1 /// For all the linkers we support, and information they might
2 /// need out of the shared crate context before we get rid of it.
4 use rustc::session::{Session, filesearch};
5 use rustc::session::config::{
6 self, RUST_CGU_EXT, DebugInfo, OutputFilenames, OutputType, PrintRequest, Sanitizer
8 use rustc::session::search_paths::PathKind;
9 use rustc::middle::dependency_format::Linkage;
10 use rustc::middle::cstore::{LibSource, NativeLibrary, NativeLibraryKind};
11 use rustc::util::common::{time, time_ext};
12 use rustc::hir::def_id::CrateNum;
13 use rustc_data_structures::fx::FxHashSet;
14 use rustc_fs_util::fix_windows_verbatim_for_gcc;
15 use rustc_target::spec::{PanicStrategy, RelroLevel, LinkerFlavor};
17 use crate::{METADATA_FILENAME, RLIB_BYTECODE_EXTENSION, CrateInfo, CodegenResults};
18 use super::archive::ArchiveBuilder;
19 use super::command::Command;
20 use super::linker::Linker;
21 use super::rpath::{self, RPathConfig};
23 use cc::windows_registry;
24 use tempfile::{Builder as TempFileBuilder, TempDir};
31 use std::path::{Path, PathBuf};
32 use std::process::{Output, Stdio};
36 pub use rustc_codegen_utils::link::*;
38 pub fn remove(sess: &Session, path: &Path) {
39 if let Err(e) = fs::remove_file(path) {
40 sess.err(&format!("failed to remove {}: {}",
46 /// Performs the linkage portion of the compilation phase. This will generate all
47 /// of the requested outputs for this compilation session.
48 pub fn link_binary<'a, B: ArchiveBuilder<'a>>(sess: &'a Session,
49 codegen_results: &CodegenResults,
50 outputs: &OutputFilenames,
53 for &crate_type in sess.crate_types.borrow().iter() {
54 // Ignore executable crates if we have -Z no-codegen, as they will error.
55 let output_metadata = sess.opts.output_types.contains_key(&OutputType::Metadata);
56 if (sess.opts.debugging_opts.no_codegen || !sess.opts.output_types.should_codegen()) &&
58 crate_type == config::CrateType::Executable {
62 if invalid_output_for_target(sess, crate_type) {
63 bug!("invalid output type `{:?}` for target os `{}`",
64 crate_type, sess.opts.target_triple);
67 for obj in codegen_results.modules.iter().filter_map(|m| m.object.as_ref()) {
68 check_file_is_writeable(obj, sess);
71 if outputs.outputs.contains_key(&OutputType::Metadata) {
72 let out_filename = filename_for_metadata(sess, crate_name, outputs);
73 // To avoid races with another rustc process scanning the output directory,
74 // we need to write the file somewhere else and atomically move it to its
75 // final destination, with a `fs::rename` call. In order for the rename to
76 // always succeed, the temporary file needs to be on the same filesystem,
77 // which is why we create it inside the output directory specifically.
78 let metadata_tmpdir = TempFileBuilder::new()
80 .tempdir_in(out_filename.parent().unwrap())
81 .unwrap_or_else(|err| sess.fatal(&format!("couldn't create a temp dir: {}", err)));
82 let metadata = emit_metadata(sess, codegen_results, &metadata_tmpdir);
83 match fs::rename(&metadata, &out_filename) {
85 if sess.opts.debugging_opts.emit_directives {
86 sess.parse_sess.span_diagnostic.maybe_emit_json_directive(
87 format!("metadata file written: {}", out_filename.display()));
90 Err(e) => sess.fatal(&format!("failed to write {}: {}", out_filename.display(), e)),
94 let tmpdir = TempFileBuilder::new().prefix("rustc").tempdir().unwrap_or_else(|err|
95 sess.fatal(&format!("couldn't create a temp dir: {}", err)));
97 if outputs.outputs.should_codegen() {
98 let out_filename = out_filename(sess, crate_type, outputs, crate_name);
100 config::CrateType::Rlib => {
107 config::CrateType::Staticlib => {
108 link_staticlib::<B>(sess, codegen_results, &out_filename, &tmpdir);
123 if sess.opts.cg.save_temps {
124 let _ = tmpdir.into_path();
128 // Remove the temporary object file and metadata if we aren't saving temps
129 if !sess.opts.cg.save_temps {
130 if sess.opts.output_types.should_codegen() && !preserve_objects_for_their_debuginfo(sess) {
131 for obj in codegen_results.modules.iter().filter_map(|m| m.object.as_ref()) {
135 for obj in codegen_results.modules.iter().filter_map(|m| m.bytecode_compressed.as_ref()) {
138 if let Some(ref metadata_module) = codegen_results.metadata_module {
139 if let Some(ref obj) = metadata_module.object {
143 if let Some(ref allocator_module) = codegen_results.allocator_module {
144 if let Some(ref obj) = allocator_module.object {
147 if let Some(ref bc) = allocator_module.bytecode_compressed {
154 // The third parameter is for env vars, used on windows to set up the
155 // path for MSVC to find its DLLs, and gcc to find its bundled
157 pub fn get_linker(sess: &Session, linker: &Path, flavor: LinkerFlavor) -> (PathBuf, Command) {
158 let msvc_tool = windows_registry::find_tool(&sess.opts.target_triple.triple(), "link.exe");
160 // If our linker looks like a batch script on Windows then to execute this
161 // we'll need to spawn `cmd` explicitly. This is primarily done to handle
162 // emscripten where the linker is `emcc.bat` and needs to be spawned as
163 // `cmd /c emcc.bat ...`.
165 // This worked historically but is needed manually since #42436 (regression
166 // was tagged as #42791) and some more info can be found on #44443 for
167 // emscripten itself.
168 let mut cmd = match linker.to_str() {
169 Some(linker) if cfg!(windows) && linker.ends_with(".bat") => Command::bat_script(linker),
171 LinkerFlavor::Lld(f) => Command::lld(linker, f),
173 if sess.opts.cg.linker.is_none() && sess.target.target.options.linker.is_none() =>
175 Command::new(msvc_tool.as_ref().map(|t| t.path()).unwrap_or(linker))
177 _ => Command::new(linker),
181 // The compiler's sysroot often has some bundled tools, so add it to the
182 // PATH for the child.
183 let mut new_path = sess.host_filesearch(PathKind::All)
184 .get_tools_search_paths();
185 let mut msvc_changed_path = false;
186 if sess.target.target.options.is_like_msvc {
187 if let Some(ref tool) = msvc_tool {
188 cmd.args(tool.args());
189 for &(ref k, ref v) in tool.env() {
191 new_path.extend(env::split_paths(v));
192 msvc_changed_path = true;
200 if !msvc_changed_path {
201 if let Some(path) = env::var_os("PATH") {
202 new_path.extend(env::split_paths(&path));
205 cmd.env("PATH", env::join_paths(new_path).unwrap());
207 (linker.to_path_buf(), cmd)
210 pub fn each_linked_rlib(sess: &Session,
212 f: &mut dyn FnMut(CrateNum, &Path)) -> Result<(), String> {
213 let crates = info.used_crates_static.iter();
214 let fmts = sess.dependency_formats.borrow();
215 let fmts = fmts.get(&config::CrateType::Executable)
216 .or_else(|| fmts.get(&config::CrateType::Staticlib))
217 .or_else(|| fmts.get(&config::CrateType::Cdylib))
218 .or_else(|| fmts.get(&config::CrateType::ProcMacro));
219 let fmts = match fmts {
221 None => return Err("could not find formats for rlibs".to_string())
223 for &(cnum, ref path) in crates {
224 match fmts.get(cnum.as_usize() - 1) {
225 Some(&Linkage::NotLinked) |
226 Some(&Linkage::IncludedFromDylib) => continue,
228 None => return Err("could not find formats for rlibs".to_string())
230 let name = &info.crate_name[&cnum];
231 let path = match *path {
232 LibSource::Some(ref p) => p,
233 LibSource::MetadataOnly => {
234 return Err(format!("could not find rlib for: `{}`, found rmeta (metadata) file",
238 return Err(format!("could not find rlib for: `{}`", name))
246 /// We use a temp directory here to avoid races between concurrent rustc processes,
247 /// such as builds in the same directory using the same filename for metadata while
248 /// building an `.rlib` (stomping over one another), or writing an `.rmeta` into a
249 /// directory being searched for `extern crate` (observing an incomplete file).
250 /// The returned path is the temporary file containing the complete metadata.
251 fn emit_metadata<'a>(
253 codegen_results: &CodegenResults,
256 let out_filename = tmpdir.path().join(METADATA_FILENAME);
257 let result = fs::write(&out_filename, &codegen_results.metadata.raw_data);
259 if let Err(e) = result {
260 sess.fatal(&format!("failed to write {}: {}", out_filename.display(), e));
268 // An rlib in its current incarnation is essentially a renamed .a file. The
269 // rlib primarily contains the object file of the crate, but it also contains
270 // all of the object files from native libraries. This is done by unzipping
271 // native libraries and inserting all of the contents into this archive.
272 fn link_rlib<'a, B: ArchiveBuilder<'a>>(sess: &'a Session,
273 codegen_results: &CodegenResults,
276 tmpdir: &TempDir) -> B {
277 info!("preparing rlib to {:?}", out_filename);
278 let mut ab = <B as ArchiveBuilder>::new(sess, out_filename, None);
280 for obj in codegen_results.modules.iter().filter_map(|m| m.object.as_ref()) {
284 // Note that in this loop we are ignoring the value of `lib.cfg`. That is,
285 // we may not be configured to actually include a static library if we're
286 // adding it here. That's because later when we consume this rlib we'll
287 // decide whether we actually needed the static library or not.
289 // To do this "correctly" we'd need to keep track of which libraries added
290 // which object files to the archive. We don't do that here, however. The
291 // #[link(cfg(..))] feature is unstable, though, and only intended to get
292 // liblibc working. In that sense the check below just indicates that if
293 // there are any libraries we want to omit object files for at link time we
294 // just exclude all custom object files.
296 // Eventually if we want to stabilize or flesh out the #[link(cfg(..))]
297 // feature then we'll need to figure out how to record what objects were
298 // loaded from the libraries found here and then encode that into the
299 // metadata of the rlib we're generating somehow.
300 for lib in codegen_results.crate_info.used_libraries.iter() {
302 NativeLibraryKind::NativeStatic => {}
303 NativeLibraryKind::NativeStaticNobundle |
304 NativeLibraryKind::NativeFramework |
305 NativeLibraryKind::NativeUnknown => continue,
307 if let Some(name) = lib.name {
308 ab.add_native_library(&name.as_str());
312 // After adding all files to the archive, we need to update the
313 // symbol table of the archive.
316 // Note that it is important that we add all of our non-object "magical
317 // files" *after* all of the object files in the archive. The reason for
318 // this is as follows:
320 // * When performing LTO, this archive will be modified to remove
321 // objects from above. The reason for this is described below.
323 // * When the system linker looks at an archive, it will attempt to
324 // determine the architecture of the archive in order to see whether its
327 // The algorithm for this detection is: iterate over the files in the
328 // archive. Skip magical SYMDEF names. Interpret the first file as an
329 // object file. Read architecture from the object file.
331 // * As one can probably see, if "metadata" and "foo.bc" were placed
332 // before all of the objects, then the architecture of this archive would
333 // not be correctly inferred once 'foo.o' is removed.
335 // Basically, all this means is that this code should not move above the
338 RlibFlavor::Normal => {
339 // Instead of putting the metadata in an object file section, rlibs
340 // contain the metadata in a separate file.
341 ab.add_file(&emit_metadata(sess, codegen_results, tmpdir));
343 // For LTO purposes, the bytecode of this library is also inserted
345 for bytecode in codegen_results
348 .filter_map(|m| m.bytecode_compressed.as_ref())
350 ab.add_file(bytecode);
353 // After adding all files to the archive, we need to update the
354 // symbol table of the archive. This currently dies on macOS (see
355 // #11162), and isn't necessary there anyway
356 if !sess.target.target.options.is_like_osx {
361 RlibFlavor::StaticlibBase => {
362 let obj = codegen_results.allocator_module
364 .and_then(|m| m.object.as_ref());
365 if let Some(obj) = obj {
374 // Create a static archive
376 // This is essentially the same thing as an rlib, but it also involves adding
377 // all of the upstream crates' objects into the archive. This will slurp in
378 // all of the native libraries of upstream dependencies as well.
380 // Additionally, there's no way for us to link dynamic libraries, so we warn
381 // about all dynamic library dependencies that they're not linked in.
383 // There's no need to include metadata in a static archive, so ensure to not
384 // link in the metadata object file (and also don't prepare the archive with a
386 fn link_staticlib<'a, B: ArchiveBuilder<'a>>(sess: &'a Session,
387 codegen_results: &CodegenResults,
390 let mut ab = link_rlib::<B>(sess,
392 RlibFlavor::StaticlibBase,
395 let mut all_native_libs = vec![];
397 let res = each_linked_rlib(sess, &codegen_results.crate_info, &mut |cnum, path| {
398 let name = &codegen_results.crate_info.crate_name[&cnum];
399 let native_libs = &codegen_results.crate_info.native_libraries[&cnum];
401 // Here when we include the rlib into our staticlib we need to make a
402 // decision whether to include the extra object files along the way.
403 // These extra object files come from statically included native
404 // libraries, but they may be cfg'd away with #[link(cfg(..))].
406 // This unstable feature, though, only needs liblibc to work. The only
407 // use case there is where musl is statically included in liblibc.rlib,
408 // so if we don't want the included version we just need to skip it. As
409 // a result the logic here is that if *any* linked library is cfg'd away
410 // we just skip all object files.
412 // Clearly this is not sufficient for a general purpose feature, and
413 // we'd want to read from the library's metadata to determine which
414 // object files come from where and selectively skip them.
415 let skip_object_files = native_libs.iter().any(|lib| {
416 lib.kind == NativeLibraryKind::NativeStatic && !relevant_lib(sess, lib)
420 are_upstream_rust_objects_already_included(sess) &&
421 !ignored_for_lto(sess, &codegen_results.crate_info, cnum),
422 skip_object_files).unwrap();
424 all_native_libs.extend(codegen_results.crate_info.native_libraries[&cnum].iter().cloned());
426 if let Err(e) = res {
433 if !all_native_libs.is_empty() {
434 if sess.opts.prints.contains(&PrintRequest::NativeStaticLibs) {
435 print_native_static_libs(sess, &all_native_libs);
440 // Create a dynamic library or executable
442 // This will invoke the system linker/cc to create the resulting file. This
443 // links to all upstream files as well.
444 fn link_natively<'a, B: ArchiveBuilder<'a>>(sess: &'a Session,
445 crate_type: config::CrateType,
447 codegen_results: &CodegenResults,
450 info!("preparing {:?} to {:?}", crate_type, out_filename);
451 let (linker, flavor) = linker_and_flavor(sess);
453 // The invocations of cc share some flags across platforms
454 let (pname, mut cmd) = get_linker(sess, &linker, flavor);
456 if let Some(args) = sess.target.target.options.pre_link_args.get(&flavor) {
459 if let Some(args) = sess.target.target.options.pre_link_args_crt.get(&flavor) {
460 if sess.crt_static() {
464 if let Some(ref args) = sess.opts.debugging_opts.pre_link_args {
467 cmd.args(&sess.opts.debugging_opts.pre_link_arg);
469 if sess.target.target.options.is_like_fuchsia {
470 let prefix = match sess.opts.debugging_opts.sanitizer {
471 Some(Sanitizer::Address) => "asan/",
474 cmd.arg(format!("--dynamic-linker={}ld.so.1", prefix));
477 let pre_link_objects = if crate_type == config::CrateType::Executable {
478 &sess.target.target.options.pre_link_objects_exe
480 &sess.target.target.options.pre_link_objects_dll
482 for obj in pre_link_objects {
483 cmd.arg(get_file_path(sess, obj));
486 if crate_type == config::CrateType::Executable && sess.crt_static() {
487 for obj in &sess.target.target.options.pre_link_objects_exe_crt {
488 cmd.arg(get_file_path(sess, obj));
492 if sess.target.target.options.is_like_emscripten {
494 cmd.arg(if sess.panic_strategy() == PanicStrategy::Abort {
495 "DISABLE_EXCEPTION_CATCHING=1"
497 "DISABLE_EXCEPTION_CATCHING=0"
502 let mut linker = codegen_results.linker_info.to_linker(cmd, &sess, flavor, target_cpu);
503 link_args::<B>(&mut *linker, flavor, sess, crate_type, tmpdir,
504 out_filename, codegen_results);
505 cmd = linker.finalize();
507 if let Some(args) = sess.target.target.options.late_link_args.get(&flavor) {
510 for obj in &sess.target.target.options.post_link_objects {
511 cmd.arg(get_file_path(sess, obj));
513 if sess.crt_static() {
514 for obj in &sess.target.target.options.post_link_objects_crt {
515 cmd.arg(get_file_path(sess, obj));
518 if let Some(args) = sess.target.target.options.post_link_args.get(&flavor) {
521 for &(ref k, ref v) in &sess.target.target.options.link_env {
525 if sess.opts.debugging_opts.print_link_args {
526 println!("{:?}", &cmd);
529 // May have not found libraries in the right formats.
530 sess.abort_if_errors();
532 // Invoke the system linker
534 // Note that there's a terribly awful hack that really shouldn't be present
535 // in any compiler. Here an environment variable is supported to
536 // automatically retry the linker invocation if the linker looks like it
539 // Gee that seems odd, normally segfaults are things we want to know about!
540 // Unfortunately though in rust-lang/rust#38878 we're experiencing the
541 // linker segfaulting on Travis quite a bit which is causing quite a bit of
542 // pain to land PRs when they spuriously fail due to a segfault.
544 // The issue #38878 has some more debugging information on it as well, but
545 // this unfortunately looks like it's just a race condition in macOS's linker
546 // with some thread pool working in the background. It seems that no one
547 // currently knows a fix for this so in the meantime we're left with this...
549 let retry_on_segfault = env::var("RUSTC_RETRY_LINKER_ON_SEGFAULT").is_ok();
554 prog = time(sess, "running linker", || {
555 exec_linker(sess, &mut cmd, out_filename, tmpdir)
557 let output = match prog {
558 Ok(ref output) => output,
561 if output.status.success() {
564 let mut out = output.stderr.clone();
565 out.extend(&output.stdout);
566 let out = String::from_utf8_lossy(&out);
568 // Check to see if the link failed with "unrecognized command line option:
569 // '-no-pie'" for gcc or "unknown argument: '-no-pie'" for clang. If so,
570 // reperform the link step without the -no-pie option. This is safe because
571 // if the linker doesn't support -no-pie then it should not default to
572 // linking executables as pie. Different versions of gcc seem to use
573 // different quotes in the error message so don't check for them.
574 if sess.target.target.options.linker_is_gnu &&
575 flavor != LinkerFlavor::Ld &&
576 (out.contains("unrecognized command line option") ||
577 out.contains("unknown argument")) &&
578 out.contains("-no-pie") &&
579 cmd.get_args().iter().any(|e| e.to_string_lossy() == "-no-pie") {
580 info!("linker output: {:?}", out);
581 warn!("Linker does not support -no-pie command line option. Retrying without.");
582 for arg in cmd.take_args() {
583 if arg.to_string_lossy() != "-no-pie" {
590 if !retry_on_segfault || i > 3 {
593 let msg_segv = "clang: error: unable to execute command: Segmentation fault: 11";
594 let msg_bus = "clang: error: unable to execute command: Bus error: 10";
595 if !(out.contains(msg_segv) || out.contains(msg_bus)) {
600 "looks like the linker segfaulted when we tried to call it, \
601 automatically retrying again. cmd = {:?}, out = {}.",
609 fn escape_string(s: &[u8]) -> String {
610 str::from_utf8(s).map(|s| s.to_owned())
611 .unwrap_or_else(|_| {
612 let mut x = "Non-UTF-8 output: ".to_string();
614 .flat_map(|&b| ascii::escape_default(b))
619 if !prog.status.success() {
620 let mut output = prog.stderr.clone();
621 output.extend_from_slice(&prog.stdout);
622 sess.struct_err(&format!("linking with `{}` failed: {}",
625 .note(&format!("{:?}", &cmd))
626 .note(&escape_string(&output))
628 sess.abort_if_errors();
630 info!("linker stderr:\n{}", escape_string(&prog.stderr));
631 info!("linker stdout:\n{}", escape_string(&prog.stdout));
634 let linker_not_found = e.kind() == io::ErrorKind::NotFound;
636 let mut linker_error = {
637 if linker_not_found {
638 sess.struct_err(&format!("linker `{}` not found", pname.display()))
640 sess.struct_err(&format!("could not exec the linker `{}`", pname.display()))
644 linker_error.note(&e.to_string());
646 if !linker_not_found {
647 linker_error.note(&format!("{:?}", &cmd));
652 if sess.target.target.options.is_like_msvc && linker_not_found {
653 sess.note_without_error("the msvc targets depend on the msvc linker \
654 but `link.exe` was not found");
655 sess.note_without_error("please ensure that VS 2013, VS 2015 or VS 2017 \
656 was installed with the Visual C++ option");
658 sess.abort_if_errors();
663 // On macOS, debuggers need this utility to get run to do some munging of
664 // the symbols. Note, though, that if the object files are being preserved
665 // for their debug information there's no need for us to run dsymutil.
666 if sess.target.target.options.is_like_osx &&
667 sess.opts.debuginfo != DebugInfo::None &&
668 !preserve_objects_for_their_debuginfo(sess)
670 if let Err(e) = Command::new("dsymutil").arg(out_filename).output() {
671 sess.fatal(&format!("failed to run dsymutil: {}", e))
675 if sess.opts.target_triple.triple() == "wasm32-unknown-unknown" {
676 super::wasm::add_producer_section(
678 &sess.edition().to_string(),
679 option_env!("CFG_VERSION").unwrap_or("unknown"),
684 /// Returns a boolean indicating whether the specified crate should be ignored
687 /// Crates ignored during LTO are not lumped together in the "massive object
688 /// file" that we create and are linked in their normal rlib states. See
689 /// comments below for what crates do not participate in LTO.
691 /// It's unusual for a crate to not participate in LTO. Typically only
692 /// compiler-specific and unstable crates have a reason to not participate in
694 pub fn ignored_for_lto(sess: &Session, info: &CrateInfo, cnum: CrateNum) -> bool {
695 // If our target enables builtin function lowering in LLVM then the
696 // crates providing these functions don't participate in LTO (e.g.
697 // no_builtins or compiler builtins crates).
698 !sess.target.target.options.no_builtins &&
699 (info.compiler_builtins == Some(cnum) || info.is_no_builtins.contains(&cnum))
702 pub fn linker_and_flavor(sess: &Session) -> (PathBuf, LinkerFlavor) {
705 linker: Option<PathBuf>,
706 flavor: Option<LinkerFlavor>,
707 ) -> Option<(PathBuf, LinkerFlavor)> {
708 match (linker, flavor) {
709 (Some(linker), Some(flavor)) => Some((linker, flavor)),
710 // only the linker flavor is known; use the default linker for the selected flavor
711 (None, Some(flavor)) => Some((PathBuf::from(match flavor {
712 LinkerFlavor::Em => if cfg!(windows) { "emcc.bat" } else { "emcc" },
713 LinkerFlavor::Gcc => "cc",
714 LinkerFlavor::Ld => "ld",
715 LinkerFlavor::Msvc => "link.exe",
716 LinkerFlavor::Lld(_) => "lld",
717 LinkerFlavor::PtxLinker => "rust-ptx-linker",
719 (Some(linker), None) => {
722 .and_then(|stem| stem.to_str())
724 sess.fatal("couldn't extract file stem from specified linker")
727 let flavor = if stem == "emcc" {
729 } else if stem == "gcc"
730 || stem.ends_with("-gcc")
732 || stem.ends_with("-clang")
735 } else if stem == "ld" || stem == "ld.lld" || stem.ends_with("-ld") {
737 } else if stem == "link" || stem == "lld-link" {
739 } else if stem == "lld" || stem == "rust-lld" {
740 LinkerFlavor::Lld(sess.target.target.options.lld_flavor)
742 // fall back to the value in the target spec
743 sess.target.target.linker_flavor
746 Some((linker, flavor))
748 (None, None) => None,
752 // linker and linker flavor specified via command line have precedence over what the target
753 // specification specifies
754 if let Some(ret) = infer_from(sess, sess.opts.cg.linker.clone(), sess.opts.cg.linker_flavor) {
758 if let Some(ret) = infer_from(
760 sess.target.target.options.linker.clone().map(PathBuf::from),
761 Some(sess.target.target.linker_flavor),
766 bug!("Not enough information provided to determine how to invoke the linker");
769 /// Returns a boolean indicating whether we should preserve the object files on
770 /// the filesystem for their debug information. This is often useful with
771 /// split-dwarf like schemes.
772 pub fn preserve_objects_for_their_debuginfo(sess: &Session) -> bool {
773 // If the objects don't have debuginfo there's nothing to preserve.
774 if sess.opts.debuginfo == config::DebugInfo::None {
778 // If we're only producing artifacts that are archives, no need to preserve
779 // the objects as they're losslessly contained inside the archives.
780 let output_linked = sess.crate_types.borrow()
782 .any(|&x| x != config::CrateType::Rlib && x != config::CrateType::Staticlib);
787 // If we're on OSX then the equivalent of split dwarf is turned on by
788 // default. The final executable won't actually have any debug information
789 // except it'll have pointers to elsewhere. Historically we've always run
790 // `dsymutil` to "link all the dwarf together" but this is actually sort of
791 // a bummer for incremental compilation! (the whole point of split dwarf is
792 // that you don't do this sort of dwarf link).
794 // Basically as a result this just means that if we're on OSX and we're
795 // *not* running dsymutil then the object files are the only source of truth
796 // for debug information, so we must preserve them.
797 if sess.target.target.options.is_like_osx {
798 match sess.opts.debugging_opts.run_dsymutil {
799 // dsymutil is not being run, preserve objects
800 Some(false) => return true,
802 // dsymutil is being run, no need to preserve the objects
803 Some(true) => return false,
805 // The default historical behavior was to always run dsymutil, so
806 // we're preserving that temporarily, but we're likely to switch the
808 None => return false,
815 pub fn archive_search_paths(sess: &Session) -> Vec<PathBuf> {
816 sess.target_filesearch(PathKind::Native).search_path_dirs()
824 pub fn print_native_static_libs(sess: &Session, all_native_libs: &[NativeLibrary]) {
825 let lib_args: Vec<_> = all_native_libs.iter()
826 .filter(|l| relevant_lib(sess, l))
828 let name = lib.name?;
830 NativeLibraryKind::NativeStaticNobundle |
831 NativeLibraryKind::NativeUnknown => {
832 if sess.target.target.options.is_like_msvc {
833 Some(format!("{}.lib", name))
835 Some(format!("-l{}", name))
838 NativeLibraryKind::NativeFramework => {
839 // ld-only syntax, since there are no frameworks in MSVC
840 Some(format!("-framework {}", name))
842 // These are included, no need to print them
843 NativeLibraryKind::NativeStatic => None,
847 if !lib_args.is_empty() {
848 sess.note_without_error("Link against the following native artifacts when linking \
849 against this static library. The order and any duplication \
850 can be significant on some platforms.");
851 // Prefix for greppability
852 sess.note_without_error(&format!("native-static-libs: {}", &lib_args.join(" ")));
856 pub fn get_file_path(sess: &Session, name: &str) -> PathBuf {
857 let fs = sess.target_filesearch(PathKind::Native);
858 let file_path = fs.get_lib_path().join(name);
859 if file_path.exists() {
862 for search_path in fs.search_paths() {
863 let file_path = search_path.dir.join(name);
864 if file_path.exists() {
871 pub fn exec_linker(sess: &Session, cmd: &mut Command, out_filename: &Path, tmpdir: &Path)
872 -> io::Result<Output>
874 // When attempting to spawn the linker we run a risk of blowing out the
875 // size limits for spawning a new process with respect to the arguments
876 // we pass on the command line.
878 // Here we attempt to handle errors from the OS saying "your list of
879 // arguments is too big" by reinvoking the linker again with an `@`-file
880 // that contains all the arguments. The theory is that this is then
881 // accepted on all linkers and the linker will read all its options out of
882 // there instead of looking at the command line.
883 if !cmd.very_likely_to_exceed_some_spawn_limit() {
884 match cmd.command().stdout(Stdio::piped()).stderr(Stdio::piped()).spawn() {
886 let output = child.wait_with_output();
887 flush_linked_file(&output, out_filename)?;
890 Err(ref e) if command_line_too_big(e) => {
891 info!("command line to linker was too big: {}", e);
893 Err(e) => return Err(e)
897 info!("falling back to passing arguments to linker via an @-file");
898 let mut cmd2 = cmd.clone();
899 let mut args = String::new();
900 for arg in cmd2.take_args() {
901 args.push_str(&Escape {
902 arg: arg.to_str().unwrap(),
903 is_like_msvc: sess.target.target.options.is_like_msvc,
907 let file = tmpdir.join("linker-arguments");
908 let bytes = if sess.target.target.options.is_like_msvc {
909 let mut out = Vec::with_capacity((1 + args.len()) * 2);
910 // start the stream with a UTF-16 BOM
911 for c in std::iter::once(0xFEFF).chain(args.encode_utf16()) {
912 // encode in little endian
914 out.push((c >> 8) as u8);
920 fs::write(&file, &bytes)?;
921 cmd2.arg(format!("@{}", file.display()));
922 info!("invoking linker {:?}", cmd2);
923 let output = cmd2.output();
924 flush_linked_file(&output, out_filename)?;
928 fn flush_linked_file(_: &io::Result<Output>, _: &Path) -> io::Result<()> {
933 fn flush_linked_file(command_output: &io::Result<Output>, out_filename: &Path)
936 // On Windows, under high I/O load, output buffers are sometimes not flushed,
937 // even long after process exit, causing nasty, non-reproducible output bugs.
939 // File::sync_all() calls FlushFileBuffers() down the line, which solves the problem.
941 // А full writeup of the original Chrome bug can be found at
942 // randomascii.wordpress.com/2018/02/25/compiler-bug-linker-bug-windows-kernel-bug/amp
944 if let &Ok(ref out) = command_output {
945 if out.status.success() {
946 if let Ok(of) = fs::OpenOptions::new().write(true).open(out_filename) {
956 fn command_line_too_big(err: &io::Error) -> bool {
957 err.raw_os_error() == Some(::libc::E2BIG)
961 fn command_line_too_big(err: &io::Error) -> bool {
962 const ERROR_FILENAME_EXCED_RANGE: i32 = 206;
963 err.raw_os_error() == Some(ERROR_FILENAME_EXCED_RANGE)
971 impl<'a> fmt::Display for Escape<'a> {
972 fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
973 if self.is_like_msvc {
974 // This is "documented" at
975 // https://msdn.microsoft.com/en-us/library/4xdcbak7.aspx
977 // Unfortunately there's not a great specification of the
978 // syntax I could find online (at least) but some local
979 // testing showed that this seemed sufficient-ish to catch
980 // at least a few edge cases.
982 for c in self.arg.chars() {
984 '"' => write!(f, "\\{}", c)?,
985 c => write!(f, "{}", c)?,
990 // This is documented at https://linux.die.net/man/1/ld, namely:
992 // > Options in file are separated by whitespace. A whitespace
993 // > character may be included in an option by surrounding the
994 // > entire option in either single or double quotes. Any
995 // > character (including a backslash) may be included by
996 // > prefixing the character to be included with a backslash.
998 // We put an argument on each line, so all we need to do is
999 // ensure the line is interpreted as one whole argument.
1000 for c in self.arg.chars() {
1002 '\\' | ' ' => write!(f, "\\{}", c)?,
1003 c => write!(f, "{}", c)?,
1012 fn link_args<'a, B: ArchiveBuilder<'a>>(cmd: &mut dyn Linker,
1013 flavor: LinkerFlavor,
1015 crate_type: config::CrateType,
1017 out_filename: &Path,
1018 codegen_results: &CodegenResults) {
1020 // Linker plugins should be specified early in the list of arguments
1021 cmd.linker_plugin_lto();
1023 // The default library location, we need this to find the runtime.
1024 // The location of crates will be determined as needed.
1025 let lib_path = sess.target_filesearch(PathKind::All).get_lib_path();
1027 // target descriptor
1028 let t = &sess.target.target;
1030 cmd.include_path(&fix_windows_verbatim_for_gcc(&lib_path));
1031 for obj in codegen_results.modules.iter().filter_map(|m| m.object.as_ref()) {
1032 cmd.add_object(obj);
1034 cmd.output_filename(out_filename);
1036 if crate_type == config::CrateType::Executable &&
1037 sess.target.target.options.is_like_windows {
1038 if let Some(ref s) = codegen_results.windows_subsystem {
1043 // If we're building a dynamic library then some platforms need to make sure
1044 // that all symbols are exported correctly from the dynamic library.
1045 if crate_type != config::CrateType::Executable ||
1046 sess.target.target.options.is_like_emscripten {
1047 cmd.export_symbols(tmpdir, crate_type);
1050 // When linking a dynamic library, we put the metadata into a section of the
1051 // executable. This metadata is in a separate object file from the main
1052 // object file, so we link that in here.
1053 if crate_type == config::CrateType::Dylib ||
1054 crate_type == config::CrateType::ProcMacro {
1055 let obj = codegen_results.metadata_module
1057 .and_then(|m| m.object.as_ref());
1058 if let Some(obj) = obj {
1059 cmd.add_object(obj);
1063 let obj = codegen_results.allocator_module
1065 .and_then(|m| m.object.as_ref());
1066 if let Some(obj) = obj {
1067 cmd.add_object(obj);
1070 // Try to strip as much out of the generated object by removing unused
1071 // sections if possible. See more comments in linker.rs
1072 if !sess.opts.cg.link_dead_code {
1073 let keep_metadata = crate_type == config::CrateType::Dylib;
1074 cmd.gc_sections(keep_metadata);
1077 let used_link_args = &codegen_results.crate_info.link_args;
1079 if crate_type == config::CrateType::Executable {
1080 let mut position_independent_executable = false;
1082 if t.options.position_independent_executables {
1083 let empty_vec = Vec::new();
1084 let args = sess.opts.cg.link_args.as_ref().unwrap_or(&empty_vec);
1085 let more_args = &sess.opts.cg.link_arg;
1086 let mut args = args.iter().chain(more_args.iter()).chain(used_link_args.iter());
1088 if is_pic(sess) && !sess.crt_static() && !args.any(|x| *x == "-static") {
1089 position_independent_executable = true;
1093 if position_independent_executable {
1094 cmd.position_independent_executable();
1096 // recent versions of gcc can be configured to generate position
1097 // independent executables by default. We have to pass -no-pie to
1098 // explicitly turn that off. Not applicable to ld.
1099 if sess.target.target.options.linker_is_gnu
1100 && flavor != LinkerFlavor::Ld {
1101 cmd.no_position_independent_executable();
1106 let relro_level = match sess.opts.debugging_opts.relro_level {
1107 Some(level) => level,
1108 None => t.options.relro_level,
1111 RelroLevel::Full => {
1114 RelroLevel::Partial => {
1115 cmd.partial_relro();
1117 RelroLevel::Off => {
1120 RelroLevel::None => {
1124 // Pass optimization flags down to the linker.
1127 // Pass debuginfo flags down to the linker.
1130 // We want to, by default, prevent the compiler from accidentally leaking in
1131 // any system libraries, so we may explicitly ask linkers to not link to any
1132 // libraries by default. Note that this does not happen for windows because
1133 // windows pulls in some large number of libraries and I couldn't quite
1134 // figure out which subset we wanted.
1136 // This is all naturally configurable via the standard methods as well.
1137 if !sess.opts.cg.default_linker_libraries.unwrap_or(false) &&
1138 t.options.no_default_libraries
1140 cmd.no_default_libraries();
1143 // Take careful note of the ordering of the arguments we pass to the linker
1144 // here. Linkers will assume that things on the left depend on things to the
1145 // right. Things on the right cannot depend on things on the left. This is
1146 // all formally implemented in terms of resolving symbols (libs on the right
1147 // resolve unknown symbols of libs on the left, but not vice versa).
1149 // For this reason, we have organized the arguments we pass to the linker as
1152 // 1. The local object that LLVM just generated
1153 // 2. Local native libraries
1154 // 3. Upstream rust libraries
1155 // 4. Upstream native libraries
1157 // The rationale behind this ordering is that those items lower down in the
1158 // list can't depend on items higher up in the list. For example nothing can
1159 // depend on what we just generated (e.g., that'd be a circular dependency).
1160 // Upstream rust libraries are not allowed to depend on our local native
1161 // libraries as that would violate the structure of the DAG, in that
1162 // scenario they are required to link to them as well in a shared fashion.
1164 // Note that upstream rust libraries may contain native dependencies as
1165 // well, but they also can't depend on what we just started to add to the
1166 // link line. And finally upstream native libraries can't depend on anything
1167 // in this DAG so far because they're only dylibs and dylibs can only depend
1168 // on other dylibs (e.g., other native deps).
1169 add_local_native_libraries(cmd, sess, codegen_results);
1170 add_upstream_rust_crates::<B>(cmd, sess, codegen_results, crate_type, tmpdir);
1171 add_upstream_native_libraries(cmd, sess, codegen_results, crate_type);
1173 // Tell the linker what we're doing.
1174 if crate_type != config::CrateType::Executable {
1175 cmd.build_dylib(out_filename);
1177 if crate_type == config::CrateType::Executable && sess.crt_static() {
1178 cmd.build_static_executable();
1181 if sess.opts.debugging_opts.pgo_gen.enabled() {
1185 // FIXME (#2397): At some point we want to rpath our guesses as to
1186 // where extern libraries might live, based on the
1187 // addl_lib_search_paths
1188 if sess.opts.cg.rpath {
1189 let target_triple = sess.opts.target_triple.triple();
1190 let mut get_install_prefix_lib_path = || {
1191 let install_prefix = option_env!("CFG_PREFIX").expect("CFG_PREFIX");
1192 let tlib = filesearch::relative_target_lib_path(&sess.sysroot, target_triple);
1193 let mut path = PathBuf::from(install_prefix);
1198 let mut rpath_config = RPathConfig {
1199 used_crates: &codegen_results.crate_info.used_crates_dynamic,
1200 out_filename: out_filename.to_path_buf(),
1201 has_rpath: sess.target.target.options.has_rpath,
1202 is_like_osx: sess.target.target.options.is_like_osx,
1203 linker_is_gnu: sess.target.target.options.linker_is_gnu,
1204 get_install_prefix_lib_path: &mut get_install_prefix_lib_path,
1206 cmd.args(&rpath::get_rpath_flags(&mut rpath_config));
1209 // Finally add all the linker arguments provided on the command line along
1210 // with any #[link_args] attributes found inside the crate
1211 if let Some(ref args) = sess.opts.cg.link_args {
1214 cmd.args(&sess.opts.cg.link_arg);
1215 cmd.args(&used_link_args);
1218 // # Native library linking
1220 // User-supplied library search paths (-L on the command line). These are
1221 // the same paths used to find Rust crates, so some of them may have been
1222 // added already by the previous crate linking code. This only allows them
1223 // to be found at compile time so it is still entirely up to outside
1224 // forces to make sure that library can be found at runtime.
1226 // Also note that the native libraries linked here are only the ones located
1227 // in the current crate. Upstream crates with native library dependencies
1228 // may have their native library pulled in above.
1229 pub fn add_local_native_libraries(cmd: &mut dyn Linker,
1231 codegen_results: &CodegenResults) {
1232 let filesearch = sess.target_filesearch(PathKind::All);
1233 for search_path in filesearch.search_paths() {
1234 match search_path.kind {
1235 PathKind::Framework => { cmd.framework_path(&search_path.dir); }
1236 _ => { cmd.include_path(&fix_windows_verbatim_for_gcc(&search_path.dir)); }
1240 let relevant_libs = codegen_results.crate_info.used_libraries.iter().filter(|l| {
1241 relevant_lib(sess, l)
1244 let search_path = archive_search_paths(sess);
1245 for lib in relevant_libs {
1246 let name = match lib.name {
1251 NativeLibraryKind::NativeUnknown => cmd.link_dylib(&name.as_str()),
1252 NativeLibraryKind::NativeFramework => cmd.link_framework(&name.as_str()),
1253 NativeLibraryKind::NativeStaticNobundle => cmd.link_staticlib(&name.as_str()),
1254 NativeLibraryKind::NativeStatic => cmd.link_whole_staticlib(&name.as_str(),
1260 // # Rust Crate linking
1262 // Rust crates are not considered at all when creating an rlib output. All
1263 // dependencies will be linked when producing the final output (instead of
1264 // the intermediate rlib version)
1265 fn add_upstream_rust_crates<'a, B: ArchiveBuilder<'a>>(cmd: &mut dyn Linker,
1267 codegen_results: &CodegenResults,
1268 crate_type: config::CrateType,
1270 // All of the heavy lifting has previously been accomplished by the
1271 // dependency_format module of the compiler. This is just crawling the
1272 // output of that module, adding crates as necessary.
1274 // Linking to a rlib involves just passing it to the linker (the linker
1275 // will slurp up the object files inside), and linking to a dynamic library
1276 // involves just passing the right -l flag.
1278 let formats = sess.dependency_formats.borrow();
1279 let data = formats.get(&crate_type).unwrap();
1281 // Invoke get_used_crates to ensure that we get a topological sorting of
1283 let deps = &codegen_results.crate_info.used_crates_dynamic;
1285 // There's a few internal crates in the standard library (aka libcore and
1286 // libstd) which actually have a circular dependence upon one another. This
1287 // currently arises through "weak lang items" where libcore requires things
1288 // like `rust_begin_unwind` but libstd ends up defining it. To get this
1289 // circular dependence to work correctly in all situations we'll need to be
1290 // sure to correctly apply the `--start-group` and `--end-group` options to
1291 // GNU linkers, otherwise if we don't use any other symbol from the standard
1292 // library it'll get discarded and the whole application won't link.
1294 // In this loop we're calculating the `group_end`, after which crate to
1295 // pass `--end-group` and `group_start`, before which crate to pass
1296 // `--start-group`. We currently do this by passing `--end-group` after
1297 // the first crate (when iterating backwards) that requires a lang item
1298 // defined somewhere else. Once that's set then when we've defined all the
1299 // necessary lang items we'll pass `--start-group`.
1301 // Note that this isn't amazing logic for now but it should do the trick
1302 // for the current implementation of the standard library.
1303 let mut group_end = None;
1304 let mut group_start = None;
1305 let mut end_with = FxHashSet::default();
1306 let info = &codegen_results.crate_info;
1307 for &(cnum, _) in deps.iter().rev() {
1308 if let Some(missing) = info.missing_lang_items.get(&cnum) {
1309 end_with.extend(missing.iter().cloned());
1310 if end_with.len() > 0 && group_end.is_none() {
1311 group_end = Some(cnum);
1314 end_with.retain(|item| info.lang_item_to_crate.get(item) != Some(&cnum));
1315 if end_with.len() == 0 && group_end.is_some() {
1316 group_start = Some(cnum);
1321 // If we didn't end up filling in all lang items from upstream crates then
1322 // we'll be filling it in with our crate. This probably means we're the
1323 // standard library itself, so skip this for now.
1324 if group_end.is_some() && group_start.is_none() {
1328 let mut compiler_builtins = None;
1330 for &(cnum, _) in deps.iter() {
1331 if group_start == Some(cnum) {
1335 // We may not pass all crates through to the linker. Some crates may
1336 // appear statically in an existing dylib, meaning we'll pick up all the
1337 // symbols from the dylib.
1338 let src = &codegen_results.crate_info.used_crate_source[&cnum];
1339 match data[cnum.as_usize() - 1] {
1340 _ if codegen_results.crate_info.profiler_runtime == Some(cnum) => {
1341 add_static_crate::<B>(cmd, sess, codegen_results, tmpdir, crate_type, cnum);
1343 _ if codegen_results.crate_info.sanitizer_runtime == Some(cnum) => {
1344 link_sanitizer_runtime::<B>(cmd, sess, codegen_results, tmpdir, cnum);
1346 // compiler-builtins are always placed last to ensure that they're
1347 // linked correctly.
1348 _ if codegen_results.crate_info.compiler_builtins == Some(cnum) => {
1349 assert!(compiler_builtins.is_none());
1350 compiler_builtins = Some(cnum);
1352 Linkage::NotLinked |
1353 Linkage::IncludedFromDylib => {}
1354 Linkage::Static => {
1355 add_static_crate::<B>(cmd, sess, codegen_results, tmpdir, crate_type, cnum);
1357 Linkage::Dynamic => {
1358 add_dynamic_crate(cmd, sess, &src.dylib.as_ref().unwrap().0)
1362 if group_end == Some(cnum) {
1367 // compiler-builtins are always placed last to ensure that they're
1368 // linked correctly.
1369 // We must always link the `compiler_builtins` crate statically. Even if it
1370 // was already "included" in a dylib (e.g., `libstd` when `-C prefer-dynamic`
1372 if let Some(cnum) = compiler_builtins {
1373 add_static_crate::<B>(cmd, sess, codegen_results, tmpdir, crate_type, cnum);
1376 // Converts a library file-stem into a cc -l argument
1377 fn unlib<'a>(config: &config::Config, stem: &'a str) -> &'a str {
1378 if stem.starts_with("lib") && !config.target.options.is_like_windows {
1385 // We must link the sanitizer runtime using -Wl,--whole-archive but since
1386 // it's packed in a .rlib, it contains stuff that are not objects that will
1387 // make the linker error. So we must remove those bits from the .rlib before
1389 fn link_sanitizer_runtime<'a, B: ArchiveBuilder<'a>>(cmd: &mut dyn Linker,
1391 codegen_results: &CodegenResults,
1394 let src = &codegen_results.crate_info.used_crate_source[&cnum];
1395 let cratepath = &src.rlib.as_ref().unwrap().0;
1397 if sess.target.target.options.is_like_osx {
1398 // On Apple platforms, the sanitizer is always built as a dylib, and
1399 // LLVM will link to `@rpath/*.dylib`, so we need to specify an
1400 // rpath to the library as well (the rpath should be absolute, see
1401 // PR #41352 for details).
1403 // FIXME: Remove this logic into librustc_*san once Cargo supports it
1404 let rpath = cratepath.parent().unwrap();
1405 let rpath = rpath.to_str().expect("non-utf8 component in path");
1406 cmd.args(&["-Wl,-rpath".into(), "-Xlinker".into(), rpath.into()]);
1409 let dst = tmpdir.join(cratepath.file_name().unwrap());
1410 let mut archive = <B as ArchiveBuilder>::new(sess, &dst, Some(cratepath));
1411 archive.update_symbols();
1413 for f in archive.src_files() {
1414 if f.ends_with(RLIB_BYTECODE_EXTENSION) || f == METADATA_FILENAME {
1415 archive.remove_file(&f);
1421 cmd.link_whole_rlib(&dst);
1424 // Adds the static "rlib" versions of all crates to the command line.
1425 // There's a bit of magic which happens here specifically related to LTO and
1426 // dynamic libraries. Specifically:
1428 // * For LTO, we remove upstream object files.
1429 // * For dylibs we remove metadata and bytecode from upstream rlibs
1431 // When performing LTO, almost(*) all of the bytecode from the upstream
1432 // libraries has already been included in our object file output. As a
1433 // result we need to remove the object files in the upstream libraries so
1434 // the linker doesn't try to include them twice (or whine about duplicate
1435 // symbols). We must continue to include the rest of the rlib, however, as
1436 // it may contain static native libraries which must be linked in.
1438 // (*) Crates marked with `#![no_builtins]` don't participate in LTO and
1439 // their bytecode wasn't included. The object files in those libraries must
1440 // still be passed to the linker.
1442 // When making a dynamic library, linkers by default don't include any
1443 // object files in an archive if they're not necessary to resolve the link.
1444 // We basically want to convert the archive (rlib) to a dylib, though, so we
1445 // *do* want everything included in the output, regardless of whether the
1446 // linker thinks it's needed or not. As a result we must use the
1447 // --whole-archive option (or the platform equivalent). When using this
1448 // option the linker will fail if there are non-objects in the archive (such
1449 // as our own metadata and/or bytecode). All in all, for rlibs to be
1450 // entirely included in dylibs, we need to remove all non-object files.
1452 // Note, however, that if we're not doing LTO or we're not producing a dylib
1453 // (aka we're making an executable), we can just pass the rlib blindly to
1454 // the linker (fast) because it's fine if it's not actually included as
1455 // we're at the end of the dependency chain.
1456 fn add_static_crate<'a, B: ArchiveBuilder<'a>>(cmd: &mut dyn Linker,
1458 codegen_results: &CodegenResults,
1460 crate_type: config::CrateType,
1462 let src = &codegen_results.crate_info.used_crate_source[&cnum];
1463 let cratepath = &src.rlib.as_ref().unwrap().0;
1465 // See the comment above in `link_staticlib` and `link_rlib` for why if
1466 // there's a static library that's not relevant we skip all object
1468 let native_libs = &codegen_results.crate_info.native_libraries[&cnum];
1469 let skip_native = native_libs.iter().any(|lib| {
1470 lib.kind == NativeLibraryKind::NativeStatic && !relevant_lib(sess, lib)
1473 if (!are_upstream_rust_objects_already_included(sess) ||
1474 ignored_for_lto(sess, &codegen_results.crate_info, cnum)) &&
1475 crate_type != config::CrateType::Dylib &&
1477 cmd.link_rlib(&fix_windows_verbatim_for_gcc(cratepath));
1481 let dst = tmpdir.join(cratepath.file_name().unwrap());
1482 let name = cratepath.file_name().unwrap().to_str().unwrap();
1483 let name = &name[3..name.len() - 5]; // chop off lib/.rlib
1485 time_ext(sess.time_extended(), Some(sess), &format!("altering {}.rlib", name), || {
1486 let mut archive = <B as ArchiveBuilder>::new(sess, &dst, Some(cratepath));
1487 archive.update_symbols();
1489 let mut any_objects = false;
1490 for f in archive.src_files() {
1491 if f.ends_with(RLIB_BYTECODE_EXTENSION) || f == METADATA_FILENAME {
1492 archive.remove_file(&f);
1496 let canonical = f.replace("-", "_");
1497 let canonical_name = name.replace("-", "_");
1499 // Look for `.rcgu.o` at the end of the filename to conclude
1500 // that this is a Rust-related object file.
1501 fn looks_like_rust(s: &str) -> bool {
1502 let path = Path::new(s);
1503 let ext = path.extension().and_then(|s| s.to_str());
1504 if ext != Some(OutputType::Object.extension()) {
1507 let ext2 = path.file_stem()
1508 .and_then(|s| Path::new(s).extension())
1509 .and_then(|s| s.to_str());
1510 ext2 == Some(RUST_CGU_EXT)
1513 let is_rust_object =
1514 canonical.starts_with(&canonical_name) &&
1515 looks_like_rust(&f);
1517 // If we've been requested to skip all native object files
1518 // (those not generated by the rust compiler) then we can skip
1519 // this file. See above for why we may want to do this.
1520 let skip_because_cfg_say_so = skip_native && !is_rust_object;
1522 // If we're performing LTO and this is a rust-generated object
1523 // file, then we don't need the object file as it's part of the
1524 // LTO module. Note that `#![no_builtins]` is excluded from LTO,
1525 // though, so we let that object file slide.
1526 let skip_because_lto = are_upstream_rust_objects_already_included(sess) &&
1528 (sess.target.target.options.no_builtins ||
1529 !codegen_results.crate_info.is_no_builtins.contains(&cnum));
1531 if skip_because_cfg_say_so || skip_because_lto {
1532 archive.remove_file(&f);
1543 // If we're creating a dylib, then we need to include the
1544 // whole of each object in our archive into that artifact. This is
1545 // because a `dylib` can be reused as an intermediate artifact.
1547 // Note, though, that we don't want to include the whole of a
1548 // compiler-builtins crate (e.g., compiler-rt) because it'll get
1549 // repeatedly linked anyway.
1550 if crate_type == config::CrateType::Dylib &&
1551 codegen_results.crate_info.compiler_builtins != Some(cnum) {
1552 cmd.link_whole_rlib(&fix_windows_verbatim_for_gcc(&dst));
1554 cmd.link_rlib(&fix_windows_verbatim_for_gcc(&dst));
1559 // Same thing as above, but for dynamic crates instead of static crates.
1560 fn add_dynamic_crate(cmd: &mut dyn Linker, sess: &Session, cratepath: &Path) {
1561 // Just need to tell the linker about where the library lives and
1563 let parent = cratepath.parent();
1564 if let Some(dir) = parent {
1565 cmd.include_path(&fix_windows_verbatim_for_gcc(dir));
1567 let filestem = cratepath.file_stem().unwrap().to_str().unwrap();
1568 cmd.link_rust_dylib(&unlib(&sess.target, filestem),
1569 parent.unwrap_or(Path::new("")));
1573 // Link in all of our upstream crates' native dependencies. Remember that
1574 // all of these upstream native dependencies are all non-static
1575 // dependencies. We've got two cases then:
1577 // 1. The upstream crate is an rlib. In this case we *must* link in the
1578 // native dependency because the rlib is just an archive.
1580 // 2. The upstream crate is a dylib. In order to use the dylib, we have to
1581 // have the dependency present on the system somewhere. Thus, we don't
1582 // gain a whole lot from not linking in the dynamic dependency to this
1585 // The use case for this is a little subtle. In theory the native
1586 // dependencies of a crate are purely an implementation detail of the crate
1587 // itself, but the problem arises with generic and inlined functions. If a
1588 // generic function calls a native function, then the generic function must
1589 // be instantiated in the target crate, meaning that the native symbol must
1590 // also be resolved in the target crate.
1591 pub fn add_upstream_native_libraries(cmd: &mut dyn Linker,
1593 codegen_results: &CodegenResults,
1594 crate_type: config::CrateType) {
1595 // Be sure to use a topological sorting of crates because there may be
1596 // interdependencies between native libraries. When passing -nodefaultlibs,
1597 // for example, almost all native libraries depend on libc, so we have to
1598 // make sure that's all the way at the right (liblibc is near the base of
1599 // the dependency chain).
1601 // This passes RequireStatic, but the actual requirement doesn't matter,
1602 // we're just getting an ordering of crate numbers, we're not worried about
1604 let formats = sess.dependency_formats.borrow();
1605 let data = formats.get(&crate_type).unwrap();
1607 let crates = &codegen_results.crate_info.used_crates_static;
1608 for &(cnum, _) in crates {
1609 for lib in codegen_results.crate_info.native_libraries[&cnum].iter() {
1610 let name = match lib.name {
1614 if !relevant_lib(sess, &lib) {
1618 NativeLibraryKind::NativeUnknown => cmd.link_dylib(&name.as_str()),
1619 NativeLibraryKind::NativeFramework => cmd.link_framework(&name.as_str()),
1620 NativeLibraryKind::NativeStaticNobundle => {
1621 // Link "static-nobundle" native libs only if the crate they originate from
1622 // is being linked statically to the current crate. If it's linked dynamically
1623 // or is an rlib already included via some other dylib crate, the symbols from
1624 // native libs will have already been included in that dylib.
1625 if data[cnum.as_usize() - 1] == Linkage::Static {
1626 cmd.link_staticlib(&name.as_str())
1629 // ignore statically included native libraries here as we've
1630 // already included them when we included the rust library
1632 NativeLibraryKind::NativeStatic => {}
1638 pub fn relevant_lib(sess: &Session, lib: &NativeLibrary) -> bool {
1640 Some(ref cfg) => syntax::attr::cfg_matches(cfg, &sess.parse_sess, None),
1645 pub fn are_upstream_rust_objects_already_included(sess: &Session) -> bool {
1647 config::Lto::Fat => true,
1648 config::Lto::Thin => {
1649 // If we defer LTO to the linker, we haven't run LTO ourselves, so
1650 // any upstream object files have not been copied yet.
1651 !sess.opts.cg.linker_plugin_lto.enabled()
1654 config::Lto::ThinLocal => false,
1658 fn is_pic(sess: &Session) -> bool {
1659 let reloc_model_arg = match sess.opts.cg.relocation_model {
1660 Some(ref s) => &s[..],
1661 None => &sess.target.target.options.relocation_model[..],
1664 reloc_model_arg == "pic"