1 use rustc_data_structures::fx::{FxHashMap, FxHashSet};
2 use rustc_data_structures::temp_dir::MaybeTempDir;
3 use rustc_errors::Handler;
4 use rustc_fs_util::fix_windows_verbatim_for_gcc;
5 use rustc_hir::def_id::CrateNum;
6 use rustc_middle::middle::cstore::{DllImport, LibSource};
7 use rustc_middle::middle::dependency_format::Linkage;
8 use rustc_session::config::{self, CFGuard, CrateType, DebugInfo};
9 use rustc_session::config::{OutputFilenames, OutputType, PrintRequest};
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::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};
35 use tempfile::Builder as TempFileBuilder;
37 use std::cmp::Ordering;
38 use std::ffi::OsString;
39 use std::path::{Path, PathBuf};
40 use std::process::{ExitStatus, Output, Stdio};
41 use std::{ascii, char, env, fmt, fs, io, mem, str};
43 pub fn ensure_removed(diag_handler: &Handler, path: &Path) {
44 if let Err(e) = fs::remove_file(path) {
45 if e.kind() != io::ErrorKind::NotFound {
46 diag_handler.err(&format!("failed to remove {}: {}", path.display(), e));
51 /// Performs the linkage portion of the compilation phase. This will generate all
52 /// of the requested outputs for this compilation session.
53 pub fn link_binary<'a, B: ArchiveBuilder<'a>>(
55 codegen_results: &CodegenResults,
56 outputs: &OutputFilenames,
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(sess, crate_type, outputs, crate_name);
93 let _timer = sess.timer("link_rlib");
94 link_rlib::<B>(sess, codegen_results, RlibFlavor::Normal, &out_filename, &path)
97 CrateType::Staticlib => {
98 link_staticlib::<B>(sess, codegen_results, &out_filename, &path);
110 if sess.opts.json_artifact_notifications {
111 sess.parse_sess.span_diagnostic.emit_artifact_notification(&out_filename, "link");
116 // Remove the temporary object file and metadata if we aren't saving temps
117 sess.time("link_binary_remove_temps", || {
118 if !sess.opts.cg.save_temps {
119 let remove_temps_from_module = |module: &CompiledModule| {
120 if let Some(ref obj) = module.object {
121 ensure_removed(sess.diagnostic(), obj);
124 if let Some(ref obj) = module.dwarf_object {
125 ensure_removed(sess.diagnostic(), obj);
129 if sess.opts.output_types.should_link() && !preserve_objects_for_their_debuginfo(sess) {
130 for module in &codegen_results.modules {
131 remove_temps_from_module(module);
135 if let Some(ref metadata_module) = codegen_results.metadata_module {
136 remove_temps_from_module(metadata_module);
139 if let Some(ref allocator_module) = codegen_results.allocator_module {
140 remove_temps_from_module(allocator_module);
146 // The third parameter is for env vars, used on windows to set up the
147 // path for MSVC to find its DLLs, and gcc to find its bundled
152 flavor: LinkerFlavor,
153 self_contained: bool,
155 let msvc_tool = windows_registry::find_tool(&sess.opts.target_triple.triple(), "link.exe");
157 // If our linker looks like a batch script on Windows then to execute this
158 // we'll need to spawn `cmd` explicitly. This is primarily done to handle
159 // emscripten where the linker is `emcc.bat` and needs to be spawned as
160 // `cmd /c emcc.bat ...`.
162 // This worked historically but is needed manually since #42436 (regression
163 // was tagged as #42791) and some more info can be found on #44443 for
164 // emscripten itself.
165 let mut cmd = match linker.to_str() {
166 Some(linker) if cfg!(windows) && linker.ends_with(".bat") => Command::bat_script(linker),
168 LinkerFlavor::Lld(f) => Command::lld(linker, f),
169 LinkerFlavor::Msvc if sess.opts.cg.linker.is_none() && sess.target.linker.is_none() => {
170 Command::new(msvc_tool.as_ref().map_or(linker, |t| t.path()))
172 _ => Command::new(linker),
176 // UWP apps have API restrictions enforced during Store submissions.
177 // To comply with the Windows App Certification Kit,
178 // MSVC needs to link with the Store versions of the runtime libraries (vcruntime, msvcrt, etc).
179 let t = &sess.target;
180 if (flavor == LinkerFlavor::Msvc || flavor == LinkerFlavor::Lld(LldFlavor::Link))
183 if let Some(ref tool) = msvc_tool {
184 let original_path = tool.path();
185 if let Some(ref root_lib_path) = original_path.ancestors().nth(4) {
186 let arch = match t.arch.as_str() {
187 "x86_64" => Some("x64"),
188 "x86" => Some("x86"),
189 "aarch64" => Some("arm64"),
190 "arm" => Some("arm"),
193 if let Some(ref a) = arch {
194 // FIXME: Move this to `fn linker_with_args`.
195 let mut arg = OsString::from("/LIBPATH:");
196 arg.push(format!("{}\\lib\\{}\\store", root_lib_path.display(), a));
199 warn!("arch is not supported");
202 warn!("MSVC root path lib location not found");
205 warn!("link.exe not found");
209 // The compiler's sysroot often has some bundled tools, so add it to the
210 // PATH for the child.
211 let mut new_path = sess.host_filesearch(PathKind::All).get_tools_search_paths(self_contained);
212 let mut msvc_changed_path = false;
213 if sess.target.is_like_msvc {
214 if let Some(ref tool) = msvc_tool {
215 cmd.args(tool.args());
216 for &(ref k, ref v) in tool.env() {
218 new_path.extend(env::split_paths(v));
219 msvc_changed_path = true;
227 if !msvc_changed_path {
228 if let Some(path) = env::var_os("PATH") {
229 new_path.extend(env::split_paths(&path));
232 cmd.env("PATH", env::join_paths(new_path).unwrap());
237 pub fn each_linked_rlib(
239 f: &mut dyn FnMut(CrateNum, &Path),
240 ) -> Result<(), String> {
241 let crates = info.used_crates_static.iter();
243 for (ty, list) in info.dependency_formats.iter() {
245 CrateType::Executable
246 | CrateType::Staticlib
248 | CrateType::ProcMacro => {
255 let fmts = match fmts {
257 None => return Err("could not find formats for rlibs".to_string()),
259 for &(cnum, ref path) in crates {
260 match fmts.get(cnum.as_usize() - 1) {
261 Some(&Linkage::NotLinked | &Linkage::IncludedFromDylib) => continue,
263 None => return Err("could not find formats for rlibs".to_string()),
265 let name = &info.crate_name[&cnum];
266 let path = match *path {
267 LibSource::Some(ref p) => p,
268 LibSource::MetadataOnly => {
270 "could not find rlib for: `{}`, found rmeta (metadata) file",
274 LibSource::None => return Err(format!("could not find rlib for: `{}`", name)),
281 /// We use a temp directory here to avoid races between concurrent rustc processes,
282 /// such as builds in the same directory using the same filename for metadata while
283 /// building an `.rlib` (stomping over one another), or writing an `.rmeta` into a
284 /// directory being searched for `extern crate` (observing an incomplete file).
285 /// The returned path is the temporary file containing the complete metadata.
286 pub fn emit_metadata(sess: &Session, metadata: &[u8], tmpdir: &MaybeTempDir) -> PathBuf {
287 let out_filename = tmpdir.as_ref().join(METADATA_FILENAME);
288 let result = fs::write(&out_filename, metadata);
290 if let Err(e) = result {
291 sess.fatal(&format!("failed to write {}: {}", out_filename.display(), e));
297 /// Create an 'rlib'.
299 /// An rlib in its current incarnation is essentially a renamed .a file. The rlib primarily contains
300 /// the object file of the crate, but it also contains all of the object files from native
301 /// libraries. This is done by unzipping native libraries and inserting all of the contents into
303 fn link_rlib<'a, B: ArchiveBuilder<'a>>(
305 codegen_results: &CodegenResults,
308 tmpdir: &MaybeTempDir,
310 info!("preparing rlib to {:?}", out_filename);
311 let mut ab = <B as ArchiveBuilder>::new(sess, out_filename, None);
313 for obj in codegen_results.modules.iter().filter_map(|m| m.object.as_ref()) {
317 // Note that in this loop we are ignoring the value of `lib.cfg`. That is,
318 // we may not be configured to actually include a static library if we're
319 // adding it here. That's because later when we consume this rlib we'll
320 // decide whether we actually needed the static library or not.
322 // To do this "correctly" we'd need to keep track of which libraries added
323 // which object files to the archive. We don't do that here, however. The
324 // #[link(cfg(..))] feature is unstable, though, and only intended to get
325 // liblibc working. In that sense the check below just indicates that if
326 // there are any libraries we want to omit object files for at link time we
327 // just exclude all custom object files.
329 // Eventually if we want to stabilize or flesh out the #[link(cfg(..))]
330 // feature then we'll need to figure out how to record what objects were
331 // loaded from the libraries found here and then encode that into the
332 // metadata of the rlib we're generating somehow.
333 for lib in codegen_results.crate_info.used_libraries.iter() {
335 NativeLibKind::Static { bundle: None | Some(true), .. } => {}
336 NativeLibKind::Static { bundle: Some(false), .. }
337 | NativeLibKind::Dylib { .. }
338 | NativeLibKind::Framework { .. }
339 | NativeLibKind::RawDylib
340 | NativeLibKind::Unspecified => continue,
342 if let Some(name) = lib.name {
343 ab.add_native_library(name, lib.verbatim.unwrap_or(false));
347 for (raw_dylib_name, raw_dylib_imports) in
348 collate_raw_dylibs(&codegen_results.crate_info.used_libraries)
350 ab.inject_dll_import_lib(&raw_dylib_name, &raw_dylib_imports, tmpdir);
353 // After adding all files to the archive, we need to update the
354 // symbol table of the archive.
357 // Note that it is important that we add all of our non-object "magical
358 // files" *after* all of the object files in the archive. The reason for
359 // this is as follows:
361 // * When performing LTO, this archive will be modified to remove
362 // objects from above. The reason for this is described below.
364 // * When the system linker looks at an archive, it will attempt to
365 // determine the architecture of the archive in order to see whether its
368 // The algorithm for this detection is: iterate over the files in the
369 // archive. Skip magical SYMDEF names. Interpret the first file as an
370 // object file. Read architecture from the object file.
372 // * As one can probably see, if "metadata" and "foo.bc" were placed
373 // before all of the objects, then the architecture of this archive would
374 // not be correctly inferred once 'foo.o' is removed.
376 // Basically, all this means is that this code should not move above the
379 RlibFlavor::Normal => {
380 // metadata in rlib files is wrapped in a "dummy" object file for
381 // the target platform so the rlib can be processed entirely by
382 // normal linkers for the platform.
383 let metadata = create_metadata_file(sess, &codegen_results.metadata.raw_data);
384 ab.add_file(&emit_metadata(sess, &metadata, tmpdir));
386 // After adding all files to the archive, we need to update the
387 // symbol table of the archive. This currently dies on macOS (see
388 // #11162), and isn't necessary there anyway
389 if !sess.target.is_like_osx {
394 RlibFlavor::StaticlibBase => {
395 let obj = codegen_results.allocator_module.as_ref().and_then(|m| m.object.as_ref());
396 if let Some(obj) = obj {
403 // For rlibs we "pack" rustc metadata into a dummy object file. When rustc
404 // creates a dylib crate type it will pass `--whole-archive` (or the
405 // platform equivalent) to include all object files from an rlib into the
406 // final dylib itself. This causes linkers to iterate and try to include all
407 // files located in an archive, so if metadata is stored in an archive then
408 // it needs to be of a form that the linker will be able to process.
410 // Note, though, that we don't actually want this metadata to show up in any
411 // final output of the compiler. Instead this is purely for rustc's own
412 // metadata tracking purposes.
414 // With the above in mind, each "flavor" of object format gets special
415 // handling here depending on the target:
417 // * MachO - macos-like targets will insert the metadata into a section that
418 // is sort of fake dwarf debug info. Inspecting the source of the macos
419 // linker this causes these sections to be skipped automatically because
420 // it's not in an allowlist of otherwise well known dwarf section names to
421 // go into the final artifact.
423 // * WebAssembly - we actually don't have any container format for this
424 // target. WebAssembly doesn't support the `dylib` crate type anyway so
425 // there's no need for us to support this at this time. Consequently the
426 // metadata bytes are simply stored as-is into an rlib.
428 // * COFF - Windows-like targets create an object with a section that has
429 // the `IMAGE_SCN_LNK_REMOVE` flag set which ensures that if the linker
430 // ever sees the section it doesn't process it and it's removed.
432 // * ELF - All other targets are similar to Windows in that there's a
433 // `SHF_EXCLUDE` flag we can set on sections in an object file to get
434 // automatically removed from the final output.
436 // Note that this metdata format is kept in sync with
437 // `rustc_codegen_ssa/src/back/metadata.rs`.
438 fn create_metadata_file(sess: &Session, metadata: &[u8]) -> Vec<u8> {
439 let endianness = match sess.target.options.endian {
440 Endian::Little => Endianness::Little,
441 Endian::Big => Endianness::Big,
443 let architecture = match &sess.target.arch[..] {
444 "arm" => Architecture::Arm,
445 "aarch64" => Architecture::Aarch64,
446 "x86" => Architecture::I386,
447 "s390x" => Architecture::S390x,
448 "mips" => Architecture::Mips,
449 "mips64" => Architecture::Mips64,
451 if sess.target.pointer_width == 32 {
452 Architecture::X86_64_X32
457 "powerpc" => Architecture::PowerPc,
458 "powerpc64" => Architecture::PowerPc64,
459 "riscv32" => Architecture::Riscv32,
460 "riscv64" => Architecture::Riscv64,
461 "sparc64" => Architecture::Sparc64,
463 // This is used to handle all "other" targets. This includes targets
464 // in two categories:
466 // * Some targets don't have support in the `object` crate just yet
467 // to write an object file. These targets are likely to get filled
470 // * Targets like WebAssembly don't support dylibs, so the purpose
471 // of putting metadata in object files, to support linking rlibs
472 // into dylibs, is moot.
474 // In both of these cases it means that linking into dylibs will
475 // not be supported by rustc. This doesn't matter for targets like
476 // WebAssembly and for targets not supported by the `object` crate
477 // yet it means that work will need to be done in the `object` crate
478 // to add a case above.
479 _ => return metadata.to_vec(),
482 if sess.target.is_like_osx {
483 let mut file = Object::new(BinaryFormat::MachO, architecture, endianness);
486 file.add_section(b"__DWARF".to_vec(), b".rmeta".to_vec(), SectionKind::Debug);
487 file.append_section_data(section, metadata, 1);
488 file.write().unwrap()
489 } else if sess.target.is_like_windows {
490 const IMAGE_SCN_LNK_REMOVE: u32 = 0;
491 let mut file = Object::new(BinaryFormat::Coff, architecture, endianness);
493 let section = file.add_section(Vec::new(), b".rmeta".to_vec(), SectionKind::Debug);
494 file.section_mut(section).flags =
495 SectionFlags::Coff { characteristics: IMAGE_SCN_LNK_REMOVE };
496 file.append_section_data(section, metadata, 1);
497 file.write().unwrap()
499 const SHF_EXCLUDE: u64 = 0x80000000;
500 let mut file = Object::new(BinaryFormat::Elf, architecture, endianness);
502 match &sess.target.arch[..] {
503 // copied from `mipsel-linux-gnu-gcc foo.c -c` and
504 // inspecting the resulting `e_flags` field.
506 let e_flags = elf::EF_MIPS_ARCH_32R2 | elf::EF_MIPS_CPIC | elf::EF_MIPS_PIC;
507 file.flags = FileFlags::Elf { e_flags };
509 // copied from `mips64el-linux-gnuabi64-gcc foo.c -c`
511 let e_flags = elf::EF_MIPS_ARCH_64R2 | elf::EF_MIPS_CPIC | elf::EF_MIPS_PIC;
512 file.flags = FileFlags::Elf { e_flags };
515 // copied from `riscv64-linux-gnu-gcc foo.c -c`, note though
516 // that the `+d` target feature represents whether the double
517 // float abi is enabled.
518 "riscv64" if sess.target.options.features.contains("+d") => {
519 let e_flags = elf::EF_RISCV_RVC | elf::EF_RISCV_FLOAT_ABI_DOUBLE;
520 file.flags = FileFlags::Elf { e_flags };
526 let section = file.add_section(Vec::new(), b".rmeta".to_vec(), SectionKind::Debug);
527 file.section_mut(section).flags = SectionFlags::Elf { sh_flags: SHF_EXCLUDE };
528 file.append_section_data(section, metadata, 1);
529 file.write().unwrap()
534 /// Extract all symbols defined in raw-dylib libraries, collated by library name.
536 /// If we have multiple extern blocks that specify symbols defined in the same raw-dylib library,
537 /// then the CodegenResults value contains one NativeLib instance for each block. However, the
538 /// linker appears to expect only a single import library for each library used, so we need to
539 /// collate the symbols together by library name before generating the import libraries.
540 fn collate_raw_dylibs(used_libraries: &[NativeLib]) -> Vec<(String, Vec<DllImport>)> {
541 let mut dylib_table: FxHashMap<String, FxHashSet<Symbol>> = FxHashMap::default();
543 for lib in used_libraries {
544 if lib.kind == NativeLibKind::RawDylib {
545 let name = lib.name.unwrap_or_else(||
546 bug!("`link` attribute with kind = \"raw-dylib\" and no name should have caused error earlier")
548 let name = if matches!(lib.verbatim, Some(true)) {
551 format!("{}.dll", name)
556 .extend(lib.dll_imports.iter().map(|import| import.name));
560 // FIXME: when we add support for ordinals, fix this to propagate ordinals. Also figure out
561 // what we should do if we have two DllImport values with the same name but different
563 let mut result = dylib_table
565 .map(|(lib_name, imported_names)| {
566 let mut names = imported_names
568 .map(|name| DllImport { name: *name, ordinal: None })
569 .collect::<Vec<_>>();
570 names.sort_unstable_by(|a: &DllImport, b: &DllImport| {
571 match a.name.as_str().cmp(&b.name.as_str()) {
572 Ordering::Equal => a.ordinal.cmp(&b.ordinal),
578 .collect::<Vec<_>>();
579 result.sort_unstable_by(|a: &(String, Vec<DllImport>), b: &(String, Vec<DllImport>)| {
585 /// Create a static archive.
587 /// This is essentially the same thing as an rlib, but it also involves adding all of the upstream
588 /// crates' objects into the archive. This will slurp in all of the native libraries of upstream
589 /// dependencies as well.
591 /// Additionally, there's no way for us to link dynamic libraries, so we warn about all dynamic
592 /// library dependencies that they're not linked in.
594 /// There's no need to include metadata in a static archive, so ensure to not link in the metadata
595 /// object file (and also don't prepare the archive with a metadata file).
596 fn link_staticlib<'a, B: ArchiveBuilder<'a>>(
598 codegen_results: &CodegenResults,
600 tempdir: &MaybeTempDir,
603 link_rlib::<B>(sess, codegen_results, RlibFlavor::StaticlibBase, out_filename, tempdir);
604 let mut all_native_libs = vec![];
606 let res = each_linked_rlib(&codegen_results.crate_info, &mut |cnum, path| {
607 let name = &codegen_results.crate_info.crate_name[&cnum];
608 let native_libs = &codegen_results.crate_info.native_libraries[&cnum];
610 // Here when we include the rlib into our staticlib we need to make a
611 // decision whether to include the extra object files along the way.
612 // These extra object files come from statically included native
613 // libraries, but they may be cfg'd away with #[link(cfg(..))].
615 // This unstable feature, though, only needs liblibc to work. The only
616 // use case there is where musl is statically included in liblibc.rlib,
617 // so if we don't want the included version we just need to skip it. As
618 // a result the logic here is that if *any* linked library is cfg'd away
619 // we just skip all object files.
621 // Clearly this is not sufficient for a general purpose feature, and
622 // we'd want to read from the library's metadata to determine which
623 // object files come from where and selectively skip them.
624 let skip_object_files = native_libs.iter().any(|lib| {
625 matches!(lib.kind, NativeLibKind::Static { bundle: None | Some(true), .. })
626 && !relevant_lib(sess, lib)
631 are_upstream_rust_objects_already_included(sess)
632 && !ignored_for_lto(sess, &codegen_results.crate_info, cnum),
637 all_native_libs.extend(codegen_results.crate_info.native_libraries[&cnum].iter().cloned());
639 if let Err(e) = res {
646 if !all_native_libs.is_empty() {
647 if sess.opts.prints.contains(&PrintRequest::NativeStaticLibs) {
648 print_native_static_libs(sess, &all_native_libs);
653 fn escape_stdout_stderr_string(s: &[u8]) -> String {
654 str::from_utf8(s).map(|s| s.to_owned()).unwrap_or_else(|_| {
655 let mut x = "Non-UTF-8 output: ".to_string();
656 x.extend(s.iter().flat_map(|&b| ascii::escape_default(b)).map(char::from));
661 const LLVM_DWP_EXECUTABLE: &'static str = "rust-llvm-dwp";
663 /// Invoke `llvm-dwp` (shipped alongside rustc) to link `dwo` files from Split DWARF into a `dwp`
665 fn link_dwarf_object<'a>(sess: &'a Session, executable_out_filename: &Path) {
666 info!("preparing dwp to {}.dwp", executable_out_filename.to_str().unwrap());
668 let dwp_out_filename = executable_out_filename.with_extension("dwp");
669 let mut cmd = Command::new(LLVM_DWP_EXECUTABLE);
671 cmd.arg(executable_out_filename);
673 cmd.arg(&dwp_out_filename);
675 let mut new_path = sess.host_filesearch(PathKind::All).get_tools_search_paths(false);
676 if let Some(path) = env::var_os("PATH") {
677 new_path.extend(env::split_paths(&path));
679 let new_path = env::join_paths(new_path).unwrap();
680 cmd.env("PATH", new_path);
683 match sess.time("run_dwp", || cmd.output()) {
684 Ok(prog) if !prog.status.success() => {
685 sess.struct_err(&format!(
686 "linking dwarf objects with `{}` failed: {}",
687 LLVM_DWP_EXECUTABLE, prog.status
689 .note(&format!("{:?}", &cmd))
690 .note(&escape_stdout_stderr_string(&prog.stdout))
691 .note(&escape_stdout_stderr_string(&prog.stderr))
693 info!("linker stderr:\n{}", escape_stdout_stderr_string(&prog.stderr));
694 info!("linker stdout:\n{}", escape_stdout_stderr_string(&prog.stdout));
698 let dwp_not_found = e.kind() == io::ErrorKind::NotFound;
699 let mut err = if dwp_not_found {
700 sess.struct_err(&format!("linker `{}` not found", LLVM_DWP_EXECUTABLE))
702 sess.struct_err(&format!("could not exec the linker `{}`", LLVM_DWP_EXECUTABLE))
705 err.note(&e.to_string());
708 err.note(&format!("{:?}", &cmd));
716 /// Create a dynamic library or executable.
718 /// This will invoke the system linker/cc to create the resulting file. This links to all upstream
720 fn link_natively<'a, B: ArchiveBuilder<'a>>(
722 crate_type: CrateType,
724 codegen_results: &CodegenResults,
727 info!("preparing {:?} to {:?}", crate_type, out_filename);
728 let (linker_path, flavor) = linker_and_flavor(sess);
729 let mut cmd = linker_with_args::<B>(
739 linker::disable_localization(&mut cmd);
741 for &(ref k, ref v) in &sess.target.link_env {
744 for k in &sess.target.link_env_remove {
748 if sess.opts.debugging_opts.print_link_args {
749 println!("{:?}", &cmd);
752 // May have not found libraries in the right formats.
753 sess.abort_if_errors();
755 // Invoke the system linker
757 let retry_on_segfault = env::var("RUSTC_RETRY_LINKER_ON_SEGFAULT").is_ok();
762 prog = sess.time("run_linker", || exec_linker(sess, &cmd, out_filename, tmpdir));
763 let output = match prog {
764 Ok(ref output) => output,
767 if output.status.success() {
770 let mut out = output.stderr.clone();
771 out.extend(&output.stdout);
772 let out = String::from_utf8_lossy(&out);
774 // Check to see if the link failed with "unrecognized command line option:
775 // '-no-pie'" for gcc or "unknown argument: '-no-pie'" for clang. If so,
776 // reperform the link step without the -no-pie option. This is safe because
777 // if the linker doesn't support -no-pie then it should not default to
778 // linking executables as pie. Different versions of gcc seem to use
779 // different quotes in the error message so don't check for them.
780 if sess.target.linker_is_gnu
781 && flavor != LinkerFlavor::Ld
782 && (out.contains("unrecognized command line option")
783 || out.contains("unknown argument"))
784 && out.contains("-no-pie")
785 && cmd.get_args().iter().any(|e| e.to_string_lossy() == "-no-pie")
787 info!("linker output: {:?}", out);
788 warn!("Linker does not support -no-pie command line option. Retrying without.");
789 for arg in cmd.take_args() {
790 if arg.to_string_lossy() != "-no-pie" {
798 // Detect '-static-pie' used with an older version of gcc or clang not supporting it.
799 // Fallback from '-static-pie' to '-static' in that case.
800 if sess.target.linker_is_gnu
801 && flavor != LinkerFlavor::Ld
802 && (out.contains("unrecognized command line option")
803 || out.contains("unknown argument"))
804 && (out.contains("-static-pie") || out.contains("--no-dynamic-linker"))
805 && cmd.get_args().iter().any(|e| e.to_string_lossy() == "-static-pie")
807 info!("linker output: {:?}", out);
809 "Linker does not support -static-pie command line option. Retrying with -static instead."
811 // Mirror `add_(pre,post)_link_objects` to replace CRT objects.
812 let self_contained = crt_objects_fallback(sess, crate_type);
813 let opts = &sess.target;
814 let pre_objects = if self_contained {
815 &opts.pre_link_objects_fallback
817 &opts.pre_link_objects
819 let post_objects = if self_contained {
820 &opts.post_link_objects_fallback
822 &opts.post_link_objects
824 let get_objects = |objects: &CrtObjects, kind| {
830 .map(|obj| get_object_file_path(sess, obj, self_contained).into_os_string())
833 let pre_objects_static_pie = get_objects(pre_objects, LinkOutputKind::StaticPicExe);
834 let post_objects_static_pie = get_objects(post_objects, LinkOutputKind::StaticPicExe);
835 let mut pre_objects_static = get_objects(pre_objects, LinkOutputKind::StaticNoPicExe);
836 let mut post_objects_static = get_objects(post_objects, LinkOutputKind::StaticNoPicExe);
837 // Assume that we know insertion positions for the replacement arguments from replaced
838 // arguments, which is true for all supported targets.
839 assert!(pre_objects_static.is_empty() || !pre_objects_static_pie.is_empty());
840 assert!(post_objects_static.is_empty() || !post_objects_static_pie.is_empty());
841 for arg in cmd.take_args() {
842 if arg.to_string_lossy() == "-static-pie" {
843 // Replace the output kind.
845 } else if pre_objects_static_pie.contains(&arg) {
846 // Replace the pre-link objects (replace the first and remove the rest).
847 cmd.args(mem::take(&mut pre_objects_static));
848 } else if post_objects_static_pie.contains(&arg) {
849 // Replace the post-link objects (replace the first and remove the rest).
850 cmd.args(mem::take(&mut post_objects_static));
859 // Here's a terribly awful hack that really shouldn't be present in any
860 // compiler. Here an environment variable is supported to automatically
861 // retry the linker invocation if the linker looks like it segfaulted.
863 // Gee that seems odd, normally segfaults are things we want to know
864 // about! Unfortunately though in rust-lang/rust#38878 we're
865 // experiencing the linker segfaulting on Travis quite a bit which is
866 // causing quite a bit of pain to land PRs when they spuriously fail
867 // due to a segfault.
869 // The issue #38878 has some more debugging information on it as well,
870 // but this unfortunately looks like it's just a race condition in
871 // macOS's linker with some thread pool working in the background. It
872 // seems that no one currently knows a fix for this so in the meantime
873 // we're left with this...
874 if !retry_on_segfault || i > 3 {
877 let msg_segv = "clang: error: unable to execute command: Segmentation fault: 11";
878 let msg_bus = "clang: error: unable to execute command: Bus error: 10";
879 if out.contains(msg_segv) || out.contains(msg_bus) {
881 "looks like the linker segfaulted when we tried to call it, \
882 automatically retrying again. cmd = {:?}, out = {}.",
888 if is_illegal_instruction(&output.status) {
890 "looks like the linker hit an illegal instruction when we \
891 tried to call it, automatically retrying again. cmd = {:?}, ]\
892 out = {}, status = {}.",
893 cmd, out, output.status,
899 fn is_illegal_instruction(status: &ExitStatus) -> bool {
900 use std::os::unix::prelude::*;
901 status.signal() == Some(libc::SIGILL)
905 fn is_illegal_instruction(_status: &ExitStatus) -> bool {
910 fn escape_string(s: &[u8]) -> String {
911 str::from_utf8(s).map(|s| s.to_owned()).unwrap_or_else(|_| {
912 let mut x = "Non-UTF-8 output: ".to_string();
913 x.extend(s.iter().flat_map(|&b| ascii::escape_default(b)).map(char::from));
920 if !prog.status.success() {
921 let mut output = prog.stderr.clone();
922 output.extend_from_slice(&prog.stdout);
923 sess.struct_err(&format!(
924 "linking with `{}` failed: {}",
925 linker_path.display(),
928 .note(&format!("{:?}", &cmd))
929 .note(&escape_stdout_stderr_string(&output))
932 // If MSVC's `link.exe` was expected but the return code
933 // is not a Microsoft LNK error then suggest a way to fix or
934 // install the Visual Studio build tools.
935 if let Some(code) = prog.status.code() {
936 if sess.target.is_like_msvc
937 && flavor == LinkerFlavor::Msvc
938 // Respect the command line override
939 && sess.opts.cg.linker.is_none()
940 // Match exactly "link.exe"
941 && linker_path.to_str() == Some("link.exe")
942 // All Microsoft `link.exe` linking error codes are
943 // four digit numbers in the range 1000 to 9999 inclusive
944 && (code < 1000 || code > 9999)
946 let is_vs_installed = windows_registry::find_vs_version().is_ok();
947 let has_linker = windows_registry::find_tool(
948 &sess.opts.target_triple.triple(),
953 sess.note_without_error("`link.exe` returned an unexpected error");
954 if is_vs_installed && has_linker {
955 // the linker is broken
956 sess.note_without_error(
957 "the Visual Studio build tools may need to be repaired \
958 using the Visual Studio installer",
960 sess.note_without_error(
961 "or a necessary component may be missing from the \
962 \"C++ build tools\" workload",
964 } else if is_vs_installed {
965 // the linker is not installed
966 sess.note_without_error(
967 "in the Visual Studio installer, ensure the \
968 \"C++ build tools\" workload is selected",
971 // visual studio is not installed
972 sess.note_without_error(
973 "you may need to install Visual Studio build tools with the \
974 \"C++ build tools\" workload",
980 sess.abort_if_errors();
982 info!("linker stderr:\n{}", escape_stdout_stderr_string(&prog.stderr));
983 info!("linker stdout:\n{}", escape_stdout_stderr_string(&prog.stdout));
986 let linker_not_found = e.kind() == io::ErrorKind::NotFound;
988 let mut linker_error = {
989 if linker_not_found {
990 sess.struct_err(&format!("linker `{}` not found", linker_path.display()))
992 sess.struct_err(&format!(
993 "could not exec the linker `{}`",
994 linker_path.display()
999 linker_error.note(&e.to_string());
1001 if !linker_not_found {
1002 linker_error.note(&format!("{:?}", &cmd));
1005 linker_error.emit();
1007 if sess.target.is_like_msvc && linker_not_found {
1008 sess.note_without_error(
1009 "the msvc targets depend on the msvc linker \
1010 but `link.exe` was not found",
1012 sess.note_without_error(
1013 "please ensure that VS 2013, VS 2015, VS 2017 or VS 2019 \
1014 was installed with the Visual C++ option",
1017 sess.abort_if_errors();
1021 match sess.split_debuginfo() {
1022 // If split debug information is disabled or located in individual files
1023 // there's nothing to do here.
1024 SplitDebuginfo::Off | SplitDebuginfo::Unpacked => {}
1026 // If packed split-debuginfo is requested, but the final compilation
1027 // doesn't actually have any debug information, then we skip this step.
1028 SplitDebuginfo::Packed if sess.opts.debuginfo == DebugInfo::None => {}
1030 // On macOS the external `dsymutil` tool is used to create the packed
1031 // debug information. Note that this will read debug information from
1032 // the objects on the filesystem which we'll clean up later.
1033 SplitDebuginfo::Packed if sess.target.is_like_osx => {
1034 let prog = Command::new("dsymutil").arg(out_filename).output();
1037 if !prog.status.success() {
1038 let mut output = prog.stderr.clone();
1039 output.extend_from_slice(&prog.stdout);
1040 sess.struct_warn(&format!(
1041 "processing debug info with `dsymutil` failed: {}",
1044 .note(&escape_string(&output))
1048 Err(e) => sess.fatal(&format!("unable to run `dsymutil`: {}", e)),
1052 // On MSVC packed debug information is produced by the linker itself so
1053 // there's no need to do anything else here.
1054 SplitDebuginfo::Packed if sess.target.is_like_msvc => {}
1056 // ... and otherwise we're processing a `*.dwp` packed dwarf file.
1057 SplitDebuginfo::Packed => link_dwarf_object(sess, &out_filename),
1061 fn add_sanitizer_libraries(sess: &Session, crate_type: CrateType, linker: &mut dyn Linker) {
1062 // On macOS the runtimes are distributed as dylibs which should be linked to
1063 // both executables and dynamic shared objects. Everywhere else the runtimes
1064 // are currently distributed as static liraries which should be linked to
1065 // executables only.
1066 let needs_runtime = match crate_type {
1067 CrateType::Executable => true,
1068 CrateType::Dylib | CrateType::Cdylib | CrateType::ProcMacro => sess.target.is_like_osx,
1069 CrateType::Rlib | CrateType::Staticlib => false,
1076 let sanitizer = sess.opts.debugging_opts.sanitizer;
1077 if sanitizer.contains(SanitizerSet::ADDRESS) {
1078 link_sanitizer_runtime(sess, linker, "asan");
1080 if sanitizer.contains(SanitizerSet::LEAK) {
1081 link_sanitizer_runtime(sess, linker, "lsan");
1083 if sanitizer.contains(SanitizerSet::MEMORY) {
1084 link_sanitizer_runtime(sess, linker, "msan");
1086 if sanitizer.contains(SanitizerSet::THREAD) {
1087 link_sanitizer_runtime(sess, linker, "tsan");
1089 if sanitizer.contains(SanitizerSet::HWADDRESS) {
1090 link_sanitizer_runtime(sess, linker, "hwasan");
1094 fn link_sanitizer_runtime(sess: &Session, linker: &mut dyn Linker, name: &str) {
1095 fn find_sanitizer_runtime(sess: &Session, filename: &String) -> PathBuf {
1097 filesearch::make_target_lib_path(&sess.sysroot, sess.opts.target_triple.triple());
1098 let path = session_tlib.join(&filename);
1100 return session_tlib;
1102 let default_sysroot = filesearch::get_or_default_sysroot();
1103 let default_tlib = filesearch::make_target_lib_path(
1105 sess.opts.target_triple.triple(),
1107 return default_tlib;
1111 let channel = option_env!("CFG_RELEASE_CHANNEL")
1112 .map(|channel| format!("-{}", channel))
1113 .unwrap_or_default();
1115 if sess.target.is_like_osx {
1116 // On Apple platforms, the sanitizer is always built as a dylib, and
1117 // LLVM will link to `@rpath/*.dylib`, so we need to specify an
1118 // rpath to the library as well (the rpath should be absolute, see
1119 // PR #41352 for details).
1120 let filename = format!("rustc{}_rt.{}", channel, name);
1121 let path = find_sanitizer_runtime(&sess, &filename);
1122 let rpath = path.to_str().expect("non-utf8 component in path");
1123 linker.args(&["-Wl,-rpath", "-Xlinker", rpath]);
1124 linker.link_dylib(Symbol::intern(&filename), false, true);
1126 let filename = format!("librustc{}_rt.{}.a", channel, name);
1127 let path = find_sanitizer_runtime(&sess, &filename).join(&filename);
1128 linker.link_whole_rlib(&path);
1132 /// Returns a boolean indicating whether the specified crate should be ignored
1135 /// Crates ignored during LTO are not lumped together in the "massive object
1136 /// file" that we create and are linked in their normal rlib states. See
1137 /// comments below for what crates do not participate in LTO.
1139 /// It's unusual for a crate to not participate in LTO. Typically only
1140 /// compiler-specific and unstable crates have a reason to not participate in
1142 pub fn ignored_for_lto(sess: &Session, info: &CrateInfo, cnum: CrateNum) -> bool {
1143 // If our target enables builtin function lowering in LLVM then the
1144 // crates providing these functions don't participate in LTO (e.g.
1145 // no_builtins or compiler builtins crates).
1146 !sess.target.no_builtins
1147 && (info.compiler_builtins == Some(cnum) || info.is_no_builtins.contains(&cnum))
1150 fn linker_and_flavor(sess: &Session) -> (PathBuf, LinkerFlavor) {
1153 linker: Option<PathBuf>,
1154 flavor: Option<LinkerFlavor>,
1155 ) -> Option<(PathBuf, LinkerFlavor)> {
1156 match (linker, flavor) {
1157 (Some(linker), Some(flavor)) => Some((linker, flavor)),
1158 // only the linker flavor is known; use the default linker for the selected flavor
1159 (None, Some(flavor)) => Some((
1160 PathBuf::from(match flavor {
1161 LinkerFlavor::Em => {
1168 LinkerFlavor::Gcc => {
1169 if cfg!(any(target_os = "solaris", target_os = "illumos")) {
1170 // On historical Solaris systems, "cc" may have
1171 // been Sun Studio, which is not flag-compatible
1172 // with "gcc". This history casts a long shadow,
1173 // and many modern illumos distributions today
1174 // ship GCC as "gcc" without also making it
1175 // available as "cc".
1181 LinkerFlavor::Ld => "ld",
1182 LinkerFlavor::Msvc => "link.exe",
1183 LinkerFlavor::Lld(_) => "lld",
1184 LinkerFlavor::PtxLinker => "rust-ptx-linker",
1185 LinkerFlavor::BpfLinker => "bpf-linker",
1189 (Some(linker), None) => {
1190 let stem = linker.file_stem().and_then(|stem| stem.to_str()).unwrap_or_else(|| {
1191 sess.fatal("couldn't extract file stem from specified linker")
1194 let flavor = if stem == "emcc" {
1196 } else if stem == "gcc"
1197 || stem.ends_with("-gcc")
1199 || stem.ends_with("-clang")
1202 } else if stem == "wasm-ld" || stem.ends_with("-wasm-ld") {
1203 LinkerFlavor::Lld(LldFlavor::Wasm)
1204 } else if stem == "ld" || stem == "ld.lld" || stem.ends_with("-ld") {
1206 } else if stem == "link" || stem == "lld-link" {
1208 } else if stem == "lld" || stem == "rust-lld" {
1209 LinkerFlavor::Lld(sess.target.lld_flavor)
1211 // fall back to the value in the target spec
1212 sess.target.linker_flavor
1215 Some((linker, flavor))
1217 (None, None) => None,
1221 // linker and linker flavor specified via command line have precedence over what the target
1222 // specification specifies
1223 if let Some(ret) = infer_from(sess, sess.opts.cg.linker.clone(), sess.opts.cg.linker_flavor) {
1227 if let Some(ret) = infer_from(
1229 sess.target.linker.clone().map(PathBuf::from),
1230 Some(sess.target.linker_flavor),
1235 bug!("Not enough information provided to determine how to invoke the linker");
1238 /// Returns a boolean indicating whether we should preserve the object files on
1239 /// the filesystem for their debug information. This is often useful with
1240 /// split-dwarf like schemes.
1241 fn preserve_objects_for_their_debuginfo(sess: &Session) -> bool {
1242 // If the objects don't have debuginfo there's nothing to preserve.
1243 if sess.opts.debuginfo == config::DebugInfo::None {
1247 // If we're only producing artifacts that are archives, no need to preserve
1248 // the objects as they're losslessly contained inside the archives.
1250 sess.crate_types().iter().any(|&x| x != CrateType::Rlib && x != CrateType::Staticlib);
1255 // "unpacked" split debuginfo means that we leave object files as the
1256 // debuginfo is found in the original object files themselves
1257 sess.split_debuginfo() == SplitDebuginfo::Unpacked
1260 pub fn archive_search_paths(sess: &Session) -> Vec<PathBuf> {
1261 sess.target_filesearch(PathKind::Native).search_path_dirs()
1269 fn print_native_static_libs(sess: &Session, all_native_libs: &[NativeLib]) {
1270 let lib_args: Vec<_> = all_native_libs
1272 .filter(|l| relevant_lib(sess, l))
1274 let name = lib.name?;
1276 NativeLibKind::Static { bundle: Some(false), .. }
1277 | NativeLibKind::Dylib { .. }
1278 | NativeLibKind::Unspecified => {
1279 let verbatim = lib.verbatim.unwrap_or(false);
1280 if sess.target.is_like_msvc {
1281 Some(format!("{}{}", name, if verbatim { "" } else { ".lib" }))
1282 } else if sess.target.linker_is_gnu {
1283 Some(format!("-l{}{}", if verbatim { ":" } else { "" }, name))
1285 Some(format!("-l{}", name))
1288 NativeLibKind::Framework { .. } => {
1289 // ld-only syntax, since there are no frameworks in MSVC
1290 Some(format!("-framework {}", name))
1292 // These are included, no need to print them
1293 NativeLibKind::Static { bundle: None | Some(true), .. }
1294 | NativeLibKind::RawDylib => None,
1298 if !lib_args.is_empty() {
1299 sess.note_without_error(
1300 "Link against the following native artifacts when linking \
1301 against this static library. The order and any duplication \
1302 can be significant on some platforms.",
1304 // Prefix for greppability
1305 sess.note_without_error(&format!("native-static-libs: {}", &lib_args.join(" ")));
1309 fn get_object_file_path(sess: &Session, name: &str, self_contained: bool) -> PathBuf {
1310 let fs = sess.target_filesearch(PathKind::Native);
1311 let file_path = fs.get_lib_path().join(name);
1312 if file_path.exists() {
1315 // Special directory with objects used only in self-contained linkage mode
1317 let file_path = fs.get_self_contained_lib_path().join(name);
1318 if file_path.exists() {
1322 for search_path in fs.search_paths() {
1323 let file_path = search_path.dir.join(name);
1324 if file_path.exists() {
1334 out_filename: &Path,
1336 ) -> io::Result<Output> {
1337 // When attempting to spawn the linker we run a risk of blowing out the
1338 // size limits for spawning a new process with respect to the arguments
1339 // we pass on the command line.
1341 // Here we attempt to handle errors from the OS saying "your list of
1342 // arguments is too big" by reinvoking the linker again with an `@`-file
1343 // that contains all the arguments. The theory is that this is then
1344 // accepted on all linkers and the linker will read all its options out of
1345 // there instead of looking at the command line.
1346 if !cmd.very_likely_to_exceed_some_spawn_limit() {
1347 match cmd.command().stdout(Stdio::piped()).stderr(Stdio::piped()).spawn() {
1349 let output = child.wait_with_output();
1350 flush_linked_file(&output, out_filename)?;
1353 Err(ref e) if command_line_too_big(e) => {
1354 info!("command line to linker was too big: {}", e);
1356 Err(e) => return Err(e),
1360 info!("falling back to passing arguments to linker via an @-file");
1361 let mut cmd2 = cmd.clone();
1362 let mut args = String::new();
1363 for arg in cmd2.take_args() {
1365 &Escape { arg: arg.to_str().unwrap(), is_like_msvc: sess.target.is_like_msvc }
1370 let file = tmpdir.join("linker-arguments");
1371 let bytes = if sess.target.is_like_msvc {
1372 let mut out = Vec::with_capacity((1 + args.len()) * 2);
1373 // start the stream with a UTF-16 BOM
1374 for c in std::iter::once(0xFEFF).chain(args.encode_utf16()) {
1375 // encode in little endian
1377 out.push((c >> 8) as u8);
1383 fs::write(&file, &bytes)?;
1384 cmd2.arg(format!("@{}", file.display()));
1385 info!("invoking linker {:?}", cmd2);
1386 let output = cmd2.output();
1387 flush_linked_file(&output, out_filename)?;
1390 #[cfg(not(windows))]
1391 fn flush_linked_file(_: &io::Result<Output>, _: &Path) -> io::Result<()> {
1396 fn flush_linked_file(
1397 command_output: &io::Result<Output>,
1398 out_filename: &Path,
1399 ) -> io::Result<()> {
1400 // On Windows, under high I/O load, output buffers are sometimes not flushed,
1401 // even long after process exit, causing nasty, non-reproducible output bugs.
1403 // File::sync_all() calls FlushFileBuffers() down the line, which solves the problem.
1405 // А full writeup of the original Chrome bug can be found at
1406 // randomascii.wordpress.com/2018/02/25/compiler-bug-linker-bug-windows-kernel-bug/amp
1408 if let &Ok(ref out) = command_output {
1409 if out.status.success() {
1410 if let Ok(of) = fs::OpenOptions::new().write(true).open(out_filename) {
1420 fn command_line_too_big(err: &io::Error) -> bool {
1421 err.raw_os_error() == Some(::libc::E2BIG)
1425 fn command_line_too_big(err: &io::Error) -> bool {
1426 const ERROR_FILENAME_EXCED_RANGE: i32 = 206;
1427 err.raw_os_error() == Some(ERROR_FILENAME_EXCED_RANGE)
1430 #[cfg(not(any(unix, windows)))]
1431 fn command_line_too_big(_: &io::Error) -> bool {
1440 impl<'a> fmt::Display for Escape<'a> {
1441 fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
1442 if self.is_like_msvc {
1443 // This is "documented" at
1444 // https://docs.microsoft.com/en-us/cpp/build/reference/at-specify-a-linker-response-file
1446 // Unfortunately there's not a great specification of the
1447 // syntax I could find online (at least) but some local
1448 // testing showed that this seemed sufficient-ish to catch
1449 // at least a few edge cases.
1451 for c in self.arg.chars() {
1453 '"' => write!(f, "\\{}", c)?,
1454 c => write!(f, "{}", c)?,
1459 // This is documented at https://linux.die.net/man/1/ld, namely:
1461 // > Options in file are separated by whitespace. A whitespace
1462 // > character may be included in an option by surrounding the
1463 // > entire option in either single or double quotes. Any
1464 // > character (including a backslash) may be included by
1465 // > prefixing the character to be included with a backslash.
1467 // We put an argument on each line, so all we need to do is
1468 // ensure the line is interpreted as one whole argument.
1469 for c in self.arg.chars() {
1471 '\\' | ' ' => write!(f, "\\{}", c)?,
1472 c => write!(f, "{}", c)?,
1481 fn link_output_kind(sess: &Session, crate_type: CrateType) -> LinkOutputKind {
1482 let kind = match (crate_type, sess.crt_static(Some(crate_type)), sess.relocation_model()) {
1483 (CrateType::Executable, _, _) if sess.is_wasi_reactor() => LinkOutputKind::WasiReactorExe,
1484 (CrateType::Executable, false, RelocModel::Pic) => LinkOutputKind::DynamicPicExe,
1485 (CrateType::Executable, false, _) => LinkOutputKind::DynamicNoPicExe,
1486 (CrateType::Executable, true, RelocModel::Pic) => LinkOutputKind::StaticPicExe,
1487 (CrateType::Executable, true, _) => LinkOutputKind::StaticNoPicExe,
1488 (_, true, _) => LinkOutputKind::StaticDylib,
1489 (_, false, _) => LinkOutputKind::DynamicDylib,
1492 // Adjust the output kind to target capabilities.
1493 let opts = &sess.target;
1494 let pic_exe_supported = opts.position_independent_executables;
1495 let static_pic_exe_supported = opts.static_position_independent_executables;
1496 let static_dylib_supported = opts.crt_static_allows_dylibs;
1498 LinkOutputKind::DynamicPicExe if !pic_exe_supported => LinkOutputKind::DynamicNoPicExe,
1499 LinkOutputKind::StaticPicExe if !static_pic_exe_supported => LinkOutputKind::StaticNoPicExe,
1500 LinkOutputKind::StaticDylib if !static_dylib_supported => LinkOutputKind::DynamicDylib,
1505 // Returns true if linker is located within sysroot
1506 fn detect_self_contained_mingw(sess: &Session) -> bool {
1507 let (linker, _) = linker_and_flavor(&sess);
1508 // Assume `-C linker=rust-lld` as self-contained mode
1509 if linker == Path::new("rust-lld") {
1512 let linker_with_extension = if cfg!(windows) && linker.extension().is_none() {
1513 linker.with_extension("exe")
1517 for dir in env::split_paths(&env::var_os("PATH").unwrap_or_default()) {
1518 let full_path = dir.join(&linker_with_extension);
1519 // If linker comes from sysroot assume self-contained mode
1520 if full_path.is_file() && !full_path.starts_with(&sess.sysroot) {
1527 /// Whether we link to our own CRT objects instead of relying on gcc to pull them.
1528 /// We only provide such support for a very limited number of targets.
1529 fn crt_objects_fallback(sess: &Session, crate_type: CrateType) -> bool {
1530 if let Some(self_contained) = sess.opts.cg.link_self_contained {
1531 return self_contained;
1534 match sess.target.crt_objects_fallback {
1535 // FIXME: Find a better heuristic for "native musl toolchain is available",
1536 // based on host and linker path, for example.
1537 // (https://github.com/rust-lang/rust/pull/71769#issuecomment-626330237).
1538 Some(CrtObjectsFallback::Musl) => sess.crt_static(Some(crate_type)),
1539 Some(CrtObjectsFallback::Mingw) => {
1540 sess.host == sess.target
1541 && sess.target.vendor != "uwp"
1542 && detect_self_contained_mingw(&sess)
1544 // FIXME: Figure out cases in which WASM needs to link with a native toolchain.
1545 Some(CrtObjectsFallback::Wasm) => true,
1550 /// Add pre-link object files defined by the target spec.
1551 fn add_pre_link_objects(
1552 cmd: &mut dyn Linker,
1554 link_output_kind: LinkOutputKind,
1555 self_contained: bool,
1557 let opts = &sess.target;
1559 if self_contained { &opts.pre_link_objects_fallback } else { &opts.pre_link_objects };
1560 for obj in objects.get(&link_output_kind).iter().copied().flatten() {
1561 cmd.add_object(&get_object_file_path(sess, obj, self_contained));
1565 /// Add post-link object files defined by the target spec.
1566 fn add_post_link_objects(
1567 cmd: &mut dyn Linker,
1569 link_output_kind: LinkOutputKind,
1570 self_contained: bool,
1572 let opts = &sess.target;
1574 if self_contained { &opts.post_link_objects_fallback } else { &opts.post_link_objects };
1575 for obj in objects.get(&link_output_kind).iter().copied().flatten() {
1576 cmd.add_object(&get_object_file_path(sess, obj, self_contained));
1580 /// Add arbitrary "pre-link" args defined by the target spec or from command line.
1581 /// FIXME: Determine where exactly these args need to be inserted.
1582 fn add_pre_link_args(cmd: &mut dyn Linker, sess: &Session, flavor: LinkerFlavor) {
1583 if let Some(args) = sess.target.pre_link_args.get(&flavor) {
1586 cmd.args(&sess.opts.debugging_opts.pre_link_args);
1589 /// Add a link script embedded in the target, if applicable.
1590 fn add_link_script(cmd: &mut dyn Linker, sess: &Session, tmpdir: &Path, crate_type: CrateType) {
1591 match (crate_type, &sess.target.link_script) {
1592 (CrateType::Cdylib | CrateType::Executable, Some(script)) => {
1593 if !sess.target.linker_is_gnu {
1594 sess.fatal("can only use link script when linking with GNU-like linker");
1597 let file_name = ["rustc", &sess.target.llvm_target, "linkfile.ld"].join("-");
1599 let path = tmpdir.join(file_name);
1600 if let Err(e) = fs::write(&path, script) {
1601 sess.fatal(&format!("failed to write link script to {}: {}", path.display(), e));
1604 cmd.arg("--script");
1611 /// Add arbitrary "user defined" args defined from command line.
1612 /// FIXME: Determine where exactly these args need to be inserted.
1613 fn add_user_defined_link_args(cmd: &mut dyn Linker, sess: &Session) {
1614 cmd.args(&sess.opts.cg.link_args);
1617 /// Add arbitrary "late link" args defined by the target spec.
1618 /// FIXME: Determine where exactly these args need to be inserted.
1619 fn add_late_link_args(
1620 cmd: &mut dyn Linker,
1622 flavor: LinkerFlavor,
1623 crate_type: CrateType,
1624 codegen_results: &CodegenResults,
1626 let any_dynamic_crate = crate_type == CrateType::Dylib
1627 || codegen_results.crate_info.dependency_formats.iter().any(|(ty, list)| {
1628 *ty == crate_type && list.iter().any(|&linkage| linkage == Linkage::Dynamic)
1630 if any_dynamic_crate {
1631 if let Some(args) = sess.target.late_link_args_dynamic.get(&flavor) {
1635 if let Some(args) = sess.target.late_link_args_static.get(&flavor) {
1639 if let Some(args) = sess.target.late_link_args.get(&flavor) {
1644 /// Add arbitrary "post-link" args defined by the target spec.
1645 /// FIXME: Determine where exactly these args need to be inserted.
1646 fn add_post_link_args(cmd: &mut dyn Linker, sess: &Session, flavor: LinkerFlavor) {
1647 if let Some(args) = sess.target.post_link_args.get(&flavor) {
1652 /// Add object files containing code from the current crate.
1653 fn add_local_crate_regular_objects(cmd: &mut dyn Linker, codegen_results: &CodegenResults) {
1654 for obj in codegen_results.modules.iter().filter_map(|m| m.object.as_ref()) {
1655 cmd.add_object(obj);
1659 /// Add object files for allocator code linked once for the whole crate tree.
1660 fn add_local_crate_allocator_objects(cmd: &mut dyn Linker, codegen_results: &CodegenResults) {
1661 if let Some(obj) = codegen_results.allocator_module.as_ref().and_then(|m| m.object.as_ref()) {
1662 cmd.add_object(obj);
1666 /// Add object files containing metadata for the current crate.
1667 fn add_local_crate_metadata_objects(
1668 cmd: &mut dyn Linker,
1669 crate_type: CrateType,
1670 codegen_results: &CodegenResults,
1672 // When linking a dynamic library, we put the metadata into a section of the
1673 // executable. This metadata is in a separate object file from the main
1674 // object file, so we link that in here.
1675 if crate_type == CrateType::Dylib || crate_type == CrateType::ProcMacro {
1676 if let Some(obj) = codegen_results.metadata_module.as_ref().and_then(|m| m.object.as_ref())
1678 cmd.add_object(obj);
1683 /// Add sysroot and other globally set directories to the directory search list.
1684 fn add_library_search_dirs(cmd: &mut dyn Linker, sess: &Session, self_contained: bool) {
1685 // The default library location, we need this to find the runtime.
1686 // The location of crates will be determined as needed.
1687 let lib_path = sess.target_filesearch(PathKind::All).get_lib_path();
1688 cmd.include_path(&fix_windows_verbatim_for_gcc(&lib_path));
1690 // Special directory with libraries used only in self-contained linkage mode
1692 let lib_path = sess.target_filesearch(PathKind::All).get_self_contained_lib_path();
1693 cmd.include_path(&fix_windows_verbatim_for_gcc(&lib_path));
1697 /// Add options making relocation sections in the produced ELF files read-only
1698 /// and suppressing lazy binding.
1699 fn add_relro_args(cmd: &mut dyn Linker, sess: &Session) {
1700 match sess.opts.debugging_opts.relro_level.unwrap_or(sess.target.relro_level) {
1701 RelroLevel::Full => cmd.full_relro(),
1702 RelroLevel::Partial => cmd.partial_relro(),
1703 RelroLevel::Off => cmd.no_relro(),
1704 RelroLevel::None => {}
1708 /// Add library search paths used at runtime by dynamic linkers.
1710 cmd: &mut dyn Linker,
1712 codegen_results: &CodegenResults,
1713 out_filename: &Path,
1715 // FIXME (#2397): At some point we want to rpath our guesses as to
1716 // where extern libraries might live, based on the
1717 // addl_lib_search_paths
1718 if sess.opts.cg.rpath {
1719 let target_triple = sess.opts.target_triple.triple();
1720 let mut get_install_prefix_lib_path = || {
1721 let install_prefix = option_env!("CFG_PREFIX").expect("CFG_PREFIX");
1722 let tlib = rustc_target::target_rustlib_path(&sess.sysroot, target_triple).join("lib");
1723 let mut path = PathBuf::from(install_prefix);
1728 let mut rpath_config = RPathConfig {
1729 used_crates: &codegen_results.crate_info.used_crates_dynamic,
1730 out_filename: out_filename.to_path_buf(),
1731 has_rpath: sess.target.has_rpath,
1732 is_like_osx: sess.target.is_like_osx,
1733 linker_is_gnu: sess.target.linker_is_gnu,
1734 get_install_prefix_lib_path: &mut get_install_prefix_lib_path,
1736 cmd.args(&rpath::get_rpath_flags(&mut rpath_config));
1740 /// Produce the linker command line containing linker path and arguments.
1742 /// When comments in the function say "order-(in)dependent" they mean order-dependence between
1743 /// options and libraries/object files. For example `--whole-archive` (order-dependent) applies
1744 /// to specific libraries passed after it, and `-o` (output file, order-independent) applies
1745 /// to the linking process as a whole.
1746 /// Order-independent options may still override each other in order-dependent fashion,
1747 /// e.g `--foo=yes --foo=no` may be equivalent to `--foo=no`.
1748 fn linker_with_args<'a, B: ArchiveBuilder<'a>>(
1750 flavor: LinkerFlavor,
1752 crate_type: CrateType,
1754 out_filename: &Path,
1755 codegen_results: &CodegenResults,
1757 let crt_objects_fallback = crt_objects_fallback(sess, crate_type);
1758 let base_cmd = get_linker(sess, path, flavor, crt_objects_fallback);
1759 // FIXME: Move `/LIBPATH` addition for uwp targets from the linker construction
1760 // to the linker args construction.
1761 assert!(base_cmd.get_args().is_empty() || sess.target.vendor == "uwp");
1762 let cmd = &mut *codegen_results.linker_info.to_linker(base_cmd, &sess, flavor);
1763 let link_output_kind = link_output_kind(sess, crate_type);
1765 // ------------ Early order-dependent options ------------
1767 // Avoid linking to dynamic libraries unless they satisfy some undefined symbols
1768 // at the point at which they are specified on the command line.
1769 // Must be passed before any (dynamic) libraries to have effect on them.
1770 cmd.add_as_needed();
1772 // If we're building something like a dynamic library then some platforms
1773 // need to make sure that all symbols are exported correctly from the
1775 // Must be passed before any libraries to prevent the symbols to export from being thrown away,
1776 // at least on some platforms (e.g. windows-gnu).
1777 cmd.export_symbols(tmpdir, crate_type);
1779 // Can be used for adding custom CRT objects or overriding order-dependent options above.
1780 // FIXME: In practice built-in target specs use this for arbitrary order-independent options,
1781 // introduce a target spec option for order-independent linker options and migrate built-in
1783 add_pre_link_args(cmd, sess, flavor);
1785 // ------------ Object code and libraries, order-dependent ------------
1787 // Pre-link CRT objects.
1788 add_pre_link_objects(cmd, sess, link_output_kind, crt_objects_fallback);
1790 // Sanitizer libraries.
1791 add_sanitizer_libraries(sess, crate_type, cmd);
1793 // Object code from the current crate.
1794 // Take careful note of the ordering of the arguments we pass to the linker
1795 // here. Linkers will assume that things on the left depend on things to the
1796 // right. Things on the right cannot depend on things on the left. This is
1797 // all formally implemented in terms of resolving symbols (libs on the right
1798 // resolve unknown symbols of libs on the left, but not vice versa).
1800 // For this reason, we have organized the arguments we pass to the linker as
1803 // 1. The local object that LLVM just generated
1804 // 2. Local native libraries
1805 // 3. Upstream rust libraries
1806 // 4. Upstream native libraries
1808 // The rationale behind this ordering is that those items lower down in the
1809 // list can't depend on items higher up in the list. For example nothing can
1810 // depend on what we just generated (e.g., that'd be a circular dependency).
1811 // Upstream rust libraries are not supposed to depend on our local native
1812 // libraries as that would violate the structure of the DAG, in that
1813 // scenario they are required to link to them as well in a shared fashion.
1814 // (The current implementation still doesn't prevent it though, see the FIXME below.)
1816 // Note that upstream rust libraries may contain native dependencies as
1817 // well, but they also can't depend on what we just started to add to the
1818 // link line. And finally upstream native libraries can't depend on anything
1819 // in this DAG so far because they can only depend on other native libraries
1820 // and such dependencies are also required to be specified.
1821 add_local_crate_regular_objects(cmd, codegen_results);
1822 add_local_crate_metadata_objects(cmd, crate_type, codegen_results);
1823 add_local_crate_allocator_objects(cmd, codegen_results);
1825 // FIXME: Move this below to other native libraries
1826 // (or alternatively link all native libraries after their respective crates).
1827 // This change is somewhat breaking in practice due to local static libraries being linked
1828 // as whole-archive (#85144), so removing whole-archive may be a pre-requisite.
1829 if sess.opts.debugging_opts.link_native_libraries {
1830 add_local_native_libraries(cmd, sess, codegen_results);
1834 add_upstream_rust_crates::<B>(cmd, sess, codegen_results, crate_type, tmpdir);
1836 // Native libraries linked with `#[link]` attributes at and `-l` command line options.
1837 // If -Zlink-native-libraries=false is set, then the assumption is that an
1838 // external build system already has the native dependencies defined, and it
1839 // will provide them to the linker itself.
1840 if sess.opts.debugging_opts.link_native_libraries {
1841 add_upstream_native_libraries(cmd, sess, codegen_results, crate_type);
1844 // Library linking above uses some global state for things like `-Bstatic`/`-Bdynamic` to make
1845 // command line shorter, reset it to default here before adding more libraries.
1846 cmd.reset_per_library_state();
1848 // FIXME: Built-in target specs occasionally use this for linking system libraries,
1849 // eliminate all such uses by migrating them to `#[link]` attributes in `lib(std,c,unwind)`
1850 // and remove the option.
1851 add_late_link_args(cmd, sess, flavor, crate_type, codegen_results);
1853 // ------------ Arbitrary order-independent options ------------
1855 // Add order-independent options determined by rustc from its compiler options,
1856 // target properties and source code.
1857 add_order_independent_options(
1861 crt_objects_fallback,
1869 // Can be used for arbitrary order-independent options.
1870 // In practice may also be occasionally used for linking native libraries.
1871 // Passed after compiler-generated options to support manual overriding when necessary.
1872 add_user_defined_link_args(cmd, sess);
1874 // ------------ Object code and libraries, order-dependent ------------
1876 // Post-link CRT objects.
1877 add_post_link_objects(cmd, sess, link_output_kind, crt_objects_fallback);
1879 // ------------ Late order-dependent options ------------
1881 // Doesn't really make sense.
1882 // FIXME: In practice built-in target specs use this for arbitrary order-independent options,
1883 // introduce a target spec option for order-independent linker options, migrate built-in specs
1884 // to it and remove the option.
1885 add_post_link_args(cmd, sess, flavor);
1890 fn add_order_independent_options(
1891 cmd: &mut dyn Linker,
1893 link_output_kind: LinkOutputKind,
1894 crt_objects_fallback: bool,
1895 flavor: LinkerFlavor,
1896 crate_type: CrateType,
1897 codegen_results: &CodegenResults,
1898 out_filename: &Path,
1901 add_apple_sdk(cmd, sess, flavor);
1903 add_link_script(cmd, sess, tmpdir, crate_type);
1905 if sess.target.is_like_fuchsia && crate_type == CrateType::Executable {
1906 let prefix = if sess.opts.debugging_opts.sanitizer.contains(SanitizerSet::ADDRESS) {
1911 cmd.arg(format!("--dynamic-linker={}ld.so.1", prefix));
1914 if sess.target.eh_frame_header {
1915 cmd.add_eh_frame_header();
1918 // Make the binary compatible with data execution prevention schemes.
1921 if crt_objects_fallback {
1922 cmd.no_crt_objects();
1925 if sess.target.is_like_emscripten {
1927 cmd.arg(if sess.panic_strategy() == PanicStrategy::Abort {
1928 "DISABLE_EXCEPTION_CATCHING=1"
1930 "DISABLE_EXCEPTION_CATCHING=0"
1934 if flavor == LinkerFlavor::PtxLinker {
1935 // Provide the linker with fallback to internal `target-cpu`.
1936 cmd.arg("--fallback-arch");
1937 cmd.arg(&codegen_results.linker_info.target_cpu);
1938 } else if flavor == LinkerFlavor::BpfLinker {
1940 cmd.arg(&codegen_results.linker_info.target_cpu);
1941 cmd.arg("--cpu-features");
1942 cmd.arg(match &sess.opts.cg.target_feature {
1943 feat if !feat.is_empty() => feat,
1944 _ => &sess.target.options.features,
1948 cmd.linker_plugin_lto();
1950 add_library_search_dirs(cmd, sess, crt_objects_fallback);
1952 cmd.output_filename(out_filename);
1954 if crate_type == CrateType::Executable && sess.target.is_like_windows {
1955 if let Some(ref s) = codegen_results.windows_subsystem {
1960 // Try to strip as much out of the generated object by removing unused
1961 // sections if possible. See more comments in linker.rs
1962 if !sess.link_dead_code() {
1963 let keep_metadata = crate_type == CrateType::Dylib;
1964 cmd.gc_sections(keep_metadata);
1967 cmd.set_output_kind(link_output_kind, out_filename);
1969 add_relro_args(cmd, sess);
1971 // Pass optimization flags down to the linker.
1974 // Pass debuginfo and strip flags down to the linker.
1975 cmd.debuginfo(sess.opts.debugging_opts.strip);
1977 // We want to prevent the compiler from accidentally leaking in any system libraries,
1978 // so by default we tell linkers not to link to any default libraries.
1979 if !sess.opts.cg.default_linker_libraries && sess.target.no_default_libraries {
1980 cmd.no_default_libraries();
1983 if sess.opts.cg.profile_generate.enabled() || sess.instrument_coverage() {
1987 if sess.opts.cg.control_flow_guard != CFGuard::Disabled {
1988 cmd.control_flow_guard();
1991 add_rpath_args(cmd, sess, codegen_results, out_filename);
1994 /// # Native library linking
1996 /// User-supplied library search paths (-L on the command line). These are the same paths used to
1997 /// find Rust crates, so some of them may have been added already by the previous crate linking
1998 /// code. This only allows them to be found at compile time so it is still entirely up to outside
1999 /// forces to make sure that library can be found at runtime.
2001 /// Also note that the native libraries linked here are only the ones located in the current crate.
2002 /// Upstream crates with native library dependencies may have their native library pulled in above.
2003 fn add_local_native_libraries(
2004 cmd: &mut dyn Linker,
2006 codegen_results: &CodegenResults,
2008 let filesearch = sess.target_filesearch(PathKind::All);
2009 for search_path in filesearch.search_paths() {
2010 match search_path.kind {
2011 PathKind::Framework => {
2012 cmd.framework_path(&search_path.dir);
2015 cmd.include_path(&fix_windows_verbatim_for_gcc(&search_path.dir));
2021 codegen_results.crate_info.used_libraries.iter().filter(|l| relevant_lib(sess, l));
2023 let search_path = archive_search_paths(sess);
2024 let mut last = (NativeLibKind::Unspecified, None);
2025 for lib in relevant_libs {
2026 let name = match lib.name {
2031 // Skip if this library is the same as the last.
2032 last = if (lib.kind, lib.name) == last { continue } else { (lib.kind, lib.name) };
2034 let verbatim = lib.verbatim.unwrap_or(false);
2036 NativeLibKind::Dylib { as_needed } => {
2037 cmd.link_dylib(name, verbatim, as_needed.unwrap_or(true))
2039 NativeLibKind::Unspecified => cmd.link_dylib(name, verbatim, true),
2040 NativeLibKind::Framework { as_needed } => {
2041 cmd.link_framework(name, as_needed.unwrap_or(true))
2043 NativeLibKind::Static { bundle: None | Some(true), .. }
2044 | NativeLibKind::Static { whole_archive: Some(true), .. } => {
2045 cmd.link_whole_staticlib(name, verbatim, &search_path);
2047 NativeLibKind::Static { .. } => cmd.link_staticlib(name, verbatim),
2048 NativeLibKind::RawDylib => {
2049 // FIXME(#58713): Proper handling for raw dylibs.
2050 bug!("raw_dylib feature not yet implemented");
2056 /// # Rust Crate linking
2058 /// Rust crates are not considered at all when creating an rlib output. All dependencies will be
2059 /// linked when producing the final output (instead of the intermediate rlib version).
2060 fn add_upstream_rust_crates<'a, B: ArchiveBuilder<'a>>(
2061 cmd: &mut dyn Linker,
2063 codegen_results: &CodegenResults,
2064 crate_type: CrateType,
2067 // All of the heavy lifting has previously been accomplished by the
2068 // dependency_format module of the compiler. This is just crawling the
2069 // output of that module, adding crates as necessary.
2071 // Linking to a rlib involves just passing it to the linker (the linker
2072 // will slurp up the object files inside), and linking to a dynamic library
2073 // involves just passing the right -l flag.
2075 let (_, data) = codegen_results
2079 .find(|(ty, _)| *ty == crate_type)
2080 .expect("failed to find crate type in dependency format list");
2082 // Invoke get_used_crates to ensure that we get a topological sorting of
2084 let deps = &codegen_results.crate_info.used_crates_dynamic;
2086 // There's a few internal crates in the standard library (aka libcore and
2087 // libstd) which actually have a circular dependence upon one another. This
2088 // currently arises through "weak lang items" where libcore requires things
2089 // like `rust_begin_unwind` but libstd ends up defining it. To get this
2090 // circular dependence to work correctly in all situations we'll need to be
2091 // sure to correctly apply the `--start-group` and `--end-group` options to
2092 // GNU linkers, otherwise if we don't use any other symbol from the standard
2093 // library it'll get discarded and the whole application won't link.
2095 // In this loop we're calculating the `group_end`, after which crate to
2096 // pass `--end-group` and `group_start`, before which crate to pass
2097 // `--start-group`. We currently do this by passing `--end-group` after
2098 // the first crate (when iterating backwards) that requires a lang item
2099 // defined somewhere else. Once that's set then when we've defined all the
2100 // necessary lang items we'll pass `--start-group`.
2102 // Note that this isn't amazing logic for now but it should do the trick
2103 // for the current implementation of the standard library.
2104 let mut group_end = None;
2105 let mut group_start = None;
2106 // Crates available for linking thus far.
2107 let mut available = FxHashSet::default();
2108 // Crates required to satisfy dependencies discovered so far.
2109 let mut required = FxHashSet::default();
2111 let info = &codegen_results.crate_info;
2112 for &(cnum, _) in deps.iter().rev() {
2113 if let Some(missing) = info.missing_lang_items.get(&cnum) {
2114 let missing_crates = missing.iter().map(|i| info.lang_item_to_crate.get(i).copied());
2115 required.extend(missing_crates);
2118 required.insert(Some(cnum));
2119 available.insert(Some(cnum));
2121 if required.len() > available.len() && group_end.is_none() {
2122 group_end = Some(cnum);
2124 if required.len() == available.len() && group_end.is_some() {
2125 group_start = Some(cnum);
2130 // If we didn't end up filling in all lang items from upstream crates then
2131 // we'll be filling it in with our crate. This probably means we're the
2132 // standard library itself, so skip this for now.
2133 if group_end.is_some() && group_start.is_none() {
2137 let mut compiler_builtins = None;
2139 for &(cnum, _) in deps.iter() {
2140 if group_start == Some(cnum) {
2144 // We may not pass all crates through to the linker. Some crates may
2145 // appear statically in an existing dylib, meaning we'll pick up all the
2146 // symbols from the dylib.
2147 let src = &codegen_results.crate_info.used_crate_source[&cnum];
2148 match data[cnum.as_usize() - 1] {
2149 _ if codegen_results.crate_info.profiler_runtime == Some(cnum) => {
2150 add_static_crate::<B>(cmd, sess, codegen_results, tmpdir, crate_type, cnum);
2152 // compiler-builtins are always placed last to ensure that they're
2153 // linked correctly.
2154 _ if codegen_results.crate_info.compiler_builtins == Some(cnum) => {
2155 assert!(compiler_builtins.is_none());
2156 compiler_builtins = Some(cnum);
2158 Linkage::NotLinked | Linkage::IncludedFromDylib => {}
2159 Linkage::Static => {
2160 add_static_crate::<B>(cmd, sess, codegen_results, tmpdir, crate_type, cnum);
2162 Linkage::Dynamic => add_dynamic_crate(cmd, sess, &src.dylib.as_ref().unwrap().0),
2165 if group_end == Some(cnum) {
2170 // compiler-builtins are always placed last to ensure that they're
2171 // linked correctly.
2172 // We must always link the `compiler_builtins` crate statically. Even if it
2173 // was already "included" in a dylib (e.g., `libstd` when `-C prefer-dynamic`
2175 if let Some(cnum) = compiler_builtins {
2176 add_static_crate::<B>(cmd, sess, codegen_results, tmpdir, crate_type, cnum);
2179 // Converts a library file-stem into a cc -l argument
2180 fn unlib<'a>(target: &Target, stem: &'a str) -> &'a str {
2181 if stem.starts_with("lib") && !target.is_like_windows { &stem[3..] } else { stem }
2184 // Adds the static "rlib" versions of all crates to the command line.
2185 // There's a bit of magic which happens here specifically related to LTO,
2186 // namely that we remove upstream object files.
2188 // When performing LTO, almost(*) all of the bytecode from the upstream
2189 // libraries has already been included in our object file output. As a
2190 // result we need to remove the object files in the upstream libraries so
2191 // the linker doesn't try to include them twice (or whine about duplicate
2192 // symbols). We must continue to include the rest of the rlib, however, as
2193 // it may contain static native libraries which must be linked in.
2195 // (*) Crates marked with `#![no_builtins]` don't participate in LTO and
2196 // their bytecode wasn't included. The object files in those libraries must
2197 // still be passed to the linker.
2199 // Note, however, that if we're not doing LTO we can just pass the rlib
2200 // blindly to the linker (fast) because it's fine if it's not actually
2201 // included as we're at the end of the dependency chain.
2202 fn add_static_crate<'a, B: ArchiveBuilder<'a>>(
2203 cmd: &mut dyn Linker,
2205 codegen_results: &CodegenResults,
2207 crate_type: CrateType,
2210 let src = &codegen_results.crate_info.used_crate_source[&cnum];
2211 let cratepath = &src.rlib.as_ref().unwrap().0;
2213 let mut link_upstream = |path: &Path| {
2214 // If we're creating a dylib, then we need to include the
2215 // whole of each object in our archive into that artifact. This is
2216 // because a `dylib` can be reused as an intermediate artifact.
2218 // Note, though, that we don't want to include the whole of a
2219 // compiler-builtins crate (e.g., compiler-rt) because it'll get
2220 // repeatedly linked anyway.
2221 let path = fix_windows_verbatim_for_gcc(path);
2222 if crate_type == CrateType::Dylib
2223 && codegen_results.crate_info.compiler_builtins != Some(cnum)
2225 cmd.link_whole_rlib(&path);
2227 cmd.link_rlib(&path);
2231 // See the comment above in `link_staticlib` and `link_rlib` for why if
2232 // there's a static library that's not relevant we skip all object
2234 let native_libs = &codegen_results.crate_info.native_libraries[&cnum];
2235 let skip_native = native_libs.iter().any(|lib| {
2236 matches!(lib.kind, NativeLibKind::Static { bundle: None | Some(true), .. })
2237 && !relevant_lib(sess, lib)
2240 if (!are_upstream_rust_objects_already_included(sess)
2241 || ignored_for_lto(sess, &codegen_results.crate_info, cnum))
2244 link_upstream(cratepath);
2248 let dst = tmpdir.join(cratepath.file_name().unwrap());
2249 let name = cratepath.file_name().unwrap().to_str().unwrap();
2250 let name = &name[3..name.len() - 5]; // chop off lib/.rlib
2252 sess.prof.generic_activity_with_arg("link_altering_rlib", name).run(|| {
2253 let mut archive = <B as ArchiveBuilder>::new(sess, &dst, Some(cratepath));
2254 archive.update_symbols();
2256 let mut any_objects = false;
2257 for f in archive.src_files() {
2258 if f == METADATA_FILENAME {
2259 archive.remove_file(&f);
2263 let canonical = f.replace("-", "_");
2264 let canonical_name = name.replace("-", "_");
2266 let is_rust_object =
2267 canonical.starts_with(&canonical_name) && looks_like_rust_object_file(&f);
2269 // If we've been requested to skip all native object files
2270 // (those not generated by the rust compiler) then we can skip
2271 // this file. See above for why we may want to do this.
2272 let skip_because_cfg_say_so = skip_native && !is_rust_object;
2274 // If we're performing LTO and this is a rust-generated object
2275 // file, then we don't need the object file as it's part of the
2276 // LTO module. Note that `#![no_builtins]` is excluded from LTO,
2277 // though, so we let that object file slide.
2278 let skip_because_lto = are_upstream_rust_objects_already_included(sess)
2280 && (sess.target.no_builtins
2281 || !codegen_results.crate_info.is_no_builtins.contains(&cnum));
2283 if skip_because_cfg_say_so || skip_because_lto {
2284 archive.remove_file(&f);
2294 link_upstream(&dst);
2298 // Same thing as above, but for dynamic crates instead of static crates.
2299 fn add_dynamic_crate(cmd: &mut dyn Linker, sess: &Session, cratepath: &Path) {
2300 // Just need to tell the linker about where the library lives and
2302 let parent = cratepath.parent();
2303 if let Some(dir) = parent {
2304 cmd.include_path(&fix_windows_verbatim_for_gcc(dir));
2306 let filestem = cratepath.file_stem().unwrap().to_str().unwrap();
2307 cmd.link_rust_dylib(
2308 Symbol::intern(&unlib(&sess.target, filestem)),
2309 parent.unwrap_or_else(|| Path::new("")),
2314 /// Link in all of our upstream crates' native dependencies. Remember that all of these upstream
2315 /// native dependencies are all non-static dependencies. We've got two cases then:
2317 /// 1. The upstream crate is an rlib. In this case we *must* link in the native dependency because
2318 /// the rlib is just an archive.
2320 /// 2. The upstream crate is a dylib. In order to use the dylib, we have to have the dependency
2321 /// present on the system somewhere. Thus, we don't gain a whole lot from not linking in the
2322 /// dynamic dependency to this crate as well.
2324 /// The use case for this is a little subtle. In theory the native dependencies of a crate are
2325 /// purely an implementation detail of the crate itself, but the problem arises with generic and
2326 /// inlined functions. If a generic function calls a native function, then the generic function
2327 /// must be instantiated in the target crate, meaning that the native symbol must also be resolved
2328 /// in the target crate.
2329 fn add_upstream_native_libraries(
2330 cmd: &mut dyn Linker,
2332 codegen_results: &CodegenResults,
2333 crate_type: CrateType,
2335 // Be sure to use a topological sorting of crates because there may be
2336 // interdependencies between native libraries. When passing -nodefaultlibs,
2337 // for example, almost all native libraries depend on libc, so we have to
2338 // make sure that's all the way at the right (liblibc is near the base of
2339 // the dependency chain).
2341 // This passes RequireStatic, but the actual requirement doesn't matter,
2342 // we're just getting an ordering of crate numbers, we're not worried about
2344 let (_, data) = codegen_results
2348 .find(|(ty, _)| *ty == crate_type)
2349 .expect("failed to find crate type in dependency format list");
2351 let crates = &codegen_results.crate_info.used_crates_static;
2352 let mut last = (NativeLibKind::Unspecified, None);
2353 for &(cnum, _) in crates {
2354 for lib in codegen_results.crate_info.native_libraries[&cnum].iter() {
2355 let name = match lib.name {
2359 if !relevant_lib(sess, &lib) {
2363 // Skip if this library is the same as the last.
2364 last = if (lib.kind, lib.name) == last { continue } else { (lib.kind, lib.name) };
2366 let verbatim = lib.verbatim.unwrap_or(false);
2368 NativeLibKind::Dylib { as_needed } => {
2369 cmd.link_dylib(name, verbatim, as_needed.unwrap_or(true))
2371 NativeLibKind::Unspecified => cmd.link_dylib(name, verbatim, true),
2372 NativeLibKind::Framework { as_needed } => {
2373 cmd.link_framework(name, as_needed.unwrap_or(true))
2375 NativeLibKind::Static { bundle: Some(false), .. } => {
2376 // Link "static-nobundle" native libs only if the crate they originate from
2377 // is being linked statically to the current crate. If it's linked dynamically
2378 // or is an rlib already included via some other dylib crate, the symbols from
2379 // native libs will have already been included in that dylib.
2380 if data[cnum.as_usize() - 1] == Linkage::Static {
2381 cmd.link_staticlib(name, verbatim)
2384 // ignore statically included native libraries here as we've
2385 // already included them when we included the rust library
2387 NativeLibKind::Static { bundle: None | Some(true), .. } => {}
2388 NativeLibKind::RawDylib => {}
2394 fn relevant_lib(sess: &Session, lib: &NativeLib) -> bool {
2396 Some(ref cfg) => rustc_attr::cfg_matches(cfg, &sess.parse_sess, None),
2401 fn are_upstream_rust_objects_already_included(sess: &Session) -> bool {
2403 config::Lto::Fat => true,
2404 config::Lto::Thin => {
2405 // If we defer LTO to the linker, we haven't run LTO ourselves, so
2406 // any upstream object files have not been copied yet.
2407 !sess.opts.cg.linker_plugin_lto.enabled()
2409 config::Lto::No | config::Lto::ThinLocal => false,
2413 fn add_apple_sdk(cmd: &mut dyn Linker, sess: &Session, flavor: LinkerFlavor) {
2414 let arch = &sess.target.arch;
2415 let os = &sess.target.os;
2416 let llvm_target = &sess.target.llvm_target;
2417 if sess.target.vendor != "apple"
2418 || !matches!(os.as_str(), "ios" | "tvos")
2419 || flavor != LinkerFlavor::Gcc
2423 let sdk_name = match (arch.as_str(), os.as_str()) {
2424 ("aarch64", "tvos") => "appletvos",
2425 ("x86_64", "tvos") => "appletvsimulator",
2426 ("arm", "ios") => "iphoneos",
2427 ("aarch64", "ios") if llvm_target.contains("macabi") => "macosx",
2428 ("aarch64", "ios") if llvm_target.contains("sim") => "iphonesimulator",
2429 ("aarch64", "ios") => "iphoneos",
2430 ("x86", "ios") => "iphonesimulator",
2431 ("x86_64", "ios") if llvm_target.contains("macabi") => "macosx",
2432 ("x86_64", "ios") => "iphonesimulator",
2434 sess.err(&format!("unsupported arch `{}` for os `{}`", arch, os));
2438 let sdk_root = match get_apple_sdk_root(sdk_name) {
2445 if llvm_target.contains("macabi") {
2446 cmd.args(&["-target", llvm_target])
2448 let arch_name = llvm_target.split('-').next().expect("LLVM target must have a hyphen");
2449 cmd.args(&["-arch", arch_name])
2451 cmd.args(&["-isysroot", &sdk_root, "-Wl,-syslibroot", &sdk_root]);
2454 fn get_apple_sdk_root(sdk_name: &str) -> Result<String, String> {
2455 // Following what clang does
2456 // (https://github.com/llvm/llvm-project/blob/
2457 // 296a80102a9b72c3eda80558fb78a3ed8849b341/clang/lib/Driver/ToolChains/Darwin.cpp#L1661-L1678)
2458 // to allow the SDK path to be set. (For clang, xcrun sets
2459 // SDKROOT; for rustc, the user or build system can set it, or we
2460 // can fall back to checking for xcrun on PATH.)
2461 if let Ok(sdkroot) = env::var("SDKROOT") {
2462 let p = Path::new(&sdkroot);
2464 // Ignore `SDKROOT` if it's clearly set for the wrong platform.
2466 if sdkroot.contains("TVSimulator.platform")
2467 || sdkroot.contains("MacOSX.platform") => {}
2469 if sdkroot.contains("TVOS.platform") || sdkroot.contains("MacOSX.platform") => {}
2471 if sdkroot.contains("iPhoneSimulator.platform")
2472 || sdkroot.contains("MacOSX.platform") => {}
2474 if sdkroot.contains("iPhoneOS.platform") || sdkroot.contains("MacOSX.platform") => {
2477 if sdkroot.contains("iPhoneOS.platform")
2478 || sdkroot.contains("iPhoneSimulator.platform") => {}
2479 // Ignore `SDKROOT` if it's not a valid path.
2480 _ if !p.is_absolute() || p == Path::new("/") || !p.exists() => {}
2481 _ => return Ok(sdkroot),
2485 Command::new("xcrun").arg("--show-sdk-path").arg("-sdk").arg(sdk_name).output().and_then(
2487 if output.status.success() {
2488 Ok(String::from_utf8(output.stdout).unwrap())
2490 let error = String::from_utf8(output.stderr);
2491 let error = format!("process exit with error: {}", error.unwrap());
2492 Err(io::Error::new(io::ErrorKind::Other, &error[..]))
2498 Ok(output) => Ok(output.trim().to_string()),
2499 Err(e) => Err(format!("failed to get {} SDK path: {}", sdk_name, e)),