1 use rustc_data_structures::fx::{FxHashSet, FxIndexMap};
2 use rustc_data_structures::temp_dir::MaybeTempDir;
3 use rustc_errors::{ErrorReported, Handler};
4 use rustc_fs_util::fix_windows_verbatim_for_gcc;
5 use rustc_hir::def_id::CrateNum;
6 use rustc_middle::middle::dependency_format::Linkage;
7 use rustc_session::config::{self, CFGuard, CrateType, DebugInfo, LdImpl, Strip};
8 use rustc_session::config::{OutputFilenames, OutputType, PrintRequest};
9 use rustc_session::cstore::DllImport;
10 use rustc_session::output::{check_file_is_writeable, invalid_output_for_target, out_filename};
11 use rustc_session::search_paths::PathKind;
12 use rustc_session::utils::NativeLibKind;
13 /// For all the linkers we support, and information they might
14 /// need out of the shared crate context before we get rid of it.
15 use rustc_session::{filesearch, Session};
16 use rustc_span::symbol::Symbol;
17 use rustc_target::abi::Endian;
18 use rustc_target::spec::crt_objects::{CrtObjects, CrtObjectsFallback};
19 use rustc_target::spec::{LinkOutputKind, LinkerFlavor, LldFlavor, SplitDebuginfo};
20 use rustc_target::spec::{PanicStrategy, RelocModel, RelroLevel, SanitizerSet, Target};
22 use super::archive::{find_library, ArchiveBuilder};
23 use super::command::Command;
24 use super::linker::{self, Linker};
25 use super::rpath::{self, RPathConfig};
27 looks_like_rust_object_file, CodegenResults, CompiledModule, CrateInfo, NativeLib,
31 use cc::windows_registry;
33 use object::write::Object;
34 use object::{Architecture, BinaryFormat, Endianness, FileFlags, SectionFlags, SectionKind};
36 use tempfile::Builder as TempFileBuilder;
38 use std::ffi::OsString;
39 use std::lazy::OnceCell;
40 use std::path::{Path, PathBuf};
41 use std::process::{ExitStatus, Output, Stdio};
42 use std::{ascii, char, env, fmt, fs, io, mem, str};
44 pub fn ensure_removed(diag_handler: &Handler, path: &Path) {
45 if let Err(e) = fs::remove_file(path) {
46 if e.kind() != io::ErrorKind::NotFound {
47 diag_handler.err(&format!("failed to remove {}: {}", path.display(), e));
52 /// Performs the linkage portion of the compilation phase. This will generate all
53 /// of the requested outputs for this compilation session.
54 pub fn link_binary<'a, B: ArchiveBuilder<'a>>(
56 codegen_results: &CodegenResults,
57 outputs: &OutputFilenames,
58 ) -> Result<(), ErrorReported> {
59 let _timer = sess.timer("link_binary");
60 let output_metadata = sess.opts.output_types.contains_key(&OutputType::Metadata);
61 for &crate_type in sess.crate_types().iter() {
62 // Ignore executable crates if we have -Z no-codegen, as they will error.
63 if (sess.opts.debugging_opts.no_codegen || !sess.opts.output_types.should_codegen())
65 && crate_type == CrateType::Executable
70 if invalid_output_for_target(sess, crate_type) {
72 "invalid output type `{:?}` for target os `{}`",
74 sess.opts.target_triple
78 sess.time("link_binary_check_files_are_writeable", || {
79 for obj in codegen_results.modules.iter().filter_map(|m| m.object.as_ref()) {
80 check_file_is_writeable(obj, sess);
84 if outputs.outputs.should_link() {
85 let tmpdir = TempFileBuilder::new()
88 .unwrap_or_else(|err| sess.fatal(&format!("couldn't create a temp dir: {}", err)));
89 let path = MaybeTempDir::new(tmpdir, sess.opts.cg.save_temps);
90 let out_filename = out_filename(
94 &codegen_results.crate_info.local_crate_name.as_str(),
98 let _timer = sess.timer("link_rlib");
108 CrateType::Staticlib => {
109 link_staticlib::<B>(sess, codegen_results, &out_filename, &path)?;
121 if sess.opts.json_artifact_notifications {
122 sess.parse_sess.span_diagnostic.emit_artifact_notification(&out_filename, "link");
125 if sess.prof.enabled() {
126 if let Some(artifact_name) = out_filename.file_name() {
127 // Record size for self-profiling
128 let file_size = std::fs::metadata(&out_filename).map(|m| m.len()).unwrap_or(0);
130 sess.prof.artifact_size(
132 artifact_name.to_string_lossy(),
140 // Remove the temporary object file and metadata if we aren't saving temps
141 sess.time("link_binary_remove_temps", || {
142 if !sess.opts.cg.save_temps {
143 let remove_temps_from_module = |module: &CompiledModule| {
144 if let Some(ref obj) = module.object {
145 ensure_removed(sess.diagnostic(), obj);
148 if let Some(ref obj) = module.dwarf_object {
149 ensure_removed(sess.diagnostic(), obj);
153 if sess.opts.output_types.should_link() && !preserve_objects_for_their_debuginfo(sess) {
154 for module in &codegen_results.modules {
155 remove_temps_from_module(module);
159 if let Some(ref metadata_module) = codegen_results.metadata_module {
160 remove_temps_from_module(metadata_module);
163 if let Some(ref allocator_module) = codegen_results.allocator_module {
164 remove_temps_from_module(allocator_module);
172 pub fn each_linked_rlib(
174 f: &mut dyn FnMut(CrateNum, &Path),
175 ) -> Result<(), String> {
176 let crates = info.used_crates.iter();
178 for (ty, list) in info.dependency_formats.iter() {
180 CrateType::Executable
181 | CrateType::Staticlib
183 | CrateType::ProcMacro => {
190 let Some(fmts) = fmts else {
191 return Err("could not find formats for rlibs".to_string());
193 for &cnum in crates {
194 match fmts.get(cnum.as_usize() - 1) {
195 Some(&Linkage::NotLinked | &Linkage::IncludedFromDylib) => continue,
197 None => return Err("could not find formats for rlibs".to_string()),
199 let name = &info.crate_name[&cnum];
200 let used_crate_source = &info.used_crate_source[&cnum];
201 let path = if let Some((path, _)) = &used_crate_source.rlib {
203 } else if used_crate_source.rmeta.is_some() {
205 "could not find rlib for: `{}`, found rmeta (metadata) file",
209 return Err(format!("could not find rlib for: `{}`", name));
216 /// We use a temp directory here to avoid races between concurrent rustc processes,
217 /// such as builds in the same directory using the same filename for metadata while
218 /// building an `.rlib` (stomping over one another), or writing an `.rmeta` into a
219 /// directory being searched for `extern crate` (observing an incomplete file).
220 /// The returned path is the temporary file containing the complete metadata.
221 pub fn emit_metadata(sess: &Session, metadata: &[u8], tmpdir: &MaybeTempDir) -> PathBuf {
222 let out_filename = tmpdir.as_ref().join(METADATA_FILENAME);
223 let result = fs::write(&out_filename, metadata);
225 if let Err(e) = result {
226 sess.fatal(&format!("failed to write {}: {}", out_filename.display(), e));
232 /// Create an 'rlib'.
234 /// An rlib in its current incarnation is essentially a renamed .a file. The rlib primarily contains
235 /// the object file of the crate, but it also contains all of the object files from native
236 /// libraries. This is done by unzipping native libraries and inserting all of the contents into
238 fn link_rlib<'a, B: ArchiveBuilder<'a>>(
240 codegen_results: &CodegenResults,
243 tmpdir: &MaybeTempDir,
244 ) -> Result<B, ErrorReported> {
245 info!("preparing rlib to {:?}", out_filename);
247 let lib_search_paths = archive_search_paths(sess);
249 let mut ab = <B as ArchiveBuilder>::new(sess, out_filename, None);
251 for obj in codegen_results.modules.iter().filter_map(|m| m.object.as_ref()) {
255 // Note that in this loop we are ignoring the value of `lib.cfg`. That is,
256 // we may not be configured to actually include a static library if we're
257 // adding it here. That's because later when we consume this rlib we'll
258 // decide whether we actually needed the static library or not.
260 // To do this "correctly" we'd need to keep track of which libraries added
261 // which object files to the archive. We don't do that here, however. The
262 // #[link(cfg(..))] feature is unstable, though, and only intended to get
263 // liblibc working. In that sense the check below just indicates that if
264 // there are any libraries we want to omit object files for at link time we
265 // just exclude all custom object files.
267 // Eventually if we want to stabilize or flesh out the #[link(cfg(..))]
268 // feature then we'll need to figure out how to record what objects were
269 // loaded from the libraries found here and then encode that into the
270 // metadata of the rlib we're generating somehow.
271 for lib in codegen_results.crate_info.used_libraries.iter() {
273 NativeLibKind::Static { bundle: None | Some(true), whole_archive: Some(true) }
274 if flavor == RlibFlavor::Normal =>
276 // Don't allow mixing +bundle with +whole_archive since an rlib may contain
277 // multiple native libs, some of which are +whole-archive and some of which are
278 // -whole-archive and it isn't clear how we can currently handle such a
279 // situation correctly.
280 // See https://github.com/rust-lang/rust/issues/88085#issuecomment-901050897
282 "the linking modifiers `+bundle` and `+whole-archive` are not compatible \
283 with each other when generating rlibs",
286 NativeLibKind::Static { bundle: None | Some(true), .. } => {}
287 NativeLibKind::Static { bundle: Some(false), .. }
288 | NativeLibKind::Dylib { .. }
289 | NativeLibKind::Framework { .. }
290 | NativeLibKind::RawDylib
291 | NativeLibKind::Unspecified => continue,
293 if let Some(name) = lib.name {
295 find_library(name, lib.verbatim.unwrap_or(false), &lib_search_paths, sess);
296 ab.add_archive(&location, |_| false).unwrap_or_else(|e| {
298 "failed to add native library {}: {}",
299 location.to_string_lossy(),
306 for (raw_dylib_name, raw_dylib_imports) in
307 collate_raw_dylibs(sess, &codegen_results.crate_info.used_libraries)?
309 ab.inject_dll_import_lib(&raw_dylib_name, &raw_dylib_imports, tmpdir);
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 // metadata in rlib files is wrapped in a "dummy" object file for
340 // the target platform so the rlib can be processed entirely by
341 // normal linkers for the platform.
342 let metadata = create_metadata_file(sess, codegen_results.metadata.raw_data());
343 ab.add_file(&emit_metadata(sess, &metadata, tmpdir));
345 // After adding all files to the archive, we need to update the
346 // symbol table of the archive. This currently dies on macOS (see
347 // #11162), and isn't necessary there anyway
348 if !sess.target.is_like_osx {
353 RlibFlavor::StaticlibBase => {
354 let obj = codegen_results.allocator_module.as_ref().and_then(|m| m.object.as_ref());
355 if let Some(obj) = obj {
362 // For rlibs we "pack" rustc metadata into a dummy object file. When rustc
363 // creates a dylib crate type it will pass `--whole-archive` (or the
364 // platform equivalent) to include all object files from an rlib into the
365 // final dylib itself. This causes linkers to iterate and try to include all
366 // files located in an archive, so if metadata is stored in an archive then
367 // it needs to be of a form that the linker will be able to process.
369 // Note, though, that we don't actually want this metadata to show up in any
370 // final output of the compiler. Instead this is purely for rustc's own
371 // metadata tracking purposes.
373 // With the above in mind, each "flavor" of object format gets special
374 // handling here depending on the target:
376 // * MachO - macos-like targets will insert the metadata into a section that
377 // is sort of fake dwarf debug info. Inspecting the source of the macos
378 // linker this causes these sections to be skipped automatically because
379 // it's not in an allowlist of otherwise well known dwarf section names to
380 // go into the final artifact.
382 // * WebAssembly - we actually don't have any container format for this
383 // target. WebAssembly doesn't support the `dylib` crate type anyway so
384 // there's no need for us to support this at this time. Consequently the
385 // metadata bytes are simply stored as-is into an rlib.
387 // * COFF - Windows-like targets create an object with a section that has
388 // the `IMAGE_SCN_LNK_REMOVE` flag set which ensures that if the linker
389 // ever sees the section it doesn't process it and it's removed.
391 // * ELF - All other targets are similar to Windows in that there's a
392 // `SHF_EXCLUDE` flag we can set on sections in an object file to get
393 // automatically removed from the final output.
395 // Note that this metdata format is kept in sync with
396 // `rustc_codegen_ssa/src/back/metadata.rs`.
397 fn create_metadata_file(sess: &Session, metadata: &[u8]) -> Vec<u8> {
398 let endianness = match sess.target.options.endian {
399 Endian::Little => Endianness::Little,
400 Endian::Big => Endianness::Big,
402 let architecture = match &sess.target.arch[..] {
403 "arm" => Architecture::Arm,
404 "aarch64" => Architecture::Aarch64,
405 "x86" => Architecture::I386,
406 "s390x" => Architecture::S390x,
407 "mips" => Architecture::Mips,
408 "mips64" => Architecture::Mips64,
410 if sess.target.pointer_width == 32 {
411 Architecture::X86_64_X32
416 "powerpc" => Architecture::PowerPc,
417 "powerpc64" => Architecture::PowerPc64,
418 "riscv32" => Architecture::Riscv32,
419 "riscv64" => Architecture::Riscv64,
420 "sparc64" => Architecture::Sparc64,
422 // This is used to handle all "other" targets. This includes targets
423 // in two categories:
425 // * Some targets don't have support in the `object` crate just yet
426 // to write an object file. These targets are likely to get filled
429 // * Targets like WebAssembly don't support dylibs, so the purpose
430 // of putting metadata in object files, to support linking rlibs
431 // into dylibs, is moot.
433 // In both of these cases it means that linking into dylibs will
434 // not be supported by rustc. This doesn't matter for targets like
435 // WebAssembly and for targets not supported by the `object` crate
436 // yet it means that work will need to be done in the `object` crate
437 // to add a case above.
438 _ => return metadata.to_vec(),
441 if sess.target.is_like_osx {
442 let mut file = Object::new(BinaryFormat::MachO, architecture, endianness);
445 file.add_section(b"__DWARF".to_vec(), b".rmeta".to_vec(), SectionKind::Debug);
446 file.append_section_data(section, metadata, 1);
447 file.write().unwrap()
448 } else if sess.target.is_like_windows {
449 const IMAGE_SCN_LNK_REMOVE: u32 = 0;
450 let mut file = Object::new(BinaryFormat::Coff, architecture, endianness);
452 let section = file.add_section(Vec::new(), b".rmeta".to_vec(), SectionKind::Debug);
453 file.section_mut(section).flags =
454 SectionFlags::Coff { characteristics: IMAGE_SCN_LNK_REMOVE };
455 file.append_section_data(section, metadata, 1);
456 file.write().unwrap()
458 const SHF_EXCLUDE: u64 = 0x80000000;
459 let mut file = Object::new(BinaryFormat::Elf, architecture, endianness);
461 match &sess.target.arch[..] {
462 // copied from `mipsel-linux-gnu-gcc foo.c -c` and
463 // inspecting the resulting `e_flags` field.
465 let e_flags = elf::EF_MIPS_ARCH_32R2 | elf::EF_MIPS_CPIC | elf::EF_MIPS_PIC;
466 file.flags = FileFlags::Elf { e_flags };
468 // copied from `mips64el-linux-gnuabi64-gcc foo.c -c`
470 let e_flags = elf::EF_MIPS_ARCH_64R2 | elf::EF_MIPS_CPIC | elf::EF_MIPS_PIC;
471 file.flags = FileFlags::Elf { e_flags };
474 // copied from `riscv64-linux-gnu-gcc foo.c -c`, note though
475 // that the `+d` target feature represents whether the double
476 // float abi is enabled.
477 "riscv64" if sess.target.options.features.contains("+d") => {
478 let e_flags = elf::EF_RISCV_RVC | elf::EF_RISCV_FLOAT_ABI_DOUBLE;
479 file.flags = FileFlags::Elf { e_flags };
485 let section = file.add_section(Vec::new(), b".rmeta".to_vec(), SectionKind::Debug);
486 file.section_mut(section).flags = SectionFlags::Elf { sh_flags: SHF_EXCLUDE };
487 file.append_section_data(section, metadata, 1);
488 file.write().unwrap()
493 /// Extract all symbols defined in raw-dylib libraries, collated by library name.
495 /// If we have multiple extern blocks that specify symbols defined in the same raw-dylib library,
496 /// then the CodegenResults value contains one NativeLib instance for each block. However, the
497 /// linker appears to expect only a single import library for each library used, so we need to
498 /// collate the symbols together by library name before generating the import libraries.
499 fn collate_raw_dylibs(
501 used_libraries: &[NativeLib],
502 ) -> Result<Vec<(String, Vec<DllImport>)>, ErrorReported> {
503 // Use index maps to preserve original order of imports and libraries.
504 let mut dylib_table = FxIndexMap::<String, FxIndexMap<Symbol, &DllImport>>::default();
506 for lib in used_libraries {
507 if lib.kind == NativeLibKind::RawDylib {
508 let ext = if matches!(lib.verbatim, Some(true)) { "" } else { ".dll" };
509 let name = format!("{}{}", lib.name.expect("unnamed raw-dylib library"), ext);
510 let imports = dylib_table.entry(name.clone()).or_default();
511 for import in &lib.dll_imports {
512 if let Some(old_import) = imports.insert(import.name, import) {
513 // FIXME: when we add support for ordinals, figure out if we need to do anything
514 // if we have two DllImport values with the same name but different ordinals.
515 if import.calling_convention != old_import.calling_convention {
519 "multiple declarations of external function `{}` from \
520 library `{}` have different calling conventions",
529 sess.compile_status()?;
532 .map(|(name, imports)| {
533 (name, imports.into_iter().map(|(_, import)| import.clone()).collect())
538 /// Create a static archive.
540 /// This is essentially the same thing as an rlib, but it also involves adding all of the upstream
541 /// crates' objects into the archive. This will slurp in all of the native libraries of upstream
542 /// dependencies as well.
544 /// Additionally, there's no way for us to link dynamic libraries, so we warn about all dynamic
545 /// library dependencies that they're not linked in.
547 /// There's no need to include metadata in a static archive, so ensure to not link in the metadata
548 /// object file (and also don't prepare the archive with a metadata file).
549 fn link_staticlib<'a, B: ArchiveBuilder<'a>>(
551 codegen_results: &CodegenResults,
553 tempdir: &MaybeTempDir,
554 ) -> Result<(), ErrorReported> {
556 link_rlib::<B>(sess, codegen_results, RlibFlavor::StaticlibBase, out_filename, tempdir)?;
557 let mut all_native_libs = vec![];
559 let res = each_linked_rlib(&codegen_results.crate_info, &mut |cnum, path| {
560 let name = &codegen_results.crate_info.crate_name[&cnum];
561 let native_libs = &codegen_results.crate_info.native_libraries[&cnum];
563 // Here when we include the rlib into our staticlib we need to make a
564 // decision whether to include the extra object files along the way.
565 // These extra object files come from statically included native
566 // libraries, but they may be cfg'd away with #[link(cfg(..))].
568 // This unstable feature, though, only needs liblibc to work. The only
569 // use case there is where musl is statically included in liblibc.rlib,
570 // so if we don't want the included version we just need to skip it. As
571 // a result the logic here is that if *any* linked library is cfg'd away
572 // we just skip all object files.
574 // Clearly this is not sufficient for a general purpose feature, and
575 // we'd want to read from the library's metadata to determine which
576 // object files come from where and selectively skip them.
577 let skip_object_files = native_libs.iter().any(|lib| {
578 matches!(lib.kind, NativeLibKind::Static { bundle: None | Some(true), .. })
579 && !relevant_lib(sess, lib)
582 let lto = are_upstream_rust_objects_already_included(sess)
583 && !ignored_for_lto(sess, &codegen_results.crate_info, cnum);
585 // Ignoring obj file starting with the crate name
586 // as simple comparison is not enough - there
587 // might be also an extra name suffix
588 let obj_start = name.as_str().to_owned();
590 ab.add_archive(path, move |fname: &str| {
591 // Ignore metadata files, no matter the name.
592 if fname == METADATA_FILENAME {
596 // Don't include Rust objects if LTO is enabled
597 if lto && looks_like_rust_object_file(fname) {
601 // Otherwise if this is *not* a rust object and we're skipping
602 // objects then skip this file
603 if skip_object_files && (!fname.starts_with(&obj_start) || !fname.ends_with(".o")) {
607 // ok, don't skip this
612 all_native_libs.extend(codegen_results.crate_info.native_libraries[&cnum].iter().cloned());
614 if let Err(e) = res {
621 if !all_native_libs.is_empty() {
622 if sess.opts.prints.contains(&PrintRequest::NativeStaticLibs) {
623 print_native_static_libs(sess, &all_native_libs);
630 fn escape_stdout_stderr_string(s: &[u8]) -> String {
631 str::from_utf8(s).map(|s| s.to_owned()).unwrap_or_else(|_| {
632 let mut x = "Non-UTF-8 output: ".to_string();
633 x.extend(s.iter().flat_map(|&b| ascii::escape_default(b)).map(char::from));
638 const LLVM_DWP_EXECUTABLE: &'static str = "rust-llvm-dwp";
640 /// Invoke `llvm-dwp` (shipped alongside rustc) to link `dwo` files from Split DWARF into a `dwp`
642 fn link_dwarf_object<'a>(sess: &'a Session, executable_out_filename: &Path) {
643 info!("preparing dwp to {}.dwp", executable_out_filename.to_str().unwrap());
645 let dwp_out_filename = executable_out_filename.with_extension("dwp");
646 let mut cmd = Command::new(LLVM_DWP_EXECUTABLE);
648 cmd.arg(executable_out_filename);
650 cmd.arg(&dwp_out_filename);
652 let mut new_path = sess.get_tools_search_paths(false);
653 if let Some(path) = env::var_os("PATH") {
654 new_path.extend(env::split_paths(&path));
656 let new_path = env::join_paths(new_path).unwrap();
657 cmd.env("PATH", new_path);
660 match sess.time("run_dwp", || cmd.output()) {
661 Ok(prog) if !prog.status.success() => {
662 sess.struct_err(&format!(
663 "linking dwarf objects with `{}` failed: {}",
664 LLVM_DWP_EXECUTABLE, prog.status
666 .note(&format!("{:?}", &cmd))
667 .note(&escape_stdout_stderr_string(&prog.stdout))
668 .note(&escape_stdout_stderr_string(&prog.stderr))
670 info!("linker stderr:\n{}", escape_stdout_stderr_string(&prog.stderr));
671 info!("linker stdout:\n{}", escape_stdout_stderr_string(&prog.stdout));
675 let dwp_not_found = e.kind() == io::ErrorKind::NotFound;
676 let mut err = if dwp_not_found {
677 sess.struct_err(&format!("linker `{}` not found", LLVM_DWP_EXECUTABLE))
679 sess.struct_err(&format!("could not exec the linker `{}`", LLVM_DWP_EXECUTABLE))
682 err.note(&e.to_string());
685 err.note(&format!("{:?}", &cmd));
693 /// Create a dynamic library or executable.
695 /// This will invoke the system linker/cc to create the resulting file. This links to all upstream
697 fn link_natively<'a, B: ArchiveBuilder<'a>>(
699 crate_type: CrateType,
701 codegen_results: &CodegenResults,
704 info!("preparing {:?} to {:?}", crate_type, out_filename);
705 let (linker_path, flavor) = linker_and_flavor(sess);
706 let mut cmd = linker_with_args::<B>(
716 linker::disable_localization(&mut cmd);
718 for &(ref k, ref v) in &sess.target.link_env {
721 for k in &sess.target.link_env_remove {
725 if sess.opts.prints.contains(&PrintRequest::LinkArgs) {
726 println!("{:?}", &cmd);
729 // May have not found libraries in the right formats.
730 sess.abort_if_errors();
732 // Invoke the system linker
734 let retry_on_segfault = env::var("RUSTC_RETRY_LINKER_ON_SEGFAULT").is_ok();
735 let unknown_arg_regex =
736 Regex::new(r"(unknown|unrecognized) (command line )?(option|argument)").unwrap();
741 prog = sess.time("run_linker", || exec_linker(sess, &cmd, out_filename, tmpdir));
742 let output = match prog {
743 Ok(ref output) => output,
746 if output.status.success() {
749 let mut out = output.stderr.clone();
750 out.extend(&output.stdout);
751 let out = String::from_utf8_lossy(&out);
753 // Check to see if the link failed with an error message that indicates it
754 // doesn't recognize the -no-pie option. If so, reperform the link step
755 // without it. This is safe because if the linker doesn't support -no-pie
756 // then it should not default to linking executables as pie. Different
757 // versions of gcc seem to use different quotes in the error message so
758 // don't check for them.
759 if sess.target.linker_is_gnu
760 && flavor != LinkerFlavor::Ld
761 && unknown_arg_regex.is_match(&out)
762 && out.contains("-no-pie")
763 && cmd.get_args().iter().any(|e| e.to_string_lossy() == "-no-pie")
765 info!("linker output: {:?}", out);
766 warn!("Linker does not support -no-pie command line option. Retrying without.");
767 for arg in cmd.take_args() {
768 if arg.to_string_lossy() != "-no-pie" {
776 // Detect '-static-pie' used with an older version of gcc or clang not supporting it.
777 // Fallback from '-static-pie' to '-static' in that case.
778 if sess.target.linker_is_gnu
779 && flavor != LinkerFlavor::Ld
780 && unknown_arg_regex.is_match(&out)
781 && (out.contains("-static-pie") || out.contains("--no-dynamic-linker"))
782 && cmd.get_args().iter().any(|e| e.to_string_lossy() == "-static-pie")
784 info!("linker output: {:?}", out);
786 "Linker does not support -static-pie command line option. Retrying with -static instead."
788 // Mirror `add_(pre,post)_link_objects` to replace CRT objects.
789 let self_contained = crt_objects_fallback(sess, crate_type);
790 let opts = &sess.target;
791 let pre_objects = if self_contained {
792 &opts.pre_link_objects_fallback
794 &opts.pre_link_objects
796 let post_objects = if self_contained {
797 &opts.post_link_objects_fallback
799 &opts.post_link_objects
801 let get_objects = |objects: &CrtObjects, kind| {
807 .map(|obj| get_object_file_path(sess, obj, self_contained).into_os_string())
810 let pre_objects_static_pie = get_objects(pre_objects, LinkOutputKind::StaticPicExe);
811 let post_objects_static_pie = get_objects(post_objects, LinkOutputKind::StaticPicExe);
812 let mut pre_objects_static = get_objects(pre_objects, LinkOutputKind::StaticNoPicExe);
813 let mut post_objects_static = get_objects(post_objects, LinkOutputKind::StaticNoPicExe);
814 // Assume that we know insertion positions for the replacement arguments from replaced
815 // arguments, which is true for all supported targets.
816 assert!(pre_objects_static.is_empty() || !pre_objects_static_pie.is_empty());
817 assert!(post_objects_static.is_empty() || !post_objects_static_pie.is_empty());
818 for arg in cmd.take_args() {
819 if arg.to_string_lossy() == "-static-pie" {
820 // Replace the output kind.
822 } else if pre_objects_static_pie.contains(&arg) {
823 // Replace the pre-link objects (replace the first and remove the rest).
824 cmd.args(mem::take(&mut pre_objects_static));
825 } else if post_objects_static_pie.contains(&arg) {
826 // Replace the post-link objects (replace the first and remove the rest).
827 cmd.args(mem::take(&mut post_objects_static));
836 // Here's a terribly awful hack that really shouldn't be present in any
837 // compiler. Here an environment variable is supported to automatically
838 // retry the linker invocation if the linker looks like it segfaulted.
840 // Gee that seems odd, normally segfaults are things we want to know
841 // about! Unfortunately though in rust-lang/rust#38878 we're
842 // experiencing the linker segfaulting on Travis quite a bit which is
843 // causing quite a bit of pain to land PRs when they spuriously fail
844 // due to a segfault.
846 // The issue #38878 has some more debugging information on it as well,
847 // but this unfortunately looks like it's just a race condition in
848 // macOS's linker with some thread pool working in the background. It
849 // seems that no one currently knows a fix for this so in the meantime
850 // we're left with this...
851 if !retry_on_segfault || i > 3 {
854 let msg_segv = "clang: error: unable to execute command: Segmentation fault: 11";
855 let msg_bus = "clang: error: unable to execute command: Bus error: 10";
856 if out.contains(msg_segv) || out.contains(msg_bus) {
859 "looks like the linker segfaulted when we tried to call it, \
860 automatically retrying again",
865 if is_illegal_instruction(&output.status) {
867 ?cmd, %out, status = %output.status,
868 "looks like the linker hit an illegal instruction when we \
869 tried to call it, automatically retrying again.",
875 fn is_illegal_instruction(status: &ExitStatus) -> bool {
876 use std::os::unix::prelude::*;
877 status.signal() == Some(libc::SIGILL)
881 fn is_illegal_instruction(_status: &ExitStatus) -> bool {
888 if !prog.status.success() {
889 let mut output = prog.stderr.clone();
890 output.extend_from_slice(&prog.stdout);
891 let escaped_output = escape_stdout_stderr_string(&output);
892 let mut err = sess.struct_err(&format!(
893 "linking with `{}` failed: {}",
894 linker_path.display(),
897 err.note(&format!("{:?}", &cmd)).note(&escaped_output);
898 if escaped_output.contains("undefined reference to") {
900 "some `extern` functions couldn't be found; some native libraries may \
901 need to be installed or have their path specified",
903 err.note("use the `-l` flag to specify native libraries to link");
904 err.note("use the `cargo:rustc-link-lib` directive to specify the native \
905 libraries to link with Cargo (see https://doc.rust-lang.org/cargo/reference/build-scripts.html#cargorustc-link-libkindname)");
909 // If MSVC's `link.exe` was expected but the return code
910 // is not a Microsoft LNK error then suggest a way to fix or
911 // install the Visual Studio build tools.
912 if let Some(code) = prog.status.code() {
913 if sess.target.is_like_msvc
914 && flavor == LinkerFlavor::Msvc
915 // Respect the command line override
916 && sess.opts.cg.linker.is_none()
917 // Match exactly "link.exe"
918 && linker_path.to_str() == Some("link.exe")
919 // All Microsoft `link.exe` linking error codes are
920 // four digit numbers in the range 1000 to 9999 inclusive
921 && (code < 1000 || code > 9999)
923 let is_vs_installed = windows_registry::find_vs_version().is_ok();
924 let has_linker = windows_registry::find_tool(
925 &sess.opts.target_triple.triple(),
930 sess.note_without_error("`link.exe` returned an unexpected error");
931 if is_vs_installed && has_linker {
932 // the linker is broken
933 sess.note_without_error(
934 "the Visual Studio build tools may need to be repaired \
935 using the Visual Studio installer",
937 sess.note_without_error(
938 "or a necessary component may be missing from the \
939 \"C++ build tools\" workload",
941 } else if is_vs_installed {
942 // the linker is not installed
943 sess.note_without_error(
944 "in the Visual Studio installer, ensure the \
945 \"C++ build tools\" workload is selected",
948 // visual studio is not installed
949 sess.note_without_error(
950 "you may need to install Visual Studio build tools with the \
951 \"C++ build tools\" workload",
957 sess.abort_if_errors();
959 info!("linker stderr:\n{}", escape_stdout_stderr_string(&prog.stderr));
960 info!("linker stdout:\n{}", escape_stdout_stderr_string(&prog.stdout));
963 let linker_not_found = e.kind() == io::ErrorKind::NotFound;
965 let mut linker_error = {
966 if linker_not_found {
967 sess.struct_err(&format!("linker `{}` not found", linker_path.display()))
969 sess.struct_err(&format!(
970 "could not exec the linker `{}`",
971 linker_path.display()
976 linker_error.note(&e.to_string());
978 if !linker_not_found {
979 linker_error.note(&format!("{:?}", &cmd));
984 if sess.target.is_like_msvc && linker_not_found {
985 sess.note_without_error(
986 "the msvc targets depend on the msvc linker \
987 but `link.exe` was not found",
989 sess.note_without_error(
990 "please ensure that VS 2013, VS 2015, VS 2017 or VS 2019 \
991 was installed with the Visual C++ option",
994 sess.abort_if_errors();
998 match sess.split_debuginfo() {
999 // If split debug information is disabled or located in individual files
1000 // there's nothing to do here.
1001 SplitDebuginfo::Off | SplitDebuginfo::Unpacked => {}
1003 // If packed split-debuginfo is requested, but the final compilation
1004 // doesn't actually have any debug information, then we skip this step.
1005 SplitDebuginfo::Packed if sess.opts.debuginfo == DebugInfo::None => {}
1007 // On macOS the external `dsymutil` tool is used to create the packed
1008 // debug information. Note that this will read debug information from
1009 // the objects on the filesystem which we'll clean up later.
1010 SplitDebuginfo::Packed if sess.target.is_like_osx => {
1011 let prog = Command::new("dsymutil").arg(out_filename).output();
1014 if !prog.status.success() {
1015 let mut output = prog.stderr.clone();
1016 output.extend_from_slice(&prog.stdout);
1017 sess.struct_warn(&format!(
1018 "processing debug info with `dsymutil` failed: {}",
1021 .note(&escape_string(&output))
1025 Err(e) => sess.fatal(&format!("unable to run `dsymutil`: {}", e)),
1029 // On MSVC packed debug information is produced by the linker itself so
1030 // there's no need to do anything else here.
1031 SplitDebuginfo::Packed if sess.target.is_like_msvc => {}
1033 // ... and otherwise we're processing a `*.dwp` packed dwarf file.
1034 SplitDebuginfo::Packed => link_dwarf_object(sess, &out_filename),
1037 let strip = strip_value(sess);
1039 if sess.target.is_like_osx {
1041 Strip::Debuginfo => strip_symbols_in_osx(sess, &out_filename, Some("-S")),
1042 Strip::Symbols => strip_symbols_in_osx(sess, &out_filename, None),
1048 // Temporarily support both -Z strip and -C strip
1049 fn strip_value(sess: &Session) -> Strip {
1050 match (sess.opts.debugging_opts.strip, sess.opts.cg.strip) {
1051 (s, Strip::None) => s,
1056 fn strip_symbols_in_osx<'a>(sess: &'a Session, out_filename: &Path, option: Option<&str>) {
1057 let mut cmd = Command::new("strip");
1058 if let Some(option) = option {
1061 let prog = cmd.arg(out_filename).output();
1064 if !prog.status.success() {
1065 let mut output = prog.stderr.clone();
1066 output.extend_from_slice(&prog.stdout);
1067 sess.struct_warn(&format!(
1068 "stripping debug info with `strip` failed: {}",
1071 .note(&escape_string(&output))
1075 Err(e) => sess.fatal(&format!("unable to run `strip`: {}", e)),
1079 fn escape_string(s: &[u8]) -> String {
1080 str::from_utf8(s).map(|s| s.to_owned()).unwrap_or_else(|_| {
1081 let mut x = "Non-UTF-8 output: ".to_string();
1082 x.extend(s.iter().flat_map(|&b| ascii::escape_default(b)).map(char::from));
1087 fn add_sanitizer_libraries(sess: &Session, crate_type: CrateType, linker: &mut dyn Linker) {
1088 // On macOS the runtimes are distributed as dylibs which should be linked to
1089 // both executables and dynamic shared objects. Everywhere else the runtimes
1090 // are currently distributed as static liraries which should be linked to
1091 // executables only.
1092 let needs_runtime = match crate_type {
1093 CrateType::Executable => true,
1094 CrateType::Dylib | CrateType::Cdylib | CrateType::ProcMacro => sess.target.is_like_osx,
1095 CrateType::Rlib | CrateType::Staticlib => false,
1102 let sanitizer = sess.opts.debugging_opts.sanitizer;
1103 if sanitizer.contains(SanitizerSet::ADDRESS) {
1104 link_sanitizer_runtime(sess, linker, "asan");
1106 if sanitizer.contains(SanitizerSet::LEAK) {
1107 link_sanitizer_runtime(sess, linker, "lsan");
1109 if sanitizer.contains(SanitizerSet::MEMORY) {
1110 link_sanitizer_runtime(sess, linker, "msan");
1112 if sanitizer.contains(SanitizerSet::THREAD) {
1113 link_sanitizer_runtime(sess, linker, "tsan");
1115 if sanitizer.contains(SanitizerSet::HWADDRESS) {
1116 link_sanitizer_runtime(sess, linker, "hwasan");
1120 fn link_sanitizer_runtime(sess: &Session, linker: &mut dyn Linker, name: &str) {
1121 fn find_sanitizer_runtime(sess: &Session, filename: &str) -> PathBuf {
1123 filesearch::make_target_lib_path(&sess.sysroot, sess.opts.target_triple.triple());
1124 let path = session_tlib.join(filename);
1126 return session_tlib;
1128 let default_sysroot = filesearch::get_or_default_sysroot();
1129 let default_tlib = filesearch::make_target_lib_path(
1131 sess.opts.target_triple.triple(),
1133 return default_tlib;
1137 let channel = option_env!("CFG_RELEASE_CHANNEL")
1138 .map(|channel| format!("-{}", channel))
1139 .unwrap_or_default();
1141 if sess.target.is_like_osx {
1142 // On Apple platforms, the sanitizer is always built as a dylib, and
1143 // LLVM will link to `@rpath/*.dylib`, so we need to specify an
1144 // rpath to the library as well (the rpath should be absolute, see
1145 // PR #41352 for details).
1146 let filename = format!("rustc{}_rt.{}", channel, name);
1147 let path = find_sanitizer_runtime(&sess, &filename);
1148 let rpath = path.to_str().expect("non-utf8 component in path");
1149 linker.args(&["-Wl,-rpath", "-Xlinker", rpath]);
1150 linker.link_dylib(Symbol::intern(&filename), false, true);
1152 let filename = format!("librustc{}_rt.{}.a", channel, name);
1153 let path = find_sanitizer_runtime(&sess, &filename).join(&filename);
1154 linker.link_whole_rlib(&path);
1158 /// Returns a boolean indicating whether the specified crate should be ignored
1161 /// Crates ignored during LTO are not lumped together in the "massive object
1162 /// file" that we create and are linked in their normal rlib states. See
1163 /// comments below for what crates do not participate in LTO.
1165 /// It's unusual for a crate to not participate in LTO. Typically only
1166 /// compiler-specific and unstable crates have a reason to not participate in
1168 pub fn ignored_for_lto(sess: &Session, info: &CrateInfo, cnum: CrateNum) -> bool {
1169 // If our target enables builtin function lowering in LLVM then the
1170 // crates providing these functions don't participate in LTO (e.g.
1171 // no_builtins or compiler builtins crates).
1172 !sess.target.no_builtins
1173 && (info.compiler_builtins == Some(cnum) || info.is_no_builtins.contains(&cnum))
1176 // This functions tries to determine the appropriate linker (and corresponding LinkerFlavor) to use
1177 pub fn linker_and_flavor(sess: &Session) -> (PathBuf, LinkerFlavor) {
1180 linker: Option<PathBuf>,
1181 flavor: Option<LinkerFlavor>,
1182 ) -> Option<(PathBuf, LinkerFlavor)> {
1183 match (linker, flavor) {
1184 (Some(linker), Some(flavor)) => Some((linker, flavor)),
1185 // only the linker flavor is known; use the default linker for the selected flavor
1186 (None, Some(flavor)) => Some((
1187 PathBuf::from(match flavor {
1188 LinkerFlavor::Em => {
1195 LinkerFlavor::Gcc => {
1196 if cfg!(any(target_os = "solaris", target_os = "illumos")) {
1197 // On historical Solaris systems, "cc" may have
1198 // been Sun Studio, which is not flag-compatible
1199 // with "gcc". This history casts a long shadow,
1200 // and many modern illumos distributions today
1201 // ship GCC as "gcc" without also making it
1202 // available as "cc".
1208 LinkerFlavor::Ld => "ld",
1209 LinkerFlavor::Msvc => "link.exe",
1210 LinkerFlavor::Lld(_) => "lld",
1211 LinkerFlavor::PtxLinker => "rust-ptx-linker",
1212 LinkerFlavor::BpfLinker => "bpf-linker",
1216 (Some(linker), None) => {
1217 let stem = linker.file_stem().and_then(|stem| stem.to_str()).unwrap_or_else(|| {
1218 sess.fatal("couldn't extract file stem from specified linker")
1221 let flavor = if stem == "emcc" {
1223 } else if stem == "gcc"
1224 || stem.ends_with("-gcc")
1226 || stem.ends_with("-clang")
1229 } else if stem == "wasm-ld" || stem.ends_with("-wasm-ld") {
1230 LinkerFlavor::Lld(LldFlavor::Wasm)
1231 } else if stem == "ld" || stem == "ld.lld" || stem.ends_with("-ld") {
1233 } else if stem == "link" || stem == "lld-link" {
1235 } else if stem == "lld" || stem == "rust-lld" {
1236 LinkerFlavor::Lld(sess.target.lld_flavor)
1238 // fall back to the value in the target spec
1239 sess.target.linker_flavor
1242 Some((linker, flavor))
1244 (None, None) => None,
1248 // linker and linker flavor specified via command line have precedence over what the target
1249 // specification specifies
1250 if let Some(ret) = infer_from(sess, sess.opts.cg.linker.clone(), sess.opts.cg.linker_flavor) {
1254 if let Some(ret) = infer_from(
1256 sess.target.linker.clone().map(PathBuf::from),
1257 Some(sess.target.linker_flavor),
1262 bug!("Not enough information provided to determine how to invoke the linker");
1265 /// Returns a boolean indicating whether we should preserve the object files on
1266 /// the filesystem for their debug information. This is often useful with
1267 /// split-dwarf like schemes.
1268 fn preserve_objects_for_their_debuginfo(sess: &Session) -> bool {
1269 // If the objects don't have debuginfo there's nothing to preserve.
1270 if sess.opts.debuginfo == config::DebugInfo::None {
1274 // If we're only producing artifacts that are archives, no need to preserve
1275 // the objects as they're losslessly contained inside the archives.
1277 sess.crate_types().iter().any(|&x| x != CrateType::Rlib && x != CrateType::Staticlib);
1282 // "unpacked" split debuginfo means that we leave object files as the
1283 // debuginfo is found in the original object files themselves
1284 sess.split_debuginfo() == SplitDebuginfo::Unpacked
1287 fn archive_search_paths(sess: &Session) -> Vec<PathBuf> {
1288 sess.target_filesearch(PathKind::Native).search_path_dirs()
1291 #[derive(PartialEq)]
1297 fn print_native_static_libs(sess: &Session, all_native_libs: &[NativeLib]) {
1298 let lib_args: Vec<_> = all_native_libs
1300 .filter(|l| relevant_lib(sess, l))
1302 let name = lib.name?;
1304 NativeLibKind::Static { bundle: Some(false), .. }
1305 | NativeLibKind::Dylib { .. }
1306 | NativeLibKind::Unspecified => {
1307 let verbatim = lib.verbatim.unwrap_or(false);
1308 if sess.target.is_like_msvc {
1309 Some(format!("{}{}", name, if verbatim { "" } else { ".lib" }))
1310 } else if sess.target.linker_is_gnu {
1311 Some(format!("-l{}{}", if verbatim { ":" } else { "" }, name))
1313 Some(format!("-l{}", name))
1316 NativeLibKind::Framework { .. } => {
1317 // ld-only syntax, since there are no frameworks in MSVC
1318 Some(format!("-framework {}", name))
1320 // These are included, no need to print them
1321 NativeLibKind::Static { bundle: None | Some(true), .. }
1322 | NativeLibKind::RawDylib => None,
1326 if !lib_args.is_empty() {
1327 sess.note_without_error(
1328 "Link against the following native artifacts when linking \
1329 against this static library. The order and any duplication \
1330 can be significant on some platforms.",
1332 // Prefix for greppability
1333 sess.note_without_error(&format!("native-static-libs: {}", &lib_args.join(" ")));
1337 fn get_object_file_path(sess: &Session, name: &str, self_contained: bool) -> PathBuf {
1338 let fs = sess.target_filesearch(PathKind::Native);
1339 let file_path = fs.get_lib_path().join(name);
1340 if file_path.exists() {
1343 // Special directory with objects used only in self-contained linkage mode
1345 let file_path = fs.get_self_contained_lib_path().join(name);
1346 if file_path.exists() {
1350 for search_path in fs.search_paths() {
1351 let file_path = search_path.dir.join(name);
1352 if file_path.exists() {
1362 out_filename: &Path,
1364 ) -> io::Result<Output> {
1365 // When attempting to spawn the linker we run a risk of blowing out the
1366 // size limits for spawning a new process with respect to the arguments
1367 // we pass on the command line.
1369 // Here we attempt to handle errors from the OS saying "your list of
1370 // arguments is too big" by reinvoking the linker again with an `@`-file
1371 // that contains all the arguments. The theory is that this is then
1372 // accepted on all linkers and the linker will read all its options out of
1373 // there instead of looking at the command line.
1374 if !cmd.very_likely_to_exceed_some_spawn_limit() {
1375 match cmd.command().stdout(Stdio::piped()).stderr(Stdio::piped()).spawn() {
1377 let output = child.wait_with_output();
1378 flush_linked_file(&output, out_filename)?;
1381 Err(ref e) if command_line_too_big(e) => {
1382 info!("command line to linker was too big: {}", e);
1384 Err(e) => return Err(e),
1388 info!("falling back to passing arguments to linker via an @-file");
1389 let mut cmd2 = cmd.clone();
1390 let mut args = String::new();
1391 for arg in cmd2.take_args() {
1393 &Escape { arg: arg.to_str().unwrap(), is_like_msvc: sess.target.is_like_msvc }
1398 let file = tmpdir.join("linker-arguments");
1399 let bytes = if sess.target.is_like_msvc {
1400 let mut out = Vec::with_capacity((1 + args.len()) * 2);
1401 // start the stream with a UTF-16 BOM
1402 for c in std::iter::once(0xFEFF).chain(args.encode_utf16()) {
1403 // encode in little endian
1405 out.push((c >> 8) as u8);
1411 fs::write(&file, &bytes)?;
1412 cmd2.arg(format!("@{}", file.display()));
1413 info!("invoking linker {:?}", cmd2);
1414 let output = cmd2.output();
1415 flush_linked_file(&output, out_filename)?;
1418 #[cfg(not(windows))]
1419 fn flush_linked_file(_: &io::Result<Output>, _: &Path) -> io::Result<()> {
1424 fn flush_linked_file(
1425 command_output: &io::Result<Output>,
1426 out_filename: &Path,
1427 ) -> io::Result<()> {
1428 // On Windows, under high I/O load, output buffers are sometimes not flushed,
1429 // even long after process exit, causing nasty, non-reproducible output bugs.
1431 // File::sync_all() calls FlushFileBuffers() down the line, which solves the problem.
1433 // А full writeup of the original Chrome bug can be found at
1434 // randomascii.wordpress.com/2018/02/25/compiler-bug-linker-bug-windows-kernel-bug/amp
1436 if let &Ok(ref out) = command_output {
1437 if out.status.success() {
1438 if let Ok(of) = fs::OpenOptions::new().write(true).open(out_filename) {
1448 fn command_line_too_big(err: &io::Error) -> bool {
1449 err.raw_os_error() == Some(::libc::E2BIG)
1453 fn command_line_too_big(err: &io::Error) -> bool {
1454 const ERROR_FILENAME_EXCED_RANGE: i32 = 206;
1455 err.raw_os_error() == Some(ERROR_FILENAME_EXCED_RANGE)
1458 #[cfg(not(any(unix, windows)))]
1459 fn command_line_too_big(_: &io::Error) -> bool {
1468 impl<'a> fmt::Display for Escape<'a> {
1469 fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
1470 if self.is_like_msvc {
1471 // This is "documented" at
1472 // https://docs.microsoft.com/en-us/cpp/build/reference/at-specify-a-linker-response-file
1474 // Unfortunately there's not a great specification of the
1475 // syntax I could find online (at least) but some local
1476 // testing showed that this seemed sufficient-ish to catch
1477 // at least a few edge cases.
1479 for c in self.arg.chars() {
1481 '"' => write!(f, "\\{}", c)?,
1482 c => write!(f, "{}", c)?,
1487 // This is documented at https://linux.die.net/man/1/ld, namely:
1489 // > Options in file are separated by whitespace. A whitespace
1490 // > character may be included in an option by surrounding the
1491 // > entire option in either single or double quotes. Any
1492 // > character (including a backslash) may be included by
1493 // > prefixing the character to be included with a backslash.
1495 // We put an argument on each line, so all we need to do is
1496 // ensure the line is interpreted as one whole argument.
1497 for c in self.arg.chars() {
1499 '\\' | ' ' => write!(f, "\\{}", c)?,
1500 c => write!(f, "{}", c)?,
1509 fn link_output_kind(sess: &Session, crate_type: CrateType) -> LinkOutputKind {
1510 let kind = match (crate_type, sess.crt_static(Some(crate_type)), sess.relocation_model()) {
1511 (CrateType::Executable, _, _) if sess.is_wasi_reactor() => LinkOutputKind::WasiReactorExe,
1512 (CrateType::Executable, false, RelocModel::Pic | RelocModel::Pie) => {
1513 LinkOutputKind::DynamicPicExe
1515 (CrateType::Executable, false, _) => LinkOutputKind::DynamicNoPicExe,
1516 (CrateType::Executable, true, RelocModel::Pic | RelocModel::Pie) => {
1517 LinkOutputKind::StaticPicExe
1519 (CrateType::Executable, true, _) => LinkOutputKind::StaticNoPicExe,
1520 (_, true, _) => LinkOutputKind::StaticDylib,
1521 (_, false, _) => LinkOutputKind::DynamicDylib,
1524 // Adjust the output kind to target capabilities.
1525 let opts = &sess.target;
1526 let pic_exe_supported = opts.position_independent_executables;
1527 let static_pic_exe_supported = opts.static_position_independent_executables;
1528 let static_dylib_supported = opts.crt_static_allows_dylibs;
1530 LinkOutputKind::DynamicPicExe if !pic_exe_supported => LinkOutputKind::DynamicNoPicExe,
1531 LinkOutputKind::StaticPicExe if !static_pic_exe_supported => LinkOutputKind::StaticNoPicExe,
1532 LinkOutputKind::StaticDylib if !static_dylib_supported => LinkOutputKind::DynamicDylib,
1537 // Returns true if linker is located within sysroot
1538 fn detect_self_contained_mingw(sess: &Session) -> bool {
1539 let (linker, _) = linker_and_flavor(&sess);
1540 // Assume `-C linker=rust-lld` as self-contained mode
1541 if linker == Path::new("rust-lld") {
1544 let linker_with_extension = if cfg!(windows) && linker.extension().is_none() {
1545 linker.with_extension("exe")
1549 for dir in env::split_paths(&env::var_os("PATH").unwrap_or_default()) {
1550 let full_path = dir.join(&linker_with_extension);
1551 // If linker comes from sysroot assume self-contained mode
1552 if full_path.is_file() && !full_path.starts_with(&sess.sysroot) {
1559 /// Whether we link to our own CRT objects instead of relying on gcc to pull them.
1560 /// We only provide such support for a very limited number of targets.
1561 fn crt_objects_fallback(sess: &Session, crate_type: CrateType) -> bool {
1562 if let Some(self_contained) = sess.opts.cg.link_self_contained {
1563 return self_contained;
1566 match sess.target.crt_objects_fallback {
1567 // FIXME: Find a better heuristic for "native musl toolchain is available",
1568 // based on host and linker path, for example.
1569 // (https://github.com/rust-lang/rust/pull/71769#issuecomment-626330237).
1570 Some(CrtObjectsFallback::Musl) => sess.crt_static(Some(crate_type)),
1571 Some(CrtObjectsFallback::Mingw) => {
1572 sess.host == sess.target
1573 && sess.target.vendor != "uwp"
1574 && detect_self_contained_mingw(&sess)
1576 // FIXME: Figure out cases in which WASM needs to link with a native toolchain.
1577 Some(CrtObjectsFallback::Wasm) => true,
1582 /// Add pre-link object files defined by the target spec.
1583 fn add_pre_link_objects(
1584 cmd: &mut dyn Linker,
1586 link_output_kind: LinkOutputKind,
1587 self_contained: bool,
1589 let opts = &sess.target;
1591 if self_contained { &opts.pre_link_objects_fallback } else { &opts.pre_link_objects };
1592 for obj in objects.get(&link_output_kind).iter().copied().flatten() {
1593 cmd.add_object(&get_object_file_path(sess, obj, self_contained));
1597 /// Add post-link object files defined by the target spec.
1598 fn add_post_link_objects(
1599 cmd: &mut dyn Linker,
1601 link_output_kind: LinkOutputKind,
1602 self_contained: bool,
1604 let opts = &sess.target;
1606 if self_contained { &opts.post_link_objects_fallback } else { &opts.post_link_objects };
1607 for obj in objects.get(&link_output_kind).iter().copied().flatten() {
1608 cmd.add_object(&get_object_file_path(sess, obj, self_contained));
1612 /// Add arbitrary "pre-link" args defined by the target spec or from command line.
1613 /// FIXME: Determine where exactly these args need to be inserted.
1614 fn add_pre_link_args(cmd: &mut dyn Linker, sess: &Session, flavor: LinkerFlavor) {
1615 if let Some(args) = sess.target.pre_link_args.get(&flavor) {
1618 cmd.args(&sess.opts.debugging_opts.pre_link_args);
1621 /// Add a link script embedded in the target, if applicable.
1622 fn add_link_script(cmd: &mut dyn Linker, sess: &Session, tmpdir: &Path, crate_type: CrateType) {
1623 match (crate_type, &sess.target.link_script) {
1624 (CrateType::Cdylib | CrateType::Executable, Some(script)) => {
1625 if !sess.target.linker_is_gnu {
1626 sess.fatal("can only use link script when linking with GNU-like linker");
1629 let file_name = ["rustc", &sess.target.llvm_target, "linkfile.ld"].join("-");
1631 let path = tmpdir.join(file_name);
1632 if let Err(e) = fs::write(&path, script) {
1633 sess.fatal(&format!("failed to write link script to {}: {}", path.display(), e));
1636 cmd.arg("--script");
1643 /// Add arbitrary "user defined" args defined from command line.
1644 /// FIXME: Determine where exactly these args need to be inserted.
1645 fn add_user_defined_link_args(cmd: &mut dyn Linker, sess: &Session) {
1646 cmd.args(&sess.opts.cg.link_args);
1649 /// Add arbitrary "late link" args defined by the target spec.
1650 /// FIXME: Determine where exactly these args need to be inserted.
1651 fn add_late_link_args(
1652 cmd: &mut dyn Linker,
1654 flavor: LinkerFlavor,
1655 crate_type: CrateType,
1656 codegen_results: &CodegenResults,
1658 let any_dynamic_crate = crate_type == CrateType::Dylib
1659 || codegen_results.crate_info.dependency_formats.iter().any(|(ty, list)| {
1660 *ty == crate_type && list.iter().any(|&linkage| linkage == Linkage::Dynamic)
1662 if any_dynamic_crate {
1663 if let Some(args) = sess.target.late_link_args_dynamic.get(&flavor) {
1667 if let Some(args) = sess.target.late_link_args_static.get(&flavor) {
1671 if let Some(args) = sess.target.late_link_args.get(&flavor) {
1676 /// Add arbitrary "post-link" args defined by the target spec.
1677 /// FIXME: Determine where exactly these args need to be inserted.
1678 fn add_post_link_args(cmd: &mut dyn Linker, sess: &Session, flavor: LinkerFlavor) {
1679 if let Some(args) = sess.target.post_link_args.get(&flavor) {
1684 /// Add object files containing code from the current crate.
1685 fn add_local_crate_regular_objects(cmd: &mut dyn Linker, codegen_results: &CodegenResults) {
1686 for obj in codegen_results.modules.iter().filter_map(|m| m.object.as_ref()) {
1687 cmd.add_object(obj);
1691 /// Add object files for allocator code linked once for the whole crate tree.
1692 fn add_local_crate_allocator_objects(cmd: &mut dyn Linker, codegen_results: &CodegenResults) {
1693 if let Some(obj) = codegen_results.allocator_module.as_ref().and_then(|m| m.object.as_ref()) {
1694 cmd.add_object(obj);
1698 /// Add object files containing metadata for the current crate.
1699 fn add_local_crate_metadata_objects(
1700 cmd: &mut dyn Linker,
1701 crate_type: CrateType,
1702 codegen_results: &CodegenResults,
1704 // When linking a dynamic library, we put the metadata into a section of the
1705 // executable. This metadata is in a separate object file from the main
1706 // object file, so we link that in here.
1707 if crate_type == CrateType::Dylib || crate_type == CrateType::ProcMacro {
1708 if let Some(obj) = codegen_results.metadata_module.as_ref().and_then(|m| m.object.as_ref())
1710 cmd.add_object(obj);
1715 /// Add sysroot and other globally set directories to the directory search list.
1716 fn add_library_search_dirs(cmd: &mut dyn Linker, sess: &Session, self_contained: bool) {
1717 // The default library location, we need this to find the runtime.
1718 // The location of crates will be determined as needed.
1719 let lib_path = sess.target_filesearch(PathKind::All).get_lib_path();
1720 cmd.include_path(&fix_windows_verbatim_for_gcc(&lib_path));
1722 // Special directory with libraries used only in self-contained linkage mode
1724 let lib_path = sess.target_filesearch(PathKind::All).get_self_contained_lib_path();
1725 cmd.include_path(&fix_windows_verbatim_for_gcc(&lib_path));
1729 /// Add options making relocation sections in the produced ELF files read-only
1730 /// and suppressing lazy binding.
1731 fn add_relro_args(cmd: &mut dyn Linker, sess: &Session) {
1732 match sess.opts.debugging_opts.relro_level.unwrap_or(sess.target.relro_level) {
1733 RelroLevel::Full => cmd.full_relro(),
1734 RelroLevel::Partial => cmd.partial_relro(),
1735 RelroLevel::Off => cmd.no_relro(),
1736 RelroLevel::None => {}
1740 /// Add library search paths used at runtime by dynamic linkers.
1742 cmd: &mut dyn Linker,
1744 codegen_results: &CodegenResults,
1745 out_filename: &Path,
1747 // FIXME (#2397): At some point we want to rpath our guesses as to
1748 // where extern libraries might live, based on the
1749 // add_lib_search_paths
1750 if sess.opts.cg.rpath {
1751 let libs = codegen_results
1755 .filter_map(|cnum| {
1756 codegen_results.crate_info.used_crate_source[cnum]
1759 .map(|(path, _)| &**path)
1761 .collect::<Vec<_>>();
1762 let mut rpath_config = RPathConfig {
1764 out_filename: out_filename.to_path_buf(),
1765 has_rpath: sess.target.has_rpath,
1766 is_like_osx: sess.target.is_like_osx,
1767 linker_is_gnu: sess.target.linker_is_gnu,
1769 cmd.args(&rpath::get_rpath_flags(&mut rpath_config));
1773 /// Produce the linker command line containing linker path and arguments.
1775 /// When comments in the function say "order-(in)dependent" they mean order-dependence between
1776 /// options and libraries/object files. For example `--whole-archive` (order-dependent) applies
1777 /// to specific libraries passed after it, and `-o` (output file, order-independent) applies
1778 /// to the linking process as a whole.
1779 /// Order-independent options may still override each other in order-dependent fashion,
1780 /// e.g `--foo=yes --foo=no` may be equivalent to `--foo=no`.
1781 fn linker_with_args<'a, B: ArchiveBuilder<'a>>(
1783 flavor: LinkerFlavor,
1785 crate_type: CrateType,
1787 out_filename: &Path,
1788 codegen_results: &CodegenResults,
1790 let crt_objects_fallback = crt_objects_fallback(sess, crate_type);
1791 let cmd = &mut *super::linker::get_linker(
1795 crt_objects_fallback,
1796 &codegen_results.crate_info.target_cpu,
1798 let link_output_kind = link_output_kind(sess, crate_type);
1800 // ------------ Early order-dependent options ------------
1802 // If we're building something like a dynamic library then some platforms
1803 // need to make sure that all symbols are exported correctly from the
1805 // Must be passed before any libraries to prevent the symbols to export from being thrown away,
1806 // at least on some platforms (e.g. windows-gnu).
1810 &codegen_results.crate_info.exported_symbols[&crate_type],
1813 // Can be used for adding custom CRT objects or overriding order-dependent options above.
1814 // FIXME: In practice built-in target specs use this for arbitrary order-independent options,
1815 // introduce a target spec option for order-independent linker options and migrate built-in
1817 add_pre_link_args(cmd, sess, flavor);
1819 // ------------ Object code and libraries, order-dependent ------------
1821 // Pre-link CRT objects.
1822 add_pre_link_objects(cmd, sess, link_output_kind, crt_objects_fallback);
1824 // Sanitizer libraries.
1825 add_sanitizer_libraries(sess, crate_type, cmd);
1827 // Object code from the current crate.
1828 // Take careful note of the ordering of the arguments we pass to the linker
1829 // here. Linkers will assume that things on the left depend on things to the
1830 // right. Things on the right cannot depend on things on the left. This is
1831 // all formally implemented in terms of resolving symbols (libs on the right
1832 // resolve unknown symbols of libs on the left, but not vice versa).
1834 // For this reason, we have organized the arguments we pass to the linker as
1837 // 1. The local object that LLVM just generated
1838 // 2. Local native libraries
1839 // 3. Upstream rust libraries
1840 // 4. Upstream native libraries
1842 // The rationale behind this ordering is that those items lower down in the
1843 // list can't depend on items higher up in the list. For example nothing can
1844 // depend on what we just generated (e.g., that'd be a circular dependency).
1845 // Upstream rust libraries are not supposed to depend on our local native
1846 // libraries as that would violate the structure of the DAG, in that
1847 // scenario they are required to link to them as well in a shared fashion.
1848 // (The current implementation still doesn't prevent it though, see the FIXME below.)
1850 // Note that upstream rust libraries may contain native dependencies as
1851 // well, but they also can't depend on what we just started to add to the
1852 // link line. And finally upstream native libraries can't depend on anything
1853 // in this DAG so far because they can only depend on other native libraries
1854 // and such dependencies are also required to be specified.
1855 add_local_crate_regular_objects(cmd, codegen_results);
1856 add_local_crate_metadata_objects(cmd, crate_type, codegen_results);
1857 add_local_crate_allocator_objects(cmd, codegen_results);
1859 // Avoid linking to dynamic libraries unless they satisfy some undefined symbols
1860 // at the point at which they are specified on the command line.
1861 // Must be passed before any (dynamic) libraries to have effect on them.
1862 // On Solaris-like systems, `-z ignore` acts as both `--as-needed` and `--gc-sections`
1863 // so it will ignore unreferenced ELF sections from relocatable objects.
1864 // For that reason, we put this flag after metadata objects as they would otherwise be removed.
1865 // FIXME: Support more fine-grained dead code removal on Solaris/illumos
1866 // and move this option back to the top.
1867 cmd.add_as_needed();
1869 // FIXME: Move this below to other native libraries
1870 // (or alternatively link all native libraries after their respective crates).
1871 // This change is somewhat breaking in practice due to local static libraries being linked
1872 // as whole-archive (#85144), so removing whole-archive may be a pre-requisite.
1873 if sess.opts.debugging_opts.link_native_libraries {
1874 add_local_native_libraries(cmd, sess, codegen_results);
1877 // Upstream rust libraries and their nobundle static libraries
1878 add_upstream_rust_crates::<B>(cmd, sess, codegen_results, crate_type, tmpdir);
1880 // Upstream dymamic native libraries linked with `#[link]` attributes at and `-l`
1881 // command line options.
1882 // If -Zlink-native-libraries=false is set, then the assumption is that an
1883 // external build system already has the native dependencies defined, and it
1884 // will provide them to the linker itself.
1885 if sess.opts.debugging_opts.link_native_libraries {
1886 add_upstream_native_libraries(cmd, sess, codegen_results);
1889 // Library linking above uses some global state for things like `-Bstatic`/`-Bdynamic` to make
1890 // command line shorter, reset it to default here before adding more libraries.
1891 cmd.reset_per_library_state();
1893 // FIXME: Built-in target specs occasionally use this for linking system libraries,
1894 // eliminate all such uses by migrating them to `#[link]` attributes in `lib(std,c,unwind)`
1895 // and remove the option.
1896 add_late_link_args(cmd, sess, flavor, crate_type, codegen_results);
1898 // ------------ Arbitrary order-independent options ------------
1900 // Add order-independent options determined by rustc from its compiler options,
1901 // target properties and source code.
1902 add_order_independent_options(
1906 crt_objects_fallback,
1914 // Can be used for arbitrary order-independent options.
1915 // In practice may also be occasionally used for linking native libraries.
1916 // Passed after compiler-generated options to support manual overriding when necessary.
1917 add_user_defined_link_args(cmd, sess);
1919 // ------------ Object code and libraries, order-dependent ------------
1921 // Post-link CRT objects.
1922 add_post_link_objects(cmd, sess, link_output_kind, crt_objects_fallback);
1924 // ------------ Late order-dependent options ------------
1926 // Doesn't really make sense.
1927 // FIXME: In practice built-in target specs use this for arbitrary order-independent options,
1928 // introduce a target spec option for order-independent linker options, migrate built-in specs
1929 // to it and remove the option.
1930 add_post_link_args(cmd, sess, flavor);
1935 fn add_order_independent_options(
1936 cmd: &mut dyn Linker,
1938 link_output_kind: LinkOutputKind,
1939 crt_objects_fallback: bool,
1940 flavor: LinkerFlavor,
1941 crate_type: CrateType,
1942 codegen_results: &CodegenResults,
1943 out_filename: &Path,
1946 add_gcc_ld_path(cmd, sess, flavor);
1948 add_apple_sdk(cmd, sess, flavor);
1950 add_link_script(cmd, sess, tmpdir, crate_type);
1952 if sess.target.is_like_fuchsia && crate_type == CrateType::Executable {
1953 let prefix = if sess.opts.debugging_opts.sanitizer.contains(SanitizerSet::ADDRESS) {
1958 cmd.arg(format!("--dynamic-linker={}ld.so.1", prefix));
1961 if sess.target.eh_frame_header {
1962 cmd.add_eh_frame_header();
1965 // Make the binary compatible with data execution prevention schemes.
1968 if crt_objects_fallback {
1969 cmd.no_crt_objects();
1972 if sess.target.is_like_emscripten {
1974 cmd.arg(if sess.panic_strategy() == PanicStrategy::Abort {
1975 "DISABLE_EXCEPTION_CATCHING=1"
1977 "DISABLE_EXCEPTION_CATCHING=0"
1981 if flavor == LinkerFlavor::PtxLinker {
1982 // Provide the linker with fallback to internal `target-cpu`.
1983 cmd.arg("--fallback-arch");
1984 cmd.arg(&codegen_results.crate_info.target_cpu);
1985 } else if flavor == LinkerFlavor::BpfLinker {
1987 cmd.arg(&codegen_results.crate_info.target_cpu);
1988 cmd.arg("--cpu-features");
1989 cmd.arg(match &sess.opts.cg.target_feature {
1990 feat if !feat.is_empty() => feat,
1991 _ => &sess.target.options.features,
1995 cmd.linker_plugin_lto();
1997 add_library_search_dirs(cmd, sess, crt_objects_fallback);
1999 cmd.output_filename(out_filename);
2001 if crate_type == CrateType::Executable && sess.target.is_like_windows {
2002 if let Some(ref s) = codegen_results.crate_info.windows_subsystem {
2007 // Try to strip as much out of the generated object by removing unused
2008 // sections if possible. See more comments in linker.rs
2009 if !sess.link_dead_code() {
2010 // If PGO is enabled sometimes gc_sections will remove the profile data section
2011 // as it appears to be unused. This can then cause the PGO profile file to lose
2012 // some functions. If we are generating a profile we shouldn't strip those metadata
2013 // sections to ensure we have all the data for PGO.
2015 crate_type == CrateType::Dylib || sess.opts.cg.profile_generate.enabled();
2016 cmd.gc_sections(keep_metadata);
2019 cmd.set_output_kind(link_output_kind, out_filename);
2021 add_relro_args(cmd, sess);
2023 // Pass optimization flags down to the linker.
2026 // Pass debuginfo and strip flags down to the linker.
2027 cmd.debuginfo(strip_value(sess));
2029 // We want to prevent the compiler from accidentally leaking in any system libraries,
2030 // so by default we tell linkers not to link to any default libraries.
2031 if !sess.opts.cg.default_linker_libraries && sess.target.no_default_libraries {
2032 cmd.no_default_libraries();
2035 if sess.opts.cg.profile_generate.enabled() || sess.instrument_coverage() {
2039 if sess.opts.cg.control_flow_guard != CFGuard::Disabled {
2040 cmd.control_flow_guard();
2043 add_rpath_args(cmd, sess, codegen_results, out_filename);
2046 /// # Native library linking
2048 /// User-supplied library search paths (-L on the command line). These are the same paths used to
2049 /// find Rust crates, so some of them may have been added already by the previous crate linking
2050 /// code. This only allows them to be found at compile time so it is still entirely up to outside
2051 /// forces to make sure that library can be found at runtime.
2053 /// Also note that the native libraries linked here are only the ones located in the current crate.
2054 /// Upstream crates with native library dependencies may have their native library pulled in above.
2055 fn add_local_native_libraries(
2056 cmd: &mut dyn Linker,
2058 codegen_results: &CodegenResults,
2060 let filesearch = sess.target_filesearch(PathKind::All);
2061 for search_path in filesearch.search_paths() {
2062 match search_path.kind {
2063 PathKind::Framework => {
2064 cmd.framework_path(&search_path.dir);
2067 cmd.include_path(&fix_windows_verbatim_for_gcc(&search_path.dir));
2073 codegen_results.crate_info.used_libraries.iter().filter(|l| relevant_lib(sess, l));
2075 let search_path = OnceCell::new();
2076 let mut last = (NativeLibKind::Unspecified, None);
2077 for lib in relevant_libs {
2078 let name = match lib.name {
2083 // Skip if this library is the same as the last.
2084 last = if (lib.kind, lib.name) == last { continue } else { (lib.kind, lib.name) };
2086 let verbatim = lib.verbatim.unwrap_or(false);
2088 NativeLibKind::Dylib { as_needed } => {
2089 cmd.link_dylib(name, verbatim, as_needed.unwrap_or(true))
2091 NativeLibKind::Unspecified => cmd.link_dylib(name, verbatim, true),
2092 NativeLibKind::Framework { as_needed } => {
2093 cmd.link_framework(name, as_needed.unwrap_or(true))
2095 NativeLibKind::Static { bundle: None | Some(true), .. }
2096 | NativeLibKind::Static { whole_archive: Some(true), .. } => {
2097 cmd.link_whole_staticlib(
2100 &search_path.get_or_init(|| archive_search_paths(sess)),
2103 NativeLibKind::Static { .. } => cmd.link_staticlib(name, verbatim),
2104 NativeLibKind::RawDylib => {
2105 // FIXME(#58713): Proper handling for raw dylibs.
2106 bug!("raw_dylib feature not yet implemented");
2112 /// # Linking Rust crates and their nobundle static libraries
2114 /// Rust crates are not considered at all when creating an rlib output. All dependencies will be
2115 /// linked when producing the final output (instead of the intermediate rlib version).
2116 fn add_upstream_rust_crates<'a, B: ArchiveBuilder<'a>>(
2117 cmd: &mut dyn Linker,
2119 codegen_results: &CodegenResults,
2120 crate_type: CrateType,
2123 // All of the heavy lifting has previously been accomplished by the
2124 // dependency_format module of the compiler. This is just crawling the
2125 // output of that module, adding crates as necessary.
2127 // Linking to a rlib involves just passing it to the linker (the linker
2128 // will slurp up the object files inside), and linking to a dynamic library
2129 // involves just passing the right -l flag.
2131 let (_, data) = codegen_results
2135 .find(|(ty, _)| *ty == crate_type)
2136 .expect("failed to find crate type in dependency format list");
2138 // Invoke get_used_crates to ensure that we get a topological sorting of
2140 let deps = &codegen_results.crate_info.used_crates;
2142 // There's a few internal crates in the standard library (aka libcore and
2143 // libstd) which actually have a circular dependence upon one another. This
2144 // currently arises through "weak lang items" where libcore requires things
2145 // like `rust_begin_unwind` but libstd ends up defining it. To get this
2146 // circular dependence to work correctly in all situations we'll need to be
2147 // sure to correctly apply the `--start-group` and `--end-group` options to
2148 // GNU linkers, otherwise if we don't use any other symbol from the standard
2149 // library it'll get discarded and the whole application won't link.
2151 // In this loop we're calculating the `group_end`, after which crate to
2152 // pass `--end-group` and `group_start`, before which crate to pass
2153 // `--start-group`. We currently do this by passing `--end-group` after
2154 // the first crate (when iterating backwards) that requires a lang item
2155 // defined somewhere else. Once that's set then when we've defined all the
2156 // necessary lang items we'll pass `--start-group`.
2158 // Note that this isn't amazing logic for now but it should do the trick
2159 // for the current implementation of the standard library.
2160 let mut group_end = None;
2161 let mut group_start = None;
2162 // Crates available for linking thus far.
2163 let mut available = FxHashSet::default();
2164 // Crates required to satisfy dependencies discovered so far.
2165 let mut required = FxHashSet::default();
2167 let info = &codegen_results.crate_info;
2168 for &cnum in deps.iter().rev() {
2169 if let Some(missing) = info.missing_lang_items.get(&cnum) {
2170 let missing_crates = missing.iter().map(|i| info.lang_item_to_crate.get(i).copied());
2171 required.extend(missing_crates);
2174 required.insert(Some(cnum));
2175 available.insert(Some(cnum));
2177 if required.len() > available.len() && group_end.is_none() {
2178 group_end = Some(cnum);
2180 if required.len() == available.len() && group_end.is_some() {
2181 group_start = Some(cnum);
2186 // If we didn't end up filling in all lang items from upstream crates then
2187 // we'll be filling it in with our crate. This probably means we're the
2188 // standard library itself, so skip this for now.
2189 if group_end.is_some() && group_start.is_none() {
2193 let mut compiler_builtins = None;
2194 let search_path = OnceCell::new();
2196 for &cnum in deps.iter() {
2197 if group_start == Some(cnum) {
2201 // We may not pass all crates through to the linker. Some crates may
2202 // appear statically in an existing dylib, meaning we'll pick up all the
2203 // symbols from the dylib.
2204 let src = &codegen_results.crate_info.used_crate_source[&cnum];
2205 match data[cnum.as_usize() - 1] {
2206 _ if codegen_results.crate_info.profiler_runtime == Some(cnum) => {
2207 add_static_crate::<B>(cmd, sess, codegen_results, tmpdir, crate_type, cnum);
2209 // compiler-builtins are always placed last to ensure that they're
2210 // linked correctly.
2211 _ if codegen_results.crate_info.compiler_builtins == Some(cnum) => {
2212 assert!(compiler_builtins.is_none());
2213 compiler_builtins = Some(cnum);
2215 Linkage::NotLinked | Linkage::IncludedFromDylib => {}
2216 Linkage::Static => {
2217 add_static_crate::<B>(cmd, sess, codegen_results, tmpdir, crate_type, cnum);
2219 // Link static native libs with "-bundle" modifier only if the crate they originate from
2220 // is being linked statically to the current crate. If it's linked dynamically
2221 // or is an rlib already included via some other dylib crate, the symbols from
2222 // native libs will have already been included in that dylib.
2224 // If -Zlink-native-libraries=false is set, then the assumption is that an
2225 // external build system already has the native dependencies defined, and it
2226 // will provide them to the linker itself.
2227 if sess.opts.debugging_opts.link_native_libraries {
2228 let mut last = None;
2229 for lib in &codegen_results.crate_info.native_libraries[&cnum] {
2230 if !relevant_lib(sess, lib) {
2231 // Skip libraries if they are disabled by `#[link(cfg=...)]`
2235 // Skip if this library is the same as the last.
2236 if last == lib.name {
2240 if let Some(static_lib_name) = lib.name {
2241 if let NativeLibKind::Static { bundle: Some(false), whole_archive } =
2244 let verbatim = lib.verbatim.unwrap_or(false);
2245 if whole_archive == Some(true) {
2246 cmd.link_whole_staticlib(
2249 search_path.get_or_init(|| archive_search_paths(sess)),
2252 cmd.link_staticlib(static_lib_name, verbatim);
2261 Linkage::Dynamic => add_dynamic_crate(cmd, sess, &src.dylib.as_ref().unwrap().0),
2264 if group_end == Some(cnum) {
2269 // compiler-builtins are always placed last to ensure that they're
2270 // linked correctly.
2271 // We must always link the `compiler_builtins` crate statically. Even if it
2272 // was already "included" in a dylib (e.g., `libstd` when `-C prefer-dynamic`
2274 if let Some(cnum) = compiler_builtins {
2275 add_static_crate::<B>(cmd, sess, codegen_results, tmpdir, crate_type, cnum);
2278 // Converts a library file-stem into a cc -l argument
2279 fn unlib<'a>(target: &Target, stem: &'a str) -> &'a str {
2280 if stem.starts_with("lib") && !target.is_like_windows { &stem[3..] } else { stem }
2283 // Adds the static "rlib" versions of all crates to the command line.
2284 // There's a bit of magic which happens here specifically related to LTO,
2285 // namely that we remove upstream object files.
2287 // When performing LTO, almost(*) all of the bytecode from the upstream
2288 // libraries has already been included in our object file output. As a
2289 // result we need to remove the object files in the upstream libraries so
2290 // the linker doesn't try to include them twice (or whine about duplicate
2291 // symbols). We must continue to include the rest of the rlib, however, as
2292 // it may contain static native libraries which must be linked in.
2294 // (*) Crates marked with `#![no_builtins]` don't participate in LTO and
2295 // their bytecode wasn't included. The object files in those libraries must
2296 // still be passed to the linker.
2298 // Note, however, that if we're not doing LTO we can just pass the rlib
2299 // blindly to the linker (fast) because it's fine if it's not actually
2300 // included as we're at the end of the dependency chain.
2301 fn add_static_crate<'a, B: ArchiveBuilder<'a>>(
2302 cmd: &mut dyn Linker,
2304 codegen_results: &CodegenResults,
2306 crate_type: CrateType,
2309 let src = &codegen_results.crate_info.used_crate_source[&cnum];
2310 let cratepath = &src.rlib.as_ref().unwrap().0;
2312 let mut link_upstream = |path: &Path| {
2313 // If we're creating a dylib, then we need to include the
2314 // whole of each object in our archive into that artifact. This is
2315 // because a `dylib` can be reused as an intermediate artifact.
2317 // Note, though, that we don't want to include the whole of a
2318 // compiler-builtins crate (e.g., compiler-rt) because it'll get
2319 // repeatedly linked anyway.
2320 let path = fix_windows_verbatim_for_gcc(path);
2321 if crate_type == CrateType::Dylib
2322 && codegen_results.crate_info.compiler_builtins != Some(cnum)
2324 cmd.link_whole_rlib(&path);
2326 cmd.link_rlib(&path);
2330 // See the comment above in `link_staticlib` and `link_rlib` for why if
2331 // there's a static library that's not relevant we skip all object
2333 let native_libs = &codegen_results.crate_info.native_libraries[&cnum];
2334 let skip_native = native_libs.iter().any(|lib| {
2335 matches!(lib.kind, NativeLibKind::Static { bundle: None | Some(true), .. })
2336 && !relevant_lib(sess, lib)
2339 if (!are_upstream_rust_objects_already_included(sess)
2340 || ignored_for_lto(sess, &codegen_results.crate_info, cnum))
2343 link_upstream(cratepath);
2347 let dst = tmpdir.join(cratepath.file_name().unwrap());
2348 let name = cratepath.file_name().unwrap().to_str().unwrap();
2349 let name = &name[3..name.len() - 5]; // chop off lib/.rlib
2351 sess.prof.generic_activity_with_arg("link_altering_rlib", name).run(|| {
2352 let mut archive = <B as ArchiveBuilder>::new(sess, &dst, Some(cratepath));
2353 archive.update_symbols();
2355 let mut any_objects = false;
2356 for f in archive.src_files() {
2357 if f == METADATA_FILENAME {
2358 archive.remove_file(&f);
2362 let canonical = f.replace("-", "_");
2363 let canonical_name = name.replace("-", "_");
2365 let is_rust_object =
2366 canonical.starts_with(&canonical_name) && looks_like_rust_object_file(&f);
2368 // If we've been requested to skip all native object files
2369 // (those not generated by the rust compiler) then we can skip
2370 // this file. See above for why we may want to do this.
2371 let skip_because_cfg_say_so = skip_native && !is_rust_object;
2373 // If we're performing LTO and this is a rust-generated object
2374 // file, then we don't need the object file as it's part of the
2375 // LTO module. Note that `#![no_builtins]` is excluded from LTO,
2376 // though, so we let that object file slide.
2377 let skip_because_lto = are_upstream_rust_objects_already_included(sess)
2379 && (sess.target.no_builtins
2380 || !codegen_results.crate_info.is_no_builtins.contains(&cnum));
2382 if skip_because_cfg_say_so || skip_because_lto {
2383 archive.remove_file(&f);
2393 link_upstream(&dst);
2397 // Same thing as above, but for dynamic crates instead of static crates.
2398 fn add_dynamic_crate(cmd: &mut dyn Linker, sess: &Session, cratepath: &Path) {
2399 // Just need to tell the linker about where the library lives and
2401 let parent = cratepath.parent();
2402 if let Some(dir) = parent {
2403 cmd.include_path(&fix_windows_verbatim_for_gcc(dir));
2405 let filestem = cratepath.file_stem().unwrap().to_str().unwrap();
2406 cmd.link_rust_dylib(
2407 Symbol::intern(&unlib(&sess.target, filestem)),
2408 parent.unwrap_or_else(|| Path::new("")),
2413 /// Link in all of our upstream crates' native dependencies. Remember that all of these upstream
2414 /// native dependencies are all non-static dependencies. We've got two cases then:
2416 /// 1. The upstream crate is an rlib. In this case we *must* link in the native dependency because
2417 /// the rlib is just an archive.
2419 /// 2. The upstream crate is a dylib. In order to use the dylib, we have to have the dependency
2420 /// present on the system somewhere. Thus, we don't gain a whole lot from not linking in the
2421 /// dynamic dependency to this crate as well.
2423 /// The use case for this is a little subtle. In theory the native dependencies of a crate are
2424 /// purely an implementation detail of the crate itself, but the problem arises with generic and
2425 /// inlined functions. If a generic function calls a native function, then the generic function
2426 /// must be instantiated in the target crate, meaning that the native symbol must also be resolved
2427 /// in the target crate.
2428 fn add_upstream_native_libraries(
2429 cmd: &mut dyn Linker,
2431 codegen_results: &CodegenResults,
2433 let mut last = (NativeLibKind::Unspecified, None);
2434 for &cnum in &codegen_results.crate_info.used_crates {
2435 for lib in codegen_results.crate_info.native_libraries[&cnum].iter() {
2436 let name = match lib.name {
2440 if !relevant_lib(sess, &lib) {
2444 // Skip if this library is the same as the last.
2445 last = if (lib.kind, lib.name) == last { continue } else { (lib.kind, lib.name) };
2447 let verbatim = lib.verbatim.unwrap_or(false);
2449 NativeLibKind::Dylib { as_needed } => {
2450 cmd.link_dylib(name, verbatim, as_needed.unwrap_or(true))
2452 NativeLibKind::Unspecified => cmd.link_dylib(name, verbatim, true),
2453 NativeLibKind::Framework { as_needed } => {
2454 cmd.link_framework(name, as_needed.unwrap_or(true))
2456 // ignore static native libraries here as we've
2457 // already included them in add_local_native_libraries and
2458 // add_upstream_rust_crates
2459 NativeLibKind::Static { .. } => {}
2460 NativeLibKind::RawDylib => {}
2466 fn relevant_lib(sess: &Session, lib: &NativeLib) -> bool {
2468 Some(ref cfg) => rustc_attr::cfg_matches(cfg, &sess.parse_sess, None),
2473 fn are_upstream_rust_objects_already_included(sess: &Session) -> bool {
2475 config::Lto::Fat => true,
2476 config::Lto::Thin => {
2477 // If we defer LTO to the linker, we haven't run LTO ourselves, so
2478 // any upstream object files have not been copied yet.
2479 !sess.opts.cg.linker_plugin_lto.enabled()
2481 config::Lto::No | config::Lto::ThinLocal => false,
2485 fn add_apple_sdk(cmd: &mut dyn Linker, sess: &Session, flavor: LinkerFlavor) {
2486 let arch = &sess.target.arch;
2487 let os = &sess.target.os;
2488 let llvm_target = &sess.target.llvm_target;
2489 if sess.target.vendor != "apple"
2490 || !matches!(os.as_str(), "ios" | "tvos")
2491 || flavor != LinkerFlavor::Gcc
2495 let sdk_name = match (arch.as_str(), os.as_str()) {
2496 ("aarch64", "tvos") => "appletvos",
2497 ("x86_64", "tvos") => "appletvsimulator",
2498 ("arm", "ios") => "iphoneos",
2499 ("aarch64", "ios") if llvm_target.contains("macabi") => "macosx",
2500 ("aarch64", "ios") if llvm_target.contains("sim") => "iphonesimulator",
2501 ("aarch64", "ios") => "iphoneos",
2502 ("x86", "ios") => "iphonesimulator",
2503 ("x86_64", "ios") if llvm_target.contains("macabi") => "macosx",
2504 ("x86_64", "ios") => "iphonesimulator",
2506 sess.err(&format!("unsupported arch `{}` for os `{}`", arch, os));
2510 let sdk_root = match get_apple_sdk_root(sdk_name) {
2517 if llvm_target.contains("macabi") {
2518 cmd.args(&["-target", llvm_target])
2520 let arch_name = llvm_target.split('-').next().expect("LLVM target must have a hyphen");
2521 cmd.args(&["-arch", arch_name])
2523 cmd.args(&["-isysroot", &sdk_root, "-Wl,-syslibroot", &sdk_root]);
2526 fn get_apple_sdk_root(sdk_name: &str) -> Result<String, String> {
2527 // Following what clang does
2528 // (https://github.com/llvm/llvm-project/blob/
2529 // 296a80102a9b72c3eda80558fb78a3ed8849b341/clang/lib/Driver/ToolChains/Darwin.cpp#L1661-L1678)
2530 // to allow the SDK path to be set. (For clang, xcrun sets
2531 // SDKROOT; for rustc, the user or build system can set it, or we
2532 // can fall back to checking for xcrun on PATH.)
2533 if let Ok(sdkroot) = env::var("SDKROOT") {
2534 let p = Path::new(&sdkroot);
2536 // Ignore `SDKROOT` if it's clearly set for the wrong platform.
2538 if sdkroot.contains("TVSimulator.platform")
2539 || sdkroot.contains("MacOSX.platform") => {}
2541 if sdkroot.contains("TVOS.platform") || sdkroot.contains("MacOSX.platform") => {}
2543 if sdkroot.contains("iPhoneSimulator.platform")
2544 || sdkroot.contains("MacOSX.platform") => {}
2546 if sdkroot.contains("iPhoneOS.platform") || sdkroot.contains("MacOSX.platform") => {
2549 if sdkroot.contains("iPhoneOS.platform")
2550 || sdkroot.contains("iPhoneSimulator.platform") => {}
2551 // Ignore `SDKROOT` if it's not a valid path.
2552 _ if !p.is_absolute() || p == Path::new("/") || !p.exists() => {}
2553 _ => return Ok(sdkroot),
2557 Command::new("xcrun").arg("--show-sdk-path").arg("-sdk").arg(sdk_name).output().and_then(
2559 if output.status.success() {
2560 Ok(String::from_utf8(output.stdout).unwrap())
2562 let error = String::from_utf8(output.stderr);
2563 let error = format!("process exit with error: {}", error.unwrap());
2564 Err(io::Error::new(io::ErrorKind::Other, &error[..]))
2570 Ok(output) => Ok(output.trim().to_string()),
2571 Err(e) => Err(format!("failed to get {} SDK path: {}", sdk_name, e)),
2575 fn add_gcc_ld_path(cmd: &mut dyn Linker, sess: &Session, flavor: LinkerFlavor) {
2576 if let Some(ld_impl) = sess.opts.debugging_opts.gcc_ld {
2577 if let LinkerFlavor::Gcc = flavor {
2580 if sess.target.lld_flavor == LldFlavor::Ld64 {
2581 let tools_path = sess.get_tools_search_paths(false);
2582 let ld64_exe = tools_path
2584 .map(|p| p.join("gcc-ld"))
2586 p.join(if sess.host.is_like_windows { "ld64.exe" } else { "ld64" })
2588 .find(|p| p.exists())
2589 .unwrap_or_else(|| sess.fatal("rust-lld (as ld64) not found"));
2591 let mut arg = OsString::from("-fuse-ld=");
2596 let tools_path = sess.get_tools_search_paths(false);
2597 let lld_path = tools_path
2599 .map(|p| p.join("gcc-ld"))
2601 p.join(if sess.host.is_like_windows { "ld.exe" } else { "ld" })
2604 .unwrap_or_else(|| sess.fatal("rust-lld (as ld) not found"));
2606 let mut arg = OsString::from("-B");
2614 sess.fatal("option `-Z gcc-ld` is used even though linker flavor is not gcc");