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 super::archive::{ArchiveBuilder, ArchiveConfig};
12 use super::bytecode::RLIB_BYTECODE_EXTENSION;
13 use super::linker::Linker;
14 use super::command::Command;
15 use super::rpath::RPathConfig;
17 use metadata::METADATA_FILENAME;
18 use rustc::session::config::{self, NoDebugInfo, OutputFilenames, OutputType, PrintRequest};
19 use rustc::session::config::{RUST_CGU_EXT, Lto};
20 use rustc::session::filesearch;
21 use rustc::session::search_paths::PathKind;
22 use rustc::session::Session;
23 use rustc::middle::cstore::{NativeLibrary, LibSource, NativeLibraryKind};
24 use rustc::middle::dependency_format::Linkage;
25 use {CrateTranslation, CrateInfo};
26 use rustc::util::common::time;
27 use rustc::util::fs::fix_windows_verbatim_for_gcc;
28 use rustc::hir::def_id::CrateNum;
30 use rustc_back::{PanicStrategy, RelroLevel, LinkerFlavor};
31 use context::get_reloc_model;
37 use std::ffi::OsString;
41 use std::path::{Path, PathBuf};
42 use std::process::{Output, Stdio};
46 /// The LLVM module name containing crate-metadata. This includes a `.` on
47 /// purpose, so it cannot clash with the name of a user-defined module.
48 pub const METADATA_MODULE_NAME: &'static str = "crate.metadata";
50 // same as for metadata above, but for allocator shim
51 pub const ALLOCATOR_MODULE_NAME: &'static str = "crate.allocator";
53 pub use rustc_trans_utils::link::{find_crate_name, filename_for_input, default_output_for_target,
54 invalid_output_for_target, build_link_meta, out_filename,
55 check_file_is_writeable};
57 // The third parameter is for env vars, used on windows to set up the
58 // path for MSVC to find its DLLs, and gcc to find its bundled
60 pub fn get_linker(sess: &Session) -> (PathBuf, Command, Vec<(OsString, OsString)>) {
61 let envs = vec![("PATH".into(), command_path(sess))];
63 // If our linker looks like a batch script on Windows then to execute this
64 // we'll need to spawn `cmd` explicitly. This is primarily done to handle
65 // emscripten where the linker is `emcc.bat` and needs to be spawned as
66 // `cmd /c emcc.bat ...`.
68 // This worked historically but is needed manually since #42436 (regression
69 // was tagged as #42791) and some more info can be found on #44443 for
71 let cmd = |linker: &Path| {
72 if let Some(linker) = linker.to_str() {
73 if cfg!(windows) && linker.ends_with(".bat") {
74 return Command::bat_script(linker)
80 if let Some(ref linker) = sess.opts.cg.linker {
81 (linker.clone(), cmd(linker), envs)
82 } else if sess.target.target.options.is_like_msvc {
83 let (cmd, envs) = msvc_link_exe_cmd(sess);
84 (PathBuf::from("link.exe"), cmd, envs)
86 let linker = PathBuf::from(&sess.target.target.options.linker);
87 let cmd = cmd(&linker);
93 pub fn msvc_link_exe_cmd(sess: &Session) -> (Command, Vec<(OsString, OsString)>) {
94 use cc::windows_registry;
96 let target = &sess.opts.target_triple;
97 let tool = windows_registry::find_tool(target, "link.exe");
99 if let Some(tool) = tool {
100 let mut cmd = Command::new(tool.path());
101 cmd.args(tool.args());
102 for &(ref k, ref v) in tool.env() {
105 let envs = tool.env().to_vec();
108 debug!("Failed to locate linker.");
109 (Command::new("link.exe"), vec![])
114 pub fn msvc_link_exe_cmd(_sess: &Session) -> (Command, Vec<(OsString, OsString)>) {
115 (Command::new("link.exe"), vec![])
118 fn command_path(sess: &Session) -> OsString {
119 // The compiler's sysroot often has some bundled tools, so add it to the
120 // PATH for the child.
121 let mut new_path = sess.host_filesearch(PathKind::All)
122 .get_tools_search_paths();
123 if let Some(path) = env::var_os("PATH") {
124 new_path.extend(env::split_paths(&path));
126 env::join_paths(new_path).unwrap()
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 for obj in trans.modules.iter().filter_map(|m| m.object.as_ref()) {
174 for obj in trans.modules.iter().filter_map(|m| m.bytecode_compressed.as_ref()) {
177 if let Some(ref obj) = trans.metadata_module.object {
180 if let Some(ref allocator) = trans.allocator_module {
181 if let Some(ref obj) = allocator.object {
184 if let Some(ref bc) = allocator.bytecode_compressed {
193 fn filename_for_metadata(sess: &Session, crate_name: &str, outputs: &OutputFilenames) -> PathBuf {
194 let out_filename = outputs.single_output_file.clone()
197 .join(&format!("lib{}{}.rmeta", crate_name, sess.opts.cg.extra_filename)));
198 check_file_is_writeable(&out_filename, sess);
202 pub(crate) fn each_linked_rlib(sess: &Session,
204 f: &mut FnMut(CrateNum, &Path)) -> Result<(), String> {
205 let crates = info.used_crates_static.iter();
206 let fmts = sess.dependency_formats.borrow();
207 let fmts = fmts.get(&config::CrateTypeExecutable)
208 .or_else(|| fmts.get(&config::CrateTypeStaticlib))
209 .or_else(|| fmts.get(&config::CrateTypeCdylib))
210 .or_else(|| fmts.get(&config::CrateTypeProcMacro));
211 let fmts = match fmts {
213 None => return Err(format!("could not find formats for rlibs"))
215 for &(cnum, ref path) in crates {
216 match fmts.get(cnum.as_usize() - 1) {
217 Some(&Linkage::NotLinked) |
218 Some(&Linkage::IncludedFromDylib) => continue,
220 None => return Err(format!("could not find formats for rlibs"))
222 let name = &info.crate_name[&cnum];
223 let path = match *path {
224 LibSource::Some(ref p) => p,
225 LibSource::MetadataOnly => {
226 return Err(format!("could not find rlib for: `{}`, found rmeta (metadata) file",
230 return Err(format!("could not find rlib for: `{}`", name))
238 /// Returns a boolean indicating whether the specified crate should be ignored
241 /// Crates ignored during LTO are not lumped together in the "massive object
242 /// file" that we create and are linked in their normal rlib states. See
243 /// comments below for what crates do not participate in LTO.
245 /// It's unusual for a crate to not participate in LTO. Typically only
246 /// compiler-specific and unstable crates have a reason to not participate in
248 pub(crate) fn ignored_for_lto(sess: &Session, info: &CrateInfo, cnum: CrateNum) -> bool {
249 // If our target enables builtin function lowering in LLVM then the
250 // crates providing these functions don't participate in LTO (e.g.
251 // no_builtins or compiler builtins crates).
252 !sess.target.target.options.no_builtins &&
253 (info.is_no_builtins.contains(&cnum) || info.compiler_builtins == Some(cnum))
256 fn link_binary_output(sess: &Session,
257 trans: &CrateTranslation,
258 crate_type: config::CrateType,
259 outputs: &OutputFilenames,
260 crate_name: &str) -> Vec<PathBuf> {
261 for obj in trans.modules.iter().filter_map(|m| m.object.as_ref()) {
262 check_file_is_writeable(obj, sess);
265 let mut out_filenames = vec![];
267 if outputs.outputs.contains_key(&OutputType::Metadata) {
268 let out_filename = filename_for_metadata(sess, crate_name, outputs);
269 // To avoid races with another rustc process scanning the output directory,
270 // we need to write the file somewhere else and atomically move it to its
271 // final destination, with a `fs::rename` call. In order for the rename to
272 // always succeed, the temporary file needs to be on the same filesystem,
273 // which is why we create it inside the output directory specifically.
274 let metadata_tmpdir = match TempDir::new_in(out_filename.parent().unwrap(), "rmeta") {
275 Ok(tmpdir) => tmpdir,
276 Err(err) => sess.fatal(&format!("couldn't create a temp dir: {}", err)),
278 let metadata = emit_metadata(sess, trans, &metadata_tmpdir);
279 if let Err(e) = fs::rename(metadata, &out_filename) {
280 sess.fatal(&format!("failed to write {}: {}", out_filename.display(), e));
282 out_filenames.push(out_filename);
285 let tmpdir = match TempDir::new("rustc") {
286 Ok(tmpdir) => tmpdir,
287 Err(err) => sess.fatal(&format!("couldn't create a temp dir: {}", err)),
290 if outputs.outputs.should_trans() {
291 let out_filename = out_filename(sess, crate_type, outputs, crate_name);
293 config::CrateTypeRlib => {
300 config::CrateTypeStaticlib => {
301 link_staticlib(sess, trans, &out_filename, &tmpdir);
304 link_natively(sess, crate_type, &out_filename, trans, tmpdir.path());
307 out_filenames.push(out_filename);
310 if sess.opts.cg.save_temps {
311 let _ = tmpdir.into_path();
317 fn archive_search_paths(sess: &Session) -> Vec<PathBuf> {
318 let mut search = Vec::new();
319 sess.target_filesearch(PathKind::Native).for_each_lib_search_path(|path, _| {
320 search.push(path.to_path_buf());
325 fn archive_config<'a>(sess: &'a Session,
327 input: Option<&Path>) -> ArchiveConfig<'a> {
330 dst: output.to_path_buf(),
331 src: input.map(|p| p.to_path_buf()),
332 lib_search_paths: archive_search_paths(sess),
336 /// We use a temp directory here to avoid races between concurrent rustc processes,
337 /// such as builds in the same directory using the same filename for metadata while
338 /// building an `.rlib` (stomping over one another), or writing an `.rmeta` into a
339 /// directory being searched for `extern crate` (observing an incomplete file).
340 /// The returned path is the temporary file containing the complete metadata.
341 fn emit_metadata<'a>(sess: &'a Session, trans: &CrateTranslation, tmpdir: &TempDir)
343 let out_filename = tmpdir.path().join(METADATA_FILENAME);
344 let result = fs::write(&out_filename, &trans.metadata.raw_data);
346 if let Err(e) = result {
347 sess.fatal(&format!("failed to write {}: {}", out_filename.display(), e));
360 // An rlib in its current incarnation is essentially a renamed .a file. The
361 // rlib primarily contains the object file of the crate, but it also contains
362 // all of the object files from native libraries. This is done by unzipping
363 // native libraries and inserting all of the contents into this archive.
364 fn link_rlib<'a>(sess: &'a Session,
365 trans: &CrateTranslation,
368 tmpdir: &TempDir) -> ArchiveBuilder<'a> {
369 info!("preparing rlib to {:?}", out_filename);
370 let mut ab = ArchiveBuilder::new(archive_config(sess, out_filename, None));
372 for obj in trans.modules.iter().filter_map(|m| m.object.as_ref()) {
376 // Note that in this loop we are ignoring the value of `lib.cfg`. That is,
377 // we may not be configured to actually include a static library if we're
378 // adding it here. That's because later when we consume this rlib we'll
379 // decide whether we actually needed the static library or not.
381 // To do this "correctly" we'd need to keep track of which libraries added
382 // which object files to the archive. We don't do that here, however. The
383 // #[link(cfg(..))] feature is unstable, though, and only intended to get
384 // liblibc working. In that sense the check below just indicates that if
385 // there are any libraries we want to omit object files for at link time we
386 // just exclude all custom object files.
388 // Eventually if we want to stabilize or flesh out the #[link(cfg(..))]
389 // feature then we'll need to figure out how to record what objects were
390 // loaded from the libraries found here and then encode that into the
391 // metadata of the rlib we're generating somehow.
392 for lib in trans.crate_info.used_libraries.iter() {
394 NativeLibraryKind::NativeStatic => {}
395 NativeLibraryKind::NativeStaticNobundle |
396 NativeLibraryKind::NativeFramework |
397 NativeLibraryKind::NativeUnknown => continue,
399 ab.add_native_library(&lib.name.as_str());
402 // After adding all files to the archive, we need to update the
403 // symbol table of the archive.
406 // Note that it is important that we add all of our non-object "magical
407 // files" *after* all of the object files in the archive. The reason for
408 // this is as follows:
410 // * When performing LTO, this archive will be modified to remove
411 // objects from above. The reason for this is described below.
413 // * When the system linker looks at an archive, it will attempt to
414 // determine the architecture of the archive in order to see whether its
417 // The algorithm for this detection is: iterate over the files in the
418 // archive. Skip magical SYMDEF names. Interpret the first file as an
419 // object file. Read architecture from the object file.
421 // * As one can probably see, if "metadata" and "foo.bc" were placed
422 // before all of the objects, then the architecture of this archive would
423 // not be correctly inferred once 'foo.o' is removed.
425 // Basically, all this means is that this code should not move above the
428 RlibFlavor::Normal => {
429 // Instead of putting the metadata in an object file section, rlibs
430 // contain the metadata in a separate file.
431 ab.add_file(&emit_metadata(sess, trans, tmpdir));
433 // For LTO purposes, the bytecode of this library is also inserted
435 for bytecode in trans.modules.iter().filter_map(|m| m.bytecode_compressed.as_ref()) {
436 ab.add_file(bytecode);
439 // After adding all files to the archive, we need to update the
440 // symbol table of the archive. This currently dies on macOS (see
441 // #11162), and isn't necessary there anyway
442 if !sess.target.target.options.is_like_osx {
447 RlibFlavor::StaticlibBase => {
448 let obj = trans.allocator_module
450 .and_then(|m| m.object.as_ref());
451 if let Some(obj) = obj {
460 // Create a static archive
462 // This is essentially the same thing as an rlib, but it also involves adding
463 // all of the upstream crates' objects into the archive. This will slurp in
464 // all of the native libraries of upstream dependencies as well.
466 // Additionally, there's no way for us to link dynamic libraries, so we warn
467 // about all dynamic library dependencies that they're not linked in.
469 // There's no need to include metadata in a static archive, so ensure to not
470 // link in the metadata object file (and also don't prepare the archive with a
472 fn link_staticlib(sess: &Session,
473 trans: &CrateTranslation,
476 let mut ab = link_rlib(sess,
478 RlibFlavor::StaticlibBase,
481 let mut all_native_libs = vec![];
483 let res = each_linked_rlib(sess, &trans.crate_info, &mut |cnum, path| {
484 let name = &trans.crate_info.crate_name[&cnum];
485 let native_libs = &trans.crate_info.native_libraries[&cnum];
487 // Here when we include the rlib into our staticlib we need to make a
488 // decision whether to include the extra object files along the way.
489 // These extra object files come from statically included native
490 // libraries, but they may be cfg'd away with #[link(cfg(..))].
492 // This unstable feature, though, only needs liblibc to work. The only
493 // use case there is where musl is statically included in liblibc.rlib,
494 // so if we don't want the included version we just need to skip it. As
495 // a result the logic here is that if *any* linked library is cfg'd away
496 // we just skip all object files.
498 // Clearly this is not sufficient for a general purpose feature, and
499 // we'd want to read from the library's metadata to determine which
500 // object files come from where and selectively skip them.
501 let skip_object_files = native_libs.iter().any(|lib| {
502 lib.kind == NativeLibraryKind::NativeStatic && !relevant_lib(sess, lib)
506 is_full_lto_enabled(sess) &&
507 !ignored_for_lto(sess, &trans.crate_info, cnum),
508 skip_object_files).unwrap();
510 all_native_libs.extend(trans.crate_info.native_libraries[&cnum].iter().cloned());
512 if let Err(e) = res {
519 if !all_native_libs.is_empty() {
520 if sess.opts.prints.contains(&PrintRequest::NativeStaticLibs) {
521 print_native_static_libs(sess, &all_native_libs);
526 fn print_native_static_libs(sess: &Session, all_native_libs: &[NativeLibrary]) {
527 let lib_args: Vec<_> = all_native_libs.iter()
528 .filter(|l| relevant_lib(sess, l))
529 .filter_map(|lib| match lib.kind {
530 NativeLibraryKind::NativeStaticNobundle |
531 NativeLibraryKind::NativeUnknown => {
532 if sess.target.target.options.is_like_msvc {
533 Some(format!("{}.lib", lib.name))
535 Some(format!("-l{}", lib.name))
538 NativeLibraryKind::NativeFramework => {
539 // ld-only syntax, since there are no frameworks in MSVC
540 Some(format!("-framework {}", lib.name))
542 // These are included, no need to print them
543 NativeLibraryKind::NativeStatic => None,
546 if !lib_args.is_empty() {
547 sess.note_without_error("Link against the following native artifacts when linking \
548 against this static library. The order and any duplication \
549 can be significant on some platforms.");
550 // Prefix for greppability
551 sess.note_without_error(&format!("native-static-libs: {}", &lib_args.join(" ")));
555 // Create a dynamic library or executable
557 // This will invoke the system linker/cc to create the resulting file. This
558 // links to all upstream files as well.
559 fn link_natively(sess: &Session,
560 crate_type: config::CrateType,
562 trans: &CrateTranslation,
564 info!("preparing {:?} to {:?}", crate_type, out_filename);
565 let flavor = sess.linker_flavor();
567 // The "binaryen linker" is massively special, so skip everything below.
568 if flavor == LinkerFlavor::Binaryen {
569 return link_binaryen(sess, crate_type, out_filename, trans, tmpdir);
572 // The invocations of cc share some flags across platforms
573 let (pname, mut cmd, envs) = get_linker(sess);
574 // This will set PATH on windows
577 let root = sess.target_filesearch(PathKind::Native).get_lib_path();
578 if let Some(args) = sess.target.target.options.pre_link_args.get(&flavor) {
581 if let Some(ref args) = sess.opts.debugging_opts.pre_link_args {
584 cmd.args(&sess.opts.debugging_opts.pre_link_arg);
586 let pre_link_objects = if crate_type == config::CrateTypeExecutable {
587 &sess.target.target.options.pre_link_objects_exe
589 &sess.target.target.options.pre_link_objects_dll
591 for obj in pre_link_objects {
592 cmd.arg(root.join(obj));
595 if sess.target.target.options.is_like_emscripten {
597 cmd.arg(if sess.panic_strategy() == PanicStrategy::Abort {
598 "DISABLE_EXCEPTION_CATCHING=1"
600 "DISABLE_EXCEPTION_CATCHING=0"
605 let mut linker = trans.linker_info.to_linker(cmd, &sess);
606 link_args(&mut *linker, sess, crate_type, tmpdir,
607 out_filename, trans);
608 cmd = linker.finalize();
610 if let Some(args) = sess.target.target.options.late_link_args.get(&flavor) {
613 for obj in &sess.target.target.options.post_link_objects {
614 cmd.arg(root.join(obj));
616 if let Some(args) = sess.target.target.options.post_link_args.get(&flavor) {
619 for &(ref k, ref v) in &sess.target.target.options.link_env {
623 if sess.opts.debugging_opts.print_link_args {
624 println!("{:?}", &cmd);
627 // May have not found libraries in the right formats.
628 sess.abort_if_errors();
630 // Invoke the system linker
632 // Note that there's a terribly awful hack that really shouldn't be present
633 // in any compiler. Here an environment variable is supported to
634 // automatically retry the linker invocation if the linker looks like it
637 // Gee that seems odd, normally segfaults are things we want to know about!
638 // Unfortunately though in rust-lang/rust#38878 we're experiencing the
639 // linker segfaulting on Travis quite a bit which is causing quite a bit of
640 // pain to land PRs when they spuriously fail due to a segfault.
642 // The issue #38878 has some more debugging information on it as well, but
643 // this unfortunately looks like it's just a race condition in macOS's linker
644 // with some thread pool working in the background. It seems that no one
645 // currently knows a fix for this so in the meantime we're left with this...
647 let retry_on_segfault = env::var("RUSTC_RETRY_LINKER_ON_SEGFAULT").is_ok();
652 prog = time(sess.time_passes(), "running linker", || {
653 exec_linker(sess, &mut cmd, tmpdir)
655 if !retry_on_segfault || i > 3 {
658 let output = match prog {
659 Ok(ref output) => output,
662 if output.status.success() {
665 let mut out = output.stderr.clone();
666 out.extend(&output.stdout);
667 let out = String::from_utf8_lossy(&out);
668 let msg_segv = "clang: error: unable to execute command: Segmentation fault: 11";
669 let msg_bus = "clang: error: unable to execute command: Bus error: 10";
670 if !(out.contains(msg_segv) || out.contains(msg_bus)) {
675 "looks like the linker segfaulted when we tried to call it, \
676 automatically retrying again. cmd = {:?}, out = {}.",
684 fn escape_string(s: &[u8]) -> String {
685 str::from_utf8(s).map(|s| s.to_owned())
686 .unwrap_or_else(|_| {
687 let mut x = "Non-UTF-8 output: ".to_string();
689 .flat_map(|&b| ascii::escape_default(b))
690 .map(|b| char::from_u32(b as u32).unwrap()));
694 if !prog.status.success() {
695 let mut output = prog.stderr.clone();
696 output.extend_from_slice(&prog.stdout);
697 sess.struct_err(&format!("linking with `{}` failed: {}",
700 .note(&format!("{:?}", &cmd))
701 .note(&escape_string(&output))
703 sess.abort_if_errors();
705 info!("linker stderr:\n{}", escape_string(&prog.stderr));
706 info!("linker stdout:\n{}", escape_string(&prog.stdout));
709 let linker_not_found = e.kind() == io::ErrorKind::NotFound;
711 let mut linker_error = {
712 if linker_not_found {
713 sess.struct_err(&format!("linker `{}` not found", pname.display()))
715 sess.struct_err(&format!("could not exec the linker `{}`", pname.display()))
719 linker_error.note(&format!("{}", e));
721 if !linker_not_found {
722 linker_error.note(&format!("{:?}", &cmd));
727 if sess.target.target.options.is_like_msvc && linker_not_found {
728 sess.note_without_error("the msvc targets depend on the msvc linker \
729 but `link.exe` was not found");
730 sess.note_without_error("please ensure that VS 2013 or VS 2015 was installed \
731 with the Visual C++ option");
733 sess.abort_if_errors();
738 // On macOS, debuggers need this utility to get run to do some munging of
740 if sess.target.target.options.is_like_osx && sess.opts.debuginfo != NoDebugInfo {
741 match Command::new("dsymutil").arg(out_filename).output() {
743 Err(e) => sess.fatal(&format!("failed to run dsymutil: {}", e)),
748 fn exec_linker(sess: &Session, cmd: &mut Command, tmpdir: &Path)
749 -> io::Result<Output>
751 // When attempting to spawn the linker we run a risk of blowing out the
752 // size limits for spawning a new process with respect to the arguments
753 // we pass on the command line.
755 // Here we attempt to handle errors from the OS saying "your list of
756 // arguments is too big" by reinvoking the linker again with an `@`-file
757 // that contains all the arguments. The theory is that this is then
758 // accepted on all linkers and the linker will read all its options out of
759 // there instead of looking at the command line.
760 if !cmd.very_likely_to_exceed_some_spawn_limit() {
761 match cmd.command().stdout(Stdio::piped()).stderr(Stdio::piped()).spawn() {
762 Ok(child) => return child.wait_with_output(),
763 Err(ref e) if command_line_too_big(e) => {}
764 Err(e) => return Err(e)
768 let mut cmd2 = cmd.clone();
769 let mut args = String::new();
770 for arg in cmd2.take_args() {
771 args.push_str(&Escape {
772 arg: arg.to_str().unwrap(),
773 is_like_msvc: sess.target.target.options.is_like_msvc,
777 let file = tmpdir.join("linker-arguments");
778 fs::write(&file, args.as_bytes())?;
779 cmd2.arg(format!("@{}", file.display()));
780 return cmd2.output();
783 fn command_line_too_big(err: &io::Error) -> bool {
784 err.raw_os_error() == Some(::libc::E2BIG)
788 fn command_line_too_big(err: &io::Error) -> bool {
789 const ERROR_FILENAME_EXCED_RANGE: i32 = 206;
790 err.raw_os_error() == Some(ERROR_FILENAME_EXCED_RANGE)
798 impl<'a> fmt::Display for Escape<'a> {
799 fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
800 if self.is_like_msvc {
801 // This is "documented" at
802 // https://msdn.microsoft.com/en-us/library/4xdcbak7.aspx
804 // Unfortunately there's not a great specification of the
805 // syntax I could find online (at least) but some local
806 // testing showed that this seemed sufficient-ish to catch
807 // at least a few edge cases.
809 for c in self.arg.chars() {
811 '"' => write!(f, "\\{}", c)?,
812 c => write!(f, "{}", c)?,
817 // This is documented at https://linux.die.net/man/1/ld, namely:
819 // > Options in file are separated by whitespace. A whitespace
820 // > character may be included in an option by surrounding the
821 // > entire option in either single or double quotes. Any
822 // > character (including a backslash) may be included by
823 // > prefixing the character to be included with a backslash.
825 // We put an argument on each line, so all we need to do is
826 // ensure the line is interpreted as one whole argument.
827 for c in self.arg.chars() {
830 ' ' => write!(f, "\\{}", c)?,
831 c => write!(f, "{}", c)?,
840 fn link_args(cmd: &mut Linker,
842 crate_type: config::CrateType,
845 trans: &CrateTranslation) {
847 // The default library location, we need this to find the runtime.
848 // The location of crates will be determined as needed.
849 let lib_path = sess.target_filesearch(PathKind::All).get_lib_path();
852 let t = &sess.target.target;
854 cmd.include_path(&fix_windows_verbatim_for_gcc(&lib_path));
855 for obj in trans.modules.iter().filter_map(|m| m.object.as_ref()) {
858 cmd.output_filename(out_filename);
860 if crate_type == config::CrateTypeExecutable &&
861 sess.target.target.options.is_like_windows {
862 if let Some(ref s) = trans.windows_subsystem {
867 // If we're building a dynamic library then some platforms need to make sure
868 // that all symbols are exported correctly from the dynamic library.
869 if crate_type != config::CrateTypeExecutable ||
870 sess.target.target.options.is_like_emscripten {
871 cmd.export_symbols(tmpdir, crate_type);
874 // When linking a dynamic library, we put the metadata into a section of the
875 // executable. This metadata is in a separate object file from the main
876 // object file, so we link that in here.
877 if crate_type == config::CrateTypeDylib ||
878 crate_type == config::CrateTypeProcMacro {
879 if let Some(obj) = trans.metadata_module.object.as_ref() {
884 let obj = trans.allocator_module
886 .and_then(|m| m.object.as_ref());
887 if let Some(obj) = obj {
891 // Try to strip as much out of the generated object by removing unused
892 // sections if possible. See more comments in linker.rs
893 if !sess.opts.cg.link_dead_code {
894 let keep_metadata = crate_type == config::CrateTypeDylib;
895 cmd.gc_sections(keep_metadata);
898 let used_link_args = &trans.crate_info.link_args;
900 if crate_type == config::CrateTypeExecutable &&
901 t.options.position_independent_executables {
902 let empty_vec = Vec::new();
903 let args = sess.opts.cg.link_args.as_ref().unwrap_or(&empty_vec);
904 let more_args = &sess.opts.cg.link_arg;
905 let mut args = args.iter().chain(more_args.iter()).chain(used_link_args.iter());
907 if get_reloc_model(sess) == llvm::RelocMode::PIC
908 && !sess.crt_static() && !args.any(|x| *x == "-static") {
909 cmd.position_independent_executable();
913 let relro_level = match sess.opts.debugging_opts.relro_level {
914 Some(level) => level,
915 None => t.options.relro_level,
918 RelroLevel::Full => {
921 RelroLevel::Partial => {
924 RelroLevel::Off => {},
927 // Pass optimization flags down to the linker.
930 // Pass debuginfo flags down to the linker.
933 // We want to prevent the compiler from accidentally leaking in any system
934 // libraries, so we explicitly ask gcc to not link to any libraries by
935 // default. Note that this does not happen for windows because windows pulls
936 // in some large number of libraries and I couldn't quite figure out which
938 if t.options.no_default_libraries {
939 cmd.no_default_libraries();
942 // Take careful note of the ordering of the arguments we pass to the linker
943 // here. Linkers will assume that things on the left depend on things to the
944 // right. Things on the right cannot depend on things on the left. This is
945 // all formally implemented in terms of resolving symbols (libs on the right
946 // resolve unknown symbols of libs on the left, but not vice versa).
948 // For this reason, we have organized the arguments we pass to the linker as
951 // 1. The local object that LLVM just generated
952 // 2. Local native libraries
953 // 3. Upstream rust libraries
954 // 4. Upstream native libraries
956 // The rationale behind this ordering is that those items lower down in the
957 // list can't depend on items higher up in the list. For example nothing can
958 // depend on what we just generated (e.g. that'd be a circular dependency).
959 // Upstream rust libraries are not allowed to depend on our local native
960 // libraries as that would violate the structure of the DAG, in that
961 // scenario they are required to link to them as well in a shared fashion.
963 // Note that upstream rust libraries may contain native dependencies as
964 // well, but they also can't depend on what we just started to add to the
965 // link line. And finally upstream native libraries can't depend on anything
966 // in this DAG so far because they're only dylibs and dylibs can only depend
967 // on other dylibs (e.g. other native deps).
968 add_local_native_libraries(cmd, sess, trans);
969 add_upstream_rust_crates(cmd, sess, trans, crate_type, tmpdir);
970 add_upstream_native_libraries(cmd, sess, trans, crate_type);
972 // Tell the linker what we're doing.
973 if crate_type != config::CrateTypeExecutable {
974 cmd.build_dylib(out_filename);
976 if crate_type == config::CrateTypeExecutable && sess.crt_static() {
977 cmd.build_static_executable();
980 // FIXME (#2397): At some point we want to rpath our guesses as to
981 // where extern libraries might live, based on the
982 // addl_lib_search_paths
983 if sess.opts.cg.rpath {
984 let sysroot = sess.sysroot();
985 let target_triple = &sess.opts.target_triple;
986 let mut get_install_prefix_lib_path = || {
987 let install_prefix = option_env!("CFG_PREFIX").expect("CFG_PREFIX");
988 let tlib = filesearch::relative_target_lib_path(sysroot, target_triple);
989 let mut path = PathBuf::from(install_prefix);
994 let mut rpath_config = RPathConfig {
995 used_crates: &trans.crate_info.used_crates_dynamic,
996 out_filename: out_filename.to_path_buf(),
997 has_rpath: sess.target.target.options.has_rpath,
998 is_like_osx: sess.target.target.options.is_like_osx,
999 linker_is_gnu: sess.target.target.options.linker_is_gnu,
1000 get_install_prefix_lib_path: &mut get_install_prefix_lib_path,
1002 cmd.args(&rpath::get_rpath_flags(&mut rpath_config));
1005 // Finally add all the linker arguments provided on the command line along
1006 // with any #[link_args] attributes found inside the crate
1007 if let Some(ref args) = sess.opts.cg.link_args {
1010 cmd.args(&sess.opts.cg.link_arg);
1011 cmd.args(&used_link_args);
1014 // # Native library linking
1016 // User-supplied library search paths (-L on the command line). These are
1017 // the same paths used to find Rust crates, so some of them may have been
1018 // added already by the previous crate linking code. This only allows them
1019 // to be found at compile time so it is still entirely up to outside
1020 // forces to make sure that library can be found at runtime.
1022 // Also note that the native libraries linked here are only the ones located
1023 // in the current crate. Upstream crates with native library dependencies
1024 // may have their native library pulled in above.
1025 fn add_local_native_libraries(cmd: &mut Linker,
1027 trans: &CrateTranslation) {
1028 sess.target_filesearch(PathKind::All).for_each_lib_search_path(|path, k| {
1030 PathKind::Framework => { cmd.framework_path(path); }
1031 _ => { cmd.include_path(&fix_windows_verbatim_for_gcc(path)); }
1035 let relevant_libs = trans.crate_info.used_libraries.iter().filter(|l| {
1036 relevant_lib(sess, l)
1039 let search_path = archive_search_paths(sess);
1040 for lib in relevant_libs {
1042 NativeLibraryKind::NativeUnknown => cmd.link_dylib(&lib.name.as_str()),
1043 NativeLibraryKind::NativeFramework => cmd.link_framework(&lib.name.as_str()),
1044 NativeLibraryKind::NativeStaticNobundle => cmd.link_staticlib(&lib.name.as_str()),
1045 NativeLibraryKind::NativeStatic => cmd.link_whole_staticlib(&lib.name.as_str(),
1051 // # Rust Crate linking
1053 // Rust crates are not considered at all when creating an rlib output. All
1054 // dependencies will be linked when producing the final output (instead of
1055 // the intermediate rlib version)
1056 fn add_upstream_rust_crates(cmd: &mut Linker,
1058 trans: &CrateTranslation,
1059 crate_type: config::CrateType,
1061 // All of the heavy lifting has previously been accomplished by the
1062 // dependency_format module of the compiler. This is just crawling the
1063 // output of that module, adding crates as necessary.
1065 // Linking to a rlib involves just passing it to the linker (the linker
1066 // will slurp up the object files inside), and linking to a dynamic library
1067 // involves just passing the right -l flag.
1069 let formats = sess.dependency_formats.borrow();
1070 let data = formats.get(&crate_type).unwrap();
1072 // Invoke get_used_crates to ensure that we get a topological sorting of
1074 let deps = &trans.crate_info.used_crates_dynamic;
1076 let mut compiler_builtins = None;
1078 for &(cnum, _) in deps.iter() {
1079 // We may not pass all crates through to the linker. Some crates may
1080 // appear statically in an existing dylib, meaning we'll pick up all the
1081 // symbols from the dylib.
1082 let src = &trans.crate_info.used_crate_source[&cnum];
1083 match data[cnum.as_usize() - 1] {
1084 _ if trans.crate_info.profiler_runtime == Some(cnum) => {
1085 add_static_crate(cmd, sess, trans, tmpdir, crate_type, cnum);
1087 _ if trans.crate_info.sanitizer_runtime == Some(cnum) => {
1088 link_sanitizer_runtime(cmd, sess, trans, tmpdir, cnum);
1090 // compiler-builtins are always placed last to ensure that they're
1091 // linked correctly.
1092 _ if trans.crate_info.compiler_builtins == Some(cnum) => {
1093 assert!(compiler_builtins.is_none());
1094 compiler_builtins = Some(cnum);
1096 Linkage::NotLinked |
1097 Linkage::IncludedFromDylib => {}
1098 Linkage::Static => {
1099 add_static_crate(cmd, sess, trans, tmpdir, crate_type, cnum);
1101 Linkage::Dynamic => {
1102 add_dynamic_crate(cmd, sess, &src.dylib.as_ref().unwrap().0)
1107 // compiler-builtins are always placed last to ensure that they're
1108 // linked correctly.
1109 // We must always link the `compiler_builtins` crate statically. Even if it
1110 // was already "included" in a dylib (e.g. `libstd` when `-C prefer-dynamic`
1112 if let Some(cnum) = compiler_builtins {
1113 add_static_crate(cmd, sess, trans, tmpdir, crate_type, cnum);
1116 // Converts a library file-stem into a cc -l argument
1117 fn unlib<'a>(config: &config::Config, stem: &'a str) -> &'a str {
1118 if stem.starts_with("lib") && !config.target.options.is_like_windows {
1125 // We must link the sanitizer runtime using -Wl,--whole-archive but since
1126 // it's packed in a .rlib, it contains stuff that are not objects that will
1127 // make the linker error. So we must remove those bits from the .rlib before
1129 fn link_sanitizer_runtime(cmd: &mut Linker,
1131 trans: &CrateTranslation,
1134 let src = &trans.crate_info.used_crate_source[&cnum];
1135 let cratepath = &src.rlib.as_ref().unwrap().0;
1137 if sess.target.target.options.is_like_osx {
1138 // On Apple platforms, the sanitizer is always built as a dylib, and
1139 // LLVM will link to `@rpath/*.dylib`, so we need to specify an
1140 // rpath to the library as well (the rpath should be absolute, see
1141 // PR #41352 for details).
1143 // FIXME: Remove this logic into librustc_*san once Cargo supports it
1144 let rpath = cratepath.parent().unwrap();
1145 let rpath = rpath.to_str().expect("non-utf8 component in path");
1146 cmd.args(&["-Wl,-rpath".into(), "-Xlinker".into(), rpath.into()]);
1149 let dst = tmpdir.join(cratepath.file_name().unwrap());
1150 let cfg = archive_config(sess, &dst, Some(cratepath));
1151 let mut archive = ArchiveBuilder::new(cfg);
1152 archive.update_symbols();
1154 for f in archive.src_files() {
1155 if f.ends_with(RLIB_BYTECODE_EXTENSION) || f == METADATA_FILENAME {
1156 archive.remove_file(&f);
1163 cmd.link_whole_rlib(&dst);
1166 // Adds the static "rlib" versions of all crates to the command line.
1167 // There's a bit of magic which happens here specifically related to LTO and
1168 // dynamic libraries. Specifically:
1170 // * For LTO, we remove upstream object files.
1171 // * For dylibs we remove metadata and bytecode from upstream rlibs
1173 // When performing LTO, almost(*) all of the bytecode from the upstream
1174 // libraries has already been included in our object file output. As a
1175 // result we need to remove the object files in the upstream libraries so
1176 // the linker doesn't try to include them twice (or whine about duplicate
1177 // symbols). We must continue to include the rest of the rlib, however, as
1178 // it may contain static native libraries which must be linked in.
1180 // (*) Crates marked with `#![no_builtins]` don't participate in LTO and
1181 // their bytecode wasn't included. The object files in those libraries must
1182 // still be passed to the linker.
1184 // When making a dynamic library, linkers by default don't include any
1185 // object files in an archive if they're not necessary to resolve the link.
1186 // We basically want to convert the archive (rlib) to a dylib, though, so we
1187 // *do* want everything included in the output, regardless of whether the
1188 // linker thinks it's needed or not. As a result we must use the
1189 // --whole-archive option (or the platform equivalent). When using this
1190 // option the linker will fail if there are non-objects in the archive (such
1191 // as our own metadata and/or bytecode). All in all, for rlibs to be
1192 // entirely included in dylibs, we need to remove all non-object files.
1194 // Note, however, that if we're not doing LTO or we're not producing a dylib
1195 // (aka we're making an executable), we can just pass the rlib blindly to
1196 // the linker (fast) because it's fine if it's not actually included as
1197 // we're at the end of the dependency chain.
1198 fn add_static_crate(cmd: &mut Linker,
1200 trans: &CrateTranslation,
1202 crate_type: config::CrateType,
1204 let src = &trans.crate_info.used_crate_source[&cnum];
1205 let cratepath = &src.rlib.as_ref().unwrap().0;
1207 // See the comment above in `link_staticlib` and `link_rlib` for why if
1208 // there's a static library that's not relevant we skip all object
1210 let native_libs = &trans.crate_info.native_libraries[&cnum];
1211 let skip_native = native_libs.iter().any(|lib| {
1212 lib.kind == NativeLibraryKind::NativeStatic && !relevant_lib(sess, lib)
1215 if (!is_full_lto_enabled(sess) ||
1216 ignored_for_lto(sess, &trans.crate_info, cnum)) &&
1217 crate_type != config::CrateTypeDylib &&
1219 cmd.link_rlib(&fix_windows_verbatim_for_gcc(cratepath));
1223 let dst = tmpdir.join(cratepath.file_name().unwrap());
1224 let name = cratepath.file_name().unwrap().to_str().unwrap();
1225 let name = &name[3..name.len() - 5]; // chop off lib/.rlib
1227 time(sess.time_passes(), &format!("altering {}.rlib", name), || {
1228 let cfg = archive_config(sess, &dst, Some(cratepath));
1229 let mut archive = ArchiveBuilder::new(cfg);
1230 archive.update_symbols();
1232 let mut any_objects = false;
1233 for f in archive.src_files() {
1234 if f.ends_with(RLIB_BYTECODE_EXTENSION) || f == METADATA_FILENAME {
1235 archive.remove_file(&f);
1239 let canonical = f.replace("-", "_");
1240 let canonical_name = name.replace("-", "_");
1242 // Look for `.rcgu.o` at the end of the filename to conclude
1243 // that this is a Rust-related object file.
1244 fn looks_like_rust(s: &str) -> bool {
1245 let path = Path::new(s);
1246 let ext = path.extension().and_then(|s| s.to_str());
1247 if ext != Some(OutputType::Object.extension()) {
1250 let ext2 = path.file_stem()
1251 .and_then(|s| Path::new(s).extension())
1252 .and_then(|s| s.to_str());
1253 ext2 == Some(RUST_CGU_EXT)
1256 let is_rust_object =
1257 canonical.starts_with(&canonical_name) &&
1258 looks_like_rust(&f);
1260 // If we've been requested to skip all native object files
1261 // (those not generated by the rust compiler) then we can skip
1262 // this file. See above for why we may want to do this.
1263 let skip_because_cfg_say_so = skip_native && !is_rust_object;
1265 // If we're performing LTO and this is a rust-generated object
1266 // file, then we don't need the object file as it's part of the
1267 // LTO module. Note that `#![no_builtins]` is excluded from LTO,
1268 // though, so we let that object file slide.
1269 let skip_because_lto = is_full_lto_enabled(sess) &&
1271 (sess.target.target.options.no_builtins ||
1272 !trans.crate_info.is_no_builtins.contains(&cnum));
1274 if skip_because_cfg_say_so || skip_because_lto {
1275 archive.remove_file(&f);
1286 // If we're creating a dylib, then we need to include the
1287 // whole of each object in our archive into that artifact. This is
1288 // because a `dylib` can be reused as an intermediate artifact.
1290 // Note, though, that we don't want to include the whole of a
1291 // compiler-builtins crate (e.g. compiler-rt) because it'll get
1292 // repeatedly linked anyway.
1293 if crate_type == config::CrateTypeDylib &&
1294 trans.crate_info.compiler_builtins != Some(cnum) {
1295 cmd.link_whole_rlib(&fix_windows_verbatim_for_gcc(&dst));
1297 cmd.link_rlib(&fix_windows_verbatim_for_gcc(&dst));
1302 // Same thing as above, but for dynamic crates instead of static crates.
1303 fn add_dynamic_crate(cmd: &mut Linker, sess: &Session, cratepath: &Path) {
1304 // If we're performing LTO, then it should have been previously required
1305 // that all upstream rust dependencies were available in an rlib format.
1306 assert!(!is_full_lto_enabled(sess));
1308 // Just need to tell the linker about where the library lives and
1310 let parent = cratepath.parent();
1311 if let Some(dir) = parent {
1312 cmd.include_path(&fix_windows_verbatim_for_gcc(dir));
1314 let filestem = cratepath.file_stem().unwrap().to_str().unwrap();
1315 cmd.link_rust_dylib(&unlib(&sess.target, filestem),
1316 parent.unwrap_or(Path::new("")));
1320 // Link in all of our upstream crates' native dependencies. Remember that
1321 // all of these upstream native dependencies are all non-static
1322 // dependencies. We've got two cases then:
1324 // 1. The upstream crate is an rlib. In this case we *must* link in the
1325 // native dependency because the rlib is just an archive.
1327 // 2. The upstream crate is a dylib. In order to use the dylib, we have to
1328 // have the dependency present on the system somewhere. Thus, we don't
1329 // gain a whole lot from not linking in the dynamic dependency to this
1332 // The use case for this is a little subtle. In theory the native
1333 // dependencies of a crate are purely an implementation detail of the crate
1334 // itself, but the problem arises with generic and inlined functions. If a
1335 // generic function calls a native function, then the generic function must
1336 // be instantiated in the target crate, meaning that the native symbol must
1337 // also be resolved in the target crate.
1338 fn add_upstream_native_libraries(cmd: &mut Linker,
1340 trans: &CrateTranslation,
1341 crate_type: config::CrateType) {
1342 // Be sure to use a topological sorting of crates because there may be
1343 // interdependencies between native libraries. When passing -nodefaultlibs,
1344 // for example, almost all native libraries depend on libc, so we have to
1345 // make sure that's all the way at the right (liblibc is near the base of
1346 // the dependency chain).
1348 // This passes RequireStatic, but the actual requirement doesn't matter,
1349 // we're just getting an ordering of crate numbers, we're not worried about
1351 let formats = sess.dependency_formats.borrow();
1352 let data = formats.get(&crate_type).unwrap();
1354 let crates = &trans.crate_info.used_crates_static;
1355 for &(cnum, _) in crates {
1356 for lib in trans.crate_info.native_libraries[&cnum].iter() {
1357 if !relevant_lib(sess, &lib) {
1361 NativeLibraryKind::NativeUnknown => cmd.link_dylib(&lib.name.as_str()),
1362 NativeLibraryKind::NativeFramework => cmd.link_framework(&lib.name.as_str()),
1363 NativeLibraryKind::NativeStaticNobundle => {
1364 // Link "static-nobundle" native libs only if the crate they originate from
1365 // is being linked statically to the current crate. If it's linked dynamically
1366 // or is an rlib already included via some other dylib crate, the symbols from
1367 // native libs will have already been included in that dylib.
1368 if data[cnum.as_usize() - 1] == Linkage::Static {
1369 cmd.link_staticlib(&lib.name.as_str())
1372 // ignore statically included native libraries here as we've
1373 // already included them when we included the rust library
1375 NativeLibraryKind::NativeStatic => {}
1381 fn relevant_lib(sess: &Session, lib: &NativeLibrary) -> bool {
1383 Some(ref cfg) => attr::cfg_matches(cfg, &sess.parse_sess, None),
1388 /// For now "linking with binaryen" is just "move the one module we generated in
1389 /// the backend to the final output"
1391 /// That is, all the heavy lifting happens during the `back::write` phase. Here
1392 /// we just clean up after that.
1394 /// Note that this is super temporary and "will not survive the night", this is
1395 /// guaranteed to get removed as soon as a linker for wasm exists. This should
1396 /// not be used for anything other than wasm.
1397 fn link_binaryen(sess: &Session,
1398 _crate_type: config::CrateType,
1399 out_filename: &Path,
1400 trans: &CrateTranslation,
1402 assert!(trans.allocator_module.is_none());
1403 assert_eq!(trans.modules.len(), 1);
1405 let object = trans.modules[0].object.as_ref().expect("object must exist");
1406 let res = fs::hard_link(object, out_filename)
1407 .or_else(|_| fs::copy(object, out_filename).map(|_| ()));
1408 if let Err(e) = res {
1409 sess.fatal(&format!("failed to create `{}`: {}",
1410 out_filename.display(),
1415 fn is_full_lto_enabled(sess: &Session) -> bool {
1421 Lto::ThinLocal => false,