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;
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;
39 use std::fs::{self, File};
40 use std::io::{self, Write, BufWriter};
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 cfg!(windows) && linker.ends_with(".bat") {
73 let mut cmd = Command::new("cmd");
74 cmd.arg("/c").arg(linker);
81 if let Some(ref linker) = sess.opts.cg.linker {
82 (linker.clone(), cmd(linker), envs)
83 } else if sess.target.target.options.is_like_msvc {
84 let (cmd, envs) = msvc_link_exe_cmd(sess);
85 (PathBuf::from("link.exe"), cmd, envs)
87 let linker = PathBuf::from(&sess.target.target.options.linker);
88 let cmd = cmd(&linker);
94 pub fn msvc_link_exe_cmd(sess: &Session) -> (Command, Vec<(OsString, OsString)>) {
95 use cc::windows_registry;
97 let target = &sess.opts.target_triple;
98 let tool = windows_registry::find_tool(target, "link.exe");
100 if let Some(tool) = tool {
101 let mut cmd = Command::new(tool.path());
102 cmd.args(tool.args());
103 for &(ref k, ref v) in tool.env() {
106 let envs = tool.env().to_vec();
109 debug!("Failed to locate linker.");
110 (Command::new("link.exe"), vec![])
115 pub fn msvc_link_exe_cmd(_sess: &Session) -> (Command, Vec<(OsString, OsString)>) {
116 (Command::new("link.exe"), vec![])
119 fn command_path(sess: &Session) -> OsString {
120 // The compiler's sysroot often has some bundled tools, so add it to the
121 // PATH for the child.
122 let mut new_path = sess.host_filesearch(PathKind::All)
123 .get_tools_search_paths();
124 if let Some(path) = env::var_os("PATH") {
125 new_path.extend(env::split_paths(&path));
127 env::join_paths(new_path).unwrap()
130 pub fn remove(sess: &Session, path: &Path) {
131 match fs::remove_file(path) {
134 sess.err(&format!("failed to remove {}: {}",
141 /// Perform the linkage portion of the compilation phase. This will generate all
142 /// of the requested outputs for this compilation session.
143 pub fn link_binary(sess: &Session,
144 trans: &CrateTranslation,
145 outputs: &OutputFilenames,
146 crate_name: &str) -> Vec<PathBuf> {
147 let mut out_filenames = Vec::new();
148 for &crate_type in sess.crate_types.borrow().iter() {
149 // Ignore executable crates if we have -Z no-trans, as they will error.
150 if (sess.opts.debugging_opts.no_trans ||
151 !sess.opts.output_types.should_trans()) &&
152 crate_type == config::CrateTypeExecutable {
156 if invalid_output_for_target(sess, crate_type) {
157 bug!("invalid output type `{:?}` for target os `{}`",
158 crate_type, sess.opts.target_triple);
160 let mut out_files = link_binary_output(sess,
165 out_filenames.append(&mut out_files);
168 // Remove the temporary object file and metadata if we aren't saving temps
169 if !sess.opts.cg.save_temps {
170 if sess.opts.output_types.should_trans() {
171 for obj in trans.modules.iter().filter_map(|m| m.object.as_ref()) {
175 for obj in trans.modules.iter().filter_map(|m| m.bytecode_compressed.as_ref()) {
178 if let Some(ref obj) = trans.metadata_module.object {
181 if let Some(ref allocator) = trans.allocator_module {
182 if let Some(ref obj) = allocator.object {
185 if let Some(ref bc) = allocator.bytecode_compressed {
194 fn filename_for_metadata(sess: &Session, crate_name: &str, outputs: &OutputFilenames) -> PathBuf {
195 let out_filename = outputs.single_output_file.clone()
198 .join(&format!("lib{}{}.rmeta", crate_name, sess.opts.cg.extra_filename)));
199 check_file_is_writeable(&out_filename, sess);
203 pub fn each_linked_rlib(sess: &Session,
205 f: &mut FnMut(CrateNum, &Path)) -> Result<(), String> {
206 let crates = info.used_crates_static.iter();
207 let fmts = sess.dependency_formats.borrow();
208 let fmts = fmts.get(&config::CrateTypeExecutable)
209 .or_else(|| fmts.get(&config::CrateTypeStaticlib))
210 .or_else(|| fmts.get(&config::CrateTypeCdylib))
211 .or_else(|| fmts.get(&config::CrateTypeProcMacro));
212 let fmts = match fmts {
214 None => return Err(format!("could not find formats for rlibs"))
216 for &(cnum, ref path) in crates {
217 match fmts.get(cnum.as_usize() - 1) {
218 Some(&Linkage::NotLinked) |
219 Some(&Linkage::IncludedFromDylib) => continue,
221 None => return Err(format!("could not find formats for rlibs"))
223 let name = &info.crate_name[&cnum];
224 let path = match *path {
225 LibSource::Some(ref p) => p,
226 LibSource::MetadataOnly => {
227 return Err(format!("could not find rlib for: `{}`, found rmeta (metadata) file",
231 return Err(format!("could not find rlib for: `{}`", name))
239 /// Returns a boolean indicating whether the specified crate should be ignored
242 /// Crates ignored during LTO are not lumped together in the "massive object
243 /// file" that we create and are linked in their normal rlib states. See
244 /// comments below for what crates do not participate in LTO.
246 /// It's unusual for a crate to not participate in LTO. Typically only
247 /// compiler-specific and unstable crates have a reason to not participate in
249 pub fn ignored_for_lto(sess: &Session, info: &CrateInfo, cnum: CrateNum) -> bool {
250 // If our target enables builtin function lowering in LLVM then the
251 // crates providing these functions don't participate in LTO (e.g.
252 // no_builtins or compiler builtins crates).
253 !sess.target.target.options.no_builtins &&
254 (info.is_no_builtins.contains(&cnum) || info.compiler_builtins == Some(cnum))
257 fn link_binary_output(sess: &Session,
258 trans: &CrateTranslation,
259 crate_type: config::CrateType,
260 outputs: &OutputFilenames,
261 crate_name: &str) -> Vec<PathBuf> {
262 for obj in trans.modules.iter().filter_map(|m| m.object.as_ref()) {
263 check_file_is_writeable(obj, sess);
266 let mut out_filenames = vec![];
268 if outputs.outputs.contains_key(&OutputType::Metadata) {
269 let out_filename = filename_for_metadata(sess, crate_name, outputs);
270 // To avoid races with another rustc process scanning the output directory,
271 // we need to write the file somewhere else and atomically move it to its
272 // final destination, with a `fs::rename` call. In order for the rename to
273 // always succeed, the temporary file needs to be on the same filesystem,
274 // which is why we create it inside the output directory specifically.
275 let metadata_tmpdir = match TempDir::new_in(out_filename.parent().unwrap(), "rmeta") {
276 Ok(tmpdir) => tmpdir,
277 Err(err) => sess.fatal(&format!("couldn't create a temp dir: {}", err)),
279 let metadata = emit_metadata(sess, trans, &metadata_tmpdir);
280 if let Err(e) = fs::rename(metadata, &out_filename) {
281 sess.fatal(&format!("failed to write {}: {}", out_filename.display(), e));
283 out_filenames.push(out_filename);
286 let tmpdir = match TempDir::new("rustc") {
287 Ok(tmpdir) => tmpdir,
288 Err(err) => sess.fatal(&format!("couldn't create a temp dir: {}", err)),
291 if outputs.outputs.should_trans() {
292 let out_filename = out_filename(sess, crate_type, outputs, crate_name);
294 config::CrateTypeRlib => {
301 config::CrateTypeStaticlib => {
302 link_staticlib(sess, trans, &out_filename, &tmpdir);
305 link_natively(sess, crate_type, &out_filename, trans, tmpdir.path());
308 out_filenames.push(out_filename);
311 if sess.opts.cg.save_temps {
312 let _ = tmpdir.into_path();
318 fn archive_search_paths(sess: &Session) -> Vec<PathBuf> {
319 let mut search = Vec::new();
320 sess.target_filesearch(PathKind::Native).for_each_lib_search_path(|path, _| {
321 search.push(path.to_path_buf());
326 fn archive_config<'a>(sess: &'a Session,
328 input: Option<&Path>) -> ArchiveConfig<'a> {
331 dst: output.to_path_buf(),
332 src: input.map(|p| p.to_path_buf()),
333 lib_search_paths: archive_search_paths(sess),
337 /// We use a temp directory here to avoid races between concurrent rustc processes,
338 /// such as builds in the same directory using the same filename for metadata while
339 /// building an `.rlib` (stomping over one another), or writing an `.rmeta` into a
340 /// directory being searched for `extern crate` (observing an incomplete file).
341 /// The returned path is the temporary file containing the complete metadata.
342 fn emit_metadata<'a>(sess: &'a Session, trans: &CrateTranslation, tmpdir: &TempDir)
344 let out_filename = tmpdir.path().join(METADATA_FILENAME);
345 let result = fs::File::create(&out_filename).and_then(|mut f| {
346 f.write_all(&trans.metadata.raw_data)
349 if let Err(e) = result {
350 sess.fatal(&format!("failed to write {}: {}", out_filename.display(), e));
363 // An rlib in its current incarnation is essentially a renamed .a file. The
364 // rlib primarily contains the object file of the crate, but it also contains
365 // all of the object files from native libraries. This is done by unzipping
366 // native libraries and inserting all of the contents into this archive.
367 fn link_rlib<'a>(sess: &'a Session,
368 trans: &CrateTranslation,
371 tmpdir: &TempDir) -> ArchiveBuilder<'a> {
372 info!("preparing rlib to {:?}", out_filename);
373 let mut ab = ArchiveBuilder::new(archive_config(sess, out_filename, None));
375 for obj in trans.modules.iter().filter_map(|m| m.object.as_ref()) {
379 // Note that in this loop we are ignoring the value of `lib.cfg`. That is,
380 // we may not be configured to actually include a static library if we're
381 // adding it here. That's because later when we consume this rlib we'll
382 // decide whether we actually needed the static library or not.
384 // To do this "correctly" we'd need to keep track of which libraries added
385 // which object files to the archive. We don't do that here, however. The
386 // #[link(cfg(..))] feature is unstable, though, and only intended to get
387 // liblibc working. In that sense the check below just indicates that if
388 // there are any libraries we want to omit object files for at link time we
389 // just exclude all custom object files.
391 // Eventually if we want to stabilize or flesh out the #[link(cfg(..))]
392 // feature then we'll need to figure out how to record what objects were
393 // loaded from the libraries found here and then encode that into the
394 // metadata of the rlib we're generating somehow.
395 for lib in trans.crate_info.used_libraries.iter() {
397 NativeLibraryKind::NativeStatic => {}
398 NativeLibraryKind::NativeStaticNobundle |
399 NativeLibraryKind::NativeFramework |
400 NativeLibraryKind::NativeUnknown => continue,
402 ab.add_native_library(&lib.name.as_str());
405 // After adding all files to the archive, we need to update the
406 // symbol table of the archive.
409 // Note that it is important that we add all of our non-object "magical
410 // files" *after* all of the object files in the archive. The reason for
411 // this is as follows:
413 // * When performing LTO, this archive will be modified to remove
414 // objects from above. The reason for this is described below.
416 // * When the system linker looks at an archive, it will attempt to
417 // determine the architecture of the archive in order to see whether its
420 // The algorithm for this detection is: iterate over the files in the
421 // archive. Skip magical SYMDEF names. Interpret the first file as an
422 // object file. Read architecture from the object file.
424 // * As one can probably see, if "metadata" and "foo.bc" were placed
425 // before all of the objects, then the architecture of this archive would
426 // not be correctly inferred once 'foo.o' is removed.
428 // Basically, all this means is that this code should not move above the
431 RlibFlavor::Normal => {
432 // Instead of putting the metadata in an object file section, rlibs
433 // contain the metadata in a separate file.
434 ab.add_file(&emit_metadata(sess, trans, tmpdir));
436 // For LTO purposes, the bytecode of this library is also inserted
438 for bytecode in trans.modules.iter().filter_map(|m| m.bytecode_compressed.as_ref()) {
439 ab.add_file(bytecode);
442 // After adding all files to the archive, we need to update the
443 // symbol table of the archive. This currently dies on macOS (see
444 // #11162), and isn't necessary there anyway
445 if !sess.target.target.options.is_like_osx {
450 RlibFlavor::StaticlibBase => {
451 let obj = trans.allocator_module
453 .and_then(|m| m.object.as_ref());
454 if let Some(obj) = obj {
463 // Create a static archive
465 // This is essentially the same thing as an rlib, but it also involves adding
466 // all of the upstream crates' objects into the archive. This will slurp in
467 // all of the native libraries of upstream dependencies as well.
469 // Additionally, there's no way for us to link dynamic libraries, so we warn
470 // about all dynamic library dependencies that they're not linked in.
472 // There's no need to include metadata in a static archive, so ensure to not
473 // link in the metadata object file (and also don't prepare the archive with a
475 fn link_staticlib(sess: &Session,
476 trans: &CrateTranslation,
479 let mut ab = link_rlib(sess,
481 RlibFlavor::StaticlibBase,
484 let mut all_native_libs = vec![];
486 let res = each_linked_rlib(sess, &trans.crate_info, &mut |cnum, path| {
487 let name = &trans.crate_info.crate_name[&cnum];
488 let native_libs = &trans.crate_info.native_libraries[&cnum];
490 // Here when we include the rlib into our staticlib we need to make a
491 // decision whether to include the extra object files along the way.
492 // These extra object files come from statically included native
493 // libraries, but they may be cfg'd away with #[link(cfg(..))].
495 // This unstable feature, though, only needs liblibc to work. The only
496 // use case there is where musl is statically included in liblibc.rlib,
497 // so if we don't want the included version we just need to skip it. As
498 // a result the logic here is that if *any* linked library is cfg'd away
499 // we just skip all object files.
501 // Clearly this is not sufficient for a general purpose feature, and
502 // we'd want to read from the library's metadata to determine which
503 // object files come from where and selectively skip them.
504 let skip_object_files = native_libs.iter().any(|lib| {
505 lib.kind == NativeLibraryKind::NativeStatic && !relevant_lib(sess, lib)
509 sess.lto() && !ignored_for_lto(sess, &trans.crate_info, cnum),
510 skip_object_files).unwrap();
512 all_native_libs.extend(trans.crate_info.native_libraries[&cnum].iter().cloned());
514 if let Err(e) = res {
521 if !all_native_libs.is_empty() {
522 if sess.opts.prints.contains(&PrintRequest::NativeStaticLibs) {
523 print_native_static_libs(sess, &all_native_libs);
528 fn print_native_static_libs(sess: &Session, all_native_libs: &[NativeLibrary]) {
529 let lib_args: Vec<_> = all_native_libs.iter()
530 .filter(|l| relevant_lib(sess, l))
531 .filter_map(|lib| match lib.kind {
532 NativeLibraryKind::NativeStaticNobundle |
533 NativeLibraryKind::NativeUnknown => {
534 if sess.target.target.options.is_like_msvc {
535 Some(format!("{}.lib", lib.name))
537 Some(format!("-l{}", lib.name))
540 NativeLibraryKind::NativeFramework => {
541 // ld-only syntax, since there are no frameworks in MSVC
542 Some(format!("-framework {}", lib.name))
544 // These are included, no need to print them
545 NativeLibraryKind::NativeStatic => None,
548 if !lib_args.is_empty() {
549 sess.note_without_error("Link against the following native artifacts when linking \
550 against this static library. The order and any duplication \
551 can be significant on some platforms.");
552 // Prefix for greppability
553 sess.note_without_error(&format!("native-static-libs: {}", &lib_args.join(" ")));
557 // Create a dynamic library or executable
559 // This will invoke the system linker/cc to create the resulting file. This
560 // links to all upstream files as well.
561 fn link_natively(sess: &Session,
562 crate_type: config::CrateType,
564 trans: &CrateTranslation,
566 info!("preparing {:?} to {:?}", crate_type, out_filename);
567 let flavor = sess.linker_flavor();
569 // The "binaryen linker" is massively special, so skip everything below.
570 if flavor == LinkerFlavor::Binaryen {
571 return link_binaryen(sess, crate_type, out_filename, trans, tmpdir);
574 // The invocations of cc share some flags across platforms
575 let (pname, mut cmd, envs) = get_linker(sess);
576 // This will set PATH on windows
579 let root = sess.target_filesearch(PathKind::Native).get_lib_path();
580 if let Some(args) = sess.target.target.options.pre_link_args.get(&flavor) {
583 if let Some(ref args) = sess.opts.debugging_opts.pre_link_args {
586 cmd.args(&sess.opts.debugging_opts.pre_link_arg);
588 let pre_link_objects = if crate_type == config::CrateTypeExecutable {
589 &sess.target.target.options.pre_link_objects_exe
591 &sess.target.target.options.pre_link_objects_dll
593 for obj in pre_link_objects {
594 cmd.arg(root.join(obj));
597 if sess.target.target.options.is_like_emscripten {
599 cmd.arg(if sess.panic_strategy() == PanicStrategy::Abort {
600 "DISABLE_EXCEPTION_CATCHING=1"
602 "DISABLE_EXCEPTION_CATCHING=0"
607 let mut linker = trans.linker_info.to_linker(cmd, &sess);
608 link_args(&mut *linker, sess, crate_type, tmpdir,
609 out_filename, trans);
610 cmd = linker.finalize();
612 if let Some(args) = sess.target.target.options.late_link_args.get(&flavor) {
615 for obj in &sess.target.target.options.post_link_objects {
616 cmd.arg(root.join(obj));
618 if let Some(args) = sess.target.target.options.post_link_args.get(&flavor) {
621 for &(ref k, ref v) in &sess.target.target.options.link_env {
625 if sess.opts.debugging_opts.print_link_args {
626 println!("{:?}", &cmd);
629 // May have not found libraries in the right formats.
630 sess.abort_if_errors();
632 // Invoke the system linker
634 // Note that there's a terribly awful hack that really shouldn't be present
635 // in any compiler. Here an environment variable is supported to
636 // automatically retry the linker invocation if the linker looks like it
639 // Gee that seems odd, normally segfaults are things we want to know about!
640 // Unfortunately though in rust-lang/rust#38878 we're experiencing the
641 // linker segfaulting on Travis quite a bit which is causing quite a bit of
642 // pain to land PRs when they spuriously fail due to a segfault.
644 // The issue #38878 has some more debugging information on it as well, but
645 // this unfortunately looks like it's just a race condition in macOS's linker
646 // with some thread pool working in the background. It seems that no one
647 // currently knows a fix for this so in the meantime we're left with this...
649 let retry_on_segfault = env::var("RUSTC_RETRY_LINKER_ON_SEGFAULT").is_ok();
654 prog = time(sess.time_passes(), "running linker", || {
655 exec_linker(sess, &mut cmd, tmpdir)
657 if !retry_on_segfault || i > 3 {
660 let output = match prog {
661 Ok(ref output) => output,
664 if output.status.success() {
667 let mut out = output.stderr.clone();
668 out.extend(&output.stdout);
669 let out = String::from_utf8_lossy(&out);
670 let msg_segv = "clang: error: unable to execute command: Segmentation fault: 11";
671 let msg_bus = "clang: error: unable to execute command: Bus error: 10";
672 if !(out.contains(msg_segv) || out.contains(msg_bus)) {
677 "looks like the linker segfaulted when we tried to call it, \
678 automatically retrying again. cmd = {:?}, out = {}.",
686 fn escape_string(s: &[u8]) -> String {
687 str::from_utf8(s).map(|s| s.to_owned())
688 .unwrap_or_else(|_| {
689 let mut x = "Non-UTF-8 output: ".to_string();
691 .flat_map(|&b| ascii::escape_default(b))
692 .map(|b| char::from_u32(b as u32).unwrap()));
696 if !prog.status.success() {
697 let mut output = prog.stderr.clone();
698 output.extend_from_slice(&prog.stdout);
699 sess.struct_err(&format!("linking with `{}` failed: {}",
702 .note(&format!("{:?}", &cmd))
703 .note(&escape_string(&output))
705 sess.abort_if_errors();
707 info!("linker stderr:\n{}", escape_string(&prog.stderr));
708 info!("linker stdout:\n{}", escape_string(&prog.stdout));
711 let linker_not_found = e.kind() == io::ErrorKind::NotFound;
713 let mut linker_error = {
714 if linker_not_found {
715 sess.struct_err(&format!("linker `{}` not found", pname.display()))
717 sess.struct_err(&format!("could not exec the linker `{}`", pname.display()))
721 linker_error.note(&format!("{}", e));
723 if !linker_not_found {
724 linker_error.note(&format!("{:?}", &cmd));
729 if sess.target.target.options.is_like_msvc && linker_not_found {
730 sess.note_without_error("the msvc targets depend on the msvc linker \
731 but `link.exe` was not found");
732 sess.note_without_error("please ensure that VS 2013 or VS 2015 was installed \
733 with the Visual C++ option");
735 sess.abort_if_errors();
740 // On macOS, debuggers need this utility to get run to do some munging of
742 if sess.target.target.options.is_like_osx && sess.opts.debuginfo != NoDebugInfo {
743 match Command::new("dsymutil").arg(out_filename).output() {
745 Err(e) => sess.fatal(&format!("failed to run dsymutil: {}", e)),
750 fn exec_linker(sess: &Session, cmd: &mut Command, tmpdir: &Path)
751 -> io::Result<Output>
753 // When attempting to spawn the linker we run a risk of blowing out the
754 // size limits for spawning a new process with respect to the arguments
755 // we pass on the command line.
757 // Here we attempt to handle errors from the OS saying "your list of
758 // arguments is too big" by reinvoking the linker again with an `@`-file
759 // that contains all the arguments. The theory is that this is then
760 // accepted on all linkers and the linker will read all its options out of
761 // there instead of looking at the command line.
762 match cmd.command().stdout(Stdio::piped()).stderr(Stdio::piped()).spawn() {
763 Ok(child) => return child.wait_with_output(),
764 Err(ref e) if command_line_too_big(e) => {}
765 Err(e) => return Err(e)
768 let file = tmpdir.join("linker-arguments");
769 let mut cmd2 = Command::new(cmd.get_program());
770 cmd2.arg(format!("@{}", file.display()));
771 for &(ref k, ref v) in cmd.get_env() {
774 let mut f = BufWriter::new(File::create(&file)?);
775 for arg in cmd.get_args() {
776 writeln!(f, "{}", Escape {
777 arg: arg.to_str().unwrap(),
778 is_like_msvc: sess.target.target.options.is_like_msvc,
782 return cmd2.output();
785 fn command_line_too_big(err: &io::Error) -> bool {
786 err.raw_os_error() == Some(::libc::E2BIG)
790 fn command_line_too_big(err: &io::Error) -> bool {
791 const ERROR_FILENAME_EXCED_RANGE: i32 = 206;
792 err.raw_os_error() == Some(ERROR_FILENAME_EXCED_RANGE)
800 impl<'a> fmt::Display for Escape<'a> {
801 fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
802 if self.is_like_msvc {
803 // This is "documented" at
804 // https://msdn.microsoft.com/en-us/library/4xdcbak7.aspx
806 // Unfortunately there's not a great specification of the
807 // syntax I could find online (at least) but some local
808 // testing showed that this seemed sufficient-ish to catch
809 // at least a few edge cases.
811 for c in self.arg.chars() {
813 '"' => write!(f, "\\{}", c)?,
814 c => write!(f, "{}", c)?,
819 // This is documented at https://linux.die.net/man/1/ld, namely:
821 // > Options in file are separated by whitespace. A whitespace
822 // > character may be included in an option by surrounding the
823 // > entire option in either single or double quotes. Any
824 // > character (including a backslash) may be included by
825 // > prefixing the character to be included with a backslash.
827 // We put an argument on each line, so all we need to do is
828 // ensure the line is interpreted as one whole argument.
829 for c in self.arg.chars() {
832 ' ' => write!(f, "\\{}", c)?,
833 c => write!(f, "{}", c)?,
842 fn link_args(cmd: &mut Linker,
844 crate_type: config::CrateType,
847 trans: &CrateTranslation) {
849 // The default library location, we need this to find the runtime.
850 // The location of crates will be determined as needed.
851 let lib_path = sess.target_filesearch(PathKind::All).get_lib_path();
854 let t = &sess.target.target;
856 cmd.include_path(&fix_windows_verbatim_for_gcc(&lib_path));
857 for obj in trans.modules.iter().filter_map(|m| m.object.as_ref()) {
860 cmd.output_filename(out_filename);
862 if crate_type == config::CrateTypeExecutable &&
863 sess.target.target.options.is_like_windows {
864 if let Some(ref s) = trans.windows_subsystem {
869 // If we're building a dynamic library then some platforms need to make sure
870 // that all symbols are exported correctly from the dynamic library.
871 if crate_type != config::CrateTypeExecutable ||
872 sess.target.target.options.is_like_emscripten {
873 cmd.export_symbols(tmpdir, crate_type);
876 // When linking a dynamic library, we put the metadata into a section of the
877 // executable. This metadata is in a separate object file from the main
878 // object file, so we link that in here.
879 if crate_type == config::CrateTypeDylib ||
880 crate_type == config::CrateTypeProcMacro {
881 if let Some(obj) = trans.metadata_module.object.as_ref() {
886 let obj = trans.allocator_module
888 .and_then(|m| m.object.as_ref());
889 if let Some(obj) = obj {
893 // Try to strip as much out of the generated object by removing unused
894 // sections if possible. See more comments in linker.rs
895 if !sess.opts.cg.link_dead_code {
896 let keep_metadata = crate_type == config::CrateTypeDylib;
897 cmd.gc_sections(keep_metadata);
900 let used_link_args = &trans.crate_info.link_args;
902 if crate_type == config::CrateTypeExecutable &&
903 t.options.position_independent_executables {
904 let empty_vec = Vec::new();
905 let args = sess.opts.cg.link_args.as_ref().unwrap_or(&empty_vec);
906 let more_args = &sess.opts.cg.link_arg;
907 let mut args = args.iter().chain(more_args.iter()).chain(used_link_args.iter());
909 if get_reloc_model(sess) == llvm::RelocMode::PIC
910 && !sess.crt_static() && !args.any(|x| *x == "-static") {
911 cmd.position_independent_executable();
915 let relro_level = match sess.opts.debugging_opts.relro_level {
916 Some(level) => level,
917 None => t.options.relro_level,
920 RelroLevel::Full => {
923 RelroLevel::Partial => {
926 RelroLevel::Off => {},
929 // Pass optimization flags down to the linker.
932 // Pass debuginfo flags down to the linker.
935 // We want to prevent the compiler from accidentally leaking in any system
936 // libraries, so we explicitly ask gcc to not link to any libraries by
937 // default. Note that this does not happen for windows because windows pulls
938 // in some large number of libraries and I couldn't quite figure out which
940 if t.options.no_default_libraries {
941 cmd.no_default_libraries();
944 // Take careful note of the ordering of the arguments we pass to the linker
945 // here. Linkers will assume that things on the left depend on things to the
946 // right. Things on the right cannot depend on things on the left. This is
947 // all formally implemented in terms of resolving symbols (libs on the right
948 // resolve unknown symbols of libs on the left, but not vice versa).
950 // For this reason, we have organized the arguments we pass to the linker as
953 // 1. The local object that LLVM just generated
954 // 2. Local native libraries
955 // 3. Upstream rust libraries
956 // 4. Upstream native libraries
958 // The rationale behind this ordering is that those items lower down in the
959 // list can't depend on items higher up in the list. For example nothing can
960 // depend on what we just generated (e.g. that'd be a circular dependency).
961 // Upstream rust libraries are not allowed to depend on our local native
962 // libraries as that would violate the structure of the DAG, in that
963 // scenario they are required to link to them as well in a shared fashion.
965 // Note that upstream rust libraries may contain native dependencies as
966 // well, but they also can't depend on what we just started to add to the
967 // link line. And finally upstream native libraries can't depend on anything
968 // in this DAG so far because they're only dylibs and dylibs can only depend
969 // on other dylibs (e.g. other native deps).
970 add_local_native_libraries(cmd, sess, trans);
971 add_upstream_rust_crates(cmd, sess, trans, crate_type, tmpdir);
972 add_upstream_native_libraries(cmd, sess, trans, crate_type);
974 // Tell the linker what we're doing.
975 if crate_type != config::CrateTypeExecutable {
976 cmd.build_dylib(out_filename);
978 if crate_type == config::CrateTypeExecutable && sess.crt_static() {
979 cmd.build_static_executable();
982 // FIXME (#2397): At some point we want to rpath our guesses as to
983 // where extern libraries might live, based on the
984 // addl_lib_search_paths
985 if sess.opts.cg.rpath {
986 let sysroot = sess.sysroot();
987 let target_triple = &sess.opts.target_triple;
988 let mut get_install_prefix_lib_path = || {
989 let install_prefix = option_env!("CFG_PREFIX").expect("CFG_PREFIX");
990 let tlib = filesearch::relative_target_lib_path(sysroot, target_triple);
991 let mut path = PathBuf::from(install_prefix);
996 let mut rpath_config = RPathConfig {
997 used_crates: &trans.crate_info.used_crates_dynamic,
998 out_filename: out_filename.to_path_buf(),
999 has_rpath: sess.target.target.options.has_rpath,
1000 is_like_osx: sess.target.target.options.is_like_osx,
1001 linker_is_gnu: sess.target.target.options.linker_is_gnu,
1002 get_install_prefix_lib_path: &mut get_install_prefix_lib_path,
1004 cmd.args(&rpath::get_rpath_flags(&mut rpath_config));
1007 // Finally add all the linker arguments provided on the command line along
1008 // with any #[link_args] attributes found inside the crate
1009 if let Some(ref args) = sess.opts.cg.link_args {
1012 cmd.args(&sess.opts.cg.link_arg);
1013 cmd.args(&used_link_args);
1016 // # Native library linking
1018 // User-supplied library search paths (-L on the command line). These are
1019 // the same paths used to find Rust crates, so some of them may have been
1020 // added already by the previous crate linking code. This only allows them
1021 // to be found at compile time so it is still entirely up to outside
1022 // forces to make sure that library can be found at runtime.
1024 // Also note that the native libraries linked here are only the ones located
1025 // in the current crate. Upstream crates with native library dependencies
1026 // may have their native library pulled in above.
1027 fn add_local_native_libraries(cmd: &mut Linker,
1029 trans: &CrateTranslation) {
1030 sess.target_filesearch(PathKind::All).for_each_lib_search_path(|path, k| {
1032 PathKind::Framework => { cmd.framework_path(path); }
1033 _ => { cmd.include_path(&fix_windows_verbatim_for_gcc(path)); }
1037 let relevant_libs = trans.crate_info.used_libraries.iter().filter(|l| {
1038 relevant_lib(sess, l)
1041 let search_path = archive_search_paths(sess);
1042 for lib in relevant_libs {
1044 NativeLibraryKind::NativeUnknown => cmd.link_dylib(&lib.name.as_str()),
1045 NativeLibraryKind::NativeFramework => cmd.link_framework(&lib.name.as_str()),
1046 NativeLibraryKind::NativeStaticNobundle => cmd.link_staticlib(&lib.name.as_str()),
1047 NativeLibraryKind::NativeStatic => cmd.link_whole_staticlib(&lib.name.as_str(),
1053 // # Rust Crate linking
1055 // Rust crates are not considered at all when creating an rlib output. All
1056 // dependencies will be linked when producing the final output (instead of
1057 // the intermediate rlib version)
1058 fn add_upstream_rust_crates(cmd: &mut Linker,
1060 trans: &CrateTranslation,
1061 crate_type: config::CrateType,
1063 // All of the heavy lifting has previously been accomplished by the
1064 // dependency_format module of the compiler. This is just crawling the
1065 // output of that module, adding crates as necessary.
1067 // Linking to a rlib involves just passing it to the linker (the linker
1068 // will slurp up the object files inside), and linking to a dynamic library
1069 // involves just passing the right -l flag.
1071 let formats = sess.dependency_formats.borrow();
1072 let data = formats.get(&crate_type).unwrap();
1074 // Invoke get_used_crates to ensure that we get a topological sorting of
1076 let deps = &trans.crate_info.used_crates_dynamic;
1078 let mut compiler_builtins = None;
1080 for &(cnum, _) in deps.iter() {
1081 // We may not pass all crates through to the linker. Some crates may
1082 // appear statically in an existing dylib, meaning we'll pick up all the
1083 // symbols from the dylib.
1084 let src = &trans.crate_info.used_crate_source[&cnum];
1085 match data[cnum.as_usize() - 1] {
1086 _ if trans.crate_info.profiler_runtime == Some(cnum) => {
1087 add_static_crate(cmd, sess, trans, tmpdir, crate_type, cnum);
1089 _ if trans.crate_info.sanitizer_runtime == Some(cnum) => {
1090 link_sanitizer_runtime(cmd, sess, trans, tmpdir, cnum);
1092 // compiler-builtins are always placed last to ensure that they're
1093 // linked correctly.
1094 _ if trans.crate_info.compiler_builtins == Some(cnum) => {
1095 assert!(compiler_builtins.is_none());
1096 compiler_builtins = Some(cnum);
1098 Linkage::NotLinked |
1099 Linkage::IncludedFromDylib => {}
1100 Linkage::Static => {
1101 add_static_crate(cmd, sess, trans, tmpdir, crate_type, cnum);
1103 Linkage::Dynamic => {
1104 add_dynamic_crate(cmd, sess, &src.dylib.as_ref().unwrap().0)
1109 // compiler-builtins are always placed last to ensure that they're
1110 // linked correctly.
1111 // We must always link the `compiler_builtins` crate statically. Even if it
1112 // was already "included" in a dylib (e.g. `libstd` when `-C prefer-dynamic`
1114 if let Some(cnum) = compiler_builtins {
1115 add_static_crate(cmd, sess, trans, tmpdir, crate_type, cnum);
1118 // Converts a library file-stem into a cc -l argument
1119 fn unlib<'a>(config: &config::Config, stem: &'a str) -> &'a str {
1120 if stem.starts_with("lib") && !config.target.options.is_like_windows {
1127 // We must link the sanitizer runtime using -Wl,--whole-archive but since
1128 // it's packed in a .rlib, it contains stuff that are not objects that will
1129 // make the linker error. So we must remove those bits from the .rlib before
1131 fn link_sanitizer_runtime(cmd: &mut Linker,
1133 trans: &CrateTranslation,
1136 let src = &trans.crate_info.used_crate_source[&cnum];
1137 let cratepath = &src.rlib.as_ref().unwrap().0;
1139 if sess.target.target.options.is_like_osx {
1140 // On Apple platforms, the sanitizer is always built as a dylib, and
1141 // LLVM will link to `@rpath/*.dylib`, so we need to specify an
1142 // rpath to the library as well (the rpath should be absolute, see
1143 // PR #41352 for details).
1145 // FIXME: Remove this logic into librustc_*san once Cargo supports it
1146 let rpath = cratepath.parent().unwrap();
1147 let rpath = rpath.to_str().expect("non-utf8 component in path");
1148 cmd.args(&["-Wl,-rpath".into(), "-Xlinker".into(), rpath.into()]);
1151 let dst = tmpdir.join(cratepath.file_name().unwrap());
1152 let cfg = archive_config(sess, &dst, Some(cratepath));
1153 let mut archive = ArchiveBuilder::new(cfg);
1154 archive.update_symbols();
1156 for f in archive.src_files() {
1157 if f.ends_with(RLIB_BYTECODE_EXTENSION) || f == METADATA_FILENAME {
1158 archive.remove_file(&f);
1165 cmd.link_whole_rlib(&dst);
1168 // Adds the static "rlib" versions of all crates to the command line.
1169 // There's a bit of magic which happens here specifically related to LTO and
1170 // dynamic libraries. Specifically:
1172 // * For LTO, we remove upstream object files.
1173 // * For dylibs we remove metadata and bytecode from upstream rlibs
1175 // When performing LTO, almost(*) all of the bytecode from the upstream
1176 // libraries has already been included in our object file output. As a
1177 // result we need to remove the object files in the upstream libraries so
1178 // the linker doesn't try to include them twice (or whine about duplicate
1179 // symbols). We must continue to include the rest of the rlib, however, as
1180 // it may contain static native libraries which must be linked in.
1182 // (*) Crates marked with `#![no_builtins]` don't participate in LTO and
1183 // their bytecode wasn't included. The object files in those libraries must
1184 // still be passed to the linker.
1186 // When making a dynamic library, linkers by default don't include any
1187 // object files in an archive if they're not necessary to resolve the link.
1188 // We basically want to convert the archive (rlib) to a dylib, though, so we
1189 // *do* want everything included in the output, regardless of whether the
1190 // linker thinks it's needed or not. As a result we must use the
1191 // --whole-archive option (or the platform equivalent). When using this
1192 // option the linker will fail if there are non-objects in the archive (such
1193 // as our own metadata and/or bytecode). All in all, for rlibs to be
1194 // entirely included in dylibs, we need to remove all non-object files.
1196 // Note, however, that if we're not doing LTO or we're not producing a dylib
1197 // (aka we're making an executable), we can just pass the rlib blindly to
1198 // the linker (fast) because it's fine if it's not actually included as
1199 // we're at the end of the dependency chain.
1200 fn add_static_crate(cmd: &mut Linker,
1202 trans: &CrateTranslation,
1204 crate_type: config::CrateType,
1206 let src = &trans.crate_info.used_crate_source[&cnum];
1207 let cratepath = &src.rlib.as_ref().unwrap().0;
1209 // See the comment above in `link_staticlib` and `link_rlib` for why if
1210 // there's a static library that's not relevant we skip all object
1212 let native_libs = &trans.crate_info.native_libraries[&cnum];
1213 let skip_native = native_libs.iter().any(|lib| {
1214 lib.kind == NativeLibraryKind::NativeStatic && !relevant_lib(sess, lib)
1217 if (!sess.lto() || ignored_for_lto(sess, &trans.crate_info, cnum)) &&
1218 crate_type != config::CrateTypeDylib &&
1220 cmd.link_rlib(&fix_windows_verbatim_for_gcc(cratepath));
1224 let dst = tmpdir.join(cratepath.file_name().unwrap());
1225 let name = cratepath.file_name().unwrap().to_str().unwrap();
1226 let name = &name[3..name.len() - 5]; // chop off lib/.rlib
1228 time(sess.time_passes(), &format!("altering {}.rlib", name), || {
1229 let cfg = archive_config(sess, &dst, Some(cratepath));
1230 let mut archive = ArchiveBuilder::new(cfg);
1231 archive.update_symbols();
1233 let mut any_objects = false;
1234 for f in archive.src_files() {
1235 if f.ends_with(RLIB_BYTECODE_EXTENSION) || f == METADATA_FILENAME {
1236 archive.remove_file(&f);
1240 let canonical = f.replace("-", "_");
1241 let canonical_name = name.replace("-", "_");
1243 // Look for `.rcgu.o` at the end of the filename to conclude
1244 // that this is a Rust-related object file.
1245 fn looks_like_rust(s: &str) -> bool {
1246 let path = Path::new(s);
1247 let ext = path.extension().and_then(|s| s.to_str());
1248 if ext != Some(OutputType::Object.extension()) {
1251 let ext2 = path.file_stem()
1252 .and_then(|s| Path::new(s).extension())
1253 .and_then(|s| s.to_str());
1254 ext2 == Some(RUST_CGU_EXT)
1257 let is_rust_object =
1258 canonical.starts_with(&canonical_name) &&
1259 looks_like_rust(&f);
1261 // If we've been requested to skip all native object files
1262 // (those not generated by the rust compiler) then we can skip
1263 // this file. See above for why we may want to do this.
1264 let skip_because_cfg_say_so = skip_native && !is_rust_object;
1266 // If we're performing LTO and this is a rust-generated object
1267 // file, then we don't need the object file as it's part of the
1268 // LTO module. Note that `#![no_builtins]` is excluded from LTO,
1269 // though, so we let that object file slide.
1270 let skip_because_lto = sess.lto() &&
1272 (sess.target.target.options.no_builtins ||
1273 !trans.crate_info.is_no_builtins.contains(&cnum));
1275 if skip_because_cfg_say_so || skip_because_lto {
1276 archive.remove_file(&f);
1287 // If we're creating a dylib, then we need to include the
1288 // whole of each object in our archive into that artifact. This is
1289 // because a `dylib` can be reused as an intermediate artifact.
1291 // Note, though, that we don't want to include the whole of a
1292 // compiler-builtins crate (e.g. compiler-rt) because it'll get
1293 // repeatedly linked anyway.
1294 if crate_type == config::CrateTypeDylib &&
1295 trans.crate_info.compiler_builtins != Some(cnum) {
1296 cmd.link_whole_rlib(&fix_windows_verbatim_for_gcc(&dst));
1298 cmd.link_rlib(&fix_windows_verbatim_for_gcc(&dst));
1303 // Same thing as above, but for dynamic crates instead of static crates.
1304 fn add_dynamic_crate(cmd: &mut Linker, sess: &Session, cratepath: &Path) {
1305 // If we're performing LTO, then it should have been previously required
1306 // that all upstream rust dependencies were available in an rlib format.
1307 assert!(!sess.lto());
1309 // Just need to tell the linker about where the library lives and
1311 let parent = cratepath.parent();
1312 if let Some(dir) = parent {
1313 cmd.include_path(&fix_windows_verbatim_for_gcc(dir));
1315 let filestem = cratepath.file_stem().unwrap().to_str().unwrap();
1316 cmd.link_rust_dylib(&unlib(&sess.target, filestem),
1317 parent.unwrap_or(Path::new("")));
1321 // Link in all of our upstream crates' native dependencies. Remember that
1322 // all of these upstream native dependencies are all non-static
1323 // dependencies. We've got two cases then:
1325 // 1. The upstream crate is an rlib. In this case we *must* link in the
1326 // native dependency because the rlib is just an archive.
1328 // 2. The upstream crate is a dylib. In order to use the dylib, we have to
1329 // have the dependency present on the system somewhere. Thus, we don't
1330 // gain a whole lot from not linking in the dynamic dependency to this
1333 // The use case for this is a little subtle. In theory the native
1334 // dependencies of a crate are purely an implementation detail of the crate
1335 // itself, but the problem arises with generic and inlined functions. If a
1336 // generic function calls a native function, then the generic function must
1337 // be instantiated in the target crate, meaning that the native symbol must
1338 // also be resolved in the target crate.
1339 fn add_upstream_native_libraries(cmd: &mut Linker,
1341 trans: &CrateTranslation,
1342 crate_type: config::CrateType) {
1343 // Be sure to use a topological sorting of crates because there may be
1344 // interdependencies between native libraries. When passing -nodefaultlibs,
1345 // for example, almost all native libraries depend on libc, so we have to
1346 // make sure that's all the way at the right (liblibc is near the base of
1347 // the dependency chain).
1349 // This passes RequireStatic, but the actual requirement doesn't matter,
1350 // we're just getting an ordering of crate numbers, we're not worried about
1352 let formats = sess.dependency_formats.borrow();
1353 let data = formats.get(&crate_type).unwrap();
1355 let crates = &trans.crate_info.used_crates_static;
1356 for &(cnum, _) in crates {
1357 for lib in trans.crate_info.native_libraries[&cnum].iter() {
1358 if !relevant_lib(sess, &lib) {
1362 NativeLibraryKind::NativeUnknown => cmd.link_dylib(&lib.name.as_str()),
1363 NativeLibraryKind::NativeFramework => cmd.link_framework(&lib.name.as_str()),
1364 NativeLibraryKind::NativeStaticNobundle => {
1365 // Link "static-nobundle" native libs only if the crate they originate from
1366 // is being linked statically to the current crate. If it's linked dynamically
1367 // or is an rlib already included via some other dylib crate, the symbols from
1368 // native libs will have already been included in that dylib.
1369 if data[cnum.as_usize() - 1] == Linkage::Static {
1370 cmd.link_staticlib(&lib.name.as_str())
1373 // ignore statically included native libraries here as we've
1374 // already included them when we included the rust library
1376 NativeLibraryKind::NativeStatic => {}
1382 fn relevant_lib(sess: &Session, lib: &NativeLibrary) -> bool {
1384 Some(ref cfg) => attr::cfg_matches(cfg, &sess.parse_sess, None),
1389 /// For now "linking with binaryen" is just "move the one module we generated in
1390 /// the backend to the final output"
1392 /// That is, all the heavy lifting happens during the `back::write` phase. Here
1393 /// we just clean up after that.
1395 /// Note that this is super temporary and "will not survive the night", this is
1396 /// guaranteed to get removed as soon as a linker for wasm exists. This should
1397 /// not be used for anything other than wasm.
1398 fn link_binaryen(sess: &Session,
1399 _crate_type: config::CrateType,
1400 out_filename: &Path,
1401 trans: &CrateTranslation,
1403 assert!(trans.allocator_module.is_none());
1404 assert_eq!(trans.modules.len(), 1);
1406 let object = trans.modules[0].object.as_ref().expect("object must exist");
1407 let res = fs::hard_link(object, out_filename)
1408 .or_else(|_| fs::copy(object, out_filename).map(|_| ()));
1409 if let Err(e) = res {
1410 sess.fatal(&format!("failed to create `{}`: {}",
1411 out_filename.display(),