2 use super::command::Command;
3 use super::symbol_export;
4 use rustc_span::symbol::sym;
6 use std::ffi::{OsStr, OsString};
7 use std::fs::{self, File};
8 use std::io::prelude::*;
9 use std::io::{self, BufWriter};
11 use std::path::{Path, PathBuf};
13 use rustc_data_structures::fx::FxHashMap;
14 use rustc_hir::def_id::{CrateNum, LOCAL_CRATE};
15 use rustc_middle::middle::dependency_format::Linkage;
16 use rustc_middle::ty::TyCtxt;
17 use rustc_serialize::{json, Encoder};
18 use rustc_session::config::{self, CrateType, DebugInfo, LinkerPluginLto, Lto, OptLevel, Strip};
19 use rustc_session::Session;
20 use rustc_span::symbol::Symbol;
21 use rustc_target::spec::{LinkOutputKind, LinkerFlavor, LldFlavor};
23 /// Disables non-English messages from localized linkers.
24 /// Such messages may cause issues with text encoding on Windows (#35785)
25 /// and prevent inspection of linker output in case of errors, which we occasionally do.
26 /// This should be acceptable because other messages from rustc are in English anyway,
27 /// and may also be desirable to improve searchability of the linker diagnostics.
28 pub fn disable_localization(linker: &mut Command) {
29 // No harm in setting both env vars simultaneously.
30 // Unix-style linkers.
31 linker.env("LC_ALL", "C");
33 linker.env("VSLANG", "1033");
36 /// For all the linkers we support, and information they might
37 /// need out of the shared crate context before we get rid of it.
38 #[derive(RustcEncodable, RustcDecodable)]
39 pub struct LinkerInfo {
40 exports: FxHashMap<CrateType, Vec<String>>,
44 pub fn new(tcx: TyCtxt<'_>) -> LinkerInfo {
50 .map(|&c| (c, exported_symbols(tcx, c)))
61 ) -> Box<dyn Linker + 'a> {
63 LinkerFlavor::Lld(LldFlavor::Link) | LinkerFlavor::Msvc => {
64 Box::new(MsvcLinker { cmd, sess, info: self }) as Box<dyn Linker>
66 LinkerFlavor::Em => Box::new(EmLinker { cmd, sess, info: self }) as Box<dyn Linker>,
67 LinkerFlavor::Gcc => Box::new(GccLinker {
74 }) as Box<dyn Linker>,
76 LinkerFlavor::Lld(LldFlavor::Ld)
77 | LinkerFlavor::Lld(LldFlavor::Ld64)
78 | LinkerFlavor::Ld => Box::new(GccLinker {
85 }) as Box<dyn Linker>,
87 LinkerFlavor::Lld(LldFlavor::Wasm) => {
88 Box::new(WasmLd::new(cmd, sess, self)) as Box<dyn Linker>
91 LinkerFlavor::PtxLinker => Box::new(PtxLinker { cmd, sess }) as Box<dyn Linker>,
96 /// Linker abstraction used by `back::link` to build up the command to invoke a
99 /// This trait is the total list of requirements needed by `back::link` and
100 /// represents the meaning of each option being passed down. This trait is then
101 /// used to dispatch on whether a GNU-like linker (generally `ld.exe`) or an
102 /// MSVC linker (e.g., `link.exe`) is being used.
104 fn cmd(&mut self) -> &mut Command;
105 fn set_output_kind(&mut self, output_kind: LinkOutputKind, out_filename: &Path);
106 fn link_dylib(&mut self, lib: Symbol);
107 fn link_rust_dylib(&mut self, lib: Symbol, path: &Path);
108 fn link_framework(&mut self, framework: Symbol);
109 fn link_staticlib(&mut self, lib: Symbol);
110 fn link_rlib(&mut self, lib: &Path);
111 fn link_whole_rlib(&mut self, lib: &Path);
112 fn link_whole_staticlib(&mut self, lib: Symbol, search_path: &[PathBuf]);
113 fn include_path(&mut self, path: &Path);
114 fn framework_path(&mut self, path: &Path);
115 fn output_filename(&mut self, path: &Path);
116 fn add_object(&mut self, path: &Path);
117 fn gc_sections(&mut self, keep_metadata: bool);
118 fn full_relro(&mut self);
119 fn partial_relro(&mut self);
120 fn no_relro(&mut self);
121 fn optimize(&mut self);
122 fn pgo_gen(&mut self);
123 fn control_flow_guard(&mut self);
124 fn debuginfo(&mut self, strip: Strip);
125 fn no_crt_objects(&mut self);
126 fn no_default_libraries(&mut self);
127 fn export_symbols(&mut self, tmpdir: &Path, crate_type: CrateType);
128 fn subsystem(&mut self, subsystem: &str);
129 fn group_start(&mut self);
130 fn group_end(&mut self);
131 fn linker_plugin_lto(&mut self);
132 fn add_eh_frame_header(&mut self) {}
133 fn finalize(&mut self);
136 impl dyn Linker + '_ {
137 pub fn arg(&mut self, arg: impl AsRef<OsStr>) {
141 pub fn args(&mut self, args: impl IntoIterator<Item: AsRef<OsStr>>) {
142 self.cmd().args(args);
145 pub fn take_cmd(&mut self) -> Command {
146 mem::replace(self.cmd(), Command::new(""))
150 pub struct GccLinker<'a> {
153 info: &'a LinkerInfo,
154 hinted_static: bool, // Keeps track of the current hinting mode.
160 impl<'a> GccLinker<'a> {
161 /// Argument that must be passed *directly* to the linker
163 /// These arguments need to be prepended with `-Wl`, when a GCC-style linker is used.
164 fn linker_arg<S>(&mut self, arg: S) -> &mut Self
169 let mut os = OsString::from("-Wl,");
170 os.push(arg.as_ref());
178 fn takes_hints(&self) -> bool {
179 // Really this function only returns true if the underlying linker
180 // configured for a compiler is binutils `ld.bfd` and `ld.gold`. We
181 // don't really have a foolproof way to detect that, so rule out some
182 // platforms where currently this is guaranteed to *not* be the case:
184 // * On OSX they have their own linker, not binutils'
185 // * For WebAssembly the only functional linker is LLD, which doesn't
186 // support hint flags
187 !self.sess.target.target.options.is_like_osx && self.sess.target.target.arch != "wasm32"
190 // Some platforms take hints about whether a library is static or dynamic.
191 // For those that support this, we ensure we pass the option if the library
192 // was flagged "static" (most defaults are dynamic) to ensure that if
193 // libfoo.a and libfoo.so both exist that the right one is chosen.
194 fn hint_static(&mut self) {
195 if !self.takes_hints() {
198 if !self.hinted_static {
199 self.linker_arg("-Bstatic");
200 self.hinted_static = true;
204 fn hint_dynamic(&mut self) {
205 if !self.takes_hints() {
208 if self.hinted_static {
209 self.linker_arg("-Bdynamic");
210 self.hinted_static = false;
214 fn push_linker_plugin_lto_args(&mut self, plugin_path: Option<&OsStr>) {
215 if let Some(plugin_path) = plugin_path {
216 let mut arg = OsString::from("-plugin=");
217 arg.push(plugin_path);
218 self.linker_arg(&arg);
221 let opt_level = match self.sess.opts.optimize {
222 config::OptLevel::No => "O0",
223 config::OptLevel::Less => "O1",
224 config::OptLevel::Default => "O2",
225 config::OptLevel::Aggressive => "O3",
226 config::OptLevel::Size => "Os",
227 config::OptLevel::SizeMin => "Oz",
230 self.linker_arg(&format!("-plugin-opt={}", opt_level));
231 let target_cpu = self.target_cpu;
232 self.linker_arg(&format!("-plugin-opt=mcpu={}", target_cpu));
235 fn build_dylib(&mut self, out_filename: &Path) {
236 // On mac we need to tell the linker to let this library be rpathed
237 if self.sess.target.target.options.is_like_osx {
238 self.cmd.arg("-dynamiclib");
239 self.linker_arg("-dylib");
241 // Note that the `osx_rpath_install_name` option here is a hack
242 // purely to support rustbuild right now, we should get a more
243 // principled solution at some point to force the compiler to pass
244 // the right `-Wl,-install_name` with an `@rpath` in it.
245 if self.sess.opts.cg.rpath || self.sess.opts.debugging_opts.osx_rpath_install_name {
246 self.linker_arg("-install_name");
247 let mut v = OsString::from("@rpath/");
248 v.push(out_filename.file_name().unwrap());
252 self.cmd.arg("-shared");
253 if self.sess.target.target.options.is_like_windows {
254 // The output filename already contains `dll_suffix` so
255 // the resulting import library will have a name in the
256 // form of libfoo.dll.a
258 out_filename.file_name().and_then(|file| file.to_str()).map(|file| {
261 self.sess.target.target.options.staticlib_prefix,
263 self.sess.target.target.options.staticlib_suffix
266 if let Some(implib_name) = implib_name {
267 let implib = out_filename.parent().map(|dir| dir.join(&implib_name));
268 if let Some(implib) = implib {
269 self.linker_arg(&format!("--out-implib,{}", (*implib).to_str().unwrap()));
277 impl<'a> Linker for GccLinker<'a> {
278 fn cmd(&mut self) -> &mut Command {
282 fn set_output_kind(&mut self, output_kind: LinkOutputKind, out_filename: &Path) {
284 LinkOutputKind::DynamicNoPicExe => {
285 if !self.is_ld && self.sess.target.target.options.linker_is_gnu {
286 self.cmd.arg("-no-pie");
289 LinkOutputKind::DynamicPicExe => {
290 // `-pie` works for both gcc wrapper and ld.
291 self.cmd.arg("-pie");
293 LinkOutputKind::StaticNoPicExe => {
294 // `-static` works for both gcc wrapper and ld.
295 self.cmd.arg("-static");
296 if !self.is_ld && self.sess.target.target.options.linker_is_gnu {
297 self.cmd.arg("-no-pie");
300 LinkOutputKind::StaticPicExe => {
302 // Note that combination `-static -pie` doesn't work as expected
303 // for the gcc wrapper, `-static` in that case suppresses `-pie`.
304 self.cmd.arg("-static-pie");
306 // `--no-dynamic-linker` and `-z text` are not strictly necessary for producing
307 // a static pie, but currently passed because gcc and clang pass them.
308 // The former suppresses the `INTERP` ELF header specifying dynamic linker,
309 // which is otherwise implicitly injected by ld (but not lld).
310 // The latter doesn't change anything, only ensures that everything is pic.
311 self.cmd.args(&["-static", "-pie", "--no-dynamic-linker", "-z", "text"]);
314 LinkOutputKind::DynamicDylib => self.build_dylib(out_filename),
315 LinkOutputKind::StaticDylib => {
316 self.cmd.arg("-static");
317 self.build_dylib(out_filename);
320 // VxWorks compiler driver introduced `--static-crt` flag specifically for rustc,
321 // it switches linking for libc and similar system libraries to static without using
322 // any `#[link]` attributes in the `libc` crate, see #72782 for details.
323 // FIXME: Switch to using `#[link]` attributes in the `libc` crate
324 // similarly to other targets.
325 if self.sess.target.target.target_os == "vxworks"
328 LinkOutputKind::StaticNoPicExe
329 | LinkOutputKind::StaticPicExe
330 | LinkOutputKind::StaticDylib
333 self.cmd.arg("--static-crt");
337 fn link_dylib(&mut self, lib: Symbol) {
339 self.cmd.arg(format!("-l{}", lib));
341 fn link_staticlib(&mut self, lib: Symbol) {
343 self.cmd.arg(format!("-l{}", lib));
345 fn link_rlib(&mut self, lib: &Path) {
349 fn include_path(&mut self, path: &Path) {
350 self.cmd.arg("-L").arg(path);
352 fn framework_path(&mut self, path: &Path) {
353 self.cmd.arg("-F").arg(path);
355 fn output_filename(&mut self, path: &Path) {
356 self.cmd.arg("-o").arg(path);
358 fn add_object(&mut self, path: &Path) {
361 fn full_relro(&mut self) {
362 self.linker_arg("-zrelro");
363 self.linker_arg("-znow");
365 fn partial_relro(&mut self) {
366 self.linker_arg("-zrelro");
368 fn no_relro(&mut self) {
369 self.linker_arg("-znorelro");
372 fn link_rust_dylib(&mut self, lib: Symbol, _path: &Path) {
374 self.cmd.arg(format!("-l{}", lib));
377 fn link_framework(&mut self, framework: Symbol) {
379 self.cmd.arg("-framework").sym_arg(framework);
382 // Here we explicitly ask that the entire archive is included into the
383 // result artifact. For more details see #15460, but the gist is that
384 // the linker will strip away any unused objects in the archive if we
385 // don't otherwise explicitly reference them. This can occur for
386 // libraries which are just providing bindings, libraries with generic
388 fn link_whole_staticlib(&mut self, lib: Symbol, search_path: &[PathBuf]) {
390 let target = &self.sess.target.target;
391 if !target.options.is_like_osx {
392 self.linker_arg("--whole-archive").cmd.arg(format!("-l{}", lib));
393 self.linker_arg("--no-whole-archive");
395 // -force_load is the macOS equivalent of --whole-archive, but it
396 // involves passing the full path to the library to link.
397 self.linker_arg("-force_load");
398 let lib = archive::find_library(lib, search_path, &self.sess);
399 self.linker_arg(&lib);
403 fn link_whole_rlib(&mut self, lib: &Path) {
405 if self.sess.target.target.options.is_like_osx {
406 self.linker_arg("-force_load");
407 self.linker_arg(&lib);
409 self.linker_arg("--whole-archive").cmd.arg(lib);
410 self.linker_arg("--no-whole-archive");
414 fn gc_sections(&mut self, keep_metadata: bool) {
415 // The dead_strip option to the linker specifies that functions and data
416 // unreachable by the entry point will be removed. This is quite useful
417 // with Rust's compilation model of compiling libraries at a time into
418 // one object file. For example, this brings hello world from 1.7MB to
421 // Note that this is done for both executables and dynamic libraries. We
422 // won't get much benefit from dylibs because LLVM will have already
423 // stripped away as much as it could. This has not been seen to impact
424 // link times negatively.
426 // -dead_strip can't be part of the pre_link_args because it's also used
427 // for partial linking when using multiple codegen units (-r). So we
429 if self.sess.target.target.options.is_like_osx {
430 self.linker_arg("-dead_strip");
431 } else if self.sess.target.target.options.is_like_solaris {
432 self.linker_arg("-zignore");
434 // If we're building a dylib, we don't use --gc-sections because LLVM
435 // has already done the best it can do, and we also don't want to
436 // eliminate the metadata. If we're building an executable, however,
437 // --gc-sections drops the size of hello world from 1.8MB to 597K, a 67%
439 } else if !keep_metadata {
440 self.linker_arg("--gc-sections");
444 fn optimize(&mut self) {
445 if !self.sess.target.target.options.linker_is_gnu {
449 // GNU-style linkers support optimization with -O. GNU ld doesn't
450 // need a numeric argument, but other linkers do.
451 if self.sess.opts.optimize == config::OptLevel::Default
452 || self.sess.opts.optimize == config::OptLevel::Aggressive
454 self.linker_arg("-O1");
458 fn pgo_gen(&mut self) {
459 if !self.sess.target.target.options.linker_is_gnu {
463 // If we're doing PGO generation stuff and on a GNU-like linker, use the
464 // "-u" flag to properly pull in the profiler runtime bits.
466 // This is because LLVM otherwise won't add the needed initialization
467 // for us on Linux (though the extra flag should be harmless if it
470 // See https://reviews.llvm.org/D14033 and https://reviews.llvm.org/D14030.
472 // Though it may be worth to try to revert those changes upstream, since
473 // the overhead of the initialization should be minor.
475 self.cmd.arg("__llvm_profile_runtime");
478 fn control_flow_guard(&mut self) {}
480 fn debuginfo(&mut self, strip: Strip) {
483 Strip::Debuginfo => {
484 // MacOS linker does not support longhand argument --strip-debug
485 self.linker_arg("-S");
488 // MacOS linker does not support longhand argument --strip-all
489 self.linker_arg("-s");
494 fn no_crt_objects(&mut self) {
496 self.cmd.arg("-nostartfiles");
500 fn no_default_libraries(&mut self) {
502 self.cmd.arg("-nodefaultlibs");
506 fn export_symbols(&mut self, tmpdir: &Path, crate_type: CrateType) {
507 // Symbol visibility in object files typically takes care of this.
508 if crate_type == CrateType::Executable
509 && self.sess.target.target.options.override_export_symbols.is_none()
514 // We manually create a list of exported symbols to ensure we don't expose any more.
515 // The object files have far more public symbols than we actually want to export,
516 // so we hide them all here.
518 if !self.sess.target.target.options.limit_rdylib_exports {
522 if crate_type == CrateType::ProcMacro {
526 let is_windows = self.sess.target.target.options.is_like_windows;
527 let mut arg = OsString::new();
528 let path = tmpdir.join(if is_windows { "list.def" } else { "list" });
530 debug!("EXPORTED SYMBOLS:");
532 if self.sess.target.target.options.is_like_osx {
533 // Write a plain, newline-separated list of symbols
534 let res: io::Result<()> = try {
535 let mut f = BufWriter::new(File::create(&path)?);
536 for sym in self.info.exports[&crate_type].iter() {
538 writeln!(f, "_{}", sym)?;
541 if let Err(e) = res {
542 self.sess.fatal(&format!("failed to write lib.def file: {}", e));
544 } else if is_windows {
545 let res: io::Result<()> = try {
546 let mut f = BufWriter::new(File::create(&path)?);
548 // .def file similar to MSVC one but without LIBRARY section
549 // because LD doesn't like when it's empty
550 writeln!(f, "EXPORTS")?;
551 for symbol in self.info.exports[&crate_type].iter() {
552 debug!(" _{}", symbol);
553 writeln!(f, " {}", symbol)?;
556 if let Err(e) = res {
557 self.sess.fatal(&format!("failed to write list.def file: {}", e));
560 // Write an LD version script
561 let res: io::Result<()> = try {
562 let mut f = BufWriter::new(File::create(&path)?);
564 if !self.info.exports[&crate_type].is_empty() {
565 writeln!(f, " global:")?;
566 for sym in self.info.exports[&crate_type].iter() {
568 writeln!(f, " {};", sym)?;
571 writeln!(f, "\n local:\n *;\n}};")?;
573 if let Err(e) = res {
574 self.sess.fatal(&format!("failed to write version script: {}", e));
578 if self.sess.target.target.options.is_like_osx {
582 arg.push("-exported_symbols_list,");
583 } else if self.sess.target.target.options.is_like_solaris {
592 // Both LD and LLD accept export list in *.def file form, there are no flags required
594 arg.push("--version-script=")
602 fn subsystem(&mut self, subsystem: &str) {
603 self.linker_arg("--subsystem");
604 self.linker_arg(&subsystem);
607 fn finalize(&mut self) {
608 self.hint_dynamic(); // Reset to default before returning the composed command line.
611 fn group_start(&mut self) {
612 if self.takes_hints() {
613 self.linker_arg("--start-group");
617 fn group_end(&mut self) {
618 if self.takes_hints() {
619 self.linker_arg("--end-group");
623 fn linker_plugin_lto(&mut self) {
624 match self.sess.opts.cg.linker_plugin_lto {
625 LinkerPluginLto::Disabled => {
628 LinkerPluginLto::LinkerPluginAuto => {
629 self.push_linker_plugin_lto_args(None);
631 LinkerPluginLto::LinkerPlugin(ref path) => {
632 self.push_linker_plugin_lto_args(Some(path.as_os_str()));
637 // Add the `GNU_EH_FRAME` program header which is required to locate unwinding information.
638 // Some versions of `gcc` add it implicitly, some (e.g. `musl-gcc`) don't,
639 // so we just always add it.
640 fn add_eh_frame_header(&mut self) {
641 self.linker_arg("--eh-frame-hdr");
645 pub struct MsvcLinker<'a> {
648 info: &'a LinkerInfo,
651 impl<'a> Linker for MsvcLinker<'a> {
652 fn cmd(&mut self) -> &mut Command {
656 fn set_output_kind(&mut self, output_kind: LinkOutputKind, out_filename: &Path) {
658 LinkOutputKind::DynamicNoPicExe
659 | LinkOutputKind::DynamicPicExe
660 | LinkOutputKind::StaticNoPicExe
661 | LinkOutputKind::StaticPicExe => {}
662 LinkOutputKind::DynamicDylib | LinkOutputKind::StaticDylib => {
663 self.cmd.arg("/DLL");
664 let mut arg: OsString = "/IMPLIB:".into();
665 arg.push(out_filename.with_extension("dll.lib"));
671 fn link_rlib(&mut self, lib: &Path) {
674 fn add_object(&mut self, path: &Path) {
678 fn gc_sections(&mut self, _keep_metadata: bool) {
679 // MSVC's ICF (Identical COMDAT Folding) link optimization is
680 // slow for Rust and thus we disable it by default when not in
681 // optimization build.
682 if self.sess.opts.optimize != config::OptLevel::No {
683 self.cmd.arg("/OPT:REF,ICF");
685 // It is necessary to specify NOICF here, because /OPT:REF
686 // implies ICF by default.
687 self.cmd.arg("/OPT:REF,NOICF");
691 fn link_dylib(&mut self, lib: Symbol) {
692 self.cmd.arg(&format!("{}.lib", lib));
695 fn link_rust_dylib(&mut self, lib: Symbol, path: &Path) {
696 // When producing a dll, the MSVC linker may not actually emit a
697 // `foo.lib` file if the dll doesn't actually export any symbols, so we
698 // check to see if the file is there and just omit linking to it if it's
700 let name = format!("{}.dll.lib", lib);
701 if fs::metadata(&path.join(&name)).is_ok() {
706 fn link_staticlib(&mut self, lib: Symbol) {
707 self.cmd.arg(&format!("{}.lib", lib));
710 fn full_relro(&mut self) {
714 fn partial_relro(&mut self) {
718 fn no_relro(&mut self) {
722 fn no_crt_objects(&mut self) {
726 fn no_default_libraries(&mut self) {
727 self.cmd.arg("/NODEFAULTLIB");
730 fn include_path(&mut self, path: &Path) {
731 let mut arg = OsString::from("/LIBPATH:");
736 fn output_filename(&mut self, path: &Path) {
737 let mut arg = OsString::from("/OUT:");
742 fn framework_path(&mut self, _path: &Path) {
743 bug!("frameworks are not supported on windows")
745 fn link_framework(&mut self, _framework: Symbol) {
746 bug!("frameworks are not supported on windows")
749 fn link_whole_staticlib(&mut self, lib: Symbol, _search_path: &[PathBuf]) {
750 self.link_staticlib(lib);
751 self.cmd.arg(format!("/WHOLEARCHIVE:{}.lib", lib));
753 fn link_whole_rlib(&mut self, path: &Path) {
754 self.link_rlib(path);
755 let mut arg = OsString::from("/WHOLEARCHIVE:");
759 fn optimize(&mut self) {
760 // Needs more investigation of `/OPT` arguments
763 fn pgo_gen(&mut self) {
764 // Nothing needed here.
767 fn control_flow_guard(&mut self) {
768 self.cmd.arg("/guard:cf");
771 fn debuginfo(&mut self, strip: Strip) {
774 // This will cause the Microsoft linker to generate a PDB file
775 // from the CodeView line tables in the object files.
776 self.cmd.arg("/DEBUG");
778 // This will cause the Microsoft linker to embed .natvis info into the PDB file
779 let natvis_dir_path = self.sess.sysroot.join("lib\\rustlib\\etc");
780 if let Ok(natvis_dir) = fs::read_dir(&natvis_dir_path) {
781 for entry in natvis_dir {
784 let path = entry.path();
785 if path.extension() == Some("natvis".as_ref()) {
786 let mut arg = OsString::from("/NATVIS:");
793 .warn(&format!("error enumerating natvis directory: {}", err));
799 Strip::Debuginfo | Strip::Symbols => {
800 self.cmd.arg("/DEBUG:NONE");
805 // Currently the compiler doesn't use `dllexport` (an LLVM attribute) to
806 // export symbols from a dynamic library. When building a dynamic library,
807 // however, we're going to want some symbols exported, so this function
808 // generates a DEF file which lists all the symbols.
810 // The linker will read this `*.def` file and export all the symbols from
811 // the dynamic library. Note that this is not as simple as just exporting
812 // all the symbols in the current crate (as specified by `codegen.reachable`)
813 // but rather we also need to possibly export the symbols of upstream
814 // crates. Upstream rlibs may be linked statically to this dynamic library,
815 // in which case they may continue to transitively be used and hence need
816 // their symbols exported.
817 fn export_symbols(&mut self, tmpdir: &Path, crate_type: CrateType) {
818 // Symbol visibility takes care of this typically
819 if crate_type == CrateType::Executable {
823 let path = tmpdir.join("lib.def");
824 let res: io::Result<()> = try {
825 let mut f = BufWriter::new(File::create(&path)?);
827 // Start off with the standard module name header and then go
828 // straight to exports.
829 writeln!(f, "LIBRARY")?;
830 writeln!(f, "EXPORTS")?;
831 for symbol in self.info.exports[&crate_type].iter() {
832 debug!(" _{}", symbol);
833 writeln!(f, " {}", symbol)?;
836 if let Err(e) = res {
837 self.sess.fatal(&format!("failed to write lib.def file: {}", e));
839 let mut arg = OsString::from("/DEF:");
844 fn subsystem(&mut self, subsystem: &str) {
845 // Note that previous passes of the compiler validated this subsystem,
846 // so we just blindly pass it to the linker.
847 self.cmd.arg(&format!("/SUBSYSTEM:{}", subsystem));
849 // Windows has two subsystems we're interested in right now, the console
850 // and windows subsystems. These both implicitly have different entry
851 // points (starting symbols). The console entry point starts with
852 // `mainCRTStartup` and the windows entry point starts with
853 // `WinMainCRTStartup`. These entry points, defined in system libraries,
854 // will then later probe for either `main` or `WinMain`, respectively to
855 // start the application.
857 // In Rust we just always generate a `main` function so we want control
858 // to always start there, so we force the entry point on the windows
859 // subsystem to be `mainCRTStartup` to get everything booted up
862 // For more information see RFC #1665
863 if subsystem == "windows" {
864 self.cmd.arg("/ENTRY:mainCRTStartup");
868 fn finalize(&mut self) {}
870 // MSVC doesn't need group indicators
871 fn group_start(&mut self) {}
872 fn group_end(&mut self) {}
874 fn linker_plugin_lto(&mut self) {
879 pub struct EmLinker<'a> {
882 info: &'a LinkerInfo,
885 impl<'a> Linker for EmLinker<'a> {
886 fn cmd(&mut self) -> &mut Command {
890 fn set_output_kind(&mut self, _output_kind: LinkOutputKind, _out_filename: &Path) {}
892 fn include_path(&mut self, path: &Path) {
893 self.cmd.arg("-L").arg(path);
896 fn link_staticlib(&mut self, lib: Symbol) {
897 self.cmd.arg("-l").sym_arg(lib);
900 fn output_filename(&mut self, path: &Path) {
901 self.cmd.arg("-o").arg(path);
904 fn add_object(&mut self, path: &Path) {
908 fn link_dylib(&mut self, lib: Symbol) {
909 // Emscripten always links statically
910 self.link_staticlib(lib);
913 fn link_whole_staticlib(&mut self, lib: Symbol, _search_path: &[PathBuf]) {
915 self.link_staticlib(lib);
918 fn link_whole_rlib(&mut self, lib: &Path) {
923 fn link_rust_dylib(&mut self, lib: Symbol, _path: &Path) {
924 self.link_dylib(lib);
927 fn link_rlib(&mut self, lib: &Path) {
928 self.add_object(lib);
931 fn full_relro(&mut self) {
935 fn partial_relro(&mut self) {
939 fn no_relro(&mut self) {
943 fn framework_path(&mut self, _path: &Path) {
944 bug!("frameworks are not supported on Emscripten")
947 fn link_framework(&mut self, _framework: Symbol) {
948 bug!("frameworks are not supported on Emscripten")
951 fn gc_sections(&mut self, _keep_metadata: bool) {
955 fn optimize(&mut self) {
956 // Emscripten performs own optimizations
957 self.cmd.arg(match self.sess.opts.optimize {
958 OptLevel::No => "-O0",
959 OptLevel::Less => "-O1",
960 OptLevel::Default => "-O2",
961 OptLevel::Aggressive => "-O3",
962 OptLevel::Size => "-Os",
963 OptLevel::SizeMin => "-Oz",
965 // Unusable until https://github.com/rust-lang/rust/issues/38454 is resolved
966 self.cmd.args(&["--memory-init-file", "0"]);
969 fn pgo_gen(&mut self) {
970 // noop, but maybe we need something like the gnu linker?
973 fn control_flow_guard(&mut self) {}
975 fn debuginfo(&mut self, _strip: Strip) {
976 // Preserve names or generate source maps depending on debug info
977 self.cmd.arg(match self.sess.opts.debuginfo {
978 DebugInfo::None => "-g0",
979 DebugInfo::Limited => "-g3",
980 DebugInfo::Full => "-g4",
984 fn no_crt_objects(&mut self) {}
986 fn no_default_libraries(&mut self) {
987 self.cmd.args(&["-s", "DEFAULT_LIBRARY_FUNCS_TO_INCLUDE=[]"]);
990 fn export_symbols(&mut self, _tmpdir: &Path, crate_type: CrateType) {
991 let symbols = &self.info.exports[&crate_type];
993 debug!("EXPORTED SYMBOLS:");
997 let mut arg = OsString::from("EXPORTED_FUNCTIONS=");
998 let mut encoded = String::new();
1001 let mut encoder = json::Encoder::new(&mut encoded);
1002 let res = encoder.emit_seq(symbols.len(), |encoder| {
1003 for (i, sym) in symbols.iter().enumerate() {
1004 encoder.emit_seq_elt(i, |encoder| encoder.emit_str(&("_".to_owned() + sym)))?;
1008 if let Err(e) = res {
1009 self.sess.fatal(&format!("failed to encode exported symbols: {}", e));
1012 debug!("{}", encoded);
1018 fn subsystem(&mut self, _subsystem: &str) {
1022 fn finalize(&mut self) {}
1024 // Appears not necessary on Emscripten
1025 fn group_start(&mut self) {}
1026 fn group_end(&mut self) {}
1028 fn linker_plugin_lto(&mut self) {
1033 pub struct WasmLd<'a> {
1036 info: &'a LinkerInfo,
1039 impl<'a> WasmLd<'a> {
1040 fn new(mut cmd: Command, sess: &'a Session, info: &'a LinkerInfo) -> WasmLd<'a> {
1041 // If the atomics feature is enabled for wasm then we need a whole bunch
1044 // * `--shared-memory` - the link won't even succeed without this, flags
1045 // the one linear memory as `shared`
1047 // * `--max-memory=1G` - when specifying a shared memory this must also
1048 // be specified. We conservatively choose 1GB but users should be able
1049 // to override this with `-C link-arg`.
1051 // * `--import-memory` - it doesn't make much sense for memory to be
1052 // exported in a threaded module because typically you're
1053 // sharing memory and instantiating the module multiple times. As a
1054 // result if it were exported then we'd just have no sharing.
1056 // * `--export=__wasm_init_memory` - when using `--passive-segments` the
1057 // linker will synthesize this function, and so we need to make sure
1058 // that our usage of `--export` below won't accidentally cause this
1059 // function to get deleted.
1061 // * `--export=*tls*` - when `#[thread_local]` symbols are used these
1062 // symbols are how the TLS segments are initialized and configured.
1063 if sess.target_features.contains(&sym::atomics) {
1064 cmd.arg("--shared-memory");
1065 cmd.arg("--max-memory=1073741824");
1066 cmd.arg("--import-memory");
1067 cmd.arg("--export=__wasm_init_memory");
1068 cmd.arg("--export=__wasm_init_tls");
1069 cmd.arg("--export=__tls_size");
1070 cmd.arg("--export=__tls_align");
1071 cmd.arg("--export=__tls_base");
1073 WasmLd { cmd, sess, info }
1077 impl<'a> Linker for WasmLd<'a> {
1078 fn cmd(&mut self) -> &mut Command {
1082 fn set_output_kind(&mut self, output_kind: LinkOutputKind, _out_filename: &Path) {
1084 LinkOutputKind::DynamicNoPicExe
1085 | LinkOutputKind::DynamicPicExe
1086 | LinkOutputKind::StaticNoPicExe
1087 | LinkOutputKind::StaticPicExe => {}
1088 LinkOutputKind::DynamicDylib | LinkOutputKind::StaticDylib => {
1089 self.cmd.arg("--no-entry");
1094 fn link_dylib(&mut self, lib: Symbol) {
1095 self.cmd.arg("-l").sym_arg(lib);
1098 fn link_staticlib(&mut self, lib: Symbol) {
1099 self.cmd.arg("-l").sym_arg(lib);
1102 fn link_rlib(&mut self, lib: &Path) {
1106 fn include_path(&mut self, path: &Path) {
1107 self.cmd.arg("-L").arg(path);
1110 fn framework_path(&mut self, _path: &Path) {
1111 panic!("frameworks not supported")
1114 fn output_filename(&mut self, path: &Path) {
1115 self.cmd.arg("-o").arg(path);
1118 fn add_object(&mut self, path: &Path) {
1122 fn full_relro(&mut self) {}
1124 fn partial_relro(&mut self) {}
1126 fn no_relro(&mut self) {}
1128 fn link_rust_dylib(&mut self, lib: Symbol, _path: &Path) {
1129 self.cmd.arg("-l").sym_arg(lib);
1132 fn link_framework(&mut self, _framework: Symbol) {
1133 panic!("frameworks not supported")
1136 fn link_whole_staticlib(&mut self, lib: Symbol, _search_path: &[PathBuf]) {
1137 self.cmd.arg("-l").sym_arg(lib);
1140 fn link_whole_rlib(&mut self, lib: &Path) {
1144 fn gc_sections(&mut self, _keep_metadata: bool) {
1145 self.cmd.arg("--gc-sections");
1148 fn optimize(&mut self) {
1149 self.cmd.arg(match self.sess.opts.optimize {
1150 OptLevel::No => "-O0",
1151 OptLevel::Less => "-O1",
1152 OptLevel::Default => "-O2",
1153 OptLevel::Aggressive => "-O3",
1154 // Currently LLD doesn't support `Os` and `Oz`, so pass through `O2`
1156 OptLevel::Size => "-O2",
1157 OptLevel::SizeMin => "-O2",
1161 fn pgo_gen(&mut self) {}
1163 fn debuginfo(&mut self, strip: Strip) {
1166 Strip::Debuginfo => {
1167 self.cmd.arg("--strip-debug");
1170 self.cmd.arg("--strip-all");
1175 fn control_flow_guard(&mut self) {}
1177 fn no_crt_objects(&mut self) {}
1179 fn no_default_libraries(&mut self) {}
1181 fn export_symbols(&mut self, _tmpdir: &Path, crate_type: CrateType) {
1182 for sym in self.info.exports[&crate_type].iter() {
1183 self.cmd.arg("--export").arg(&sym);
1186 // LLD will hide these otherwise-internal symbols since it only exports
1187 // symbols explicity passed via the `--export` flags above and hides all
1188 // others. Various bits and pieces of tooling use this, so be sure these
1189 // symbols make their way out of the linker as well.
1190 self.cmd.arg("--export=__heap_base");
1191 self.cmd.arg("--export=__data_end");
1194 fn subsystem(&mut self, _subsystem: &str) {}
1196 fn finalize(&mut self) {}
1198 // Not needed for now with LLD
1199 fn group_start(&mut self) {}
1200 fn group_end(&mut self) {}
1202 fn linker_plugin_lto(&mut self) {
1203 // Do nothing for now
1207 fn exported_symbols(tcx: TyCtxt<'_>, crate_type: CrateType) -> Vec<String> {
1208 if let Some(ref exports) = tcx.sess.target.target.options.override_export_symbols {
1209 return exports.clone();
1212 let mut symbols = Vec::new();
1214 let export_threshold = symbol_export::crates_export_threshold(&[crate_type]);
1215 for &(symbol, level) in tcx.exported_symbols(LOCAL_CRATE).iter() {
1216 if level.is_below_threshold(export_threshold) {
1217 symbols.push(symbol_export::symbol_name_for_instance_in_crate(
1225 let formats = tcx.dependency_formats(LOCAL_CRATE);
1226 let deps = formats.iter().find_map(|(t, list)| (*t == crate_type).then_some(list)).unwrap();
1228 for (index, dep_format) in deps.iter().enumerate() {
1229 let cnum = CrateNum::new(index + 1);
1230 // For each dependency that we are linking to statically ...
1231 if *dep_format == Linkage::Static {
1232 // ... we add its symbol list to our export list.
1233 for &(symbol, level) in tcx.exported_symbols(cnum).iter() {
1234 if !level.is_below_threshold(export_threshold) {
1238 symbols.push(symbol_export::symbol_name_for_instance_in_crate(tcx, symbol, cnum));
1246 /// Much simplified and explicit CLI for the NVPTX linker. The linker operates
1247 /// with bitcode and uses LLVM backend to generate a PTX assembly.
1248 pub struct PtxLinker<'a> {
1253 impl<'a> Linker for PtxLinker<'a> {
1254 fn cmd(&mut self) -> &mut Command {
1258 fn set_output_kind(&mut self, _output_kind: LinkOutputKind, _out_filename: &Path) {}
1260 fn link_rlib(&mut self, path: &Path) {
1261 self.cmd.arg("--rlib").arg(path);
1264 fn link_whole_rlib(&mut self, path: &Path) {
1265 self.cmd.arg("--rlib").arg(path);
1268 fn include_path(&mut self, path: &Path) {
1269 self.cmd.arg("-L").arg(path);
1272 fn debuginfo(&mut self, _strip: Strip) {
1273 self.cmd.arg("--debug");
1276 fn add_object(&mut self, path: &Path) {
1277 self.cmd.arg("--bitcode").arg(path);
1280 fn optimize(&mut self) {
1281 match self.sess.lto() {
1282 Lto::Thin | Lto::Fat | Lto::ThinLocal => {
1283 self.cmd.arg("-Olto");
1290 fn output_filename(&mut self, path: &Path) {
1291 self.cmd.arg("-o").arg(path);
1294 fn finalize(&mut self) {
1295 // Provide the linker with fallback to internal `target-cpu`.
1296 self.cmd.arg("--fallback-arch").arg(match self.sess.opts.cg.target_cpu {
1298 None => &self.sess.target.target.options.cpu,
1302 fn link_dylib(&mut self, _lib: Symbol) {
1303 panic!("external dylibs not supported")
1306 fn link_rust_dylib(&mut self, _lib: Symbol, _path: &Path) {
1307 panic!("external dylibs not supported")
1310 fn link_staticlib(&mut self, _lib: Symbol) {
1311 panic!("staticlibs not supported")
1314 fn link_whole_staticlib(&mut self, _lib: Symbol, _search_path: &[PathBuf]) {
1315 panic!("staticlibs not supported")
1318 fn framework_path(&mut self, _path: &Path) {
1319 panic!("frameworks not supported")
1322 fn link_framework(&mut self, _framework: Symbol) {
1323 panic!("frameworks not supported")
1326 fn full_relro(&mut self) {}
1328 fn partial_relro(&mut self) {}
1330 fn no_relro(&mut self) {}
1332 fn gc_sections(&mut self, _keep_metadata: bool) {}
1334 fn pgo_gen(&mut self) {}
1336 fn no_crt_objects(&mut self) {}
1338 fn no_default_libraries(&mut self) {}
1340 fn control_flow_guard(&mut self) {}
1342 fn export_symbols(&mut self, _tmpdir: &Path, _crate_type: CrateType) {}
1344 fn subsystem(&mut self, _subsystem: &str) {}
1346 fn group_start(&mut self) {}
1348 fn group_end(&mut self) {}
1350 fn linker_plugin_lto(&mut self) {}