637 lines
27 KiB
Rust
637 lines
27 KiB
Rust
//! All functions here are copied from https://github.com/rust-lang/rust/blob/942864a000efd74b73e36bda5606b2cdb55ecf39/src/librustc_codegen_llvm/back/link.rs
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use std::fmt;
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use std::fs;
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use std::io;
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use std::iter;
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use std::path::{Path, PathBuf};
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use std::process::{Output, Stdio};
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use log::info;
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use rustc::middle::cstore::{NativeLibrary, NativeLibraryKind};
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use rustc::middle::dependency_format::Linkage;
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use rustc::session::config::{self, OutputType, RUST_CGU_EXT};
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use rustc::session::search_paths::PathKind;
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use rustc::session::Session;
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use rustc::util::common::time;
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use rustc_codegen_ssa::back::command::Command;
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use rustc_codegen_ssa::back::linker::*;
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use rustc_codegen_ssa::back::link::*;
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use rustc_data_structures::fx::FxHashSet;
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use rustc_fs_util::fix_windows_verbatim_for_gcc;
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use syntax::attr;
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use crate::prelude::*;
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use crate::archive::{ArchiveBuilder, ArchiveConfig};
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use crate::metadata::METADATA_FILENAME;
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// cg_clif doesn't have bytecode, so this is just a dummy
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const RLIB_BYTECODE_EXTENSION: &str = ".cg_clif_bytecode_dummy";
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fn archive_search_paths(sess: &Session) -> Vec<PathBuf> {
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sess.target_filesearch(PathKind::Native).search_path_dirs()
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}
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fn archive_config<'a>(sess: &'a Session,
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output: &Path,
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input: Option<&Path>) -> ArchiveConfig<'a> {
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ArchiveConfig {
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sess,
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dst: output.to_path_buf(),
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src: input.map(|p| p.to_path_buf()),
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lib_search_paths: archive_search_paths(sess),
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}
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}
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pub fn exec_linker(sess: &Session, cmd: &mut Command, out_filename: &Path, tmpdir: &Path)
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-> io::Result<Output>
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{
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// When attempting to spawn the linker we run a risk of blowing out the
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// size limits for spawning a new process with respect to the arguments
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// we pass on the command line.
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//
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// Here we attempt to handle errors from the OS saying "your list of
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// arguments is too big" by reinvoking the linker again with an `@`-file
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// that contains all the arguments. The theory is that this is then
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// accepted on all linkers and the linker will read all its options out of
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// there instead of looking at the command line.
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if !cmd.very_likely_to_exceed_some_spawn_limit() {
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match cmd.command().stdout(Stdio::piped()).stderr(Stdio::piped()).spawn() {
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Ok(child) => {
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let output = child.wait_with_output();
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flush_linked_file(&output, out_filename)?;
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return output;
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}
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Err(ref e) if command_line_too_big(e) => {
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info!("command line to linker was too big: {}", e);
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}
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Err(e) => return Err(e)
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}
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}
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info!("falling back to passing arguments to linker via an @-file");
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let mut cmd2 = cmd.clone();
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let mut args = String::new();
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for arg in cmd2.take_args() {
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args.push_str(&Escape {
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arg: arg.to_str().unwrap(),
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is_like_msvc: sess.target.target.options.is_like_msvc,
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}.to_string());
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args.push_str("\n");
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}
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let file = tmpdir.join("linker-arguments");
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let bytes = if sess.target.target.options.is_like_msvc {
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let mut out = Vec::with_capacity((1 + args.len()) * 2);
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// start the stream with a UTF-16 BOM
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for c in iter::once(0xFEFF).chain(args.encode_utf16()) {
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// encode in little endian
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out.push(c as u8);
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out.push((c >> 8) as u8);
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}
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out
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} else {
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args.into_bytes()
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};
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fs::write(&file, &bytes)?;
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cmd2.arg(format!("@{}", file.display()));
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info!("invoking linker {:?}", cmd2);
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let output = cmd2.output();
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flush_linked_file(&output, out_filename)?;
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return output;
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#[cfg(unix)]
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fn flush_linked_file(_: &io::Result<Output>, _: &Path) -> io::Result<()> {
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Ok(())
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}
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#[cfg(windows)]
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fn flush_linked_file(command_output: &io::Result<Output>, out_filename: &Path)
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-> io::Result<()>
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{
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// On Windows, under high I/O load, output buffers are sometimes not flushed,
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// even long after process exit, causing nasty, non-reproducible output bugs.
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//
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// File::sync_all() calls FlushFileBuffers() down the line, which solves the problem.
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//
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// А full writeup of the original Chrome bug can be found at
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// randomascii.wordpress.com/2018/02/25/compiler-bug-linker-bug-windows-kernel-bug/amp
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if let &Ok(ref out) = command_output {
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if out.status.success() {
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if let Ok(of) = fs::OpenOptions::new().write(true).open(out_filename) {
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of.sync_all()?;
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}
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}
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}
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Ok(())
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}
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#[cfg(unix)]
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fn command_line_too_big(err: &io::Error) -> bool {
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err.raw_os_error() == Some(::libc::E2BIG)
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}
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#[cfg(windows)]
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fn command_line_too_big(err: &io::Error) -> bool {
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const ERROR_FILENAME_EXCED_RANGE: i32 = 206;
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err.raw_os_error() == Some(ERROR_FILENAME_EXCED_RANGE)
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}
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struct Escape<'a> {
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arg: &'a str,
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is_like_msvc: bool,
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}
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impl<'a> fmt::Display for Escape<'a> {
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fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
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if self.is_like_msvc {
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// This is "documented" at
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// https://msdn.microsoft.com/en-us/library/4xdcbak7.aspx
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//
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// Unfortunately there's not a great specification of the
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// syntax I could find online (at least) but some local
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// testing showed that this seemed sufficient-ish to catch
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// at least a few edge cases.
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write!(f, "\"")?;
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for c in self.arg.chars() {
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match c {
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'"' => write!(f, "\\{}", c)?,
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c => write!(f, "{}", c)?,
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}
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}
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write!(f, "\"")?;
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} else {
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// This is documented at https://linux.die.net/man/1/ld, namely:
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//
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// > Options in file are separated by whitespace. A whitespace
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// > character may be included in an option by surrounding the
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// > entire option in either single or double quotes. Any
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// > character (including a backslash) may be included by
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// > prefixing the character to be included with a backslash.
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//
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// We put an argument on each line, so all we need to do is
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// ensure the line is interpreted as one whole argument.
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for c in self.arg.chars() {
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match c {
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'\\' |
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' ' => write!(f, "\\{}", c)?,
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c => write!(f, "{}", c)?,
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}
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}
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}
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Ok(())
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}
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}
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}
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// # Rust Crate linking
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//
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// Rust crates are not considered at all when creating an rlib output. All
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// dependencies will be linked when producing the final output (instead of
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// the intermediate rlib version)
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pub fn add_upstream_rust_crates(cmd: &mut dyn Linker,
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sess: &Session,
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codegen_results: &CodegenResults,
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crate_type: config::CrateType,
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tmpdir: &Path) {
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// All of the heavy lifting has previously been accomplished by the
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// dependency_format module of the compiler. This is just crawling the
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// output of that module, adding crates as necessary.
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//
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// Linking to a rlib involves just passing it to the linker (the linker
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// will slurp up the object files inside), and linking to a dynamic library
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// involves just passing the right -l flag.
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let formats = sess.dependency_formats.borrow();
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let data = formats.get(&crate_type).unwrap();
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// Invoke get_used_crates to ensure that we get a topological sorting of
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// crates.
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let deps = &codegen_results.crate_info.used_crates_dynamic;
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// There's a few internal crates in the standard library (aka libcore and
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// libstd) which actually have a circular dependence upon one another. This
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// currently arises through "weak lang items" where libcore requires things
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// like `rust_begin_unwind` but libstd ends up defining it. To get this
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// circular dependence to work correctly in all situations we'll need to be
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// sure to correctly apply the `--start-group` and `--end-group` options to
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// GNU linkers, otherwise if we don't use any other symbol from the standard
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// library it'll get discarded and the whole application won't link.
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//
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// In this loop we're calculating the `group_end`, after which crate to
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// pass `--end-group` and `group_start`, before which crate to pass
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// `--start-group`. We currently do this by passing `--end-group` after
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// the first crate (when iterating backwards) that requires a lang item
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// defined somewhere else. Once that's set then when we've defined all the
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// necessary lang items we'll pass `--start-group`.
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//
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// Note that this isn't amazing logic for now but it should do the trick
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// for the current implementation of the standard library.
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let mut group_end = None;
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let mut group_start = None;
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let mut end_with = FxHashSet::default();
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let info = &codegen_results.crate_info;
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for &(cnum, _) in deps.iter().rev() {
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if let Some(missing) = info.missing_lang_items.get(&cnum) {
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end_with.extend(missing.iter().cloned());
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if end_with.len() > 0 && group_end.is_none() {
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group_end = Some(cnum);
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}
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}
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end_with.retain(|item| info.lang_item_to_crate.get(item) != Some(&cnum));
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if end_with.len() == 0 && group_end.is_some() {
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group_start = Some(cnum);
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break
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}
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}
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// If we didn't end up filling in all lang items from upstream crates then
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// we'll be filling it in with our crate. This probably means we're the
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// standard library itself, so skip this for now.
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if group_end.is_some() && group_start.is_none() {
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group_end = None;
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}
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let mut compiler_builtins = None;
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for &(cnum, _) in deps.iter() {
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if group_start == Some(cnum) {
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cmd.group_start();
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}
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// We may not pass all crates through to the linker. Some crates may
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// appear statically in an existing dylib, meaning we'll pick up all the
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// symbols from the dylib.
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let src = &codegen_results.crate_info.used_crate_source[&cnum];
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match data[cnum.as_usize() - 1] {
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_ if codegen_results.crate_info.profiler_runtime == Some(cnum) => {
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add_static_crate(cmd, sess, codegen_results, tmpdir, crate_type, cnum);
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}
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_ if codegen_results.crate_info.sanitizer_runtime == Some(cnum) => {
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link_sanitizer_runtime(cmd, sess, codegen_results, tmpdir, cnum);
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}
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// compiler-builtins are always placed last to ensure that they're
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// linked correctly.
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_ if codegen_results.crate_info.compiler_builtins == Some(cnum) => {
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assert!(compiler_builtins.is_none());
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compiler_builtins = Some(cnum);
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}
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Linkage::NotLinked |
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Linkage::IncludedFromDylib => {}
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Linkage::Static => {
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add_static_crate(cmd, sess, codegen_results, tmpdir, crate_type, cnum);
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}
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Linkage::Dynamic => {
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add_dynamic_crate(cmd, sess, &src.dylib.as_ref().unwrap().0)
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}
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}
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if group_end == Some(cnum) {
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cmd.group_end();
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}
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}
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// compiler-builtins are always placed last to ensure that they're
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// linked correctly.
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// We must always link the `compiler_builtins` crate statically. Even if it
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// was already "included" in a dylib (e.g. `libstd` when `-C prefer-dynamic`
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// is used)
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if let Some(cnum) = compiler_builtins {
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add_static_crate(cmd, sess, codegen_results, tmpdir, crate_type, cnum);
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}
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// Converts a library file-stem into a cc -l argument
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fn unlib<'a>(config: &config::Config, stem: &'a str) -> &'a str {
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if stem.starts_with("lib") && !config.target.options.is_like_windows {
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&stem[3..]
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} else {
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stem
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}
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}
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// We must link the sanitizer runtime using -Wl,--whole-archive but since
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// it's packed in a .rlib, it contains stuff that are not objects that will
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// make the linker error. So we must remove those bits from the .rlib before
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// linking it.
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fn link_sanitizer_runtime(cmd: &mut dyn Linker,
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sess: &Session,
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codegen_results: &CodegenResults,
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tmpdir: &Path,
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cnum: CrateNum) {
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let src = &codegen_results.crate_info.used_crate_source[&cnum];
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let cratepath = &src.rlib.as_ref().unwrap().0;
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if sess.target.target.options.is_like_osx {
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// On Apple platforms, the sanitizer is always built as a dylib, and
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// LLVM will link to `@rpath/*.dylib`, so we need to specify an
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// rpath to the library as well (the rpath should be absolute, see
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// PR #41352 for details).
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//
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// FIXME: Remove this logic into librustc_*san once Cargo supports it
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let rpath = cratepath.parent().unwrap();
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let rpath = rpath.to_str().expect("non-utf8 component in path");
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cmd.args(&["-Wl,-rpath".into(), "-Xlinker".into(), rpath.into()]);
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}
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let dst = tmpdir.join(cratepath.file_name().unwrap());
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let cfg = archive_config(sess, &dst, Some(cratepath));
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let mut archive = ArchiveBuilder::new(cfg);
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archive.update_symbols();
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for f in archive.src_files() {
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if f.ends_with(RLIB_BYTECODE_EXTENSION) || f == METADATA_FILENAME {
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archive.remove_file(&f);
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continue
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}
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}
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archive.build();
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cmd.link_whole_rlib(&dst);
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}
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// Adds the static "rlib" versions of all crates to the command line.
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// There's a bit of magic which happens here specifically related to LTO and
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// dynamic libraries. Specifically:
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//
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// * For LTO, we remove upstream object files.
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// * For dylibs we remove metadata and bytecode from upstream rlibs
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//
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// When performing LTO, almost(*) all of the bytecode from the upstream
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// libraries has already been included in our object file output. As a
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// result we need to remove the object files in the upstream libraries so
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// the linker doesn't try to include them twice (or whine about duplicate
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// symbols). We must continue to include the rest of the rlib, however, as
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// it may contain static native libraries which must be linked in.
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//
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// (*) Crates marked with `#![no_builtins]` don't participate in LTO and
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// their bytecode wasn't included. The object files in those libraries must
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// still be passed to the linker.
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//
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// When making a dynamic library, linkers by default don't include any
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// object files in an archive if they're not necessary to resolve the link.
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// We basically want to convert the archive (rlib) to a dylib, though, so we
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// *do* want everything included in the output, regardless of whether the
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// linker thinks it's needed or not. As a result we must use the
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// --whole-archive option (or the platform equivalent). When using this
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// option the linker will fail if there are non-objects in the archive (such
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// as our own metadata and/or bytecode). All in all, for rlibs to be
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// entirely included in dylibs, we need to remove all non-object files.
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//
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// Note, however, that if we're not doing LTO or we're not producing a dylib
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// (aka we're making an executable), we can just pass the rlib blindly to
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// the linker (fast) because it's fine if it's not actually included as
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// we're at the end of the dependency chain.
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fn add_static_crate(cmd: &mut dyn Linker,
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sess: &Session,
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codegen_results: &CodegenResults,
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tmpdir: &Path,
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crate_type: config::CrateType,
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cnum: CrateNum) {
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let src = &codegen_results.crate_info.used_crate_source[&cnum];
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let cratepath = &src.rlib.as_ref().unwrap().0;
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// See the comment above in `link_staticlib` and `link_rlib` for why if
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// there's a static library that's not relevant we skip all object
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// files.
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let native_libs = &codegen_results.crate_info.native_libraries[&cnum];
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let skip_native = native_libs.iter().any(|lib| {
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lib.kind == NativeLibraryKind::NativeStatic && !relevant_lib(sess, lib)
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});
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if (!are_upstream_rust_objects_already_included(sess) ||
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ignored_for_lto(sess, &codegen_results.crate_info, cnum)) &&
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crate_type != config::CrateType::Dylib &&
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!skip_native {
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cmd.link_rlib(&fix_windows_verbatim_for_gcc(cratepath));
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return
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}
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let dst = tmpdir.join(cratepath.file_name().unwrap());
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let name = cratepath.file_name().unwrap().to_str().unwrap();
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let name = &name[3..name.len() - 5]; // chop off lib/.rlib
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time(sess, &format!("altering {}.rlib", name), || {
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let cfg = archive_config(sess, &dst, Some(cratepath));
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let mut archive = ArchiveBuilder::new(cfg);
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archive.update_symbols();
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let mut any_objects = false;
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for f in archive.src_files() {
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if f.ends_with(RLIB_BYTECODE_EXTENSION) || f == METADATA_FILENAME {
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archive.remove_file(&f);
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continue
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}
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let canonical = f.replace("-", "_");
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let canonical_name = name.replace("-", "_");
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// Look for `.rcgu.o` at the end of the filename to conclude
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// that this is a Rust-related object file.
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fn looks_like_rust(s: &str) -> bool {
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let path = Path::new(s);
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let ext = path.extension().and_then(|s| s.to_str());
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if ext != Some(OutputType::Object.extension()) {
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return false
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}
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let ext2 = path.file_stem()
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.and_then(|s| Path::new(s).extension())
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.and_then(|s| s.to_str());
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ext2 == Some(RUST_CGU_EXT)
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}
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let is_rust_object =
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canonical.starts_with(&canonical_name) &&
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looks_like_rust(&f);
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|
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// 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 == config::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) {
|
||
// If we're performing LTO, then it should have been previously required
|
||
// that all upstream rust dependencies were available in an rlib format.
|
||
assert!(!are_upstream_rust_objects_already_included(sess));
|
||
|
||
// Just need to tell the linker about where the library lives and
|
||
// what its name is
|
||
let parent = cratepath.parent();
|
||
if let Some(dir) = parent {
|
||
cmd.include_path(&fix_windows_verbatim_for_gcc(dir));
|
||
}
|
||
let filestem = cratepath.file_stem().unwrap().to_str().unwrap();
|
||
cmd.link_rust_dylib(&unlib(&sess.target, filestem),
|
||
parent.unwrap_or(Path::new("")));
|
||
}
|
||
}
|
||
|
||
// # 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.
|
||
pub 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(ref l) => l,
|
||
None => continue,
|
||
};
|
||
match lib.kind {
|
||
NativeLibraryKind::NativeUnknown => cmd.link_dylib(&name.as_str()),
|
||
NativeLibraryKind::NativeFramework => cmd.link_framework(&name.as_str()),
|
||
NativeLibraryKind::NativeStaticNobundle => cmd.link_staticlib(&name.as_str()),
|
||
NativeLibraryKind::NativeStatic => cmd.link_whole_staticlib(&name.as_str(),
|
||
&search_path)
|
||
}
|
||
}
|
||
}
|
||
|
||
// 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.
|
||
pub fn add_upstream_native_libraries(cmd: &mut dyn Linker,
|
||
sess: &Session,
|
||
codegen_results: &CodegenResults,
|
||
crate_type: config::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 formats = sess.dependency_formats.borrow();
|
||
let data = formats.get(&crate_type).unwrap();
|
||
|
||
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(ref l) => l,
|
||
None => continue,
|
||
};
|
||
if !relevant_lib(sess, &lib) {
|
||
continue
|
||
}
|
||
match lib.kind {
|
||
NativeLibraryKind::NativeUnknown => cmd.link_dylib(&name.as_str()),
|
||
NativeLibraryKind::NativeFramework => cmd.link_framework(&name.as_str()),
|
||
NativeLibraryKind::NativeStaticNobundle => {
|
||
// 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.as_str())
|
||
}
|
||
},
|
||
// ignore statically included native libraries here as we've
|
||
// already included them when we included the rust library
|
||
// previously
|
||
NativeLibraryKind::NativeStatic => {}
|
||
}
|
||
}
|
||
}
|
||
}
|
||
|
||
fn relevant_lib(sess: &Session, lib: &NativeLibrary) -> bool {
|
||
match lib.cfg {
|
||
Some(ref cfg) => attr::cfg_matches(cfg, &sess.parse_sess, None),
|
||
None => true,
|
||
}
|
||
}
|
||
|
||
fn are_upstream_rust_objects_already_included(sess: &Session) -> bool {
|
||
match sess.lto() {
|
||
Lto::Fat => true,
|
||
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.debugging_opts.cross_lang_lto.enabled()
|
||
}
|
||
Lto::No |
|
||
Lto::ThinLocal => false,
|
||
}
|
||
}
|