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");
127 // Remove the temporary object file and metadata if we aren't saving temps
128 sess.time("link_binary_remove_temps", || {
129 if !sess.opts.cg.save_temps {
130 let remove_temps_from_module = |module: &CompiledModule| {
131 if let Some(ref obj) = module.object {
132 ensure_removed(sess.diagnostic(), obj);
135 if let Some(ref obj) = module.dwarf_object {
136 ensure_removed(sess.diagnostic(), obj);
140 if sess.opts.output_types.should_link() && !preserve_objects_for_their_debuginfo(sess) {
141 for module in &codegen_results.modules {
142 remove_temps_from_module(module);
146 if let Some(ref metadata_module) = codegen_results.metadata_module {
147 remove_temps_from_module(metadata_module);
150 if let Some(ref allocator_module) = codegen_results.allocator_module {
151 remove_temps_from_module(allocator_module);
159 pub fn each_linked_rlib(
161 f: &mut dyn FnMut(CrateNum, &Path),
162 ) -> Result<(), String> {
163 let crates = info.used_crates.iter();
165 for (ty, list) in info.dependency_formats.iter() {
167 CrateType::Executable
168 | CrateType::Staticlib
170 | CrateType::ProcMacro => {
177 let fmts = match fmts {
179 None => return Err("could not find formats for rlibs".to_string()),
181 for &cnum in crates {
182 match fmts.get(cnum.as_usize() - 1) {
183 Some(&Linkage::NotLinked | &Linkage::IncludedFromDylib) => continue,
185 None => return Err("could not find formats for rlibs".to_string()),
187 let name = &info.crate_name[&cnum];
188 let used_crate_source = &info.used_crate_source[&cnum];
189 let path = if let Some((path, _)) = &used_crate_source.rlib {
191 } else if used_crate_source.rmeta.is_some() {
193 "could not find rlib for: `{}`, found rmeta (metadata) file",
197 return Err(format!("could not find rlib for: `{}`", name));
204 /// We use a temp directory here to avoid races between concurrent rustc processes,
205 /// such as builds in the same directory using the same filename for metadata while
206 /// building an `.rlib` (stomping over one another), or writing an `.rmeta` into a
207 /// directory being searched for `extern crate` (observing an incomplete file).
208 /// The returned path is the temporary file containing the complete metadata.
209 pub fn emit_metadata(sess: &Session, metadata: &[u8], tmpdir: &MaybeTempDir) -> PathBuf {
210 let out_filename = tmpdir.as_ref().join(METADATA_FILENAME);
211 let result = fs::write(&out_filename, metadata);
213 if let Err(e) = result {
214 sess.fatal(&format!("failed to write {}: {}", out_filename.display(), e));
220 /// Create an 'rlib'.
222 /// An rlib in its current incarnation is essentially a renamed .a file. The rlib primarily contains
223 /// the object file of the crate, but it also contains all of the object files from native
224 /// libraries. This is done by unzipping native libraries and inserting all of the contents into
226 fn link_rlib<'a, B: ArchiveBuilder<'a>>(
228 codegen_results: &CodegenResults,
231 tmpdir: &MaybeTempDir,
232 ) -> Result<B, ErrorReported> {
233 info!("preparing rlib to {:?}", out_filename);
235 let lib_search_paths = archive_search_paths(sess);
237 let mut ab = <B as ArchiveBuilder>::new(sess, out_filename, None);
239 for obj in codegen_results.modules.iter().filter_map(|m| m.object.as_ref()) {
243 // Note that in this loop we are ignoring the value of `lib.cfg`. That is,
244 // we may not be configured to actually include a static library if we're
245 // adding it here. That's because later when we consume this rlib we'll
246 // decide whether we actually needed the static library or not.
248 // To do this "correctly" we'd need to keep track of which libraries added
249 // which object files to the archive. We don't do that here, however. The
250 // #[link(cfg(..))] feature is unstable, though, and only intended to get
251 // liblibc working. In that sense the check below just indicates that if
252 // there are any libraries we want to omit object files for at link time we
253 // just exclude all custom object files.
255 // Eventually if we want to stabilize or flesh out the #[link(cfg(..))]
256 // feature then we'll need to figure out how to record what objects were
257 // loaded from the libraries found here and then encode that into the
258 // metadata of the rlib we're generating somehow.
259 for lib in codegen_results.crate_info.used_libraries.iter() {
261 NativeLibKind::Static { bundle: None | Some(true), whole_archive: Some(true) }
262 if flavor == RlibFlavor::Normal =>
264 // Don't allow mixing +bundle with +whole_archive since an rlib may contain
265 // multiple native libs, some of which are +whole-archive and some of which are
266 // -whole-archive and it isn't clear how we can currently handle such a
267 // situation correctly.
268 // See https://github.com/rust-lang/rust/issues/88085#issuecomment-901050897
270 "the linking modifiers `+bundle` and `+whole-archive` are not compatible \
271 with each other when generating rlibs",
274 NativeLibKind::Static { bundle: None | Some(true), .. } => {}
275 NativeLibKind::Static { bundle: Some(false), .. }
276 | NativeLibKind::Dylib { .. }
277 | NativeLibKind::Framework { .. }
278 | NativeLibKind::RawDylib
279 | NativeLibKind::Unspecified => continue,
281 if let Some(name) = lib.name {
283 find_library(name, lib.verbatim.unwrap_or(false), &lib_search_paths, sess);
284 ab.add_archive(&location, |_| false).unwrap_or_else(|e| {
286 "failed to add native library {}: {}",
287 location.to_string_lossy(),
294 for (raw_dylib_name, raw_dylib_imports) in
295 collate_raw_dylibs(sess, &codegen_results.crate_info.used_libraries)?
297 ab.inject_dll_import_lib(&raw_dylib_name, &raw_dylib_imports, tmpdir);
300 // After adding all files to the archive, we need to update the
301 // symbol table of the archive.
304 // Note that it is important that we add all of our non-object "magical
305 // files" *after* all of the object files in the archive. The reason for
306 // this is as follows:
308 // * When performing LTO, this archive will be modified to remove
309 // objects from above. The reason for this is described below.
311 // * When the system linker looks at an archive, it will attempt to
312 // determine the architecture of the archive in order to see whether its
315 // The algorithm for this detection is: iterate over the files in the
316 // archive. Skip magical SYMDEF names. Interpret the first file as an
317 // object file. Read architecture from the object file.
319 // * As one can probably see, if "metadata" and "foo.bc" were placed
320 // before all of the objects, then the architecture of this archive would
321 // not be correctly inferred once 'foo.o' is removed.
323 // Basically, all this means is that this code should not move above the
326 RlibFlavor::Normal => {
327 // metadata in rlib files is wrapped in a "dummy" object file for
328 // the target platform so the rlib can be processed entirely by
329 // normal linkers for the platform.
330 let metadata = create_metadata_file(sess, codegen_results.metadata.raw_data());
331 ab.add_file(&emit_metadata(sess, &metadata, tmpdir));
333 // After adding all files to the archive, we need to update the
334 // symbol table of the archive. This currently dies on macOS (see
335 // #11162), and isn't necessary there anyway
336 if !sess.target.is_like_osx {
341 RlibFlavor::StaticlibBase => {
342 let obj = codegen_results.allocator_module.as_ref().and_then(|m| m.object.as_ref());
343 if let Some(obj) = obj {
350 // For rlibs we "pack" rustc metadata into a dummy object file. When rustc
351 // creates a dylib crate type it will pass `--whole-archive` (or the
352 // platform equivalent) to include all object files from an rlib into the
353 // final dylib itself. This causes linkers to iterate and try to include all
354 // files located in an archive, so if metadata is stored in an archive then
355 // it needs to be of a form that the linker will be able to process.
357 // Note, though, that we don't actually want this metadata to show up in any
358 // final output of the compiler. Instead this is purely for rustc's own
359 // metadata tracking purposes.
361 // With the above in mind, each "flavor" of object format gets special
362 // handling here depending on the target:
364 // * MachO - macos-like targets will insert the metadata into a section that
365 // is sort of fake dwarf debug info. Inspecting the source of the macos
366 // linker this causes these sections to be skipped automatically because
367 // it's not in an allowlist of otherwise well known dwarf section names to
368 // go into the final artifact.
370 // * WebAssembly - we actually don't have any container format for this
371 // target. WebAssembly doesn't support the `dylib` crate type anyway so
372 // there's no need for us to support this at this time. Consequently the
373 // metadata bytes are simply stored as-is into an rlib.
375 // * COFF - Windows-like targets create an object with a section that has
376 // the `IMAGE_SCN_LNK_REMOVE` flag set which ensures that if the linker
377 // ever sees the section it doesn't process it and it's removed.
379 // * ELF - All other targets are similar to Windows in that there's a
380 // `SHF_EXCLUDE` flag we can set on sections in an object file to get
381 // automatically removed from the final output.
383 // Note that this metdata format is kept in sync with
384 // `rustc_codegen_ssa/src/back/metadata.rs`.
385 fn create_metadata_file(sess: &Session, metadata: &[u8]) -> Vec<u8> {
386 let endianness = match sess.target.options.endian {
387 Endian::Little => Endianness::Little,
388 Endian::Big => Endianness::Big,
390 let architecture = match &sess.target.arch[..] {
391 "arm" => Architecture::Arm,
392 "aarch64" => Architecture::Aarch64,
393 "x86" => Architecture::I386,
394 "s390x" => Architecture::S390x,
395 "mips" => Architecture::Mips,
396 "mips64" => Architecture::Mips64,
398 if sess.target.pointer_width == 32 {
399 Architecture::X86_64_X32
404 "powerpc" => Architecture::PowerPc,
405 "powerpc64" => Architecture::PowerPc64,
406 "riscv32" => Architecture::Riscv32,
407 "riscv64" => Architecture::Riscv64,
408 "sparc64" => Architecture::Sparc64,
410 // This is used to handle all "other" targets. This includes targets
411 // in two categories:
413 // * Some targets don't have support in the `object` crate just yet
414 // to write an object file. These targets are likely to get filled
417 // * Targets like WebAssembly don't support dylibs, so the purpose
418 // of putting metadata in object files, to support linking rlibs
419 // into dylibs, is moot.
421 // In both of these cases it means that linking into dylibs will
422 // not be supported by rustc. This doesn't matter for targets like
423 // WebAssembly and for targets not supported by the `object` crate
424 // yet it means that work will need to be done in the `object` crate
425 // to add a case above.
426 _ => return metadata.to_vec(),
429 if sess.target.is_like_osx {
430 let mut file = Object::new(BinaryFormat::MachO, architecture, endianness);
433 file.add_section(b"__DWARF".to_vec(), b".rmeta".to_vec(), SectionKind::Debug);
434 file.append_section_data(section, metadata, 1);
435 file.write().unwrap()
436 } else if sess.target.is_like_windows {
437 const IMAGE_SCN_LNK_REMOVE: u32 = 0;
438 let mut file = Object::new(BinaryFormat::Coff, architecture, endianness);
440 let section = file.add_section(Vec::new(), b".rmeta".to_vec(), SectionKind::Debug);
441 file.section_mut(section).flags =
442 SectionFlags::Coff { characteristics: IMAGE_SCN_LNK_REMOVE };
443 file.append_section_data(section, metadata, 1);
444 file.write().unwrap()
446 const SHF_EXCLUDE: u64 = 0x80000000;
447 let mut file = Object::new(BinaryFormat::Elf, architecture, endianness);
449 match &sess.target.arch[..] {
450 // copied from `mipsel-linux-gnu-gcc foo.c -c` and
451 // inspecting the resulting `e_flags` field.
453 let e_flags = elf::EF_MIPS_ARCH_32R2 | elf::EF_MIPS_CPIC | elf::EF_MIPS_PIC;
454 file.flags = FileFlags::Elf { e_flags };
456 // copied from `mips64el-linux-gnuabi64-gcc foo.c -c`
458 let e_flags = elf::EF_MIPS_ARCH_64R2 | elf::EF_MIPS_CPIC | elf::EF_MIPS_PIC;
459 file.flags = FileFlags::Elf { e_flags };
462 // copied from `riscv64-linux-gnu-gcc foo.c -c`, note though
463 // that the `+d` target feature represents whether the double
464 // float abi is enabled.
465 "riscv64" if sess.target.options.features.contains("+d") => {
466 let e_flags = elf::EF_RISCV_RVC | elf::EF_RISCV_FLOAT_ABI_DOUBLE;
467 file.flags = FileFlags::Elf { e_flags };
473 let section = file.add_section(Vec::new(), b".rmeta".to_vec(), SectionKind::Debug);
474 file.section_mut(section).flags = SectionFlags::Elf { sh_flags: SHF_EXCLUDE };
475 file.append_section_data(section, metadata, 1);
476 file.write().unwrap()
481 /// Extract all symbols defined in raw-dylib libraries, collated by library name.
483 /// If we have multiple extern blocks that specify symbols defined in the same raw-dylib library,
484 /// then the CodegenResults value contains one NativeLib instance for each block. However, the
485 /// linker appears to expect only a single import library for each library used, so we need to
486 /// collate the symbols together by library name before generating the import libraries.
487 fn collate_raw_dylibs(
489 used_libraries: &[NativeLib],
490 ) -> Result<Vec<(String, Vec<DllImport>)>, ErrorReported> {
491 // Use index maps to preserve original order of imports and libraries.
492 let mut dylib_table = FxIndexMap::<String, FxIndexMap<Symbol, &DllImport>>::default();
494 for lib in used_libraries {
495 if lib.kind == NativeLibKind::RawDylib {
496 let ext = if matches!(lib.verbatim, Some(true)) { "" } else { ".dll" };
497 let name = format!("{}{}", lib.name.expect("unnamed raw-dylib library"), ext);
498 let imports = dylib_table.entry(name.clone()).or_default();
499 for import in &lib.dll_imports {
500 if let Some(old_import) = imports.insert(import.name, import) {
501 // FIXME: when we add support for ordinals, figure out if we need to do anything
502 // if we have two DllImport values with the same name but different ordinals.
503 if import.calling_convention != old_import.calling_convention {
507 "multiple declarations of external function `{}` from \
508 library `{}` have different calling conventions",
517 sess.compile_status()?;
520 .map(|(name, imports)| {
521 (name, imports.into_iter().map(|(_, import)| import.clone()).collect())
526 /// Create a static archive.
528 /// This is essentially the same thing as an rlib, but it also involves adding all of the upstream
529 /// crates' objects into the archive. This will slurp in all of the native libraries of upstream
530 /// dependencies as well.
532 /// Additionally, there's no way for us to link dynamic libraries, so we warn about all dynamic
533 /// library dependencies that they're not linked in.
535 /// There's no need to include metadata in a static archive, so ensure to not link in the metadata
536 /// object file (and also don't prepare the archive with a metadata file).
537 fn link_staticlib<'a, B: ArchiveBuilder<'a>>(
539 codegen_results: &CodegenResults,
541 tempdir: &MaybeTempDir,
542 ) -> Result<(), ErrorReported> {
544 link_rlib::<B>(sess, codegen_results, RlibFlavor::StaticlibBase, out_filename, tempdir)?;
545 let mut all_native_libs = vec![];
547 let res = each_linked_rlib(&codegen_results.crate_info, &mut |cnum, path| {
548 let name = &codegen_results.crate_info.crate_name[&cnum];
549 let native_libs = &codegen_results.crate_info.native_libraries[&cnum];
551 // Here when we include the rlib into our staticlib we need to make a
552 // decision whether to include the extra object files along the way.
553 // These extra object files come from statically included native
554 // libraries, but they may be cfg'd away with #[link(cfg(..))].
556 // This unstable feature, though, only needs liblibc to work. The only
557 // use case there is where musl is statically included in liblibc.rlib,
558 // so if we don't want the included version we just need to skip it. As
559 // a result the logic here is that if *any* linked library is cfg'd away
560 // we just skip all object files.
562 // Clearly this is not sufficient for a general purpose feature, and
563 // we'd want to read from the library's metadata to determine which
564 // object files come from where and selectively skip them.
565 let skip_object_files = native_libs.iter().any(|lib| {
566 matches!(lib.kind, NativeLibKind::Static { bundle: None | Some(true), .. })
567 && !relevant_lib(sess, lib)
570 let lto = are_upstream_rust_objects_already_included(sess)
571 && !ignored_for_lto(sess, &codegen_results.crate_info, cnum);
573 // Ignoring obj file starting with the crate name
574 // as simple comparison is not enough - there
575 // might be also an extra name suffix
576 let obj_start = name.as_str().to_owned();
578 ab.add_archive(path, move |fname: &str| {
579 // Ignore metadata files, no matter the name.
580 if fname == METADATA_FILENAME {
584 // Don't include Rust objects if LTO is enabled
585 if lto && looks_like_rust_object_file(fname) {
589 // Otherwise if this is *not* a rust object and we're skipping
590 // objects then skip this file
591 if skip_object_files && (!fname.starts_with(&obj_start) || !fname.ends_with(".o")) {
595 // ok, don't skip this
600 all_native_libs.extend(codegen_results.crate_info.native_libraries[&cnum].iter().cloned());
602 if let Err(e) = res {
609 if !all_native_libs.is_empty() {
610 if sess.opts.prints.contains(&PrintRequest::NativeStaticLibs) {
611 print_native_static_libs(sess, &all_native_libs);
618 fn escape_stdout_stderr_string(s: &[u8]) -> String {
619 str::from_utf8(s).map(|s| s.to_owned()).unwrap_or_else(|_| {
620 let mut x = "Non-UTF-8 output: ".to_string();
621 x.extend(s.iter().flat_map(|&b| ascii::escape_default(b)).map(char::from));
626 const LLVM_DWP_EXECUTABLE: &'static str = "rust-llvm-dwp";
628 /// Invoke `llvm-dwp` (shipped alongside rustc) to link `dwo` files from Split DWARF into a `dwp`
630 fn link_dwarf_object<'a>(sess: &'a Session, executable_out_filename: &Path) {
631 info!("preparing dwp to {}.dwp", executable_out_filename.to_str().unwrap());
633 let dwp_out_filename = executable_out_filename.with_extension("dwp");
634 let mut cmd = Command::new(LLVM_DWP_EXECUTABLE);
636 cmd.arg(executable_out_filename);
638 cmd.arg(&dwp_out_filename);
640 let mut new_path = sess.get_tools_search_paths(false);
641 if let Some(path) = env::var_os("PATH") {
642 new_path.extend(env::split_paths(&path));
644 let new_path = env::join_paths(new_path).unwrap();
645 cmd.env("PATH", new_path);
648 match sess.time("run_dwp", || cmd.output()) {
649 Ok(prog) if !prog.status.success() => {
650 sess.struct_err(&format!(
651 "linking dwarf objects with `{}` failed: {}",
652 LLVM_DWP_EXECUTABLE, prog.status
654 .note(&format!("{:?}", &cmd))
655 .note(&escape_stdout_stderr_string(&prog.stdout))
656 .note(&escape_stdout_stderr_string(&prog.stderr))
658 info!("linker stderr:\n{}", escape_stdout_stderr_string(&prog.stderr));
659 info!("linker stdout:\n{}", escape_stdout_stderr_string(&prog.stdout));
663 let dwp_not_found = e.kind() == io::ErrorKind::NotFound;
664 let mut err = if dwp_not_found {
665 sess.struct_err(&format!("linker `{}` not found", LLVM_DWP_EXECUTABLE))
667 sess.struct_err(&format!("could not exec the linker `{}`", LLVM_DWP_EXECUTABLE))
670 err.note(&e.to_string());
673 err.note(&format!("{:?}", &cmd));
681 /// Create a dynamic library or executable.
683 /// This will invoke the system linker/cc to create the resulting file. This links to all upstream
685 fn link_natively<'a, B: ArchiveBuilder<'a>>(
687 crate_type: CrateType,
689 codegen_results: &CodegenResults,
692 info!("preparing {:?} to {:?}", crate_type, out_filename);
693 let (linker_path, flavor) = linker_and_flavor(sess);
694 let mut cmd = linker_with_args::<B>(
704 linker::disable_localization(&mut cmd);
706 for &(ref k, ref v) in &sess.target.link_env {
709 for k in &sess.target.link_env_remove {
713 if sess.opts.debugging_opts.print_link_args {
714 println!("{:?}", &cmd);
717 // May have not found libraries in the right formats.
718 sess.abort_if_errors();
720 // Invoke the system linker
722 let retry_on_segfault = env::var("RUSTC_RETRY_LINKER_ON_SEGFAULT").is_ok();
723 let unknown_arg_regex =
724 Regex::new(r"(unknown|unrecognized) (command line )?(option|argument)").unwrap();
729 prog = sess.time("run_linker", || exec_linker(sess, &cmd, out_filename, tmpdir));
730 let output = match prog {
731 Ok(ref output) => output,
734 if output.status.success() {
737 let mut out = output.stderr.clone();
738 out.extend(&output.stdout);
739 let out = String::from_utf8_lossy(&out);
741 // Check to see if the link failed with an error message that indicates it
742 // doesn't recognize the -no-pie option. If so, reperform the link step
743 // without it. This is safe because if the linker doesn't support -no-pie
744 // then it should not default to linking executables as pie. Different
745 // versions of gcc seem to use different quotes in the error message so
746 // don't check for them.
747 if sess.target.linker_is_gnu
748 && flavor != LinkerFlavor::Ld
749 && unknown_arg_regex.is_match(&out)
750 && out.contains("-no-pie")
751 && cmd.get_args().iter().any(|e| e.to_string_lossy() == "-no-pie")
753 info!("linker output: {:?}", out);
754 warn!("Linker does not support -no-pie command line option. Retrying without.");
755 for arg in cmd.take_args() {
756 if arg.to_string_lossy() != "-no-pie" {
764 // Detect '-static-pie' used with an older version of gcc or clang not supporting it.
765 // Fallback from '-static-pie' to '-static' in that case.
766 if sess.target.linker_is_gnu
767 && flavor != LinkerFlavor::Ld
768 && unknown_arg_regex.is_match(&out)
769 && (out.contains("-static-pie") || out.contains("--no-dynamic-linker"))
770 && cmd.get_args().iter().any(|e| e.to_string_lossy() == "-static-pie")
772 info!("linker output: {:?}", out);
774 "Linker does not support -static-pie command line option. Retrying with -static instead."
776 // Mirror `add_(pre,post)_link_objects` to replace CRT objects.
777 let self_contained = crt_objects_fallback(sess, crate_type);
778 let opts = &sess.target;
779 let pre_objects = if self_contained {
780 &opts.pre_link_objects_fallback
782 &opts.pre_link_objects
784 let post_objects = if self_contained {
785 &opts.post_link_objects_fallback
787 &opts.post_link_objects
789 let get_objects = |objects: &CrtObjects, kind| {
795 .map(|obj| get_object_file_path(sess, obj, self_contained).into_os_string())
798 let pre_objects_static_pie = get_objects(pre_objects, LinkOutputKind::StaticPicExe);
799 let post_objects_static_pie = get_objects(post_objects, LinkOutputKind::StaticPicExe);
800 let mut pre_objects_static = get_objects(pre_objects, LinkOutputKind::StaticNoPicExe);
801 let mut post_objects_static = get_objects(post_objects, LinkOutputKind::StaticNoPicExe);
802 // Assume that we know insertion positions for the replacement arguments from replaced
803 // arguments, which is true for all supported targets.
804 assert!(pre_objects_static.is_empty() || !pre_objects_static_pie.is_empty());
805 assert!(post_objects_static.is_empty() || !post_objects_static_pie.is_empty());
806 for arg in cmd.take_args() {
807 if arg.to_string_lossy() == "-static-pie" {
808 // Replace the output kind.
810 } else if pre_objects_static_pie.contains(&arg) {
811 // Replace the pre-link objects (replace the first and remove the rest).
812 cmd.args(mem::take(&mut pre_objects_static));
813 } else if post_objects_static_pie.contains(&arg) {
814 // Replace the post-link objects (replace the first and remove the rest).
815 cmd.args(mem::take(&mut post_objects_static));
824 // Here's a terribly awful hack that really shouldn't be present in any
825 // compiler. Here an environment variable is supported to automatically
826 // retry the linker invocation if the linker looks like it segfaulted.
828 // Gee that seems odd, normally segfaults are things we want to know
829 // about! Unfortunately though in rust-lang/rust#38878 we're
830 // experiencing the linker segfaulting on Travis quite a bit which is
831 // causing quite a bit of pain to land PRs when they spuriously fail
832 // due to a segfault.
834 // The issue #38878 has some more debugging information on it as well,
835 // but this unfortunately looks like it's just a race condition in
836 // macOS's linker with some thread pool working in the background. It
837 // seems that no one currently knows a fix for this so in the meantime
838 // we're left with this...
839 if !retry_on_segfault || i > 3 {
842 let msg_segv = "clang: error: unable to execute command: Segmentation fault: 11";
843 let msg_bus = "clang: error: unable to execute command: Bus error: 10";
844 if out.contains(msg_segv) || out.contains(msg_bus) {
846 "looks like the linker segfaulted when we tried to call it, \
847 automatically retrying again",
853 if is_illegal_instruction(&output.status) {
855 "looks like the linker hit an illegal instruction when we \
856 tried to call it, automatically retrying again.",
857 ?cmd, %out, status = %output.status,
863 fn is_illegal_instruction(status: &ExitStatus) -> bool {
864 use std::os::unix::prelude::*;
865 status.signal() == Some(libc::SIGILL)
869 fn is_illegal_instruction(_status: &ExitStatus) -> bool {
876 if !prog.status.success() {
877 let mut output = prog.stderr.clone();
878 output.extend_from_slice(&prog.stdout);
879 let escaped_output = escape_stdout_stderr_string(&output);
880 let mut err = sess.struct_err(&format!(
881 "linking with `{}` failed: {}",
882 linker_path.display(),
885 err.note(&format!("{:?}", &cmd)).note(&escaped_output);
886 if escaped_output.contains("undefined reference to") {
888 "some `extern` functions couldn't be found; some native libraries may \
889 need to be installed or have their path specified",
891 err.note("use the `-l` flag to specify native libraries to link");
892 err.note("use the `cargo:rustc-link-lib` directive to specify the native \
893 libraries to link with Cargo (see https://doc.rust-lang.org/cargo/reference/build-scripts.html#cargorustc-link-libkindname)");
897 // If MSVC's `link.exe` was expected but the return code
898 // is not a Microsoft LNK error then suggest a way to fix or
899 // install the Visual Studio build tools.
900 if let Some(code) = prog.status.code() {
901 if sess.target.is_like_msvc
902 && flavor == LinkerFlavor::Msvc
903 // Respect the command line override
904 && sess.opts.cg.linker.is_none()
905 // Match exactly "link.exe"
906 && linker_path.to_str() == Some("link.exe")
907 // All Microsoft `link.exe` linking error codes are
908 // four digit numbers in the range 1000 to 9999 inclusive
909 && (code < 1000 || code > 9999)
911 let is_vs_installed = windows_registry::find_vs_version().is_ok();
912 let has_linker = windows_registry::find_tool(
913 &sess.opts.target_triple.triple(),
918 sess.note_without_error("`link.exe` returned an unexpected error");
919 if is_vs_installed && has_linker {
920 // the linker is broken
921 sess.note_without_error(
922 "the Visual Studio build tools may need to be repaired \
923 using the Visual Studio installer",
925 sess.note_without_error(
926 "or a necessary component may be missing from the \
927 \"C++ build tools\" workload",
929 } else if is_vs_installed {
930 // the linker is not installed
931 sess.note_without_error(
932 "in the Visual Studio installer, ensure the \
933 \"C++ build tools\" workload is selected",
936 // visual studio is not installed
937 sess.note_without_error(
938 "you may need to install Visual Studio build tools with the \
939 \"C++ build tools\" workload",
945 sess.abort_if_errors();
947 info!("linker stderr:\n{}", escape_stdout_stderr_string(&prog.stderr));
948 info!("linker stdout:\n{}", escape_stdout_stderr_string(&prog.stdout));
951 let linker_not_found = e.kind() == io::ErrorKind::NotFound;
953 let mut linker_error = {
954 if linker_not_found {
955 sess.struct_err(&format!("linker `{}` not found", linker_path.display()))
957 sess.struct_err(&format!(
958 "could not exec the linker `{}`",
959 linker_path.display()
964 linker_error.note(&e.to_string());
966 if !linker_not_found {
967 linker_error.note(&format!("{:?}", &cmd));
972 if sess.target.is_like_msvc && linker_not_found {
973 sess.note_without_error(
974 "the msvc targets depend on the msvc linker \
975 but `link.exe` was not found",
977 sess.note_without_error(
978 "please ensure that VS 2013, VS 2015, VS 2017 or VS 2019 \
979 was installed with the Visual C++ option",
982 sess.abort_if_errors();
986 match sess.split_debuginfo() {
987 // If split debug information is disabled or located in individual files
988 // there's nothing to do here.
989 SplitDebuginfo::Off | SplitDebuginfo::Unpacked => {}
991 // If packed split-debuginfo is requested, but the final compilation
992 // doesn't actually have any debug information, then we skip this step.
993 SplitDebuginfo::Packed if sess.opts.debuginfo == DebugInfo::None => {}
995 // On macOS the external `dsymutil` tool is used to create the packed
996 // debug information. Note that this will read debug information from
997 // the objects on the filesystem which we'll clean up later.
998 SplitDebuginfo::Packed if sess.target.is_like_osx => {
999 let prog = Command::new("dsymutil").arg(out_filename).output();
1002 if !prog.status.success() {
1003 let mut output = prog.stderr.clone();
1004 output.extend_from_slice(&prog.stdout);
1005 sess.struct_warn(&format!(
1006 "processing debug info with `dsymutil` failed: {}",
1009 .note(&escape_string(&output))
1013 Err(e) => sess.fatal(&format!("unable to run `dsymutil`: {}", e)),
1017 // On MSVC packed debug information is produced by the linker itself so
1018 // there's no need to do anything else here.
1019 SplitDebuginfo::Packed if sess.target.is_like_msvc => {}
1021 // ... and otherwise we're processing a `*.dwp` packed dwarf file.
1022 SplitDebuginfo::Packed => link_dwarf_object(sess, &out_filename),
1025 if sess.target.is_like_osx {
1026 if let Some(option) = osx_strip_opt(sess.opts.debugging_opts.strip) {
1027 strip_symbols_in_osx(sess, &out_filename, option);
1032 fn strip_symbols_in_osx<'a>(sess: &'a Session, out_filename: &Path, option: &str) {
1033 let prog = Command::new("strip").arg(option).arg(out_filename).output();
1036 if !prog.status.success() {
1037 let mut output = prog.stderr.clone();
1038 output.extend_from_slice(&prog.stdout);
1039 sess.struct_warn(&format!(
1040 "stripping debug info with `strip` failed: {}",
1043 .note(&escape_string(&output))
1047 Err(e) => sess.fatal(&format!("unable to run `strip`: {}", e)),
1051 fn osx_strip_opt<'a>(strip: Strip) -> Option<&'a str> {
1053 Strip::Debuginfo => Some("-S"),
1054 Strip::Symbols => Some("-x"),
1055 Strip::None => None,
1059 fn escape_string(s: &[u8]) -> String {
1060 str::from_utf8(s).map(|s| s.to_owned()).unwrap_or_else(|_| {
1061 let mut x = "Non-UTF-8 output: ".to_string();
1062 x.extend(s.iter().flat_map(|&b| ascii::escape_default(b)).map(char::from));
1067 fn add_sanitizer_libraries(sess: &Session, crate_type: CrateType, linker: &mut dyn Linker) {
1068 // On macOS the runtimes are distributed as dylibs which should be linked to
1069 // both executables and dynamic shared objects. Everywhere else the runtimes
1070 // are currently distributed as static liraries which should be linked to
1071 // executables only.
1072 let needs_runtime = match crate_type {
1073 CrateType::Executable => true,
1074 CrateType::Dylib | CrateType::Cdylib | CrateType::ProcMacro => sess.target.is_like_osx,
1075 CrateType::Rlib | CrateType::Staticlib => false,
1082 let sanitizer = sess.opts.debugging_opts.sanitizer;
1083 if sanitizer.contains(SanitizerSet::ADDRESS) {
1084 link_sanitizer_runtime(sess, linker, "asan");
1086 if sanitizer.contains(SanitizerSet::LEAK) {
1087 link_sanitizer_runtime(sess, linker, "lsan");
1089 if sanitizer.contains(SanitizerSet::MEMORY) {
1090 link_sanitizer_runtime(sess, linker, "msan");
1092 if sanitizer.contains(SanitizerSet::THREAD) {
1093 link_sanitizer_runtime(sess, linker, "tsan");
1095 if sanitizer.contains(SanitizerSet::HWADDRESS) {
1096 link_sanitizer_runtime(sess, linker, "hwasan");
1100 fn link_sanitizer_runtime(sess: &Session, linker: &mut dyn Linker, name: &str) {
1101 fn find_sanitizer_runtime(sess: &Session, filename: &String) -> PathBuf {
1103 filesearch::make_target_lib_path(&sess.sysroot, sess.opts.target_triple.triple());
1104 let path = session_tlib.join(&filename);
1106 return session_tlib;
1108 let default_sysroot = filesearch::get_or_default_sysroot();
1109 let default_tlib = filesearch::make_target_lib_path(
1111 sess.opts.target_triple.triple(),
1113 return default_tlib;
1117 let channel = option_env!("CFG_RELEASE_CHANNEL")
1118 .map(|channel| format!("-{}", channel))
1119 .unwrap_or_default();
1121 if sess.target.is_like_osx {
1122 // On Apple platforms, the sanitizer is always built as a dylib, and
1123 // LLVM will link to `@rpath/*.dylib`, so we need to specify an
1124 // rpath to the library as well (the rpath should be absolute, see
1125 // PR #41352 for details).
1126 let filename = format!("rustc{}_rt.{}", channel, name);
1127 let path = find_sanitizer_runtime(&sess, &filename);
1128 let rpath = path.to_str().expect("non-utf8 component in path");
1129 linker.args(&["-Wl,-rpath", "-Xlinker", rpath]);
1130 linker.link_dylib(Symbol::intern(&filename), false, true);
1132 let filename = format!("librustc{}_rt.{}.a", channel, name);
1133 let path = find_sanitizer_runtime(&sess, &filename).join(&filename);
1134 linker.link_whole_rlib(&path);
1138 /// Returns a boolean indicating whether the specified crate should be ignored
1141 /// Crates ignored during LTO are not lumped together in the "massive object
1142 /// file" that we create and are linked in their normal rlib states. See
1143 /// comments below for what crates do not participate in LTO.
1145 /// It's unusual for a crate to not participate in LTO. Typically only
1146 /// compiler-specific and unstable crates have a reason to not participate in
1148 pub fn ignored_for_lto(sess: &Session, info: &CrateInfo, cnum: CrateNum) -> bool {
1149 // If our target enables builtin function lowering in LLVM then the
1150 // crates providing these functions don't participate in LTO (e.g.
1151 // no_builtins or compiler builtins crates).
1152 !sess.target.no_builtins
1153 && (info.compiler_builtins == Some(cnum) || info.is_no_builtins.contains(&cnum))
1156 // This functions tries to determine the appropriate linker (and corresponding LinkerFlavor) to use
1157 pub fn linker_and_flavor(sess: &Session) -> (PathBuf, LinkerFlavor) {
1160 linker: Option<PathBuf>,
1161 flavor: Option<LinkerFlavor>,
1162 ) -> Option<(PathBuf, LinkerFlavor)> {
1163 match (linker, flavor) {
1164 (Some(linker), Some(flavor)) => Some((linker, flavor)),
1165 // only the linker flavor is known; use the default linker for the selected flavor
1166 (None, Some(flavor)) => Some((
1167 PathBuf::from(match flavor {
1168 LinkerFlavor::Em => {
1175 LinkerFlavor::Gcc => {
1176 if cfg!(any(target_os = "solaris", target_os = "illumos")) {
1177 // On historical Solaris systems, "cc" may have
1178 // been Sun Studio, which is not flag-compatible
1179 // with "gcc". This history casts a long shadow,
1180 // and many modern illumos distributions today
1181 // ship GCC as "gcc" without also making it
1182 // available as "cc".
1188 LinkerFlavor::Ld => "ld",
1189 LinkerFlavor::Msvc => "link.exe",
1190 LinkerFlavor::Lld(_) => "lld",
1191 LinkerFlavor::PtxLinker => "rust-ptx-linker",
1192 LinkerFlavor::BpfLinker => "bpf-linker",
1196 (Some(linker), None) => {
1197 let stem = linker.file_stem().and_then(|stem| stem.to_str()).unwrap_or_else(|| {
1198 sess.fatal("couldn't extract file stem from specified linker")
1201 let flavor = if stem == "emcc" {
1203 } else if stem == "gcc"
1204 || stem.ends_with("-gcc")
1206 || stem.ends_with("-clang")
1209 } else if stem == "wasm-ld" || stem.ends_with("-wasm-ld") {
1210 LinkerFlavor::Lld(LldFlavor::Wasm)
1211 } else if stem == "ld" || stem == "ld.lld" || stem.ends_with("-ld") {
1213 } else if stem == "link" || stem == "lld-link" {
1215 } else if stem == "lld" || stem == "rust-lld" {
1216 LinkerFlavor::Lld(sess.target.lld_flavor)
1218 // fall back to the value in the target spec
1219 sess.target.linker_flavor
1222 Some((linker, flavor))
1224 (None, None) => None,
1228 // linker and linker flavor specified via command line have precedence over what the target
1229 // specification specifies
1230 if let Some(ret) = infer_from(sess, sess.opts.cg.linker.clone(), sess.opts.cg.linker_flavor) {
1234 if let Some(ret) = infer_from(
1236 sess.target.linker.clone().map(PathBuf::from),
1237 Some(sess.target.linker_flavor),
1242 bug!("Not enough information provided to determine how to invoke the linker");
1245 /// Returns a boolean indicating whether we should preserve the object files on
1246 /// the filesystem for their debug information. This is often useful with
1247 /// split-dwarf like schemes.
1248 fn preserve_objects_for_their_debuginfo(sess: &Session) -> bool {
1249 // If the objects don't have debuginfo there's nothing to preserve.
1250 if sess.opts.debuginfo == config::DebugInfo::None {
1254 // If we're only producing artifacts that are archives, no need to preserve
1255 // the objects as they're losslessly contained inside the archives.
1257 sess.crate_types().iter().any(|&x| x != CrateType::Rlib && x != CrateType::Staticlib);
1262 // "unpacked" split debuginfo means that we leave object files as the
1263 // debuginfo is found in the original object files themselves
1264 sess.split_debuginfo() == SplitDebuginfo::Unpacked
1267 fn archive_search_paths(sess: &Session) -> Vec<PathBuf> {
1268 sess.target_filesearch(PathKind::Native).search_path_dirs()
1271 #[derive(PartialEq)]
1277 fn print_native_static_libs(sess: &Session, all_native_libs: &[NativeLib]) {
1278 let lib_args: Vec<_> = all_native_libs
1280 .filter(|l| relevant_lib(sess, l))
1282 let name = lib.name?;
1284 NativeLibKind::Static { bundle: Some(false), .. }
1285 | NativeLibKind::Dylib { .. }
1286 | NativeLibKind::Unspecified => {
1287 let verbatim = lib.verbatim.unwrap_or(false);
1288 if sess.target.is_like_msvc {
1289 Some(format!("{}{}", name, if verbatim { "" } else { ".lib" }))
1290 } else if sess.target.linker_is_gnu {
1291 Some(format!("-l{}{}", if verbatim { ":" } else { "" }, name))
1293 Some(format!("-l{}", name))
1296 NativeLibKind::Framework { .. } => {
1297 // ld-only syntax, since there are no frameworks in MSVC
1298 Some(format!("-framework {}", name))
1300 // These are included, no need to print them
1301 NativeLibKind::Static { bundle: None | Some(true), .. }
1302 | NativeLibKind::RawDylib => None,
1306 if !lib_args.is_empty() {
1307 sess.note_without_error(
1308 "Link against the following native artifacts when linking \
1309 against this static library. The order and any duplication \
1310 can be significant on some platforms.",
1312 // Prefix for greppability
1313 sess.note_without_error(&format!("native-static-libs: {}", &lib_args.join(" ")));
1317 fn get_object_file_path(sess: &Session, name: &str, self_contained: bool) -> PathBuf {
1318 let fs = sess.target_filesearch(PathKind::Native);
1319 let file_path = fs.get_lib_path().join(name);
1320 if file_path.exists() {
1323 // Special directory with objects used only in self-contained linkage mode
1325 let file_path = fs.get_self_contained_lib_path().join(name);
1326 if file_path.exists() {
1330 for search_path in fs.search_paths() {
1331 let file_path = search_path.dir.join(name);
1332 if file_path.exists() {
1342 out_filename: &Path,
1344 ) -> io::Result<Output> {
1345 // When attempting to spawn the linker we run a risk of blowing out the
1346 // size limits for spawning a new process with respect to the arguments
1347 // we pass on the command line.
1349 // Here we attempt to handle errors from the OS saying "your list of
1350 // arguments is too big" by reinvoking the linker again with an `@`-file
1351 // that contains all the arguments. The theory is that this is then
1352 // accepted on all linkers and the linker will read all its options out of
1353 // there instead of looking at the command line.
1354 if !cmd.very_likely_to_exceed_some_spawn_limit() {
1355 match cmd.command().stdout(Stdio::piped()).stderr(Stdio::piped()).spawn() {
1357 let output = child.wait_with_output();
1358 flush_linked_file(&output, out_filename)?;
1361 Err(ref e) if command_line_too_big(e) => {
1362 info!("command line to linker was too big: {}", e);
1364 Err(e) => return Err(e),
1368 info!("falling back to passing arguments to linker via an @-file");
1369 let mut cmd2 = cmd.clone();
1370 let mut args = String::new();
1371 for arg in cmd2.take_args() {
1373 &Escape { arg: arg.to_str().unwrap(), is_like_msvc: sess.target.is_like_msvc }
1378 let file = tmpdir.join("linker-arguments");
1379 let bytes = if sess.target.is_like_msvc {
1380 let mut out = Vec::with_capacity((1 + args.len()) * 2);
1381 // start the stream with a UTF-16 BOM
1382 for c in std::iter::once(0xFEFF).chain(args.encode_utf16()) {
1383 // encode in little endian
1385 out.push((c >> 8) as u8);
1391 fs::write(&file, &bytes)?;
1392 cmd2.arg(format!("@{}", file.display()));
1393 info!("invoking linker {:?}", cmd2);
1394 let output = cmd2.output();
1395 flush_linked_file(&output, out_filename)?;
1398 #[cfg(not(windows))]
1399 fn flush_linked_file(_: &io::Result<Output>, _: &Path) -> io::Result<()> {
1404 fn flush_linked_file(
1405 command_output: &io::Result<Output>,
1406 out_filename: &Path,
1407 ) -> io::Result<()> {
1408 // On Windows, under high I/O load, output buffers are sometimes not flushed,
1409 // even long after process exit, causing nasty, non-reproducible output bugs.
1411 // File::sync_all() calls FlushFileBuffers() down the line, which solves the problem.
1413 // А full writeup of the original Chrome bug can be found at
1414 // randomascii.wordpress.com/2018/02/25/compiler-bug-linker-bug-windows-kernel-bug/amp
1416 if let &Ok(ref out) = command_output {
1417 if out.status.success() {
1418 if let Ok(of) = fs::OpenOptions::new().write(true).open(out_filename) {
1428 fn command_line_too_big(err: &io::Error) -> bool {
1429 err.raw_os_error() == Some(::libc::E2BIG)
1433 fn command_line_too_big(err: &io::Error) -> bool {
1434 const ERROR_FILENAME_EXCED_RANGE: i32 = 206;
1435 err.raw_os_error() == Some(ERROR_FILENAME_EXCED_RANGE)
1438 #[cfg(not(any(unix, windows)))]
1439 fn command_line_too_big(_: &io::Error) -> bool {
1448 impl<'a> fmt::Display for Escape<'a> {
1449 fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
1450 if self.is_like_msvc {
1451 // This is "documented" at
1452 // https://docs.microsoft.com/en-us/cpp/build/reference/at-specify-a-linker-response-file
1454 // Unfortunately there's not a great specification of the
1455 // syntax I could find online (at least) but some local
1456 // testing showed that this seemed sufficient-ish to catch
1457 // at least a few edge cases.
1459 for c in self.arg.chars() {
1461 '"' => write!(f, "\\{}", c)?,
1462 c => write!(f, "{}", c)?,
1467 // This is documented at https://linux.die.net/man/1/ld, namely:
1469 // > Options in file are separated by whitespace. A whitespace
1470 // > character may be included in an option by surrounding the
1471 // > entire option in either single or double quotes. Any
1472 // > character (including a backslash) may be included by
1473 // > prefixing the character to be included with a backslash.
1475 // We put an argument on each line, so all we need to do is
1476 // ensure the line is interpreted as one whole argument.
1477 for c in self.arg.chars() {
1479 '\\' | ' ' => write!(f, "\\{}", c)?,
1480 c => write!(f, "{}", c)?,
1489 fn link_output_kind(sess: &Session, crate_type: CrateType) -> LinkOutputKind {
1490 let kind = match (crate_type, sess.crt_static(Some(crate_type)), sess.relocation_model()) {
1491 (CrateType::Executable, _, _) if sess.is_wasi_reactor() => LinkOutputKind::WasiReactorExe,
1492 (CrateType::Executable, false, RelocModel::Pic | RelocModel::Pie) => {
1493 LinkOutputKind::DynamicPicExe
1495 (CrateType::Executable, false, _) => LinkOutputKind::DynamicNoPicExe,
1496 (CrateType::Executable, true, RelocModel::Pic | RelocModel::Pie) => {
1497 LinkOutputKind::StaticPicExe
1499 (CrateType::Executable, true, _) => LinkOutputKind::StaticNoPicExe,
1500 (_, true, _) => LinkOutputKind::StaticDylib,
1501 (_, false, _) => LinkOutputKind::DynamicDylib,
1504 // Adjust the output kind to target capabilities.
1505 let opts = &sess.target;
1506 let pic_exe_supported = opts.position_independent_executables;
1507 let static_pic_exe_supported = opts.static_position_independent_executables;
1508 let static_dylib_supported = opts.crt_static_allows_dylibs;
1510 LinkOutputKind::DynamicPicExe if !pic_exe_supported => LinkOutputKind::DynamicNoPicExe,
1511 LinkOutputKind::StaticPicExe if !static_pic_exe_supported => LinkOutputKind::StaticNoPicExe,
1512 LinkOutputKind::StaticDylib if !static_dylib_supported => LinkOutputKind::DynamicDylib,
1517 // Returns true if linker is located within sysroot
1518 fn detect_self_contained_mingw(sess: &Session) -> bool {
1519 let (linker, _) = linker_and_flavor(&sess);
1520 // Assume `-C linker=rust-lld` as self-contained mode
1521 if linker == Path::new("rust-lld") {
1524 let linker_with_extension = if cfg!(windows) && linker.extension().is_none() {
1525 linker.with_extension("exe")
1529 for dir in env::split_paths(&env::var_os("PATH").unwrap_or_default()) {
1530 let full_path = dir.join(&linker_with_extension);
1531 // If linker comes from sysroot assume self-contained mode
1532 if full_path.is_file() && !full_path.starts_with(&sess.sysroot) {
1539 /// Whether we link to our own CRT objects instead of relying on gcc to pull them.
1540 /// We only provide such support for a very limited number of targets.
1541 fn crt_objects_fallback(sess: &Session, crate_type: CrateType) -> bool {
1542 if let Some(self_contained) = sess.opts.cg.link_self_contained {
1543 return self_contained;
1546 match sess.target.crt_objects_fallback {
1547 // FIXME: Find a better heuristic for "native musl toolchain is available",
1548 // based on host and linker path, for example.
1549 // (https://github.com/rust-lang/rust/pull/71769#issuecomment-626330237).
1550 Some(CrtObjectsFallback::Musl) => sess.crt_static(Some(crate_type)),
1551 Some(CrtObjectsFallback::Mingw) => {
1552 sess.host == sess.target
1553 && sess.target.vendor != "uwp"
1554 && detect_self_contained_mingw(&sess)
1556 // FIXME: Figure out cases in which WASM needs to link with a native toolchain.
1557 Some(CrtObjectsFallback::Wasm) => true,
1562 /// Add pre-link object files defined by the target spec.
1563 fn add_pre_link_objects(
1564 cmd: &mut dyn Linker,
1566 link_output_kind: LinkOutputKind,
1567 self_contained: bool,
1569 let opts = &sess.target;
1571 if self_contained { &opts.pre_link_objects_fallback } else { &opts.pre_link_objects };
1572 for obj in objects.get(&link_output_kind).iter().copied().flatten() {
1573 cmd.add_object(&get_object_file_path(sess, obj, self_contained));
1577 /// Add post-link object files defined by the target spec.
1578 fn add_post_link_objects(
1579 cmd: &mut dyn Linker,
1581 link_output_kind: LinkOutputKind,
1582 self_contained: bool,
1584 let opts = &sess.target;
1586 if self_contained { &opts.post_link_objects_fallback } else { &opts.post_link_objects };
1587 for obj in objects.get(&link_output_kind).iter().copied().flatten() {
1588 cmd.add_object(&get_object_file_path(sess, obj, self_contained));
1592 /// Add arbitrary "pre-link" args defined by the target spec or from command line.
1593 /// FIXME: Determine where exactly these args need to be inserted.
1594 fn add_pre_link_args(cmd: &mut dyn Linker, sess: &Session, flavor: LinkerFlavor) {
1595 if let Some(args) = sess.target.pre_link_args.get(&flavor) {
1598 cmd.args(&sess.opts.debugging_opts.pre_link_args);
1601 /// Add a link script embedded in the target, if applicable.
1602 fn add_link_script(cmd: &mut dyn Linker, sess: &Session, tmpdir: &Path, crate_type: CrateType) {
1603 match (crate_type, &sess.target.link_script) {
1604 (CrateType::Cdylib | CrateType::Executable, Some(script)) => {
1605 if !sess.target.linker_is_gnu {
1606 sess.fatal("can only use link script when linking with GNU-like linker");
1609 let file_name = ["rustc", &sess.target.llvm_target, "linkfile.ld"].join("-");
1611 let path = tmpdir.join(file_name);
1612 if let Err(e) = fs::write(&path, script) {
1613 sess.fatal(&format!("failed to write link script to {}: {}", path.display(), e));
1616 cmd.arg("--script");
1623 /// Add arbitrary "user defined" args defined from command line.
1624 /// FIXME: Determine where exactly these args need to be inserted.
1625 fn add_user_defined_link_args(cmd: &mut dyn Linker, sess: &Session) {
1626 cmd.args(&sess.opts.cg.link_args);
1629 /// Add arbitrary "late link" args defined by the target spec.
1630 /// FIXME: Determine where exactly these args need to be inserted.
1631 fn add_late_link_args(
1632 cmd: &mut dyn Linker,
1634 flavor: LinkerFlavor,
1635 crate_type: CrateType,
1636 codegen_results: &CodegenResults,
1638 let any_dynamic_crate = crate_type == CrateType::Dylib
1639 || codegen_results.crate_info.dependency_formats.iter().any(|(ty, list)| {
1640 *ty == crate_type && list.iter().any(|&linkage| linkage == Linkage::Dynamic)
1642 if any_dynamic_crate {
1643 if let Some(args) = sess.target.late_link_args_dynamic.get(&flavor) {
1647 if let Some(args) = sess.target.late_link_args_static.get(&flavor) {
1651 if let Some(args) = sess.target.late_link_args.get(&flavor) {
1656 /// Add arbitrary "post-link" args defined by the target spec.
1657 /// FIXME: Determine where exactly these args need to be inserted.
1658 fn add_post_link_args(cmd: &mut dyn Linker, sess: &Session, flavor: LinkerFlavor) {
1659 if let Some(args) = sess.target.post_link_args.get(&flavor) {
1664 /// Add object files containing code from the current crate.
1665 fn add_local_crate_regular_objects(cmd: &mut dyn Linker, codegen_results: &CodegenResults) {
1666 for obj in codegen_results.modules.iter().filter_map(|m| m.object.as_ref()) {
1667 cmd.add_object(obj);
1671 /// Add object files for allocator code linked once for the whole crate tree.
1672 fn add_local_crate_allocator_objects(cmd: &mut dyn Linker, codegen_results: &CodegenResults) {
1673 if let Some(obj) = codegen_results.allocator_module.as_ref().and_then(|m| m.object.as_ref()) {
1674 cmd.add_object(obj);
1678 /// Add object files containing metadata for the current crate.
1679 fn add_local_crate_metadata_objects(
1680 cmd: &mut dyn Linker,
1681 crate_type: CrateType,
1682 codegen_results: &CodegenResults,
1684 // When linking a dynamic library, we put the metadata into a section of the
1685 // executable. This metadata is in a separate object file from the main
1686 // object file, so we link that in here.
1687 if crate_type == CrateType::Dylib || crate_type == CrateType::ProcMacro {
1688 if let Some(obj) = codegen_results.metadata_module.as_ref().and_then(|m| m.object.as_ref())
1690 cmd.add_object(obj);
1695 /// Add sysroot and other globally set directories to the directory search list.
1696 fn add_library_search_dirs(cmd: &mut dyn Linker, sess: &Session, self_contained: bool) {
1697 // The default library location, we need this to find the runtime.
1698 // The location of crates will be determined as needed.
1699 let lib_path = sess.target_filesearch(PathKind::All).get_lib_path();
1700 cmd.include_path(&fix_windows_verbatim_for_gcc(&lib_path));
1702 // Special directory with libraries used only in self-contained linkage mode
1704 let lib_path = sess.target_filesearch(PathKind::All).get_self_contained_lib_path();
1705 cmd.include_path(&fix_windows_verbatim_for_gcc(&lib_path));
1709 /// Add options making relocation sections in the produced ELF files read-only
1710 /// and suppressing lazy binding.
1711 fn add_relro_args(cmd: &mut dyn Linker, sess: &Session) {
1712 match sess.opts.debugging_opts.relro_level.unwrap_or(sess.target.relro_level) {
1713 RelroLevel::Full => cmd.full_relro(),
1714 RelroLevel::Partial => cmd.partial_relro(),
1715 RelroLevel::Off => cmd.no_relro(),
1716 RelroLevel::None => {}
1720 /// Add library search paths used at runtime by dynamic linkers.
1722 cmd: &mut dyn Linker,
1724 codegen_results: &CodegenResults,
1725 out_filename: &Path,
1727 // FIXME (#2397): At some point we want to rpath our guesses as to
1728 // where extern libraries might live, based on the
1729 // add_lib_search_paths
1730 if sess.opts.cg.rpath {
1731 let libs = codegen_results
1735 .filter_map(|cnum| {
1736 codegen_results.crate_info.used_crate_source[cnum]
1739 .map(|(path, _)| &**path)
1741 .collect::<Vec<_>>();
1742 let mut rpath_config = RPathConfig {
1744 out_filename: out_filename.to_path_buf(),
1745 has_rpath: sess.target.has_rpath,
1746 is_like_osx: sess.target.is_like_osx,
1747 linker_is_gnu: sess.target.linker_is_gnu,
1749 cmd.args(&rpath::get_rpath_flags(&mut rpath_config));
1753 /// Produce the linker command line containing linker path and arguments.
1755 /// When comments in the function say "order-(in)dependent" they mean order-dependence between
1756 /// options and libraries/object files. For example `--whole-archive` (order-dependent) applies
1757 /// to specific libraries passed after it, and `-o` (output file, order-independent) applies
1758 /// to the linking process as a whole.
1759 /// Order-independent options may still override each other in order-dependent fashion,
1760 /// e.g `--foo=yes --foo=no` may be equivalent to `--foo=no`.
1761 fn linker_with_args<'a, B: ArchiveBuilder<'a>>(
1763 flavor: LinkerFlavor,
1765 crate_type: CrateType,
1767 out_filename: &Path,
1768 codegen_results: &CodegenResults,
1770 let crt_objects_fallback = crt_objects_fallback(sess, crate_type);
1771 let cmd = &mut *super::linker::get_linker(
1775 crt_objects_fallback,
1776 &codegen_results.crate_info.target_cpu,
1778 let link_output_kind = link_output_kind(sess, crate_type);
1780 // ------------ Early order-dependent options ------------
1782 // If we're building something like a dynamic library then some platforms
1783 // need to make sure that all symbols are exported correctly from the
1785 // Must be passed before any libraries to prevent the symbols to export from being thrown away,
1786 // at least on some platforms (e.g. windows-gnu).
1790 &codegen_results.crate_info.exported_symbols[&crate_type],
1793 // Can be used for adding custom CRT objects or overriding order-dependent options above.
1794 // FIXME: In practice built-in target specs use this for arbitrary order-independent options,
1795 // introduce a target spec option for order-independent linker options and migrate built-in
1797 add_pre_link_args(cmd, sess, flavor);
1799 // ------------ Object code and libraries, order-dependent ------------
1801 // Pre-link CRT objects.
1802 add_pre_link_objects(cmd, sess, link_output_kind, crt_objects_fallback);
1804 // Sanitizer libraries.
1805 add_sanitizer_libraries(sess, crate_type, cmd);
1807 // Object code from the current crate.
1808 // Take careful note of the ordering of the arguments we pass to the linker
1809 // here. Linkers will assume that things on the left depend on things to the
1810 // right. Things on the right cannot depend on things on the left. This is
1811 // all formally implemented in terms of resolving symbols (libs on the right
1812 // resolve unknown symbols of libs on the left, but not vice versa).
1814 // For this reason, we have organized the arguments we pass to the linker as
1817 // 1. The local object that LLVM just generated
1818 // 2. Local native libraries
1819 // 3. Upstream rust libraries
1820 // 4. Upstream native libraries
1822 // The rationale behind this ordering is that those items lower down in the
1823 // list can't depend on items higher up in the list. For example nothing can
1824 // depend on what we just generated (e.g., that'd be a circular dependency).
1825 // Upstream rust libraries are not supposed to depend on our local native
1826 // libraries as that would violate the structure of the DAG, in that
1827 // scenario they are required to link to them as well in a shared fashion.
1828 // (The current implementation still doesn't prevent it though, see the FIXME below.)
1830 // Note that upstream rust libraries may contain native dependencies as
1831 // well, but they also can't depend on what we just started to add to the
1832 // link line. And finally upstream native libraries can't depend on anything
1833 // in this DAG so far because they can only depend on other native libraries
1834 // and such dependencies are also required to be specified.
1835 add_local_crate_regular_objects(cmd, codegen_results);
1836 add_local_crate_metadata_objects(cmd, crate_type, codegen_results);
1837 add_local_crate_allocator_objects(cmd, codegen_results);
1839 // Avoid linking to dynamic libraries unless they satisfy some undefined symbols
1840 // at the point at which they are specified on the command line.
1841 // Must be passed before any (dynamic) libraries to have effect on them.
1842 // On Solaris-like systems, `-z ignore` acts as both `--as-needed` and `--gc-sections`
1843 // so it will ignore unreferenced ELF sections from relocatable objects.
1844 // For that reason, we put this flag after metadata objects as they would otherwise be removed.
1845 // FIXME: Support more fine-grained dead code removal on Solaris/illumos
1846 // and move this option back to the top.
1847 cmd.add_as_needed();
1849 // FIXME: Move this below to other native libraries
1850 // (or alternatively link all native libraries after their respective crates).
1851 // This change is somewhat breaking in practice due to local static libraries being linked
1852 // as whole-archive (#85144), so removing whole-archive may be a pre-requisite.
1853 if sess.opts.debugging_opts.link_native_libraries {
1854 add_local_native_libraries(cmd, sess, codegen_results);
1857 // Upstream rust libraries and their nobundle static libraries
1858 add_upstream_rust_crates::<B>(cmd, sess, codegen_results, crate_type, tmpdir);
1860 // Upstream dymamic native libraries linked with `#[link]` attributes at and `-l`
1861 // command line options.
1862 // If -Zlink-native-libraries=false is set, then the assumption is that an
1863 // external build system already has the native dependencies defined, and it
1864 // will provide them to the linker itself.
1865 if sess.opts.debugging_opts.link_native_libraries {
1866 add_upstream_native_libraries(cmd, sess, codegen_results);
1869 // Library linking above uses some global state for things like `-Bstatic`/`-Bdynamic` to make
1870 // command line shorter, reset it to default here before adding more libraries.
1871 cmd.reset_per_library_state();
1873 // FIXME: Built-in target specs occasionally use this for linking system libraries,
1874 // eliminate all such uses by migrating them to `#[link]` attributes in `lib(std,c,unwind)`
1875 // and remove the option.
1876 add_late_link_args(cmd, sess, flavor, crate_type, codegen_results);
1878 // ------------ Arbitrary order-independent options ------------
1880 // Add order-independent options determined by rustc from its compiler options,
1881 // target properties and source code.
1882 add_order_independent_options(
1886 crt_objects_fallback,
1894 // Can be used for arbitrary order-independent options.
1895 // In practice may also be occasionally used for linking native libraries.
1896 // Passed after compiler-generated options to support manual overriding when necessary.
1897 add_user_defined_link_args(cmd, sess);
1899 // ------------ Object code and libraries, order-dependent ------------
1901 // Post-link CRT objects.
1902 add_post_link_objects(cmd, sess, link_output_kind, crt_objects_fallback);
1904 // ------------ Late order-dependent options ------------
1906 // Doesn't really make sense.
1907 // FIXME: In practice built-in target specs use this for arbitrary order-independent options,
1908 // introduce a target spec option for order-independent linker options, migrate built-in specs
1909 // to it and remove the option.
1910 add_post_link_args(cmd, sess, flavor);
1915 fn add_order_independent_options(
1916 cmd: &mut dyn Linker,
1918 link_output_kind: LinkOutputKind,
1919 crt_objects_fallback: bool,
1920 flavor: LinkerFlavor,
1921 crate_type: CrateType,
1922 codegen_results: &CodegenResults,
1923 out_filename: &Path,
1926 add_gcc_ld_path(cmd, sess, flavor);
1928 add_apple_sdk(cmd, sess, flavor);
1930 add_link_script(cmd, sess, tmpdir, crate_type);
1932 if sess.target.is_like_fuchsia && crate_type == CrateType::Executable {
1933 let prefix = if sess.opts.debugging_opts.sanitizer.contains(SanitizerSet::ADDRESS) {
1938 cmd.arg(format!("--dynamic-linker={}ld.so.1", prefix));
1941 if sess.target.eh_frame_header {
1942 cmd.add_eh_frame_header();
1945 // Make the binary compatible with data execution prevention schemes.
1948 if crt_objects_fallback {
1949 cmd.no_crt_objects();
1952 if sess.target.is_like_emscripten {
1954 cmd.arg(if sess.panic_strategy() == PanicStrategy::Abort {
1955 "DISABLE_EXCEPTION_CATCHING=1"
1957 "DISABLE_EXCEPTION_CATCHING=0"
1961 if flavor == LinkerFlavor::PtxLinker {
1962 // Provide the linker with fallback to internal `target-cpu`.
1963 cmd.arg("--fallback-arch");
1964 cmd.arg(&codegen_results.crate_info.target_cpu);
1965 } else if flavor == LinkerFlavor::BpfLinker {
1967 cmd.arg(&codegen_results.crate_info.target_cpu);
1968 cmd.arg("--cpu-features");
1969 cmd.arg(match &sess.opts.cg.target_feature {
1970 feat if !feat.is_empty() => feat,
1971 _ => &sess.target.options.features,
1975 cmd.linker_plugin_lto();
1977 add_library_search_dirs(cmd, sess, crt_objects_fallback);
1979 cmd.output_filename(out_filename);
1981 if crate_type == CrateType::Executable && sess.target.is_like_windows {
1982 if let Some(ref s) = codegen_results.crate_info.windows_subsystem {
1987 // Try to strip as much out of the generated object by removing unused
1988 // sections if possible. See more comments in linker.rs
1989 if !sess.link_dead_code() {
1990 // If PGO is enabled sometimes gc_sections will remove the profile data section
1991 // as it appears to be unused. This can then cause the PGO profile file to lose
1992 // some functions. If we are generating a profile we shouldn't strip those metadata
1993 // sections to ensure we have all the data for PGO.
1995 crate_type == CrateType::Dylib || sess.opts.cg.profile_generate.enabled();
1996 cmd.gc_sections(keep_metadata);
1999 cmd.set_output_kind(link_output_kind, out_filename);
2001 add_relro_args(cmd, sess);
2003 // Pass optimization flags down to the linker.
2006 // Pass debuginfo and strip flags down to the linker.
2007 cmd.debuginfo(sess.opts.debugging_opts.strip);
2009 // We want to prevent the compiler from accidentally leaking in any system libraries,
2010 // so by default we tell linkers not to link to any default libraries.
2011 if !sess.opts.cg.default_linker_libraries && sess.target.no_default_libraries {
2012 cmd.no_default_libraries();
2015 if sess.opts.cg.profile_generate.enabled() || sess.instrument_coverage() {
2019 if sess.opts.cg.control_flow_guard != CFGuard::Disabled {
2020 cmd.control_flow_guard();
2023 add_rpath_args(cmd, sess, codegen_results, out_filename);
2026 /// # Native library linking
2028 /// User-supplied library search paths (-L on the command line). These are the same paths used to
2029 /// find Rust crates, so some of them may have been added already by the previous crate linking
2030 /// code. This only allows them to be found at compile time so it is still entirely up to outside
2031 /// forces to make sure that library can be found at runtime.
2033 /// Also note that the native libraries linked here are only the ones located in the current crate.
2034 /// Upstream crates with native library dependencies may have their native library pulled in above.
2035 fn add_local_native_libraries(
2036 cmd: &mut dyn Linker,
2038 codegen_results: &CodegenResults,
2040 let filesearch = sess.target_filesearch(PathKind::All);
2041 for search_path in filesearch.search_paths() {
2042 match search_path.kind {
2043 PathKind::Framework => {
2044 cmd.framework_path(&search_path.dir);
2047 cmd.include_path(&fix_windows_verbatim_for_gcc(&search_path.dir));
2053 codegen_results.crate_info.used_libraries.iter().filter(|l| relevant_lib(sess, l));
2055 let search_path = OnceCell::new();
2056 let mut last = (NativeLibKind::Unspecified, None);
2057 for lib in relevant_libs {
2058 let name = match lib.name {
2063 // Skip if this library is the same as the last.
2064 last = if (lib.kind, lib.name) == last { continue } else { (lib.kind, lib.name) };
2066 let verbatim = lib.verbatim.unwrap_or(false);
2068 NativeLibKind::Dylib { as_needed } => {
2069 cmd.link_dylib(name, verbatim, as_needed.unwrap_or(true))
2071 NativeLibKind::Unspecified => cmd.link_dylib(name, verbatim, true),
2072 NativeLibKind::Framework { as_needed } => {
2073 cmd.link_framework(name, as_needed.unwrap_or(true))
2075 NativeLibKind::Static { bundle: None | Some(true), .. }
2076 | NativeLibKind::Static { whole_archive: Some(true), .. } => {
2077 cmd.link_whole_staticlib(
2080 &search_path.get_or_init(|| archive_search_paths(sess)),
2083 NativeLibKind::Static { .. } => cmd.link_staticlib(name, verbatim),
2084 NativeLibKind::RawDylib => {
2085 // FIXME(#58713): Proper handling for raw dylibs.
2086 bug!("raw_dylib feature not yet implemented");
2092 /// # Linking Rust crates and their nobundle static libraries
2094 /// Rust crates are not considered at all when creating an rlib output. All dependencies will be
2095 /// linked when producing the final output (instead of the intermediate rlib version).
2096 fn add_upstream_rust_crates<'a, B: ArchiveBuilder<'a>>(
2097 cmd: &mut dyn Linker,
2099 codegen_results: &CodegenResults,
2100 crate_type: CrateType,
2103 // All of the heavy lifting has previously been accomplished by the
2104 // dependency_format module of the compiler. This is just crawling the
2105 // output of that module, adding crates as necessary.
2107 // Linking to a rlib involves just passing it to the linker (the linker
2108 // will slurp up the object files inside), and linking to a dynamic library
2109 // involves just passing the right -l flag.
2111 let (_, data) = codegen_results
2115 .find(|(ty, _)| *ty == crate_type)
2116 .expect("failed to find crate type in dependency format list");
2118 // Invoke get_used_crates to ensure that we get a topological sorting of
2120 let deps = &codegen_results.crate_info.used_crates;
2122 // There's a few internal crates in the standard library (aka libcore and
2123 // libstd) which actually have a circular dependence upon one another. This
2124 // currently arises through "weak lang items" where libcore requires things
2125 // like `rust_begin_unwind` but libstd ends up defining it. To get this
2126 // circular dependence to work correctly in all situations we'll need to be
2127 // sure to correctly apply the `--start-group` and `--end-group` options to
2128 // GNU linkers, otherwise if we don't use any other symbol from the standard
2129 // library it'll get discarded and the whole application won't link.
2131 // In this loop we're calculating the `group_end`, after which crate to
2132 // pass `--end-group` and `group_start`, before which crate to pass
2133 // `--start-group`. We currently do this by passing `--end-group` after
2134 // the first crate (when iterating backwards) that requires a lang item
2135 // defined somewhere else. Once that's set then when we've defined all the
2136 // necessary lang items we'll pass `--start-group`.
2138 // Note that this isn't amazing logic for now but it should do the trick
2139 // for the current implementation of the standard library.
2140 let mut group_end = None;
2141 let mut group_start = None;
2142 // Crates available for linking thus far.
2143 let mut available = FxHashSet::default();
2144 // Crates required to satisfy dependencies discovered so far.
2145 let mut required = FxHashSet::default();
2147 let info = &codegen_results.crate_info;
2148 for &cnum in deps.iter().rev() {
2149 if let Some(missing) = info.missing_lang_items.get(&cnum) {
2150 let missing_crates = missing.iter().map(|i| info.lang_item_to_crate.get(i).copied());
2151 required.extend(missing_crates);
2154 required.insert(Some(cnum));
2155 available.insert(Some(cnum));
2157 if required.len() > available.len() && group_end.is_none() {
2158 group_end = Some(cnum);
2160 if required.len() == available.len() && group_end.is_some() {
2161 group_start = Some(cnum);
2166 // If we didn't end up filling in all lang items from upstream crates then
2167 // we'll be filling it in with our crate. This probably means we're the
2168 // standard library itself, so skip this for now.
2169 if group_end.is_some() && group_start.is_none() {
2173 let mut compiler_builtins = None;
2174 let search_path = OnceCell::new();
2176 for &cnum in deps.iter() {
2177 if group_start == Some(cnum) {
2181 // We may not pass all crates through to the linker. Some crates may
2182 // appear statically in an existing dylib, meaning we'll pick up all the
2183 // symbols from the dylib.
2184 let src = &codegen_results.crate_info.used_crate_source[&cnum];
2185 match data[cnum.as_usize() - 1] {
2186 _ if codegen_results.crate_info.profiler_runtime == Some(cnum) => {
2187 add_static_crate::<B>(cmd, sess, codegen_results, tmpdir, crate_type, cnum);
2189 // compiler-builtins are always placed last to ensure that they're
2190 // linked correctly.
2191 _ if codegen_results.crate_info.compiler_builtins == Some(cnum) => {
2192 assert!(compiler_builtins.is_none());
2193 compiler_builtins = Some(cnum);
2195 Linkage::NotLinked | Linkage::IncludedFromDylib => {}
2196 Linkage::Static => {
2197 add_static_crate::<B>(cmd, sess, codegen_results, tmpdir, crate_type, cnum);
2199 // Link static native libs with "-bundle" modifier only if the crate they originate from
2200 // is being linked statically to the current crate. If it's linked dynamically
2201 // or is an rlib already included via some other dylib crate, the symbols from
2202 // native libs will have already been included in that dylib.
2204 // If -Zlink-native-libraries=false is set, then the assumption is that an
2205 // external build system already has the native dependencies defined, and it
2206 // will provide them to the linker itself.
2207 if sess.opts.debugging_opts.link_native_libraries {
2208 let mut last = None;
2209 for lib in &codegen_results.crate_info.native_libraries[&cnum] {
2210 if !relevant_lib(sess, lib) {
2211 // Skip libraries if they are disabled by `#[link(cfg=...)]`
2215 // Skip if this library is the same as the last.
2216 if last == lib.name {
2220 if let Some(static_lib_name) = lib.name {
2221 if let NativeLibKind::Static { bundle: Some(false), whole_archive } =
2224 let verbatim = lib.verbatim.unwrap_or(false);
2225 if whole_archive == Some(true) {
2226 cmd.link_whole_staticlib(
2229 search_path.get_or_init(|| archive_search_paths(sess)),
2232 cmd.link_staticlib(static_lib_name, verbatim);
2241 Linkage::Dynamic => add_dynamic_crate(cmd, sess, &src.dylib.as_ref().unwrap().0),
2244 if group_end == Some(cnum) {
2249 // compiler-builtins are always placed last to ensure that they're
2250 // linked correctly.
2251 // We must always link the `compiler_builtins` crate statically. Even if it
2252 // was already "included" in a dylib (e.g., `libstd` when `-C prefer-dynamic`
2254 if let Some(cnum) = compiler_builtins {
2255 add_static_crate::<B>(cmd, sess, codegen_results, tmpdir, crate_type, cnum);
2258 // Converts a library file-stem into a cc -l argument
2259 fn unlib<'a>(target: &Target, stem: &'a str) -> &'a str {
2260 if stem.starts_with("lib") && !target.is_like_windows { &stem[3..] } else { stem }
2263 // Adds the static "rlib" versions of all crates to the command line.
2264 // There's a bit of magic which happens here specifically related to LTO,
2265 // namely that we remove upstream object files.
2267 // When performing LTO, almost(*) all of the bytecode from the upstream
2268 // libraries has already been included in our object file output. As a
2269 // result we need to remove the object files in the upstream libraries so
2270 // the linker doesn't try to include them twice (or whine about duplicate
2271 // symbols). We must continue to include the rest of the rlib, however, as
2272 // it may contain static native libraries which must be linked in.
2274 // (*) Crates marked with `#![no_builtins]` don't participate in LTO and
2275 // their bytecode wasn't included. The object files in those libraries must
2276 // still be passed to the linker.
2278 // Note, however, that if we're not doing LTO we can just pass the rlib
2279 // blindly to the linker (fast) because it's fine if it's not actually
2280 // included as we're at the end of the dependency chain.
2281 fn add_static_crate<'a, B: ArchiveBuilder<'a>>(
2282 cmd: &mut dyn Linker,
2284 codegen_results: &CodegenResults,
2286 crate_type: CrateType,
2289 let src = &codegen_results.crate_info.used_crate_source[&cnum];
2290 let cratepath = &src.rlib.as_ref().unwrap().0;
2292 let mut link_upstream = |path: &Path| {
2293 // If we're creating a dylib, then we need to include the
2294 // whole of each object in our archive into that artifact. This is
2295 // because a `dylib` can be reused as an intermediate artifact.
2297 // Note, though, that we don't want to include the whole of a
2298 // compiler-builtins crate (e.g., compiler-rt) because it'll get
2299 // repeatedly linked anyway.
2300 let path = fix_windows_verbatim_for_gcc(path);
2301 if crate_type == CrateType::Dylib
2302 && codegen_results.crate_info.compiler_builtins != Some(cnum)
2304 cmd.link_whole_rlib(&path);
2306 cmd.link_rlib(&path);
2310 // See the comment above in `link_staticlib` and `link_rlib` for why if
2311 // there's a static library that's not relevant we skip all object
2313 let native_libs = &codegen_results.crate_info.native_libraries[&cnum];
2314 let skip_native = native_libs.iter().any(|lib| {
2315 matches!(lib.kind, NativeLibKind::Static { bundle: None | Some(true), .. })
2316 && !relevant_lib(sess, lib)
2319 if (!are_upstream_rust_objects_already_included(sess)
2320 || ignored_for_lto(sess, &codegen_results.crate_info, cnum))
2323 link_upstream(cratepath);
2327 let dst = tmpdir.join(cratepath.file_name().unwrap());
2328 let name = cratepath.file_name().unwrap().to_str().unwrap();
2329 let name = &name[3..name.len() - 5]; // chop off lib/.rlib
2331 sess.prof.generic_activity_with_arg("link_altering_rlib", name).run(|| {
2332 let mut archive = <B as ArchiveBuilder>::new(sess, &dst, Some(cratepath));
2333 archive.update_symbols();
2335 let mut any_objects = false;
2336 for f in archive.src_files() {
2337 if f == METADATA_FILENAME {
2338 archive.remove_file(&f);
2342 let canonical = f.replace("-", "_");
2343 let canonical_name = name.replace("-", "_");
2345 let is_rust_object =
2346 canonical.starts_with(&canonical_name) && looks_like_rust_object_file(&f);
2348 // If we've been requested to skip all native object files
2349 // (those not generated by the rust compiler) then we can skip
2350 // this file. See above for why we may want to do this.
2351 let skip_because_cfg_say_so = skip_native && !is_rust_object;
2353 // If we're performing LTO and this is a rust-generated object
2354 // file, then we don't need the object file as it's part of the
2355 // LTO module. Note that `#![no_builtins]` is excluded from LTO,
2356 // though, so we let that object file slide.
2357 let skip_because_lto = are_upstream_rust_objects_already_included(sess)
2359 && (sess.target.no_builtins
2360 || !codegen_results.crate_info.is_no_builtins.contains(&cnum));
2362 if skip_because_cfg_say_so || skip_because_lto {
2363 archive.remove_file(&f);
2373 link_upstream(&dst);
2377 // Same thing as above, but for dynamic crates instead of static crates.
2378 fn add_dynamic_crate(cmd: &mut dyn Linker, sess: &Session, cratepath: &Path) {
2379 // Just need to tell the linker about where the library lives and
2381 let parent = cratepath.parent();
2382 if let Some(dir) = parent {
2383 cmd.include_path(&fix_windows_verbatim_for_gcc(dir));
2385 let filestem = cratepath.file_stem().unwrap().to_str().unwrap();
2386 cmd.link_rust_dylib(
2387 Symbol::intern(&unlib(&sess.target, filestem)),
2388 parent.unwrap_or_else(|| Path::new("")),
2393 /// Link in all of our upstream crates' native dependencies. Remember that all of these upstream
2394 /// native dependencies are all non-static dependencies. We've got two cases then:
2396 /// 1. The upstream crate is an rlib. In this case we *must* link in the native dependency because
2397 /// the rlib is just an archive.
2399 /// 2. The upstream crate is a dylib. In order to use the dylib, we have to have the dependency
2400 /// present on the system somewhere. Thus, we don't gain a whole lot from not linking in the
2401 /// dynamic dependency to this crate as well.
2403 /// The use case for this is a little subtle. In theory the native dependencies of a crate are
2404 /// purely an implementation detail of the crate itself, but the problem arises with generic and
2405 /// inlined functions. If a generic function calls a native function, then the generic function
2406 /// must be instantiated in the target crate, meaning that the native symbol must also be resolved
2407 /// in the target crate.
2408 fn add_upstream_native_libraries(
2409 cmd: &mut dyn Linker,
2411 codegen_results: &CodegenResults,
2413 let mut last = (NativeLibKind::Unspecified, None);
2414 for &cnum in &codegen_results.crate_info.used_crates {
2415 for lib in codegen_results.crate_info.native_libraries[&cnum].iter() {
2416 let name = match lib.name {
2420 if !relevant_lib(sess, &lib) {
2424 // Skip if this library is the same as the last.
2425 last = if (lib.kind, lib.name) == last { continue } else { (lib.kind, lib.name) };
2427 let verbatim = lib.verbatim.unwrap_or(false);
2429 NativeLibKind::Dylib { as_needed } => {
2430 cmd.link_dylib(name, verbatim, as_needed.unwrap_or(true))
2432 NativeLibKind::Unspecified => cmd.link_dylib(name, verbatim, true),
2433 NativeLibKind::Framework { as_needed } => {
2434 cmd.link_framework(name, as_needed.unwrap_or(true))
2436 // ignore static native libraries here as we've
2437 // already included them in add_local_native_libraries and
2438 // add_upstream_rust_crates
2439 NativeLibKind::Static { .. } => {}
2440 NativeLibKind::RawDylib => {}
2446 fn relevant_lib(sess: &Session, lib: &NativeLib) -> bool {
2448 Some(ref cfg) => rustc_attr::cfg_matches(cfg, &sess.parse_sess, None),
2453 fn are_upstream_rust_objects_already_included(sess: &Session) -> bool {
2455 config::Lto::Fat => true,
2456 config::Lto::Thin => {
2457 // If we defer LTO to the linker, we haven't run LTO ourselves, so
2458 // any upstream object files have not been copied yet.
2459 !sess.opts.cg.linker_plugin_lto.enabled()
2461 config::Lto::No | config::Lto::ThinLocal => false,
2465 fn add_apple_sdk(cmd: &mut dyn Linker, sess: &Session, flavor: LinkerFlavor) {
2466 let arch = &sess.target.arch;
2467 let os = &sess.target.os;
2468 let llvm_target = &sess.target.llvm_target;
2469 if sess.target.vendor != "apple"
2470 || !matches!(os.as_str(), "ios" | "tvos")
2471 || flavor != LinkerFlavor::Gcc
2475 let sdk_name = match (arch.as_str(), os.as_str()) {
2476 ("aarch64", "tvos") => "appletvos",
2477 ("x86_64", "tvos") => "appletvsimulator",
2478 ("arm", "ios") => "iphoneos",
2479 ("aarch64", "ios") if llvm_target.contains("macabi") => "macosx",
2480 ("aarch64", "ios") if llvm_target.contains("sim") => "iphonesimulator",
2481 ("aarch64", "ios") => "iphoneos",
2482 ("x86", "ios") => "iphonesimulator",
2483 ("x86_64", "ios") if llvm_target.contains("macabi") => "macosx",
2484 ("x86_64", "ios") => "iphonesimulator",
2486 sess.err(&format!("unsupported arch `{}` for os `{}`", arch, os));
2490 let sdk_root = match get_apple_sdk_root(sdk_name) {
2497 if llvm_target.contains("macabi") {
2498 cmd.args(&["-target", llvm_target])
2500 let arch_name = llvm_target.split('-').next().expect("LLVM target must have a hyphen");
2501 cmd.args(&["-arch", arch_name])
2503 cmd.args(&["-isysroot", &sdk_root, "-Wl,-syslibroot", &sdk_root]);
2506 fn get_apple_sdk_root(sdk_name: &str) -> Result<String, String> {
2507 // Following what clang does
2508 // (https://github.com/llvm/llvm-project/blob/
2509 // 296a80102a9b72c3eda80558fb78a3ed8849b341/clang/lib/Driver/ToolChains/Darwin.cpp#L1661-L1678)
2510 // to allow the SDK path to be set. (For clang, xcrun sets
2511 // SDKROOT; for rustc, the user or build system can set it, or we
2512 // can fall back to checking for xcrun on PATH.)
2513 if let Ok(sdkroot) = env::var("SDKROOT") {
2514 let p = Path::new(&sdkroot);
2516 // Ignore `SDKROOT` if it's clearly set for the wrong platform.
2518 if sdkroot.contains("TVSimulator.platform")
2519 || sdkroot.contains("MacOSX.platform") => {}
2521 if sdkroot.contains("TVOS.platform") || sdkroot.contains("MacOSX.platform") => {}
2523 if sdkroot.contains("iPhoneSimulator.platform")
2524 || sdkroot.contains("MacOSX.platform") => {}
2526 if sdkroot.contains("iPhoneOS.platform") || sdkroot.contains("MacOSX.platform") => {
2529 if sdkroot.contains("iPhoneOS.platform")
2530 || sdkroot.contains("iPhoneSimulator.platform") => {}
2531 // Ignore `SDKROOT` if it's not a valid path.
2532 _ if !p.is_absolute() || p == Path::new("/") || !p.exists() => {}
2533 _ => return Ok(sdkroot),
2537 Command::new("xcrun").arg("--show-sdk-path").arg("-sdk").arg(sdk_name).output().and_then(
2539 if output.status.success() {
2540 Ok(String::from_utf8(output.stdout).unwrap())
2542 let error = String::from_utf8(output.stderr);
2543 let error = format!("process exit with error: {}", error.unwrap());
2544 Err(io::Error::new(io::ErrorKind::Other, &error[..]))
2550 Ok(output) => Ok(output.trim().to_string()),
2551 Err(e) => Err(format!("failed to get {} SDK path: {}", sdk_name, e)),
2555 fn add_gcc_ld_path(cmd: &mut dyn Linker, sess: &Session, flavor: LinkerFlavor) {
2556 if let Some(ld_impl) = sess.opts.debugging_opts.gcc_ld {
2557 if let LinkerFlavor::Gcc = flavor {
2560 if sess.target.lld_flavor == LldFlavor::Ld64 {
2561 let tools_path = sess.get_tools_search_paths(false);
2562 let ld64_exe = tools_path
2564 .map(|p| p.join("gcc-ld"))
2566 p.join(if sess.host.is_like_windows { "ld64.exe" } else { "ld64" })
2568 .find(|p| p.exists())
2569 .unwrap_or_else(|| sess.fatal("rust-lld (as ld64) not found"));
2571 let mut arg = OsString::from("-fuse-ld=");
2576 let tools_path = sess.get_tools_search_paths(false);
2577 let lld_path = tools_path
2579 .map(|p| p.join("gcc-ld"))
2581 p.join(if sess.host.is_like_windows { "ld.exe" } else { "ld" })
2584 .unwrap_or_else(|| sess.fatal("rust-lld (as ld) not found"));
2586 let mut arg = OsString::from("-B");
2594 sess.fatal("option `-Z gcc-ld` is used even though linker flavor is not gcc");