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 extern crate rustc_trans_utils;
13 use super::archive::{ArchiveBuilder, ArchiveConfig};
14 use super::linker::Linker;
15 use super::command::Command;
16 use super::rpath::RPathConfig;
18 use metadata::METADATA_FILENAME;
19 use rustc::session::config::{self, NoDebugInfo, OutputFilenames, OutputType, PrintRequest};
20 use rustc::session::filesearch;
21 use rustc::session::search_paths::PathKind;
22 use rustc::session::Session;
23 use rustc::middle::cstore::{LinkMeta, 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::dep_graph::{DepKind, 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, RelroLevel};
33 use rustc_incremental::IncrementalHashesMap;
34 use context::get_reloc_model;
40 use std::ffi::OsString;
42 use std::fs::{self, File};
43 use std::io::{self, Read, Write, BufWriter};
45 use std::path::{Path, PathBuf};
46 use std::process::{Output, Stdio};
48 use flate2::Compression;
49 use flate2::write::DeflateEncoder;
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 // same as for metadata above, but for allocator shim
60 pub const ALLOCATOR_MODULE_NAME: &'static str = "crate.allocator";
61 pub const ALLOCATOR_OBJ_NAME: &'static str = "crate.allocator.o";
63 // RLIB LLVM-BYTECODE OBJECT LAYOUT
66 // 0..10 "RUST_OBJECT" encoded in ASCII
67 // 11..14 format version as little-endian u32
68 // 15..22 size in bytes of deflate compressed LLVM bitcode as
70 // 23.. compressed LLVM bitcode
72 // This is the "magic number" expected at the beginning of a LLVM bytecode
74 pub const RLIB_BYTECODE_OBJECT_MAGIC: &'static [u8] = b"RUST_OBJECT";
76 // The version number this compiler will write to bytecode objects in rlibs
77 pub const RLIB_BYTECODE_OBJECT_VERSION: u32 = 1;
79 // The offset in bytes the bytecode object format version number can be found at
80 pub const RLIB_BYTECODE_OBJECT_VERSION_OFFSET: usize = 11;
82 // The offset in bytes the size of the compressed bytecode can be found at in
84 pub const RLIB_BYTECODE_OBJECT_V1_DATASIZE_OFFSET: usize =
85 RLIB_BYTECODE_OBJECT_VERSION_OFFSET + 4;
87 // The offset in bytes the compressed LLVM bytecode can be found at in format
89 pub const RLIB_BYTECODE_OBJECT_V1_DATA_OFFSET: usize =
90 RLIB_BYTECODE_OBJECT_V1_DATASIZE_OFFSET + 8;
92 pub use self::rustc_trans_utils::link::{find_crate_name, filename_for_input,
93 default_output_for_target, invalid_output_for_target};
95 pub fn build_link_meta(incremental_hashes_map: &IncrementalHashesMap) -> LinkMeta {
96 let krate_dep_node = &DepNode::new_no_params(DepKind::Krate);
98 crate_hash: Svh::new(incremental_hashes_map[krate_dep_node].to_smaller_hash()),
104 // The third parameter is for env vars, used on windows to set up the
105 // path for MSVC to find its DLLs, and gcc to find its bundled
107 pub fn get_linker(sess: &Session) -> (String, Command, Vec<(OsString, OsString)>) {
108 let envs = vec![("PATH".into(), command_path(sess))];
110 if let Some(ref linker) = sess.opts.cg.linker {
111 (linker.clone(), Command::new(linker), envs)
112 } else if sess.target.target.options.is_like_msvc {
113 let (cmd, envs) = msvc_link_exe_cmd(sess);
114 ("link.exe".to_string(), cmd, envs)
116 let linker = &sess.target.target.options.linker;
117 (linker.clone(), Command::new(&linker), envs)
122 pub fn msvc_link_exe_cmd(sess: &Session) -> (Command, Vec<(OsString, OsString)>) {
123 use gcc::windows_registry;
125 let target = &sess.opts.target_triple;
126 let tool = windows_registry::find_tool(target, "link.exe");
128 if let Some(tool) = tool {
129 let mut cmd = Command::new(tool.path());
130 cmd.args(tool.args());
131 for &(ref k, ref v) in tool.env() {
134 let envs = tool.env().to_vec();
137 debug!("Failed to locate linker.");
138 (Command::new("link.exe"), vec![])
143 pub fn msvc_link_exe_cmd(_sess: &Session) -> (Command, Vec<(OsString, OsString)>) {
144 (Command::new("link.exe"), vec![])
147 fn command_path(sess: &Session) -> OsString {
148 // The compiler's sysroot often has some bundled tools, so add it to the
149 // PATH for the child.
150 let mut new_path = sess.host_filesearch(PathKind::All)
151 .get_tools_search_paths();
152 if let Some(path) = env::var_os("PATH") {
153 new_path.extend(env::split_paths(&path));
155 env::join_paths(new_path).unwrap()
158 pub fn remove(sess: &Session, path: &Path) {
159 match fs::remove_file(path) {
162 sess.err(&format!("failed to remove {}: {}",
169 /// Perform the linkage portion of the compilation phase. This will generate all
170 /// of the requested outputs for this compilation session.
171 pub fn link_binary(sess: &Session,
172 trans: &CrateTranslation,
173 outputs: &OutputFilenames,
174 crate_name: &str) -> Vec<PathBuf> {
175 let mut out_filenames = Vec::new();
176 for &crate_type in sess.crate_types.borrow().iter() {
177 // Ignore executable crates if we have -Z no-trans, as they will error.
178 if (sess.opts.debugging_opts.no_trans ||
179 !sess.opts.output_types.should_trans()) &&
180 crate_type == config::CrateTypeExecutable {
184 if invalid_output_for_target(sess, crate_type) {
185 bug!("invalid output type `{:?}` for target os `{}`",
186 crate_type, sess.opts.target_triple);
188 let mut out_files = link_binary_output(sess,
193 out_filenames.append(&mut out_files);
196 // Remove the temporary object file and metadata if we aren't saving temps
197 if !sess.opts.cg.save_temps {
198 if sess.opts.output_types.should_trans() {
199 for obj in object_filenames(trans, outputs) {
203 remove(sess, &outputs.with_extension(METADATA_OBJ_NAME));
204 if trans.allocator_module.is_some() {
205 remove(sess, &outputs.with_extension(ALLOCATOR_OBJ_NAME));
212 fn is_writeable(p: &Path) -> bool {
215 Ok(m) => !m.permissions().readonly()
219 fn filename_for_metadata(sess: &Session, crate_name: &str, outputs: &OutputFilenames) -> PathBuf {
220 let out_filename = outputs.single_output_file.clone()
223 .join(&format!("lib{}{}.rmeta", crate_name, sess.opts.cg.extra_filename)));
224 check_file_is_writeable(&out_filename, sess);
228 pub fn each_linked_rlib(sess: &Session,
230 f: &mut FnMut(CrateNum, &Path)) -> Result<(), String> {
231 let crates = info.used_crates_static.iter();
232 let fmts = sess.dependency_formats.borrow();
233 let fmts = fmts.get(&config::CrateTypeExecutable)
234 .or_else(|| fmts.get(&config::CrateTypeStaticlib))
235 .or_else(|| fmts.get(&config::CrateTypeCdylib))
236 .or_else(|| fmts.get(&config::CrateTypeProcMacro));
237 let fmts = match fmts {
239 None => return Err(format!("could not find formats for rlibs"))
241 for &(cnum, ref path) in crates {
242 match fmts.get(cnum.as_usize() - 1) {
243 Some(&Linkage::NotLinked) |
244 Some(&Linkage::IncludedFromDylib) => continue,
246 None => return Err(format!("could not find formats for rlibs"))
248 let name = &info.crate_name[&cnum];
249 let path = match *path {
250 LibSource::Some(ref p) => p,
251 LibSource::MetadataOnly => {
252 return Err(format!("could not find rlib for: `{}`, found rmeta (metadata) file",
256 return Err(format!("could not find rlib for: `{}`", name))
264 /// Returns a boolean indicating whether the specified crate should be ignored
267 /// Crates ignored during LTO are not lumped together in the "massive object
268 /// file" that we create and are linked in their normal rlib states. See
269 /// comments below for what crates do not participate in LTO.
271 /// It's unusual for a crate to not participate in LTO. Typically only
272 /// compiler-specific and unstable crates have a reason to not participate in
274 pub fn ignored_for_lto(info: &CrateInfo, cnum: CrateNum) -> bool {
275 // `#![no_builtins]` crates don't participate in LTO because the state
276 // of builtins gets messed up (our crate isn't tagged with no builtins).
277 // Similarly `#![compiler_builtins]` doesn't participate because we want
279 info.is_no_builtins.contains(&cnum) || info.compiler_builtins == Some(cnum)
282 fn out_filename(sess: &Session,
283 crate_type: config::CrateType,
284 outputs: &OutputFilenames,
287 let default_filename = filename_for_input(sess, crate_type, crate_name, outputs);
288 let out_filename = outputs.outputs.get(&OutputType::Exe)
289 .and_then(|s| s.to_owned())
290 .or_else(|| outputs.single_output_file.clone())
291 .unwrap_or(default_filename);
293 check_file_is_writeable(&out_filename, sess);
298 // Make sure files are writeable. Mac, FreeBSD, and Windows system linkers
299 // check this already -- however, the Linux linker will happily overwrite a
300 // read-only file. We should be consistent.
301 fn check_file_is_writeable(file: &Path, sess: &Session) {
302 if !is_writeable(file) {
303 sess.fatal(&format!("output file {} is not writeable -- check its \
304 permissions", file.display()));
308 fn link_binary_output(sess: &Session,
309 trans: &CrateTranslation,
310 crate_type: config::CrateType,
311 outputs: &OutputFilenames,
312 crate_name: &str) -> Vec<PathBuf> {
313 let objects = object_filenames(trans, outputs);
315 for file in &objects {
316 check_file_is_writeable(file, sess);
319 let tmpdir = match TempDir::new("rustc") {
320 Ok(tmpdir) => tmpdir,
321 Err(err) => sess.fatal(&format!("couldn't create a temp dir: {}", err)),
324 let mut out_filenames = vec![];
326 if outputs.outputs.contains_key(&OutputType::Metadata) {
327 let out_filename = filename_for_metadata(sess, crate_name, outputs);
328 emit_metadata(sess, trans, &out_filename);
329 out_filenames.push(out_filename);
332 if outputs.outputs.should_trans() {
333 let out_filename = out_filename(sess, crate_type, outputs, crate_name);
335 config::CrateTypeRlib => {
342 tmpdir.path()).build();
344 config::CrateTypeStaticlib => {
353 link_natively(sess, crate_type, &objects, &out_filename,
354 trans, outputs, tmpdir.path());
357 out_filenames.push(out_filename);
360 if sess.opts.cg.save_temps {
361 let _ = tmpdir.into_path();
367 fn object_filenames(trans: &CrateTranslation,
368 outputs: &OutputFilenames)
370 trans.modules.iter().map(|module| {
371 outputs.temp_path(OutputType::Object, Some(&module.name))
375 fn archive_search_paths(sess: &Session) -> Vec<PathBuf> {
376 let mut search = Vec::new();
377 sess.target_filesearch(PathKind::Native).for_each_lib_search_path(|path, _| {
378 search.push(path.to_path_buf());
383 fn archive_config<'a>(sess: &'a Session,
385 input: Option<&Path>) -> ArchiveConfig<'a> {
388 dst: output.to_path_buf(),
389 src: input.map(|p| p.to_path_buf()),
390 lib_search_paths: archive_search_paths(sess),
394 fn emit_metadata<'a>(sess: &'a Session, trans: &CrateTranslation, out_filename: &Path) {
395 let result = fs::File::create(out_filename).and_then(|mut f| {
396 f.write_all(&trans.metadata.raw_data)
399 if let Err(e) = result {
400 sess.fatal(&format!("failed to write {}: {}", out_filename.display(), e));
411 // An rlib in its current incarnation is essentially a renamed .a file. The
412 // rlib primarily contains the object file of the crate, but it also contains
413 // all of the object files from native libraries. This is done by unzipping
414 // native libraries and inserting all of the contents into this archive.
415 fn link_rlib<'a>(sess: &'a Session,
416 trans: &CrateTranslation,
419 outputs: &OutputFilenames,
421 tmpdir: &Path) -> ArchiveBuilder<'a> {
422 info!("preparing rlib from {:?} to {:?}", objects, out_filename);
423 let mut ab = ArchiveBuilder::new(archive_config(sess, out_filename, None));
429 // Note that in this loop we are ignoring the value of `lib.cfg`. That is,
430 // we may not be configured to actually include a static library if we're
431 // adding it here. That's because later when we consume this rlib we'll
432 // decide whether we actually needed the static library or not.
434 // To do this "correctly" we'd need to keep track of which libraries added
435 // which object files to the archive. We don't do that here, however. The
436 // #[link(cfg(..))] feature is unstable, though, and only intended to get
437 // liblibc working. In that sense the check below just indicates that if
438 // there are any libraries we want to omit object files for at link time we
439 // just exclude all custom object files.
441 // Eventually if we want to stabilize or flesh out the #[link(cfg(..))]
442 // feature then we'll need to figure out how to record what objects were
443 // loaded from the libraries found here and then encode that into the
444 // metadata of the rlib we're generating somehow.
445 for lib in trans.crate_info.used_libraries.iter() {
447 NativeLibraryKind::NativeStatic => {}
448 NativeLibraryKind::NativeStaticNobundle |
449 NativeLibraryKind::NativeFramework |
450 NativeLibraryKind::NativeUnknown => continue,
452 ab.add_native_library(&lib.name.as_str());
455 // After adding all files to the archive, we need to update the
456 // symbol table of the archive.
459 // Note that it is important that we add all of our non-object "magical
460 // files" *after* all of the object files in the archive. The reason for
461 // this is as follows:
463 // * When performing LTO, this archive will be modified to remove
464 // objects from above. The reason for this is described below.
466 // * When the system linker looks at an archive, it will attempt to
467 // determine the architecture of the archive in order to see whether its
470 // The algorithm for this detection is: iterate over the files in the
471 // archive. Skip magical SYMDEF names. Interpret the first file as an
472 // object file. Read architecture from the object file.
474 // * As one can probably see, if "metadata" and "foo.bc" were placed
475 // before all of the objects, then the architecture of this archive would
476 // not be correctly inferred once 'foo.o' is removed.
478 // Basically, all this means is that this code should not move above the
481 RlibFlavor::Normal => {
482 // Instead of putting the metadata in an object file section, rlibs
483 // contain the metadata in a separate file. We use a temp directory
484 // here so concurrent builds in the same directory don't try to use
485 // the same filename for metadata (stomping over one another)
486 let metadata = tmpdir.join(METADATA_FILENAME);
487 emit_metadata(sess, trans, &metadata);
488 ab.add_file(&metadata);
490 // For LTO purposes, the bytecode of this library is also inserted
491 // into the archive. If codegen_units > 1, we insert each of the
494 // Note that we make sure that the bytecode filename in the
495 // archive is never exactly 16 bytes long by adding a 16 byte
496 // extension to it. This is to work around a bug in LLDB that
497 // would cause it to crash if the name of a file in an archive
498 // was exactly 16 bytes.
499 let bc_filename = obj.with_extension("bc");
500 let bc_deflated_filename = tmpdir.join({
501 obj.with_extension("bytecode.deflate").file_name().unwrap()
504 let mut bc_data = Vec::new();
505 match fs::File::open(&bc_filename).and_then(|mut f| {
506 f.read_to_end(&mut bc_data)
509 Err(e) => sess.fatal(&format!("failed to read bytecode: {}",
513 let mut bc_data_deflated = Vec::new();
514 DeflateEncoder::new(&mut bc_data_deflated, Compression::Fast)
515 .write_all(&bc_data).unwrap();
517 let mut bc_file_deflated = match fs::File::create(&bc_deflated_filename) {
520 sess.fatal(&format!("failed to create compressed \
521 bytecode file: {}", e))
525 match write_rlib_bytecode_object_v1(&mut bc_file_deflated,
529 sess.fatal(&format!("failed to write compressed \
534 ab.add_file(&bc_deflated_filename);
536 // See the bottom of back::write::run_passes for an explanation
537 // of when we do and don't keep .#module-name#.bc files around.
538 let user_wants_numbered_bitcode =
539 sess.opts.output_types.contains_key(&OutputType::Bitcode) &&
540 sess.opts.cg.codegen_units > 1;
541 if !sess.opts.cg.save_temps && !user_wants_numbered_bitcode {
542 remove(sess, &bc_filename);
546 // After adding all files to the archive, we need to update the
547 // symbol table of the archive. This currently dies on macOS (see
548 // #11162), and isn't necessary there anyway
549 if !sess.target.target.options.is_like_osx {
554 RlibFlavor::StaticlibBase => {
555 if trans.allocator_module.is_some() {
556 ab.add_file(&outputs.with_extension(ALLOCATOR_OBJ_NAME));
564 fn write_rlib_bytecode_object_v1(writer: &mut Write,
565 bc_data_deflated: &[u8]) -> io::Result<()> {
566 let bc_data_deflated_size: u64 = bc_data_deflated.len() as u64;
568 writer.write_all(RLIB_BYTECODE_OBJECT_MAGIC)?;
569 writer.write_all(&[1, 0, 0, 0])?;
571 (bc_data_deflated_size >> 0) as u8,
572 (bc_data_deflated_size >> 8) as u8,
573 (bc_data_deflated_size >> 16) as u8,
574 (bc_data_deflated_size >> 24) as u8,
575 (bc_data_deflated_size >> 32) as u8,
576 (bc_data_deflated_size >> 40) as u8,
577 (bc_data_deflated_size >> 48) as u8,
578 (bc_data_deflated_size >> 56) as u8,
580 writer.write_all(&bc_data_deflated)?;
582 let number_of_bytes_written_so_far =
583 RLIB_BYTECODE_OBJECT_MAGIC.len() + // magic id
584 mem::size_of_val(&RLIB_BYTECODE_OBJECT_VERSION) + // version
585 mem::size_of_val(&bc_data_deflated_size) + // data size field
586 bc_data_deflated_size as usize; // actual data
588 // If the number of bytes written to the object so far is odd, add a
589 // padding byte to make it even. This works around a crash bug in LLDB
590 // (see issue #15950)
591 if number_of_bytes_written_so_far % 2 == 1 {
592 writer.write_all(&[0])?;
598 // Create a static archive
600 // This is essentially the same thing as an rlib, but it also involves adding
601 // all of the upstream crates' objects into the archive. This will slurp in
602 // all of the native libraries of upstream dependencies as well.
604 // Additionally, there's no way for us to link dynamic libraries, so we warn
605 // about all dynamic library dependencies that they're not linked in.
607 // There's no need to include metadata in a static archive, so ensure to not
608 // link in the metadata object file (and also don't prepare the archive with a
610 fn link_staticlib(sess: &Session,
611 trans: &CrateTranslation,
612 outputs: &OutputFilenames,
616 let mut ab = link_rlib(sess,
618 RlibFlavor::StaticlibBase,
623 let mut all_native_libs = vec![];
625 let res = each_linked_rlib(sess, &trans.crate_info, &mut |cnum, path| {
626 let name = &trans.crate_info.crate_name[&cnum];
627 let native_libs = &trans.crate_info.native_libraries[&cnum];
629 // Here when we include the rlib into our staticlib we need to make a
630 // decision whether to include the extra object files along the way.
631 // These extra object files come from statically included native
632 // libraries, but they may be cfg'd away with #[link(cfg(..))].
634 // This unstable feature, though, only needs liblibc to work. The only
635 // use case there is where musl is statically included in liblibc.rlib,
636 // so if we don't want the included version we just need to skip it. As
637 // a result the logic here is that if *any* linked library is cfg'd away
638 // we just skip all object files.
640 // Clearly this is not sufficient for a general purpose feature, and
641 // we'd want to read from the library's metadata to determine which
642 // object files come from where and selectively skip them.
643 let skip_object_files = native_libs.iter().any(|lib| {
644 lib.kind == NativeLibraryKind::NativeStatic && !relevant_lib(sess, lib)
648 sess.lto() && !ignored_for_lto(&trans.crate_info, cnum),
649 skip_object_files).unwrap();
651 all_native_libs.extend(trans.crate_info.native_libraries[&cnum].iter().cloned());
653 if let Err(e) = res {
660 if !all_native_libs.is_empty() {
661 if sess.opts.prints.contains(&PrintRequest::NativeStaticLibs) {
662 print_native_static_libs(sess, &all_native_libs);
664 // Fallback for backwards compatibility only
665 print_native_static_libs_legacy(sess, &all_native_libs);
670 fn print_native_static_libs_legacy(sess: &Session, all_native_libs: &[NativeLibrary]) {
671 sess.note_without_error("link against the following native artifacts when linking against \
672 this static library");
673 sess.note_without_error("This list will not be printed by default. \
674 Please add --print=native-static-libs if you need this information");
676 for lib in all_native_libs.iter().filter(|l| relevant_lib(sess, l)) {
677 let name = match lib.kind {
678 NativeLibraryKind::NativeStaticNobundle |
679 NativeLibraryKind::NativeUnknown => "library",
680 NativeLibraryKind::NativeFramework => "framework",
681 // These are included, no need to print them
682 NativeLibraryKind::NativeStatic => continue,
684 sess.note_without_error(&format!("{}: {}", name, lib.name));
688 fn print_native_static_libs(sess: &Session, all_native_libs: &[NativeLibrary]) {
689 let lib_args: Vec<_> = all_native_libs.iter()
690 .filter(|l| relevant_lib(sess, l))
691 .filter_map(|lib| match lib.kind {
692 NativeLibraryKind::NativeStaticNobundle |
693 NativeLibraryKind::NativeUnknown => {
694 if sess.target.target.options.is_like_msvc {
695 Some(format!("{}.lib", lib.name))
697 Some(format!("-l{}", lib.name))
700 NativeLibraryKind::NativeFramework => {
701 // ld-only syntax, since there are no frameworks in MSVC
702 Some(format!("-framework {}", lib.name))
704 // These are included, no need to print them
705 NativeLibraryKind::NativeStatic => None,
708 if !lib_args.is_empty() {
709 sess.note_without_error("Link against the following native artifacts when linking \
710 against this static library. The order and any duplication \
711 can be significant on some platforms.");
712 // Prefix for greppability
713 sess.note_without_error(&format!("native-static-libs: {}", &lib_args.join(" ")));
717 // Create a dynamic library or executable
719 // This will invoke the system linker/cc to create the resulting file. This
720 // links to all upstream files as well.
721 fn link_natively(sess: &Session,
722 crate_type: config::CrateType,
725 trans: &CrateTranslation,
726 outputs: &OutputFilenames,
728 info!("preparing {:?} from {:?} to {:?}", crate_type, objects, out_filename);
729 let flavor = sess.linker_flavor();
731 // The invocations of cc share some flags across platforms
732 let (pname, mut cmd, envs) = get_linker(sess);
733 // This will set PATH on windows
736 let root = sess.target_filesearch(PathKind::Native).get_lib_path();
737 if let Some(args) = sess.target.target.options.pre_link_args.get(&flavor) {
740 if let Some(ref args) = sess.opts.debugging_opts.pre_link_args {
743 cmd.args(&sess.opts.debugging_opts.pre_link_arg);
745 let pre_link_objects = if crate_type == config::CrateTypeExecutable {
746 &sess.target.target.options.pre_link_objects_exe
748 &sess.target.target.options.pre_link_objects_dll
750 for obj in pre_link_objects {
751 cmd.arg(root.join(obj));
754 if sess.target.target.options.is_like_emscripten {
756 cmd.arg(if sess.panic_strategy() == PanicStrategy::Abort {
757 "DISABLE_EXCEPTION_CATCHING=1"
759 "DISABLE_EXCEPTION_CATCHING=0"
764 let mut linker = trans.linker_info.to_linker(cmd, &sess);
765 link_args(&mut *linker, sess, crate_type, tmpdir,
766 objects, out_filename, outputs, trans);
767 cmd = linker.finalize();
769 if let Some(args) = sess.target.target.options.late_link_args.get(&flavor) {
772 for obj in &sess.target.target.options.post_link_objects {
773 cmd.arg(root.join(obj));
775 if let Some(args) = sess.target.target.options.post_link_args.get(&flavor) {
778 for &(ref k, ref v) in &sess.target.target.options.link_env {
782 if sess.opts.debugging_opts.print_link_args {
783 println!("{:?}", &cmd);
786 // May have not found libraries in the right formats.
787 sess.abort_if_errors();
789 // Invoke the system linker
791 // Note that there's a terribly awful hack that really shouldn't be present
792 // in any compiler. Here an environment variable is supported to
793 // automatically retry the linker invocation if the linker looks like it
796 // Gee that seems odd, normally segfaults are things we want to know about!
797 // Unfortunately though in rust-lang/rust#38878 we're experiencing the
798 // linker segfaulting on Travis quite a bit which is causing quite a bit of
799 // pain to land PRs when they spuriously fail due to a segfault.
801 // The issue #38878 has some more debugging information on it as well, but
802 // this unfortunately looks like it's just a race condition in macOS's linker
803 // with some thread pool working in the background. It seems that no one
804 // currently knows a fix for this so in the meantime we're left with this...
806 let retry_on_segfault = env::var("RUSTC_RETRY_LINKER_ON_SEGFAULT").is_ok();
811 prog = time(sess.time_passes(), "running linker", || {
812 exec_linker(sess, &mut cmd, tmpdir)
814 if !retry_on_segfault || i > 3 {
817 let output = match prog {
818 Ok(ref output) => output,
821 if output.status.success() {
824 let mut out = output.stderr.clone();
825 out.extend(&output.stdout);
826 let out = String::from_utf8_lossy(&out);
827 let msg = "clang: error: unable to execute command: \
828 Segmentation fault: 11";
829 if !out.contains(msg) {
833 sess.struct_warn("looks like the linker segfaulted when we tried to \
834 call it, automatically retrying again")
835 .note(&format!("{:?}", cmd))
842 fn escape_string(s: &[u8]) -> String {
843 str::from_utf8(s).map(|s| s.to_owned())
844 .unwrap_or_else(|_| {
845 let mut x = "Non-UTF-8 output: ".to_string();
847 .flat_map(|&b| ascii::escape_default(b))
848 .map(|b| char::from_u32(b as u32).unwrap()));
852 if !prog.status.success() {
853 let mut output = prog.stderr.clone();
854 output.extend_from_slice(&prog.stdout);
855 sess.struct_err(&format!("linking with `{}` failed: {}",
858 .note(&format!("{:?}", &cmd))
859 .note(&escape_string(&output))
861 sess.abort_if_errors();
863 info!("linker stderr:\n{}", escape_string(&prog.stderr));
864 info!("linker stdout:\n{}", escape_string(&prog.stdout));
867 sess.struct_err(&format!("could not exec the linker `{}`: {}", pname, e))
868 .note(&format!("{:?}", &cmd))
870 if sess.target.target.options.is_like_msvc && e.kind() == io::ErrorKind::NotFound {
871 sess.note_without_error("the msvc targets depend on the msvc linker \
872 but `link.exe` was not found");
873 sess.note_without_error("please ensure that VS 2013 or VS 2015 was installed \
874 with the Visual C++ option");
876 sess.abort_if_errors();
881 // On macOS, debuggers need this utility to get run to do some munging of
883 if sess.target.target.options.is_like_osx && sess.opts.debuginfo != NoDebugInfo {
884 match Command::new("dsymutil").arg(out_filename).output() {
886 Err(e) => sess.fatal(&format!("failed to run dsymutil: {}", e)),
891 fn exec_linker(sess: &Session, cmd: &mut Command, tmpdir: &Path)
892 -> io::Result<Output>
894 // When attempting to spawn the linker we run a risk of blowing out the
895 // size limits for spawning a new process with respect to the arguments
896 // we pass on the command line.
898 // Here we attempt to handle errors from the OS saying "your list of
899 // arguments is too big" by reinvoking the linker again with an `@`-file
900 // that contains all the arguments. The theory is that this is then
901 // accepted on all linkers and the linker will read all its options out of
902 // there instead of looking at the command line.
903 match cmd.command().stdout(Stdio::piped()).stderr(Stdio::piped()).spawn() {
904 Ok(child) => return child.wait_with_output(),
905 Err(ref e) if command_line_too_big(e) => {}
906 Err(e) => return Err(e)
909 let file = tmpdir.join("linker-arguments");
910 let mut cmd2 = Command::new(cmd.get_program());
911 cmd2.arg(format!("@{}", file.display()));
912 for &(ref k, ref v) in cmd.get_env() {
915 let mut f = BufWriter::new(File::create(&file)?);
916 for arg in cmd.get_args() {
917 writeln!(f, "{}", Escape {
918 arg: arg.to_str().unwrap(),
919 is_like_msvc: sess.target.target.options.is_like_msvc,
923 return cmd2.output();
926 fn command_line_too_big(err: &io::Error) -> bool {
927 err.raw_os_error() == Some(::libc::E2BIG)
931 fn command_line_too_big(err: &io::Error) -> bool {
932 const ERROR_FILENAME_EXCED_RANGE: i32 = 206;
933 err.raw_os_error() == Some(ERROR_FILENAME_EXCED_RANGE)
941 impl<'a> fmt::Display for Escape<'a> {
942 fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
943 if self.is_like_msvc {
944 // This is "documented" at
945 // https://msdn.microsoft.com/en-us/library/4xdcbak7.aspx
947 // Unfortunately there's not a great specification of the
948 // syntax I could find online (at least) but some local
949 // testing showed that this seemed sufficient-ish to catch
950 // at least a few edge cases.
952 for c in self.arg.chars() {
954 '"' => write!(f, "\\{}", c)?,
955 c => write!(f, "{}", c)?,
960 // This is documented at https://linux.die.net/man/1/ld, namely:
962 // > Options in file are separated by whitespace. A whitespace
963 // > character may be included in an option by surrounding the
964 // > entire option in either single or double quotes. Any
965 // > character (including a backslash) may be included by
966 // > prefixing the character to be included with a backslash.
968 // We put an argument on each line, so all we need to do is
969 // ensure the line is interpreted as one whole argument.
970 for c in self.arg.chars() {
973 ' ' => write!(f, "\\{}", c)?,
974 c => write!(f, "{}", c)?,
983 fn link_args(cmd: &mut Linker,
985 crate_type: config::CrateType,
989 outputs: &OutputFilenames,
990 trans: &CrateTranslation) {
992 // The default library location, we need this to find the runtime.
993 // The location of crates will be determined as needed.
994 let lib_path = sess.target_filesearch(PathKind::All).get_lib_path();
997 let t = &sess.target.target;
999 cmd.include_path(&fix_windows_verbatim_for_gcc(&lib_path));
1000 for obj in objects {
1001 cmd.add_object(obj);
1003 cmd.output_filename(out_filename);
1005 if crate_type == config::CrateTypeExecutable &&
1006 sess.target.target.options.is_like_windows {
1007 if let Some(ref s) = trans.windows_subsystem {
1012 // If we're building a dynamic library then some platforms need to make sure
1013 // that all symbols are exported correctly from the dynamic library.
1014 if crate_type != config::CrateTypeExecutable ||
1015 sess.target.target.options.is_like_emscripten {
1016 cmd.export_symbols(tmpdir, crate_type);
1019 // When linking a dynamic library, we put the metadata into a section of the
1020 // executable. This metadata is in a separate object file from the main
1021 // object file, so we link that in here.
1022 if crate_type == config::CrateTypeDylib ||
1023 crate_type == config::CrateTypeProcMacro {
1024 cmd.add_object(&outputs.with_extension(METADATA_OBJ_NAME));
1027 if trans.allocator_module.is_some() {
1028 cmd.add_object(&outputs.with_extension(ALLOCATOR_OBJ_NAME));
1031 // Try to strip as much out of the generated object by removing unused
1032 // sections if possible. See more comments in linker.rs
1033 if !sess.opts.cg.link_dead_code {
1034 let keep_metadata = crate_type == config::CrateTypeDylib;
1035 cmd.gc_sections(keep_metadata);
1038 let used_link_args = &trans.crate_info.link_args;
1040 if crate_type == config::CrateTypeExecutable &&
1041 t.options.position_independent_executables {
1042 let empty_vec = Vec::new();
1043 let args = sess.opts.cg.link_args.as_ref().unwrap_or(&empty_vec);
1044 let more_args = &sess.opts.cg.link_arg;
1045 let mut args = args.iter().chain(more_args.iter()).chain(used_link_args.iter());
1047 if get_reloc_model(sess) == llvm::RelocMode::PIC
1048 && !sess.crt_static() && !args.any(|x| *x == "-static") {
1049 cmd.position_independent_executable();
1053 let relro_level = match sess.opts.debugging_opts.relro_level {
1054 Some(level) => level,
1055 None => t.options.relro_level,
1058 RelroLevel::Full => {
1061 RelroLevel::Partial => {
1062 cmd.partial_relro();
1064 RelroLevel::Off => {},
1067 // Pass optimization flags down to the linker.
1070 // Pass debuginfo flags down to the linker.
1073 // We want to prevent the compiler from accidentally leaking in any system
1074 // libraries, so we explicitly ask gcc to not link to any libraries by
1075 // default. Note that this does not happen for windows because windows pulls
1076 // in some large number of libraries and I couldn't quite figure out which
1077 // subset we wanted.
1078 if t.options.no_default_libraries {
1079 cmd.no_default_libraries();
1082 // Take careful note of the ordering of the arguments we pass to the linker
1083 // here. Linkers will assume that things on the left depend on things to the
1084 // right. Things on the right cannot depend on things on the left. This is
1085 // all formally implemented in terms of resolving symbols (libs on the right
1086 // resolve unknown symbols of libs on the left, but not vice versa).
1088 // For this reason, we have organized the arguments we pass to the linker as
1091 // 1. The local object that LLVM just generated
1092 // 2. Local native libraries
1093 // 3. Upstream rust libraries
1094 // 4. Upstream native libraries
1096 // The rationale behind this ordering is that those items lower down in the
1097 // list can't depend on items higher up in the list. For example nothing can
1098 // depend on what we just generated (e.g. that'd be a circular dependency).
1099 // Upstream rust libraries are not allowed to depend on our local native
1100 // libraries as that would violate the structure of the DAG, in that
1101 // scenario they are required to link to them as well in a shared fashion.
1103 // Note that upstream rust libraries may contain native dependencies as
1104 // well, but they also can't depend on what we just started to add to the
1105 // link line. And finally upstream native libraries can't depend on anything
1106 // in this DAG so far because they're only dylibs and dylibs can only depend
1107 // on other dylibs (e.g. other native deps).
1108 add_local_native_libraries(cmd, sess, trans);
1109 add_upstream_rust_crates(cmd, sess, trans, crate_type, tmpdir);
1110 add_upstream_native_libraries(cmd, sess, trans, crate_type);
1112 // Tell the linker what we're doing.
1113 if crate_type != config::CrateTypeExecutable {
1114 cmd.build_dylib(out_filename);
1116 if crate_type == config::CrateTypeExecutable && sess.crt_static() {
1117 cmd.build_static_executable();
1120 // FIXME (#2397): At some point we want to rpath our guesses as to
1121 // where extern libraries might live, based on the
1122 // addl_lib_search_paths
1123 if sess.opts.cg.rpath {
1124 let sysroot = sess.sysroot();
1125 let target_triple = &sess.opts.target_triple;
1126 let mut get_install_prefix_lib_path = || {
1127 let install_prefix = option_env!("CFG_PREFIX").expect("CFG_PREFIX");
1128 let tlib = filesearch::relative_target_lib_path(sysroot, target_triple);
1129 let mut path = PathBuf::from(install_prefix);
1134 let mut rpath_config = RPathConfig {
1135 used_crates: &trans.crate_info.used_crates_dynamic,
1136 out_filename: out_filename.to_path_buf(),
1137 has_rpath: sess.target.target.options.has_rpath,
1138 is_like_osx: sess.target.target.options.is_like_osx,
1139 linker_is_gnu: sess.target.target.options.linker_is_gnu,
1140 get_install_prefix_lib_path: &mut get_install_prefix_lib_path,
1142 cmd.args(&rpath::get_rpath_flags(&mut rpath_config));
1145 // Finally add all the linker arguments provided on the command line along
1146 // with any #[link_args] attributes found inside the crate
1147 if let Some(ref args) = sess.opts.cg.link_args {
1150 cmd.args(&sess.opts.cg.link_arg);
1151 cmd.args(&used_link_args);
1154 // # Native library linking
1156 // User-supplied library search paths (-L on the command line). These are
1157 // the same paths used to find Rust crates, so some of them may have been
1158 // added already by the previous crate linking code. This only allows them
1159 // to be found at compile time so it is still entirely up to outside
1160 // forces to make sure that library can be found at runtime.
1162 // Also note that the native libraries linked here are only the ones located
1163 // in the current crate. Upstream crates with native library dependencies
1164 // may have their native library pulled in above.
1165 fn add_local_native_libraries(cmd: &mut Linker,
1167 trans: &CrateTranslation) {
1168 sess.target_filesearch(PathKind::All).for_each_lib_search_path(|path, k| {
1170 PathKind::Framework => { cmd.framework_path(path); }
1171 _ => { cmd.include_path(&fix_windows_verbatim_for_gcc(path)); }
1175 let relevant_libs = trans.crate_info.used_libraries.iter().filter(|l| {
1176 relevant_lib(sess, l)
1179 let search_path = archive_search_paths(sess);
1180 for lib in relevant_libs {
1182 NativeLibraryKind::NativeUnknown => cmd.link_dylib(&lib.name.as_str()),
1183 NativeLibraryKind::NativeFramework => cmd.link_framework(&lib.name.as_str()),
1184 NativeLibraryKind::NativeStaticNobundle => cmd.link_staticlib(&lib.name.as_str()),
1185 NativeLibraryKind::NativeStatic => cmd.link_whole_staticlib(&lib.name.as_str(),
1191 // # Rust Crate linking
1193 // Rust crates are not considered at all when creating an rlib output. All
1194 // dependencies will be linked when producing the final output (instead of
1195 // the intermediate rlib version)
1196 fn add_upstream_rust_crates(cmd: &mut Linker,
1198 trans: &CrateTranslation,
1199 crate_type: config::CrateType,
1201 // All of the heavy lifting has previously been accomplished by the
1202 // dependency_format module of the compiler. This is just crawling the
1203 // output of that module, adding crates as necessary.
1205 // Linking to a rlib involves just passing it to the linker (the linker
1206 // will slurp up the object files inside), and linking to a dynamic library
1207 // involves just passing the right -l flag.
1209 let formats = sess.dependency_formats.borrow();
1210 let data = formats.get(&crate_type).unwrap();
1212 // Invoke get_used_crates to ensure that we get a topological sorting of
1214 let deps = &trans.crate_info.used_crates_dynamic;
1216 let mut compiler_builtins = None;
1218 for &(cnum, _) in deps.iter() {
1219 // We may not pass all crates through to the linker. Some crates may
1220 // appear statically in an existing dylib, meaning we'll pick up all the
1221 // symbols from the dylib.
1222 let src = &trans.crate_info.used_crate_source[&cnum];
1223 match data[cnum.as_usize() - 1] {
1224 _ if trans.crate_info.profiler_runtime == Some(cnum) => {
1225 add_static_crate(cmd, sess, trans, tmpdir, crate_type, cnum);
1227 _ if trans.crate_info.sanitizer_runtime == Some(cnum) => {
1228 link_sanitizer_runtime(cmd, sess, trans, tmpdir, cnum);
1230 // compiler-builtins are always placed last to ensure that they're
1231 // linked correctly.
1232 _ if trans.crate_info.compiler_builtins == Some(cnum) => {
1233 assert!(compiler_builtins.is_none());
1234 compiler_builtins = Some(cnum);
1236 Linkage::NotLinked |
1237 Linkage::IncludedFromDylib => {}
1238 Linkage::Static => {
1239 add_static_crate(cmd, sess, trans, tmpdir, crate_type, cnum);
1241 Linkage::Dynamic => {
1242 add_dynamic_crate(cmd, sess, &src.dylib.as_ref().unwrap().0)
1247 // compiler-builtins are always placed last to ensure that they're
1248 // linked correctly.
1249 // We must always link the `compiler_builtins` crate statically. Even if it
1250 // was already "included" in a dylib (e.g. `libstd` when `-C prefer-dynamic`
1252 if let Some(cnum) = compiler_builtins {
1253 add_static_crate(cmd, sess, trans, tmpdir, crate_type, cnum);
1256 // Converts a library file-stem into a cc -l argument
1257 fn unlib<'a>(config: &config::Config, stem: &'a str) -> &'a str {
1258 if stem.starts_with("lib") && !config.target.options.is_like_windows {
1265 // We must link the sanitizer runtime using -Wl,--whole-archive but since
1266 // it's packed in a .rlib, it contains stuff that are not objects that will
1267 // make the linker error. So we must remove those bits from the .rlib before
1269 fn link_sanitizer_runtime(cmd: &mut Linker,
1271 trans: &CrateTranslation,
1274 let src = &trans.crate_info.used_crate_source[&cnum];
1275 let cratepath = &src.rlib.as_ref().unwrap().0;
1277 if sess.target.target.options.is_like_osx {
1278 // On Apple platforms, the sanitizer is always built as a dylib, and
1279 // LLVM will link to `@rpath/*.dylib`, so we need to specify an
1280 // rpath to the library as well (the rpath should be absolute, see
1281 // PR #41352 for details).
1283 // FIXME: Remove this logic into librustc_*san once Cargo supports it
1284 let rpath = cratepath.parent().unwrap();
1285 let rpath = rpath.to_str().expect("non-utf8 component in path");
1286 cmd.args(&["-Wl,-rpath".into(), "-Xlinker".into(), rpath.into()]);
1289 let dst = tmpdir.join(cratepath.file_name().unwrap());
1290 let cfg = archive_config(sess, &dst, Some(cratepath));
1291 let mut archive = ArchiveBuilder::new(cfg);
1292 archive.update_symbols();
1294 for f in archive.src_files() {
1295 if f.ends_with("bytecode.deflate") || f == METADATA_FILENAME {
1296 archive.remove_file(&f);
1303 cmd.link_whole_rlib(&dst);
1306 // Adds the static "rlib" versions of all crates to the command line.
1307 // There's a bit of magic which happens here specifically related to LTO and
1308 // dynamic libraries. Specifically:
1310 // * For LTO, we remove upstream object files.
1311 // * For dylibs we remove metadata and bytecode from upstream rlibs
1313 // When performing LTO, almost(*) all of the bytecode from the upstream
1314 // libraries has already been included in our object file output. As a
1315 // result we need to remove the object files in the upstream libraries so
1316 // the linker doesn't try to include them twice (or whine about duplicate
1317 // symbols). We must continue to include the rest of the rlib, however, as
1318 // it may contain static native libraries which must be linked in.
1320 // (*) Crates marked with `#![no_builtins]` don't participate in LTO and
1321 // their bytecode wasn't included. The object files in those libraries must
1322 // still be passed to the linker.
1324 // When making a dynamic library, linkers by default don't include any
1325 // object files in an archive if they're not necessary to resolve the link.
1326 // We basically want to convert the archive (rlib) to a dylib, though, so we
1327 // *do* want everything included in the output, regardless of whether the
1328 // linker thinks it's needed or not. As a result we must use the
1329 // --whole-archive option (or the platform equivalent). When using this
1330 // option the linker will fail if there are non-objects in the archive (such
1331 // as our own metadata and/or bytecode). All in all, for rlibs to be
1332 // entirely included in dylibs, we need to remove all non-object files.
1334 // Note, however, that if we're not doing LTO or we're not producing a dylib
1335 // (aka we're making an executable), we can just pass the rlib blindly to
1336 // the linker (fast) because it's fine if it's not actually included as
1337 // we're at the end of the dependency chain.
1338 fn add_static_crate(cmd: &mut Linker,
1340 trans: &CrateTranslation,
1342 crate_type: config::CrateType,
1344 let src = &trans.crate_info.used_crate_source[&cnum];
1345 let cratepath = &src.rlib.as_ref().unwrap().0;
1347 // See the comment above in `link_staticlib` and `link_rlib` for why if
1348 // there's a static library that's not relevant we skip all object
1350 let native_libs = &trans.crate_info.native_libraries[&cnum];
1351 let skip_native = native_libs.iter().any(|lib| {
1352 lib.kind == NativeLibraryKind::NativeStatic && !relevant_lib(sess, lib)
1355 if (!sess.lto() || ignored_for_lto(&trans.crate_info, cnum)) &&
1356 crate_type != config::CrateTypeDylib &&
1358 cmd.link_rlib(&fix_windows_verbatim_for_gcc(cratepath));
1362 let dst = tmpdir.join(cratepath.file_name().unwrap());
1363 let name = cratepath.file_name().unwrap().to_str().unwrap();
1364 let name = &name[3..name.len() - 5]; // chop off lib/.rlib
1366 time(sess.time_passes(), &format!("altering {}.rlib", name), || {
1367 let cfg = archive_config(sess, &dst, Some(cratepath));
1368 let mut archive = ArchiveBuilder::new(cfg);
1369 archive.update_symbols();
1371 let mut any_objects = false;
1372 for f in archive.src_files() {
1373 if f.ends_with("bytecode.deflate") || f == METADATA_FILENAME {
1374 archive.remove_file(&f);
1378 let canonical = f.replace("-", "_");
1379 let canonical_name = name.replace("-", "_");
1381 let is_rust_object =
1382 canonical.starts_with(&canonical_name) && {
1383 let num = &f[name.len()..f.len() - 2];
1384 num.len() > 0 && num[1..].parse::<u32>().is_ok()
1387 // If we've been requested to skip all native object files
1388 // (those not generated by the rust compiler) then we can skip
1389 // this file. See above for why we may want to do this.
1390 let skip_because_cfg_say_so = skip_native && !is_rust_object;
1392 // If we're performing LTO and this is a rust-generated object
1393 // file, then we don't need the object file as it's part of the
1394 // LTO module. Note that `#![no_builtins]` is excluded from LTO,
1395 // though, so we let that object file slide.
1396 let skip_because_lto = sess.lto() && is_rust_object &&
1397 !trans.crate_info.is_no_builtins.contains(&cnum);
1399 if skip_because_cfg_say_so || skip_because_lto {
1400 archive.remove_file(&f);
1411 // If we're creating a dylib, then we need to include the
1412 // whole of each object in our archive into that artifact. This is
1413 // because a `dylib` can be reused as an intermediate artifact.
1415 // Note, though, that we don't want to include the whole of a
1416 // compiler-builtins crate (e.g. compiler-rt) because it'll get
1417 // repeatedly linked anyway.
1418 if crate_type == config::CrateTypeDylib &&
1419 trans.crate_info.compiler_builtins != Some(cnum) {
1420 cmd.link_whole_rlib(&fix_windows_verbatim_for_gcc(&dst));
1422 cmd.link_rlib(&fix_windows_verbatim_for_gcc(&dst));
1427 // Same thing as above, but for dynamic crates instead of static crates.
1428 fn add_dynamic_crate(cmd: &mut Linker, sess: &Session, cratepath: &Path) {
1429 // If we're performing LTO, then it should have been previously required
1430 // that all upstream rust dependencies were available in an rlib format.
1431 assert!(!sess.lto());
1433 // Just need to tell the linker about where the library lives and
1435 let parent = cratepath.parent();
1436 if let Some(dir) = parent {
1437 cmd.include_path(&fix_windows_verbatim_for_gcc(dir));
1439 let filestem = cratepath.file_stem().unwrap().to_str().unwrap();
1440 cmd.link_rust_dylib(&unlib(&sess.target, filestem),
1441 parent.unwrap_or(Path::new("")));
1445 // Link in all of our upstream crates' native dependencies. Remember that
1446 // all of these upstream native dependencies are all non-static
1447 // dependencies. We've got two cases then:
1449 // 1. The upstream crate is an rlib. In this case we *must* link in the
1450 // native dependency because the rlib is just an archive.
1452 // 2. The upstream crate is a dylib. In order to use the dylib, we have to
1453 // have the dependency present on the system somewhere. Thus, we don't
1454 // gain a whole lot from not linking in the dynamic dependency to this
1457 // The use case for this is a little subtle. In theory the native
1458 // dependencies of a crate are purely an implementation detail of the crate
1459 // itself, but the problem arises with generic and inlined functions. If a
1460 // generic function calls a native function, then the generic function must
1461 // be instantiated in the target crate, meaning that the native symbol must
1462 // also be resolved in the target crate.
1463 fn add_upstream_native_libraries(cmd: &mut Linker,
1465 trans: &CrateTranslation,
1466 crate_type: config::CrateType) {
1467 // Be sure to use a topological sorting of crates because there may be
1468 // interdependencies between native libraries. When passing -nodefaultlibs,
1469 // for example, almost all native libraries depend on libc, so we have to
1470 // make sure that's all the way at the right (liblibc is near the base of
1471 // the dependency chain).
1473 // This passes RequireStatic, but the actual requirement doesn't matter,
1474 // we're just getting an ordering of crate numbers, we're not worried about
1476 let formats = sess.dependency_formats.borrow();
1477 let data = formats.get(&crate_type).unwrap();
1479 let crates = &trans.crate_info.used_crates_static;
1480 for &(cnum, _) in crates {
1481 for lib in trans.crate_info.native_libraries[&cnum].iter() {
1482 if !relevant_lib(sess, &lib) {
1486 NativeLibraryKind::NativeUnknown => cmd.link_dylib(&lib.name.as_str()),
1487 NativeLibraryKind::NativeFramework => cmd.link_framework(&lib.name.as_str()),
1488 NativeLibraryKind::NativeStaticNobundle => {
1489 // Link "static-nobundle" native libs only if the crate they originate from
1490 // is being linked statically to the current crate. If it's linked dynamically
1491 // or is an rlib already included via some other dylib crate, the symbols from
1492 // native libs will have already been included in that dylib.
1493 if data[cnum.as_usize() - 1] == Linkage::Static {
1494 cmd.link_staticlib(&lib.name.as_str())
1497 // ignore statically included native libraries here as we've
1498 // already included them when we included the rust library
1500 NativeLibraryKind::NativeStatic => {}
1506 fn relevant_lib(sess: &Session, lib: &NativeLibrary) -> bool {
1508 Some(ref cfg) => attr::cfg_matches(cfg, &sess.parse_sess, None),