diff options
Diffstat (limited to 'compiler/rustc_codegen_ssa/src/back/link.rs')
| -rw-r--r-- | compiler/rustc_codegen_ssa/src/back/link.rs | 2800 |
1 files changed, 2800 insertions, 0 deletions
diff --git a/compiler/rustc_codegen_ssa/src/back/link.rs b/compiler/rustc_codegen_ssa/src/back/link.rs new file mode 100644 index 000000000..63207803e --- /dev/null +++ b/compiler/rustc_codegen_ssa/src/back/link.rs @@ -0,0 +1,2800 @@ +use rustc_arena::TypedArena; +use rustc_ast::CRATE_NODE_ID; +use rustc_data_structures::fx::{FxHashSet, 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::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, 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, CrtObjectsFallback}; +use rustc_target::spec::{LinkOutputKind, LinkerFlavor, LldFlavor, SplitDebuginfo}; +use rustc_target::spec::{PanicStrategy, RelocModel, RelroLevel, SanitizerSet, Target}; + +use super::archive::{find_library, 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::{looks_like_rust_object_file, CodegenResults, CompiledModule, CrateInfo, NativeLib}; + +use cc::windows_registry; +use regex::Regex; +use tempfile::Builder as TempFileBuilder; + +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::{ascii, char, 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(|err| sess.fatal(&format!("couldn't create a temp dir: {}", err))); + 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( + info: &CrateInfo, + f: &mut dyn FnMut(CrateNum, &Path), +) -> Result<(), String> { + let crates = info.used_crates.iter(); + let mut fmts = None; + for (ty, list) in info.dependency_formats.iter() { + match ty { + CrateType::Executable + | CrateType::Staticlib + | CrateType::Cdylib + | CrateType::ProcMacro => { + fmts = Some(list); + break; + } + _ => {} + } + } + let Some(fmts) = fmts else { + return Err("could not find formats for rlibs".to_string()); + }; + for &cnum in crates { + match fmts.get(cnum.as_usize() - 1) { + Some(&Linkage::NotLinked | &Linkage::IncludedFromDylib) => continue, + Some(_) => {} + None => return Err("could not find formats for rlibs".to_string()), + } + let 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(format!( + "could not find rlib for: `{}`, found rmeta (metadata) file", + name + )); + } else { + return Err(format!("could not find rlib for: `{}`", 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<Box<dyn ArchiveBuilder<'a> + '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); + } + } + } + + // 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 => + { + // 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.err( + "the linking modifiers `+bundle` and `+whole-archive` are not compatible \ + with each other when generating rlibs", + ); + } + 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_library(name.as_str(), lib.verbatim.unwrap_or(false), &lib_search_paths, sess); + ab.add_archive(&location, Box::new(|_| false)).unwrap_or_else(|e| { + sess.fatal(&format!( + "failed to add native library {}: {}", + location.to_string_lossy(), + e + )); + }); + } + } + + for (raw_dylib_name, raw_dylib_imports) in + collate_raw_dylibs(sess, &codegen_results.crate_info.used_libraries)? + { + let output_path = archive_builder_builder.create_dll_import_lib( + sess, + &raw_dylib_name, + &raw_dylib_imports, + tmpdir.as_ref(), + ); + + ab.add_archive(&output_path, Box::new(|_| false)).unwrap_or_else(|e| { + sess.fatal(&format!("failed to add native library {}: {}", output_path.display(), e)); + }); + } + + 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); + } + + 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( + sess: &Session, + used_libraries: &[NativeLib], +) -> Result<Vec<(String, Vec<DllImport>)>, ErrorGuaranteed> { + // Use index maps to preserve original order of imports and libraries. + let mut dylib_table = FxIndexMap::<String, FxIndexMap<Symbol, &DllImport>>::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.span_err( + import.span, + &format!( + "multiple declarations of external function `{}` from \ + library `{}` have different calling conventions", + import.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(&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.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(()) +} + +fn escape_stdout_stderr_string(s: &[u8]) -> String { + str::from_utf8(s).map(|s| s.to_owned()).unwrap_or_else(|_| { + let mut x = "Non-UTF-8 output: ".to_string(); + x.extend(s.iter().flat_map(|&b| ascii::escape_default(b)).map(char::from)); + x + }) +} + +/// 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<Relocations> { + arena_data: TypedArena<Vec<u8>>, + arena_mmap: TypedArena<Mmap>, + arena_relocations: TypedArena<Relocations>, + } + + impl<Relocations> ThorinSession<Relocations> { + fn alloc_mmap<'arena>(&'arena self, data: Mmap) -> &'arena Mmap { + (*self.arena_mmap.alloc(data)).borrow() + } + } + + impl<Relocations> thorin::Session<Relocations> for ThorinSession<Relocations> { + fn alloc_data<'arena>(&'arena self, data: Vec<u8>) -> &'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.struct_err("linking dwarf objects with thorin failed") + .note(&format!("{:?}", e)) + .emit(); + 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 sess.target.linker_is_gnu + && flavor != LinkerFlavor::Ld + && 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 sess.target.linker_is_gnu + && flavor != LinkerFlavor::Ld + && 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 = crt_objects_fallback(sess, crate_type); + let opts = &sess.target; + let pre_objects = if self_contained { + &opts.pre_link_objects_fallback + } else { + &opts.pre_link_objects + }; + let post_objects = if self_contained { + &opts.post_link_objects_fallback + } 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::<Vec<_>>() + }; + 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_stdout_stderr_string(&output); + let mut err = sess.struct_err(&format!( + "linking with `{}` failed: {}", + linker_path.display(), + prog.status + )); + err.note(&format!("{:?}", &cmd)).note(&escaped_output); + if escaped_output.contains("undefined reference to") { + err.help( + "some `extern` functions couldn't be found; some native libraries may \ + need to be installed or have their path specified", + ); + err.note("use the `-l` flag to specify native libraries to link"); + err.note("use the `cargo:rustc-link-lib` directive to specify the native \ + libraries to link with Cargo (see https://doc.rust-lang.org/cargo/reference/build-scripts.html#cargorustc-link-libkindname)"); + } + err.emit(); + + // 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 + // 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_stdout_stderr_string(&prog.stderr)); + info!("linker stdout:\n{}", escape_stdout_stderr_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 VS 2013, VS 2015, VS 2017, VS 2019 or VS 2022 \ + was installed with the Visual C++ option", + ); + } + 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_in_osx(sess, &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_in_osx(sess, &out_filename, Some("-x")) + } + (Strip::Symbols, _) => strip_symbols_in_osx(sess, &out_filename, None), + (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_in_osx<'a>(sess: &'a Session, out_filename: &Path, option: Option<&str>) { + let mut cmd = Command::new("strip"); + 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 `strip` failed: {}", + prog.status + )) + .note(&escape_string(&output)) + .emit(); + } + } + Err(e) => sess.fatal(&format!("unable to run `strip`: {}", e)), + } +} + +fn escape_string(s: &[u8]) -> String { + str::from_utf8(s).map(|s| s.to_owned()).unwrap_or_else(|_| { + let mut x = "Non-UTF-8 output: ".to_string(); + x.extend(s.iter().flat_map(|&b| ascii::escape_default(b)).map(char::from)); + x + }) +} + +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 = 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<PathBuf>, + flavor: Option<LinkerFlavor>, + ) -> 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::Em => { + if cfg!(windows) { + "emcc.bat" + } else { + "emcc" + } + } + LinkerFlavor::Gcc => { + 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::Ld => "ld", + LinkerFlavor::Msvc => "link.exe", + LinkerFlavor::Lld(_) => "lld", + LinkerFlavor::PtxLinker => "rust-ptx-linker", + LinkerFlavor::BpfLinker => "bpf-linker", + LinkerFlavor::L4Bender => "l4-bender", + }), + 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::Em + } else if stem == "gcc" + || stem.ends_with("-gcc") + || stem == "clang" + || stem.ends_with("-clang") + { + LinkerFlavor::Gcc + } else if stem == "wasm-ld" || stem.ends_with("-wasm-ld") { + LinkerFlavor::Lld(LldFlavor::Wasm) + } else if stem == "ld" || stem == "ld.lld" || stem.ends_with("-ld") { + LinkerFlavor::Ld + } else if stem == "link" || stem == "lld-link" { + LinkerFlavor::Msvc + } else if stem == "lld" || stem == "rust-lld" { + LinkerFlavor::Lld(sess.target.lld_flavor) + } 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 + if let Some(ret) = infer_from(sess, sess.opts.cg.linker.clone(), sess.opts.cg.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<PathBuf> { + 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_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<Output> { + // 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<Output>, _: &Path) -> io::Result<()> { + Ok(()) + } + + #[cfg(windows)] + fn flush_linked_file( + command_output: &io::Result<Output>, + 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 +} + +/// Whether we link to our own CRT objects instead of relying on gcc to pull them. +/// We only provide such support for a very limited number of targets. +fn crt_objects_fallback(sess: &Session, crate_type: CrateType) -> bool { + if let Some(self_contained) = sess.opts.cg.link_self_contained { + return self_contained; + } + + match sess.target.crt_objects_fallback { + // 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). + Some(CrtObjectsFallback::Musl) => sess.crt_static(Some(crate_type)), + Some(CrtObjectsFallback::Mingw) => { + sess.host == sess.target + && sess.target.vendor != "uwp" + && detect_self_contained_mingw(&sess) + } + // FIXME: Figure out cases in which WASM needs to link with a native toolchain. + Some(CrtObjectsFallback::Wasm) => true, + None => false, + } +} + +/// Add pre-link object files defined by the target spec. +fn add_pre_link_objects( + cmd: &mut dyn Linker, + sess: &Session, + link_output_kind: LinkOutputKind, + self_contained: bool, +) { + let opts = &sess.target; + let objects = + if self_contained { &opts.pre_link_objects_fallback } else { &opts.pre_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 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 opts = &sess.target; + let objects = + if self_contained { &opts.post_link_objects_fallback } else { &opts.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_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. +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::<Vec<_>>(); + 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_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<Command, ErrorGuaranteed> { + let crt_objects_fallback = crt_objects_fallback(sess, crate_type); + let cmd = &mut *super::linker::get_linker( + sess, + path, + flavor, + crt_objects_fallback, + &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, link_output_kind, crt_objects_fallback); + + 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. + // (The current implementation still doesn't prevent it though, see the FIXME below.) + // + // 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(); + + // FIXME: Move this below to other native libraries + // (or alternatively link all native libraries after their respective crates). + // This change is somewhat breaking in practice due to local static libraries being linked + // as whole-archive (#85144), so removing whole-archive may be a pre-requisite. + if sess.opts.unstable_opts.link_native_libraries { + add_local_native_libraries(cmd, sess, codegen_results); + } + + // Upstream rust libraries and their non-bundled static libraries + add_upstream_rust_crates( + cmd, + sess, + archive_builder_builder, + codegen_results, + crate_type, + tmpdir, + ); + + // Upstream dynamic native libraries linked with `#[link]` attributes at and `-l` + // command line options. + // 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_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)? + { + cmd.add_object(&archive_builder_builder.create_dll_import_lib( + sess, + &raw_dylib_name, + &raw_dylib_imports, + tmpdir, + )); + } + + // 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, + crt_objects_fallback, + 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, crt_objects_fallback); + + // ------------ 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, + crt_objects_fallback: 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 { + 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 crt_objects_fallback { + 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::PtxLinker { + // 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::BpfLinker { + 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, crt_objects_fallback); + + 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<DebuggerVisualizerFile>, +) -> Vec<PathBuf> { + 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; + + // 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 in all situations we'll need to be + // sure to correctly apply the `--start-group` and `--end-group` options to + // GNU linkers, otherwise if we don't use any other symbol from the standard + // library it'll get discarded and the whole application won't link. + // + // In this loop we're calculating the `group_end`, after which crate to + // pass `--end-group` and `group_start`, before which crate to pass + // `--start-group`. We currently do this by passing `--end-group` after + // the first crate (when iterating backwards) that requires a lang item + // defined somewhere else. Once that's set then when we've defined all the + // necessary lang items we'll pass `--start-group`. + // + // Note that this isn't amazing logic for now but it should do the trick + // for the current implementation of the standard library. + let mut group_end = None; + let mut group_start = None; + // Crates available for linking thus far. + let mut available = FxHashSet::default(); + // Crates required to satisfy dependencies discovered so far. + let mut required = FxHashSet::default(); + + let info = &codegen_results.crate_info; + for &cnum in deps.iter().rev() { + if let Some(missing) = info.missing_lang_items.get(&cnum) { + let missing_crates = missing.iter().map(|i| info.lang_item_to_crate.get(i).copied()); + required.extend(missing_crates); + } + + required.insert(Some(cnum)); + available.insert(Some(cnum)); + + if required.len() > available.len() && group_end.is_none() { + group_end = Some(cnum); + } + if required.len() == available.len() && group_end.is_some() { + group_start = Some(cnum); + break; + } + } + + // If we didn't end up filling in all lang items from upstream crates then + // we'll be filling it in with our crate. This probably means we're the + // standard library itself, so skip this for now. + if group_end.is_some() && group_start.is_none() { + group_end = None; + } + + let mut compiler_builtins = None; + let search_path = OnceCell::new(); + + for &cnum in deps.iter() { + if group_start == Some(cnum) { + cmd.group_start(); + } + + // 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); + } + // 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 => { + add_static_crate(cmd, sess, archive_builder_builder, codegen_results, tmpdir, cnum); + + // 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 { + 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, + } => { + 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: _, + } => {} + } + } + } + } + Linkage::Dynamic => add_dynamic_crate(cmd, sess, &src.dylib.as_ref().unwrap().0), + } + + if group_end == Some(cnum) { + cmd.group_end(); + } + } + + // 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); + } + + // 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, + ) { + 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 + + 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; + + 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, + } +} + +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") + || (flavor != LinkerFlavor::Gcc && flavor != LinkerFlavor::Lld(LldFlavor::Ld64)) + { + 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", + _ => { + 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::Gcc => { + cmd.args(&["-isysroot", &sdk_root, "-Wl,-syslibroot", &sdk_root]); + } + LinkerFlavor::Lld(LldFlavor::Ld64) => { + cmd.args(&["-syslibroot", &sdk_root]); + } + _ => unreachable!(), + } +} + +fn get_apple_sdk_root(sdk_name: &str) -> Result<String, String> { + // 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::Gcc = flavor { + match ld_impl { + LdImpl::Lld => { + let tools_path = sess.get_tools_search_paths(false); + let gcc_ld_dir = tools_path + .into_iter() + .map(|p| p.join("gcc-ld")) + .find(|p| { + p.join(if sess.host.is_like_windows { "ld.exe" } else { "ld" }).exists() + }) + .unwrap_or_else(|| sess.fatal("rust-lld (as ld) not found")); + cmd.arg({ + let mut arg = OsString::from("-B"); + arg.push(gcc_ld_dir); + arg + }); + cmd.arg(format!("-Wl,-rustc-lld-flavor={}", sess.target.lld_flavor.as_str())); + } + } + } else { + sess.fatal("option `-Z gcc-ld` is used even though linker flavor is not gcc"); + } + } +} |