src/bootstrap/bin/rustc.rs

   1 // Copyright 2015 The Rust Project Developers. See the COPYRIGHT
   2 // file at the top-level directory of this distribution and at
   3 // http://rust-lang.org/COPYRIGHT.
   4 //
   5 // Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
   6 // http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
   7 // <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
   8 // option. This file may not be copied, modified, or distributed
   9 // except according to those terms.
  10
  11 //! Shim which is passed to Cargo as "rustc" when running the bootstrap.
  12 //!
  13 //! This shim will take care of some various tasks that our build process
  14 //! requires that Cargo can't quite do through normal configuration:
  15 //!
  16 //! 1. When compiling build scripts and build dependencies, we need a guaranteed
  17 //!    full standard library available. The only compiler which actually has
  18 //!    this is the snapshot, so we detect this situation and always compile with
  19 //!    the snapshot compiler.
  20 //! 2. We pass a bunch of `--cfg` and other flags based on what we're compiling
  21 //!    (and this slightly differs based on a whether we're using a snapshot or
  22 //!    not), so we do that all here.
  23 //!
  24 //! This may one day be replaced by RUSTFLAGS, but the dynamic nature of
  25 //! switching compilers for the bootstrap and for build scripts will probably
  26 //! never get replaced.
  27
  28 extern crate bootstrap;
  29
  30 use std::env;
  31 use std::ffi::OsString;
  32 use std::path::PathBuf;
  33 use std::process::Command;
  34
  35 fn main() {
  36     let args = env::args_os().skip(1).collect::<Vec<_>>();
  37     // Detect whether or not we're a build script depending on whether --target
  38     // is passed (a bit janky...)
  39     let target = args.windows(2)
  40         .find(|w| &*w[0] == "--target")
  41         .and_then(|w| w[1].to_str());
  42     let version = args.iter().find(|w| &**w == "-vV");
  43
  44     // Build scripts always use the snapshot compiler which is guaranteed to be
  45     // able to produce an executable, whereas intermediate compilers may not
  46     // have the standard library built yet and may not be able to produce an
  47     // executable. Otherwise we just use the standard compiler we're
  48     // bootstrapping with.
  49     //
  50     // Also note that cargo will detect the version of the compiler to trigger
  51     // a rebuild when the compiler changes. If this happens, we want to make
  52     // sure to use the actual compiler instead of the snapshot compiler becase
  53     // that's the one that's actually changing.
  54     let (rustc, libdir) = if target.is_none() && version.is_none() {
  55         ("RUSTC_SNAPSHOT", "RUSTC_SNAPSHOT_LIBDIR")
  56     } else {
  57         ("RUSTC_REAL", "RUSTC_LIBDIR")
  58     };
  59     let stage = env::var("RUSTC_STAGE").expect("RUSTC_STAGE was not set");
  60
  61     let rustc = env::var_os(rustc).unwrap_or_else(|| panic!("{:?} was not set", rustc));
  62     let libdir = env::var_os(libdir).unwrap_or_else(|| panic!("{:?} was not set", libdir));
  63     let mut dylib_path = bootstrap::util::dylib_path();
  64     dylib_path.insert(0, PathBuf::from(libdir));
  65
  66     let mut cmd = Command::new(rustc);
  67     cmd.args(&args)
  68         .arg("--cfg")
  69         .arg(format!("stage{}", stage))
  70         .env(bootstrap::util::dylib_path_var(),
  71              env::join_paths(&dylib_path).unwrap());
  72
  73     if let Some(target) = target {
  74         // The stage0 compiler has a special sysroot distinct from what we
  75         // actually downloaded, so we just always pass the `--sysroot` option.
  76         cmd.arg("--sysroot").arg(env::var_os("RUSTC_SYSROOT").expect("RUSTC_SYSROOT was not set"));
  77
  78         // When we build Rust dylibs they're all intended for intermediate
  79         // usage, so make sure we pass the -Cprefer-dynamic flag instead of
  80         // linking all deps statically into the dylib.
  81         cmd.arg("-Cprefer-dynamic");
  82
  83         // Help the libc crate compile by assisting it in finding the MUSL
  84         // native libraries.
  85         if let Some(s) = env::var_os("MUSL_ROOT") {
  86             let mut root = OsString::from("native=");
  87             root.push(&s);
  88             root.push("/lib");
  89             cmd.arg("-L").arg(&root);
  90         }
  91
  92         // Pass down extra flags, commonly used to configure `-Clinker` when
  93         // cross compiling.
  94         if let Ok(s) = env::var("RUSTC_FLAGS") {
  95             cmd.args(&s.split(" ").filter(|s| !s.is_empty()).collect::<Vec<_>>());
  96         }
  97
  98         // If we're compiling specifically the `panic_abort` crate then we pass
  99         // the `-C panic=abort` option. Note that we do not do this for any
 100         // other crate intentionally as this is the only crate for now that we
 101         // ship with panic=abort.
 102         //
 103         // This... is a bit of a hack how we detect this. Ideally this
 104         // information should be encoded in the crate I guess? Would likely
 105         // require an RFC amendment to RFC 1513, however.
 106         let is_panic_abort = args.windows(2)
 107             .any(|a| &*a[0] == "--crate-name" && &*a[1] == "panic_abort");
 108         if is_panic_abort {
 109             cmd.arg("-C").arg("panic=abort");
 110         }
 111
 112         // Set various options from config.toml to configure how we're building
 113         // code.
 114         if env::var("RUSTC_DEBUGINFO") == Ok("true".to_string()) {
 115             cmd.arg("-g");
 116         } else if env::var("RUSTC_DEBUGINFO_LINES") == Ok("true".to_string()) {
 117             cmd.arg("-Cdebuginfo=1");
 118         }
 119         let debug_assertions = match env::var("RUSTC_DEBUG_ASSERTIONS") {
 120             Ok(s) => if s == "true" { "y" } else { "n" },
 121             Err(..) => "n",
 122         };
 123         cmd.arg("-C").arg(format!("debug-assertions={}", debug_assertions));
 124         if let Ok(s) = env::var("RUSTC_CODEGEN_UNITS") {
 125             cmd.arg("-C").arg(format!("codegen-units={}", s));
 126         }
 127
 128         // Dealing with rpath here is a little special, so let's go into some
 129         // detail. First off, `-rpath` is a linker option on Unix platforms
 130         // which adds to the runtime dynamic loader path when looking for
 131         // dynamic libraries. We use this by default on Unix platforms to ensure
 132         // that our nightlies behave the same on Windows, that is they work out
 133         // of the box. This can be disabled, of course, but basically that's why
 134         // we're gated on RUSTC_RPATH here.
 135         //
 136         // Ok, so the astute might be wondering "why isn't `-C rpath` used
 137         // here?" and that is indeed a good question to task. This codegen
 138         // option is the compiler's current interface to generating an rpath.
 139         // Unfortunately it doesn't quite suffice for us. The flag currently
 140         // takes no value as an argument, so the compiler calculates what it
 141         // should pass to the linker as `-rpath`. This unfortunately is based on
 142         // the **compile time** directory structure which when building with
 143         // Cargo will be very different than the runtime directory structure.
 144         //
 145         // All that's a really long winded way of saying that if we use
 146         // `-Crpath` then the executables generated have the wrong rpath of
 147         // something like `$ORIGIN/deps` when in fact the way we distribute
 148         // rustc requires the rpath to be `$ORIGIN/../lib`.
 149         //
 150         // So, all in all, to set up the correct rpath we pass the linker
 151         // argument manually via `-C link-args=-Wl,-rpath,...`. Plus isn't it
 152         // fun to pass a flag to a tool to pass a flag to pass a flag to a tool
 153         // to change a flag in a binary?
 154         if env::var("RUSTC_RPATH") == Ok("true".to_string()) {
 155             let rpath = if target.contains("apple") {
 156                 Some("-Wl,-rpath,@loader_path/../lib")
 157             } else if !target.contains("windows") {
 158                 Some("-Wl,-rpath,$ORIGIN/../lib")
 159             } else {
 160                 None
 161             };
 162             if let Some(rpath) = rpath {
 163                 cmd.arg("-C").arg(format!("link-args={}", rpath));
 164             }
 165         }
 166     }
 167
 168     // Actually run the compiler!
 169     std::process::exit(match cmd.status() {
 170         Ok(s) => s.code().unwrap_or(1),
 171         Err(e) => panic!("\n\nfailed to run {:?}: {}\n\n", cmd, e),
 172     })
 173 }