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fuchsia / third_party / rust / 7e4379c4eb25a423b8484d99b01bfc8f5bb7efd8 / . / compiler / rustc_codegen_ssa / src / back / link.rs
blob: 1d05c4eee4d15b239f7565975ccb06768a4af94e [file] [log] [blame]
mod raw_dylib;
use std::collections::BTreeSet;
use std::ffi::OsString;
use std::fs::{File, OpenOptions, read};
use std::io::{BufWriter, Write};
use std::ops::{ControlFlow, Deref};
use std::path::{Path, PathBuf};
use std::process::{ExitStatus, Output, Stdio};
use std::{env, fmt, fs, io, mem, str};
use cc::windows_registry;
use itertools::Itertools;
use regex::Regex;
use rustc_arena::TypedArena;
use rustc_ast::CRATE_NODE_ID;
use rustc_data_structures::fx::FxIndexSet;
use rustc_data_structures::memmap::Mmap;
use rustc_data_structures::temp_dir::MaybeTempDir;
use rustc_errors::{DiagCtxtHandle, LintDiagnostic};
use rustc_fs_util::{fix_windows_verbatim_for_gcc, try_canonicalize};
use rustc_hir::def_id::{CrateNum, LOCAL_CRATE};
use rustc_macros::LintDiagnostic;
use rustc_metadata::fs::{METADATA_FILENAME, copy_to_stdout, emit_wrapper_file};
use rustc_metadata::{
NativeLibSearchFallback, find_native_static_library, walk_native_lib_search_dirs,
};
use rustc_middle::bug;
use rustc_middle::lint::lint_level;
use rustc_middle::middle::debugger_visualizer::DebuggerVisualizerFile;
use rustc_middle::middle::dependency_format::Linkage;
use rustc_middle::middle::exported_symbols::SymbolExportKind;
use rustc_session::config::{
self, CFGuard, CrateType, DebugInfo, LinkerFeaturesCli, OutFileName, OutputFilenames,
OutputType, PrintKind, SplitDwarfKind, Strip,
};
use rustc_session::lint::builtin::LINKER_MESSAGES;
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::{Session, filesearch};
use rustc_span::Symbol;
use rustc_target::spec::crt_objects::CrtObjects;
use rustc_target::spec::{
BinaryFormat, Cc, LinkOutputKind, LinkSelfContainedComponents, LinkSelfContainedDefault,
LinkerFeatures, LinkerFlavor, LinkerFlavorCli, Lld, PanicStrategy, RelocModel, RelroLevel,
SanitizerSet, SplitDebuginfo,
};
use tempfile::Builder as TempFileBuilder;
use tracing::{debug, info, warn};
use super::archive::{ArchiveBuilder, ArchiveBuilderBuilder};
use super::command::Command;
use super::linker::{self, Linker};
use super::metadata::{MetadataPosition, create_wrapper_file};
use super::rpath::{self, RPathConfig};
use super::{apple, versioned_llvm_target};
use crate::{
CodegenResults, CompiledModule, CrateInfo, NativeLib, errors, looks_like_rust_object_file,
};
pub fn ensure_removed(dcx: DiagCtxtHandle<'_>, path: &Path) {
if let Err(e) = fs::remove_file(path) {
if e.kind() != io::ErrorKind::NotFound {
dcx.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(
sess: &Session,
archive_builder_builder: &dyn ArchiveBuilderBuilder,
codegen_results: CodegenResults,
outputs: &OutputFilenames,
) {
let _timer = sess.timer("link_binary");
let output_metadata = sess.opts.output_types.contains_key(&OutputType::Metadata);
let mut tempfiles_for_stdout_output: Vec<PathBuf> = Vec::new();
for &crate_type in &codegen_results.crate_info.crate_types {
// 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 `{}`", crate_type, sess.opts.target_triple);
}
sess.time("link_binary_check_files_are_writeable", || {
for obj in codegen_results.modules.iter().filter_map(|m| m.object.as_ref()) {
check_file_is_writeable(obj, sess);
}
});
if outputs.outputs.should_link() {
let tmpdir = TempFileBuilder::new()
.prefix("rustc")
.tempdir()
.unwrap_or_else(|error| sess.dcx().emit_fatal(errors::CreateTempDir { error }));
let path = MaybeTempDir::new(tmpdir, sess.opts.cg.save_temps);
let output = out_filename(
sess,
crate_type,
outputs,
codegen_results.crate_info.local_crate_name,
);
let crate_name = format!("{}", codegen_results.crate_info.local_crate_name);
let out_filename =
output.file_for_writing(outputs, OutputType::Exe, Some(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.dcx().emit_artifact_notification(&out_filename, "link");
}
if sess.prof.enabled()
&& 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,
);
}
if output.is_stdout() {
if output.is_tty() {
sess.dcx().emit_err(errors::BinaryOutputToTty {
shorthand: OutputType::Exe.shorthand(),
});
} else if let Err(e) = copy_to_stdout(&out_filename) {
sess.dcx().emit_err(errors::CopyPath::new(&out_filename, output.as_path(), e));
}
tempfiles_for_stdout_output.push(out_filename);
}
}
}
// 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 && let Some(ref obj) = module.object {
ensure_removed(sess.dcx(), obj);
}
if !preserve_dwarf_objects && let Some(ref dwo_obj) = module.dwarf_object {
ensure_removed(sess.dcx(), 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);
}
// Remove the temporary files if output goes to stdout
for temp in tempfiles_for_stdout_output {
ensure_removed(sess.dcx(), &temp);
}
// 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);
}
});
}
// Crate type is not passed when calculating the dylibs to include for LTO. In that case all
// crate types must use the same dependency formats.
pub fn each_linked_rlib(
info: &CrateInfo,
crate_type: Option<CrateType>,
f: &mut dyn FnMut(CrateNum, &Path),
) -> Result<(), errors::LinkRlibError> {
let fmts = if let Some(crate_type) = crate_type {
let Some(fmts) = info.dependency_formats.get(&crate_type) else {
return Err(errors::LinkRlibError::MissingFormat);
};
fmts
} else {
let mut dep_formats = info.dependency_formats.iter();
let (ty1, list1) = dep_formats.next().ok_or(errors::LinkRlibError::MissingFormat)?;
if let Some((ty2, list2)) = dep_formats.find(|(_, list2)| list1 != *list2) {
return Err(errors::LinkRlibError::IncompatibleDependencyFormats {
ty1: format!("{ty1:?}"),
ty2: format!("{ty2:?}"),
list1: format!("{list1:?}"),
list2: format!("{list2:?}"),
});
}
list1
};
let used_dep_crates = info.used_crates.iter();
for &cnum in used_dep_crates {
match fmts.get(cnum) {
Some(&Linkage::NotLinked | &Linkage::Dynamic | &Linkage::IncludedFromDylib) => continue,
Some(_) => {}
None => return Err(errors::LinkRlibError::MissingFormat),
}
let crate_name = info.crate_name[&cnum];
let used_crate_source = &info.used_crate_source[&cnum];
if let Some((path, _)) = &used_crate_source.rlib {
f(cnum, path);
} else if used_crate_source.rmeta.is_some() {
return Err(errors::LinkRlibError::OnlyRmetaFound { crate_name });
} else {
return Err(errors::LinkRlibError::NotFound { crate_name });
}
}
Ok(())
}
/// Create an 'rlib'.
///
/// An rlib in its current incarnation is essentially a renamed .a file (with "dummy" object files).
/// The rlib primarily contains the object file of the crate, but it also some of the object files
/// from native libraries.
fn link_rlib<'a>(
sess: &'a Session,
archive_builder_builder: &dyn ArchiveBuilderBuilder,
codegen_results: &CodegenResults,
flavor: RlibFlavor,
tmpdir: &MaybeTempDir,
) -> Box<dyn ArchiveBuilder + 'a> {
let mut ab = archive_builder_builder.new_archive_builder(sess);
let trailing_metadata = match flavor {
RlibFlavor::Normal => {
let (metadata, metadata_position) = create_wrapper_file(
sess,
".rmeta".to_string(),
codegen_results.metadata.stub_or_full(),
);
let metadata = emit_wrapper_file(sess, &metadata, tmpdir, METADATA_FILENAME);
match metadata_position {
MetadataPosition::First => {
// Most of the time metadata in rlib files is wrapped in a "dummy" object
// file for the target platform so the rlib can be processed entirely by
// normal linkers for the platform. Sometimes this is not possible however.
// If it is possible however, placing the metadata object first improves
// performance of getting metadata from rlibs.
ab.add_file(&metadata);
None
}
MetadataPosition::Last => Some(metadata),
}
}
RlibFlavor::StaticlibBase => None,
};
for m in &codegen_results.modules {
if let Some(obj) = m.object.as_ref() {
ab.add_file(obj);
}
if let Some(dwarf_obj) = m.dwarf_object.as_ref() {
ab.add_file(dwarf_obj);
}
}
match flavor {
RlibFlavor::Normal => {}
RlibFlavor::StaticlibBase => {
let obj = codegen_results.allocator_module.as_ref().and_then(|m| m.object.as_ref());
if let Some(obj) = obj {
ab.add_file(obj);
}
}
}
// Used if packed_bundled_libs flag enabled.
let mut packed_bundled_libs = Vec::new();
// Note that in this loop we are ignoring the value of `lib.cfg`. That is,
// we may not be configured to actually include a static library if we're
// adding it here. That's because later when we consume this rlib we'll
// decide whether we actually needed the static library or not.
//
// To do this "correctly" we'd need to keep track of which libraries added
// which object files to the archive. We don't do that here, however. The
// #[link(cfg(..))] feature is unstable, though, and only intended to get
// liblibc working. In that sense the check below just indicates that if
// there are any libraries we want to omit object files for at link time we
// just exclude all custom object files.
//
// Eventually if we want to stabilize or flesh out the #[link(cfg(..))]
// feature then we'll need to figure out how to record what objects were
// loaded from the libraries found here and then encode that into the
// metadata of the rlib we're generating somehow.
for lib in codegen_results.crate_info.used_libraries.iter() {
let NativeLibKind::Static { bundle: None | Some(true), .. } = lib.kind else {
continue;
};
if flavor == RlibFlavor::Normal
&& let Some(filename) = lib.filename
{
let path = find_native_static_library(filename.as_str(), true, sess);
let src = read(path)
.unwrap_or_else(|e| sess.dcx().emit_fatal(errors::ReadFileError { message: e }));
let (data, _) = create_wrapper_file(sess, ".bundled_lib".to_string(), &src);
let wrapper_file = emit_wrapper_file(sess, &data, tmpdir, filename.as_str());
packed_bundled_libs.push(wrapper_file);
} else {
let path = find_native_static_library(lib.name.as_str(), lib.verbatim, sess);
ab.add_archive(&path, Box::new(|_| false)).unwrap_or_else(|error| {
sess.dcx().emit_fatal(errors::AddNativeLibrary { library_path: path, error })
});
}
}
// On Windows, we add the raw-dylib import libraries to the rlibs already.
// But on ELF, this is not possible, as a shared object cannot be a member of a static library.
// Instead, we add all raw-dylibs to the final link on ELF.
if sess.target.is_like_windows {
for output_path in raw_dylib::create_raw_dylib_dll_import_libs(
sess,
archive_builder_builder,
codegen_results.crate_info.used_libraries.iter(),
tmpdir.as_ref(),
true,
) {
ab.add_archive(&output_path, Box::new(|_| false)).unwrap_or_else(|error| {
sess.dcx()
.emit_fatal(errors::AddNativeLibrary { library_path: output_path, error });
});
}
}
if let Some(trailing_metadata) = trailing_metadata {
// Note that it is important that we add all of our non-object "magical
// files" *after* all of the object files in the archive. The reason for
// this is as follows:
//
// * When performing LTO, this archive will be modified to remove
// objects from above. The reason for this is described below.
//
// * When the system linker looks at an archive, it will attempt to
// determine the architecture of the archive in order to see whether its
// linkable.
//
// The algorithm for this detection is: iterate over the files in the
// archive. Skip magical SYMDEF names. Interpret the first file as an
// object file. Read architecture from the object file.
//
// * As one can probably see, if "metadata" and "foo.bc" were placed
// before all of the objects, then the architecture of this archive would
// not be correctly inferred once 'foo.o' is removed.
//
// * Most of the time metadata in rlib files is wrapped in a "dummy" object
// file for the target platform so the rlib can be processed entirely by
// normal linkers for the platform. Sometimes this is not possible however.
//
// Basically, all this means is that this code should not move above the
// code above.
ab.add_file(&trailing_metadata);
}
// Add all bundled static native library dependencies.
// Archives added to the end of .rlib archive, see comment above for the reason.
for lib in packed_bundled_libs {
ab.add_file(&lib)
}
ab
}
/// 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(
sess: &Session,
archive_builder_builder: &dyn ArchiveBuilderBuilder,
codegen_results: &CodegenResults,
out_filename: &Path,
tempdir: &MaybeTempDir,
) {
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,
Some(CrateType::Staticlib),
&mut |cnum, path| {
let lto = are_upstream_rust_objects_already_included(sess)
&& !ignored_for_lto(sess, &codegen_results.crate_info, cnum);
let native_libs = codegen_results.crate_info.native_libraries[&cnum].iter();
let relevant = native_libs.clone().filter(|lib| relevant_lib(sess, lib));
let relevant_libs: FxIndexSet<_> = relevant.filter_map(|lib| lib.filename).collect();
let bundled_libs: FxIndexSet<_> = native_libs.filter_map(|lib| lib.filename).collect();
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;
}
// Skip objects for bundled libs.
if bundled_libs.contains(&Symbol::intern(fname)) {
return true;
}
false
}),
)
.unwrap();
archive_builder_builder
.extract_bundled_libs(path, tempdir.as_ref(), &relevant_libs)
.unwrap_or_else(|e| sess.dcx().emit_fatal(e));
for filename in relevant_libs.iter() {
let joined = tempdir.as_ref().join(filename.as_str());
let path = joined.as_path();
ab.add_archive(path, Box::new(|_| false)).unwrap();
}
all_native_libs
.extend(codegen_results.crate_info.native_libraries[&cnum].iter().cloned());
},
);
if let Err(e) = res {
sess.dcx().emit_fatal(e);
}
ab.build(out_filename);
let crates = codegen_results.crate_info.used_crates.iter();
let fmts = codegen_results
.crate_info
.dependency_formats
.get(&CrateType::Staticlib)
.expect("no dependency formats for staticlib");
let mut all_rust_dylibs = vec![];
for &cnum in crates {
let Some(Linkage::Dynamic) = fmts.get(cnum) else {
continue;
};
let crate_name = codegen_results.crate_info.crate_name[&cnum];
let used_crate_source = &codegen_results.crate_info.used_crate_source[&cnum];
if let Some((path, _)) = &used_crate_source.dylib {
all_rust_dylibs.push(&**path);
} else if used_crate_source.rmeta.is_some() {
sess.dcx().emit_fatal(errors::LinkRlibError::OnlyRmetaFound { crate_name });
} else {
sess.dcx().emit_fatal(errors::LinkRlibError::NotFound { crate_name });
}
}
all_native_libs.extend_from_slice(&codegen_results.crate_info.used_libraries);
for print in &sess.opts.prints {
if print.kind == PrintKind::NativeStaticLibs {
print_native_static_libs(sess, &print.out, &all_native_libs, &all_rust_dylibs);
}
}
}
/// Use `thorin` (rust implementation of a dwarf packaging utility) to link DWARF objects into a
/// DWARF package.
fn link_dwarf_object(sess: &Session, cg_results: &CodegenResults, executable_out_filename: &Path) {
let mut dwp_out_filename = executable_out_filename.to_path_buf().into_os_string();
dwp_out_filename.push(".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(&self, data: Mmap) -> &Mmap {
&*self.arena_mmap.alloc(data)
}
}
impl<Relocations> thorin::Session<Relocations> for ThorinSession<Relocations> {
fn alloc_data(&self, data: Vec<u8>) -> &[u8] {
&*self.arena_data.alloc(data)
}
fn alloc_relocation(&self, data: Relocations) -> &Relocations {
&*self.arena_relocations.alloc(data)
}
fn read_input(&self, path: &Path) -> std::io::Result<&[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
.items()
.filter_map(|(_, csource)| csource.rlib.as_ref())
.map(|(path, _)| path)
.into_sorted_stable_ord();
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_stream = BufWriter::new(
OpenOptions::new()
.read(true)
.write(true)
.create(true)
.truncate(true)
.open(dwp_out_filename)?,
);
let mut output_stream = thorin::object::write::StreamingBuffer::new(output_stream);
package.finish()?.emit(&mut output_stream)?;
output_stream.result()?;
output_stream.into_inner().flush()?;
Ok(())
}) {
Ok(()) => {}
Err(e) => sess.dcx().emit_fatal(errors::ThorinErrorWrapper(e)),
}
}
#[derive(LintDiagnostic)]
#[diag(codegen_ssa_linker_output)]
/// Translating this is kind of useless. We don't pass translation flags to the linker, so we'd just
/// end up with inconsistent languages within the same diagnostic.
struct LinkerOutput {
inner: String,
}
/// 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(
sess: &Session,
archive_builder_builder: &dyn ArchiveBuilderBuilder,
crate_type: CrateType,
out_filename: &Path,
codegen_results: &CodegenResults,
tmpdir: &Path,
) {
info!("preparing {:?} to {:?}", crate_type, out_filename);
let (linker_path, flavor) = linker_and_flavor(sess);
let self_contained_components = self_contained_components(sess, crate_type, &linker_path);
// On AIX, we ship all libraries as .a big_af archive
// the expected format is lib<name>.a(libname.so) for the actual
// dynamic library. So we link to a temporary .so file to be archived
// at the final out_filename location
let should_archive = crate_type != CrateType::Executable && sess.target.is_like_aix;
let archive_member =
should_archive.then(|| tmpdir.join(out_filename.file_name().unwrap()).with_extension("so"));
let temp_filename = archive_member.as_deref().unwrap_or(out_filename);
let mut cmd = linker_with_args(
&linker_path,
flavor,
sess,
archive_builder_builder,
crate_type,
tmpdir,
temp_filename,
codegen_results,
self_contained_components,
);
linker::disable_localization(&mut cmd);
for (k, 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());
}
for print in &sess.opts.prints {
if print.kind == PrintKind::LinkArgs {
let content = format!("{cmd:?}\n");
print.out.overwrite(&content, sess);
}
}
// May have not found libraries in the right formats.
sess.dcx().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, flavor, tmpdir));
let Ok(ref output) = prog else {
break;
};
if output.status.success() {
break;
}
let mut out = output.stderr.clone();
out.extend(&output.stdout);
let out = String::from_utf8_lossy(&out);
// Check to see if the link failed with an error message that indicates it
// doesn't recognize the -no-pie option. If so, re-perform the link step
// without it. This is safe because if the linker doesn't support -no-pie
// then it should not default to linking executables as pie. Different
// versions of gcc seem to use different quotes in the error message so
// don't check for them.
if matches!(flavor, LinkerFlavor::Gnu(Cc::Yes, _))
&& unknown_arg_regex.is_match(&out)
&& out.contains("-no-pie")
&& cmd.get_args().iter().any(|e| e == "-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 != "-no-pie" {
cmd.arg(arg);
}
}
info!("{cmd:?}");
continue;
}
// Check if linking failed with an error message that indicates the driver didn't recognize
// the `-fuse-ld=lld` option. If so, re-perform the link step without it. This avoids having
// to spawn multiple instances on the happy path to do version checking, and ensures things
// keep working on the tier 1 baseline of GLIBC 2.17+. That is generally understood as GCCs
// circa RHEL/CentOS 7, 4.5 or so, whereas lld support was added in GCC 9.
if matches!(flavor, LinkerFlavor::Gnu(Cc::Yes, Lld::Yes))
&& unknown_arg_regex.is_match(&out)
&& out.contains("-fuse-ld=lld")
&& cmd.get_args().iter().any(|e| e.to_string_lossy() == "-fuse-ld=lld")
{
info!("linker output: {:?}", out);
warn!("The linker driver does not support `-fuse-ld=lld`. Retrying without it.");
for arg in cmd.take_args() {
if arg.to_string_lossy() != "-fuse-ld=lld" {
cmd.arg(arg);
}
}
info!("{cmd:?}");
continue;
}
// Detect '-static-pie' used with an older version of gcc or clang not supporting it.
// Fallback from '-static-pie' to '-static' in that case.
if matches!(flavor, LinkerFlavor::Gnu(Cc::Yes, _))
&& unknown_arg_regex.is_match(&out)
&& (out.contains("-static-pie") || out.contains("--no-dynamic-linker"))
&& cmd.get_args().iter().any(|e| e == "-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 = self_contained_components.is_crt_objects_enabled();
let opts = &sess.target;
let pre_objects = if self_contained_crt_objects {
&opts.pre_link_objects_self_contained
} else {
&opts.pre_link_objects
};
let post_objects = if self_contained_crt_objects {
&opts.post_link_objects_self_contained
} else {
&opts.post_link_objects
};
let get_objects = |objects: &CrtObjects, kind| {
objects
.get(&kind)
.iter()
.copied()
.flatten()
.map(|obj| {
get_object_file_path(sess, obj, self_contained_crt_objects).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 == "-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) => {
let is_msvc_link_exe = sess.target.is_like_msvc
&& flavor == LinkerFlavor::Msvc(Lld::No)
// Match exactly "link.exe"
&& linker_path.to_str() == Some("link.exe");
if !prog.status.success() {
let mut output = prog.stderr.clone();
output.extend_from_slice(&prog.stdout);
let escaped_output = escape_linker_output(&output, flavor);
let err = errors::LinkingFailed {
linker_path: &linker_path,
exit_status: prog.status,
command: cmd,
escaped_output,
verbose: sess.opts.verbose,
sysroot_dir: sess.sysroot.clone(),
};
sess.dcx().emit_err(err);
// If MSVC's `link.exe` was expected but the return code
// is not a Microsoft LNK error then suggest a way to fix or
// install the Visual Studio build tools.
if let Some(code) = prog.status.code() {
// All Microsoft `link.exe` linking ror codes are
// four digit numbers in the range 1000 to 9999 inclusive
if is_msvc_link_exe && (code < 1000 || code > 9999) {
let is_vs_installed = windows_registry::find_vs_version().is_ok();
let has_linker =
windows_registry::find_tool(&sess.target.arch, "link.exe").is_some();
sess.dcx().emit_note(errors::LinkExeUnexpectedError);
if is_vs_installed && has_linker {
// the linker is broken
sess.dcx().emit_note(errors::RepairVSBuildTools);
sess.dcx().emit_note(errors::MissingCppBuildToolComponent);
} else if is_vs_installed {
// the linker is not installed
sess.dcx().emit_note(errors::SelectCppBuildToolWorkload);
} else {
// visual studio is not installed
sess.dcx().emit_note(errors::VisualStudioNotInstalled);
}
}
}
sess.dcx().abort_if_errors();
}
let stderr = escape_string(&prog.stderr);
let mut stdout = escape_string(&prog.stdout);
info!("linker stderr:\n{}", &stderr);
info!("linker stdout:\n{}", &stdout);
// Hide some progress messages from link.exe that we don't care about.
// See https://github.com/chromium/chromium/blob/bfa41e41145ffc85f041384280caf2949bb7bd72/build/toolchain/win/tool_wrapper.py#L144-L146
if is_msvc_link_exe {
if let Ok(str) = str::from_utf8(&prog.stdout) {
let mut output = String::with_capacity(str.len());
for line in stdout.lines() {
if line.starts_with(" Creating library")
|| line.starts_with("Generating code")
|| line.starts_with("Finished generating code")
{
continue;
}
output += line;
output += "\r\n"
}
stdout = escape_string(output.trim().as_bytes())
}
}
let level = codegen_results.crate_info.lint_levels.linker_messages;
let lint = |msg| {
lint_level(sess, LINKER_MESSAGES, level, None, |diag| {
LinkerOutput { inner: msg }.decorate_lint(diag)
})
};
if !prog.stderr.is_empty() {
// We already print `warning:` at the start of the diagnostic. Remove it from the linker output if present.
let stderr = stderr
.strip_prefix("warning: ")
.unwrap_or(&stderr)
.replace(": warning: ", ": ");
lint(format!("linker stderr: {stderr}"));
}
if !stdout.is_empty() {
lint(format!("linker stdout: {}", stdout))
}
}
Err(e) => {
let linker_not_found = e.kind() == io::ErrorKind::NotFound;
let err = if linker_not_found {
sess.dcx().emit_err(errors::LinkerNotFound { linker_path, error: e })
} else {
sess.dcx().emit_err(errors::UnableToExeLinker {
linker_path,
error: e,
command_formatted: format!("{cmd:?}"),
})
};
if sess.target.is_like_msvc && linker_not_found {
sess.dcx().emit_note(errors::MsvcMissingLinker);
sess.dcx().emit_note(errors::CheckInstalledVisualStudio);
sess.dcx().emit_note(errors::InsufficientVSCodeProduct);
}
err.raise_fatal();
}
}
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_darwin => {
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.dcx().emit_warn(errors::ProcessingDymutilFailed {
status: prog.status,
output: escape_string(&output),
});
}
}
Err(error) => sess.dcx().emit_fatal(errors::UnableToRunDsymutil { error }),
}
}
// 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 = sess.opts.cg.strip;
if sess.target.is_like_darwin {
let stripcmd = "rust-objcopy";
match (strip, crate_type) {
(Strip::Debuginfo, _) => {
strip_with_external_utility(sess, stripcmd, out_filename, &["--strip-debug"])
}
// Per the manpage, `-x` is the maximum safe strip level for dynamic libraries. (#93988)
(Strip::Symbols, CrateType::Dylib | CrateType::Cdylib | CrateType::ProcMacro) => {
strip_with_external_utility(sess, stripcmd, out_filename, &["-x"])
}
(Strip::Symbols, _) => {
strip_with_external_utility(sess, stripcmd, out_filename, &["--strip-all"])
}
(Strip::None, _) => {}
}
}
if sess.target.is_like_solaris {
// Many illumos systems will have both the native 'strip' utility and
// the GNU one. Use the native version explicitly and do not rely on
// what's in the path.
//
// If cross-compiling and there is not a native version, then use
// `llvm-strip` and hope.
let stripcmd = if !sess.host.is_like_solaris { "rust-objcopy" } else { "/usr/bin/strip" };
match strip {
// Always preserve the symbol table (-x).
Strip::Debuginfo => strip_with_external_utility(sess, stripcmd, out_filename, &["-x"]),
// Strip::Symbols is handled via the --strip-all linker option.
Strip::Symbols => {}
Strip::None => {}
}
}
if sess.target.is_like_aix {
// `llvm-strip` doesn't work for AIX - their strip must be used.
if !sess.host.is_like_aix {
sess.dcx().emit_warn(errors::AixStripNotUsed);
}
let stripcmd = "/usr/bin/strip";
match strip {
Strip::Debuginfo => {
// FIXME: AIX's strip utility only offers option to strip line number information.
strip_with_external_utility(sess, stripcmd, out_filename, &["-X32_64", "-l"])
}
Strip::Symbols => {
// Must be noted this option might remove symbol __aix_rust_metadata and thus removes .info section which contains metadata.
strip_with_external_utility(sess, stripcmd, out_filename, &["-X32_64", "-r"])
}
Strip::None => {}
}
}
if should_archive {
let mut ab = archive_builder_builder.new_archive_builder(sess);
ab.add_file(temp_filename);
ab.build(out_filename);
}
}
fn strip_with_external_utility(sess: &Session, util: &str, out_filename: &Path, options: &[&str]) {
let mut cmd = Command::new(util);
cmd.args(options);
let mut new_path = sess.get_tools_search_paths(false);
if let Some(path) = env::var_os("PATH") {
new_path.extend(env::split_paths(&path));
}
cmd.env("PATH", env::join_paths(new_path).unwrap());
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.dcx().emit_warn(errors::StrippingDebugInfoFailed {
util,
status: prog.status,
output: escape_string(&output),
});
}
}
Err(error) => sess.dcx().emit_fatal(errors::UnableToRun { util, error }),
}
}
fn escape_string(s: &[u8]) -> String {
match str::from_utf8(s) {
Ok(s) => s.to_owned(),
Err(_) => format!("Non-UTF-8 output: {}", s.escape_ascii()),
}
}
#[cfg(not(windows))]
fn escape_linker_output(s: &[u8], _flavour: LinkerFlavor) -> String {
escape_string(s)
}
/// If the output of the msvc linker is not UTF-8 and the host is Windows,
/// then try to convert the string from the OEM encoding.
#[cfg(windows)]
fn escape_linker_output(s: &[u8], flavour: LinkerFlavor) -> String {
// This only applies to the actual MSVC linker.
if flavour != LinkerFlavor::Msvc(Lld::No) {
return escape_string(s);
}
match str::from_utf8(s) {
Ok(s) => return s.to_owned(),
Err(_) => match win::locale_byte_str_to_string(s, win::oem_code_page()) {
Some(s) => s,
// The string is not UTF-8 and isn't valid for the OEM code page
None => format!("Non-UTF-8 output: {}", s.escape_ascii()),
},
}
}
/// Wrappers around the Windows API.
#[cfg(windows)]
mod win {
use windows::Win32::Globalization::{
CP_OEMCP, GetLocaleInfoEx, LOCALE_IUSEUTF8LEGACYOEMCP, LOCALE_NAME_SYSTEM_DEFAULT,
LOCALE_RETURN_NUMBER, MB_ERR_INVALID_CHARS, MultiByteToWideChar,
};
/// Get the Windows system OEM code page. This is most notably the code page
/// used for link.exe's output.
pub(super) fn oem_code_page() -> u32 {
unsafe {
let mut cp: u32 = 0;
// We're using the `LOCALE_RETURN_NUMBER` flag to return a u32.
// But the API requires us to pass the data as though it's a [u16] string.
let len = size_of::<u32>() / size_of::<u16>();
let data = std::slice::from_raw_parts_mut(&mut cp as *mut u32 as *mut u16, len);
let len_written = GetLocaleInfoEx(
LOCALE_NAME_SYSTEM_DEFAULT,
LOCALE_IUSEUTF8LEGACYOEMCP | LOCALE_RETURN_NUMBER,
Some(data),
);
if len_written as usize == len { cp } else { CP_OEMCP }
}
}
/// Try to convert a multi-byte string to a UTF-8 string using the given code page
/// The string does not need to be null terminated.
///
/// This is implemented as a wrapper around `MultiByteToWideChar`.
/// See <https://learn.microsoft.com/en-us/windows/win32/api/stringapiset/nf-stringapiset-multibytetowidechar>
///
/// It will fail if the multi-byte string is longer than `i32::MAX` or if it contains
/// any invalid bytes for the expected encoding.
pub(super) fn locale_byte_str_to_string(s: &[u8], code_page: u32) -> Option<String> {
// `MultiByteToWideChar` requires a length to be a "positive integer".
if s.len() > isize::MAX as usize {
return None;
}
// Error if the string is not valid for the expected code page.
let flags = MB_ERR_INVALID_CHARS;
// Call MultiByteToWideChar twice.
// First to calculate the length then to convert the string.
let mut len = unsafe { MultiByteToWideChar(code_page, flags, s, None) };
if len > 0 {
let mut utf16 = vec![0; len as usize];
len = unsafe { MultiByteToWideChar(code_page, flags, s, Some(&mut utf16)) };
if len > 0 {
return utf16.get(..len as usize).map(String::from_utf16_lossy);
}
}
None
}
}
fn add_sanitizer_libraries(
sess: &Session,
flavor: LinkerFlavor,
crate_type: CrateType,
linker: &mut dyn Linker,
) {
if sess.target.is_like_android {
// Sanitizer runtime libraries are provided dynamically on Android
// targets.
return;
}
if sess.opts.unstable_opts.external_clangrt {
// Linking against in-tree sanitizer runtimes is disabled via
// `-Z external-clangrt`
return;
}
if matches!(crate_type, CrateType::Rlib | CrateType::Staticlib) {
return;
}
// On macOS and Windows using MSVC the runtimes are distributed as dylibs
// which should be linked to both executables and dynamic libraries.
// Everywhere else the runtimes are currently distributed as static
// libraries which should be linked to executables only.
if matches!(crate_type, CrateType::Dylib | CrateType::Cdylib | CrateType::ProcMacro)
&& !(sess.target.is_like_darwin || sess.target.is_like_msvc)
{
return;
}
let sanitizer = sess.opts.unstable_opts.sanitizer;
if sanitizer.contains(SanitizerSet::ADDRESS) {
link_sanitizer_runtime(sess, flavor, linker, "asan");
}
if sanitizer.contains(SanitizerSet::DATAFLOW) {
link_sanitizer_runtime(sess, flavor, linker, "dfsan");
}
if sanitizer.contains(SanitizerSet::LEAK)
&& !sanitizer.contains(SanitizerSet::ADDRESS)
&& !sanitizer.contains(SanitizerSet::HWADDRESS)
{
link_sanitizer_runtime(sess, flavor, linker, "lsan");
}
if sanitizer.contains(SanitizerSet::MEMORY) {
link_sanitizer_runtime(sess, flavor, linker, "msan");
}
if sanitizer.contains(SanitizerSet::THREAD) {
link_sanitizer_runtime(sess, flavor, linker, "tsan");
}
if sanitizer.contains(SanitizerSet::HWADDRESS) {
link_sanitizer_runtime(sess, flavor, linker, "hwasan");
}
if sanitizer.contains(SanitizerSet::SAFESTACK) {
link_sanitizer_runtime(sess, flavor, linker, "safestack");
}
}
fn link_sanitizer_runtime(
sess: &Session,
flavor: LinkerFlavor,
linker: &mut dyn Linker,
name: &str,
) {
fn find_sanitizer_runtime(sess: &Session, filename: &str) -> PathBuf {
let path = sess.target_tlib_path.dir.join(filename);
if path.exists() {
sess.target_tlib_path.dir.clone()
} else {
let default_sysroot = filesearch::get_or_default_sysroot();
let default_tlib =
filesearch::make_target_lib_path(&default_sysroot, sess.opts.target_triple.tuple());
default_tlib
}
}
let channel =
option_env!("CFG_RELEASE_CHANNEL").map(|channel| format!("-{channel}")).unwrap_or_default();
if sess.target.is_like_darwin {
// 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{channel}_rt.{name}");
let path = find_sanitizer_runtime(sess, &filename);
let rpath = path.to_str().expect("non-utf8 component in path");
linker.link_args(&["-rpath", rpath]);
linker.link_dylib_by_name(&filename, false, true);
} else if sess.target.is_like_msvc && flavor == LinkerFlavor::Msvc(Lld::No) && name == "asan" {
// MSVC provides the `/INFERASANLIBS` argument to automatically find the
// compatible ASAN library.
linker.link_arg("/INFERASANLIBS");
} else {
let filename = format!("librustc{channel}_rt.{name}.a");
let path = find_sanitizer_runtime(sess, &filename).join(&filename);
linker.link_staticlib_by_path(&path, true);
}
}
/// 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>,
features: LinkerFeaturesCli,
) -> Option<(PathBuf, LinkerFlavor)> {
let flavor = flavor.map(|flavor| adjust_flavor_to_features(flavor, features));
match (linker, flavor) {
(Some(linker), Some(flavor)) => Some((linker, flavor)),
// only the linker flavor is known; use the default linker for the selected flavor
(None, Some(flavor)) => Some((
PathBuf::from(match flavor {
LinkerFlavor::Gnu(Cc::Yes, _)
| LinkerFlavor::Darwin(Cc::Yes, _)
| LinkerFlavor::WasmLld(Cc::Yes)
| LinkerFlavor::Unix(Cc::Yes) => {
if cfg!(any(target_os = "solaris", target_os = "illumos")) {
// On historical Solaris systems, "cc" may have
// been Sun Studio, which is not flag-compatible
// with "gcc". This history casts a long shadow,
// and many modern illumos distributions today
// ship GCC as "gcc" without also making it
// available as "cc".
"gcc"
} else {
"cc"
}
}
LinkerFlavor::Gnu(_, Lld::Yes)
| LinkerFlavor::Darwin(_, Lld::Yes)
| LinkerFlavor::WasmLld(..)
| LinkerFlavor::Msvc(Lld::Yes) => "lld",
LinkerFlavor::Gnu(..) | LinkerFlavor::Darwin(..) | LinkerFlavor::Unix(..) => {
"ld"
}
LinkerFlavor::Msvc(..) => "link.exe",
LinkerFlavor::EmCc => {
if cfg!(windows) {
"emcc.bat"
} else {
"emcc"
}
}
LinkerFlavor::Bpf => "bpf-linker",
LinkerFlavor::Llbc => "llvm-bitcode-linker",
LinkerFlavor::Ptx => "rust-ptx-linker",
}),
flavor,
)),
(Some(linker), None) => {
let stem = linker.file_stem().and_then(|stem| stem.to_str()).unwrap_or_else(|| {
sess.dcx().emit_fatal(errors::LinkerFileStem);
});
let flavor = sess.target.linker_flavor.with_linker_hints(stem);
let flavor = adjust_flavor_to_features(flavor, features);
Some((linker, flavor))
}
(None, None) => None,
}
}
// While linker flavors and linker features are isomorphic (and thus targets don't need to
// define features separately), we use the flavor as the root piece of data and have the
// linker-features CLI flag influence *that*, so that downstream code does not have to check for
// both yet.
fn adjust_flavor_to_features(
flavor: LinkerFlavor,
features: LinkerFeaturesCli,
) -> LinkerFlavor {
// Note: a linker feature cannot be both enabled and disabled on the CLI.
if features.enabled.contains(LinkerFeatures::LLD) {
flavor.with_lld_enabled()
} else if features.disabled.contains(LinkerFeatures::LLD) {
flavor.with_lld_disabled()
} else {
flavor
}
}
let features = sess.opts.unstable_opts.linker_features;
// linker and linker flavor specified via command line have precedence over what the target
// specification specifies
let linker_flavor = match sess.opts.cg.linker_flavor {
// The linker flavors that are non-target specific can be directly translated to LinkerFlavor
Some(LinkerFlavorCli::Llbc) => Some(LinkerFlavor::Llbc),
Some(LinkerFlavorCli::Ptx) => Some(LinkerFlavor::Ptx),
// The linker flavors that corresponds to targets needs logic that keeps the base LinkerFlavor
_ => sess
.opts
.cg
.linker_flavor
.map(|flavor| sess.target.linker_flavor.with_cli_hints(flavor)),
};
if let Some(ret) = infer_from(sess, sess.opts.cg.linker.clone(), linker_flavor, features) {
return ret;
}
if let Some(ret) = infer_from(
sess,
sess.target.linker.as_deref().map(PathBuf::from),
Some(sess.target.linker_flavor),
features,
) {
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);
}
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),
}
}
#[derive(PartialEq)]
enum RlibFlavor {
Normal,
StaticlibBase,
}
fn print_native_static_libs(
sess: &Session,
out: &OutFileName,
all_native_libs: &[NativeLib],
all_rust_dylibs: &[&Path],
) {
let mut 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;
if sess.target.is_like_msvc {
let (prefix, suffix) = sess.staticlib_components(verbatim);
Some(format!("{prefix}{name}{suffix}"))
} else if sess.target.linker_flavor.is_gnu() {
Some(format!("-l{}{}", if verbatim { ":" } else { "" }, name))
} else {
Some(format!("-l{name}"))
}
}
NativeLibKind::Framework { .. } => {
// ld-only syntax, since there are no frameworks in MSVC
Some(format!("-framework {name}"))
}
// These are included, no need to print them
NativeLibKind::Static { bundle: None | Some(true), .. }
| NativeLibKind::LinkArg
| NativeLibKind::WasmImportModule
| NativeLibKind::RawDylib => None,
}
})
// deduplication of consecutive repeated libraries, see rust-lang/rust#113209
.dedup()
.collect();
for path in all_rust_dylibs {
// FIXME deduplicate with add_dynamic_crate
// Just need to tell the linker about where the library lives and
// what its name is
let parent = path.parent();
if let Some(dir) = parent {
let dir = fix_windows_verbatim_for_gcc(dir);
if sess.target.is_like_msvc {
let mut arg = String::from("/LIBPATH:");
arg.push_str(&dir.display().to_string());
lib_args.push(arg);
} else {
lib_args.push("-L".to_owned());
lib_args.push(dir.display().to_string());
}
}
let stem = path.file_stem().unwrap().to_str().unwrap();
// Convert library file-stem into a cc -l argument.
let lib = if let Some(lib) = stem.strip_prefix("lib")
&& !sess.target.is_like_windows
{
lib
} else {
stem
};
let path = parent.unwrap_or_else(|| Path::new(""));
if sess.target.is_like_msvc {
// When producing a dll, the MSVC linker may not actually emit a
// `foo.lib` file if the dll doesn't actually export any symbols, so we
// check to see if the file is there and just omit linking to it if it's
// not present.
let name = format!("{lib}.dll.lib");
if path.join(&name).exists() {
lib_args.push(name);
}
} else {
lib_args.push(format!("-l{lib}"));
}
}
match out {
OutFileName::Real(path) => {
out.overwrite(&lib_args.join(" "), sess);
sess.dcx().emit_note(errors::StaticLibraryNativeArtifactsToFile { path });
}
OutFileName::Stdout => {
sess.dcx().emit_note(errors::StaticLibraryNativeArtifacts);
// Prefix for greppability
// Note: This must not be translated as tools are allowed to depend on this exact string.
sess.dcx().note(format!("native-static-libs: {}", lib_args.join(" ")));
}
}
}
fn get_object_file_path(sess: &Session, name: &str, self_contained: bool) -> PathBuf {
let file_path = sess.target_tlib_path.dir.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 = sess.target_tlib_path.dir.join("self-contained").join(name);
if file_path.exists() {
return file_path;
}
}
for search_path in sess.target_filesearch().search_paths(PathKind::Native) {
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,
flavor: LinkerFlavor,
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 (aka 'response' files).
// 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(),
// Windows-style escaping for @-files is used by
// - all linkers targeting MSVC-like targets, including LLD
// - all LLD flavors running on Windows hosts
// С/С++ compilers use Posix-style escaping (except clang-cl, which we do not use).
is_like_msvc: sess.target.is_like_msvc
|| (cfg!(windows) && flavor.uses_lld() && !flavor.uses_cc()),
}
.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, linker: &Path) -> bool {
// 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.to_path_buf()
};
for dir in env::split_paths(&env::var_os("PATH").unwrap_or_default()) {
let full_path = dir.join(&linker_with_extension);
// If linker comes from sysroot assume self-contained mode
if full_path.is_file() && !full_path.starts_with(&sess.sysroot) {
return false;
}
}
true
}
/// Various toolchain components used during linking are used from rustc distribution
/// instead of being found somewhere on the host system.
/// We only provide such support for a very limited number of targets.
fn self_contained_components(
sess: &Session,
crate_type: CrateType,
linker: &Path,
) -> LinkSelfContainedComponents {
// Turn the backwards compatible bool values for `self_contained` into fully inferred
// `LinkSelfContainedComponents`.
let self_contained =
if let Some(self_contained) = sess.opts.cg.link_self_contained.explicitly_set {
// Emit an error if the user requested self-contained mode on the CLI but the target
// explicitly refuses it.
if sess.target.link_self_contained.is_disabled() {
sess.dcx().emit_err(errors::UnsupportedLinkSelfContained);
}
self_contained
} else {
match sess.target.link_self_contained {
LinkSelfContainedDefault::False => false,
LinkSelfContainedDefault::True => true,
LinkSelfContainedDefault::WithComponents(components) => {
// For target specs with explicitly enabled components, we can return them
// directly.
return components;
}
// FIXME: Find a better heuristic for "native musl toolchain is available",
// based on host and linker path, for example.
// (https://github.com/rust-lang/rust/pull/71769#issuecomment-626330237).
LinkSelfContainedDefault::InferredForMusl => sess.crt_static(Some(crate_type)),
LinkSelfContainedDefault::InferredForMingw => {
sess.host == sess.target
&& sess.target.vendor != "uwp"
&& detect_self_contained_mingw(sess, linker)
}
}
};
if self_contained {
LinkSelfContainedComponents::all()
} else {
LinkSelfContainedComponents::empty()
}
}
/// Add pre-link object files defined by the target spec.
fn add_pre_link_objects(
cmd: &mut dyn Linker,
sess: &Session,
flavor: LinkerFlavor,
link_output_kind: LinkOutputKind,
self_contained: bool,
) {
// FIXME: we are currently missing some infra here (per-linker-flavor CRT objects),
// so Fuchsia has to be special-cased.
let opts = &sess.target;
let empty = Default::default();
let objects = if self_contained {
&opts.pre_link_objects_self_contained
} else if !(sess.target.os == "fuchsia" && matches!(flavor, LinkerFlavor::Gnu(Cc::Yes, _))) {
&opts.pre_link_objects
} else {
&empty
};
for obj in objects.get(&link_output_kind).iter().copied().flatten() {
cmd.add_object(&get_object_file_path(sess, obj, self_contained));
}
}
/// Add post-link object files defined by the target spec.
fn add_post_link_objects(
cmd: &mut dyn Linker,
sess: &Session,
link_output_kind: LinkOutputKind,
self_contained: bool,
) {
let objects = if self_contained {
&sess.target.post_link_objects_self_contained
} else {
&sess.target.post_link_objects
};
for obj in objects.get(&link_output_kind).iter().copied().flatten() {
cmd.add_object(&get_object_file_path(sess, obj, self_contained));
}
}
/// Add arbitrary "pre-link" args defined by the target spec or from command line.
/// FIXME: Determine where exactly these args need to be inserted.
fn add_pre_link_args(cmd: &mut dyn Linker, sess: &Session, flavor: LinkerFlavor) {
if let Some(args) = sess.target.pre_link_args.get(&flavor) {
cmd.verbatim_args(args.iter().map(Deref::deref));
}
cmd.verbatim_args(&sess.opts.unstable_opts.pre_link_args);
}
/// Add a link script embedded in the target, if applicable.
fn add_link_script(cmd: &mut dyn Linker, sess: &Session, tmpdir: &Path, crate_type: CrateType) {
match (crate_type, &sess.target.link_script) {
(CrateType::Cdylib | CrateType::Executable, Some(script)) => {
if !sess.target.linker_flavor.is_gnu() {
sess.dcx().emit_fatal(errors::LinkScriptUnavailable);
}
let file_name = ["rustc", &sess.target.llvm_target, "linkfile.ld"].join("-");
let path = tmpdir.join(file_name);
if let Err(error) = fs::write(&path, script.as_ref()) {
sess.dcx().emit_fatal(errors::LinkScriptWriteFailure { path, error });
}
cmd.link_arg("--script").link_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.verbatim_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.verbatim_args(args.iter().map(Deref::deref));
}
} else if let Some(args) = sess.target.late_link_args_static.get(&flavor) {
cmd.verbatim_args(args.iter().map(Deref::deref));
}
if let Some(args) = sess.target.late_link_args.get(&flavor) {
cmd.verbatim_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.verbatim_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`, `-force_load` and equivalents to force rlib
/// to participate in linking like object files, but this proves to be expensive (#93791). Therefore
/// we instead just introduce an undefined reference to them. This could be done by `-u` command
/// line option to the linker or `EXTERN(...)` in linker scripts, however they does not only
/// introduce an undefined reference, but also make them the GC roots, preventing `--gc-sections`
/// from removing them, and this is especially problematic for embedded programming where every
/// byte counts.
///
/// This method creates a synthetic object file, which contains undefined references to all symbols
/// that are necessary for the linking. They are only present in symbol table but not actually
/// used in any sections, so the linker will therefore pick relevant rlibs for linking, but
/// unused `#[no_mangle]` or `#[used]` can still be discard by GC sections.
///
/// There's a few internal crates in the standard library (aka libcore and
/// libstd) which actually have a circular dependence upon one another. This
/// currently arises through "weak lang items" where libcore requires things
/// like `rust_begin_unwind` but libstd ends up defining it. To get this
/// circular dependence to work correctly we declare some of these things
/// in this synthetic object.
fn add_linked_symbol_object(
cmd: &mut dyn Linker,
sess: &Session,
tmpdir: &Path,
symbols: &[(String, SymbolExportKind)],
) {
if symbols.is_empty() {
return;
}
let Some(mut file) = super::metadata::create_object_file(sess) else {
return;
};
if file.format() == object::BinaryFormat::Coff {
// NOTE(nbdd0121): MSVC will hang if the input object file contains no sections,
// so add an empty section.
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);
}
// ld64 requires a relocation to load undefined symbols, see below.
// Not strictly needed if linking with lld, but might as well do it there too.
let ld64_section_helper = if file.format() == object::BinaryFormat::MachO {
Some(file.add_section(
file.segment_name(object::write::StandardSegment::Data).to_vec(),
"__data".into(),
object::SectionKind::Data,
))
} else {
None
};
for (sym, kind) in symbols.iter() {
let symbol = 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,
});
// The linker shipped with Apple's Xcode, ld64, works a bit differently from other linkers.
//
// Code-wise, the relevant parts of ld64 are roughly:
// 1. Find the `ArchiveLoadMode` based on commandline options, default to `parseObjects`.
// https://github.com/apple-oss-distributions/ld64/blob/ld64-954.16/src/ld/Options.cpp#L924-L932
// https://github.com/apple-oss-distributions/ld64/blob/ld64-954.16/src/ld/Options.h#L55
//
// 2. Read the archive table of contents (__.SYMDEF file).
// https://github.com/apple-oss-distributions/ld64/blob/ld64-954.16/src/ld/parsers/archive_file.cpp#L294-L325
//
// 3. Begin linking by loading "atoms" from input files.
// https://github.com/apple-oss-distributions/ld64/blob/ld64-954.16/doc/design/linker.html
// https://github.com/apple-oss-distributions/ld64/blob/ld64-954.16/src/ld/InputFiles.cpp#L1349
//
// a. Directly specified object files (`.o`) are parsed immediately.
// https://github.com/apple-oss-distributions/ld64/blob/ld64-954.16/src/ld/parsers/macho_relocatable_file.cpp#L4611-L4627
//
// - Undefined symbols are not atoms (`n_value > 0` denotes a common symbol).
// https://github.com/apple-oss-distributions/ld64/blob/ld64-954.16/src/ld/parsers/macho_relocatable_file.cpp#L2455-L2468
// https://maskray.me/blog/2022-02-06-all-about-common-symbols
//
// - Relocations/fixups are atoms.
// https://github.com/apple-oss-distributions/ld64/blob/ce6341ae966b3451aa54eeb049f2be865afbd578/src/ld/parsers/macho_relocatable_file.cpp#L2088-L2114
//
// b. Archives are not parsed yet.
// https://github.com/apple-oss-distributions/ld64/blob/ld64-954.16/src/ld/parsers/archive_file.cpp#L467-L577
//
// 4. When a symbol is needed by an atom, parse the object file that contains the symbol.
// https://github.com/apple-oss-distributions/ld64/blob/ld64-954.16/src/ld/InputFiles.cpp#L1417-L1491
// https://github.com/apple-oss-distributions/ld64/blob/ld64-954.16/src/ld/parsers/archive_file.cpp#L579-L597
//
// All of the steps above are fairly similar to other linkers, except that **it completely
// ignores undefined symbols**.
//
// So to make this trick work on ld64, we need to do something else to load the relevant
// object files. We do this by inserting a relocation (fixup) for each symbol.
if let Some(section) = ld64_section_helper {
apple::add_data_and_relocation(&mut file, section, symbol, &sess.target, *kind)
.expect("failed adding relocation");
}
}
let path = tmpdir.join("symbols.o");
let result = std::fs::write(&path, file.write().unwrap());
if let Err(error) = result {
sess.dcx().emit_fatal(errors::FailedToWrite { path, error });
}
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 matches!(crate_type, CrateType::Dylib | CrateType::ProcMacro)
&& let Some(m) = &codegen_results.metadata_module
&& let Some(obj) = &m.object
{
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_components: LinkSelfContainedComponents,
apple_sdk_root: Option<&Path>,
) {
if !sess.opts.unstable_opts.link_native_libraries {
return;
}
let fallback = Some(NativeLibSearchFallback { self_contained_components, apple_sdk_root });
let _ = walk_native_lib_search_dirs(sess, fallback, |dir, is_framework| {
if is_framework {
cmd.framework_path(dir);
} else {
cmd.include_path(&fix_windows_verbatim_for_gcc(dir));
}
ControlFlow::<()>::Continue(())
});
}
/// 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.cg.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,
) {
if !sess.target.has_rpath {
return;
}
// 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 rpath_config = RPathConfig {
libs: &*libs,
out_filename: out_filename.to_path_buf(),
is_like_darwin: sess.target.is_like_darwin,
linker_is_gnu: sess.target.linker_flavor.is_gnu(),
};
cmd.link_args(&rpath::get_rpath_linker_args(&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(
path: &Path,
flavor: LinkerFlavor,
sess: &Session,
archive_builder_builder: &dyn ArchiveBuilderBuilder,
crate_type: CrateType,
tmpdir: &Path,
out_filename: &Path,
codegen_results: &CodegenResults,
self_contained_components: LinkSelfContainedComponents,
) -> Command {
let self_contained_crt_objects = self_contained_components.is_crt_objects_enabled();
let cmd = &mut *super::linker::get_linker(
sess,
path,
flavor,
self_contained_components.are_any_components_enabled(),
&codegen_results.crate_info.target_cpu,
);
let link_output_kind = link_output_kind(sess, crate_type);
// ------------ Early order-dependent options ------------
// If we're building something like a dynamic library then some platforms
// need to make sure that all symbols are exported correctly from the
// dynamic library.
// Must be passed before any libraries to prevent the symbols to export from being thrown away,
// at least on some platforms (e.g. windows-gnu).
cmd.export_symbols(
tmpdir,
crate_type,
&codegen_results.crate_info.exported_symbols[&crate_type],
);
// Can be used for adding custom CRT objects or overriding order-dependent options above.
// FIXME: In practice built-in target specs use this for arbitrary order-independent options,
// introduce a target spec option for order-independent linker options and migrate built-in
// specs to it.
add_pre_link_args(cmd, sess, flavor);
// ------------ Object code and libraries, order-dependent ------------
// Pre-link CRT objects.
add_pre_link_objects(cmd, sess, flavor, link_output_kind, self_contained_crt_objects);
add_linked_symbol_object(
cmd,
sess,
tmpdir,
&codegen_results.crate_info.linked_symbols[&crate_type],
);
// Sanitizer libraries.
add_sanitizer_libraries(sess, flavor, crate_type, cmd);
// Object code from the current crate.
// Take careful note of the ordering of the arguments we pass to the linker
// here. Linkers will assume that things on the left depend on things to the
// right. Things on the right cannot depend on things on the left. This is
// all formally implemented in terms of resolving symbols (libs on the right
// resolve unknown symbols of libs on the left, but not vice versa).
//
// For this reason, we have organized the arguments we pass to the linker as
// such:
//
// 1. The local object that LLVM just generated
// 2. Local native libraries
// 3. Upstream rust libraries
// 4. Upstream native libraries
//
// The rationale behind this ordering is that those items lower down in the
// list can't depend on items higher up in the list. For example nothing can
// depend on what we just generated (e.g., that'd be a circular dependency).
// Upstream rust libraries are not supposed to depend on our local native
// libraries as that would violate the structure of the DAG, in that
// scenario they are required to link to them as well in a shared fashion.
//
// Note that upstream rust libraries may contain native dependencies as
// well, but they also can't depend on what we just started to add to the
// link line. And finally upstream native libraries can't depend on anything
// in this DAG so far because they can only depend on other native libraries
// and such dependencies are also required to be specified.
add_local_crate_regular_objects(cmd, codegen_results);
add_local_crate_metadata_objects(cmd, crate_type, codegen_results);
add_local_crate_allocator_objects(cmd, codegen_results);
// Avoid linking to dynamic libraries unless they satisfy some undefined symbols
// at the point at which they are specified on the command line.
// Must be passed before any (dynamic) libraries to have effect on them.
// On Solaris-like systems, `-z ignore` acts as both `--as-needed` and `--gc-sections`
// so it will ignore unreferenced ELF sections from relocatable objects.
// For that reason, we put this flag after metadata objects as they would otherwise be removed.
// FIXME: Support more fine-grained dead code removal on Solaris/illumos
// and move this option back to the top.
cmd.add_as_needed();
// Local native libraries of all kinds.
add_local_native_libraries(
cmd,
sess,
archive_builder_builder,
codegen_results,
tmpdir,
link_output_kind,
);
// Upstream rust crates and their non-dynamic native libraries.
add_upstream_rust_crates(
cmd,
sess,
archive_builder_builder,
codegen_results,
crate_type,
tmpdir,
link_output_kind,
);
// Dynamic native libraries from upstream crates.
add_upstream_native_libraries(
cmd,
sess,
archive_builder_builder,
codegen_results,
tmpdir,
link_output_kind,
);
// Raw-dylibs from all crates.
let raw_dylib_dir = tmpdir.join("raw-dylibs");
if sess.target.binary_format == BinaryFormat::Elf {
// On ELF we can't pass the raw-dylibs stubs to the linker as a path,
// instead we need to pass them via -l. To find the stub, we need to add
// the directory of the stub to the linker search path.
// We make an extra directory for this to avoid polluting the search path.
if let Err(error) = fs::create_dir(&raw_dylib_dir) {
sess.dcx().emit_fatal(errors::CreateTempDir { error })
}
cmd.include_path(&raw_dylib_dir);
}
// Link with the import library generated for any raw-dylib functions.
if sess.target.is_like_windows {
for output_path in raw_dylib::create_raw_dylib_dll_import_libs(
sess,
archive_builder_builder,
codegen_results.crate_info.used_libraries.iter(),
tmpdir,
true,
) {
cmd.add_object(&output_path);
}
} else {
for link_path in raw_dylib::create_raw_dylib_elf_stub_shared_objects(
sess,
codegen_results.crate_info.used_libraries.iter(),
&raw_dylib_dir,
) {
// Always use verbatim linkage, see comments in create_raw_dylib_elf_stub_shared_objects.
cmd.link_dylib_by_name(&link_path, true, false);
}
}
// As with add_upstream_native_libraries, we need to add the upstream raw-dylib symbols in case
// they are used within inlined functions or instantiated generic functions. We do this *after*
// handling the raw-dylib symbols in the current crate to make sure that those are chosen first
// by the linker.
let dependency_linkage = codegen_results
.crate_info
.dependency_formats
.get(&crate_type)
.expect("failed to find crate type in dependency format list");
// We sort the libraries below
#[allow(rustc::potential_query_instability)]
let mut native_libraries_from_nonstatics = codegen_results
.crate_info
.native_libraries
.iter()
.filter_map(|(&cnum, libraries)| {
if sess.target.is_like_windows {
(dependency_linkage[cnum] != Linkage::Static).then_some(libraries)
} else {
Some(libraries)
}
})
.flatten()
.collect::<Vec<_>>();
native_libraries_from_nonstatics.sort_unstable_by(|a, b| a.name.as_str().cmp(b.name.as_str()));
if sess.target.is_like_windows {
for output_path in raw_dylib::create_raw_dylib_dll_import_libs(
sess,
archive_builder_builder,
native_libraries_from_nonstatics,
tmpdir,
false,
) {
cmd.add_object(&output_path);
}
} else {
for link_path in raw_dylib::create_raw_dylib_elf_stub_shared_objects(
sess,
native_libraries_from_nonstatics,
&raw_dylib_dir,
) {
// Always use verbatim linkage, see comments in create_raw_dylib_elf_stub_shared_objects.
cmd.link_dylib_by_name(&link_path, true, false);
}
}
// Library linking above uses some global state for things like `-Bstatic`/`-Bdynamic` to make
// command line shorter, reset it to default here before adding more libraries.
cmd.reset_per_library_state();
// FIXME: Built-in target specs occasionally use this for linking system libraries,
// eliminate all such uses by migrating them to `#[link]` attributes in `lib(std,c,unwind)`
// and remove the option.
add_late_link_args(cmd, sess, flavor, crate_type, codegen_results);
// ------------ Arbitrary order-independent options ------------
// Add order-independent options determined by rustc from its compiler options,
// target properties and source code.
add_order_independent_options(
cmd,
sess,
link_output_kind,
self_contained_components,
flavor,
crate_type,
codegen_results,
out_filename,
tmpdir,
);
// Can be used for arbitrary order-independent options.
// In practice may also be occasionally used for linking native libraries.
// Passed after compiler-generated options to support manual overriding when necessary.
add_user_defined_link_args(cmd, sess);
// ------------ Object code and libraries, order-dependent ------------
// Post-link CRT objects.
add_post_link_objects(cmd, sess, link_output_kind, self_contained_crt_objects);
// ------------ 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. Currently the last holdout is wasm32-unknown-emscripten.
add_post_link_args(cmd, sess, flavor);
cmd.take_cmd()
}
fn add_order_independent_options(
cmd: &mut dyn Linker,
sess: &Session,
link_output_kind: LinkOutputKind,
self_contained_components: LinkSelfContainedComponents,
flavor: LinkerFlavor,
crate_type: CrateType,
codegen_results: &CodegenResults,
out_filename: &Path,
tmpdir: &Path,
) {
// Take care of the flavors and CLI options requesting the `lld` linker.
add_lld_args(cmd, sess, flavor, self_contained_components);
add_apple_link_args(cmd, sess, flavor);
let apple_sdk_root = add_apple_sdk(cmd, sess, flavor);
add_link_script(cmd, sess, tmpdir, crate_type);
if sess.target.os == "fuchsia"
&& crate_type == CrateType::Executable
&& !matches!(flavor, LinkerFlavor::Gnu(Cc::Yes, _))
{
let prefix = if sess.opts.unstable_opts.sanitizer.contains(SanitizerSet::ADDRESS) {
"asan/"
} else {
""
};
cmd.link_arg(format!("--dynamic-linker={prefix}ld.so.1"));
}
if sess.target.eh_frame_header {
cmd.add_eh_frame_header();
}
// Make the binary compatible with data execution prevention schemes.
cmd.add_no_exec();
if self_contained_components.is_crt_objects_enabled() {
cmd.no_crt_objects();
}
if sess.target.os == "emscripten" {
cmd.cc_arg(if sess.opts.unstable_opts.emscripten_wasm_eh {
"-fwasm-exceptions"
} else if sess.panic_strategy() == PanicStrategy::Abort {
"-sDISABLE_EXCEPTION_CATCHING=1"
} else {
"-sDISABLE_EXCEPTION_CATCHING=0"
});
}
if flavor == LinkerFlavor::Llbc {
cmd.link_args(&[
"--target",
&versioned_llvm_target(sess),
"--target-cpu",
&codegen_results.crate_info.target_cpu,
]);
if codegen_results.crate_info.target_features.len() > 0 {
cmd.link_arg(&format!(
"--target-feature={}",
&codegen_results.crate_info.target_features.join(",")
));
}
} else if flavor == LinkerFlavor::Ptx {
cmd.link_args(&["--fallback-arch", &codegen_results.crate_info.target_cpu]);
} else if flavor == LinkerFlavor::Bpf {
cmd.link_args(&["--cpu", &codegen_results.crate_info.target_cpu]);
if let Some(feat) = [sess.opts.cg.target_feature.as_str(), &sess.target.options.features]
.into_iter()
.find(|feat| !feat.is_empty())
{
cmd.link_args(&["--cpu-features", feat]);
}
}
cmd.linker_plugin_lto();
add_library_search_dirs(cmd, sess, self_contained_components, apple_sdk_root.as_deref());
cmd.output_filename(out_filename);
if crate_type == CrateType::Executable
&& sess.target.is_like_windows
&& let Some(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, crate_type, 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(sess.opts.cg.strip, &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();
}
// OBJECT-FILES-NO, AUDIT-ORDER
if sess.opts.unstable_opts.ehcont_guard {
cmd.ehcont_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.dcx().emit_warn(errors::UnableToWriteDebuggerVisualizer {
path: visualizer_out_file,
error,
});
}
};
}
visualizer_paths
}
fn add_native_libs_from_crate(
cmd: &mut dyn Linker,
sess: &Session,
archive_builder_builder: &dyn ArchiveBuilderBuilder,
codegen_results: &CodegenResults,
tmpdir: &Path,
bundled_libs: &FxIndexSet<Symbol>,
cnum: CrateNum,
link_static: bool,
link_dynamic: bool,
link_output_kind: LinkOutputKind,
) {
if !sess.opts.unstable_opts.link_native_libraries {
// 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.
return;
}
if link_static && cnum != LOCAL_CRATE && !bundled_libs.is_empty() {
// If rlib contains native libs as archives, unpack them to tmpdir.
let rlib = &codegen_results.crate_info.used_crate_source[&cnum].rlib.as_ref().unwrap().0;
archive_builder_builder
.extract_bundled_libs(rlib, tmpdir, bundled_libs)
.unwrap_or_else(|e| sess.dcx().emit_fatal(e));
}
let native_libs = match cnum {
LOCAL_CRATE => &codegen_results.crate_info.used_libraries,
_ => &codegen_results.crate_info.native_libraries[&cnum],
};
let mut last = (None, NativeLibKind::Unspecified, false);
for lib in native_libs {
if !relevant_lib(sess, lib) {
continue;
}
// Skip if this library is the same as the last.
last = if (Some(lib.name), lib.kind, lib.verbatim) == last {
continue;
} else {
(Some(lib.name), lib.kind, lib.verbatim)
};
let name = lib.name.as_str();
let verbatim = lib.verbatim;
match lib.kind {
NativeLibKind::Static { bundle, whole_archive } => {
if link_static {
let bundle = bundle.unwrap_or(true);
let whole_archive = whole_archive == Some(true);
if bundle && cnum != LOCAL_CRATE {
if let Some(filename) = lib.filename {
// If rlib contains native libs as archives, they are unpacked to tmpdir.
let path = tmpdir.join(filename.as_str());
cmd.link_staticlib_by_path(&path, whole_archive);
}
} else {
cmd.link_staticlib_by_name(name, verbatim, whole_archive);
}
}
}
NativeLibKind::Dylib { as_needed } => {
if link_dynamic {
cmd.link_dylib_by_name(name, verbatim, as_needed.unwrap_or(true))
}
}
NativeLibKind::Unspecified => {
// If we are generating a static binary, prefer static library when the
// link kind is unspecified.
if !link_output_kind.can_link_dylib() && !sess.target.crt_static_allows_dylibs {
if link_static {
cmd.link_staticlib_by_name(name, verbatim, false);
}
} else if link_dynamic {
cmd.link_dylib_by_name(name, verbatim, true);
}
}
NativeLibKind::Framework { as_needed } => {
if link_dynamic {
cmd.link_framework_by_name(name, verbatim, as_needed.unwrap_or(true))
}
}
NativeLibKind::RawDylib => {
// Handled separately in `linker_with_args`.
}
NativeLibKind::WasmImportModule => {}
NativeLibKind::LinkArg => {
if link_static {
if verbatim {
cmd.verbatim_arg(name);
} else {
cmd.link_arg(name);
}
}
}
}
}
}
fn add_local_native_libraries(
cmd: &mut dyn Linker,
sess: &Session,
archive_builder_builder: &dyn ArchiveBuilderBuilder,
codegen_results: &CodegenResults,
tmpdir: &Path,
link_output_kind: LinkOutputKind,
) {
// All static and dynamic native library dependencies are linked to the local crate.
let link_static = true;
let link_dynamic = true;
add_native_libs_from_crate(
cmd,
sess,
archive_builder_builder,
codegen_results,
tmpdir,
&Default::default(),
LOCAL_CRATE,
link_static,
link_dynamic,
link_output_kind,
);
}
fn add_upstream_rust_crates(
cmd: &mut dyn Linker,
sess: &Session,
archive_builder_builder: &dyn ArchiveBuilderBuilder,
codegen_results: &CodegenResults,
crate_type: CrateType,
tmpdir: &Path,
link_output_kind: LinkOutputKind,
) {
// 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
.get(&crate_type)
.expect("failed to find crate type in dependency format list");
if sess.target.is_like_aix {
// Unlike ELF linkers, AIX doesn't feature `DT_SONAME` to override
// the dependency name when outputing a shared library. Thus, `ld` will
// use the full path to shared libraries as the dependency if passed it
// by default unless `noipath` is passed.
// https://www.ibm.com/docs/en/aix/7.3?topic=l-ld-command.
cmd.link_or_cc_arg("-bnoipath");
}
for &cnum in &codegen_results.crate_info.used_crates {
// 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.
// We must always link crates `compiler_builtins` and `profiler_builtins` statically.
// Even if they were already included into a dylib
// (e.g. `libstd` when `-C prefer-dynamic` is used).
// FIXME: `dependency_formats` can report `profiler_builtins` as `NotLinked` for some
// reason, it shouldn't do that because `profiler_builtins` should indeed be linked.
let linkage = data[cnum];
let link_static_crate = linkage == Linkage::Static
|| (linkage == Linkage::IncludedFromDylib || linkage == Linkage::NotLinked)
&& (codegen_results.crate_info.compiler_builtins == Some(cnum)
|| codegen_results.crate_info.profiler_runtime == Some(cnum));
let mut bundled_libs = Default::default();
match linkage {
Linkage::Static | Linkage::IncludedFromDylib | Linkage::NotLinked => {
if link_static_crate {
bundled_libs = codegen_results.crate_info.native_libraries[&cnum]
.iter()
.filter_map(|lib| lib.filename)
.collect();
add_static_crate(
cmd,
sess,
archive_builder_builder,
codegen_results,
tmpdir,
cnum,
&bundled_libs,
);
}
}
Linkage::Dynamic => {
let src = &codegen_results.crate_info.used_crate_source[&cnum];
add_dynamic_crate(cmd, sess, &src.dylib.as_ref().unwrap().0);
}
}
// Static libraries are linked for a subset of linked upstream crates.
// 1. If the upstream crate is a directly linked rlib then we must link the native library
// because the rlib is just an archive.
// 2. If the upstream crate is a dylib or a rlib linked through dylib, then we do not link
// the native library because it is already linked into the dylib, and even if
// inline/const/generic functions from the dylib can refer to symbols from the native
// library, those symbols should be exported and available from the dylib anyway.
// 3. Libraries bundled into `(compiler,profiler)_builtins` are special, see above.
let link_static = link_static_crate;
// Dynamic libraries are not linked here, see the FIXME in `add_upstream_native_libraries`.
let link_dynamic = false;
add_native_libs_from_crate(
cmd,
sess,
archive_builder_builder,
codegen_results,
tmpdir,
&bundled_libs,
cnum,
link_static,
link_dynamic,
link_output_kind,
);
}
}
fn add_upstream_native_libraries(
cmd: &mut dyn Linker,
sess: &Session,
archive_builder_builder: &dyn ArchiveBuilderBuilder,
codegen_results: &CodegenResults,
tmpdir: &Path,
link_output_kind: LinkOutputKind,
) {
for &cnum in &codegen_results.crate_info.used_crates {
// Static libraries are not linked here, they are linked in `add_upstream_rust_crates`.
// FIXME: Merge this function to `add_upstream_rust_crates` so that all native libraries
// are linked together with their respective upstream crates, and in their originally
// specified order. This is slightly breaking due to our use of `--as-needed` (see crater
// results in https://github.com/rust-lang/rust/pull/102832#issuecomment-1279772306).
let link_static = false;
// Dynamic libraries are linked for all linked upstream crates.
// 1. If the upstream crate is a directly linked rlib then we must link the native library
// because the rlib is just an archive.
// 2. If the upstream crate is a dylib or a rlib linked through dylib, then we have to link
// the native library too because inline/const/generic functions from the dylib can refer
// to symbols from the native library, so the native library providing those symbols should
// be available when linking our final binary.
let link_dynamic = true;
add_native_libs_from_crate(
cmd,
sess,
archive_builder_builder,
codegen_results,
tmpdir,
&Default::default(),
cnum,
link_static,
link_dynamic,
link_output_kind,
);
}
}
// Rehome lib paths (which exclude the library file name) that point into the sysroot lib directory
// to be relative to the sysroot directory, which may be a relative path specified by the user.
//
// If the sysroot is a relative path, and the sysroot libs are specified as an absolute path, the
// linker command line can be non-deterministic due to the paths including the current working
// directory. The linker command line needs to be deterministic since it appears inside the PDB
// file generated by the MSVC linker. See https://github.com/rust-lang/rust/issues/112586.
//
// The returned path will always have `fix_windows_verbatim_for_gcc()` applied to it.
fn rehome_sysroot_lib_dir(sess: &Session, lib_dir: &Path) -> PathBuf {
let sysroot_lib_path = &sess.target_tlib_path.dir;
let canonical_sysroot_lib_path =
{ try_canonicalize(sysroot_lib_path).unwrap_or_else(|_| sysroot_lib_path.clone()) };
let canonical_lib_dir = try_canonicalize(lib_dir).unwrap_or_else(|_| lib_dir.to_path_buf());
if canonical_lib_dir == canonical_sysroot_lib_path {
// This path already had `fix_windows_verbatim_for_gcc()` applied if needed.
sysroot_lib_path.clone()
} else {
fix_windows_verbatim_for_gcc(lib_dir)
}
}
fn rehome_lib_path(sess: &Session, path: &Path) -> PathBuf {
if let Some(dir) = path.parent() {
let file_name = path.file_name().expect("library path has no file name component");
rehome_sysroot_lib_dir(sess, dir).join(file_name)
} else {
fix_windows_verbatim_for_gcc(path)
}
}
// 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(
cmd: &mut dyn Linker,
sess: &Session,
archive_builder_builder: &dyn ArchiveBuilderBuilder,
codegen_results: &CodegenResults,
tmpdir: &Path,
cnum: CrateNum,
bundled_lib_file_names: &FxIndexSet<Symbol>,
) {
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_staticlib_by_path(&rehome_lib_path(sess, path), false);
if !are_upstream_rust_objects_already_included(sess)
|| ignored_for_lto(sess, &codegen_results.crate_info, cnum)
{
link_upstream(cratepath);
return;
}
let dst = tmpdir.join(cratepath.file_name().unwrap());
let name = cratepath.file_name().unwrap().to_str().unwrap();
let name = &name[3..name.len() - 5]; // chop off lib/.rlib
let bundled_lib_file_names = bundled_lib_file_names.clone();
sess.prof.generic_activity_with_arg("link_altering_rlib", name).run(|| {
let canonical_name = name.replace('-', "_");
let upstream_rust_objects_already_included =
are_upstream_rust_objects_already_included(sess);
let is_builtins =
sess.target.no_builtins || !codegen_results.crate_info.is_no_builtins.contains(&cnum);
let mut archive = archive_builder_builder.new_archive_builder(sess);
if let Err(error) = 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'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.
if upstream_rust_objects_already_included && is_rust_object && is_builtins {
return true;
}
// We skip native libraries because:
// 1. This native libraries won't be used from the generated rlib,
// so we can throw them away to avoid the copying work.
// 2. We can't allow it to be a single remaining entry in archive
// as some linkers may complain on that.
if bundled_lib_file_names.contains(&Symbol::intern(f)) {
return true;
}
false
}),
) {
sess.dcx()
.emit_fatal(errors::RlibArchiveBuildFailure { path: cratepath.clone(), error });
}
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) {
cmd.link_dylib_by_path(&rehome_lib_path(sess, cratepath), true);
}
fn relevant_lib(sess: &Session, lib: &NativeLib) -> bool {
match lib.cfg {
Some(ref cfg) => rustc_attr_parsing::cfg_matches(cfg, sess, CRATE_NODE_ID, None),
None => true,
}
}
pub(crate) fn are_upstream_rust_objects_already_included(sess: &Session) -> bool {
match sess.lto() {
config::Lto::Fat => true,
config::Lto::Thin => {
// If we defer LTO to the linker, we haven't run LTO ourselves, so
// any upstream object files have not been copied yet.
!sess.opts.cg.linker_plugin_lto.enabled()
}
config::Lto::No | config::Lto::ThinLocal => false,
}
}
/// We need to communicate five things to the linker on Apple/Darwin targets:
/// - The architecture.
/// - The operating system (and that it's an Apple platform).
/// - The environment / ABI.
/// - The deployment target.
/// - The SDK version.
fn add_apple_link_args(cmd: &mut dyn Linker, sess: &Session, flavor: LinkerFlavor) {
if !sess.target.is_like_darwin {
return;
}
let LinkerFlavor::Darwin(cc, _) = flavor else {
return;
};
// `sess.target.arch` (`target_arch`) is not detailed enough.
let llvm_arch = sess.target.llvm_target.split_once('-').expect("LLVM target must have arch").0;
let target_os = &*sess.target.os;
let target_abi = &*sess.target.abi;
// The architecture name to forward to the linker.
//
// Supported architecture names can be found in the source:
// https://github.com/apple-oss-distributions/ld64/blob/ld64-951.9/src/abstraction/MachOFileAbstraction.hpp#L578-L648
//
// Intentially verbose to ensure that the list always matches correctly
// with the list in the source above.
let ld64_arch = match llvm_arch {
"armv7k" => "armv7k",
"armv7s" => "armv7s",
"arm64" => "arm64",
"arm64e" => "arm64e",
"arm64_32" => "arm64_32",
// ld64 doesn't understand i686, so fall back to i386 instead.
//
// Same story when linking with cc, since that ends up invoking ld64.
"i386" | "i686" => "i386",
"x86_64" => "x86_64",
"x86_64h" => "x86_64h",
_ => bug!("unsupported architecture in Apple target: {}", sess.target.llvm_target),
};
if cc == Cc::No {
// From the man page for ld64 (`man ld`):
// > The linker accepts universal (multiple-architecture) input files,
// > but always creates a "thin" (single-architecture), standard
// > Mach-O output file. The architecture for the output file is
// > specified using the -arch option.
//
// The linker has heuristics to determine the desired architecture,
// but to be safe, and to avoid a warning, we set the architecture
// explicitly.
cmd.link_args(&["-arch", ld64_arch]);
// Man page says that ld64 supports the following platform names:
// > - macos
// > - ios
// > - tvos
// > - watchos
// > - bridgeos
// > - visionos
// > - xros
// > - mac-catalyst
// > - ios-simulator
// > - tvos-simulator
// > - watchos-simulator
// > - visionos-simulator
// > - xros-simulator
// > - driverkit
let platform_name = match (target_os, target_abi) {
(os, "") => os,
("ios", "macabi") => "mac-catalyst",
("ios", "sim") => "ios-simulator",
("tvos", "sim") => "tvos-simulator",
("watchos", "sim") => "watchos-simulator",
("visionos", "sim") => "visionos-simulator",
_ => bug!("invalid OS/ABI combination for Apple target: {target_os}, {target_abi}"),
};
let min_version = sess.apple_deployment_target().fmt_full().to_string();
// The SDK version is used at runtime when compiling with a newer SDK / version of Xcode:
// - By dyld to give extra warnings and errors, see e.g.:
// <https://github.com/apple-oss-distributions/dyld/blob/dyld-1165.3/common/MachOFile.cpp#L3029>
// <https://github.com/apple-oss-distributions/dyld/blob/dyld-1165.3/common/MachOFile.cpp#L3738-L3857>
// - By system frameworks to change certain behaviour. For example, the default value of
// `-[NSView wantsBestResolutionOpenGLSurface]` is `YES` when the SDK version is >= 10.15.
// <https://developer.apple.com/documentation/appkit/nsview/1414938-wantsbestresolutionopenglsurface?language=objc>
//
// We do not currently know the actual SDK version though, so we have a few options:
// 1. Use the minimum version supported by rustc.
// 2. Use the same as the deployment target.
// 3. Use an arbitary recent version.
// 4. Omit the version.
//
// The first option is too low / too conservative, and means that users will not get the
// same behaviour from a binary compiled with rustc as with one compiled by clang.
//
// The second option is similarly conservative, and also wrong since if the user specified a
// higher deployment target than the SDK they're compiling/linking with, the runtime might
// make invalid assumptions about the capabilities of the binary.
//
// The third option requires that `rustc` is periodically kept up to date with Apple's SDK
// version, and is also wrong for similar reasons as above.
//
// The fourth option is bad because while `ld`, `otool`, `vtool` and such understand it to
// mean "absent" or `n/a`, dyld doesn't actually understand it, and will end up interpreting
// it as 0.0, which is again too low/conservative.
//
// Currently, we lie about the SDK version, and choose the second option.
//
// FIXME(madsmtm): Parse the SDK version from the SDK root instead.
// <https://github.com/rust-lang/rust/issues/129432>
let sdk_version = &*min_version;
// From the man page for ld64 (`man ld`):
// > This is set to indicate the platform, oldest supported version of
// > that platform that output is to be used on, and the SDK that the
// > output was built against.
//
// Like with `-arch`, the linker can figure out the platform versions
// itself from the binaries being linked, but to be safe, we specify
// the desired versions here explicitly.
cmd.link_args(&["-platform_version", platform_name, &*min_version, sdk_version]);
} else {
// cc == Cc::Yes
//
// We'd _like_ to use `-target` everywhere, since that can uniquely
// communicate all the required details except for the SDK version
// (which is read by Clang itself from the SDKROOT), but that doesn't
// work on GCC, and since we don't know whether the `cc` compiler is
// Clang, GCC, or something else, we fall back to other options that
// also work on GCC when compiling for macOS.
//
// Targets other than macOS are ill-supported by GCC (it doesn't even
// support e.g. `-miphoneos-version-min`), so in those cases we can
// fairly safely use `-target`. See also the following, where it is
// made explicit that the recommendation by LLVM developers is to use
// `-target`: <https://github.com/llvm/llvm-project/issues/88271>
if target_os == "macos" {
// `-arch` communicates the architecture.
//
// CC forwards the `-arch` to the linker, so we use the same value
// here intentionally.
cmd.cc_args(&["-arch", ld64_arch]);
// The presence of `-mmacosx-version-min` makes CC default to
// macOS, and it sets the deployment target.
let version = sess.apple_deployment_target().fmt_full();
// Intentionally pass this as a single argument, Clang doesn't
// seem to like it otherwise.
cmd.cc_arg(&format!("-mmacosx-version-min={version}"));
// macOS has no environment, so with these two, we've told CC the
// four desired parameters.
//
// We avoid `-m32`/`-m64`, as this is already encoded by `-arch`.
} else {
cmd.cc_args(&["-target", &versioned_llvm_target(sess)]);
}
}
}
fn add_apple_sdk(cmd: &mut dyn Linker, sess: &Session, flavor: LinkerFlavor) -> Option<PathBuf> {
let os = &sess.target.os;
if sess.target.vendor != "apple"
|| !matches!(os.as_ref(), "ios" | "tvos" | "watchos" | "visionos" | "macos")
|| !matches!(flavor, LinkerFlavor::Darwin(..))
{
return None;
}
if os == "macos" && !matches!(flavor, LinkerFlavor::Darwin(Cc::No, _)) {
return None;
}
let sdk_root = sess.time("get_apple_sdk_root", || get_apple_sdk_root(sess))?;
match flavor {
LinkerFlavor::Darwin(Cc::Yes, _) => {
// Use `-isysroot` instead of `--sysroot`, as only the former
// makes Clang treat it as a platform SDK.
//
// This is admittedly a bit strange, as on most targets
// `-isysroot` only applies to include header files, but on Apple
// targets this also applies to libraries and frameworks.
cmd.cc_arg("-isysroot");
cmd.cc_arg(&sdk_root);
}
LinkerFlavor::Darwin(Cc::No, _) => {
cmd.link_arg("-syslibroot");
cmd.link_arg(&sdk_root);
}
_ => unreachable!(),
}
Some(sdk_root)
}
fn get_apple_sdk_root(sess: &Session) -> Option<PathBuf> {
if let Ok(sdkroot) = env::var("SDKROOT") {
let p = PathBuf::from(&sdkroot);
// Ignore invalid SDKs, similar to what clang does:
// https://github.com/llvm/llvm-project/blob/llvmorg-19.1.6/clang/lib/Driver/ToolChains/Darwin.cpp#L2212-L2229
//
// NOTE: Things are complicated here by the fact that `rustc` can be run by Cargo to compile
// build scripts and proc-macros for the host, and thus we need to ignore SDKROOT if it's
// clearly set for the wrong platform.
//
// FIXME(madsmtm): Make this more robust (maybe read `SDKSettings.json` like Clang does?).
match &*apple::sdk_name(&sess.target).to_lowercase() {
"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") => {
}
"macosx"
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") => {}
"xros"
if sdkroot.contains("XRSimulator.platform")
|| sdkroot.contains("MacOSX.platform") => {}
"xrsimulator"
if sdkroot.contains("XROS.platform") || sdkroot.contains("MacOSX.platform") => {}
// Ignore `SDKROOT` if it's not a valid path.
_ if !p.is_absolute() || p == Path::new("/") || !p.exists() => {}
_ => return Some(p),
}
}
apple::get_sdk_root(sess)
}
/// When using the linker flavors opting in to `lld`, add the necessary paths and arguments to
/// invoke it:
/// - when the self-contained linker flag is active: the build of `lld` distributed with rustc,
/// - or any `lld` available to `cc`.
fn add_lld_args(
cmd: &mut dyn Linker,
sess: &Session,
flavor: LinkerFlavor,
self_contained_components: LinkSelfContainedComponents,
) {
debug!(
"add_lld_args requested, flavor: '{:?}', target self-contained components: {:?}",
flavor, self_contained_components,
);
// If the flavor doesn't use a C/C++ compiler to invoke the linker, or doesn't opt in to `lld`,
// we don't need to do anything.
if !(flavor.uses_cc() && flavor.uses_lld()) {
return;
}
// 1. Implement the "self-contained" part of this feature by adding rustc distribution
// directories to the tool's search path, depending on a mix between what users can specify on
// the CLI, and what the target spec enables (as it can't disable components):
// - if the self-contained linker is enabled on the CLI or by the target spec,
// - and if the self-contained linker is not disabled on the CLI.
let self_contained_cli = sess.opts.cg.link_self_contained.is_linker_enabled();
let self_contained_target = self_contained_components.is_linker_enabled();
let self_contained_linker = self_contained_cli || self_contained_target;
if self_contained_linker && !sess.opts.cg.link_self_contained.is_linker_disabled() {
let mut linker_path_exists = false;
for path in sess.get_tools_search_paths(false) {
let linker_path = path.join("gcc-ld");
linker_path_exists |= linker_path.exists();
cmd.cc_arg({
let mut arg = OsString::from("-B");
arg.push(linker_path);
arg
});
}
if !linker_path_exists {
// As a sanity check, we emit an error if none of these paths exist: we want
// self-contained linking and have no linker.
sess.dcx().emit_fatal(errors::SelfContainedLinkerMissing);
}
}
// 2. Implement the "linker flavor" part of this feature by asking `cc` to use some kind of
// `lld` as the linker.
//
// Note that wasm targets skip this step since the only option there anyway
// is to use LLD but the `wasm32-wasip2` target relies on a wrapper around
// this, `wasm-component-ld`, which is overridden if this option is passed.
if !sess.target.is_like_wasm {
cmd.cc_arg("-fuse-ld=lld");
// On ELF platforms like at least x64 linux, GNU ld and LLD have opposite defaults on some
// section garbage-collection features. For example, the somewhat popular `linkme` crate and
// its dependents rely in practice on this difference: when using lld, they need `-z
// nostart-stop-gc` to prevent encapsulation symbols and sections from being
// garbage-collected.
//
// More information about all this can be found in:
// - https://maskray.me/blog/2021-01-31-metadata-sections-comdat-and-shf-link-order
// - https://lld.llvm.org/ELF/start-stop-gc
//
// So when using lld, we restore, for now, the traditional behavior to help migration, but
// will remove it in the future.
// Since this only disables an optimization, it shouldn't create issues, but is in theory
// slightly suboptimal. However, it:
// - doesn't have any visible impact on our benchmarks
// - reduces the need to disable lld for the crates that depend on this
//
// Note that lld can detect some cases where this difference is relied on, and emits a
// dedicated error to add this link arg. We could make use of this error to emit an FCW. As
// of writing this, we don't do it, because lld is already enabled by default on nightly
// without this mitigation: no working project would see the FCW, so we do this to help
// stabilization.
//
// FIXME: emit an FCW if linking fails due its absence, and then remove this link-arg in the
// future.
if sess.target.llvm_target == "x86_64-unknown-linux-gnu" {
cmd.link_arg("-znostart-stop-gc");
}
}
if !flavor.is_gnu() {
// Tell clang to use a non-default LLD flavor.
// Gcc doesn't understand the target option, but we currently assume
// that gcc is not used for Apple and Wasm targets (#97402).
//
// Note that we don't want to do that by default on macOS: e.g. passing a
// 10.7 target to LLVM works, but not to recent versions of clang/macOS, as
// shown in issue #101653 and the discussion in PR #101792.
//
// It could be required in some cases of cross-compiling with
// LLD, but this is generally unspecified, and we don't know
// which specific versions of clang, macOS SDK, host and target OS
// combinations impact us here.
//
// So we do a simple first-approximation until we know more of what the
// Apple targets require (and which would be handled prior to hitting this
// LLD codepath anyway), but the expectation is that until then
// this should be manually passed if needed. We specify the target when
// targeting a different linker flavor on macOS, and that's also always
// the case when targeting WASM.
if sess.target.linker_flavor != sess.host.linker_flavor {
cmd.cc_arg(format!("--target={}", versioned_llvm_target(sess)));
}
}
}