use rustc_arena::TypedArena; use rustc_ast::CRATE_NODE_ID; use rustc_data_structures::fx::FxHashSet; use rustc_data_structures::fx::FxIndexMap; use rustc_data_structures::memmap::Mmap; use rustc_data_structures::temp_dir::MaybeTempDir; use rustc_errors::{ErrorGuaranteed, Handler}; use rustc_fs_util::fix_windows_verbatim_for_gcc; use rustc_hir::def_id::CrateNum; use rustc_metadata::find_native_static_library; use rustc_metadata::fs::{emit_metadata, METADATA_FILENAME}; use rustc_middle::middle::dependency_format::Linkage; use rustc_middle::middle::exported_symbols::SymbolExportKind; use rustc_session::config::{self, CFGuard, CrateType, DebugInfo, LdImpl, Lto, Strip}; use rustc_session::config::{OutputFilenames, OutputType, PrintRequest, SplitDwarfKind}; use rustc_session::cstore::DllImport; use rustc_session::output::{check_file_is_writeable, invalid_output_for_target, out_filename}; use rustc_session::search_paths::PathKind; use rustc_session::utils::NativeLibKind; /// For all the linkers we support, and information they might /// need out of the shared crate context before we get rid of it. use rustc_session::{filesearch, Session}; use rustc_span::symbol::Symbol; use rustc_span::DebuggerVisualizerFile; use rustc_target::spec::crt_objects::{CrtObjects, LinkSelfContainedDefault}; use rustc_target::spec::{Cc, LinkOutputKind, LinkerFlavor, LinkerFlavorCli, Lld, PanicStrategy}; use rustc_target::spec::{RelocModel, RelroLevel, SanitizerSet, SplitDebuginfo, Target}; use super::archive::{ArchiveBuilder, ArchiveBuilderBuilder}; use super::command::Command; use super::linker::{self, Linker}; use super::metadata::{create_rmeta_file, MetadataPosition}; use super::rpath::{self, RPathConfig}; use crate::{ errors, looks_like_rust_object_file, CodegenResults, CompiledModule, CrateInfo, NativeLib, }; use cc::windows_registry; use regex::Regex; use tempfile::Builder as TempFileBuilder; use itertools::Itertools; use std::borrow::Borrow; use std::cell::OnceCell; use std::collections::BTreeSet; use std::ffi::OsString; use std::fs::{File, OpenOptions}; use std::io::{BufWriter, Write}; use std::ops::Deref; use std::path::{Path, PathBuf}; use std::process::{ExitStatus, Output, Stdio}; use std::{env, fmt, fs, io, mem, str}; pub fn ensure_removed(diag_handler: &Handler, path: &Path) { if let Err(e) = fs::remove_file(path) { if e.kind() != io::ErrorKind::NotFound { diag_handler.err(&format!("failed to remove {}: {}", path.display(), e)); } } } /// Performs the linkage portion of the compilation phase. This will generate all /// of the requested outputs for this compilation session. pub fn link_binary<'a>( sess: &'a Session, archive_builder_builder: &dyn ArchiveBuilderBuilder, codegen_results: &CodegenResults, outputs: &OutputFilenames, ) -> Result<(), ErrorGuaranteed> { let _timer = sess.timer("link_binary"); let output_metadata = sess.opts.output_types.contains_key(&OutputType::Metadata); for &crate_type in sess.crate_types().iter() { // Ignore executable crates if we have -Z no-codegen, as they will error. if (sess.opts.unstable_opts.no_codegen || !sess.opts.output_types.should_codegen()) && !output_metadata && crate_type == CrateType::Executable { continue; } if invalid_output_for_target(sess, crate_type) { bug!( "invalid output type `{:?}` for target os `{}`", crate_type, sess.opts.target_triple ); } sess.time("link_binary_check_files_are_writeable", || { for obj in codegen_results.modules.iter().filter_map(|m| m.object.as_ref()) { check_file_is_writeable(obj, sess); } }); if outputs.outputs.should_link() { let tmpdir = TempFileBuilder::new() .prefix("rustc") .tempdir() .unwrap_or_else(|error| sess.emit_fatal(errors::CreateTempDir { error })); let path = MaybeTempDir::new(tmpdir, sess.opts.cg.save_temps); let out_filename = out_filename( sess, crate_type, outputs, codegen_results.crate_info.local_crate_name.as_str(), ); match crate_type { CrateType::Rlib => { let _timer = sess.timer("link_rlib"); info!("preparing rlib to {:?}", out_filename); link_rlib( sess, archive_builder_builder, codegen_results, RlibFlavor::Normal, &path, )? .build(&out_filename); } CrateType::Staticlib => { link_staticlib( sess, archive_builder_builder, codegen_results, &out_filename, &path, )?; } _ => { link_natively( sess, archive_builder_builder, crate_type, &out_filename, codegen_results, path.as_ref(), )?; } } if sess.opts.json_artifact_notifications { sess.parse_sess.span_diagnostic.emit_artifact_notification(&out_filename, "link"); } if sess.prof.enabled() { if let Some(artifact_name) = out_filename.file_name() { // Record size for self-profiling let file_size = std::fs::metadata(&out_filename).map(|m| m.len()).unwrap_or(0); sess.prof.artifact_size( "linked_artifact", artifact_name.to_string_lossy(), file_size, ); } } } } // Remove the temporary object file and metadata if we aren't saving temps. sess.time("link_binary_remove_temps", || { // If the user requests that temporaries are saved, don't delete any. if sess.opts.cg.save_temps { return; } let maybe_remove_temps_from_module = |preserve_objects: bool, preserve_dwarf_objects: bool, module: &CompiledModule| { if !preserve_objects { if let Some(ref obj) = module.object { ensure_removed(sess.diagnostic(), obj); } } if !preserve_dwarf_objects { if let Some(ref dwo_obj) = module.dwarf_object { ensure_removed(sess.diagnostic(), dwo_obj); } } }; let remove_temps_from_module = |module: &CompiledModule| maybe_remove_temps_from_module(false, false, module); // Otherwise, always remove the metadata and allocator module temporaries. if let Some(ref metadata_module) = codegen_results.metadata_module { remove_temps_from_module(metadata_module); } if let Some(ref allocator_module) = codegen_results.allocator_module { remove_temps_from_module(allocator_module); } // If no requested outputs require linking, then the object temporaries should // be kept. if !sess.opts.output_types.should_link() { return; } // Potentially keep objects for their debuginfo. let (preserve_objects, preserve_dwarf_objects) = preserve_objects_for_their_debuginfo(sess); debug!(?preserve_objects, ?preserve_dwarf_objects); for module in &codegen_results.modules { maybe_remove_temps_from_module(preserve_objects, preserve_dwarf_objects, module); } }); Ok(()) } pub fn each_linked_rlib( sess: &Session, info: &CrateInfo, f: &mut dyn FnMut(CrateNum, &Path), ) -> Result<(), errors::LinkRlibError> { let crates = info.used_crates.iter(); let mut fmts = None; let lto_active = matches!(sess.lto(), Lto::Fat | Lto::Thin); if lto_active { for combination in info.dependency_formats.iter().combinations(2) { let (ty1, list1) = &combination[0]; let (ty2, list2) = &combination[1]; if list1 != list2 { return Err(errors::LinkRlibError::IncompatibleDependencyFormats { ty1: format!("{ty1:?}"), ty2: format!("{ty2:?}"), list1: format!("{list1:?}"), list2: format!("{list2:?}"), }); } } } for (ty, list) in info.dependency_formats.iter() { match ty { CrateType::Executable | CrateType::Staticlib | CrateType::Cdylib | CrateType::ProcMacro => { fmts = Some(list); break; } CrateType::Dylib if lto_active => { fmts = Some(list); break; } _ => {} } } let Some(fmts) = fmts else { return Err(errors::LinkRlibError::MissingFormat); }; for &cnum in crates { match fmts.get(cnum.as_usize() - 1) { Some(&Linkage::NotLinked | &Linkage::IncludedFromDylib) => continue, Some(_) => {} None => return Err(errors::LinkRlibError::MissingFormat), } let crate_name = info.crate_name[&cnum]; let used_crate_source = &info.used_crate_source[&cnum]; if let Some((path, _)) = &used_crate_source.rlib { f(cnum, &path); } else { if used_crate_source.rmeta.is_some() { return Err(errors::LinkRlibError::OnlyRmetaFound { crate_name }); } else { return Err(errors::LinkRlibError::NotFound { crate_name }); } } } Ok(()) } /// Create an 'rlib'. /// /// An rlib in its current incarnation is essentially a renamed .a file. The rlib primarily contains /// the object file of the crate, but it also contains all of the object files from native /// libraries. This is done by unzipping native libraries and inserting all of the contents into /// this archive. fn link_rlib<'a>( sess: &'a Session, archive_builder_builder: &dyn ArchiveBuilderBuilder, codegen_results: &CodegenResults, flavor: RlibFlavor, tmpdir: &MaybeTempDir, ) -> Result + 'a>, ErrorGuaranteed> { let lib_search_paths = archive_search_paths(sess); let mut ab = archive_builder_builder.new_archive_builder(sess); let trailing_metadata = match flavor { RlibFlavor::Normal => { let (metadata, metadata_position) = create_rmeta_file(sess, codegen_results.metadata.raw_data()); let metadata = emit_metadata(sess, &metadata, tmpdir); match metadata_position { MetadataPosition::First => { // Most of the time metadata in rlib files is wrapped in a "dummy" object // file for the target platform so the rlib can be processed entirely by // normal linkers for the platform. Sometimes this is not possible however. // If it is possible however, placing the metadata object first improves // performance of getting metadata from rlibs. ab.add_file(&metadata); None } MetadataPosition::Last => Some(metadata), } } RlibFlavor::StaticlibBase => None, }; for m in &codegen_results.modules { if let Some(obj) = m.object.as_ref() { ab.add_file(obj); } if let Some(dwarf_obj) = m.dwarf_object.as_ref() { ab.add_file(dwarf_obj); } } match flavor { RlibFlavor::Normal => {} RlibFlavor::StaticlibBase => { let obj = codegen_results.allocator_module.as_ref().and_then(|m| m.object.as_ref()); if let Some(obj) = obj { ab.add_file(obj); } } } // Used if packed_bundled_libs flag enabled. let mut packed_bundled_libs = Vec::new(); // Note that in this loop we are ignoring the value of `lib.cfg`. That is, // we may not be configured to actually include a static library if we're // adding it here. That's because later when we consume this rlib we'll // decide whether we actually needed the static library or not. // // To do this "correctly" we'd need to keep track of which libraries added // which object files to the archive. We don't do that here, however. The // #[link(cfg(..))] feature is unstable, though, and only intended to get // liblibc working. In that sense the check below just indicates that if // there are any libraries we want to omit object files for at link time we // just exclude all custom object files. // // Eventually if we want to stabilize or flesh out the #[link(cfg(..))] // feature then we'll need to figure out how to record what objects were // loaded from the libraries found here and then encode that into the // metadata of the rlib we're generating somehow. for lib in codegen_results.crate_info.used_libraries.iter() { match lib.kind { NativeLibKind::Static { bundle: None | Some(true), whole_archive: Some(true) } if flavor == RlibFlavor::Normal && sess.opts.unstable_opts.packed_bundled_libs => {} NativeLibKind::Static { bundle: None | Some(true), whole_archive: Some(true) } if flavor == RlibFlavor::Normal => { // Don't allow mixing +bundle with +whole_archive since an rlib may contain // multiple native libs, some of which are +whole-archive and some of which are // -whole-archive and it isn't clear how we can currently handle such a // situation correctly. // See https://github.com/rust-lang/rust/issues/88085#issuecomment-901050897 sess.emit_err(errors::IncompatibleLinkingModifiers); } NativeLibKind::Static { bundle: None | Some(true), .. } => {} NativeLibKind::Static { bundle: Some(false), .. } | NativeLibKind::Dylib { .. } | NativeLibKind::Framework { .. } | NativeLibKind::RawDylib | NativeLibKind::LinkArg | NativeLibKind::Unspecified => continue, } if let Some(name) = lib.name { let location = find_native_static_library(name.as_str(), lib.verbatim, &lib_search_paths, sess); if sess.opts.unstable_opts.packed_bundled_libs && flavor == RlibFlavor::Normal { packed_bundled_libs.push(find_native_static_library( lib.filename.unwrap().as_str(), Some(true), &lib_search_paths, sess, )); continue; } ab.add_archive(&location, Box::new(|_| false)).unwrap_or_else(|error| { sess.emit_fatal(errors::AddNativeLibrary { library_path: location, error }); }); } } for (raw_dylib_name, raw_dylib_imports) in collate_raw_dylibs(sess, codegen_results.crate_info.used_libraries.iter())? { let output_path = archive_builder_builder.create_dll_import_lib( sess, &raw_dylib_name, &raw_dylib_imports, tmpdir.as_ref(), true, ); ab.add_archive(&output_path, Box::new(|_| false)).unwrap_or_else(|error| { sess.emit_fatal(errors::AddNativeLibrary { library_path: output_path, error }); }); } if let Some(trailing_metadata) = trailing_metadata { // Note that it is important that we add all of our non-object "magical // files" *after* all of the object files in the archive. The reason for // this is as follows: // // * When performing LTO, this archive will be modified to remove // objects from above. The reason for this is described below. // // * When the system linker looks at an archive, it will attempt to // determine the architecture of the archive in order to see whether its // linkable. // // The algorithm for this detection is: iterate over the files in the // archive. Skip magical SYMDEF names. Interpret the first file as an // object file. Read architecture from the object file. // // * As one can probably see, if "metadata" and "foo.bc" were placed // before all of the objects, then the architecture of this archive would // not be correctly inferred once 'foo.o' is removed. // // * Most of the time metadata in rlib files is wrapped in a "dummy" object // file for the target platform so the rlib can be processed entirely by // normal linkers for the platform. Sometimes this is not possible however. // // Basically, all this means is that this code should not move above the // code above. ab.add_file(&trailing_metadata); } // Add all bundled static native library dependencies. // Archives added to the end of .rlib archive, see comment above for the reason. for lib in packed_bundled_libs { ab.add_file(&lib) } return Ok(ab); } /// Extract all symbols defined in raw-dylib libraries, collated by library name. /// /// If we have multiple extern blocks that specify symbols defined in the same raw-dylib library, /// then the CodegenResults value contains one NativeLib instance for each block. However, the /// linker appears to expect only a single import library for each library used, so we need to /// collate the symbols together by library name before generating the import libraries. fn collate_raw_dylibs<'a, 'b>( sess: &'a Session, used_libraries: impl IntoIterator, ) -> Result)>, ErrorGuaranteed> { // Use index maps to preserve original order of imports and libraries. let mut dylib_table = FxIndexMap::>::default(); for lib in used_libraries { if lib.kind == NativeLibKind::RawDylib { let ext = if matches!(lib.verbatim, Some(true)) { "" } else { ".dll" }; let name = format!("{}{}", lib.name.expect("unnamed raw-dylib library"), ext); let imports = dylib_table.entry(name.clone()).or_default(); for import in &lib.dll_imports { if let Some(old_import) = imports.insert(import.name, import) { // FIXME: when we add support for ordinals, figure out if we need to do anything // if we have two DllImport values with the same name but different ordinals. if import.calling_convention != old_import.calling_convention { sess.emit_err(errors::MultipleExternalFuncDecl { span: import.span, function: import.name, library_name: &name, }); } } } } } sess.compile_status()?; Ok(dylib_table .into_iter() .map(|(name, imports)| { (name, imports.into_iter().map(|(_, import)| import.clone()).collect()) }) .collect()) } /// Create a static archive. /// /// This is essentially the same thing as an rlib, but it also involves adding all of the upstream /// crates' objects into the archive. This will slurp in all of the native libraries of upstream /// dependencies as well. /// /// Additionally, there's no way for us to link dynamic libraries, so we warn about all dynamic /// library dependencies that they're not linked in. /// /// There's no need to include metadata in a static archive, so ensure to not link in the metadata /// object file (and also don't prepare the archive with a metadata file). fn link_staticlib<'a>( sess: &'a Session, archive_builder_builder: &dyn ArchiveBuilderBuilder, codegen_results: &CodegenResults, out_filename: &Path, tempdir: &MaybeTempDir, ) -> Result<(), ErrorGuaranteed> { info!("preparing staticlib to {:?}", out_filename); let mut ab = link_rlib( sess, archive_builder_builder, codegen_results, RlibFlavor::StaticlibBase, tempdir, )?; let mut all_native_libs = vec![]; let res = each_linked_rlib(sess, &codegen_results.crate_info, &mut |cnum, path| { let name = codegen_results.crate_info.crate_name[&cnum]; let native_libs = &codegen_results.crate_info.native_libraries[&cnum]; // Here when we include the rlib into our staticlib we need to make a // decision whether to include the extra object files along the way. // These extra object files come from statically included native // libraries, but they may be cfg'd away with #[link(cfg(..))]. // // This unstable feature, though, only needs liblibc to work. The only // use case there is where musl is statically included in liblibc.rlib, // so if we don't want the included version we just need to skip it. As // a result the logic here is that if *any* linked library is cfg'd away // we just skip all object files. // // Clearly this is not sufficient for a general purpose feature, and // we'd want to read from the library's metadata to determine which // object files come from where and selectively skip them. let skip_object_files = native_libs.iter().any(|lib| { matches!(lib.kind, NativeLibKind::Static { bundle: None | Some(true), .. }) && !relevant_lib(sess, lib) }); let lto = are_upstream_rust_objects_already_included(sess) && !ignored_for_lto(sess, &codegen_results.crate_info, cnum); // Ignoring obj file starting with the crate name // as simple comparison is not enough - there // might be also an extra name suffix let obj_start = name.as_str().to_owned(); ab.add_archive( path, Box::new(move |fname: &str| { // Ignore metadata files, no matter the name. if fname == METADATA_FILENAME { return true; } // Don't include Rust objects if LTO is enabled if lto && looks_like_rust_object_file(fname) { return true; } // Otherwise if this is *not* a rust object and we're skipping // objects then skip this file if skip_object_files && (!fname.starts_with(&obj_start) || !fname.ends_with(".o")) { return true; } // ok, don't skip this false }), ) .unwrap(); all_native_libs.extend(codegen_results.crate_info.native_libraries[&cnum].iter().cloned()); }); if let Err(e) = res { sess.emit_fatal(e); } ab.build(out_filename); if !all_native_libs.is_empty() { if sess.opts.prints.contains(&PrintRequest::NativeStaticLibs) { print_native_static_libs(sess, &all_native_libs); } } Ok(()) } /// Use `thorin` (rust implementation of a dwarf packaging utility) to link DWARF objects into a /// DWARF package. fn link_dwarf_object<'a>( sess: &'a Session, cg_results: &CodegenResults, executable_out_filename: &Path, ) { let dwp_out_filename = executable_out_filename.with_extension("dwp"); debug!(?dwp_out_filename, ?executable_out_filename); #[derive(Default)] struct ThorinSession { arena_data: TypedArena>, arena_mmap: TypedArena, arena_relocations: TypedArena, } impl ThorinSession { fn alloc_mmap<'arena>(&'arena self, data: Mmap) -> &'arena Mmap { (*self.arena_mmap.alloc(data)).borrow() } } impl thorin::Session for ThorinSession { fn alloc_data<'arena>(&'arena self, data: Vec) -> &'arena [u8] { (*self.arena_data.alloc(data)).borrow() } fn alloc_relocation<'arena>(&'arena self, data: Relocations) -> &'arena Relocations { (*self.arena_relocations.alloc(data)).borrow() } fn read_input<'arena>(&'arena self, path: &Path) -> std::io::Result<&'arena [u8]> { let file = File::open(&path)?; let mmap = (unsafe { Mmap::map(file) })?; Ok(self.alloc_mmap(mmap)) } } match sess.time("run_thorin", || -> Result<(), thorin::Error> { let thorin_sess = ThorinSession::default(); let mut package = thorin::DwarfPackage::new(&thorin_sess); // Input objs contain .o/.dwo files from the current crate. match sess.opts.unstable_opts.split_dwarf_kind { SplitDwarfKind::Single => { for input_obj in cg_results.modules.iter().filter_map(|m| m.object.as_ref()) { package.add_input_object(input_obj)?; } } SplitDwarfKind::Split => { for input_obj in cg_results.modules.iter().filter_map(|m| m.dwarf_object.as_ref()) { package.add_input_object(input_obj)?; } } } // Input rlibs contain .o/.dwo files from dependencies. let input_rlibs = cg_results .crate_info .used_crate_source .values() .filter_map(|csource| csource.rlib.as_ref()) .map(|(path, _)| path); for input_rlib in input_rlibs { debug!(?input_rlib); package.add_input_object(input_rlib)?; } // Failing to read the referenced objects is expected for dependencies where the path in the // executable will have been cleaned by Cargo, but the referenced objects will be contained // within rlibs provided as inputs. // // If paths have been remapped, then .o/.dwo files from the current crate also won't be // found, but are provided explicitly above. // // Adding an executable is primarily done to make `thorin` check that all the referenced // dwarf objects are found in the end. package.add_executable( &executable_out_filename, thorin::MissingReferencedObjectBehaviour::Skip, )?; let output = package.finish()?.write()?; let mut output_stream = BufWriter::new( OpenOptions::new() .read(true) .write(true) .create(true) .truncate(true) .open(dwp_out_filename)?, ); output_stream.write_all(&output)?; output_stream.flush()?; Ok(()) }) { Ok(()) => {} Err(e) => { sess.emit_err(errors::ThorinErrorWrapper(e)); sess.abort_if_errors(); } } } /// Create a dynamic library or executable. /// /// This will invoke the system linker/cc to create the resulting file. This links to all upstream /// files as well. fn link_natively<'a>( sess: &'a Session, archive_builder_builder: &dyn ArchiveBuilderBuilder, crate_type: CrateType, out_filename: &Path, codegen_results: &CodegenResults, tmpdir: &Path, ) -> Result<(), ErrorGuaranteed> { info!("preparing {:?} to {:?}", crate_type, out_filename); let (linker_path, flavor) = linker_and_flavor(sess); let mut cmd = linker_with_args( &linker_path, flavor, sess, archive_builder_builder, crate_type, tmpdir, out_filename, codegen_results, )?; linker::disable_localization(&mut cmd); for &(ref k, ref v) in sess.target.link_env.as_ref() { cmd.env(k.as_ref(), v.as_ref()); } for k in sess.target.link_env_remove.as_ref() { cmd.env_remove(k.as_ref()); } if sess.opts.prints.contains(&PrintRequest::LinkArgs) { println!("{:?}", &cmd); } // May have not found libraries in the right formats. sess.abort_if_errors(); // Invoke the system linker info!("{:?}", &cmd); let retry_on_segfault = env::var("RUSTC_RETRY_LINKER_ON_SEGFAULT").is_ok(); let unknown_arg_regex = Regex::new(r"(unknown|unrecognized) (command line )?(option|argument)").unwrap(); let mut prog; let mut i = 0; loop { i += 1; prog = sess.time("run_linker", || exec_linker(sess, &cmd, out_filename, tmpdir)); let Ok(ref output) = prog else { break; }; if output.status.success() { break; } let mut out = output.stderr.clone(); out.extend(&output.stdout); let out = String::from_utf8_lossy(&out); // Check to see if the link failed with an error message that indicates it // doesn't recognize the -no-pie option. If so, re-perform the link step // without it. This is safe because if the linker doesn't support -no-pie // then it should not default to linking executables as pie. Different // versions of gcc seem to use different quotes in the error message so // don't check for them. if matches!(flavor, LinkerFlavor::Gnu(Cc::Yes, _)) && unknown_arg_regex.is_match(&out) && out.contains("-no-pie") && cmd.get_args().iter().any(|e| e.to_string_lossy() == "-no-pie") { info!("linker output: {:?}", out); warn!("Linker does not support -no-pie command line option. Retrying without."); for arg in cmd.take_args() { if arg.to_string_lossy() != "-no-pie" { cmd.arg(arg); } } info!("{:?}", &cmd); continue; } // Detect '-static-pie' used with an older version of gcc or clang not supporting it. // Fallback from '-static-pie' to '-static' in that case. if matches!(flavor, LinkerFlavor::Gnu(Cc::Yes, _)) && unknown_arg_regex.is_match(&out) && (out.contains("-static-pie") || out.contains("--no-dynamic-linker")) && cmd.get_args().iter().any(|e| e.to_string_lossy() == "-static-pie") { info!("linker output: {:?}", out); warn!( "Linker does not support -static-pie command line option. Retrying with -static instead." ); // Mirror `add_(pre,post)_link_objects` to replace CRT objects. let self_contained = self_contained(sess, crate_type); let opts = &sess.target; let pre_objects = if self_contained { &opts.pre_link_objects_self_contained } else { &opts.pre_link_objects }; let post_objects = if self_contained { &opts.post_link_objects_self_contained } else { &opts.post_link_objects }; let get_objects = |objects: &CrtObjects, kind| { objects .get(&kind) .iter() .copied() .flatten() .map(|obj| get_object_file_path(sess, obj, self_contained).into_os_string()) .collect::>() }; let pre_objects_static_pie = get_objects(pre_objects, LinkOutputKind::StaticPicExe); let post_objects_static_pie = get_objects(post_objects, LinkOutputKind::StaticPicExe); let mut pre_objects_static = get_objects(pre_objects, LinkOutputKind::StaticNoPicExe); let mut post_objects_static = get_objects(post_objects, LinkOutputKind::StaticNoPicExe); // Assume that we know insertion positions for the replacement arguments from replaced // arguments, which is true for all supported targets. assert!(pre_objects_static.is_empty() || !pre_objects_static_pie.is_empty()); assert!(post_objects_static.is_empty() || !post_objects_static_pie.is_empty()); for arg in cmd.take_args() { if arg.to_string_lossy() == "-static-pie" { // Replace the output kind. cmd.arg("-static"); } else if pre_objects_static_pie.contains(&arg) { // Replace the pre-link objects (replace the first and remove the rest). cmd.args(mem::take(&mut pre_objects_static)); } else if post_objects_static_pie.contains(&arg) { // Replace the post-link objects (replace the first and remove the rest). cmd.args(mem::take(&mut post_objects_static)); } else { cmd.arg(arg); } } info!("{:?}", &cmd); continue; } // Here's a terribly awful hack that really shouldn't be present in any // compiler. Here an environment variable is supported to automatically // retry the linker invocation if the linker looks like it segfaulted. // // Gee that seems odd, normally segfaults are things we want to know // about! Unfortunately though in rust-lang/rust#38878 we're // experiencing the linker segfaulting on Travis quite a bit which is // causing quite a bit of pain to land PRs when they spuriously fail // due to a segfault. // // The issue #38878 has some more debugging information on it as well, // but this unfortunately looks like it's just a race condition in // macOS's linker with some thread pool working in the background. It // seems that no one currently knows a fix for this so in the meantime // we're left with this... if !retry_on_segfault || i > 3 { break; } let msg_segv = "clang: error: unable to execute command: Segmentation fault: 11"; let msg_bus = "clang: error: unable to execute command: Bus error: 10"; if out.contains(msg_segv) || out.contains(msg_bus) { warn!( ?cmd, %out, "looks like the linker segfaulted when we tried to call it, \ automatically retrying again", ); continue; } if is_illegal_instruction(&output.status) { warn!( ?cmd, %out, status = %output.status, "looks like the linker hit an illegal instruction when we \ tried to call it, automatically retrying again.", ); continue; } #[cfg(unix)] fn is_illegal_instruction(status: &ExitStatus) -> bool { use std::os::unix::prelude::*; status.signal() == Some(libc::SIGILL) } #[cfg(not(unix))] fn is_illegal_instruction(_status: &ExitStatus) -> bool { false } } match prog { Ok(prog) => { if !prog.status.success() { let mut output = prog.stderr.clone(); output.extend_from_slice(&prog.stdout); let escaped_output = escape_string(&output); // FIXME: Add UI tests for this error. let err = errors::LinkingFailed { linker_path: &linker_path, exit_status: prog.status, command: &cmd, escaped_output: &escaped_output, }; sess.diagnostic().emit_err(err); // If MSVC's `link.exe` was expected but the return code // is not a Microsoft LNK error then suggest a way to fix or // install the Visual Studio build tools. if let Some(code) = prog.status.code() { if sess.target.is_like_msvc && flavor == LinkerFlavor::Msvc(Lld::No) // Respect the command line override && sess.opts.cg.linker.is_none() // Match exactly "link.exe" && linker_path.to_str() == Some("link.exe") // All Microsoft `link.exe` linking error codes are // four digit numbers in the range 1000 to 9999 inclusive && (code < 1000 || code > 9999) { let is_vs_installed = windows_registry::find_vs_version().is_ok(); let has_linker = windows_registry::find_tool( &sess.opts.target_triple.triple(), "link.exe", ) .is_some(); sess.note_without_error("`link.exe` returned an unexpected error"); if is_vs_installed && has_linker { // the linker is broken sess.note_without_error( "the Visual Studio build tools may need to be repaired \ using the Visual Studio installer", ); sess.note_without_error( "or a necessary component may be missing from the \ \"C++ build tools\" workload", ); } else if is_vs_installed { // the linker is not installed sess.note_without_error( "in the Visual Studio installer, ensure the \ \"C++ build tools\" workload is selected", ); } else { // visual studio is not installed sess.note_without_error( "you may need to install Visual Studio build tools with the \ \"C++ build tools\" workload", ); } } } sess.abort_if_errors(); } info!("linker stderr:\n{}", escape_string(&prog.stderr)); info!("linker stdout:\n{}", escape_string(&prog.stdout)); } Err(e) => { let linker_not_found = e.kind() == io::ErrorKind::NotFound; let mut linker_error = { if linker_not_found { sess.struct_err(&format!("linker `{}` not found", linker_path.display())) } else { sess.struct_err(&format!( "could not exec the linker `{}`", linker_path.display() )) } }; linker_error.note(&e.to_string()); if !linker_not_found { linker_error.note(&format!("{:?}", &cmd)); } linker_error.emit(); if sess.target.is_like_msvc && linker_not_found { sess.note_without_error( "the msvc targets depend on the msvc linker \ but `link.exe` was not found", ); sess.note_without_error( "please ensure that Visual Studio 2017 or later, or Build Tools \ for Visual Studio were installed with the Visual C++ option.", ); sess.note_without_error("VS Code is a different product, and is not sufficient."); } sess.abort_if_errors(); } } match sess.split_debuginfo() { // If split debug information is disabled or located in individual files // there's nothing to do here. SplitDebuginfo::Off | SplitDebuginfo::Unpacked => {} // If packed split-debuginfo is requested, but the final compilation // doesn't actually have any debug information, then we skip this step. SplitDebuginfo::Packed if sess.opts.debuginfo == DebugInfo::None => {} // On macOS the external `dsymutil` tool is used to create the packed // debug information. Note that this will read debug information from // the objects on the filesystem which we'll clean up later. SplitDebuginfo::Packed if sess.target.is_like_osx => { let prog = Command::new("dsymutil").arg(out_filename).output(); match prog { Ok(prog) => { if !prog.status.success() { let mut output = prog.stderr.clone(); output.extend_from_slice(&prog.stdout); sess.struct_warn(&format!( "processing debug info with `dsymutil` failed: {}", prog.status )) .note(&escape_string(&output)) .emit(); } } Err(e) => sess.fatal(&format!("unable to run `dsymutil`: {}", e)), } } // On MSVC packed debug information is produced by the linker itself so // there's no need to do anything else here. SplitDebuginfo::Packed if sess.target.is_like_windows => {} // ... and otherwise we're processing a `*.dwp` packed dwarf file. // // We cannot rely on the .o paths in the executable because they may have been // remapped by --remap-path-prefix and therefore invalid, so we need to provide // the .o/.dwo paths explicitly. SplitDebuginfo::Packed => link_dwarf_object(sess, codegen_results, out_filename), } let strip = strip_value(sess); if sess.target.is_like_osx { match (strip, crate_type) { (Strip::Debuginfo, _) => { strip_symbols_with_external_utility(sess, "strip", &out_filename, Some("-S")) } // Per the manpage, `-x` is the maximum safe strip level for dynamic libraries. (#93988) (Strip::Symbols, CrateType::Dylib | CrateType::Cdylib | CrateType::ProcMacro) => { strip_symbols_with_external_utility(sess, "strip", &out_filename, Some("-x")) } (Strip::Symbols, _) => { strip_symbols_with_external_utility(sess, "strip", &out_filename, None) } (Strip::None, _) => {} } } if sess.target.os == "illumos" { // Many illumos systems will have both the native 'strip' utility and // the GNU one. Use the native version explicitly and do not rely on // what's in the path. let stripcmd = "/usr/bin/strip"; match strip { // Always preserve the symbol table (-x). Strip::Debuginfo => { strip_symbols_with_external_utility(sess, stripcmd, &out_filename, Some("-x")) } // Strip::Symbols is handled via the --strip-all linker option. Strip::Symbols => {} Strip::None => {} } } Ok(()) } // Temporarily support both -Z strip and -C strip fn strip_value(sess: &Session) -> Strip { match (sess.opts.unstable_opts.strip, sess.opts.cg.strip) { (s, Strip::None) => s, (_, s) => s, } } fn strip_symbols_with_external_utility<'a>( sess: &'a Session, util: &str, out_filename: &Path, option: Option<&str>, ) { let mut cmd = Command::new(util); if let Some(option) = option { cmd.arg(option); } let prog = cmd.arg(out_filename).output(); match prog { Ok(prog) => { if !prog.status.success() { let mut output = prog.stderr.clone(); output.extend_from_slice(&prog.stdout); sess.struct_warn(&format!( "stripping debug info with `{}` failed: {}", util, prog.status )) .note(&escape_string(&output)) .emit(); } } Err(e) => sess.fatal(&format!("unable to run `{}`: {}", util, e)), } } fn escape_string(s: &[u8]) -> String { match str::from_utf8(s) { Ok(s) => s.to_owned(), Err(_) => format!("Non-UTF-8 output: {}", s.escape_ascii()), } } fn add_sanitizer_libraries(sess: &Session, crate_type: CrateType, linker: &mut dyn Linker) { // On macOS the runtimes are distributed as dylibs which should be linked to // both executables and dynamic shared objects. Everywhere else the runtimes // are currently distributed as static libraries which should be linked to // executables only. let needs_runtime = !sess.target.is_like_android && match crate_type { CrateType::Executable => true, CrateType::Dylib | CrateType::Cdylib | CrateType::ProcMacro => sess.target.is_like_osx, CrateType::Rlib | CrateType::Staticlib => false, }; if !needs_runtime { return; } let sanitizer = sess.opts.unstable_opts.sanitizer; if sanitizer.contains(SanitizerSet::ADDRESS) { link_sanitizer_runtime(sess, linker, "asan"); } if sanitizer.contains(SanitizerSet::LEAK) { link_sanitizer_runtime(sess, linker, "lsan"); } if sanitizer.contains(SanitizerSet::MEMORY) { link_sanitizer_runtime(sess, linker, "msan"); } if sanitizer.contains(SanitizerSet::THREAD) { link_sanitizer_runtime(sess, linker, "tsan"); } if sanitizer.contains(SanitizerSet::HWADDRESS) { link_sanitizer_runtime(sess, linker, "hwasan"); } } fn link_sanitizer_runtime(sess: &Session, linker: &mut dyn Linker, name: &str) { fn find_sanitizer_runtime(sess: &Session, filename: &str) -> PathBuf { let session_tlib = filesearch::make_target_lib_path(&sess.sysroot, sess.opts.target_triple.triple()); let path = session_tlib.join(filename); if path.exists() { return session_tlib; } else { let default_sysroot = filesearch::get_or_default_sysroot(); let default_tlib = filesearch::make_target_lib_path( &default_sysroot, sess.opts.target_triple.triple(), ); return default_tlib; } } let channel = option_env!("CFG_RELEASE_CHANNEL") .map(|channel| format!("-{}", channel)) .unwrap_or_default(); if sess.target.is_like_osx { // On Apple platforms, the sanitizer is always built as a dylib, and // LLVM will link to `@rpath/*.dylib`, so we need to specify an // rpath to the library as well (the rpath should be absolute, see // PR #41352 for details). let filename = format!("rustc{}_rt.{}", channel, name); let path = find_sanitizer_runtime(&sess, &filename); let rpath = path.to_str().expect("non-utf8 component in path"); linker.args(&["-Wl,-rpath", "-Xlinker", rpath]); linker.link_dylib(&filename, false, true); } else { let filename = format!("librustc{}_rt.{}.a", channel, name); let path = find_sanitizer_runtime(&sess, &filename).join(&filename); linker.link_whole_rlib(&path); } } /// Returns a boolean indicating whether the specified crate should be ignored /// during LTO. /// /// Crates ignored during LTO are not lumped together in the "massive object /// file" that we create and are linked in their normal rlib states. See /// comments below for what crates do not participate in LTO. /// /// It's unusual for a crate to not participate in LTO. Typically only /// compiler-specific and unstable crates have a reason to not participate in /// LTO. pub fn ignored_for_lto(sess: &Session, info: &CrateInfo, cnum: CrateNum) -> bool { // If our target enables builtin function lowering in LLVM then the // crates providing these functions don't participate in LTO (e.g. // no_builtins or compiler builtins crates). !sess.target.no_builtins && (info.compiler_builtins == Some(cnum) || info.is_no_builtins.contains(&cnum)) } // This functions tries to determine the appropriate linker (and corresponding LinkerFlavor) to use pub fn linker_and_flavor(sess: &Session) -> (PathBuf, LinkerFlavor) { fn infer_from( sess: &Session, linker: Option, flavor: Option, ) -> Option<(PathBuf, LinkerFlavor)> { match (linker, flavor) { (Some(linker), Some(flavor)) => Some((linker, flavor)), // only the linker flavor is known; use the default linker for the selected flavor (None, Some(flavor)) => Some(( PathBuf::from(match flavor { LinkerFlavor::Gnu(Cc::Yes, _) | LinkerFlavor::Darwin(Cc::Yes, _) | LinkerFlavor::WasmLld(Cc::Yes) | LinkerFlavor::Unix(Cc::Yes) => { if cfg!(any(target_os = "solaris", target_os = "illumos")) { // On historical Solaris systems, "cc" may have // been Sun Studio, which is not flag-compatible // with "gcc". This history casts a long shadow, // and many modern illumos distributions today // ship GCC as "gcc" without also making it // available as "cc". "gcc" } else { "cc" } } LinkerFlavor::Gnu(_, Lld::Yes) | LinkerFlavor::Darwin(_, Lld::Yes) | LinkerFlavor::WasmLld(..) | LinkerFlavor::Msvc(Lld::Yes) => "lld", LinkerFlavor::Gnu(..) | LinkerFlavor::Darwin(..) | LinkerFlavor::Unix(..) => { "ld" } LinkerFlavor::Msvc(..) => "link.exe", LinkerFlavor::EmCc => { if cfg!(windows) { "emcc.bat" } else { "emcc" } } LinkerFlavor::Bpf => "bpf-linker", LinkerFlavor::Ptx => "rust-ptx-linker", }), flavor, )), (Some(linker), None) => { let stem = linker.file_stem().and_then(|stem| stem.to_str()).unwrap_or_else(|| { sess.fatal("couldn't extract file stem from specified linker") }); let flavor = if stem == "emcc" { LinkerFlavor::EmCc } else if stem == "gcc" || stem.ends_with("-gcc") || stem == "clang" || stem.ends_with("-clang") { LinkerFlavor::from_cli(LinkerFlavorCli::Gcc, &sess.target) } else if stem == "wasm-ld" || stem.ends_with("-wasm-ld") { LinkerFlavor::WasmLld(Cc::No) } else if stem == "ld" || stem.ends_with("-ld") { LinkerFlavor::from_cli(LinkerFlavorCli::Ld, &sess.target) } else if stem == "ld.lld" { LinkerFlavor::Gnu(Cc::No, Lld::Yes) } else if stem == "link" { LinkerFlavor::Msvc(Lld::No) } else if stem == "lld-link" { LinkerFlavor::Msvc(Lld::Yes) } else if stem == "lld" || stem == "rust-lld" { let lld_flavor = sess.target.linker_flavor.lld_flavor(); LinkerFlavor::from_cli(LinkerFlavorCli::Lld(lld_flavor), &sess.target) } else { // fall back to the value in the target spec sess.target.linker_flavor }; Some((linker, flavor)) } (None, None) => None, } } // linker and linker flavor specified via command line have precedence over what the target // specification specifies let linker_flavor = sess.opts.cg.linker_flavor.map(|flavor| LinkerFlavor::from_cli(flavor, &sess.target)); if let Some(ret) = infer_from(sess, sess.opts.cg.linker.clone(), linker_flavor) { return ret; } if let Some(ret) = infer_from( sess, sess.target.linker.as_deref().map(PathBuf::from), Some(sess.target.linker_flavor), ) { return ret; } bug!("Not enough information provided to determine how to invoke the linker"); } /// Returns a pair of boolean indicating whether we should preserve the object and /// dwarf object files on the filesystem for their debug information. This is often /// useful with split-dwarf like schemes. fn preserve_objects_for_their_debuginfo(sess: &Session) -> (bool, bool) { // If the objects don't have debuginfo there's nothing to preserve. if sess.opts.debuginfo == config::DebugInfo::None { return (false, false); } // If we're only producing artifacts that are archives, no need to preserve // the objects as they're losslessly contained inside the archives. if sess.crate_types().iter().all(|&x| x.is_archive()) { return (false, false); } match (sess.split_debuginfo(), sess.opts.unstable_opts.split_dwarf_kind) { // If there is no split debuginfo then do not preserve objects. (SplitDebuginfo::Off, _) => (false, false), // If there is packed split debuginfo, then the debuginfo in the objects // has been packaged and the objects can be deleted. (SplitDebuginfo::Packed, _) => (false, false), // If there is unpacked split debuginfo and the current target can not use // split dwarf, then keep objects. (SplitDebuginfo::Unpacked, _) if !sess.target_can_use_split_dwarf() => (true, false), // If there is unpacked split debuginfo and the target can use split dwarf, then // keep the object containing that debuginfo (whether that is an object file or // dwarf object file depends on the split dwarf kind). (SplitDebuginfo::Unpacked, SplitDwarfKind::Single) => (true, false), (SplitDebuginfo::Unpacked, SplitDwarfKind::Split) => (false, true), } } fn archive_search_paths(sess: &Session) -> Vec { sess.target_filesearch(PathKind::Native).search_path_dirs() } #[derive(PartialEq)] enum RlibFlavor { Normal, StaticlibBase, } fn print_native_static_libs(sess: &Session, all_native_libs: &[NativeLib]) { let lib_args: Vec<_> = all_native_libs .iter() .filter(|l| relevant_lib(sess, l)) .filter_map(|lib| { let name = lib.name?; match lib.kind { NativeLibKind::Static { bundle: Some(false), .. } | NativeLibKind::Dylib { .. } | NativeLibKind::Unspecified => { let verbatim = lib.verbatim.unwrap_or(false); if sess.target.is_like_msvc { Some(format!("{}{}", name, if verbatim { "" } else { ".lib" })) } else if sess.target.linker_flavor.is_gnu() { Some(format!("-l{}{}", if verbatim { ":" } else { "" }, name)) } else { Some(format!("-l{}", name)) } } NativeLibKind::Framework { .. } => { // ld-only syntax, since there are no frameworks in MSVC Some(format!("-framework {}", name)) } // These are included, no need to print them NativeLibKind::Static { bundle: None | Some(true), .. } | NativeLibKind::LinkArg | NativeLibKind::RawDylib => None, } }) .collect(); if !lib_args.is_empty() { sess.note_without_error( "Link against the following native artifacts when linking \ against this static library. The order and any duplication \ can be significant on some platforms.", ); // Prefix for greppability sess.note_without_error(&format!("native-static-libs: {}", &lib_args.join(" "))); } } fn get_object_file_path(sess: &Session, name: &str, self_contained: bool) -> PathBuf { let fs = sess.target_filesearch(PathKind::Native); let file_path = fs.get_lib_path().join(name); if file_path.exists() { return file_path; } // Special directory with objects used only in self-contained linkage mode if self_contained { let file_path = fs.get_self_contained_lib_path().join(name); if file_path.exists() { return file_path; } } for search_path in fs.search_paths() { let file_path = search_path.dir.join(name); if file_path.exists() { return file_path; } } PathBuf::from(name) } fn exec_linker( sess: &Session, cmd: &Command, out_filename: &Path, tmpdir: &Path, ) -> io::Result { // When attempting to spawn the linker we run a risk of blowing out the // size limits for spawning a new process with respect to the arguments // we pass on the command line. // // Here we attempt to handle errors from the OS saying "your list of // arguments is too big" by reinvoking the linker again with an `@`-file // that contains all the arguments. The theory is that this is then // accepted on all linkers and the linker will read all its options out of // there instead of looking at the command line. if !cmd.very_likely_to_exceed_some_spawn_limit() { match cmd.command().stdout(Stdio::piped()).stderr(Stdio::piped()).spawn() { Ok(child) => { let output = child.wait_with_output(); flush_linked_file(&output, out_filename)?; return output; } Err(ref e) if command_line_too_big(e) => { info!("command line to linker was too big: {}", e); } Err(e) => return Err(e), } } info!("falling back to passing arguments to linker via an @-file"); let mut cmd2 = cmd.clone(); let mut args = String::new(); for arg in cmd2.take_args() { args.push_str( &Escape { arg: arg.to_str().unwrap(), is_like_msvc: sess.target.is_like_msvc } .to_string(), ); args.push('\n'); } let file = tmpdir.join("linker-arguments"); let bytes = if sess.target.is_like_msvc { let mut out = Vec::with_capacity((1 + args.len()) * 2); // start the stream with a UTF-16 BOM for c in std::iter::once(0xFEFF).chain(args.encode_utf16()) { // encode in little endian out.push(c as u8); out.push((c >> 8) as u8); } out } else { args.into_bytes() }; fs::write(&file, &bytes)?; cmd2.arg(format!("@{}", file.display())); info!("invoking linker {:?}", cmd2); let output = cmd2.output(); flush_linked_file(&output, out_filename)?; return output; #[cfg(not(windows))] fn flush_linked_file(_: &io::Result, _: &Path) -> io::Result<()> { Ok(()) } #[cfg(windows)] fn flush_linked_file( command_output: &io::Result, out_filename: &Path, ) -> io::Result<()> { // On Windows, under high I/O load, output buffers are sometimes not flushed, // even long after process exit, causing nasty, non-reproducible output bugs. // // File::sync_all() calls FlushFileBuffers() down the line, which solves the problem. // // А full writeup of the original Chrome bug can be found at // randomascii.wordpress.com/2018/02/25/compiler-bug-linker-bug-windows-kernel-bug/amp if let &Ok(ref out) = command_output { if out.status.success() { if let Ok(of) = fs::OpenOptions::new().write(true).open(out_filename) { of.sync_all()?; } } } Ok(()) } #[cfg(unix)] fn command_line_too_big(err: &io::Error) -> bool { err.raw_os_error() == Some(::libc::E2BIG) } #[cfg(windows)] fn command_line_too_big(err: &io::Error) -> bool { const ERROR_FILENAME_EXCED_RANGE: i32 = 206; err.raw_os_error() == Some(ERROR_FILENAME_EXCED_RANGE) } #[cfg(not(any(unix, windows)))] fn command_line_too_big(_: &io::Error) -> bool { false } struct Escape<'a> { arg: &'a str, is_like_msvc: bool, } impl<'a> fmt::Display for Escape<'a> { fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result { if self.is_like_msvc { // This is "documented" at // https://docs.microsoft.com/en-us/cpp/build/reference/at-specify-a-linker-response-file // // Unfortunately there's not a great specification of the // syntax I could find online (at least) but some local // testing showed that this seemed sufficient-ish to catch // at least a few edge cases. write!(f, "\"")?; for c in self.arg.chars() { match c { '"' => write!(f, "\\{}", c)?, c => write!(f, "{}", c)?, } } write!(f, "\"")?; } else { // This is documented at https://linux.die.net/man/1/ld, namely: // // > Options in file are separated by whitespace. A whitespace // > character may be included in an option by surrounding the // > entire option in either single or double quotes. Any // > character (including a backslash) may be included by // > prefixing the character to be included with a backslash. // // We put an argument on each line, so all we need to do is // ensure the line is interpreted as one whole argument. for c in self.arg.chars() { match c { '\\' | ' ' => write!(f, "\\{}", c)?, c => write!(f, "{}", c)?, } } } Ok(()) } } } fn link_output_kind(sess: &Session, crate_type: CrateType) -> LinkOutputKind { let kind = match (crate_type, sess.crt_static(Some(crate_type)), sess.relocation_model()) { (CrateType::Executable, _, _) if sess.is_wasi_reactor() => LinkOutputKind::WasiReactorExe, (CrateType::Executable, false, RelocModel::Pic | RelocModel::Pie) => { LinkOutputKind::DynamicPicExe } (CrateType::Executable, false, _) => LinkOutputKind::DynamicNoPicExe, (CrateType::Executable, true, RelocModel::Pic | RelocModel::Pie) => { LinkOutputKind::StaticPicExe } (CrateType::Executable, true, _) => LinkOutputKind::StaticNoPicExe, (_, true, _) => LinkOutputKind::StaticDylib, (_, false, _) => LinkOutputKind::DynamicDylib, }; // Adjust the output kind to target capabilities. let opts = &sess.target; let pic_exe_supported = opts.position_independent_executables; let static_pic_exe_supported = opts.static_position_independent_executables; let static_dylib_supported = opts.crt_static_allows_dylibs; match kind { LinkOutputKind::DynamicPicExe if !pic_exe_supported => LinkOutputKind::DynamicNoPicExe, LinkOutputKind::StaticPicExe if !static_pic_exe_supported => LinkOutputKind::StaticNoPicExe, LinkOutputKind::StaticDylib if !static_dylib_supported => LinkOutputKind::DynamicDylib, _ => kind, } } // Returns true if linker is located within sysroot fn detect_self_contained_mingw(sess: &Session) -> bool { let (linker, _) = linker_and_flavor(&sess); // Assume `-C linker=rust-lld` as self-contained mode if linker == Path::new("rust-lld") { return true; } let linker_with_extension = if cfg!(windows) && linker.extension().is_none() { linker.with_extension("exe") } else { linker }; for dir in env::split_paths(&env::var_os("PATH").unwrap_or_default()) { let full_path = dir.join(&linker_with_extension); // If linker comes from sysroot assume self-contained mode if full_path.is_file() && !full_path.starts_with(&sess.sysroot) { return false; } } true } /// Various toolchain components used during linking are used from rustc distribution /// instead of being found somewhere on the host system. /// We only provide such support for a very limited number of targets. fn self_contained(sess: &Session, crate_type: CrateType) -> bool { if let Some(self_contained) = sess.opts.cg.link_self_contained { return self_contained; } match sess.target.link_self_contained { LinkSelfContainedDefault::False => false, LinkSelfContainedDefault::True => true, // FIXME: Find a better heuristic for "native musl toolchain is available", // based on host and linker path, for example. // (https://github.com/rust-lang/rust/pull/71769#issuecomment-626330237). LinkSelfContainedDefault::Musl => sess.crt_static(Some(crate_type)), LinkSelfContainedDefault::Mingw => { sess.host == sess.target && sess.target.vendor != "uwp" && detect_self_contained_mingw(&sess) } } } /// Add pre-link object files defined by the target spec. fn add_pre_link_objects( cmd: &mut dyn Linker, sess: &Session, flavor: LinkerFlavor, link_output_kind: LinkOutputKind, self_contained: bool, ) { // FIXME: we are currently missing some infra here (per-linker-flavor CRT objects), // so Fuchsia has to be special-cased. let opts = &sess.target; let empty = Default::default(); let objects = if self_contained { &opts.pre_link_objects_self_contained } else if !(sess.target.os == "fuchsia" && matches!(flavor, LinkerFlavor::Gnu(Cc::Yes, _))) { &opts.pre_link_objects } else { &empty }; for obj in objects.get(&link_output_kind).iter().copied().flatten() { cmd.add_object(&get_object_file_path(sess, obj, self_contained)); } } /// Add post-link object files defined by the target spec. fn add_post_link_objects( cmd: &mut dyn Linker, sess: &Session, link_output_kind: LinkOutputKind, self_contained: bool, ) { let objects = if self_contained { &sess.target.post_link_objects_self_contained } else { &sess.target.post_link_objects }; for obj in objects.get(&link_output_kind).iter().copied().flatten() { cmd.add_object(&get_object_file_path(sess, obj, self_contained)); } } /// Add arbitrary "pre-link" args defined by the target spec or from command line. /// FIXME: Determine where exactly these args need to be inserted. fn add_pre_link_args(cmd: &mut dyn Linker, sess: &Session, flavor: LinkerFlavor) { if let Some(args) = sess.target.pre_link_args.get(&flavor) { cmd.args(args.iter().map(Deref::deref)); } cmd.args(&sess.opts.unstable_opts.pre_link_args); } /// Add a link script embedded in the target, if applicable. fn add_link_script(cmd: &mut dyn Linker, sess: &Session, tmpdir: &Path, crate_type: CrateType) { match (crate_type, &sess.target.link_script) { (CrateType::Cdylib | CrateType::Executable, Some(script)) => { if !sess.target.linker_flavor.is_gnu() { sess.fatal("can only use link script when linking with GNU-like linker"); } let file_name = ["rustc", &sess.target.llvm_target, "linkfile.ld"].join("-"); let path = tmpdir.join(file_name); if let Err(e) = fs::write(&path, script.as_ref()) { sess.fatal(&format!("failed to write link script to {}: {}", path.display(), e)); } cmd.arg("--script"); cmd.arg(path); } _ => {} } } /// Add arbitrary "user defined" args defined from command line. /// FIXME: Determine where exactly these args need to be inserted. fn add_user_defined_link_args(cmd: &mut dyn Linker, sess: &Session) { cmd.args(&sess.opts.cg.link_args); } /// Add arbitrary "late link" args defined by the target spec. /// FIXME: Determine where exactly these args need to be inserted. fn add_late_link_args( cmd: &mut dyn Linker, sess: &Session, flavor: LinkerFlavor, crate_type: CrateType, codegen_results: &CodegenResults, ) { let any_dynamic_crate = crate_type == CrateType::Dylib || codegen_results.crate_info.dependency_formats.iter().any(|(ty, list)| { *ty == crate_type && list.iter().any(|&linkage| linkage == Linkage::Dynamic) }); if any_dynamic_crate { if let Some(args) = sess.target.late_link_args_dynamic.get(&flavor) { cmd.args(args.iter().map(Deref::deref)); } } else { if let Some(args) = sess.target.late_link_args_static.get(&flavor) { cmd.args(args.iter().map(Deref::deref)); } } if let Some(args) = sess.target.late_link_args.get(&flavor) { cmd.args(args.iter().map(Deref::deref)); } } /// Add arbitrary "post-link" args defined by the target spec. /// FIXME: Determine where exactly these args need to be inserted. fn add_post_link_args(cmd: &mut dyn Linker, sess: &Session, flavor: LinkerFlavor) { if let Some(args) = sess.target.post_link_args.get(&flavor) { cmd.args(args.iter().map(Deref::deref)); } } /// Add a synthetic object file that contains reference to all symbols that we want to expose to /// the linker. /// /// Background: we implement rlibs as static library (archives). Linkers treat archives /// differently from object files: all object files participate in linking, while archives will /// only participate in linking if they can satisfy at least one undefined reference (version /// scripts doesn't count). This causes `#[no_mangle]` or `#[used]` items to be ignored by the /// linker, and since they never participate in the linking, using `KEEP` in the linker scripts /// can't keep them either. This causes #47384. /// /// To keep them around, we could use `--whole-archive` and equivalents to force rlib to /// participate in linking like object files, but this proves to be expensive (#93791). Therefore /// we instead just introduce an undefined reference to them. This could be done by `-u` command /// line option to the linker or `EXTERN(...)` in linker scripts, however they does not only /// introduce an undefined reference, but also make them the GC roots, preventing `--gc-sections` /// from removing them, and this is especially problematic for embedded programming where every /// byte counts. /// /// This method creates a synthetic object file, which contains undefined references to all symbols /// that are necessary for the linking. They are only present in symbol table but not actually /// used in any sections, so the linker will therefore pick relevant rlibs for linking, but /// unused `#[no_mangle]` or `#[used]` can still be discard by GC sections. /// /// There's a few internal crates in the standard library (aka libcore and /// libstd) which actually have a circular dependence upon one another. This /// currently arises through "weak lang items" where libcore requires things /// like `rust_begin_unwind` but libstd ends up defining it. To get this /// circular dependence to work correctly we declare some of these things /// in this synthetic object. fn add_linked_symbol_object( cmd: &mut dyn Linker, sess: &Session, tmpdir: &Path, symbols: &[(String, SymbolExportKind)], ) { if symbols.is_empty() { return; } let Some(mut file) = super::metadata::create_object_file(sess) else { return; }; // NOTE(nbdd0121): MSVC will hang if the input object file contains no sections, // so add an empty section. if file.format() == object::BinaryFormat::Coff { file.add_section(Vec::new(), ".text".into(), object::SectionKind::Text); // We handle the name decoration of COFF targets in `symbol_export.rs`, so disable the // default mangler in `object` crate. file.set_mangling(object::write::Mangling::None); // Add feature flags to the object file. On MSVC this is optional but LLD will complain if // not present. let mut feature = 0; if file.architecture() == object::Architecture::I386 { // Indicate that all SEH handlers are registered in .sxdata section. // We don't have generate any code, so we don't need .sxdata section but LLD still // expects us to set this bit (see #96498). // Reference: https://docs.microsoft.com/en-us/windows/win32/debug/pe-format feature |= 1; } file.add_symbol(object::write::Symbol { name: "@feat.00".into(), value: feature, size: 0, kind: object::SymbolKind::Data, scope: object::SymbolScope::Compilation, weak: false, section: object::write::SymbolSection::Absolute, flags: object::SymbolFlags::None, }); } for (sym, kind) in symbols.iter() { file.add_symbol(object::write::Symbol { name: sym.clone().into(), value: 0, size: 0, kind: match kind { SymbolExportKind::Text => object::SymbolKind::Text, SymbolExportKind::Data => object::SymbolKind::Data, SymbolExportKind::Tls => object::SymbolKind::Tls, }, scope: object::SymbolScope::Unknown, weak: false, section: object::write::SymbolSection::Undefined, flags: object::SymbolFlags::None, }); } let path = tmpdir.join("symbols.o"); let result = std::fs::write(&path, file.write().unwrap()); if let Err(e) = result { sess.fatal(&format!("failed to write {}: {}", path.display(), e)); } cmd.add_object(&path); } /// Add object files containing code from the current crate. fn add_local_crate_regular_objects(cmd: &mut dyn Linker, codegen_results: &CodegenResults) { for obj in codegen_results.modules.iter().filter_map(|m| m.object.as_ref()) { cmd.add_object(obj); } } /// Add object files for allocator code linked once for the whole crate tree. fn add_local_crate_allocator_objects(cmd: &mut dyn Linker, codegen_results: &CodegenResults) { if let Some(obj) = codegen_results.allocator_module.as_ref().and_then(|m| m.object.as_ref()) { cmd.add_object(obj); } } /// Add object files containing metadata for the current crate. fn add_local_crate_metadata_objects( cmd: &mut dyn Linker, crate_type: CrateType, codegen_results: &CodegenResults, ) { // When linking a dynamic library, we put the metadata into a section of the // executable. This metadata is in a separate object file from the main // object file, so we link that in here. if crate_type == CrateType::Dylib || crate_type == CrateType::ProcMacro { if let Some(obj) = codegen_results.metadata_module.as_ref().and_then(|m| m.object.as_ref()) { cmd.add_object(obj); } } } /// Add sysroot and other globally set directories to the directory search list. fn add_library_search_dirs(cmd: &mut dyn Linker, sess: &Session, self_contained: bool) { // The default library location, we need this to find the runtime. // The location of crates will be determined as needed. let lib_path = sess.target_filesearch(PathKind::All).get_lib_path(); cmd.include_path(&fix_windows_verbatim_for_gcc(&lib_path)); // Special directory with libraries used only in self-contained linkage mode if self_contained { let lib_path = sess.target_filesearch(PathKind::All).get_self_contained_lib_path(); cmd.include_path(&fix_windows_verbatim_for_gcc(&lib_path)); } } /// Add options making relocation sections in the produced ELF files read-only /// and suppressing lazy binding. fn add_relro_args(cmd: &mut dyn Linker, sess: &Session) { match sess.opts.unstable_opts.relro_level.unwrap_or(sess.target.relro_level) { RelroLevel::Full => cmd.full_relro(), RelroLevel::Partial => cmd.partial_relro(), RelroLevel::Off => cmd.no_relro(), RelroLevel::None => {} } } /// Add library search paths used at runtime by dynamic linkers. fn add_rpath_args( cmd: &mut dyn Linker, sess: &Session, codegen_results: &CodegenResults, out_filename: &Path, ) { // FIXME (#2397): At some point we want to rpath our guesses as to // where extern libraries might live, based on the // add_lib_search_paths if sess.opts.cg.rpath { let libs = codegen_results .crate_info .used_crates .iter() .filter_map(|cnum| { codegen_results.crate_info.used_crate_source[cnum] .dylib .as_ref() .map(|(path, _)| &**path) }) .collect::>(); let mut rpath_config = RPathConfig { libs: &*libs, out_filename: out_filename.to_path_buf(), has_rpath: sess.target.has_rpath, is_like_osx: sess.target.is_like_osx, linker_is_gnu: sess.target.linker_flavor.is_gnu(), }; cmd.args(&rpath::get_rpath_flags(&mut rpath_config)); } } /// Produce the linker command line containing linker path and arguments. /// /// When comments in the function say "order-(in)dependent" they mean order-dependence between /// options and libraries/object files. For example `--whole-archive` (order-dependent) applies /// to specific libraries passed after it, and `-o` (output file, order-independent) applies /// to the linking process as a whole. /// Order-independent options may still override each other in order-dependent fashion, /// e.g `--foo=yes --foo=no` may be equivalent to `--foo=no`. fn linker_with_args<'a>( path: &Path, flavor: LinkerFlavor, sess: &'a Session, archive_builder_builder: &dyn ArchiveBuilderBuilder, crate_type: CrateType, tmpdir: &Path, out_filename: &Path, codegen_results: &CodegenResults, ) -> Result { let self_contained = self_contained(sess, crate_type); let cmd = &mut *super::linker::get_linker( sess, path, flavor, self_contained, &codegen_results.crate_info.target_cpu, ); let link_output_kind = link_output_kind(sess, crate_type); // ------------ Early order-dependent options ------------ // If we're building something like a dynamic library then some platforms // need to make sure that all symbols are exported correctly from the // dynamic library. // Must be passed before any libraries to prevent the symbols to export from being thrown away, // at least on some platforms (e.g. windows-gnu). cmd.export_symbols( tmpdir, crate_type, &codegen_results.crate_info.exported_symbols[&crate_type], ); // Can be used for adding custom CRT objects or overriding order-dependent options above. // FIXME: In practice built-in target specs use this for arbitrary order-independent options, // introduce a target spec option for order-independent linker options and migrate built-in // specs to it. add_pre_link_args(cmd, sess, flavor); // ------------ Object code and libraries, order-dependent ------------ // Pre-link CRT objects. add_pre_link_objects(cmd, sess, flavor, link_output_kind, self_contained); add_linked_symbol_object( cmd, sess, tmpdir, &codegen_results.crate_info.linked_symbols[&crate_type], ); // Sanitizer libraries. add_sanitizer_libraries(sess, crate_type, cmd); // Object code from the current crate. // Take careful note of the ordering of the arguments we pass to the linker // here. Linkers will assume that things on the left depend on things to the // right. Things on the right cannot depend on things on the left. This is // all formally implemented in terms of resolving symbols (libs on the right // resolve unknown symbols of libs on the left, but not vice versa). // // For this reason, we have organized the arguments we pass to the linker as // such: // // 1. The local object that LLVM just generated // 2. Local native libraries // 3. Upstream rust libraries // 4. Upstream native libraries // // The rationale behind this ordering is that those items lower down in the // list can't depend on items higher up in the list. For example nothing can // depend on what we just generated (e.g., that'd be a circular dependency). // Upstream rust libraries are not supposed to depend on our local native // libraries as that would violate the structure of the DAG, in that // scenario they are required to link to them as well in a shared fashion. // // Note that upstream rust libraries may contain native dependencies as // well, but they also can't depend on what we just started to add to the // link line. And finally upstream native libraries can't depend on anything // in this DAG so far because they can only depend on other native libraries // and such dependencies are also required to be specified. add_local_crate_regular_objects(cmd, codegen_results); add_local_crate_metadata_objects(cmd, crate_type, codegen_results); add_local_crate_allocator_objects(cmd, codegen_results); // Avoid linking to dynamic libraries unless they satisfy some undefined symbols // at the point at which they are specified on the command line. // Must be passed before any (dynamic) libraries to have effect on them. // On Solaris-like systems, `-z ignore` acts as both `--as-needed` and `--gc-sections` // so it will ignore unreferenced ELF sections from relocatable objects. // For that reason, we put this flag after metadata objects as they would otherwise be removed. // FIXME: Support more fine-grained dead code removal on Solaris/illumos // and move this option back to the top. cmd.add_as_needed(); // Local native libraries of all kinds. // // If `-Zlink-native-libraries=false` is set, then the assumption is that an // external build system already has the native dependencies defined, and it // will provide them to the linker itself. if sess.opts.unstable_opts.link_native_libraries { add_local_native_libraries(cmd, sess, codegen_results); } // Upstream rust libraries and their (possibly bundled) static native libraries. add_upstream_rust_crates( cmd, sess, archive_builder_builder, codegen_results, crate_type, tmpdir, ); // Dynamic native libraries from upstream crates. // // FIXME: Merge this to `add_upstream_rust_crates` so that all native libraries are linked // together with their respective upstream crates, and in their originally specified order. // This may be slightly breaking due to our use of `--as-needed` and needs a crater run. if sess.opts.unstable_opts.link_native_libraries { add_upstream_native_libraries(cmd, sess, codegen_results); } // Link with the import library generated for any raw-dylib functions. for (raw_dylib_name, raw_dylib_imports) in collate_raw_dylibs(sess, codegen_results.crate_info.used_libraries.iter())? { cmd.add_object(&archive_builder_builder.create_dll_import_lib( sess, &raw_dylib_name, &raw_dylib_imports, tmpdir, true, )); } // As with add_upstream_native_libraries, we need to add the upstream raw-dylib symbols in case // they are used within inlined functions or instantiated generic functions. We do this *after* // handling the raw-dylib symbols in the current crate to make sure that those are chosen first // by the linker. let (_, dependency_linkage) = codegen_results .crate_info .dependency_formats .iter() .find(|(ty, _)| *ty == crate_type) .expect("failed to find crate type in dependency format list"); let native_libraries_from_nonstatics = codegen_results .crate_info .native_libraries .iter() .filter_map(|(cnum, libraries)| { (dependency_linkage[cnum.as_usize() - 1] != Linkage::Static).then(|| libraries) }) .flatten(); for (raw_dylib_name, raw_dylib_imports) in collate_raw_dylibs(sess, native_libraries_from_nonstatics)? { cmd.add_object(&archive_builder_builder.create_dll_import_lib( sess, &raw_dylib_name, &raw_dylib_imports, tmpdir, false, )); } // Library linking above uses some global state for things like `-Bstatic`/`-Bdynamic` to make // command line shorter, reset it to default here before adding more libraries. cmd.reset_per_library_state(); // FIXME: Built-in target specs occasionally use this for linking system libraries, // eliminate all such uses by migrating them to `#[link]` attributes in `lib(std,c,unwind)` // and remove the option. add_late_link_args(cmd, sess, flavor, crate_type, codegen_results); // ------------ Arbitrary order-independent options ------------ // Add order-independent options determined by rustc from its compiler options, // target properties and source code. add_order_independent_options( cmd, sess, link_output_kind, self_contained, flavor, crate_type, codegen_results, out_filename, tmpdir, ); // Can be used for arbitrary order-independent options. // In practice may also be occasionally used for linking native libraries. // Passed after compiler-generated options to support manual overriding when necessary. add_user_defined_link_args(cmd, sess); // ------------ Object code and libraries, order-dependent ------------ // Post-link CRT objects. add_post_link_objects(cmd, sess, link_output_kind, self_contained); // ------------ Late order-dependent options ------------ // Doesn't really make sense. // FIXME: In practice built-in target specs use this for arbitrary order-independent options, // introduce a target spec option for order-independent linker options, migrate built-in specs // to it and remove the option. add_post_link_args(cmd, sess, flavor); Ok(cmd.take_cmd()) } fn add_order_independent_options( cmd: &mut dyn Linker, sess: &Session, link_output_kind: LinkOutputKind, self_contained: bool, flavor: LinkerFlavor, crate_type: CrateType, codegen_results: &CodegenResults, out_filename: &Path, tmpdir: &Path, ) { add_gcc_ld_path(cmd, sess, flavor); add_apple_sdk(cmd, sess, flavor); add_link_script(cmd, sess, tmpdir, crate_type); if sess.target.os == "fuchsia" && crate_type == CrateType::Executable && !matches!(flavor, LinkerFlavor::Gnu(Cc::Yes, _)) { let prefix = if sess.opts.unstable_opts.sanitizer.contains(SanitizerSet::ADDRESS) { "asan/" } else { "" }; cmd.arg(format!("--dynamic-linker={}ld.so.1", prefix)); } if sess.target.eh_frame_header { cmd.add_eh_frame_header(); } // Make the binary compatible with data execution prevention schemes. cmd.add_no_exec(); if self_contained { cmd.no_crt_objects(); } if sess.target.os == "emscripten" { cmd.arg("-s"); cmd.arg(if sess.panic_strategy() == PanicStrategy::Abort { "DISABLE_EXCEPTION_CATCHING=1" } else { "DISABLE_EXCEPTION_CATCHING=0" }); } if flavor == LinkerFlavor::Ptx { // Provide the linker with fallback to internal `target-cpu`. cmd.arg("--fallback-arch"); cmd.arg(&codegen_results.crate_info.target_cpu); } else if flavor == LinkerFlavor::Bpf { cmd.arg("--cpu"); cmd.arg(&codegen_results.crate_info.target_cpu); cmd.arg("--cpu-features"); cmd.arg(match &sess.opts.cg.target_feature { feat if !feat.is_empty() => feat.as_ref(), _ => sess.target.options.features.as_ref(), }); } cmd.linker_plugin_lto(); add_library_search_dirs(cmd, sess, self_contained); cmd.output_filename(out_filename); if crate_type == CrateType::Executable && sess.target.is_like_windows { if let Some(ref s) = codegen_results.crate_info.windows_subsystem { cmd.subsystem(s); } } // Try to strip as much out of the generated object by removing unused // sections if possible. See more comments in linker.rs if !sess.link_dead_code() { // If PGO is enabled sometimes gc_sections will remove the profile data section // as it appears to be unused. This can then cause the PGO profile file to lose // some functions. If we are generating a profile we shouldn't strip those metadata // sections to ensure we have all the data for PGO. let keep_metadata = crate_type == CrateType::Dylib || sess.opts.cg.profile_generate.enabled(); if crate_type != CrateType::Executable || !sess.opts.unstable_opts.export_executable_symbols { cmd.gc_sections(keep_metadata); } else { cmd.no_gc_sections(); } } cmd.set_output_kind(link_output_kind, out_filename); add_relro_args(cmd, sess); // Pass optimization flags down to the linker. cmd.optimize(); // Gather the set of NatVis files, if any, and write them out to a temp directory. let natvis_visualizers = collect_natvis_visualizers( tmpdir, sess, &codegen_results.crate_info.local_crate_name, &codegen_results.crate_info.natvis_debugger_visualizers, ); // Pass debuginfo, NatVis debugger visualizers and strip flags down to the linker. cmd.debuginfo(strip_value(sess), &natvis_visualizers); // We want to prevent the compiler from accidentally leaking in any system libraries, // so by default we tell linkers not to link to any default libraries. if !sess.opts.cg.default_linker_libraries && sess.target.no_default_libraries { cmd.no_default_libraries(); } if sess.opts.cg.profile_generate.enabled() || sess.instrument_coverage() { cmd.pgo_gen(); } if sess.opts.cg.control_flow_guard != CFGuard::Disabled { cmd.control_flow_guard(); } add_rpath_args(cmd, sess, codegen_results, out_filename); } // Write the NatVis debugger visualizer files for each crate to the temp directory and gather the file paths. fn collect_natvis_visualizers( tmpdir: &Path, sess: &Session, crate_name: &Symbol, natvis_debugger_visualizers: &BTreeSet, ) -> Vec { let mut visualizer_paths = Vec::with_capacity(natvis_debugger_visualizers.len()); for (index, visualizer) in natvis_debugger_visualizers.iter().enumerate() { let visualizer_out_file = tmpdir.join(format!("{}-{}.natvis", crate_name.as_str(), index)); match fs::write(&visualizer_out_file, &visualizer.src) { Ok(()) => { visualizer_paths.push(visualizer_out_file); } Err(error) => { sess.warn( format!( "Unable to write debugger visualizer file `{}`: {} ", visualizer_out_file.display(), error ) .as_str(), ); } }; } visualizer_paths } /// # Native library linking /// /// User-supplied library search paths (-L on the command line). These are the same paths used to /// find Rust crates, so some of them may have been added already by the previous crate linking /// code. This only allows them to be found at compile time so it is still entirely up to outside /// forces to make sure that library can be found at runtime. /// /// Also note that the native libraries linked here are only the ones located in the current crate. /// Upstream crates with native library dependencies may have their native library pulled in above. fn add_local_native_libraries( cmd: &mut dyn Linker, sess: &Session, codegen_results: &CodegenResults, ) { let filesearch = sess.target_filesearch(PathKind::All); for search_path in filesearch.search_paths() { match search_path.kind { PathKind::Framework => { cmd.framework_path(&search_path.dir); } _ => { cmd.include_path(&fix_windows_verbatim_for_gcc(&search_path.dir)); } } } let relevant_libs = codegen_results.crate_info.used_libraries.iter().filter(|l| relevant_lib(sess, l)); let search_path = OnceCell::new(); let mut last = (None, NativeLibKind::Unspecified, None); for lib in relevant_libs { let Some(name) = lib.name else { continue; }; let name = name.as_str(); // Skip if this library is the same as the last. last = if (lib.name, lib.kind, lib.verbatim) == last { continue; } else { (lib.name, lib.kind, lib.verbatim) }; let verbatim = lib.verbatim.unwrap_or(false); match lib.kind { NativeLibKind::Dylib { as_needed } => { cmd.link_dylib(name, verbatim, as_needed.unwrap_or(true)) } NativeLibKind::Unspecified => cmd.link_dylib(name, verbatim, true), NativeLibKind::Framework { as_needed } => { cmd.link_framework(name, as_needed.unwrap_or(true)) } NativeLibKind::Static { whole_archive, bundle, .. } => { if whole_archive == Some(true) // Backward compatibility case: this can be a rlib (so `+whole-archive` cannot // be added explicitly if necessary, see the error in `fn link_rlib`) compiled // as an executable due to `--test`. Use whole-archive implicitly, like before // the introduction of native lib modifiers. || (whole_archive == None && bundle != Some(false) && sess.opts.test) { cmd.link_whole_staticlib( name, verbatim, &search_path.get_or_init(|| archive_search_paths(sess)), ); } else { cmd.link_staticlib(name, verbatim) } } NativeLibKind::RawDylib => { // Ignore RawDylib here, they are handled separately in linker_with_args(). } NativeLibKind::LinkArg => { cmd.arg(name); } } } } /// # Linking Rust crates and their non-bundled static libraries /// /// Rust crates are not considered at all when creating an rlib output. All dependencies will be /// linked when producing the final output (instead of the intermediate rlib version). fn add_upstream_rust_crates<'a>( cmd: &mut dyn Linker, sess: &'a Session, archive_builder_builder: &dyn ArchiveBuilderBuilder, codegen_results: &CodegenResults, crate_type: CrateType, tmpdir: &Path, ) { // All of the heavy lifting has previously been accomplished by the // dependency_format module of the compiler. This is just crawling the // output of that module, adding crates as necessary. // // Linking to a rlib involves just passing it to the linker (the linker // will slurp up the object files inside), and linking to a dynamic library // involves just passing the right -l flag. let (_, data) = codegen_results .crate_info .dependency_formats .iter() .find(|(ty, _)| *ty == crate_type) .expect("failed to find crate type in dependency format list"); // Invoke get_used_crates to ensure that we get a topological sorting of // crates. let deps = &codegen_results.crate_info.used_crates; let mut compiler_builtins = None; let search_path = OnceCell::new(); for &cnum in deps.iter() { // We may not pass all crates through to the linker. Some crates may // appear statically in an existing dylib, meaning we'll pick up all the // symbols from the dylib. let src = &codegen_results.crate_info.used_crate_source[&cnum]; match data[cnum.as_usize() - 1] { _ if codegen_results.crate_info.profiler_runtime == Some(cnum) => { add_static_crate( cmd, sess, archive_builder_builder, codegen_results, tmpdir, cnum, &Default::default(), ); } // compiler-builtins are always placed last to ensure that they're // linked correctly. _ if codegen_results.crate_info.compiler_builtins == Some(cnum) => { assert!(compiler_builtins.is_none()); compiler_builtins = Some(cnum); } Linkage::NotLinked | Linkage::IncludedFromDylib => {} Linkage::Static => { let bundled_libs = if sess.opts.unstable_opts.packed_bundled_libs { codegen_results.crate_info.native_libraries[&cnum] .iter() .filter_map(|lib| lib.filename) .collect::>() } else { Default::default() }; add_static_crate( cmd, sess, archive_builder_builder, codegen_results, tmpdir, cnum, &bundled_libs, ); // Link static native libs with "-bundle" modifier only if the crate they originate from // is being linked statically to the current crate. If it's linked dynamically // or is an rlib already included via some other dylib crate, the symbols from // native libs will have already been included in that dylib. // // If `-Zlink-native-libraries=false` is set, then the assumption is that an // external build system already has the native dependencies defined, and it // will provide them to the linker itself. if sess.opts.unstable_opts.link_native_libraries { if sess.opts.unstable_opts.packed_bundled_libs { // If rlib contains native libs as archives, unpack them to tmpdir. let rlib = &src.rlib.as_ref().unwrap().0; archive_builder_builder .extract_bundled_libs(rlib, tmpdir, &bundled_libs) .unwrap_or_else(|e| sess.fatal(e)); } let mut last = (None, NativeLibKind::Unspecified, None); for lib in &codegen_results.crate_info.native_libraries[&cnum] { let Some(name) = lib.name else { continue; }; let name = name.as_str(); if !relevant_lib(sess, lib) { continue; } // Skip if this library is the same as the last. last = if (lib.name, lib.kind, lib.verbatim) == last { continue; } else { (lib.name, lib.kind, lib.verbatim) }; match lib.kind { NativeLibKind::Static { bundle: Some(false), whole_archive: Some(true), } => { cmd.link_whole_staticlib( name, lib.verbatim.unwrap_or(false), search_path.get_or_init(|| archive_search_paths(sess)), ); } NativeLibKind::Static { bundle: Some(false), whole_archive: Some(false) | None, } => { // HACK/FIXME: Fixup a circular dependency between libgcc and libc // with glibc. This logic should be moved to the libc crate. if sess.target.os == "linux" && sess.target.env == "gnu" && name == "c" { cmd.link_staticlib("gcc", false); } cmd.link_staticlib(name, lib.verbatim.unwrap_or(false)); } NativeLibKind::LinkArg => { cmd.arg(name); } NativeLibKind::Dylib { .. } | NativeLibKind::Framework { .. } | NativeLibKind::Unspecified | NativeLibKind::RawDylib => {} NativeLibKind::Static { bundle: Some(true) | None, whole_archive } => { if sess.opts.unstable_opts.packed_bundled_libs { // If rlib contains native libs as archives, they are unpacked to tmpdir. let path = tmpdir.join(lib.filename.unwrap().as_str()); if whole_archive == Some(true) { cmd.link_whole_rlib(&path); } else { cmd.link_rlib(&path); } } } } } } } Linkage::Dynamic => add_dynamic_crate(cmd, sess, &src.dylib.as_ref().unwrap().0), } } // compiler-builtins are always placed last to ensure that they're // linked correctly. // We must always link the `compiler_builtins` crate statically. Even if it // was already "included" in a dylib (e.g., `libstd` when `-C prefer-dynamic` // is used) if let Some(cnum) = compiler_builtins { add_static_crate( cmd, sess, archive_builder_builder, codegen_results, tmpdir, cnum, &Default::default(), ); } // Converts a library file-stem into a cc -l argument fn unlib<'a>(target: &Target, stem: &'a str) -> &'a str { if stem.starts_with("lib") && !target.is_like_windows { &stem[3..] } else { stem } } // Adds the static "rlib" versions of all crates to the command line. // There's a bit of magic which happens here specifically related to LTO, // namely that we remove upstream object files. // // When performing LTO, almost(*) all of the bytecode from the upstream // libraries has already been included in our object file output. As a // result we need to remove the object files in the upstream libraries so // the linker doesn't try to include them twice (or whine about duplicate // symbols). We must continue to include the rest of the rlib, however, as // it may contain static native libraries which must be linked in. // // (*) Crates marked with `#![no_builtins]` don't participate in LTO and // their bytecode wasn't included. The object files in those libraries must // still be passed to the linker. // // Note, however, that if we're not doing LTO we can just pass the rlib // blindly to the linker (fast) because it's fine if it's not actually // included as we're at the end of the dependency chain. fn add_static_crate<'a>( cmd: &mut dyn Linker, sess: &'a Session, archive_builder_builder: &dyn ArchiveBuilderBuilder, codegen_results: &CodegenResults, tmpdir: &Path, cnum: CrateNum, bundled_lib_file_names: &FxHashSet, ) { let src = &codegen_results.crate_info.used_crate_source[&cnum]; let cratepath = &src.rlib.as_ref().unwrap().0; let mut link_upstream = |path: &Path| { cmd.link_rlib(&fix_windows_verbatim_for_gcc(path)); }; // See the comment above in `link_staticlib` and `link_rlib` for why if // there's a static library that's not relevant we skip all object // files. let native_libs = &codegen_results.crate_info.native_libraries[&cnum]; let skip_native = native_libs.iter().any(|lib| { matches!(lib.kind, NativeLibKind::Static { bundle: None | Some(true), .. }) && !relevant_lib(sess, lib) }); if (!are_upstream_rust_objects_already_included(sess) || ignored_for_lto(sess, &codegen_results.crate_info, cnum)) && !skip_native { link_upstream(cratepath); return; } let dst = tmpdir.join(cratepath.file_name().unwrap()); let name = cratepath.file_name().unwrap().to_str().unwrap(); let name = &name[3..name.len() - 5]; // chop off lib/.rlib let bundled_lib_file_names = bundled_lib_file_names.clone(); sess.prof.generic_activity_with_arg("link_altering_rlib", name).run(|| { let canonical_name = name.replace('-', "_"); let upstream_rust_objects_already_included = are_upstream_rust_objects_already_included(sess); let is_builtins = sess.target.no_builtins || !codegen_results.crate_info.is_no_builtins.contains(&cnum); let mut archive = archive_builder_builder.new_archive_builder(sess); if let Err(e) = archive.add_archive( cratepath, Box::new(move |f| { if f == METADATA_FILENAME { return true; } let canonical = f.replace('-', "_"); let is_rust_object = canonical.starts_with(&canonical_name) && looks_like_rust_object_file(&f); // If we've been requested to skip all native object files // (those not generated by the rust compiler) then we can skip // this file. See above for why we may want to do this. let skip_because_cfg_say_so = skip_native && !is_rust_object; // If we're performing LTO and this is a rust-generated object // file, then we don't need the object file as it's part of the // LTO module. Note that `#![no_builtins]` is excluded from LTO, // though, so we let that object file slide. let skip_because_lto = upstream_rust_objects_already_included && is_rust_object && is_builtins; // We skip native libraries because: // 1. This native libraries won't be used from the generated rlib, // so we can throw them away to avoid the copying work. // 2. We can't allow it to be a single remaining entry in archive // as some linkers may complain on that. if bundled_lib_file_names.contains(&Symbol::intern(f)) { return true; } if skip_because_cfg_say_so || skip_because_lto { return true; } false }), ) { sess.fatal(&format!("failed to build archive from rlib: {}", e)); } if archive.build(&dst) { link_upstream(&dst); } }); } // Same thing as above, but for dynamic crates instead of static crates. fn add_dynamic_crate(cmd: &mut dyn Linker, sess: &Session, cratepath: &Path) { // Just need to tell the linker about where the library lives and // what its name is let parent = cratepath.parent(); if let Some(dir) = parent { cmd.include_path(&fix_windows_verbatim_for_gcc(dir)); } let filestem = cratepath.file_stem().unwrap().to_str().unwrap(); cmd.link_rust_dylib( &unlib(&sess.target, filestem), parent.unwrap_or_else(|| Path::new("")), ); } } /// Link in all of our upstream crates' native dependencies. Remember that all of these upstream /// native dependencies are all non-static dependencies. We've got two cases then: /// /// 1. The upstream crate is an rlib. In this case we *must* link in the native dependency because /// the rlib is just an archive. /// /// 2. The upstream crate is a dylib. In order to use the dylib, we have to have the dependency /// present on the system somewhere. Thus, we don't gain a whole lot from not linking in the /// dynamic dependency to this crate as well. /// /// The use case for this is a little subtle. In theory the native dependencies of a crate are /// purely an implementation detail of the crate itself, but the problem arises with generic and /// inlined functions. If a generic function calls a native function, then the generic function /// must be instantiated in the target crate, meaning that the native symbol must also be resolved /// in the target crate. fn add_upstream_native_libraries( cmd: &mut dyn Linker, sess: &Session, codegen_results: &CodegenResults, ) { let mut last = (None, NativeLibKind::Unspecified, None); for &cnum in &codegen_results.crate_info.used_crates { for lib in codegen_results.crate_info.native_libraries[&cnum].iter() { let Some(name) = lib.name else { continue; }; let name = name.as_str(); if !relevant_lib(sess, &lib) { continue; } // Skip if this library is the same as the last. last = if (lib.name, lib.kind, lib.verbatim) == last { continue; } else { (lib.name, lib.kind, lib.verbatim) }; let verbatim = lib.verbatim.unwrap_or(false); match lib.kind { NativeLibKind::Dylib { as_needed } => { cmd.link_dylib(name, verbatim, as_needed.unwrap_or(true)) } NativeLibKind::Unspecified => cmd.link_dylib(name, verbatim, true), NativeLibKind::Framework { as_needed } => { cmd.link_framework(name, as_needed.unwrap_or(true)) } // ignore static native libraries here as we've // already included them in add_local_native_libraries and // add_upstream_rust_crates NativeLibKind::Static { .. } => {} NativeLibKind::RawDylib | NativeLibKind::LinkArg => {} } } } } fn relevant_lib(sess: &Session, lib: &NativeLib) -> bool { match lib.cfg { Some(ref cfg) => rustc_attr::cfg_matches(cfg, &sess.parse_sess, CRATE_NODE_ID, None), None => true, } } pub(crate) fn are_upstream_rust_objects_already_included(sess: &Session) -> bool { match sess.lto() { config::Lto::Fat => true, config::Lto::Thin => { // If we defer LTO to the linker, we haven't run LTO ourselves, so // any upstream object files have not been copied yet. !sess.opts.cg.linker_plugin_lto.enabled() } config::Lto::No | config::Lto::ThinLocal => false, } } fn add_apple_sdk(cmd: &mut dyn Linker, sess: &Session, flavor: LinkerFlavor) { let arch = &sess.target.arch; let os = &sess.target.os; let llvm_target = &sess.target.llvm_target; if sess.target.vendor != "apple" || !matches!(os.as_ref(), "ios" | "tvos" | "watchos" | "macos") || !matches!(flavor, LinkerFlavor::Darwin(..)) { return; } if os == "macos" && !matches!(flavor, LinkerFlavor::Darwin(Cc::No, _)) { return; } let sdk_name = match (arch.as_ref(), os.as_ref()) { ("aarch64", "tvos") => "appletvos", ("x86_64", "tvos") => "appletvsimulator", ("arm", "ios") => "iphoneos", ("aarch64", "ios") if llvm_target.contains("macabi") => "macosx", ("aarch64", "ios") if llvm_target.ends_with("-simulator") => "iphonesimulator", ("aarch64", "ios") => "iphoneos", ("x86", "ios") => "iphonesimulator", ("x86_64", "ios") if llvm_target.contains("macabi") => "macosx", ("x86_64", "ios") => "iphonesimulator", ("x86_64", "watchos") => "watchsimulator", ("arm64_32", "watchos") => "watchos", ("aarch64", "watchos") if llvm_target.ends_with("-simulator") => "watchsimulator", ("aarch64", "watchos") => "watchos", ("arm", "watchos") => "watchos", (_, "macos") => "macosx", _ => { sess.err(&format!("unsupported arch `{}` for os `{}`", arch, os)); return; } }; let sdk_root = match get_apple_sdk_root(sdk_name) { Ok(s) => s, Err(e) => { sess.err(&e); return; } }; match flavor { LinkerFlavor::Darwin(Cc::Yes, _) => { cmd.args(&["-isysroot", &sdk_root, "-Wl,-syslibroot", &sdk_root]); } LinkerFlavor::Darwin(Cc::No, _) => { cmd.args(&["-syslibroot", &sdk_root]); } _ => unreachable!(), } } fn get_apple_sdk_root(sdk_name: &str) -> Result { // Following what clang does // (https://github.com/llvm/llvm-project/blob/ // 296a80102a9b72c3eda80558fb78a3ed8849b341/clang/lib/Driver/ToolChains/Darwin.cpp#L1661-L1678) // to allow the SDK path to be set. (For clang, xcrun sets // SDKROOT; for rustc, the user or build system can set it, or we // can fall back to checking for xcrun on PATH.) if let Ok(sdkroot) = env::var("SDKROOT") { let p = Path::new(&sdkroot); match sdk_name { // Ignore `SDKROOT` if it's clearly set for the wrong platform. "appletvos" if sdkroot.contains("TVSimulator.platform") || sdkroot.contains("MacOSX.platform") => {} "appletvsimulator" if sdkroot.contains("TVOS.platform") || sdkroot.contains("MacOSX.platform") => {} "iphoneos" if sdkroot.contains("iPhoneSimulator.platform") || sdkroot.contains("MacOSX.platform") => {} "iphonesimulator" if sdkroot.contains("iPhoneOS.platform") || sdkroot.contains("MacOSX.platform") => { } "macosx10.15" if sdkroot.contains("iPhoneOS.platform") || sdkroot.contains("iPhoneSimulator.platform") => {} "watchos" if sdkroot.contains("WatchSimulator.platform") || sdkroot.contains("MacOSX.platform") => {} "watchsimulator" if sdkroot.contains("WatchOS.platform") || sdkroot.contains("MacOSX.platform") => {} // Ignore `SDKROOT` if it's not a valid path. _ if !p.is_absolute() || p == Path::new("/") || !p.exists() => {} _ => return Ok(sdkroot), } } let res = Command::new("xcrun").arg("--show-sdk-path").arg("-sdk").arg(sdk_name).output().and_then( |output| { if output.status.success() { Ok(String::from_utf8(output.stdout).unwrap()) } else { let error = String::from_utf8(output.stderr); let error = format!("process exit with error: {}", error.unwrap()); Err(io::Error::new(io::ErrorKind::Other, &error[..])) } }, ); match res { Ok(output) => Ok(output.trim().to_string()), Err(e) => Err(format!("failed to get {} SDK path: {}", sdk_name, e)), } } fn add_gcc_ld_path(cmd: &mut dyn Linker, sess: &Session, flavor: LinkerFlavor) { if let Some(ld_impl) = sess.opts.unstable_opts.gcc_ld { if let LinkerFlavor::Gnu(Cc::Yes, _) | LinkerFlavor::Darwin(Cc::Yes, _) | LinkerFlavor::WasmLld(Cc::Yes) = flavor { match ld_impl { LdImpl::Lld => { // Implement the "self-contained" part of -Zgcc-ld // by adding rustc distribution directories to the tool search path. for path in sess.get_tools_search_paths(false) { cmd.arg({ let mut arg = OsString::from("-B"); arg.push(path.join("gcc-ld")); arg }); } // Implement the "linker flavor" part of -Zgcc-ld // by asking cc to use some kind of lld. cmd.arg("-fuse-ld=lld"); if !flavor.is_gnu() { // Tell clang to use a non-default LLD flavor. // Gcc doesn't understand the target option, but we currently assume // that gcc is not used for Apple and Wasm targets (#97402). cmd.arg(format!("--target={}", sess.target.llvm_target)); } } } } else { sess.fatal("option `-Z gcc-ld` is used even though linker flavor is not gcc"); } } }