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::linker::Linker;
13 use super::rpath::RPathConfig;
17 use session::config::NoDebugInfo;
18 use session::config::{OutputFilenames, Input, OutputType};
19 use session::filesearch;
20 use session::search_paths::PathKind;
22 use middle::cstore::{self, LinkMeta, NativeLibrary, LibSource};
23 use middle::cstore::{LinkagePreference, NativeLibraryKind};
24 use middle::dependency_format::Linkage;
26 use util::common::time;
27 use util::fs::fix_windows_verbatim_for_gcc;
28 use rustc::dep_graph::DepNode;
29 use rustc::hir::def_id::CrateNum;
30 use rustc::hir::svh::Svh;
31 use rustc_back::tempdir::TempDir;
32 use rustc_back::PanicStrategy;
33 use rustc_incremental::IncrementalHashesMap;
34 use context::get_reloc_model;
40 use std::ffi::OsString;
42 use std::io::{self, Read, Write};
44 use std::path::{Path, PathBuf};
45 use std::process::Command;
52 /// The LLVM module name containing crate-metadata. This includes a `.` on
53 /// purpose, so it cannot clash with the name of a user-defined module.
54 pub const METADATA_MODULE_NAME: &'static str = "crate.metadata";
55 /// The name of the crate-metadata object file the compiler generates. Must
56 /// match up with `METADATA_MODULE_NAME`.
57 pub const METADATA_OBJ_NAME: &'static str = "crate.metadata.o";
59 // RLIB LLVM-BYTECODE OBJECT LAYOUT
62 // 0..10 "RUST_OBJECT" encoded in ASCII
63 // 11..14 format version as little-endian u32
64 // 15..22 size in bytes of deflate compressed LLVM bitcode as
66 // 23.. compressed LLVM bitcode
68 // This is the "magic number" expected at the beginning of a LLVM bytecode
70 pub const RLIB_BYTECODE_OBJECT_MAGIC: &'static [u8] = b"RUST_OBJECT";
72 // The version number this compiler will write to bytecode objects in rlibs
73 pub const RLIB_BYTECODE_OBJECT_VERSION: u32 = 1;
75 // The offset in bytes the bytecode object format version number can be found at
76 pub const RLIB_BYTECODE_OBJECT_VERSION_OFFSET: usize = 11;
78 // The offset in bytes the size of the compressed bytecode can be found at in
80 pub const RLIB_BYTECODE_OBJECT_V1_DATASIZE_OFFSET: usize =
81 RLIB_BYTECODE_OBJECT_VERSION_OFFSET + 4;
83 // The offset in bytes the compressed LLVM bytecode can be found at in format
85 pub const RLIB_BYTECODE_OBJECT_V1_DATA_OFFSET: usize =
86 RLIB_BYTECODE_OBJECT_V1_DATASIZE_OFFSET + 8;
89 pub fn find_crate_name(sess: Option<&Session>,
90 attrs: &[ast::Attribute],
91 input: &Input) -> String {
92 let validate = |s: String, span: Option<Span>| {
93 cstore::validate_crate_name(sess, &s, span);
97 // Look in attributes 100% of the time to make sure the attribute is marked
98 // as used. After doing this, however, we still prioritize a crate name from
99 // the command line over one found in the #[crate_name] attribute. If we
100 // find both we ensure that they're the same later on as well.
101 let attr_crate_name = attrs.iter().find(|at| at.check_name("crate_name"))
102 .and_then(|at| at.value_str().map(|s| (at, s)));
104 if let Some(sess) = sess {
105 if let Some(ref s) = sess.opts.crate_name {
106 if let Some((attr, name)) = attr_crate_name {
108 let msg = format!("--crate-name and #[crate_name] are \
109 required to match, but `{}` != `{}`",
111 sess.span_err(attr.span, &msg);
114 return validate(s.clone(), None);
118 if let Some((attr, s)) = attr_crate_name {
119 return validate(s.to_string(), Some(attr.span));
121 if let Input::File(ref path) = *input {
122 if let Some(s) = path.file_stem().and_then(|s| s.to_str()) {
123 if s.starts_with("-") {
124 let msg = format!("crate names cannot start with a `-`, but \
125 `{}` has a leading hyphen", s);
126 if let Some(sess) = sess {
130 return validate(s.replace("-", "_"), None);
135 "rust_out".to_string()
138 pub fn build_link_meta(incremental_hashes_map: &IncrementalHashesMap) -> LinkMeta {
140 crate_hash: Svh::new(incremental_hashes_map[&DepNode::Krate].to_smaller_hash()),
146 // The third parameter is for an extra path to add to PATH for MSVC
147 // cross linkers for host toolchain DLL dependencies
148 pub fn get_linker(sess: &Session) -> (String, Command, Option<PathBuf>) {
149 if let Some(ref linker) = sess.opts.cg.linker {
150 (linker.clone(), Command::new(linker), None)
151 } else if sess.target.target.options.is_like_msvc {
152 let (cmd, host) = msvc::link_exe_cmd(sess);
153 ("link.exe".to_string(), cmd, host)
155 (sess.target.target.options.linker.clone(),
156 Command::new(&sess.target.target.options.linker), None)
160 pub fn get_ar_prog(sess: &Session) -> String {
161 sess.opts.cg.ar.clone().unwrap_or_else(|| {
162 sess.target.target.options.ar.clone()
166 fn command_path(sess: &Session, extra: Option<PathBuf>) -> OsString {
167 // The compiler's sysroot often has some bundled tools, so add it to the
168 // PATH for the child.
169 let mut new_path = sess.host_filesearch(PathKind::All)
170 .get_tools_search_paths();
171 if let Some(path) = env::var_os("PATH") {
172 new_path.extend(env::split_paths(&path));
174 new_path.extend(extra);
175 env::join_paths(new_path).unwrap()
178 pub fn remove(sess: &Session, path: &Path) {
179 match fs::remove_file(path) {
182 sess.err(&format!("failed to remove {}: {}",
189 /// Perform the linkage portion of the compilation phase. This will generate all
190 /// of the requested outputs for this compilation session.
191 pub fn link_binary(sess: &Session,
192 trans: &CrateTranslation,
193 outputs: &OutputFilenames,
194 crate_name: &str) -> Vec<PathBuf> {
195 let mut out_filenames = Vec::new();
196 for &crate_type in sess.crate_types.borrow().iter() {
197 // Ignore executable crates if we have -Z no-trans, as they will error.
198 if (sess.opts.debugging_opts.no_trans ||
199 !sess.opts.output_types.should_trans()) &&
200 crate_type == config::CrateTypeExecutable {
204 if invalid_output_for_target(sess, crate_type) {
205 bug!("invalid output type `{:?}` for target os `{}`",
206 crate_type, sess.opts.target_triple);
208 let mut out_files = link_binary_output(sess, trans, crate_type, outputs, crate_name);
209 out_filenames.append(&mut out_files);
212 // Remove the temporary object file and metadata if we aren't saving temps
213 if !sess.opts.cg.save_temps {
214 if sess.opts.output_types.should_trans() {
215 for obj in object_filenames(trans, outputs) {
219 remove(sess, &outputs.with_extension(METADATA_OBJ_NAME));
226 /// Returns default crate type for target
228 /// Default crate type is used when crate type isn't provided neither
229 /// through cmd line arguments nor through crate attributes
231 /// It is CrateTypeExecutable for all platforms but iOS as there is no
232 /// way to run iOS binaries anyway without jailbreaking and
233 /// interaction with Rust code through static library is the only
235 pub fn default_output_for_target(sess: &Session) -> config::CrateType {
236 if !sess.target.target.options.executables {
237 config::CrateTypeStaticlib
239 config::CrateTypeExecutable
243 /// Checks if target supports crate_type as output
244 pub fn invalid_output_for_target(sess: &Session,
245 crate_type: config::CrateType) -> bool {
246 match (sess.target.target.options.dynamic_linking,
247 sess.target.target.options.executables, crate_type) {
248 (false, _, config::CrateTypeCdylib) |
249 (false, _, config::CrateTypeProcMacro) |
250 (false, _, config::CrateTypeDylib) => true,
251 (_, false, config::CrateTypeExecutable) => true,
256 fn is_writeable(p: &Path) -> bool {
259 Ok(m) => !m.permissions().readonly()
263 fn filename_for_metadata(sess: &Session, crate_name: &str, outputs: &OutputFilenames) -> PathBuf {
264 let out_filename = outputs.single_output_file.clone()
267 .join(&format!("lib{}{}.rmeta", crate_name, sess.opts.cg.extra_filename)));
268 check_file_is_writeable(&out_filename, sess);
272 pub fn filename_for_input(sess: &Session,
273 crate_type: config::CrateType,
275 outputs: &OutputFilenames) -> PathBuf {
276 let libname = format!("{}{}", crate_name, sess.opts.cg.extra_filename);
279 config::CrateTypeRlib => {
280 outputs.out_directory.join(&format!("lib{}.rlib", libname))
282 config::CrateTypeCdylib |
283 config::CrateTypeProcMacro |
284 config::CrateTypeDylib => {
285 let (prefix, suffix) = (&sess.target.target.options.dll_prefix,
286 &sess.target.target.options.dll_suffix);
287 outputs.out_directory.join(&format!("{}{}{}", prefix, libname,
290 config::CrateTypeStaticlib => {
291 let (prefix, suffix) = (&sess.target.target.options.staticlib_prefix,
292 &sess.target.target.options.staticlib_suffix);
293 outputs.out_directory.join(&format!("{}{}{}", prefix, libname,
296 config::CrateTypeExecutable => {
297 let suffix = &sess.target.target.options.exe_suffix;
298 let out_filename = outputs.path(OutputType::Exe);
299 if suffix.is_empty() {
300 out_filename.to_path_buf()
302 out_filename.with_extension(&suffix[1..])
308 pub fn each_linked_rlib(sess: &Session,
309 f: &mut FnMut(CrateNum, &Path)) {
310 let crates = sess.cstore.used_crates(LinkagePreference::RequireStatic).into_iter();
311 let fmts = sess.dependency_formats.borrow();
312 let fmts = fmts.get(&config::CrateTypeExecutable)
313 .or_else(|| fmts.get(&config::CrateTypeStaticlib))
314 .or_else(|| fmts.get(&config::CrateTypeCdylib))
315 .or_else(|| fmts.get(&config::CrateTypeProcMacro));
316 let fmts = fmts.unwrap_or_else(|| {
317 bug!("could not find formats for rlibs");
319 for (cnum, path) in crates {
320 match fmts[cnum.as_usize() - 1] {
321 Linkage::NotLinked | Linkage::IncludedFromDylib => continue,
324 let name = sess.cstore.crate_name(cnum).clone();
325 let path = match path {
326 LibSource::Some(p) => p,
327 LibSource::MetadataOnly => {
328 sess.fatal(&format!("could not find rlib for: `{}`, found rmeta (metadata) file",
332 sess.fatal(&format!("could not find rlib for: `{}`", name));
339 fn out_filename(sess: &Session,
340 crate_type: config::CrateType,
341 outputs: &OutputFilenames,
344 let default_filename = filename_for_input(sess, crate_type, crate_name, outputs);
345 let out_filename = outputs.outputs.get(&OutputType::Exe)
346 .and_then(|s| s.to_owned())
347 .or_else(|| outputs.single_output_file.clone())
348 .unwrap_or(default_filename);
350 check_file_is_writeable(&out_filename, sess);
355 // Make sure files are writeable. Mac, FreeBSD, and Windows system linkers
356 // check this already -- however, the Linux linker will happily overwrite a
357 // read-only file. We should be consistent.
358 fn check_file_is_writeable(file: &Path, sess: &Session) {
359 if !is_writeable(file) {
360 sess.fatal(&format!("output file {} is not writeable -- check its \
361 permissions", file.display()));
365 fn link_binary_output(sess: &Session,
366 trans: &CrateTranslation,
367 crate_type: config::CrateType,
368 outputs: &OutputFilenames,
369 crate_name: &str) -> Vec<PathBuf> {
370 let objects = object_filenames(trans, outputs);
372 for file in &objects {
373 check_file_is_writeable(file, sess);
376 let tmpdir = match TempDir::new("rustc") {
377 Ok(tmpdir) => tmpdir,
378 Err(err) => sess.fatal(&format!("couldn't create a temp dir: {}", err)),
381 let mut out_filenames = vec![];
383 if outputs.outputs.contains_key(&OutputType::Metadata) {
384 let out_filename = filename_for_metadata(sess, crate_name, outputs);
385 emit_metadata(sess, trans, &out_filename);
386 out_filenames.push(out_filename);
389 if outputs.outputs.should_trans() {
390 let out_filename = out_filename(sess, crate_type, outputs, crate_name);
392 config::CrateTypeRlib => {
393 link_rlib(sess, Some(trans), &objects, &out_filename,
394 tmpdir.path()).build();
396 config::CrateTypeStaticlib => {
397 link_staticlib(sess, &objects, &out_filename, tmpdir.path());
400 link_natively(sess, crate_type, &objects, &out_filename, trans,
401 outputs, tmpdir.path());
404 out_filenames.push(out_filename);
410 fn object_filenames(trans: &CrateTranslation,
411 outputs: &OutputFilenames)
413 trans.modules.iter().map(|module| {
414 outputs.temp_path(OutputType::Object, Some(&module.name))
418 fn archive_search_paths(sess: &Session) -> Vec<PathBuf> {
419 let mut search = Vec::new();
420 sess.target_filesearch(PathKind::Native).for_each_lib_search_path(|path, _| {
421 search.push(path.to_path_buf());
426 fn archive_config<'a>(sess: &'a Session,
428 input: Option<&Path>) -> ArchiveConfig<'a> {
431 dst: output.to_path_buf(),
432 src: input.map(|p| p.to_path_buf()),
433 lib_search_paths: archive_search_paths(sess),
434 ar_prog: get_ar_prog(sess),
435 command_path: command_path(sess, None),
439 fn emit_metadata<'a>(sess: &'a Session, trans: &CrateTranslation, out_filename: &Path) {
440 let result = fs::File::create(out_filename).and_then(|mut f| {
441 f.write_all(&trans.metadata.raw_data)
444 if let Err(e) = result {
445 sess.fatal(&format!("failed to write {}: {}", out_filename.display(), e));
451 // An rlib in its current incarnation is essentially a renamed .a file. The
452 // rlib primarily contains the object file of the crate, but it also contains
453 // all of the object files from native libraries. This is done by unzipping
454 // native libraries and inserting all of the contents into this archive.
455 fn link_rlib<'a>(sess: &'a Session,
456 trans: Option<&CrateTranslation>, // None == no metadata/bytecode
459 tmpdir: &Path) -> ArchiveBuilder<'a> {
460 info!("preparing rlib from {:?} to {:?}", objects, out_filename);
461 let mut ab = ArchiveBuilder::new(archive_config(sess, out_filename, None));
467 // Note that in this loop we are ignoring the value of `lib.cfg`. That is,
468 // we may not be configured to actually include a static library if we're
469 // adding it here. That's because later when we consume this rlib we'll
470 // decide whether we actually needed the static library or not.
472 // To do this "correctly" we'd need to keep track of which libraries added
473 // which object files to the archive. We don't do that here, however. The
474 // #[link(cfg(..))] feature is unstable, though, and only intended to get
475 // liblibc working. In that sense the check below just indicates that if
476 // there are any libraries we want to omit object files for at link time we
477 // just exclude all custom object files.
479 // Eventually if we want to stabilize or flesh out the #[link(cfg(..))]
480 // feature then we'll need to figure out how to record what objects were
481 // loaded from the libraries found here and then encode that into the
482 // metadata of the rlib we're generating somehow.
483 for lib in sess.cstore.used_libraries() {
485 NativeLibraryKind::NativeStatic => {}
486 NativeLibraryKind::NativeStaticNobundle |
487 NativeLibraryKind::NativeFramework |
488 NativeLibraryKind::NativeUnknown => continue,
490 ab.add_native_library(&lib.name.as_str());
493 // After adding all files to the archive, we need to update the
494 // symbol table of the archive.
497 // Note that it is important that we add all of our non-object "magical
498 // files" *after* all of the object files in the archive. The reason for
499 // this is as follows:
501 // * When performing LTO, this archive will be modified to remove
502 // objects from above. The reason for this is described below.
504 // * When the system linker looks at an archive, it will attempt to
505 // determine the architecture of the archive in order to see whether its
508 // The algorithm for this detection is: iterate over the files in the
509 // archive. Skip magical SYMDEF names. Interpret the first file as an
510 // object file. Read architecture from the object file.
512 // * As one can probably see, if "metadata" and "foo.bc" were placed
513 // before all of the objects, then the architecture of this archive would
514 // not be correctly inferred once 'foo.o' is removed.
516 // Basically, all this means is that this code should not move above the
520 // Instead of putting the metadata in an object file section, rlibs
521 // contain the metadata in a separate file. We use a temp directory
522 // here so concurrent builds in the same directory don't try to use
523 // the same filename for metadata (stomping over one another)
524 let metadata = tmpdir.join(sess.cstore.metadata_filename());
525 emit_metadata(sess, trans, &metadata);
526 ab.add_file(&metadata);
528 // For LTO purposes, the bytecode of this library is also inserted
529 // into the archive. If codegen_units > 1, we insert each of the
532 // Note that we make sure that the bytecode filename in the
533 // archive is never exactly 16 bytes long by adding a 16 byte
534 // extension to it. This is to work around a bug in LLDB that
535 // would cause it to crash if the name of a file in an archive
536 // was exactly 16 bytes.
537 let bc_filename = obj.with_extension("bc");
538 let bc_deflated_filename = tmpdir.join({
539 obj.with_extension("bytecode.deflate").file_name().unwrap()
542 let mut bc_data = Vec::new();
543 match fs::File::open(&bc_filename).and_then(|mut f| {
544 f.read_to_end(&mut bc_data)
547 Err(e) => sess.fatal(&format!("failed to read bytecode: {}",
551 let bc_data_deflated = flate::deflate_bytes(&bc_data);
553 let mut bc_file_deflated = match fs::File::create(&bc_deflated_filename) {
556 sess.fatal(&format!("failed to create compressed \
557 bytecode file: {}", e))
561 match write_rlib_bytecode_object_v1(&mut bc_file_deflated,
565 sess.fatal(&format!("failed to write compressed \
570 ab.add_file(&bc_deflated_filename);
572 // See the bottom of back::write::run_passes for an explanation
573 // of when we do and don't keep .#module-name#.bc files around.
574 let user_wants_numbered_bitcode =
575 sess.opts.output_types.contains_key(&OutputType::Bitcode) &&
576 sess.opts.cg.codegen_units > 1;
577 if !sess.opts.cg.save_temps && !user_wants_numbered_bitcode {
578 remove(sess, &bc_filename);
582 // After adding all files to the archive, we need to update the
583 // symbol table of the archive. This currently dies on macOS (see
584 // #11162), and isn't necessary there anyway
585 if !sess.target.target.options.is_like_osx {
596 fn write_rlib_bytecode_object_v1(writer: &mut Write,
597 bc_data_deflated: &[u8]) -> io::Result<()> {
598 let bc_data_deflated_size: u64 = bc_data_deflated.len() as u64;
600 writer.write_all(RLIB_BYTECODE_OBJECT_MAGIC)?;
601 writer.write_all(&[1, 0, 0, 0])?;
603 (bc_data_deflated_size >> 0) as u8,
604 (bc_data_deflated_size >> 8) as u8,
605 (bc_data_deflated_size >> 16) as u8,
606 (bc_data_deflated_size >> 24) as u8,
607 (bc_data_deflated_size >> 32) as u8,
608 (bc_data_deflated_size >> 40) as u8,
609 (bc_data_deflated_size >> 48) as u8,
610 (bc_data_deflated_size >> 56) as u8,
612 writer.write_all(&bc_data_deflated)?;
614 let number_of_bytes_written_so_far =
615 RLIB_BYTECODE_OBJECT_MAGIC.len() + // magic id
616 mem::size_of_val(&RLIB_BYTECODE_OBJECT_VERSION) + // version
617 mem::size_of_val(&bc_data_deflated_size) + // data size field
618 bc_data_deflated_size as usize; // actual data
620 // If the number of bytes written to the object so far is odd, add a
621 // padding byte to make it even. This works around a crash bug in LLDB
622 // (see issue #15950)
623 if number_of_bytes_written_so_far % 2 == 1 {
624 writer.write_all(&[0])?;
630 // Create a static archive
632 // This is essentially the same thing as an rlib, but it also involves adding
633 // all of the upstream crates' objects into the archive. This will slurp in
634 // all of the native libraries of upstream dependencies as well.
636 // Additionally, there's no way for us to link dynamic libraries, so we warn
637 // about all dynamic library dependencies that they're not linked in.
639 // There's no need to include metadata in a static archive, so ensure to not
640 // link in the metadata object file (and also don't prepare the archive with a
642 fn link_staticlib(sess: &Session, objects: &[PathBuf], out_filename: &Path,
644 let mut ab = link_rlib(sess, None, objects, out_filename, tempdir);
645 let mut all_native_libs = vec![];
647 each_linked_rlib(sess, &mut |cnum, path| {
648 let name = sess.cstore.crate_name(cnum);
649 let native_libs = sess.cstore.native_libraries(cnum);
651 // Here when we include the rlib into our staticlib we need to make a
652 // decision whether to include the extra object files along the way.
653 // These extra object files come from statically included native
654 // libraries, but they may be cfg'd away with #[link(cfg(..))].
656 // This unstable feature, though, only needs liblibc to work. The only
657 // use case there is where musl is statically included in liblibc.rlib,
658 // so if we don't want the included version we just need to skip it. As
659 // a result the logic here is that if *any* linked library is cfg'd away
660 // we just skip all object files.
662 // Clearly this is not sufficient for a general purpose feature, and
663 // we'd want to read from the library's metadata to determine which
664 // object files come from where and selectively skip them.
665 let skip_object_files = native_libs.iter().any(|lib| {
666 lib.kind == NativeLibraryKind::NativeStatic && !relevant_lib(sess, lib)
668 ab.add_rlib(path, &name.as_str(), sess.lto(), skip_object_files).unwrap();
670 all_native_libs.extend(sess.cstore.native_libraries(cnum));
676 if !all_native_libs.is_empty() {
677 sess.note_without_error("link against the following native artifacts when linking against \
678 this static library");
679 sess.note_without_error("the order and any duplication can be significant on some \
680 platforms, and so may need to be preserved");
683 for lib in all_native_libs.iter().filter(|l| relevant_lib(sess, l)) {
684 let name = match lib.kind {
685 NativeLibraryKind::NativeStaticNobundle |
686 NativeLibraryKind::NativeUnknown => "library",
687 NativeLibraryKind::NativeFramework => "framework",
688 // These are included, no need to print them
689 NativeLibraryKind::NativeStatic => continue,
691 sess.note_without_error(&format!("{}: {}", name, lib.name));
695 // Create a dynamic library or executable
697 // This will invoke the system linker/cc to create the resulting file. This
698 // links to all upstream files as well.
699 fn link_natively(sess: &Session,
700 crate_type: config::CrateType,
703 trans: &CrateTranslation,
704 outputs: &OutputFilenames,
706 info!("preparing {:?} from {:?} to {:?}", crate_type, objects, out_filename);
707 let flavor = sess.linker_flavor();
709 // The invocations of cc share some flags across platforms
710 let (pname, mut cmd, extra) = get_linker(sess);
711 cmd.env("PATH", command_path(sess, extra));
713 let root = sess.target_filesearch(PathKind::Native).get_lib_path();
714 if let Some(args) = sess.target.target.options.pre_link_args.get(&flavor) {
718 let pre_link_objects = if crate_type == config::CrateTypeExecutable {
719 &sess.target.target.options.pre_link_objects_exe
721 &sess.target.target.options.pre_link_objects_dll
723 for obj in pre_link_objects {
724 cmd.arg(root.join(obj));
727 if sess.target.target.options.is_like_emscripten {
729 cmd.arg(if sess.panic_strategy() == PanicStrategy::Abort {
730 "DISABLE_EXCEPTION_CATCHING=1"
732 "DISABLE_EXCEPTION_CATCHING=0"
737 let mut linker = trans.linker_info.to_linker(cmd, &sess);
738 link_args(&mut *linker, sess, crate_type, tmpdir,
739 objects, out_filename, outputs, trans);
740 cmd = linker.finalize();
742 if let Some(args) = sess.target.target.options.late_link_args.get(&flavor) {
745 for obj in &sess.target.target.options.post_link_objects {
746 cmd.arg(root.join(obj));
748 if let Some(args) = sess.target.target.options.post_link_args.get(&flavor) {
752 if sess.opts.debugging_opts.print_link_args {
753 println!("{:?}", &cmd);
756 // May have not found libraries in the right formats.
757 sess.abort_if_errors();
759 // Invoke the system linker
761 // Note that there's a terribly awful hack that really shouldn't be present
762 // in any compiler. Here an environment variable is supported to
763 // automatically retry the linker invocation if the linker looks like it
766 // Gee that seems odd, normally segfaults are things we want to know about!
767 // Unfortunately though in rust-lang/rust#38878 we're experiencing the
768 // linker segfaulting on Travis quite a bit which is causing quite a bit of
769 // pain to land PRs when they spuriously fail due to a segfault.
771 // The issue #38878 has some more debugging information on it as well, but
772 // this unfortunately looks like it's just a race condition in macOS's linker
773 // with some thread pool working in the background. It seems that no one
774 // currently knows a fix for this so in the meantime we're left with this...
776 let retry_on_segfault = env::var("RUSTC_RETRY_LINKER_ON_SEGFAULT").is_ok();
781 prog = time(sess.time_passes(), "running linker", || cmd.output());
782 if !retry_on_segfault || i > 3 {
785 let output = match prog {
786 Ok(ref output) => output,
789 if output.status.success() {
792 let mut out = output.stderr.clone();
793 out.extend(&output.stdout);
794 let out = String::from_utf8_lossy(&out);
795 let msg = "clang: error: unable to execute command: \
796 Segmentation fault: 11";
797 if !out.contains(msg) {
801 sess.struct_warn("looks like the linker segfaulted when we tried to \
802 call it, automatically retrying again")
803 .note(&format!("{:?}", cmd))
810 fn escape_string(s: &[u8]) -> String {
811 str::from_utf8(s).map(|s| s.to_owned())
812 .unwrap_or_else(|_| {
813 let mut x = "Non-UTF-8 output: ".to_string();
815 .flat_map(|&b| ascii::escape_default(b))
816 .map(|b| char::from_u32(b as u32).unwrap()));
820 if !prog.status.success() {
821 let mut output = prog.stderr.clone();
822 output.extend_from_slice(&prog.stdout);
823 sess.struct_err(&format!("linking with `{}` failed: {}",
826 .note(&format!("{:?}", &cmd))
827 .note(&escape_string(&output))
829 sess.abort_if_errors();
831 info!("linker stderr:\n{}", escape_string(&prog.stderr));
832 info!("linker stdout:\n{}", escape_string(&prog.stdout));
835 sess.struct_err(&format!("could not exec the linker `{}`: {}", pname, e))
836 .note(&format!("{:?}", &cmd))
838 if sess.target.target.options.is_like_msvc && e.kind() == io::ErrorKind::NotFound {
839 sess.note_without_error("the msvc targets depend on the msvc linker \
840 but `link.exe` was not found");
841 sess.note_without_error("please ensure that VS 2013 or VS 2015 was installed \
842 with the Visual C++ option");
844 sess.abort_if_errors();
849 // On macOS, debuggers need this utility to get run to do some munging of
851 if sess.target.target.options.is_like_osx && sess.opts.debuginfo != NoDebugInfo {
852 match Command::new("dsymutil").arg(out_filename).output() {
854 Err(e) => sess.fatal(&format!("failed to run dsymutil: {}", e)),
859 fn link_args(cmd: &mut Linker,
861 crate_type: config::CrateType,
865 outputs: &OutputFilenames,
866 trans: &CrateTranslation) {
868 // The default library location, we need this to find the runtime.
869 // The location of crates will be determined as needed.
870 let lib_path = sess.target_filesearch(PathKind::All).get_lib_path();
873 let t = &sess.target.target;
875 cmd.include_path(&fix_windows_verbatim_for_gcc(&lib_path));
879 cmd.output_filename(out_filename);
881 if crate_type == config::CrateTypeExecutable &&
882 sess.target.target.options.is_like_windows {
883 if let Some(ref s) = trans.windows_subsystem {
888 // If we're building a dynamic library then some platforms need to make sure
889 // that all symbols are exported correctly from the dynamic library.
890 if crate_type != config::CrateTypeExecutable ||
891 sess.target.target.options.is_like_emscripten {
892 cmd.export_symbols(tmpdir, crate_type);
895 // When linking a dynamic library, we put the metadata into a section of the
896 // executable. This metadata is in a separate object file from the main
897 // object file, so we link that in here.
898 if crate_type == config::CrateTypeDylib ||
899 crate_type == config::CrateTypeProcMacro {
900 cmd.add_object(&outputs.with_extension(METADATA_OBJ_NAME));
903 // Try to strip as much out of the generated object by removing unused
904 // sections if possible. See more comments in linker.rs
905 if !sess.opts.cg.link_dead_code {
906 let keep_metadata = crate_type == config::CrateTypeDylib;
907 cmd.gc_sections(keep_metadata);
910 let used_link_args = sess.cstore.used_link_args();
912 if crate_type == config::CrateTypeExecutable &&
913 t.options.position_independent_executables {
914 let empty_vec = Vec::new();
915 let args = sess.opts.cg.link_args.as_ref().unwrap_or(&empty_vec);
916 let more_args = &sess.opts.cg.link_arg;
917 let mut args = args.iter().chain(more_args.iter()).chain(used_link_args.iter());
919 if get_reloc_model(sess) == llvm::RelocMode::PIC
920 && !args.any(|x| *x == "-static") {
921 cmd.position_independent_executable();
925 // Pass optimization flags down to the linker.
928 // Pass debuginfo flags down to the linker.
931 // We want to prevent the compiler from accidentally leaking in any system
932 // libraries, so we explicitly ask gcc to not link to any libraries by
933 // default. Note that this does not happen for windows because windows pulls
934 // in some large number of libraries and I couldn't quite figure out which
936 if t.options.no_default_libraries {
937 cmd.no_default_libraries();
940 // Take careful note of the ordering of the arguments we pass to the linker
941 // here. Linkers will assume that things on the left depend on things to the
942 // right. Things on the right cannot depend on things on the left. This is
943 // all formally implemented in terms of resolving symbols (libs on the right
944 // resolve unknown symbols of libs on the left, but not vice versa).
946 // For this reason, we have organized the arguments we pass to the linker as
949 // 1. The local object that LLVM just generated
950 // 2. Local native libraries
951 // 3. Upstream rust libraries
952 // 4. Upstream native libraries
954 // The rationale behind this ordering is that those items lower down in the
955 // list can't depend on items higher up in the list. For example nothing can
956 // depend on what we just generated (e.g. that'd be a circular dependency).
957 // Upstream rust libraries are not allowed to depend on our local native
958 // libraries as that would violate the structure of the DAG, in that
959 // scenario they are required to link to them as well in a shared fashion.
961 // Note that upstream rust libraries may contain native dependencies as
962 // well, but they also can't depend on what we just started to add to the
963 // link line. And finally upstream native libraries can't depend on anything
964 // in this DAG so far because they're only dylibs and dylibs can only depend
965 // on other dylibs (e.g. other native deps).
966 add_local_native_libraries(cmd, sess);
967 add_upstream_rust_crates(cmd, sess, crate_type, tmpdir);
968 add_upstream_native_libraries(cmd, sess, crate_type);
970 // # Telling the linker what we're doing
972 if crate_type != config::CrateTypeExecutable {
973 cmd.build_dylib(out_filename);
976 // FIXME (#2397): At some point we want to rpath our guesses as to
977 // where extern libraries might live, based on the
978 // addl_lib_search_paths
979 if sess.opts.cg.rpath {
980 let sysroot = sess.sysroot();
981 let target_triple = &sess.opts.target_triple;
982 let mut get_install_prefix_lib_path = || {
983 let install_prefix = option_env!("CFG_PREFIX").expect("CFG_PREFIX");
984 let tlib = filesearch::relative_target_lib_path(sysroot, target_triple);
985 let mut path = PathBuf::from(install_prefix);
990 let mut rpath_config = RPathConfig {
991 used_crates: sess.cstore.used_crates(LinkagePreference::RequireDynamic),
992 out_filename: out_filename.to_path_buf(),
993 has_rpath: sess.target.target.options.has_rpath,
994 is_like_osx: sess.target.target.options.is_like_osx,
995 linker_is_gnu: sess.target.target.options.linker_is_gnu,
996 get_install_prefix_lib_path: &mut get_install_prefix_lib_path,
998 cmd.args(&rpath::get_rpath_flags(&mut rpath_config));
1001 // Finally add all the linker arguments provided on the command line along
1002 // with any #[link_args] attributes found inside the crate
1003 if let Some(ref args) = sess.opts.cg.link_args {
1006 cmd.args(&sess.opts.cg.link_arg);
1007 cmd.args(&used_link_args);
1010 // # Native library linking
1012 // User-supplied library search paths (-L on the command line). These are
1013 // the same paths used to find Rust crates, so some of them may have been
1014 // added already by the previous crate linking code. This only allows them
1015 // to be found at compile time so it is still entirely up to outside
1016 // forces to make sure that library can be found at runtime.
1018 // Also note that the native libraries linked here are only the ones located
1019 // in the current crate. Upstream crates with native library dependencies
1020 // may have their native library pulled in above.
1021 fn add_local_native_libraries(cmd: &mut Linker, sess: &Session) {
1022 sess.target_filesearch(PathKind::All).for_each_lib_search_path(|path, k| {
1024 PathKind::Framework => { cmd.framework_path(path); }
1025 _ => { cmd.include_path(&fix_windows_verbatim_for_gcc(path)); }
1029 let relevant_libs = sess.cstore.used_libraries().into_iter().filter(|l| {
1030 relevant_lib(sess, l)
1033 let search_path = archive_search_paths(sess);
1034 for lib in relevant_libs {
1036 NativeLibraryKind::NativeUnknown => cmd.link_dylib(&lib.name.as_str()),
1037 NativeLibraryKind::NativeFramework => cmd.link_framework(&lib.name.as_str()),
1038 NativeLibraryKind::NativeStaticNobundle => cmd.link_staticlib(&lib.name.as_str()),
1039 NativeLibraryKind::NativeStatic => cmd.link_whole_staticlib(&lib.name.as_str(),
1045 // # Rust Crate linking
1047 // Rust crates are not considered at all when creating an rlib output. All
1048 // dependencies will be linked when producing the final output (instead of
1049 // the intermediate rlib version)
1050 fn add_upstream_rust_crates(cmd: &mut Linker,
1052 crate_type: config::CrateType,
1054 // All of the heavy lifting has previously been accomplished by the
1055 // dependency_format module of the compiler. This is just crawling the
1056 // output of that module, adding crates as necessary.
1058 // Linking to a rlib involves just passing it to the linker (the linker
1059 // will slurp up the object files inside), and linking to a dynamic library
1060 // involves just passing the right -l flag.
1062 let formats = sess.dependency_formats.borrow();
1063 let data = formats.get(&crate_type).unwrap();
1065 // Invoke get_used_crates to ensure that we get a topological sorting of
1067 let deps = sess.cstore.used_crates(LinkagePreference::RequireDynamic);
1069 let mut compiler_builtins = None;
1071 for &(cnum, _) in &deps {
1072 // We may not pass all crates through to the linker. Some crates may
1073 // appear statically in an existing dylib, meaning we'll pick up all the
1074 // symbols from the dylib.
1075 let src = sess.cstore.used_crate_source(cnum);
1076 match data[cnum.as_usize() - 1] {
1077 _ if sess.cstore.is_sanitizer_runtime(cnum) => {
1078 link_sanitizer_runtime(cmd, sess, tmpdir, cnum);
1080 // compiler-builtins are always placed last to ensure that they're
1081 // linked correctly.
1082 _ if sess.cstore.is_compiler_builtins(cnum) => {
1083 assert!(compiler_builtins.is_none());
1084 compiler_builtins = Some(cnum);
1086 Linkage::NotLinked |
1087 Linkage::IncludedFromDylib => {}
1088 Linkage::Static => {
1089 add_static_crate(cmd, sess, tmpdir, crate_type, cnum);
1091 Linkage::Dynamic => {
1092 add_dynamic_crate(cmd, sess, &src.dylib.unwrap().0)
1097 // compiler-builtins are always placed last to ensure that they're
1098 // linked correctly.
1099 // We must always link the `compiler_builtins` crate statically. Even if it
1100 // was already "included" in a dylib (e.g. `libstd` when `-C prefer-dynamic`
1102 if let Some(cnum) = compiler_builtins {
1103 add_static_crate(cmd, sess, tmpdir, crate_type, cnum);
1106 // Converts a library file-stem into a cc -l argument
1107 fn unlib<'a>(config: &config::Config, stem: &'a str) -> &'a str {
1108 if stem.starts_with("lib") && !config.target.options.is_like_windows {
1115 // We must link the sanitizer runtime using -Wl,--whole-archive but since
1116 // it's packed in a .rlib, it contains stuff that are not objects that will
1117 // make the linker error. So we must remove those bits from the .rlib before
1119 fn link_sanitizer_runtime(cmd: &mut Linker,
1123 let src = sess.cstore.used_crate_source(cnum);
1124 let cratepath = &src.rlib.unwrap().0;
1126 if sess.target.target.options.is_like_osx {
1127 // On Apple platforms, the sanitizer is always built as a dylib, and
1128 // LLVM will link to `@rpath/*.dylib`, so we need to specify an
1129 // rpath to the library as well (the rpath should be absolute, see
1130 // PR #41352 for details).
1132 // FIXME: Remove this logic into librustc_*san once Cargo supports it
1133 let rpath = cratepath.parent().unwrap();
1134 let rpath = rpath.to_str().expect("non-utf8 component in path");
1135 cmd.args(&["-Wl,-rpath".into(), "-Xlinker".into(), rpath.into()]);
1138 let dst = tmpdir.join(cratepath.file_name().unwrap());
1139 let cfg = archive_config(sess, &dst, Some(cratepath));
1140 let mut archive = ArchiveBuilder::new(cfg);
1141 archive.update_symbols();
1143 for f in archive.src_files() {
1144 if f.ends_with("bytecode.deflate") ||
1145 f == sess.cstore.metadata_filename() {
1146 archive.remove_file(&f);
1153 cmd.link_whole_rlib(&dst);
1156 // Adds the static "rlib" versions of all crates to the command line.
1157 // There's a bit of magic which happens here specifically related to LTO and
1158 // dynamic libraries. Specifically:
1160 // * For LTO, we remove upstream object files.
1161 // * For dylibs we remove metadata and bytecode from upstream rlibs
1163 // When performing LTO, almost(*) all of the bytecode from the upstream
1164 // libraries has already been included in our object file output. As a
1165 // result we need to remove the object files in the upstream libraries so
1166 // the linker doesn't try to include them twice (or whine about duplicate
1167 // symbols). We must continue to include the rest of the rlib, however, as
1168 // it may contain static native libraries which must be linked in.
1170 // (*) Crates marked with `#![no_builtins]` don't participate in LTO and
1171 // their bytecode wasn't included. The object files in those libraries must
1172 // still be passed to the linker.
1174 // When making a dynamic library, linkers by default don't include any
1175 // object files in an archive if they're not necessary to resolve the link.
1176 // We basically want to convert the archive (rlib) to a dylib, though, so we
1177 // *do* want everything included in the output, regardless of whether the
1178 // linker thinks it's needed or not. As a result we must use the
1179 // --whole-archive option (or the platform equivalent). When using this
1180 // option the linker will fail if there are non-objects in the archive (such
1181 // as our own metadata and/or bytecode). All in all, for rlibs to be
1182 // entirely included in dylibs, we need to remove all non-object files.
1184 // Note, however, that if we're not doing LTO or we're not producing a dylib
1185 // (aka we're making an executable), we can just pass the rlib blindly to
1186 // the linker (fast) because it's fine if it's not actually included as
1187 // we're at the end of the dependency chain.
1188 fn add_static_crate(cmd: &mut Linker,
1191 crate_type: config::CrateType,
1193 let src = sess.cstore.used_crate_source(cnum);
1194 let cratepath = &src.rlib.unwrap().0;
1196 // See the comment above in `link_staticlib` and `link_rlib` for why if
1197 // there's a static library that's not relevant we skip all object
1199 let native_libs = sess.cstore.native_libraries(cnum);
1200 let skip_native = native_libs.iter().any(|lib| {
1201 lib.kind == NativeLibraryKind::NativeStatic && !relevant_lib(sess, lib)
1204 if !sess.lto() && crate_type != config::CrateTypeDylib && !skip_native {
1205 cmd.link_rlib(&fix_windows_verbatim_for_gcc(cratepath));
1209 let dst = tmpdir.join(cratepath.file_name().unwrap());
1210 let name = cratepath.file_name().unwrap().to_str().unwrap();
1211 let name = &name[3..name.len() - 5]; // chop off lib/.rlib
1213 time(sess.time_passes(), &format!("altering {}.rlib", name), || {
1214 let cfg = archive_config(sess, &dst, Some(cratepath));
1215 let mut archive = ArchiveBuilder::new(cfg);
1216 archive.update_symbols();
1218 let mut any_objects = false;
1219 for f in archive.src_files() {
1220 if f.ends_with("bytecode.deflate") ||
1221 f == sess.cstore.metadata_filename() {
1222 archive.remove_file(&f);
1226 let canonical = f.replace("-", "_");
1227 let canonical_name = name.replace("-", "_");
1229 let is_rust_object =
1230 canonical.starts_with(&canonical_name) && {
1231 let num = &f[name.len()..f.len() - 2];
1232 num.len() > 0 && num[1..].parse::<u32>().is_ok()
1235 // If we've been requested to skip all native object files
1236 // (those not generated by the rust compiler) then we can skip
1237 // this file. See above for why we may want to do this.
1238 let skip_because_cfg_say_so = skip_native && !is_rust_object;
1240 // If we're performing LTO and this is a rust-generated object
1241 // file, then we don't need the object file as it's part of the
1242 // LTO module. Note that `#![no_builtins]` is excluded from LTO,
1243 // though, so we let that object file slide.
1244 let skip_because_lto = sess.lto() && is_rust_object &&
1245 !sess.cstore.is_no_builtins(cnum);
1247 if skip_because_cfg_say_so || skip_because_lto {
1248 archive.remove_file(&f);
1259 // If we're creating a dylib, then we need to include the
1260 // whole of each object in our archive into that artifact. This is
1261 // because a `dylib` can be reused as an intermediate artifact.
1263 // Note, though, that we don't want to include the whole of a
1264 // compiler-builtins crate (e.g. compiler-rt) because it'll get
1265 // repeatedly linked anyway.
1266 if crate_type == config::CrateTypeDylib &&
1267 !sess.cstore.is_compiler_builtins(cnum) {
1268 cmd.link_whole_rlib(&fix_windows_verbatim_for_gcc(&dst));
1270 cmd.link_rlib(&fix_windows_verbatim_for_gcc(&dst));
1275 // Same thing as above, but for dynamic crates instead of static crates.
1276 fn add_dynamic_crate(cmd: &mut Linker, sess: &Session, cratepath: &Path) {
1277 // If we're performing LTO, then it should have been previously required
1278 // that all upstream rust dependencies were available in an rlib format.
1279 assert!(!sess.lto());
1281 // Just need to tell the linker about where the library lives and
1283 let parent = cratepath.parent();
1284 if let Some(dir) = parent {
1285 cmd.include_path(&fix_windows_verbatim_for_gcc(dir));
1287 let filestem = cratepath.file_stem().unwrap().to_str().unwrap();
1288 cmd.link_rust_dylib(&unlib(&sess.target, filestem),
1289 parent.unwrap_or(Path::new("")));
1293 // Link in all of our upstream crates' native dependencies. Remember that
1294 // all of these upstream native dependencies are all non-static
1295 // dependencies. We've got two cases then:
1297 // 1. The upstream crate is an rlib. In this case we *must* link in the
1298 // native dependency because the rlib is just an archive.
1300 // 2. The upstream crate is a dylib. In order to use the dylib, we have to
1301 // have the dependency present on the system somewhere. Thus, we don't
1302 // gain a whole lot from not linking in the dynamic dependency to this
1305 // The use case for this is a little subtle. In theory the native
1306 // dependencies of a crate are purely an implementation detail of the crate
1307 // itself, but the problem arises with generic and inlined functions. If a
1308 // generic function calls a native function, then the generic function must
1309 // be instantiated in the target crate, meaning that the native symbol must
1310 // also be resolved in the target crate.
1311 fn add_upstream_native_libraries(cmd: &mut Linker, sess: &Session, crate_type: config::CrateType) {
1312 // Be sure to use a topological sorting of crates because there may be
1313 // interdependencies between native libraries. When passing -nodefaultlibs,
1314 // for example, almost all native libraries depend on libc, so we have to
1315 // make sure that's all the way at the right (liblibc is near the base of
1316 // the dependency chain).
1318 // This passes RequireStatic, but the actual requirement doesn't matter,
1319 // we're just getting an ordering of crate numbers, we're not worried about
1321 let formats = sess.dependency_formats.borrow();
1322 let data = formats.get(&crate_type).unwrap();
1324 let crates = sess.cstore.used_crates(LinkagePreference::RequireStatic);
1325 for (cnum, _) in crates {
1326 for lib in sess.cstore.native_libraries(cnum) {
1327 if !relevant_lib(sess, &lib) {
1331 NativeLibraryKind::NativeUnknown => cmd.link_dylib(&lib.name.as_str()),
1332 NativeLibraryKind::NativeFramework => cmd.link_framework(&lib.name.as_str()),
1333 NativeLibraryKind::NativeStaticNobundle => {
1334 // Link "static-nobundle" native libs only if the crate they originate from
1335 // is being linked statically to the current crate. If it's linked dynamically
1336 // or is an rlib already included via some other dylib crate, the symbols from
1337 // native libs will have already been included in that dylib.
1338 if data[cnum.as_usize() - 1] == Linkage::Static {
1339 cmd.link_staticlib(&lib.name.as_str())
1342 // ignore statically included native libraries here as we've
1343 // already included them when we included the rust library
1345 NativeLibraryKind::NativeStatic => {}
1351 fn relevant_lib(sess: &Session, lib: &NativeLibrary) -> bool {
1353 Some(ref cfg) => attr::cfg_matches(cfg, &sess.parse_sess, None),