Google Git
Sign in
fuchsia / third_party / rust / 9d09331e00b02f81c714b0c41ce3a38380dd36a2 / . / src / librustc_codegen_ssa / back / link.rs
blob: 3adaa07db91b012c054e80fa1a274fbf53db9184 [file] [log] [blame]
use rustc_data_structures::fx::FxHashSet;
use rustc_fs_util::fix_windows_verbatim_for_gcc;
use rustc_hir::def_id::CrateNum;
use rustc_middle::middle::cstore::{EncodedMetadata, LibSource, NativeLib};
use rustc_middle::middle::dependency_format::Linkage;
use rustc_session::config::{self, CFGuard, CrateType, DebugInfo};
use rustc_session::config::{OutputFilenames, OutputType, PrintRequest, SanitizerSet};
use rustc_session::output::{check_file_is_writeable, invalid_output_for_target, out_filename};
use rustc_session::search_paths::PathKind;
use rustc_session::utils::NativeLibKind;
/// For all the linkers we support, and information they might
/// need out of the shared crate context before we get rid of it.
use rustc_session::{filesearch, Session};
use rustc_span::symbol::Symbol;
use rustc_target::spec::crt_objects::{CrtObjects, CrtObjectsFallback};
use rustc_target::spec::{LinkOutputKind, LinkerFlavor, LldFlavor};
use rustc_target::spec::{PanicStrategy, RelocModel, RelroLevel};
use super::archive::ArchiveBuilder;
use super::command::Command;
use super::linker::{self, Linker};
use super::rpath::{self, RPathConfig};
use crate::{looks_like_rust_object_file, CodegenResults, CrateInfo, METADATA_FILENAME};
use cc::windows_registry;
use tempfile::{Builder as TempFileBuilder, TempDir};
use std::ffi::OsString;
use std::path::{Path, PathBuf};
use std::process::{ExitStatus, Output, Stdio};
use std::{ascii, char, env, fmt, fs, io, mem, str};
pub fn remove(sess: &Session, path: &Path) {
if let Err(e) = fs::remove_file(path) {
sess.err(&format!("failed to remove {}: {}", path.display(), e));
}
}
/// Performs the linkage portion of the compilation phase. This will generate all
/// of the requested outputs for this compilation session.
pub fn link_binary<'a, B: ArchiveBuilder<'a>>(
sess: &'a Session,
codegen_results: &CodegenResults,
outputs: &OutputFilenames,
crate_name: &str,
target_cpu: &str,
) {
let _timer = sess.timer("link_binary");
let output_metadata = sess.opts.output_types.contains_key(&OutputType::Metadata);
for &crate_type in sess.crate_types().iter() {
// Ignore executable crates if we have -Z no-codegen, as they will error.
if (sess.opts.debugging_opts.no_codegen || !sess.opts.output_types.should_codegen())
&& !output_metadata
&& crate_type == CrateType::Executable
{
continue;
}
if invalid_output_for_target(sess, crate_type) {
bug!(
"invalid output type `{:?}` for target os `{}`",
crate_type,
sess.opts.target_triple
);
}
sess.time("link_binary_check_files_are_writeable", || {
for obj in codegen_results.modules.iter().filter_map(|m| m.object.as_ref()) {
check_file_is_writeable(obj, sess);
}
});
let tmpdir = TempFileBuilder::new()
.prefix("rustc")
.tempdir()
.unwrap_or_else(|err| sess.fatal(&format!("couldn't create a temp dir: {}", err)));
if outputs.outputs.should_codegen() {
let out_filename = out_filename(sess, crate_type, outputs, crate_name);
match crate_type {
CrateType::Rlib => {
let _timer = sess.timer("link_rlib");
link_rlib::<B>(
sess,
codegen_results,
RlibFlavor::Normal,
&out_filename,
&tmpdir,
)
.build();
}
CrateType::Staticlib => {
link_staticlib::<B>(sess, codegen_results, &out_filename, &tmpdir);
}
_ => {
link_natively::<B>(
sess,
crate_type,
&out_filename,
codegen_results,
tmpdir.path(),
target_cpu,
);
}
}
if sess.opts.json_artifact_notifications {
sess.parse_sess.span_diagnostic.emit_artifact_notification(&out_filename, "link");
}
}
if sess.opts.cg.save_temps {
let _ = tmpdir.into_path();
}
}
// Remove the temporary object file and metadata if we aren't saving temps
sess.time("link_binary_remove_temps", || {
if !sess.opts.cg.save_temps {
if sess.opts.output_types.should_codegen()
&& !preserve_objects_for_their_debuginfo(sess)
{
for obj in codegen_results.modules.iter().filter_map(|m| m.object.as_ref()) {
remove(sess, obj);
}
}
if let Some(ref metadata_module) = codegen_results.metadata_module {
if let Some(ref obj) = metadata_module.object {
remove(sess, obj);
}
}
if let Some(ref allocator_module) = codegen_results.allocator_module {
if let Some(ref obj) = allocator_module.object {
remove(sess, obj);
}
}
}
});
}
// The third parameter is for env vars, used on windows to set up the
// path for MSVC to find its DLLs, and gcc to find its bundled
// toolchain
fn get_linker(
sess: &Session,
linker: &Path,
flavor: LinkerFlavor,
self_contained: bool,
) -> Command {
let msvc_tool = windows_registry::find_tool(&sess.opts.target_triple.triple(), "link.exe");
// If our linker looks like a batch script on Windows then to execute this
// we'll need to spawn `cmd` explicitly. This is primarily done to handle
// emscripten where the linker is `emcc.bat` and needs to be spawned as
// `cmd /c emcc.bat ...`.
//
// This worked historically but is needed manually since #42436 (regression
// was tagged as #42791) and some more info can be found on #44443 for
// emscripten itself.
let mut cmd = match linker.to_str() {
Some(linker) if cfg!(windows) && linker.ends_with(".bat") => Command::bat_script(linker),
_ => match flavor {
LinkerFlavor::Lld(f) => Command::lld(linker, f),
LinkerFlavor::Msvc
if sess.opts.cg.linker.is_none() && sess.target.target.options.linker.is_none() =>
{
Command::new(msvc_tool.as_ref().map(|t| t.path()).unwrap_or(linker))
}
_ => Command::new(linker),
},
};
// UWP apps have API restrictions enforced during Store submissions.
// To comply with the Windows App Certification Kit,
// MSVC needs to link with the Store versions of the runtime libraries (vcruntime, msvcrt, etc).
let t = &sess.target.target;
if (flavor == LinkerFlavor::Msvc || flavor == LinkerFlavor::Lld(LldFlavor::Link))
&& t.target_vendor == "uwp"
{
if let Some(ref tool) = msvc_tool {
let original_path = tool.path();
if let Some(ref root_lib_path) = original_path.ancestors().nth(4) {
let arch = match t.arch.as_str() {
"x86_64" => Some("x64".to_string()),
"x86" => Some("x86".to_string()),
"aarch64" => Some("arm64".to_string()),
"arm" => Some("arm".to_string()),
_ => None,
};
if let Some(ref a) = arch {
// FIXME: Move this to `fn linker_with_args`.
let mut arg = OsString::from("/LIBPATH:");
arg.push(format!("{}\\lib\\{}\\store", root_lib_path.display(), a.to_string()));
cmd.arg(&arg);
} else {
warn!("arch is not supported");
}
} else {
warn!("MSVC root path lib location not found");
}
} else {
warn!("link.exe not found");
}
}
// The compiler's sysroot often has some bundled tools, so add it to the
// PATH for the child.
let mut new_path = sess.host_filesearch(PathKind::All).get_tools_search_paths(self_contained);
let mut msvc_changed_path = false;
if sess.target.target.options.is_like_msvc {
if let Some(ref tool) = msvc_tool {
cmd.args(tool.args());
for &(ref k, ref v) in tool.env() {
if k == "PATH" {
new_path.extend(env::split_paths(v));
msvc_changed_path = true;
} else {
cmd.env(k, v);
}
}
}
}
if !msvc_changed_path {
if let Some(path) = env::var_os("PATH") {
new_path.extend(env::split_paths(&path));
}
}
cmd.env("PATH", env::join_paths(new_path).unwrap());
cmd
}
pub fn each_linked_rlib(
info: &CrateInfo,
f: &mut dyn FnMut(CrateNum, &Path),
) -> Result<(), String> {
let crates = info.used_crates_static.iter();
let mut fmts = None;
for (ty, list) in info.dependency_formats.iter() {
match ty {
CrateType::Executable
| CrateType::Staticlib
| CrateType::Cdylib
| CrateType::ProcMacro => {
fmts = Some(list);
break;
}
_ => {}
}
}
let fmts = match fmts {
Some(f) => f,
None => return Err("could not find formats for rlibs".to_string()),
};
for &(cnum, ref path) in crates {
match fmts.get(cnum.as_usize() - 1) {
Some(&Linkage::NotLinked | &Linkage::IncludedFromDylib) => continue,
Some(_) => {}
None => return Err("could not find formats for rlibs".to_string()),
}
let name = &info.crate_name[&cnum];
let path = match *path {
LibSource::Some(ref p) => p,
LibSource::MetadataOnly => {
return Err(format!(
"could not find rlib for: `{}`, found rmeta (metadata) file",
name
));
}
LibSource::None => return Err(format!("could not find rlib for: `{}`", name)),
};
f(cnum, &path);
}
Ok(())
}
/// We use a temp directory here to avoid races between concurrent rustc processes,
/// such as builds in the same directory using the same filename for metadata while
/// building an `.rlib` (stomping over one another), or writing an `.rmeta` into a
/// directory being searched for `extern crate` (observing an incomplete file).
/// The returned path is the temporary file containing the complete metadata.
pub fn emit_metadata(sess: &Session, metadata: &EncodedMetadata, tmpdir: &TempDir) -> PathBuf {
let out_filename = tmpdir.path().join(METADATA_FILENAME);
let result = fs::write(&out_filename, &metadata.raw_data);
if let Err(e) = result {
sess.fatal(&format!("failed to write {}: {}", out_filename.display(), e));
}
out_filename
}
// Create an 'rlib'
//
// An rlib in its current incarnation is essentially a renamed .a file. The
// rlib primarily contains the object file of the crate, but it also contains
// all of the object files from native libraries. This is done by unzipping
// native libraries and inserting all of the contents into this archive.
fn link_rlib<'a, B: ArchiveBuilder<'a>>(
sess: &'a Session,
codegen_results: &CodegenResults,
flavor: RlibFlavor,
out_filename: &Path,
tmpdir: &TempDir,
) -> B {
info!("preparing rlib to {:?}", out_filename);
let mut ab = <B as ArchiveBuilder>::new(sess, out_filename, None);
for obj in codegen_results.modules.iter().filter_map(|m| m.object.as_ref()) {
ab.add_file(obj);
}
// Note that in this loop we are ignoring the value of `lib.cfg`. That is,
// we may not be configured to actually include a static library if we're
// adding it here. That's because later when we consume this rlib we'll
// decide whether we actually needed the static library or not.
//
// To do this "correctly" we'd need to keep track of which libraries added
// which object files to the archive. We don't do that here, however. The
// #[link(cfg(..))] feature is unstable, though, and only intended to get
// liblibc working. In that sense the check below just indicates that if
// there are any libraries we want to omit object files for at link time we
// just exclude all custom object files.
//
// Eventually if we want to stabilize or flesh out the #[link(cfg(..))]
// feature then we'll need to figure out how to record what objects were
// loaded from the libraries found here and then encode that into the
// metadata of the rlib we're generating somehow.
for lib in codegen_results.crate_info.used_libraries.iter() {
match lib.kind {
NativeLibKind::StaticBundle => {}
NativeLibKind::StaticNoBundle
| NativeLibKind::Dylib
| NativeLibKind::Framework
| NativeLibKind::RawDylib
| NativeLibKind::Unspecified => continue,
}
if let Some(name) = lib.name {
ab.add_native_library(name);
}
}
// After adding all files to the archive, we need to update the
// symbol table of the archive.
ab.update_symbols();
// 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.
//
// Basically, all this means is that this code should not move above the
// code above.
match flavor {
RlibFlavor::Normal => {
// Instead of putting the metadata in an object file section, rlibs
// contain the metadata in a separate file.
ab.add_file(&emit_metadata(sess, &codegen_results.metadata, tmpdir));
// After adding all files to the archive, we need to update the
// symbol table of the archive. This currently dies on macOS (see
// #11162), and isn't necessary there anyway
if !sess.target.target.options.is_like_osx {
ab.update_symbols();
}
}
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);
}
}
}
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<'a, B: ArchiveBuilder<'a>>(
sess: &'a Session,
codegen_results: &CodegenResults,
out_filename: &Path,
tempdir: &TempDir,
) {
let mut ab =
link_rlib::<B>(sess, codegen_results, RlibFlavor::StaticlibBase, out_filename, tempdir);
let mut all_native_libs = vec![];
let res = each_linked_rlib(&codegen_results.crate_info, &mut |cnum, path| {
let name = &codegen_results.crate_info.crate_name[&cnum];
let native_libs = &codegen_results.crate_info.native_libraries[&cnum];
// Here when we include the rlib into our staticlib we need to make a
// decision whether to include the extra object files along the way.
// These extra object files come from statically included native
// libraries, but they may be cfg'd away with #[link(cfg(..))].
//
// This unstable feature, though, only needs liblibc to work. The only
// use case there is where musl is statically included in liblibc.rlib,
// so if we don't want the included version we just need to skip it. As
// a result the logic here is that if *any* linked library is cfg'd away
// we just skip all object files.
//
// Clearly this is not sufficient for a general purpose feature, and
// we'd want to read from the library's metadata to determine which
// object files come from where and selectively skip them.
let skip_object_files = native_libs
.iter()
.any(|lib| lib.kind == NativeLibKind::StaticBundle && !relevant_lib(sess, lib));
ab.add_rlib(
path,
&name.as_str(),
are_upstream_rust_objects_already_included(sess)
&& !ignored_for_lto(sess, &codegen_results.crate_info, cnum),
skip_object_files,
)
.unwrap();
all_native_libs.extend(codegen_results.crate_info.native_libraries[&cnum].iter().cloned());
});
if let Err(e) = res {
sess.fatal(&e);
}
ab.update_symbols();
ab.build();
if !all_native_libs.is_empty() {
if sess.opts.prints.contains(&PrintRequest::NativeStaticLibs) {
print_native_static_libs(sess, &all_native_libs);
}
}
}
// Create a dynamic library or executable
//
// This will invoke the system linker/cc to create the resulting file. This
// links to all upstream files as well.
fn link_natively<'a, B: ArchiveBuilder<'a>>(
sess: &'a Session,
crate_type: CrateType,
out_filename: &Path,
codegen_results: &CodegenResults,
tmpdir: &Path,
target_cpu: &str,
) {
info!("preparing {:?} to {:?}", crate_type, out_filename);
let (linker_path, flavor) = linker_and_flavor(sess);
let mut cmd = linker_with_args::<B>(
&linker_path,
flavor,
sess,
crate_type,
tmpdir,
out_filename,
codegen_results,
target_cpu,
);
linker::disable_localization(&mut cmd);
for &(ref k, ref v) in &sess.target.target.options.link_env {
cmd.env(k, v);
}
for k in &sess.target.target.options.link_env_remove {
cmd.env_remove(k);
}
if sess.opts.debugging_opts.print_link_args {
println!("{:?}", &cmd);
}
// May have not found libraries in the right formats.
sess.abort_if_errors();
// Invoke the system linker
info!("{:?}", &cmd);
let retry_on_segfault = env::var("RUSTC_RETRY_LINKER_ON_SEGFAULT").is_ok();
let mut prog;
let mut i = 0;
loop {
i += 1;
prog = sess.time("run_linker", || exec_linker(sess, &cmd, out_filename, tmpdir));
let output = match prog {
Ok(ref output) => output,
Err(_) => 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 "unrecognized command line option:
// '-no-pie'" for gcc or "unknown argument: '-no-pie'" for clang. If so,
// reperform the link step without the -no-pie option. This is safe because
// if the linker doesn't support -no-pie then it should not default to
// linking executables as pie. Different versions of gcc seem to use
// different quotes in the error message so don't check for them.
if sess.target.target.options.linker_is_gnu
&& flavor != LinkerFlavor::Ld
&& (out.contains("unrecognized command line option")
|| out.contains("unknown argument"))
&& out.contains("-no-pie")
&& cmd.get_args().iter().any(|e| e.to_string_lossy() == "-no-pie")
{
info!("linker output: {:?}", out);
warn!("Linker does not support -no-pie command line option. Retrying without.");
for arg in cmd.take_args() {
if arg.to_string_lossy() != "-no-pie" {
cmd.arg(arg);
}
}
info!("{:?}", &cmd);
continue;
}
// Detect '-static-pie' used with an older version of gcc or clang not supporting it.
// Fallback from '-static-pie' to '-static' in that case.
if sess.target.target.options.linker_is_gnu
&& flavor != LinkerFlavor::Ld
&& (out.contains("unrecognized command line option")
|| out.contains("unknown argument"))
&& (out.contains("-static-pie") || out.contains("--no-dynamic-linker"))
&& cmd.get_args().iter().any(|e| e.to_string_lossy() == "-static-pie")
{
info!("linker output: {:?}", out);
warn!(
"Linker does not support -static-pie command line option. Retrying with -static instead."
);
// Mirror `add_(pre,post)_link_objects` to replace CRT objects.
let self_contained = crt_objects_fallback(sess, crate_type);
let opts = &sess.target.target.options;
let pre_objects = if self_contained {
&opts.pre_link_objects_fallback
} else {
&opts.pre_link_objects
};
let post_objects = if self_contained {
&opts.post_link_objects_fallback
} else {
&opts.post_link_objects
};
let get_objects = |objects: &CrtObjects, kind| {
objects
.get(&kind)
.iter()
.copied()
.flatten()
.map(|obj| get_object_file_path(sess, obj, self_contained).into_os_string())
.collect::<Vec<_>>()
};
let pre_objects_static_pie = get_objects(pre_objects, LinkOutputKind::StaticPicExe);
let post_objects_static_pie = get_objects(post_objects, LinkOutputKind::StaticPicExe);
let mut pre_objects_static = get_objects(pre_objects, LinkOutputKind::StaticNoPicExe);
let mut post_objects_static = get_objects(post_objects, LinkOutputKind::StaticNoPicExe);
// Assume that we know insertion positions for the replacement arguments from replaced
// arguments, which is true for all supported targets.
assert!(pre_objects_static.is_empty() || !pre_objects_static_pie.is_empty());
assert!(post_objects_static.is_empty() || !post_objects_static_pie.is_empty());
for arg in cmd.take_args() {
if arg.to_string_lossy() == "-static-pie" {
// Replace the output kind.
cmd.arg("-static");
} else if pre_objects_static_pie.contains(&arg) {
// Replace the pre-link objects (replace the first and remove the rest).
cmd.args(mem::take(&mut pre_objects_static));
} else if post_objects_static_pie.contains(&arg) {
// Replace the post-link objects (replace the first and remove the rest).
cmd.args(mem::take(&mut post_objects_static));
} else {
cmd.arg(arg);
}
}
info!("{:?}", &cmd);
continue;
}
// Here's a terribly awful hack that really shouldn't be present in any
// compiler. Here an environment variable is supported to automatically
// retry the linker invocation if the linker looks like it segfaulted.
//
// Gee that seems odd, normally segfaults are things we want to know
// about! Unfortunately though in rust-lang/rust#38878 we're
// experiencing the linker segfaulting on Travis quite a bit which is
// causing quite a bit of pain to land PRs when they spuriously fail
// due to a segfault.
//
// The issue #38878 has some more debugging information on it as well,
// but this unfortunately looks like it's just a race condition in
// macOS's linker with some thread pool working in the background. It
// seems that no one currently knows a fix for this so in the meantime
// we're left with this...
if !retry_on_segfault || i > 3 {
break;
}
let msg_segv = "clang: error: unable to execute command: Segmentation fault: 11";
let msg_bus = "clang: error: unable to execute command: Bus error: 10";
if out.contains(msg_segv) || out.contains(msg_bus) {
warn!(
"looks like the linker segfaulted when we tried to call it, \
automatically retrying again. cmd = {:?}, out = {}.",
cmd, out,
);
continue;
}
if is_illegal_instruction(&output.status) {
warn!(
"looks like the linker hit an illegal instruction when we \
tried to call it, automatically retrying again. cmd = {:?}, ]\
out = {}, status = {}.",
cmd, out, output.status,
);
continue;
}
#[cfg(unix)]
fn is_illegal_instruction(status: &ExitStatus) -> bool {
use std::os::unix::prelude::*;
status.signal() == Some(libc::SIGILL)
}
#[cfg(windows)]
fn is_illegal_instruction(_status: &ExitStatus) -> bool {
false
}
}
match prog {
Ok(prog) => {
fn escape_string(s: &[u8]) -> String {
str::from_utf8(s).map(|s| s.to_owned()).unwrap_or_else(|_| {
let mut x = "Non-UTF-8 output: ".to_string();
x.extend(s.iter().flat_map(|&b| ascii::escape_default(b)).map(char::from));
x
})
}
if !prog.status.success() {
let mut output = prog.stderr.clone();
output.extend_from_slice(&prog.stdout);
sess.struct_err(&format!(
"linking with `{}` failed: {}",
linker_path.display(),
prog.status
))
.note(&format!("{:?}", &cmd))
.note(&escape_string(&output))
.emit();
// If MSVC's `link.exe` was expected but the return code
// is not a Microsoft LNK error then suggest a way to fix or
// install the Visual Studio build tools.
if let Some(code) = prog.status.code() {
if sess.target.target.options.is_like_msvc
&& flavor == LinkerFlavor::Msvc
// Respect the command line override
&& sess.opts.cg.linker.is_none()
// Match exactly "link.exe"
&& linker_path.to_str() == Some("link.exe")
// All Microsoft `link.exe` linking error codes are
// four digit numbers in the range 1000 to 9999 inclusive
&& (code < 1000 || code > 9999)
{
let is_vs_installed = windows_registry::find_vs_version().is_ok();
let has_linker = windows_registry::find_tool(
&sess.opts.target_triple.triple(),
"link.exe",
)
.is_some();
sess.note_without_error("`link.exe` returned an unexpected error");
if is_vs_installed && has_linker {
// the linker is broken
sess.note_without_error(
"the Visual Studio build tools may need to be repaired \
using the Visual Studio installer",
);
sess.note_without_error(
"or a necessary component may be missing from the \
\"C++ build tools\" workload",
);
} else if is_vs_installed {
// the linker is not installed
sess.note_without_error(
"in the Visual Studio installer, ensure the \
\"C++ build tools\" workload is selected",
);
} else {
// visual studio is not installed
sess.note_without_error(
"you may need to install Visual Studio build tools with the \
\"C++ build tools\" workload",
);
}
}
}
sess.abort_if_errors();
}
info!("linker stderr:\n{}", escape_string(&prog.stderr));
info!("linker stdout:\n{}", escape_string(&prog.stdout));
}
Err(e) => {
let linker_not_found = e.kind() == io::ErrorKind::NotFound;
let mut linker_error = {
if linker_not_found {
sess.struct_err(&format!("linker `{}` not found", linker_path.display()))
} else {
sess.struct_err(&format!(
"could not exec the linker `{}`",
linker_path.display()
))
}
};
linker_error.note(&e.to_string());
if !linker_not_found {
linker_error.note(&format!("{:?}", &cmd));
}
linker_error.emit();
if sess.target.target.options.is_like_msvc && linker_not_found {
sess.note_without_error(
"the msvc targets depend on the msvc linker \
but `link.exe` was not found",
);
sess.note_without_error(
"please ensure that VS 2013, VS 2015, VS 2017 or VS 2019 \
was installed with the Visual C++ option",
);
}
sess.abort_if_errors();
}
}
// On macOS, debuggers need this utility to get run to do some munging of
// the symbols. Note, though, that if the object files are being preserved
// for their debug information there's no need for us to run dsymutil.
if sess.target.target.options.is_like_osx
&& sess.opts.debuginfo != DebugInfo::None
&& !preserve_objects_for_their_debuginfo(sess)
{
if let Err(e) = Command::new("dsymutil").arg(out_filename).output() {
sess.fatal(&format!("failed to run dsymutil: {}", e))
}
}
}
fn link_sanitizers(sess: &Session, crate_type: CrateType, linker: &mut dyn Linker) {
if crate_type != CrateType::Executable {
return;
}
let sanitizer = sess.opts.debugging_opts.sanitizer;
if sanitizer.contains(SanitizerSet::ADDRESS) {
link_sanitizer_runtime(sess, linker, "asan");
}
if sanitizer.contains(SanitizerSet::LEAK) {
link_sanitizer_runtime(sess, linker, "lsan");
}
if sanitizer.contains(SanitizerSet::MEMORY) {
link_sanitizer_runtime(sess, linker, "msan");
}
if sanitizer.contains(SanitizerSet::THREAD) {
link_sanitizer_runtime(sess, linker, "tsan");
}
}
fn link_sanitizer_runtime(sess: &Session, linker: &mut dyn Linker, name: &str) {
let default_sysroot = filesearch::get_or_default_sysroot();
let default_tlib =
filesearch::make_target_lib_path(&default_sysroot, sess.opts.target_triple.triple());
let channel = option_env!("CFG_RELEASE_CHANNEL")
.map(|channel| format!("-{}", channel))
.unwrap_or_default();
match sess.opts.target_triple.triple() {
"x86_64-apple-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 libname = format!("rustc{}_rt.{}", channel, name);
let rpath = default_tlib.to_str().expect("non-utf8 component in path");
linker.args(&["-Wl,-rpath", "-Xlinker", rpath]);
linker.link_dylib(Symbol::intern(&libname));
}
"aarch64-fuchsia"
| "aarch64-unknown-linux-gnu"
| "x86_64-fuchsia"
| "x86_64-unknown-linux-gnu" => {
let filename = format!("librustc{}_rt.{}.a", channel, name);
let path = default_tlib.join(&filename);
linker.link_whole_rlib(&path);
}
_ => {}
}
}
/// Returns a boolean indicating whether the specified crate should be ignored
/// during LTO.
///
/// Crates ignored during LTO are not lumped together in the "massive object
/// file" that we create and are linked in their normal rlib states. See
/// comments below for what crates do not participate in LTO.
///
/// It's unusual for a crate to not participate in LTO. Typically only
/// compiler-specific and unstable crates have a reason to not participate in
/// LTO.
pub fn ignored_for_lto(sess: &Session, info: &CrateInfo, cnum: CrateNum) -> bool {
// If our target enables builtin function lowering in LLVM then the
// crates providing these functions don't participate in LTO (e.g.
// no_builtins or compiler builtins crates).
!sess.target.target.options.no_builtins
&& (info.compiler_builtins == Some(cnum) || info.is_no_builtins.contains(&cnum))
}
fn linker_and_flavor(sess: &Session) -> (PathBuf, LinkerFlavor) {
fn infer_from(
sess: &Session,
linker: Option<PathBuf>,
flavor: Option<LinkerFlavor>,
) -> Option<(PathBuf, LinkerFlavor)> {
match (linker, flavor) {
(Some(linker), Some(flavor)) => Some((linker, flavor)),
// only the linker flavor is known; use the default linker for the selected flavor
(None, Some(flavor)) => Some((
PathBuf::from(match flavor {
LinkerFlavor::Em => {
if cfg!(windows) {
"emcc.bat"
} else {
"emcc"
}
}
LinkerFlavor::Gcc => {
if cfg!(any(target_os = "solaris", target_os = "illumos")) {
// On historical Solaris systems, "cc" may have
// been Sun Studio, which is not flag-compatible
// with "gcc". This history casts a long shadow,
// and many modern illumos distributions today
// ship GCC as "gcc" without also making it
// available as "cc".
"gcc"
} else {
"cc"
}
}
LinkerFlavor::Ld => "ld",
LinkerFlavor::Msvc => "link.exe",
LinkerFlavor::Lld(_) => "lld",
LinkerFlavor::PtxLinker => "rust-ptx-linker",
}),
flavor,
)),
(Some(linker), None) => {
let stem = linker.file_stem().and_then(|stem| stem.to_str()).unwrap_or_else(|| {
sess.fatal("couldn't extract file stem from specified linker")
});
let flavor = if stem == "emcc" {
LinkerFlavor::Em
} else if stem == "gcc"
|| stem.ends_with("-gcc")
|| stem == "clang"
|| stem.ends_with("-clang")
{
LinkerFlavor::Gcc
} else if stem == "ld" || stem == "ld.lld" || stem.ends_with("-ld") {
LinkerFlavor::Ld
} else if stem == "link" || stem == "lld-link" {
LinkerFlavor::Msvc
} else if stem == "lld" || stem == "rust-lld" {
LinkerFlavor::Lld(sess.target.target.options.lld_flavor)
} else {
// fall back to the value in the target spec
sess.target.target.linker_flavor
};
Some((linker, flavor))
}
(None, None) => None,
}
}
// linker and linker flavor specified via command line have precedence over what the target
// specification specifies
if let Some(ret) = infer_from(sess, sess.opts.cg.linker.clone(), sess.opts.cg.linker_flavor) {
return ret;
}
if let Some(ret) = infer_from(
sess,
sess.target.target.options.linker.clone().map(PathBuf::from),
Some(sess.target.target.linker_flavor),
) {
return ret;
}
bug!("Not enough information provided to determine how to invoke the linker");
}
/// Returns a boolean indicating whether we should preserve the 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 {
// If the objects don't have debuginfo there's nothing to preserve.
if sess.opts.debuginfo == config::DebugInfo::None {
return false;
}
// If we're only producing artifacts that are archives, no need to preserve
// the objects as they're losslessly contained inside the archives.
let output_linked =
sess.crate_types().iter().any(|&x| x != CrateType::Rlib && x != CrateType::Staticlib);
if !output_linked {
return false;
}
// If we're on OSX then the equivalent of split dwarf is turned on by
// default. The final executable won't actually have any debug information
// except it'll have pointers to elsewhere. Historically we've always run
// `dsymutil` to "link all the dwarf together" but this is actually sort of
// a bummer for incremental compilation! (the whole point of split dwarf is
// that you don't do this sort of dwarf link).
//
// Basically as a result this just means that if we're on OSX and we're
// *not* running dsymutil then the object files are the only source of truth
// for debug information, so we must preserve them.
if sess.target.target.options.is_like_osx {
return !sess.opts.debugging_opts.run_dsymutil;
}
false
}
pub fn archive_search_paths(sess: &Session) -> Vec<PathBuf> {
sess.target_filesearch(PathKind::Native).search_path_dirs()
}
enum RlibFlavor {
Normal,
StaticlibBase,
}
fn print_native_static_libs(sess: &Session, all_native_libs: &[NativeLib]) {
let lib_args: Vec<_> = all_native_libs
.iter()
.filter(|l| relevant_lib(sess, l))
.filter_map(|lib| {
let name = lib.name?;
match lib.kind {
NativeLibKind::StaticNoBundle
| NativeLibKind::Dylib
| NativeLibKind::Unspecified => {
if sess.target.target.options.is_like_msvc {
Some(format!("{}.lib", 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::StaticBundle | NativeLibKind::RawDylib => None,
}
})
.collect();
if !lib_args.is_empty() {
sess.note_without_error(
"Link against the following native artifacts when linking \
against this static library. The order and any duplication \
can be significant on some platforms.",
);
// Prefix for greppability
sess.note_without_error(&format!("native-static-libs: {}", &lib_args.join(" ")));
}
}
// Because windows-gnu target is meant to be self-contained for pure Rust code it bundles
// own mingw-w64 libraries. These libraries are usually not compatible with mingw-w64
// installed in the system. This breaks many cases where Rust is mixed with other languages
// (e.g. *-sys crates).
// We prefer system mingw-w64 libraries if they are available to avoid this issue.
fn get_crt_libs_path(sess: &Session) -> Option<PathBuf> {
fn find_exe_in_path<P>(exe_name: P) -> Option<PathBuf>
where
P: AsRef<Path>,
{
for dir in env::split_paths(&env::var_os("PATH")?) {
let full_path = dir.join(&exe_name);
if full_path.is_file() {
return Some(fix_windows_verbatim_for_gcc(&full_path));
}
}
None
}
fn probe(sess: &Session) -> Option<PathBuf> {
if let (linker, LinkerFlavor::Gcc) = linker_and_flavor(&sess) {
let linker_path = if cfg!(windows) && linker.extension().is_none() {
linker.with_extension("exe")
} else {
linker
};
if let Some(linker_path) = find_exe_in_path(linker_path) {
let mingw_arch = match &sess.target.target.arch {
x if x == "x86" => "i686",
x => x,
};
let mingw_bits = &sess.target.target.target_pointer_width;
let mingw_dir = format!("{}-w64-mingw32", mingw_arch);
// Here we have path/bin/gcc but we need path/
let mut path = linker_path;
path.pop();
path.pop();
// Loosely based on Clang MinGW driver
let probe_paths = vec![
path.join(&mingw_dir).join("lib"), // Typical path
path.join(&mingw_dir).join("sys-root/mingw/lib"), // Rare path
path.join(format!(
"lib/mingw/tools/install/mingw{}/{}/lib",
&mingw_bits, &mingw_dir
)), // Chocolatey is creative
];
for probe_path in probe_paths {
if probe_path.join("crt2.o").exists() {
return Some(probe_path);
};
}
};
};
None
}
let mut system_library_path = sess.system_library_path.borrow_mut();
match &*system_library_path {
Some(Some(compiler_libs_path)) => Some(compiler_libs_path.clone()),
Some(None) => None,
None => {
let path = probe(sess);
*system_library_path = Some(path.clone());
path
}
}
}
fn get_object_file_path(sess: &Session, name: &str, self_contained: bool) -> PathBuf {
// prefer system {,dll}crt2.o libs, see get_crt_libs_path comment for more details
if sess.opts.debugging_opts.link_self_contained.is_none()
&& sess.target.target.llvm_target.contains("windows-gnu")
{
if let Some(compiler_libs_path) = get_crt_libs_path(sess) {
let file_path = compiler_libs_path.join(name);
if file_path.exists() {
return file_path;
}
}
}
let fs = sess.target_filesearch(PathKind::Native);
let file_path = fs.get_lib_path().join(name);
if file_path.exists() {
return file_path;
}
// Special directory with objects used only in self-contained linkage mode
if self_contained {
let file_path = fs.get_self_contained_lib_path().join(name);
if file_path.exists() {
return file_path;
}
}
for search_path in fs.search_paths() {
let file_path = search_path.dir.join(name);
if file_path.exists() {
return file_path;
}
}
PathBuf::from(name)
}
fn exec_linker(
sess: &Session,
cmd: &Command,
out_filename: &Path,
tmpdir: &Path,
) -> io::Result<Output> {
// When attempting to spawn the linker we run a risk of blowing out the
// size limits for spawning a new process with respect to the arguments
// we pass on the command line.
//
// Here we attempt to handle errors from the OS saying "your list of
// arguments is too big" by reinvoking the linker again with an `@`-file
// that contains all the arguments. The theory is that this is then
// accepted on all linkers and the linker will read all its options out of
// there instead of looking at the command line.
if !cmd.very_likely_to_exceed_some_spawn_limit() {
match cmd.command().stdout(Stdio::piped()).stderr(Stdio::piped()).spawn() {
Ok(child) => {
let output = child.wait_with_output();
flush_linked_file(&output, out_filename)?;
return output;
}
Err(ref e) if command_line_too_big(e) => {
info!("command line to linker was too big: {}", e);
}
Err(e) => return Err(e),
}
}
info!("falling back to passing arguments to linker via an @-file");
let mut cmd2 = cmd.clone();
let mut args = String::new();
for arg in cmd2.take_args() {
args.push_str(
&Escape {
arg: arg.to_str().unwrap(),
is_like_msvc: sess.target.target.options.is_like_msvc,
}
.to_string(),
);
args.push_str("\n");
}
let file = tmpdir.join("linker-arguments");
let bytes = if sess.target.target.options.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(unix)]
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)
}
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, false, RelocModel::Pic) => LinkOutputKind::DynamicPicExe,
(CrateType::Executable, false, _) => LinkOutputKind::DynamicNoPicExe,
(CrateType::Executable, true, RelocModel::Pic) => LinkOutputKind::StaticPicExe,
(CrateType::Executable, true, _) => LinkOutputKind::StaticNoPicExe,
(_, true, _) => LinkOutputKind::StaticDylib,
(_, false, _) => LinkOutputKind::DynamicDylib,
};
// Adjust the output kind to target capabilities.
let opts = &sess.target.target.options;
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,
}
}
/// Whether we link to our own CRT objects instead of relying on gcc to pull them.
/// We only provide such support for a very limited number of targets.
fn crt_objects_fallback(sess: &Session, crate_type: CrateType) -> bool {
if let Some(self_contained) = sess.opts.debugging_opts.link_self_contained {
return self_contained;
}
match sess.target.target.options.crt_objects_fallback {
// FIXME: Find a better heuristic for "native musl toolchain is available",
// based on host and linker path, for example.
// (https://github.com/rust-lang/rust/pull/71769#issuecomment-626330237).
Some(CrtObjectsFallback::Musl) => sess.crt_static(Some(crate_type)),
// FIXME: Find some heuristic for "native mingw toolchain is available",
// likely based on `get_crt_libs_path` (https://github.com/rust-lang/rust/pull/67429).
Some(CrtObjectsFallback::Mingw) => sess.target.target.target_vendor != "uwp",
// FIXME: Figure out cases in which WASM needs to link with a native toolchain.
Some(CrtObjectsFallback::Wasm) => true,
None => false,
}
}
/// Add pre-link object files defined by the target spec.
fn add_pre_link_objects(
cmd: &mut dyn Linker,
sess: &Session,
link_output_kind: LinkOutputKind,
self_contained: bool,
) {
let opts = &sess.target.target.options;
let objects =
if self_contained { &opts.pre_link_objects_fallback } else { &opts.pre_link_objects };
for obj in objects.get(&link_output_kind).iter().copied().flatten() {
cmd.add_object(&get_object_file_path(sess, obj, self_contained));
}
}
/// Add post-link object files defined by the target spec.
fn add_post_link_objects(
cmd: &mut dyn Linker,
sess: &Session,
link_output_kind: LinkOutputKind,
self_contained: bool,
) {
let opts = &sess.target.target.options;
let objects =
if self_contained { &opts.post_link_objects_fallback } else { &opts.post_link_objects };
for obj in objects.get(&link_output_kind).iter().copied().flatten() {
cmd.add_object(&get_object_file_path(sess, obj, self_contained));
}
}
/// Add arbitrary "pre-link" args defined by the target spec or from command line.
/// FIXME: Determine where exactly these args need to be inserted.
fn add_pre_link_args(cmd: &mut dyn Linker, sess: &Session, flavor: LinkerFlavor) {
if let Some(args) = sess.target.target.options.pre_link_args.get(&flavor) {
cmd.args(args);
}
cmd.args(&sess.opts.debugging_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.target.options.link_script) {
(CrateType::Cdylib | CrateType::Executable, Some(script)) => {
if !sess.target.target.options.linker_is_gnu {
sess.fatal("can only use link script when linking with GNU-like linker");
}
let file_name = ["rustc", &sess.target.target.llvm_target, "linkfile.ld"].join("-");
let path = tmpdir.join(file_name);
if let Err(e) = fs::write(&path, script) {
sess.fatal(&format!("failed to write link script to {}: {}", path.display(), e));
}
cmd.arg("--script");
cmd.arg(path);
}
_ => {}
}
}
/// Add arbitrary "user defined" args defined from command line and by `#[link_args]` attributes.
/// FIXME: Determine where exactly these args need to be inserted.
fn add_user_defined_link_args(
cmd: &mut dyn Linker,
sess: &Session,
codegen_results: &CodegenResults,
) {
cmd.args(&sess.opts.cg.link_args);
cmd.args(&*codegen_results.crate_info.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,
) {
if let Some(args) = sess.target.target.options.late_link_args.get(&flavor) {
cmd.args(args);
}
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.target.options.late_link_args_dynamic.get(&flavor) {
cmd.args(args);
}
} else {
if let Some(args) = sess.target.target.options.late_link_args_static.get(&flavor) {
cmd.args(args);
}
}
}
/// 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.target.options.post_link_args.get(&flavor) {
cmd.args(args);
}
}
/// Add object files containing code from the current crate.
fn add_local_crate_regular_objects(cmd: &mut dyn Linker, codegen_results: &CodegenResults) {
for obj in codegen_results.modules.iter().filter_map(|m| m.object.as_ref()) {
cmd.add_object(obj);
}
}
/// Add object files for allocator code linked once for the whole crate tree.
fn add_local_crate_allocator_objects(cmd: &mut dyn Linker, codegen_results: &CodegenResults) {
if let Some(obj) = codegen_results.allocator_module.as_ref().and_then(|m| m.object.as_ref()) {
cmd.add_object(obj);
}
}
/// Add object files containing metadata for the current crate.
fn add_local_crate_metadata_objects(
cmd: &mut dyn Linker,
crate_type: CrateType,
codegen_results: &CodegenResults,
) {
// When linking a dynamic library, we put the metadata into a section of the
// executable. This metadata is in a separate object file from the main
// object file, so we link that in here.
if crate_type == CrateType::Dylib || crate_type == CrateType::ProcMacro {
if let Some(obj) = codegen_results.metadata_module.as_ref().and_then(|m| m.object.as_ref())
{
cmd.add_object(obj);
}
}
}
/// Link native libraries corresponding to the current crate and all libraries corresponding to
/// all its dependency crates.
/// FIXME: Consider combining this with the functions above adding object files for the local crate.
fn link_local_crate_native_libs_and_dependent_crate_libs<'a, B: ArchiveBuilder<'a>>(
cmd: &mut dyn Linker,
sess: &'a Session,
crate_type: CrateType,
codegen_results: &CodegenResults,
tmpdir: &Path,
) {
// 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 allowed 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're only dylibs and dylibs can only depend
// on other dylibs (e.g., other native deps).
//
// If -Zlink-native-libraries=false is set, then the assumption is that an
// external build system already has the native dependencies defined, and it
// will provide them to the linker itself.
if sess.opts.debugging_opts.link_native_libraries {
add_local_native_libraries(cmd, sess, codegen_results);
}
add_upstream_rust_crates::<B>(cmd, sess, codegen_results, crate_type, tmpdir);
if sess.opts.debugging_opts.link_native_libraries {
add_upstream_native_libraries(cmd, sess, codegen_results, crate_type);
}
}
/// Add sysroot and other globally set directories to the directory search list.
fn add_library_search_dirs(cmd: &mut dyn Linker, sess: &Session, self_contained: bool) {
// Prefer system mingw-w64 libs, see get_crt_libs_path comment for more details.
if sess.opts.debugging_opts.link_self_contained.is_none()
&& cfg!(windows)
&& sess.target.target.llvm_target.contains("windows-gnu")
{
if let Some(compiler_libs_path) = get_crt_libs_path(sess) {
cmd.include_path(&compiler_libs_path);
}
}
// The default library location, we need this to find the runtime.
// The location of crates will be determined as needed.
let lib_path = sess.target_filesearch(PathKind::All).get_lib_path();
cmd.include_path(&fix_windows_verbatim_for_gcc(&lib_path));
// Special directory with libraries used only in self-contained linkage mode
if self_contained {
let lib_path = sess.target_filesearch(PathKind::All).get_self_contained_lib_path();
cmd.include_path(&fix_windows_verbatim_for_gcc(&lib_path));
}
}
/// Add options making relocation sections in the produced ELF files read-only
/// and suppressing lazy binding.
fn add_relro_args(cmd: &mut dyn Linker, sess: &Session) {
match sess.opts.debugging_opts.relro_level.unwrap_or(sess.target.target.options.relro_level) {
RelroLevel::Full => cmd.full_relro(),
RelroLevel::Partial => cmd.partial_relro(),
RelroLevel::Off => cmd.no_relro(),
RelroLevel::None => {}
}
}
/// Add library search paths used at runtime by dynamic linkers.
fn add_rpath_args(
cmd: &mut dyn Linker,
sess: &Session,
codegen_results: &CodegenResults,
out_filename: &Path,
) {
// FIXME (#2397): At some point we want to rpath our guesses as to
// where extern libraries might live, based on the
// addl_lib_search_paths
if sess.opts.cg.rpath {
let target_triple = sess.opts.target_triple.triple();
let mut get_install_prefix_lib_path = || {
let install_prefix = option_env!("CFG_PREFIX").expect("CFG_PREFIX");
let tlib = filesearch::relative_target_lib_path(&sess.sysroot, target_triple);
let mut path = PathBuf::from(install_prefix);
path.push(&tlib);
path
};
let mut rpath_config = RPathConfig {
used_crates: &codegen_results.crate_info.used_crates_dynamic,
out_filename: out_filename.to_path_buf(),
has_rpath: sess.target.target.options.has_rpath,
is_like_osx: sess.target.target.options.is_like_osx,
linker_is_gnu: sess.target.target.options.linker_is_gnu,
get_install_prefix_lib_path: &mut get_install_prefix_lib_path,
};
cmd.args(&rpath::get_rpath_flags(&mut rpath_config));
}
}
/// Produce the linker command line containing linker path and arguments.
/// `NO-OPT-OUT` marks the arguments that cannot be removed from the command line
/// by the user without creating a custom target specification.
/// `OBJECT-FILES` specify whether the arguments can add object files.
/// `CUSTOMIZATION-POINT` means that arbitrary arguments defined by the user
/// or by the target spec can be inserted here.
/// `AUDIT-ORDER` - need to figure out whether the option is order-dependent or not.
fn linker_with_args<'a, B: ArchiveBuilder<'a>>(
path: &Path,
flavor: LinkerFlavor,
sess: &'a Session,
crate_type: CrateType,
tmpdir: &Path,
out_filename: &Path,
codegen_results: &CodegenResults,
target_cpu: &str,
) -> Command {
let crt_objects_fallback = crt_objects_fallback(sess, crate_type);
let base_cmd = get_linker(sess, path, flavor, crt_objects_fallback);
// FIXME: Move `/LIBPATH` addition for uwp targets from the linker construction
// to the linker args construction.
assert!(base_cmd.get_args().is_empty() || sess.target.target.target_vendor == "uwp");
let cmd = &mut *codegen_results.linker_info.to_linker(base_cmd, &sess, flavor, target_cpu);
let link_output_kind = link_output_kind(sess, crate_type);
// NO-OPT-OUT, OBJECT-FILES-MAYBE, CUSTOMIZATION-POINT
add_pre_link_args(cmd, sess, flavor);
// NO-OPT-OUT
add_link_script(cmd, sess, tmpdir, crate_type);
// NO-OPT-OUT, OBJECT-FILES-NO, AUDIT-ORDER
if sess.target.target.options.is_like_fuchsia && crate_type == CrateType::Executable {
let prefix = if sess.opts.debugging_opts.sanitizer.contains(SanitizerSet::ADDRESS) {
"asan/"
} else {
""
};
cmd.arg(format!("--dynamic-linker={}ld.so.1", prefix));
}
// NO-OPT-OUT, OBJECT-FILES-NO, AUDIT-ORDER
cmd.add_eh_frame_header();
// NO-OPT-OUT, OBJECT-FILES-NO
if crt_objects_fallback {
cmd.no_crt_objects();
}
// NO-OPT-OUT, OBJECT-FILES-YES
add_pre_link_objects(cmd, sess, link_output_kind, crt_objects_fallback);
// NO-OPT-OUT, OBJECT-FILES-NO, AUDIT-ORDER
if sess.target.target.options.is_like_emscripten {
cmd.arg("-s");
cmd.arg(if sess.panic_strategy() == PanicStrategy::Abort {
"DISABLE_EXCEPTION_CATCHING=1"
} else {
"DISABLE_EXCEPTION_CATCHING=0"
});
}
// OBJECT-FILES-YES, AUDIT-ORDER
link_sanitizers(sess, crate_type, cmd);
// OBJECT-FILES-NO, AUDIT-ORDER
// Linker plugins should be specified early in the list of arguments
// FIXME: How "early" exactly?
cmd.linker_plugin_lto();
// NO-OPT-OUT, OBJECT-FILES-NO, AUDIT-ORDER
// FIXME: Order-dependent, at least relatively to other args adding searh directories.
add_library_search_dirs(cmd, sess, crt_objects_fallback);
// OBJECT-FILES-YES
add_local_crate_regular_objects(cmd, codegen_results);
// NO-OPT-OUT, OBJECT-FILES-NO, AUDIT-ORDER
cmd.output_filename(out_filename);
// OBJECT-FILES-NO, AUDIT-ORDER
if crate_type == CrateType::Executable && sess.target.target.options.is_like_windows {
if let Some(ref s) = codegen_results.windows_subsystem {
cmd.subsystem(s);
}
}
// NO-OPT-OUT, OBJECT-FILES-NO, AUDIT-ORDER
// 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.
cmd.export_symbols(tmpdir, crate_type);
// OBJECT-FILES-YES
add_local_crate_metadata_objects(cmd, crate_type, codegen_results);
// OBJECT-FILES-YES
add_local_crate_allocator_objects(cmd, codegen_results);
// OBJECT-FILES-NO, AUDIT-ORDER
// FIXME: Order dependent, applies to the following objects. Where should it be placed?
// Try to strip as much out of the generated object by removing unused
// sections if possible. See more comments in linker.rs
if !sess.opts.cg.link_dead_code {
let keep_metadata = crate_type == CrateType::Dylib;
cmd.gc_sections(keep_metadata);
}
// NO-OPT-OUT, OBJECT-FILES-NO, AUDIT-ORDER
cmd.set_output_kind(link_output_kind, out_filename);
// OBJECT-FILES-NO, AUDIT-ORDER
add_relro_args(cmd, sess);
// OBJECT-FILES-NO, AUDIT-ORDER
// Pass optimization flags down to the linker.
cmd.optimize();
// OBJECT-FILES-NO, AUDIT-ORDER
// Pass debuginfo and strip flags down to the linker.
cmd.debuginfo(sess.opts.debugging_opts.strip);
// OBJECT-FILES-NO, AUDIT-ORDER
// 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.target.options.no_default_libraries {
cmd.no_default_libraries();
}
// OBJECT-FILES-YES
link_local_crate_native_libs_and_dependent_crate_libs::<B>(
cmd,
sess,
crate_type,
codegen_results,
tmpdir,
);
// OBJECT-FILES-NO, AUDIT-ORDER
if sess.opts.cg.profile_generate.enabled() {
cmd.pgo_gen();
}
// OBJECT-FILES-NO, AUDIT-ORDER
if sess.opts.debugging_opts.control_flow_guard != CFGuard::Disabled {
cmd.control_flow_guard();
}
// OBJECT-FILES-NO, AUDIT-ORDER
add_rpath_args(cmd, sess, codegen_results, out_filename);
// OBJECT-FILES-MAYBE, CUSTOMIZATION-POINT
add_user_defined_link_args(cmd, sess, codegen_results);
// NO-OPT-OUT, OBJECT-FILES-NO, AUDIT-ORDER
cmd.finalize();
// NO-OPT-OUT, OBJECT-FILES-MAYBE, CUSTOMIZATION-POINT
add_late_link_args(cmd, sess, flavor, crate_type, codegen_results);
// NO-OPT-OUT, OBJECT-FILES-YES
add_post_link_objects(cmd, sess, link_output_kind, crt_objects_fallback);
// NO-OPT-OUT, OBJECT-FILES-MAYBE, CUSTOMIZATION-POINT
add_post_link_args(cmd, sess, flavor);
cmd.take_cmd()
}
// # Native library linking
//
// User-supplied library search paths (-L on the command line). These are
// the same paths used to find Rust crates, so some of them may have been
// added already by the previous crate linking code. This only allows them
// to be found at compile time so it is still entirely up to outside
// forces to make sure that library can be found at runtime.
//
// Also note that the native libraries linked here are only the ones located
// in the current crate. Upstream crates with native library dependencies
// may have their native library pulled in above.
fn add_local_native_libraries(
cmd: &mut dyn Linker,
sess: &Session,
codegen_results: &CodegenResults,
) {
let filesearch = sess.target_filesearch(PathKind::All);
for search_path in filesearch.search_paths() {
match search_path.kind {
PathKind::Framework => {
cmd.framework_path(&search_path.dir);
}
_ => {
cmd.include_path(&fix_windows_verbatim_for_gcc(&search_path.dir));
}
}
}
let relevant_libs =
codegen_results.crate_info.used_libraries.iter().filter(|l| relevant_lib(sess, l));
let search_path = archive_search_paths(sess);
for lib in relevant_libs {
let name = match lib.name {
Some(l) => l,
None => continue,
};
match lib.kind {
NativeLibKind::Dylib | NativeLibKind::Unspecified => cmd.link_dylib(name),
NativeLibKind::Framework => cmd.link_framework(name),
NativeLibKind::StaticNoBundle => cmd.link_staticlib(name),
NativeLibKind::StaticBundle => cmd.link_whole_staticlib(name, &search_path),
NativeLibKind::RawDylib => {
// FIXME(#58713): Proper handling for raw dylibs.
bug!("raw_dylib feature not yet implemented");
}
}
}
}
// # Rust Crate linking
//
// Rust crates are not considered at all when creating an rlib output. All
// dependencies will be linked when producing the final output (instead of
// the intermediate rlib version)
fn add_upstream_rust_crates<'a, B: ArchiveBuilder<'a>>(
cmd: &mut dyn Linker,
sess: &'a Session,
codegen_results: &CodegenResults,
crate_type: CrateType,
tmpdir: &Path,
) {
// All of the heavy lifting has previously been accomplished by the
// dependency_format module of the compiler. This is just crawling the
// output of that module, adding crates as necessary.
//
// Linking to a rlib involves just passing it to the linker (the linker
// will slurp up the object files inside), and linking to a dynamic library
// involves just passing the right -l flag.
let (_, data) = codegen_results
.crate_info
.dependency_formats
.iter()
.find(|(ty, _)| *ty == crate_type)
.expect("failed to find crate type in dependency format list");
// Invoke get_used_crates to ensure that we get a topological sorting of
// crates.
let deps = &codegen_results.crate_info.used_crates_dynamic;
// There's a few internal crates in the standard library (aka libcore and
// libstd) which actually have a circular dependence upon one another. This
// currently arises through "weak lang items" where libcore requires things
// like `rust_begin_unwind` but libstd ends up defining it. To get this
// circular dependence to work correctly in all situations we'll need to be
// sure to correctly apply the `--start-group` and `--end-group` options to
// GNU linkers, otherwise if we don't use any other symbol from the standard
// library it'll get discarded and the whole application won't link.
//
// In this loop we're calculating the `group_end`, after which crate to
// pass `--end-group` and `group_start`, before which crate to pass
// `--start-group`. We currently do this by passing `--end-group` after
// the first crate (when iterating backwards) that requires a lang item
// defined somewhere else. Once that's set then when we've defined all the
// necessary lang items we'll pass `--start-group`.
//
// Note that this isn't amazing logic for now but it should do the trick
// for the current implementation of the standard library.
let mut group_end = None;
let mut group_start = None;
// Crates available for linking thus far.
let mut available = FxHashSet::default();
// Crates required to satisfy dependencies discovered so far.
let mut required = FxHashSet::default();
let info = &codegen_results.crate_info;
for &(cnum, _) in deps.iter().rev() {
if let Some(missing) = info.missing_lang_items.get(&cnum) {
let missing_crates = missing.iter().map(|i| info.lang_item_to_crate.get(i).copied());
required.extend(missing_crates);
}
required.insert(Some(cnum));
available.insert(Some(cnum));
if required.len() > available.len() && group_end.is_none() {
group_end = Some(cnum);
}
if required.len() == available.len() && group_end.is_some() {
group_start = Some(cnum);
break;
}
}
// If we didn't end up filling in all lang items from upstream crates then
// we'll be filling it in with our crate. This probably means we're the
// standard library itself, so skip this for now.
if group_end.is_some() && group_start.is_none() {
group_end = None;
}
let mut compiler_builtins = None;
for &(cnum, _) in deps.iter() {
if group_start == Some(cnum) {
cmd.group_start();
}
// We may not pass all crates through to the linker. Some crates may
// appear statically in an existing dylib, meaning we'll pick up all the
// symbols from the dylib.
let src = &codegen_results.crate_info.used_crate_source[&cnum];
match data[cnum.as_usize() - 1] {
_ if codegen_results.crate_info.profiler_runtime == Some(cnum) => {
add_static_crate::<B>(cmd, sess, codegen_results, tmpdir, crate_type, cnum);
}
// compiler-builtins are always placed last to ensure that they're
// linked correctly.
_ if codegen_results.crate_info.compiler_builtins == Some(cnum) => {
assert!(compiler_builtins.is_none());
compiler_builtins = Some(cnum);
}
Linkage::NotLinked | Linkage::IncludedFromDylib => {}
Linkage::Static => {
add_static_crate::<B>(cmd, sess, codegen_results, tmpdir, crate_type, cnum);
}
Linkage::Dynamic => add_dynamic_crate(cmd, sess, &src.dylib.as_ref().unwrap().0),
}
if group_end == Some(cnum) {
cmd.group_end();
}
}
// compiler-builtins are always placed last to ensure that they're
// linked correctly.
// We must always link the `compiler_builtins` crate statically. Even if it
// was already "included" in a dylib (e.g., `libstd` when `-C prefer-dynamic`
// is used)
if let Some(cnum) = compiler_builtins {
add_static_crate::<B>(cmd, sess, codegen_results, tmpdir, crate_type, cnum);
}
// Converts a library file-stem into a cc -l argument
fn unlib<'a>(config: &config::Config, stem: &'a str) -> &'a str {
if stem.starts_with("lib") && !config.target.options.is_like_windows {
&stem[3..]
} else {
stem
}
}
// Adds the static "rlib" versions of all crates to the command line.
// There's a bit of magic which happens here specifically related to LTO and
// dynamic libraries. Specifically:
//
// * For LTO, we remove upstream object files.
// * For dylibs we remove metadata and bytecode from upstream rlibs
//
// 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.
//
// When making a dynamic library, linkers by default don't include any
// object files in an archive if they're not necessary to resolve the link.
// We basically want to convert the archive (rlib) to a dylib, though, so we
// *do* want everything included in the output, regardless of whether the
// linker thinks it's needed or not. As a result we must use the
// --whole-archive option (or the platform equivalent). When using this
// option the linker will fail if there are non-objects in the archive (such
// as our own metadata and/or bytecode). All in all, for rlibs to be
// entirely included in dylibs, we need to remove all non-object files.
//
// Note, however, that if we're not doing LTO or we're not producing a dylib
// (aka we're making an executable), we can just pass the rlib blindly to
// the linker (fast) because it's fine if it's not actually included as
// we're at the end of the dependency chain.
fn add_static_crate<'a, B: ArchiveBuilder<'a>>(
cmd: &mut dyn Linker,
sess: &'a Session,
codegen_results: &CodegenResults,
tmpdir: &Path,
crate_type: CrateType,
cnum: CrateNum,
) {
let src = &codegen_results.crate_info.used_crate_source[&cnum];
let cratepath = &src.rlib.as_ref().unwrap().0;
// See the comment above in `link_staticlib` and `link_rlib` for why if
// there's a static library that's not relevant we skip all object
// files.
let native_libs = &codegen_results.crate_info.native_libraries[&cnum];
let skip_native = native_libs
.iter()
.any(|lib| lib.kind == NativeLibKind::StaticBundle && !relevant_lib(sess, lib));
if (!are_upstream_rust_objects_already_included(sess)
|| ignored_for_lto(sess, &codegen_results.crate_info, cnum))
&& crate_type != CrateType::Dylib
&& !skip_native
{
cmd.link_rlib(&fix_windows_verbatim_for_gcc(cratepath));
return;
}
let dst = tmpdir.join(cratepath.file_name().unwrap());
let name = cratepath.file_name().unwrap().to_str().unwrap();
let name = &name[3..name.len() - 5]; // chop off lib/.rlib
sess.prof.generic_activity_with_arg("link_altering_rlib", name).run(|| {
let mut archive = <B as ArchiveBuilder>::new(sess, &dst, Some(cratepath));
archive.update_symbols();
let mut any_objects = false;
for f in archive.src_files() {
if f == METADATA_FILENAME {
archive.remove_file(&f);
continue;
}
let canonical = f.replace("-", "_");
let canonical_name = name.replace("-", "_");
let is_rust_object =
canonical.starts_with(&canonical_name) && looks_like_rust_object_file(&f);
// If we've been requested to skip all native object files
// (those not generated by the rust compiler) then we can skip
// this file. See above for why we may want to do this.
let skip_because_cfg_say_so = skip_native && !is_rust_object;
// If we're performing LTO and this is a rust-generated object
// file, then we don't need the object file as it's part of the
// LTO module. Note that `#![no_builtins]` is excluded from LTO,
// though, so we let that object file slide.
let skip_because_lto = are_upstream_rust_objects_already_included(sess)
&& is_rust_object
&& (sess.target.target.options.no_builtins
|| !codegen_results.crate_info.is_no_builtins.contains(&cnum));
if skip_because_cfg_say_so || skip_because_lto {
archive.remove_file(&f);
} else {
any_objects = true;
}
}
if !any_objects {
return;
}
archive.build();
// If we're creating a dylib, then we need to include the
// whole of each object in our archive into that artifact. This is
// because a `dylib` can be reused as an intermediate artifact.
//
// Note, though, that we don't want to include the whole of a
// compiler-builtins crate (e.g., compiler-rt) because it'll get
// repeatedly linked anyway.
if crate_type == CrateType::Dylib
&& codegen_results.crate_info.compiler_builtins != Some(cnum)
{
cmd.link_whole_rlib(&fix_windows_verbatim_for_gcc(&dst));
} else {
cmd.link_rlib(&fix_windows_verbatim_for_gcc(&dst));
}
});
}
// Same thing as above, but for dynamic crates instead of static crates.
fn add_dynamic_crate(cmd: &mut dyn Linker, sess: &Session, cratepath: &Path) {
// Just need to tell the linker about where the library lives and
// what its name is
let parent = cratepath.parent();
if let Some(dir) = parent {
cmd.include_path(&fix_windows_verbatim_for_gcc(dir));
}
let filestem = cratepath.file_stem().unwrap().to_str().unwrap();
cmd.link_rust_dylib(
Symbol::intern(&unlib(&sess.target, filestem)),
parent.unwrap_or(Path::new("")),
);
}
}
// Link in all of our upstream crates' native dependencies. Remember that
// all of these upstream native dependencies are all non-static
// dependencies. We've got two cases then:
//
// 1. The upstream crate is an rlib. In this case we *must* link in the
// native dependency because the rlib is just an archive.
//
// 2. The upstream crate is a dylib. In order to use the dylib, we have to
// have the dependency present on the system somewhere. Thus, we don't
// gain a whole lot from not linking in the dynamic dependency to this
// crate as well.
//
// The use case for this is a little subtle. In theory the native
// dependencies of a crate are purely an implementation detail of the crate
// itself, but the problem arises with generic and inlined functions. If a
// generic function calls a native function, then the generic function must
// be instantiated in the target crate, meaning that the native symbol must
// also be resolved in the target crate.
fn add_upstream_native_libraries(
cmd: &mut dyn Linker,
sess: &Session,
codegen_results: &CodegenResults,
crate_type: CrateType,
) {
// Be sure to use a topological sorting of crates because there may be
// interdependencies between native libraries. When passing -nodefaultlibs,
// for example, almost all native libraries depend on libc, so we have to
// make sure that's all the way at the right (liblibc is near the base of
// the dependency chain).
//
// This passes RequireStatic, but the actual requirement doesn't matter,
// we're just getting an ordering of crate numbers, we're not worried about
// the paths.
let (_, data) = codegen_results
.crate_info
.dependency_formats
.iter()
.find(|(ty, _)| *ty == crate_type)
.expect("failed to find crate type in dependency format list");
let crates = &codegen_results.crate_info.used_crates_static;
for &(cnum, _) in crates {
for lib in codegen_results.crate_info.native_libraries[&cnum].iter() {
let name = match lib.name {
Some(l) => l,
None => continue,
};
if !relevant_lib(sess, &lib) {
continue;
}
match lib.kind {
NativeLibKind::Dylib | NativeLibKind::Unspecified => cmd.link_dylib(name),
NativeLibKind::Framework => cmd.link_framework(name),
NativeLibKind::StaticNoBundle => {
// Link "static-nobundle" native libs only if the crate they originate from
// is being linked statically to the current crate. If it's linked dynamically
// or is an rlib already included via some other dylib crate, the symbols from
// native libs will have already been included in that dylib.
if data[cnum.as_usize() - 1] == Linkage::Static {
cmd.link_staticlib(name)
}
}
// ignore statically included native libraries here as we've
// already included them when we included the rust library
// previously
NativeLibKind::StaticBundle => {}
NativeLibKind::RawDylib => {
// FIXME(#58713): Proper handling for raw dylibs.
bug!("raw_dylib feature not yet implemented");
}
}
}
}
}
fn relevant_lib(sess: &Session, lib: &NativeLib) -> bool {
match lib.cfg {
Some(ref cfg) => rustc_attr::cfg_matches(cfg, &sess.parse_sess, None),
None => true,
}
}
fn are_upstream_rust_objects_already_included(sess: &Session) -> bool {
match sess.lto() {
config::Lto::Fat => true,
config::Lto::Thin => {
// If we defer LTO to the linker, we haven't run LTO ourselves, so
// any upstream object files have not been copied yet.
!sess.opts.cg.linker_plugin_lto.enabled()
}
config::Lto::No | config::Lto::ThinLocal => false,
}
}