for_target(sess, crate_type) {
139 bug!("invalid output type `{:?}` for target os `{}`",
140 crate_type, sess.opts.target_triple);
142 let mut out_files = link_binary_output(sess,
147 out_filenames.append(&mut out_files);
150 // Remove the temporary object file and metadata if we aren't saving temps
151 if !sess.opts.cg.save_temps {
152 if sess.opts.output_types.should_codegen() &&
153 !preserve_objects_for_their_debuginfo(sess)
155 for obj in codegen_results.modules.iter().filter_map(|m| m.object.as_ref()) {
159 for obj in codegen_results.modules.iter().filter_map(|m| m.bytecode_compressed.as_ref()) {
162 if let Some(ref obj) = codegen_results.metadata_module.object {
165 if let Some(ref allocator) = codegen_results.allocator_module {
166 if let Some(ref obj) = allocator.object {
169 if let Some(ref bc) = allocator.bytecode_compressed {
178 /// Returns a boolean indicating whether we should preserve the object files on
179 /// the filesystem for their debug information. This is often useful with
180 /// split-dwarf like schemes.
181 fn preserve_objects_for_their_debuginfo(sess: &Session) -> bool {
182 // If the objects don't have debuginfo there's nothing to preserve.
183 if sess.opts.debuginfo == DebugInfo::None {
187 // If we're only producing artifacts that are archives, no need to preserve
188 // the objects as they're losslessly contained inside the archives.
189 let output_linked = sess.crate_types.borrow()
191 .any(|x| *x != config::CrateType::Rlib && *x != config::CrateType::Staticlib);
196 // If we're on OSX then the equivalent of split dwarf is turned on by
197 // default. The final executable won't actually have any debug information
198 // except it'll have pointers to elsewhere. Historically we've always run
199 // `dsymutil` to "link all the dwarf together" but this is actually sort of
200 // a bummer for incremental compilation! (the whole point of split dwarf is
201 // that you don't do this sort of dwarf link).
203 // Basically as a result this just means that if we're on OSX and we're
204 // *not* running dsymutil then the object files are the only source of truth
205 // for debug information, so we must preserve them.
206 if sess.target.target.options.is_like_osx {
207 match sess.opts.debugging_opts.run_dsymutil {
208 // dsymutil is not being run, preserve objects
209 Some(false) => return true,
211 // dsymutil is being run, no need to preserve the objects
212 Some(true) => return false,
214 // The default historical behavior was to always run dsymutil, so
215 // we're preserving that temporarily, but we're likely to switch the
217 None => return false,
224 fn filename_for_metadata(sess: &Session, crate_name: &str, outputs: &OutputFilenames) -> PathBuf {
225 let out_filename = outputs.single_output_file.clone()
228 .join(&format!("lib{}{}.rmeta", crate_name, sess.opts.cg.extra_filename)));
229 check_file_is_writeable(&out_filename, sess);
233 pub(crate) fn each_linked_rlib(sess: &Session,
235 f: &mut dyn FnMut(CrateNum, &Path)) -> Result<(), String> {
236 let crates = info.used_crates_static.iter();
237 let fmts = sess.dependency_formats.borrow();
238 let fmts = fmts.get(&config::CrateType::Executable)
239 .or_else(|| fmts.get(&config::CrateType::Staticlib))
240 .or_else(|| fmts.get(&config::CrateType::Cdylib))
241 .or_else(|| fmts.get(&config::CrateType::ProcMacro));
242 let fmts = match fmts {
244 None => return Err("could not find formats for rlibs".to_string())
246 for &(cnum, ref path) in crates {
247 match fmts.get(cnum.as_usize() - 1) {
248 Some(&Linkage::NotLinked) |
249 Some(&Linkage::IncludedFromDylib) => continue,
251 None => return Err("could not find formats for rlibs".to_string())
253 let name = &info.crate_name[&cnum];
254 let path = match *path {
255 LibSource::Some(ref p) => p,
256 LibSource::MetadataOnly => {
257 return Err(format!("could not find rlib for: `{}`, found rmeta (metadata) file",
261 return Err(format!("could not find rlib for: `{}`", name))
269 /// Returns a boolean indicating whether the specified crate should be ignored
272 /// Crates ignored during LTO are not lumped together in the "massive object
273 /// file" that we create and are linked in their normal rlib states. See
274 /// comments below for what crates do not participate in LTO.
276 /// It's unusual for a crate to not participate in LTO. Typically only
277 /// compiler-specific and unstable crates have a reason to not participate in
279 pub(crate) fn ignored_for_lto(sess: &Session, info: &CrateInfo, cnum: CrateNum) -> bool {
280 // If our target enables builtin function lowering in LLVM then the
281 // crates providing these functions don't participate in LTO (e.g.
282 // no_builtins or compiler builtins crates).
283 !sess.target.target.options.no_builtins &&
284 (info.is_no_builtins.contains(&cnum) || info.compiler_builtins == Some(cnum))
287 fn link_binary_output(sess: &Session,
288 codegen_results: &CodegenResults,
289 crate_type: config::CrateType,
290 outputs: &OutputFilenames,
291 crate_name: &str) -> Vec<PathBuf> {
292 for obj in codegen_results.modules.iter().filter_map(|m| m.object.as_ref()) {
293 check_file_is_writeable(obj, sess);
296 let mut out_filenames = vec![];
298 if outputs.outputs.contains_key(&OutputType::Metadata) {
299 let out_filename = filename_for_metadata(sess, crate_name, outputs);
300 // To avoid races with another rustc process scanning the output directory,
301 // we need to write the file somewhere else and atomically move it to its
302 // final destination, with a `fs::rename` call. In order for the rename to
303 // always succeed, the temporary file needs to be on the same filesystem,
304 // which is why we create it inside the output directory specifically.
305 let metadata_tmpdir = match TempFileBuilder::new()
307 .tempdir_in(out_filename.parent().unwrap())
309 Ok(tmpdir) => tmpdir,
310 Err(err) => sess.fatal(&format!("couldn't create a temp dir: {}", err)),
312 let metadata = emit_metadata(sess, codegen_results, &metadata_tmpdir);
313 if let Err(e) = fs::rename(metadata, &out_filename) {
314 sess.fatal(&format!("failed to write {}: {}", out_filename.display(), e));
316 out_filenames.push(out_filename);
319 let tmpdir = match TempFileBuilder::new().prefix("rustc").tempdir() {
320 Ok(tmpdir) => tmpdir,
321 Err(err) => sess.fatal(&format!("couldn't create a temp dir: {}", err)),
324 if outputs.outputs.should_codegen() {
325 let out_filename = out_filename(sess, crate_type, outputs, crate_name);
327 config::CrateType::Rlib => {
334 config::CrateType::Staticlib => {
335 link_staticlib(sess, codegen_results, &out_filename, &tmpdir);
338 link_natively(sess, crate_type, &out_filename, codegen_results, tmpdir.path());
341 out_filenames.push(out_filename);
344 if sess.opts.cg.save_temps {
345 let _ = tmpdir.into_path();
351 fn archive_search_paths(sess: &Session) -> Vec<PathBuf> {
352 let mut search = Vec::new();
353 sess.target_filesearch(PathKind::Native).for_each_lib_search_path(|path, _| {
354 search.push(path.to_path_buf());
359 fn archive_config<'a>(sess: &'a Session,
361 input: Option<&Path>) -> ArchiveConfig<'a> {
364 dst: output.to_path_buf(),
365 src: input.map(|p| p.to_path_buf()),
366 lib_search_paths: archive_search_paths(sess),
370 /// We use a temp directory here to avoid races between concurrent rustc processes,
371 /// such as builds in the same directory using the same filename for metadata while
372 /// building an `.rlib` (stomping over one another), or writing an `.rmeta` into a
373 /// directory being searched for `extern crate` (observing an incomplete file).
374 /// The returned path is the temporary file containing the complete metadata.
375 fn emit_metadata<'a>(sess: &'a Session, codegen_results: &CodegenResults, tmpdir: &TempDir)
377 let out_filename = tmpdir.path().join(METADATA_FILENAME);
378 let result = fs::write(&out_filename, &codegen_results.metadata.raw_data);
380 if let Err(e) = result {
381 sess.fatal(&format!("failed to write {}: {}", out_filename.display(), e));
394 // An rlib in its current incarnation is essentially a renamed .a file. The
395 // rlib primarily contains the object file of the crate, but it also contains
396 // all of the object files from native libraries. This is done by unzipping
397 // native libraries and inserting all of the contents into this archive.
398 fn link_rlib<'a>(sess: &'a Session,
399 codegen_results: &CodegenResults,
402 tmpdir: &TempDir) -> ArchiveBuilder<'a> {
403 info!("preparing rlib to {:?}", out_filename);
404 let mut ab = ArchiveBuilder::new(archive_config(sess, out_filename, None));
406 for obj in codegen_results.modules.iter().filter_map(|m| m.object.as_ref()) {
410 // Note that in this loop we are ignoring the value of `lib.cfg`. That is,
411 // we may not be configured to actually include a static library if we're
412 // adding it here. That's because later when we consume this rlib we'll
413 // decide whether we actually needed the static library or not.
415 // To do this "correctly" we'd need to keep track of which libraries added
416 // which object files to the archive. We don't do that here, however. The
417 // #[link(cfg(..))] feature is unstable, though, and only intended to get
418 // liblibc working. In that sense the check below just indicates that if
419 // there are any libraries we want to omit object files for at link time we
420 // just exclude all custom object files.
422 // Eventually if we want to stabilize or flesh out the #[link(cfg(..))]
423 // feature then we'll need to figure out how to record what objects were
424 // loaded from the libraries found here and then encode that into the
425 // metadata of the rlib we're generating somehow.
426 for lib in codegen_results.crate_info.used_libraries.iter() {
428 NativeLibraryKind::NativeStatic => {}
429 NativeLibraryKind::NativeStaticNobundle |
430 NativeLibraryKind::NativeFramework |
431 NativeLibraryKind::NativeUnknown => continue,
433 if let Some(name) = lib.name {
434 ab.add_native_library(&name.as_str());
438 // After adding all files to the archive, we need to update the
439 // symbol table of the archive.
442 // Note that it is important that we add all of our non-object "magical
443 // files" *after* all of the object files in the archive. The reason for
444 // this is as follows:
446 // * When performing LTO, this archive will be modified to remove
447 // objects from above. The reason for this is described below.
449 // * When the system linker looks at an archive, it will attempt to
450 // determine the architecture of the archive in order to see whether its
453 // The algorithm for this detection is: iterate over the files in the
454 // archive. Skip magical SYMDEF names. Interpret the first file as an
455 // object file. Read architecture from the object file.
457 // * As one can probably see, if "metadata" and "foo.bc" were placed
458 // before all of the objects, then the architecture of this archive would
459 // not be correctly inferred once 'foo.o' is removed.
461 // Basically, all this means is that this code should not move above the
464 RlibFlavor::Normal => {
465 // Instead of putting the metadata in an object file section, rlibs
466 // contain the metadata in a separate file.
467 ab.add_file(&emit_metadata(sess, codegen_results, tmpdir));
469 // For LTO purposes, the bytecode of this library is also inserted
471 for bytecode in codegen_results
474 .filter_map(|m| m.bytecode_compressed.as_ref())
476 ab.add_file(bytecode);
479 // After adding all files to the archive, we need to update the
480 // symbol table of the archive. This currently dies on macOS (see
481 // #11162), and isn't necessary there anyway
482 if !sess.target.target.options.is_like_osx {
487 RlibFlavor::StaticlibBase => {
488 let obj = codegen_results.allocator_module
490 .and_then(|m| m.object.as_ref());
491 if let Some(obj) = obj {
500 // Create a static archive
502 // This is essentially the same thing as an rlib, but it also involves adding
503 // all of the upstream crates' objects into the archive. This will slurp in
504 // all of the native libraries of upstream dependencies as well.
506 // Additionally, there's no way for us to link dynamic libraries, so we warn
507 // about all dynamic library dependencies that they're not linked in.
509 // There's no need to include metadata in a static archive, so ensure to not
510 // link in the metadata object file (and also don't prepare the archive with a
512 fn link_staticlib(sess: &Session,
513 codegen_results: &CodegenResults,
516 let mut ab = link_rlib(sess,
518 RlibFlavor::StaticlibBase,
521 let mut all_native_libs = vec![];
523 let res = each_linked_rlib(sess, &codegen_results.crate_info, &mut |cnum, path| {
524 let name = &codegen_results.crate_info.crate_name[&cnum];
525 let native_libs = &codegen_results.crate_info.native_libraries[&cnum];
527 // Here when we include the rlib into our staticlib we need to make a
528 // decision whether to include the extra object files along the way.
529 // These extra object files come from statically included native
530 // libraries, but they may be cfg'd away with #[link(cfg(..))].
532 // This unstable feature, though, only needs liblibc to work. The only
533 // use case there is where musl is statically included in liblibc.rlib,
534 // so if we don't want the included version we just need to skip it. As
535 // a result the logic here is that if *any* linked library is cfg'd away
536 // we just skip all object files.
538 // Clearly this is not sufficient for a general purpose feature, and
539 // we'd want to read from the library's metadata to determine which
540 // object files come from where and selectively skip them.
541 let skip_object_files = native_libs.iter().any(|lib| {
542 lib.kind == NativeLibraryKind::NativeStatic && !relevant_lib(sess, lib)
546 are_upstream_rust_objects_already_included(sess) &&
547 !ignored_for_lto(sess, &codegen_results.crate_info, cnum),
548 skip_object_files).unwrap();
550 all_native_libs.extend(codegen_results.crate_info.native_libraries[&cnum].iter().cloned());
552 if let Err(e) = res {
559 if !all_native_libs.is_empty() {
560 if sess.opts.prints.contains(&PrintRequest::NativeStaticLibs) {
561 print_native_static_libs(sess, &all_native_libs);
566 fn print_native_static_libs(sess: &Session, all_native_libs: &[NativeLibrary]) {
567 let lib_args: Vec<_> = all_native_libs.iter()
568 .filter(|l| relevant_lib(sess, l))
570 let name = lib.name?;
572 NativeLibraryKind::NativeStaticNobundle |
573 NativeLibraryKind::NativeUnknown => {
574 if sess.target.target.options.is_like_msvc {
575 Some(format!("{}.lib", name))
577 Some(format!("-l{}", name))
580 NativeLibraryKind::NativeFramework => {
581 // ld-only syntax, since there are no frameworks in MSVC
582 Some(format!("-framework {}", name))
584 // These are included, no need to print them
585 NativeLibraryKind::NativeStatic => None,
589 if !lib_args.is_empty() {
590 sess.note_without_error("Link against the following native artifacts when linking \
591 against this static library. The order and any duplication \
592 can be significant on some platforms.");
593 // Prefix for greppability
594 sess.note_without_error(&format!("native-static-libs: {}", &lib_args.join(" ")));
598 pub fn linker_and_flavor(sess: &Session) -> (PathBuf, LinkerFlavor) {
601 linker: Option<PathBuf>,
602 flavor: Option<LinkerFlavor>,
603 ) -> Option<(PathBuf, LinkerFlavor)> {
604 match (linker, flavor) {
605 (Some(linker), Some(flavor)) => Some((linker, flavor)),
606 // only the linker flavor is known; use the default linker for the selected flavor
607 (None, Some(flavor)) => Some((PathBuf::from(match flavor {
608 LinkerFlavor::Em => if cfg!(windows) { "emcc.bat" } else { "emcc" },
609 LinkerFlavor::Gcc => "cc",
610 LinkerFlavor::Ld => "ld",
611 LinkerFlavor::Msvc => "link.exe",
612 LinkerFlavor::Lld(_) => "lld",
614 (Some(linker), None) => {
615 let stem = linker.file_stem().and_then(|stem| stem.to_str()).unwrap_or_else(|| {
616 sess.fatal("couldn't extract file stem from specified linker");
619 let flavor = if stem == "emcc" {
621 } else if stem == "gcc" || stem.ends_with("-gcc") {
623 } else if stem == "ld" || stem == "ld.lld" || stem.ends_with("-ld") {
625 } else if stem == "link" || stem == "lld-link" {
627 } else if stem == "lld" || stem == "rust-lld" {
628 LinkerFlavor::Lld(sess.target.target.options.lld_flavor)
630 // fall back to the value in the target spec
631 sess.target.target.linker_flavor
634 Some((linker, flavor))
636 (None, None) => None,
640 // linker and linker flavor specified via command line have precedence over what the target
641 // specification specifies
642 if let Some(ret) = infer_from(
644 sess.opts.cg.linker.clone(),
645 sess.opts.debugging_opts.linker_flavor,
650 if let Some(ret) = infer_from(
652 sess.target.target.options.linker.clone().map(PathBuf::from),
653 Some(sess.target.target.linker_flavor),
658 bug!("Not enough information provided to determine how to invoke the linker");
661 // Create a dynamic library or executable
663 // This will invoke the system linker/cc to create the resulting file. This
664 // links to all upstream files as well.
665 fn link_natively(sess: &Session,
666 crate_type: config::CrateType,
668 codegen_results: &CodegenResults,
670 info!("preparing {:?} to {:?}", crate_type, out_filename);
671 let (linker, flavor) = linker_and_flavor(sess);
673 // The invocations of cc share some flags across platforms
674 let (pname, mut cmd) = get_linker(sess, &linker, flavor);
676 let root = sess.target_filesearch(PathKind::Native).get_lib_path();
677 if let Some(args) = sess.target.target.options.pre_link_args.get(&flavor) {
680 if let Some(args) = sess.target.target.options.pre_link_args_crt.get(&flavor) {
681 if sess.crt_static() {
685 if let Some(ref args) = sess.opts.debugging_opts.pre_link_args {
688 cmd.args(&sess.opts.debugging_opts.pre_link_arg);
690 let pre_link_objects = if crate_type == config::CrateType::Executable {
691 &sess.target.target.options.pre_link_objects_exe
693 &sess.target.target.options.pre_link_objects_dll
695 for obj in pre_link_objects {
696 cmd.arg(root.join(obj));
699 if crate_type == config::CrateType::Executable && sess.crt_static() {
700 for obj in &sess.target.target.options.pre_link_objects_exe_crt {
701 cmd.arg(root.join(obj));
705 if sess.target.target.options.is_like_emscripten {
707 cmd.arg(if sess.panic_strategy() == PanicStrategy::Abort {
708 "DISABLE_EXCEPTION_CATCHING=1"
710 "DISABLE_EXCEPTION_CATCHING=0"
715 let mut linker = codegen_results.linker_info.to_linker(cmd, &sess, flavor);
716 link_args(&mut *linker, flavor, sess, crate_type, tmpdir,
717 out_filename, codegen_results);
718 cmd = linker.finalize();
720 if let Some(args) = sess.target.target.options.late_link_args.get(&flavor) {
723 for obj in &sess.target.target.options.post_link_objects {
724 cmd.arg(root.join(obj));
726 if sess.crt_static() {
727 for obj in &sess.target.target.options.post_link_objects_crt {
728 cmd.arg(root.join(obj));
731 if let Some(args) = sess.target.target.options.post_link_args.get(&flavor) {
734 for &(ref k, ref v) in &sess.target.target.options.link_env {
738 if sess.opts.debugging_opts.print_link_args {
739 println!("{:?}", &cmd);
742 // May have not found libraries in the right formats.
743 sess.abort_if_errors();
745 // Invoke the system linker
747 // Note that there's a terribly awful hack that really shouldn't be present
748 // in any compiler. Here an environment variable is supported to
749 // automatically retry the linker invocation if the linker looks like it
752 // Gee that seems odd, normally segfaults are things we want to know about!
753 // Unfortunately though in rust-lang/rust#38878 we're experiencing the
754 // linker segfaulting on Travis quite a bit which is causing quite a bit of
755 // pain to land PRs when they spuriously fail due to a segfault.
757 // The issue #38878 has some more debugging information on it as well, but
758 // this unfortunately looks like it's just a race condition in macOS's linker
759 // with some thread pool working in the background. It seems that no one
760 // currently knows a fix for this so in the meantime we're left with this...
762 let retry_on_segfault = env::var("RUSTC_RETRY_LINKER_ON_SEGFAULT").is_ok();
767 prog = time(sess, "running linker", || {
768 exec_linker(sess, &mut cmd, out_filename, tmpdir)
770 let output = match prog {
771 Ok(ref output) => output,
774 if output.status.success() {
777 let mut out = output.stderr.clone();
778 out.extend(&output.stdout);
779 let out = String::from_utf8_lossy(&out);
781 // Check to see if the link failed with "unrecognized command line option:
782 // '-no-pie'" for gcc or "unknown argument: '-no-pie'" for clang. If so,
783 // reperform the link step without the -no-pie option. This is safe because
784 // if the linker doesn't support -no-pie then it should not default to
785 // linking executables as pie. Different versions of gcc seem to use
786 // different quotes in the error message so don't check for them.
787 if sess.target.target.options.linker_is_gnu &&
788 flavor != LinkerFlavor::Ld &&
789 (out.contains("unrecognized command line option") ||
790 out.contains("unknown argument")) &&
791 out.contains("-no-pie") &&
792 cmd.get_args().iter().any(|e| e.to_string_lossy() == "-no-pie") {
793 info!("linker output: {:?}", out);
794 warn!("Linker does not support -no-pie command line option. Retrying without.");
795 for arg in cmd.take_args() {
796 if arg.to_string_lossy() != "-no-pie" {
803 if !retry_on_segfault || i > 3 {
806 let msg_segv = "clang: error: unable to execute command: Segmentation fault: 11";
807 let msg_bus = "clang: error: unable to execute command: Bus error: 10";
808 if !(out.contains(msg_segv) || out.contains(msg_bus)) {
813 "looks like the linker segfaulted when we tried to call it, \
814 automatically retrying again. cmd = {:?}, out = {}.",
822 fn escape_string(s: &[u8]) -> String {
823 str::from_utf8(s).map(|s| s.to_owned())
824 .unwrap_or_else(|_| {
825 let mut x = "Non-UTF-8 output: ".to_string();
827 .flat_map(|&b| ascii::escape_default(b))
828 .map(|b| char::from_u32(b as u32).unwrap()));
832 if !prog.status.success() {
833 let mut output = prog.stderr.clone();
834 output.extend_from_slice(&prog.stdout);
835 sess.struct_err(&format!("linking with `{}` failed: {}",
838 .note(&format!("{:?}", &cmd))
839 .note(&escape_string(&output))
841 sess.abort_if_errors();
843 info!("linker stderr:\n{}", escape_string(&prog.stderr));
844 info!("linker stdout:\n{}", escape_string(&prog.stdout));
847 let linker_not_found = e.kind() == io::ErrorKind::NotFound;
849 let mut linker_error = {
850 if linker_not_found {
851 sess.struct_err(&format!("linker `{}` not found", pname.display()))
853 sess.struct_err(&format!("could not exec the linker `{}`", pname.display()))
857 linker_error.note(&e.to_string());
859 if !linker_not_found {
860 linker_error.note(&format!("{:?}", &cmd));
865 if sess.target.target.options.is_like_msvc && linker_not_found {
866 sess.note_without_error("the msvc targets depend on the msvc linker \
867 but `link.exe` was not found");
868 sess.note_without_error("please ensure that VS 2013, VS 2015 or VS 2017 \
869 was installed with the Visual C++ option");
871 sess.abort_if_errors();
876 // On macOS, debuggers need this utility to get run to do some munging of
877 // the symbols. Note, though, that if the object files are being preserved
878 // for their debug information there's no need for us to run dsymutil.
879 if sess.target.target.options.is_like_osx &&
880 sess.opts.debuginfo != DebugInfo::None &&
881 !preserve_objects_for_their_debuginfo(sess)
883 match Command::new("dsymutil").arg(out_filename).output() {
885 Err(e) => sess.fatal(&format!("failed to run dsymutil: {}", e)),
889 if sess.opts.target_triple.triple() == "wasm32-unknown-unknown" {
890 wasm::rewrite_imports(&out_filename, &codegen_results.crate_info.wasm_imports);
894 fn exec_linker(sess: &Session, cmd: &mut Command, out_filename: &Path, tmpdir: &Path)
895 -> io::Result<Output>
897 // When attempting to spawn the linker we run a risk of blowing out the
898 // size limits for spawning a new process with respect to the arguments
899 // we pass on the command line.
901 // Here we attempt to handle errors from the OS saying "your list of
902 // arguments is too big" by reinvoking the linker again with an `@`-file
903 // that contains all the arguments. The theory is that this is then
904 // accepted on all linkers and the linker will read all its options out of
905 // there instead of looking at the command line.
906 if !cmd.very_likely_to_exceed_some_spawn_limit() {
907 match cmd.command().stdout(Stdio::piped()).stderr(Stdio::piped()).spawn() {
909 let output = child.wait_with_output();
910 flush_linked_file(&output, out_filename)?;
913 Err(ref e) if command_line_too_big(e) => {
914 info!("command line to linker was too big: {}", e);
916 Err(e) => return Err(e)
920 info!("falling back to passing arguments to linker via an @-file");
921 let mut cmd2 = cmd.clone();
922 let mut args = String::new();
923 for arg in cmd2.take_args() {
924 args.push_str(&Escape {
925 arg: arg.to_str().unwrap(),
926 is_like_msvc: sess.target.target.options.is_like_msvc,
930 let file = tmpdir.join("linker-arguments");
931 let bytes = if sess.target.target.options.is_like_msvc {
932 let mut out = Vec::with_capacity((1 + args.len()) * 2);
933 // start the stream with a UTF-16 BOM
934 for c in iter::once(0xFEFF).chain(args.encode_utf16()) {
935 // encode in little endian
937 out.push((c >> 8) as u8);
943 fs::write(&file, &bytes)?;
944 cmd2.arg(format!("@{}", file.display()));
945 info!("invoking linker {:?}", cmd2);
946 let output = cmd2.output();
947 flush_linked_file(&output, out_filename)?;
951 fn flush_linked_file(_: &io::Result<Output>, _: &Path) -> io::Result<()> {
956 fn flush_linked_file(command_output: &io::Result<Output>, out_filename: &Path)
959 // On Windows, under high I/O load, output buffers are sometimes not flushed,
960 // even long after process exit, causing nasty, non-reproducible output bugs.
962 // File::sync_all() calls FlushFileBuffers() down the line, which solves the problem.
964 // А full writeup of the original Chrome bug can be found at
965 // randomascii.wordpress.com/2018/02/25/compiler-bug-linker-bug-windows-kernel-bug/amp
967 if let &Ok(ref out) = command_output {
968 if out.status.success() {
969 if let Ok(of) = fs::OpenOptions::new().write(true).open(out_filename) {
979 fn command_line_too_big(err: &io::Error) -> bool {
980 err.raw_os_error() == Some(::libc::E2BIG)
984 fn command_line_too_big(err: &io::Error) -> bool {
985 const ERROR_FILENAME_EXCED_RANGE: i32 = 206;
986 err.raw_os_error() == Some(ERROR_FILENAME_EXCED_RANGE)
994 impl<'a> fmt::Display for Escape<'a> {
995 fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
996 if self.is_like_msvc {
997 // This is "documented" at
998 // https://msdn.microsoft.com/en-us/library/4xdcbak7.aspx
1000 // Unfortunately there's not a great specification of the
1001 // syntax I could find online (at least) but some local
1002 // testing showed that this seemed sufficient-ish to catch
1003 // at least a few edge cases.
1005 for c in self.arg.chars() {
1007 '"' => write!(f, "\\{}", c)?,
1008 c => write!(f, "{}", c)?,
1013 // This is documented at https://linux.die.net/man/1/ld, namely:
1015 // > Options in file are separated by whitespace. A whitespace
1016 // > character may be included in an option by surrounding the
1017 // > entire option in either single or double quotes. Any
1018 // > character (including a backslash) may be included by
1019 // > prefixing the character to be included with a backslash.
1021 // We put an argument on each line, so all we need to do is
1022 // ensure the line is interpreted as one whole argument.
1023 for c in self.arg.chars() {
1026 ' ' => write!(f, "\\{}", c)?,
1027 c => write!(f, "{}", c)?,
1036 fn link_args(cmd: &mut dyn Linker,
1037 flavor: LinkerFlavor,
1039 crate_type: config::CrateType,
1041 out_filename: &Path,
1042 codegen_results: &CodegenResults) {
1044 // Linker plugins should be specified early in the list of arguments
1045 cmd.cross_lang_lto();
1047 // The default library location, we need this to find the runtime.
1048 // The location of crates will be determined as needed.
1049 let lib_path = sess.target_filesearch(PathKind::All).get_lib_path();
1051 // target descriptor
1052 let t = &sess.target.target;
1054 cmd.include_path(&fix_windows_verbatim_for_gcc(&lib_path));
1055 for obj in codegen_results.modules.iter().filter_map(|m| m.object.as_ref()) {
1056 cmd.add_object(obj);
1058 cmd.output_filename(out_filename);
1060 if crate_type == config::CrateType::Executable &&
1061 sess.target.target.options.is_like_windows {
1062 if let Some(ref s) = codegen_results.windows_subsystem {
1067 // If we're building a dynamic library then some platforms need to make sure
1068 // that all symbols are exported correctly from the dynamic library.
1069 if crate_type != config::CrateType::Executable ||
1070 sess.target.target.options.is_like_emscripten {
1071 cmd.export_symbols(tmpdir, crate_type);
1074 // When linking a dynamic library, we put the metadata into a section of the
1075 // executable. This metadata is in a separate object file from the main
1076 // object file, so we link that in here.
1077 if crate_type == config::CrateType::Dylib ||
1078 crate_type == config::CrateType::ProcMacro {
1079 if let Some(obj) = codegen_results.metadata_module.object.as_ref() {
1080 cmd.add_object(obj);
1084 let obj = codegen_results.allocator_module
1086 .and_then(|m| m.object.as_ref());
1087 if let Some(obj) = obj {
1088 cmd.add_object(obj);
1091 // Try to strip as much out of the generated object by removing unused
1092 // sections if possible. See more comments in linker.rs
1093 if !sess.opts.cg.link_dead_code {
1094 let keep_metadata = crate_type == config::CrateType::Dylib;
1095 cmd.gc_sections(keep_metadata);
1098 let used_link_args = &codegen_results.crate_info.link_args;
1100 if crate_type == config::CrateType::Executable {
1101 let mut position_independent_executable = false;
1103 if t.options.position_independent_executables {
1104 let empty_vec = Vec::new();
1105 let args = sess.opts.cg.link_args.as_ref().unwrap_or(&empty_vec);
1106 let more_args = &sess.opts.cg.link_arg;
1107 let mut args = args.iter().chain(more_args.iter()).chain(used_link_args.iter());
1109 if get_reloc_model(sess) == llvm::RelocMode::PIC
1110 && !sess.crt_static() && !args.any(|x| *x == "-static") {
1111 position_independent_executable = true;
1115 if position_independent_executable {
1116 cmd.position_independent_executable();
1118 // recent versions of gcc can be configured to generate position
1119 // independent executables by default. We have to pass -no-pie to
1120 // explicitly turn that off. Not applicable to ld.
1121 if sess.target.target.options.linker_is_gnu
1122 && flavor != LinkerFlavor::Ld {
1123 cmd.no_position_independent_executable();
1128 let relro_level = match sess.opts.debugging_opts.relro_level {
1129 Some(level) => level,
1130 None => t.options.relro_level,
1133 RelroLevel::Full => {
1136 RelroLevel::Partial => {
1137 cmd.partial_relro();
1139 RelroLevel::Off => {
1142 RelroLevel::None => {
1146 // Pass optimization flags down to the linker.
1149 // Pass debuginfo flags down to the linker.
1152 // We want to prevent the compiler from accidentally leaking in any system
1153 // libraries, so we explicitly ask gcc to not link to any libraries by
1154 // default. Note that this does not happen for windows because windows pulls
1155 // in some large number of libraries and I couldn't quite figure out which
1156 // subset we wanted.
1157 if t.options.no_default_libraries {
1158 cmd.no_default_libraries();
1161 // Take careful note of the ordering of the arguments we pass to the linker
1162 // here. Linkers will assume that things on the left depend on things to the
1163 // right. Things on the right cannot depend on things on the left. This is
1164 // all formally implemented in terms of resolving symbols (libs on the right
1165 // resolve unknown symbols of libs on the left, but not vice versa).
1167 // For this reason, we have organized the arguments we pass to the linker as
1170 // 1. The local object that LLVM just generated
1171 // 2. Local native libraries
1172 // 3. Upstream rust libraries
1173 // 4. Upstream native libraries
1175 // The rationale behind this ordering is that those items lower down in the
1176 // list can't depend on items higher up in the list. For example nothing can
1177 // depend on what we just generated (e.g. that'd be a circular dependency).
1178 // Upstream rust libraries are not allowed to depend on our local native
1179 // libraries as that would violate the structure of the DAG, in that
1180 // scenario they are required to link to them as well in a shared fashion.
1182 // Note that upstream rust libraries may contain native dependencies as
1183 // well, but they also can't depend on what we just started to add to the
1184 // link line. And finally upstream native libraries can't depend on anything
1185 // in this DAG so far because they're only dylibs and dylibs can only depend
1186 // on other dylibs (e.g. other native deps).
1187 add_local_native_libraries(cmd, sess, codegen_results);
1188 add_upstream_rust_crates(cmd, sess, codegen_results, crate_type, tmpdir);
1189 add_upstream_native_libraries(cmd, sess, codegen_results, crate_type);
1191 // Tell the linker what we're doing.
1192 if crate_type != config::CrateType::Executable {
1193 cmd.build_dylib(out_filename);
1195 if crate_type == config::CrateType::Executable && sess.crt_static() {
1196 cmd.build_static_executable();
1199 if sess.opts.debugging_opts.pgo_gen.is_some() {
1203 // FIXME (#2397): At some point we want to rpath our guesses as to
1204 // where extern libraries might live, based on the
1205 // addl_lib_search_paths
1206 if sess.opts.cg.rpath {
1207 let sysroot = sess.sysroot();
1208 let target_triple = sess.opts.target_triple.triple();
1209 let mut get_install_prefix_lib_path = || {
1210 let install_prefix = option_env!("CFG_PREFIX").expect("CFG_PREFIX");
1211 let tlib = filesearch::relative_target_lib_path(sysroot, target_triple);
1212 let mut path = PathBuf::from(install_prefix);
1217 let mut rpath_config = RPathConfig {
1218 used_crates: &codegen_results.crate_info.used_crates_dynamic,
1219 out_filename: out_filename.to_path_buf(),
1220 has_rpath: sess.target.target.options.has_rpath,
1221 is_like_osx: sess.target.target.options.is_like_osx,
1222 linker_is_gnu: sess.target.target.options.linker_is_gnu,
1223 get_install_prefix_lib_path: &mut get_install_prefix_lib_path,
1225 cmd.args(&rpath::get_rpath_flags(&mut rpath_config));
1228 // Finally add all the linker arguments provided on the command line along
1229 // with any #[link_args] attributes found inside the crate
1230 if let Some(ref args) = sess.opts.cg.link_args {
1233 cmd.args(&sess.opts.cg.link_arg);
1234 cmd.args(&used_link_args);
1237 // # Native library linking
1239 // User-supplied library search paths (-L on the command line). These are
1240 // the same paths used to find Rust crates, so some of them may have been
1241 // added already by the previous crate linking code. This only allows them
1242 // to be found at compile time so it is still entirely up to outside
1243 // forces to make sure that library can be found at runtime.
1245 // Also note that the native libraries linked here are only the ones located
1246 // in the current crate. Upstream crates with native library dependencies
1247 // may have their native library pulled in above.
1248 fn add_local_native_libraries(cmd: &mut dyn Linker,
1250 codegen_results: &CodegenResults) {
1251 sess.target_filesearch(PathKind::All).for_each_lib_search_path(|path, k| {
1253 PathKind::Framework => { cmd.framework_path(path); }
1254 _ => { cmd.include_path(&fix_windows_verbatim_for_gcc(path)); }
1258 let relevant_libs = codegen_results.crate_info.used_libraries.iter().filter(|l| {
1259 relevant_lib(sess, l)
1262 let search_path = archive_search_paths(sess);
1263 for lib in relevant_libs {
1264 let name = match lib.name {
1269 NativeLibraryKind::NativeUnknown => cmd.link_dylib(&name.as_str()),
1270 NativeLibraryKind::NativeFramework => cmd.link_framework(&name.as_str()),
1271 NativeLibraryKind::NativeStaticNobundle => cmd.link_staticlib(&name.as_str()),
1272 NativeLibraryKind::NativeStatic => cmd.link_whole_staticlib(&name.as_str(),
1278 // # Rust Crate linking
1280 // Rust crates are not considered at all when creating an rlib output. All
1281 // dependencies will be linked when producing the final output (instead of
1282 // the intermediate rlib version)
1283 fn add_upstream_rust_crates(cmd: &mut dyn Linker,
1285 codegen_results: &CodegenResults,
1286 crate_type: config::CrateType,
1288 // All of the heavy lifting has previously been accomplished by the
1289 // dependency_format module of the compiler. This is just crawling the
1290 // output of that module, adding crates as necessary.
1292 // Linking to a rlib involves just passing it to the linker (the linker
1293 // will slurp up the object files inside), and linking to a dynamic library
1294 // involves just passing the right -l flag.
1296 let formats = sess.dependency_formats.borrow();
1297 let data = formats.get(&crate_type).unwrap();
1299 // Invoke get_used_crates to ensure that we get a topological sorting of
1301 let deps = &codegen_results.crate_info.used_crates_dynamic;
1303 // There's a few internal crates in the standard library (aka libcore and
1304 // libstd) which actually have a circular dependence upon one another. This
1305 // currently arises through "weak lang items" where libcore requires things
1306 // like `rust_begin_unwind` but libstd ends up defining it. To get this
1307 // circular dependence to work correctly in all situations we'll need to be
1308 // sure to correctly apply the `--start-group` and `--end-group` options to
1309 // GNU linkers, otherwise if we don't use any other symbol from the standard
1310 // library it'll get discarded and the whole application won't link.
1312 // In this loop we're calculating the `group_end`, after which crate to
1313 // pass `--end-group` and `group_start`, before which crate to pass
1314 // `--start-group`. We currently do this by passing `--end-group` after
1315 // the first crate (when iterating backwards) that requires a lang item
1316 // defined somewhere else. Once that's set then when we've defined all the
1317 // necessary lang items we'll pass `--start-group`.
1319 // Note that this isn't amazing logic for now but it should do the trick
1320 // for the current implementation of the standard library.
1321 let mut group_end = None;
1322 let mut group_start = None;
1323 let mut end_with = FxHashSet();
1324 let info = &codegen_results.crate_info;
1325 for &(cnum, _) in deps.iter().rev() {
1326 if let Some(missing) = info.missing_lang_items.get(&cnum) {
1327 end_with.extend(missing.iter().cloned());
1328 if end_with.len() > 0 && group_end.is_none() {
1329 group_end = Some(cnum);
1332 end_with.retain(|item| info.lang_item_to_crate.get(item) != Some(&cnum));
1333 if end_with.len() == 0 && group_end.is_some() {
1334 group_start = Some(cnum);
1339 // If we didn't end up filling in all lang items from upstream crates then
1340 // we'll be filling it in with our crate. This probably means we're the
1341 // standard library itself, so skip this for now.
1342 if group_end.is_some() && group_start.is_none() {
1346 let mut compiler_builtins = None;
1348 for &(cnum, _) in deps.iter() {
1349 if group_start == Some(cnum) {
1353 // We may not pass all crates through to the linker. Some crates may
1354 // appear statically in an existing dylib, meaning we'll pick up all the
1355 // symbols from the dylib.
1356 let src = &codegen_results.crate_info.used_crate_source[&cnum];
1357 match data[cnum.as_usize() - 1] {
1358 _ if codegen_results.crate_info.profiler_runtime == Some(cnum) => {
1359 add_static_crate(cmd, sess, codegen_results, tmpdir, crate_type, cnum);
1361 _ if codegen_results.crate_info.sanitizer_runtime == Some(cnum) => {
1362 link_sanitizer_runtime(cmd, sess, codegen_results, tmpdir, cnum);
1364 // compiler-builtins are always placed last to ensure that they're
1365 // linked correctly.
1366 _ if codegen_results.crate_info.compiler_builtins == Some(cnum) => {
1367 assert!(compiler_builtins.is_none());
1368 compiler_builtins = Some(cnum);
1370 Linkage::NotLinked |
1371 Linkage::IncludedFromDylib => {}
1372 Linkage::Static => {
1373 add_static_crate(cmd, sess, codegen_results, tmpdir, crate_type, cnum);
1375 Linkage::Dynamic => {
1376 add_dynamic_crate(cmd, sess, &src.dylib.as_ref().unwrap().0)
1380 if group_end == Some(cnum) {
1385 // compiler-builtins are always placed last to ensure that they're
1386 // linked correctly.
1387 // We must always link the `compiler_builtins` crate statically. Even if it
1388 // was already "included" in a dylib (e.g. `libstd` when `-C prefer-dynamic`
1390 if let Some(cnum) = compiler_builtins {
1391 add_static_crate(cmd, sess, codegen_results, tmpdir, crate_type, cnum);
1394 // Converts a library file-stem into a cc -l argument
1395 fn unlib<'a>(config: &config::Config, stem: &'a str) -> &'a str {
1396 if stem.starts_with("lib") && !config.target.options.is_like_windows {
1403 // We must link the sanitizer runtime using -Wl,--whole-archive but since
1404 // it's packed in a .rlib, it contains stuff that are not objects that will
1405 // make the linker error. So we must remove those bits from the .rlib before
1407 fn link_sanitizer_runtime(cmd: &mut dyn Linker,
1409 codegen_results: &CodegenResults,
1412 let src = &codegen_results.crate_info.used_crate_source[&cnum];
1413 let cratepath = &src.rlib.as_ref().unwrap().0;
1415 if sess.target.target.options.is_like_osx {
1416 // On Apple platforms, the sanitizer is always built as a dylib, and
1417 // LLVM will link to `@rpath/*.dylib`, so we need to specify an
1418 // rpath to the library as well (the rpath should be absolute, see
1419 // PR #41352 for details).
1421 // FIXME: Remove this logic into librustc_*san once Cargo supports it
1422 let rpath = cratepath.parent().unwrap();
1423 let rpath = rpath.to_str().expect("non-utf8 component in path");
1424 cmd.args(&["-Wl,-rpath".into(), "-Xlinker".into(), rpath.into()]);
1427 let dst = tmpdir.join(cratepath.file_name().unwrap());
1428 let cfg = archive_config(sess, &dst, Some(cratepath));
1429 let mut archive = ArchiveBuilder::new(cfg);
1430 archive.update_symbols();
1432 for f in archive.src_files() {
1433 if f.ends_with(RLIB_BYTECODE_EXTENSION) || f == METADATA_FILENAME {
1434 archive.remove_file(&f);
1441 cmd.link_whole_rlib(&dst);
1444 // Adds the static "rlib" versions of all crates to the command line.
1445 // There's a bit of magic which happens here specifically related to LTO and
1446 // dynamic libraries. Specifically:
1448 // * For LTO, we remove upstream object files.
1449 // * For dylibs we remove metadata and bytecode from upstream rlibs
1451 // When performing LTO, almost(*) all of the bytecode from the upstream
1452 // libraries has already been included in our object file output. As a
1453 // result we need to remove the object files in the upstream libraries so
1454 // the linker doesn't try to include them twice (or whine about duplicate
1455 // symbols). We must continue to include the rest of the rlib, however, as
1456 // it may contain static native libraries which must be linked in.
1458 // (*) Crates marked with `#![no_builtins]` don't participate in LTO and
1459 // their bytecode wasn't included. The object files in those libraries must
1460 // still be passed to the linker.
1462 // When making a dynamic library, linkers by default don't include any
1463 // object files in an archive if they're not necessary to resolve the link.
1464 // We basically want to convert the archive (rlib) to a dylib, though, so we
1465 // *do* want everything included in the output, regardless of whether the
1466 // linker thinks it's needed or not. As a result we must use the
1467 // --whole-archive option (or the platform equivalent). When using this
1468 // option the linker will fail if there are non-objects in the archive (such
1469 // as our own metadata and/or bytecode). All in all, for rlibs to be
1470 // entirely included in dylibs, we need to remove all non-object files.
1472 // Note, however, that if we're not doing LTO or we're not producing a dylib
1473 // (aka we're making an executable), we can just pass the rlib blindly to
1474 // the linker (fast) because it's fine if it's not actually included as
1475 // we're at the end of the dependency chain.
1476 fn add_static_crate(cmd: &mut dyn Linker,
1478 codegen_results: &CodegenResults,
1480 crate_type: config::CrateType,
1482 let src = &codegen_results.crate_info.used_crate_source[&cnum];
1483 let cratepath = &src.rlib.as_ref().unwrap().0;
1485 // See the comment above in `link_staticlib` and `link_rlib` for why if
1486 // there's a static library that's not relevant we skip all object
1488 let native_libs = &codegen_results.crate_info.native_libraries[&cnum];
1489 let skip_native = native_libs.iter().any(|lib| {
1490 lib.kind == NativeLibraryKind::NativeStatic && !relevant_lib(sess, lib)
1493 if (!are_upstream_rust_objects_already_included(sess) ||
1494 ignored_for_lto(sess, &codegen_results.crate_info, cnum)) &&
1495 crate_type != config::CrateType::Dylib &&
1497 cmd.link_rlib(&fix_windows_verbatim_for_gcc(cratepath));
1501 let dst = tmpdir.join(cratepath.file_name().unwrap());
1502 let name = cratepath.file_name().unwrap().to_str().unwrap();
1503 let name = &name[3..name.len() - 5]; // chop off lib/.rlib
1505 time(sess, &format!("altering {}.rlib", name), || {
1506 let cfg = archive_config(sess, &dst, Some(cratepath));
1507 let mut archive = ArchiveBuilder::new(cfg);
1508 archive.update_symbols();
1510 let mut any_objects = false;
1511 for f in archive.src_files() {
1512 if f.ends_with(RLIB_BYTECODE_EXTENSION) || f == METADATA_FILENAME {
1513 archive.remove_file(&f);
1517 let canonical = f.replace("-", "_");
1518 let canonical_name = name.replace("-", "_");
1520 // Look for `.rcgu.o` at the end of the filename to conclude
1521 // that this is a Rust-related object file.
1522 fn looks_like_rust(s: &str) -> bool {
1523 let path = Path::new(s);
1524 let ext = path.extension().and_then(|s| s.to_str());
1525 if ext != Some(OutputType::Object.extension()) {
1528 let ext2 = path.file_stem()
1529 .and_then(|s| Path::new(s).extension())
1530 .and_then(|s| s.to_str());
1531 ext2 == Some(RUST_CGU_EXT)
1534 let is_rust_object =
1535 canonical.starts_with(&canonical_name) &&
1536 looks_like_rust(&f);
1538 // If we've been requested to skip all native object files
1539 // (those not generated by the rust compiler) then we can skip
1540 // this file. See above for why we may want to do this.
1541 let skip_because_cfg_say_so = skip_native && !is_rust_object;
1543 // If we're performing LTO and this is a rust-generated object
1544 // file, then we don't need the object file as it's part of the
1545 // LTO module. Note that `#![no_builtins]` is excluded from LTO,
1546 // though, so we let that object file slide.
1547 let skip_because_lto = are_upstream_rust_objects_already_included(sess) &&
1549 (sess.target.target.options.no_builtins ||
1550 !codegen_results.crate_info.is_no_builtins.contains(&cnum));
1552 if skip_because_cfg_say_so || skip_because_lto {
1553 archive.remove_file(&f);
1564 // If we're creating a dylib, then we need to include the
1565 // whole of each object in our archive into that artifact. This is
1566 // because a `dylib` can be reused as an intermediate artifact.
1568 // Note, though, that we don't want to include the whole of a
1569 // compiler-builtins crate (e.g. compiler-rt) because it'll get
1570 // repeatedly linked anyway.
1571 if crate_type == config::CrateType::Dylib &&
1572 codegen_results.crate_info.compiler_builtins != Some(cnum) {
1573 cmd.link_whole_rlib(&fix_windows_verbatim_for_gcc(&dst));
1575 cmd.link_rlib(&fix_windows_verbatim_for_gcc(&dst));
1580 // Same thing as above, but for dynamic crates instead of static crates.
1581 fn add_dynamic_crate(cmd: &mut dyn Linker, sess: &Session, cratepath: &Path) {
1582 // If we're performing LTO, then it should have been previously required
1583 // that all upstream rust dependencies were available in an rlib format.
1584 assert!(!are_upstream_rust_objects_already_included(sess));
1586 // Just need to tell the linker about where the library lives and
1588 let parent = cratepath.parent();
1589 if let Some(dir) = parent {
1590 cmd.include_path(&fix_windows_verbatim_for_gcc(dir));
1592 let filestem = cratepath.file_stem().unwrap().to_str().unwrap();
1593 cmd.link_rust_dylib(&unlib(&sess.target, filestem),
1594 parent.unwrap_or(Path::new("")));
1598 // Link in all of our upstream crates' native dependencies. Remember that
1599 // all of these upstream native dependencies are all non-static
1600 // dependencies. We've got two cases then:
1602 // 1. The upstream crate is an rlib. In this case we *must* link in the
1603 // native dependency because the rlib is just an archive.
1605 // 2. The upstream crate is a dylib. In order to use the dylib, we have to
1606 // have the dependency present on the system somewhere. Thus, we don't
1607 // gain a whole lot from not linking in the dynamic dependency to this
1610 // The use case for this is a little subtle. In theory the native
1611 // dependencies of a crate are purely an implementation detail of the crate
1612 // itself, but the problem arises with generic and inlined functions. If a
1613 // generic function calls a native function, then the generic function must
1614 // be instantiated in the target crate, meaning that the native symbol must
1615 // also be resolved in the target crate.
1616 fn add_upstream_native_libraries(cmd: &mut dyn Linker,
1618 codegen_results: &CodegenResults,
1619 crate_type: config::CrateType) {
1620 // Be sure to use a topological sorting of crates because there may be
1621 // interdependencies between native libraries. When passing -nodefaultlibs,
1622 // for example, almost all native libraries depend on libc, so we have to
1623 // make sure that's all the way at the right (liblibc is near the base of
1624 // the dependency chain).
1626 // This passes RequireStatic, but the actual requirement doesn't matter,
1627 // we're just getting an ordering of crate numbers, we're not worried about
1629 let formats = sess.dependency_formats.borrow();
1630 let data = formats.get(&crate_type).unwrap();
1632 let crates = &codegen_results.crate_info.used_crates_static;
1633 for &(cnum, _) in crates {
1634 for lib in codegen_results.crate_info.native_libraries[&cnum].iter() {
1635 let name = match lib.name {
1639 if !relevant_lib(sess, &lib) {
1643 NativeLibraryKind::NativeUnknown => cmd.link_dylib(&name.as_str()),
1644 NativeLibraryKind::NativeFramework => cmd.link_framework(&name.as_str()),
1645 NativeLibraryKind::NativeStaticNobundle => {
1646 // Link "static-nobundle" native libs only if the crate they originate from
1647 // is being linked statically to the current crate. If it's linked dynamically
1648 // or is an rlib already included via some other dylib crate, the symbols from
1649 // native libs will have already been included in that dylib.
1650 if data[cnum.as_usize() - 1] == Linkage::Static {
1651 cmd.link_staticlib(&name.as_str())
1654 // ignore statically included native libraries here as we've
1655 // already included them when we included the rust library
1657 NativeLibraryKind::NativeStatic => {}
1663 fn relevant_lib(sess: &Session, lib: &NativeLibrary) -> bool {
1665 Some(ref cfg) => attr::cfg_matches(cfg, &sess.parse_sess, None),
1670 fn are_upstream_rust_objects_already_included(sess: &Session) -> bool {
1675 // If we defer LTO to the linker, we haven't run LTO ourselves, so
1676 // any upstream object files have not been copied yet.
1677 !sess.opts.debugging_opts.cross_lang_lto.enabled()
1680 Lto::ThinLocal => false,