Skip to content
Branch: master
Find file Copy path
Find file Copy path
383 lines (340 sloc) 15.5 KB
//! Shim which is passed to Cargo as "rustc" when running the bootstrap.
//! This shim will take care of some various tasks that our build process
//! requires that Cargo can't quite do through normal configuration:
//! 1. When compiling build scripts and build dependencies, we need a guaranteed
//! full standard library available. The only compiler which actually has
//! this is the snapshot, so we detect this situation and always compile with
//! the snapshot compiler.
//! 2. We pass a bunch of `--cfg` and other flags based on what we're compiling
//! (and this slightly differs based on a whether we're using a snapshot or
//! not), so we do that all here.
//! This may one day be replaced by RUSTFLAGS, but the dynamic nature of
//! switching compilers for the bootstrap and for build scripts will probably
//! never get replaced.
use std::env;
use std::ffi::OsString;
use std::io;
use std::path::PathBuf;
use std::process::Command;
use std::str::FromStr;
use std::time::Instant;
fn main() {
let mut args = env::args_os().skip(1).collect::<Vec<_>>();
// Append metadata suffix for internal crates. See the corresponding entry
// in bootstrap/ for details.
if let Ok(s) = env::var("RUSTC_METADATA_SUFFIX") {
for i in 1..args.len() {
// Dirty code for borrowing issues
let mut new = None;
if let Some(current_as_str) = args[i].to_str() {
if (&*args[i - 1] == "-C" && current_as_str.starts_with("metadata")) ||
current_as_str.starts_with("-Cmetadata") {
new = Some(format!("{}-{}", current_as_str, s));
if let Some(new) = new { args[i] = new.into(); }
// Detect whether or not we're a build script depending on whether --target
// is passed (a bit janky...)
let target =
.find(|w| &*w[0] == "--target")
.and_then(|w| w[1].to_str());
let version = args.iter().find(|w| &**w == "-vV");
let verbose = match env::var("RUSTC_VERBOSE") {
Ok(s) => usize::from_str(&s).expect("RUSTC_VERBOSE should be an integer"),
Err(_) => 0,
// Use a different compiler for build scripts, since there may not yet be a
// libstd for the real compiler to use. However, if Cargo is attempting to
// determine the version of the compiler, the real compiler needs to be
// used. Currently, these two states are differentiated based on whether
// --target and -vV is/isn't passed.
let (rustc, libdir) = if target.is_none() && version.is_none() {
} else {
let stage = env::var("RUSTC_STAGE").expect("RUSTC_STAGE was not set");
let sysroot = env::var_os("RUSTC_SYSROOT").expect("RUSTC_SYSROOT was not set");
let on_fail = env::var_os("RUSTC_ON_FAIL").map(|of| Command::new(of));
let rustc = env::var_os(rustc).unwrap_or_else(|| panic!("{:?} was not set", rustc));
let libdir = env::var_os(libdir).unwrap_or_else(|| panic!("{:?} was not set", libdir));
let mut dylib_path = bootstrap::util::dylib_path();
dylib_path.insert(0, PathBuf::from(&libdir));
let mut cmd = Command::new(rustc);
// Get the name of the crate we're compiling, if any.
let crate_name =
.find(|args| args[0] == "--crate-name")
.and_then(|args| args[1].to_str());
if let Some(crate_name) = crate_name {
if let Some(target) = env::var_os("RUSTC_TIME") {
if target == "all" ||
target.into_string().unwrap().split(",").any(|c| c.trim() == crate_name)
// Non-zero stages must all be treated uniformly to avoid problems when attempting to uplift
// compiler libraries and such from stage 1 to 2.
// FIXME: the fact that core here is excluded is due to core_arch from our stdarch submodule
// being broken on the beta compiler with bootstrap passed, so this is a temporary workaround
// (we've just snapped, so there are no cfg(bootstrap) related annotations in core).
if stage == "0" {
if crate_name != Some("core") {
} else {
// NOTE(eddyb) see FIXME above, except now we need annotations again in core.
// Print backtrace in case of ICE
if env::var("RUSTC_BACKTRACE_ON_ICE").is_ok() && env::var("RUST_BACKTRACE").is_err() {
cmd.env("RUST_BACKTRACE", "1");
cmd.env("RUSTC_BREAK_ON_ICE", "1");
if let Ok(debuginfo_level) = env::var("RUSTC_DEBUGINFO_LEVEL") {
cmd.arg(format!("-Cdebuginfo={}", debuginfo_level));
if env::var_os("RUSTC_EXTERNAL_TOOL").is_none() {
// When extending this list, add the new lints to the RUSTFLAGS of the
// build_bootstrap function of src/bootstrap/ as well as
// some code doesn't go through this `rustc` wrapper.
if use_internal_lints(crate_name) {
if env::var_os("RUSTC_DENY_WARNINGS").is_some() {
if let Some(target) = target {
// The stage0 compiler has a special sysroot distinct from what we
// actually downloaded, so we just always pass the `--sysroot` option,
// unless one is already set.
if !args.iter().any(|arg| arg == "--sysroot") {
// Link crates to the proc macro crate for the target, but use a host proc macro crate
// to actually run the macros
if env::var_os("RUST_DUAL_PROC_MACROS").is_some() {
// When we build Rust dylibs they're all intended for intermediate
// usage, so make sure we pass the -Cprefer-dynamic flag instead of
// linking all deps statically into the dylib.
if env::var_os("RUSTC_NO_PREFER_DYNAMIC").is_none() {
// Help the libc crate compile by assisting it in finding various
// sysroot native libraries.
if let Some(s) = env::var_os("MUSL_ROOT") {
if target.contains("musl") {
let mut root = OsString::from("native=");
if let Some(s) = env::var_os("WASI_ROOT") {
let mut root = OsString::from("native=");
// Override linker if necessary.
if let Ok(target_linker) = env::var("RUSTC_TARGET_LINKER") {
cmd.arg(format!("-Clinker={}", target_linker));
// If we're compiling specifically the `panic_abort` crate then we pass
// the `-C panic=abort` option. Note that we do not do this for any
// other crate intentionally as this is the only crate for now that we
// ship with panic=abort.
// This... is a bit of a hack how we detect this. Ideally this
// information should be encoded in the crate I guess? Would likely
// require an RFC amendment to RFC 1513, however.
// `compiler_builtins` are unconditionally compiled with panic=abort to
// workaround undefined references to `rust_eh_unwind_resume` generated
// otherwise, see issue
if crate_name == Some("panic_abort") ||
crate_name == Some("compiler_builtins") && stage != "0" {
// Set various options from config.toml to configure how we're building
// code.
let debug_assertions = match env::var("RUSTC_DEBUG_ASSERTIONS") {
Ok(s) => if s == "true" { "y" } else { "n" },
Err(..) => "n",
// The compiler builtins are pretty sensitive to symbols referenced in
// libcore and such, so we never compile them with debug assertions.
if crate_name == Some("compiler_builtins") {
} else {
cmd.arg("-C").arg(format!("debug-assertions={}", debug_assertions));
if let Ok(s) = env::var("RUSTC_CODEGEN_UNITS") {
cmd.arg("-C").arg(format!("codegen-units={}", s));
// Emit save-analysis info.
if env::var("RUSTC_SAVE_ANALYSIS") == Ok("api".to_string()) {
"{\"output_file\": null,\"full_docs\": false,\
\"pub_only\": true,\"reachable_only\": false,\
\"distro_crate\": true,\"signatures\": false,\"borrow_data\": false}");
// Dealing with rpath here is a little special, so let's go into some
// detail. First off, `-rpath` is a linker option on Unix platforms
// which adds to the runtime dynamic loader path when looking for
// dynamic libraries. We use this by default on Unix platforms to ensure
// that our nightlies behave the same on Windows, that is they work out
// of the box. This can be disabled, of course, but basically that's why
// we're gated on RUSTC_RPATH here.
// Ok, so the astute might be wondering "why isn't `-C rpath` used
// here?" and that is indeed a good question to task. This codegen
// option is the compiler's current interface to generating an rpath.
// Unfortunately it doesn't quite suffice for us. The flag currently
// takes no value as an argument, so the compiler calculates what it
// should pass to the linker as `-rpath`. This unfortunately is based on
// the **compile time** directory structure which when building with
// Cargo will be very different than the runtime directory structure.
// All that's a really long winded way of saying that if we use
// `-Crpath` then the executables generated have the wrong rpath of
// something like `$ORIGIN/deps` when in fact the way we distribute
// rustc requires the rpath to be `$ORIGIN/../lib`.
// So, all in all, to set up the correct rpath we pass the linker
// argument manually via `-C link-args=-Wl,-rpath,...`. Plus isn't it
// fun to pass a flag to a tool to pass a flag to pass a flag to a tool
// to change a flag in a binary?
if env::var("RUSTC_RPATH") == Ok("true".to_string()) {
let rpath = if target.contains("apple") {
// Note that we need to take one extra step on macOS to also pass
// `-Wl,-instal_name,@rpath/...` to get things to work right. To
// do that we pass a weird flag to the compiler to get it to do
// so. Note that this is definitely a hack, and we should likely
// flesh out rpath support more fully in the future.
} else if !target.contains("windows") &&
!target.contains("wasm32") &&
!target.contains("fuchsia") {
} else {
if let Some(rpath) = rpath {
cmd.arg("-C").arg(format!("link-args={}", rpath));
if let Ok(s) = env::var("RUSTC_CRT_STATIC") {
if s == "true" {
if s == "false" {
} else {
// Override linker if necessary.
if let Ok(host_linker) = env::var("RUSTC_HOST_LINKER") {
cmd.arg(format!("-Clinker={}", host_linker));
if let Ok(s) = env::var("RUSTC_HOST_CRT_STATIC") {
if s == "true" {
if s == "false" {
if let Ok(map) = env::var("RUSTC_DEBUGINFO_MAP") {
// Force all crates compiled by this compiler to (a) be unstable and (b)
// allow the `rustc_private` feature to link to other unstable crates
// also in the sysroot. We also do this for host crates, since those
// may be proc macros, in which case we might ship them.
if env::var_os("RUSTC_FORCE_UNSTABLE").is_some() && (stage != "0" || target.is_some()) {
if env::var_os("RUSTC_PARALLEL_COMPILER").is_some() {
if verbose > 1 {
"rustc command: {:?}={:?} {:?}",
eprintln!("sysroot: {:?}", sysroot);
eprintln!("libdir: {:?}", libdir);
if let Some(mut on_fail) = on_fail {
let e = match cmd.status() {
Ok(s) if s.success() => std::process::exit(0),
e => e,
println!("\nDid not run successfully: {:?}\n{:?}\n-------------", e, cmd);
exec_cmd(&mut on_fail).expect("could not run the backup command");
if env::var_os("RUSTC_PRINT_STEP_TIMINGS").is_some() {
if let Some(crate_name) = crate_name {
let start = Instant::now();
let status = cmd
.unwrap_or_else(|_| panic!("\n\n failed to run {:?}", cmd));
let dur = start.elapsed();
let is_test = args.iter().any(|a| a == "--test");
eprintln!("[RUSTC-TIMING] {} test:{} {}.{:03}",
dur.subsec_nanos() / 1_000_000);
match status.code() {
Some(i) => std::process::exit(i),
None => {
eprintln!("rustc exited with {}", status);
let code = exec_cmd(&mut cmd).unwrap_or_else(|_| panic!("\n\n failed to run {:?}", cmd));
// Rustc crates for which internal lints are in effect.
fn use_internal_lints(crate_name: Option<&str>) -> bool {
crate_name.map_or(false, |crate_name| {
crate_name.starts_with("rustc") || crate_name.starts_with("syntax") ||
["arena", "fmt_macros"].contains(&crate_name)
fn exec_cmd(cmd: &mut Command) -> io::Result<i32> {
use std::os::unix::process::CommandExt;
fn exec_cmd(cmd: &mut Command) -> io::Result<i32> {
cmd.status().map(|status| status.code().unwrap())
You can’t perform that action at this time.