rustbuild: Remove the `build` directory

The organization in rustbuild was a little odd at the moment where the `lib.rs`
was quite small but the binary `main.rs` was much larger. Unfortunately as well
there was a `build/` directory with the implementation of the build system, but
this directory was ignored by GitHub on the file-search prompt which was a
little annoying.

This commit reorganizes rustbuild slightly where all the library files (the
build system) is located directly inside of `src/bootstrap` and all the binaries
now live in `src/bootstrap/bin` (they're small). Hopefully this should allow
GitHub to index and allow navigating all the files while maintaining a
relatively similar layout to the other libraries in `src/`.

1 files changed, 165 insertions, 0 deletions

diff --git a/src/bootstrap/bin/rustc.rs b/src/bootstrap/bin/rustc.rs
new file mode 100644
index 00000000000..c64cbb9a74e
--- /dev/null
+++ b/src/bootstrap/bin/rustc.rs
@@ -0,0 +1,165 @@
+// Copyright 2015 The Rust Project Developers. See the COPYRIGHT
+// file at the top-level directory of this distribution and at
+// http://rust-lang.org/COPYRIGHT.
+//
+// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
+// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
+// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
+// option. This file may not be copied, modified, or distributed
+// except according to those terms.
+
+//! 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.
+
+extern crate bootstrap;
+
+use std::env;
+use std::ffi::OsString;
+use std::path::PathBuf;
+use std::process::Command;
+
+fn main() {
+    let args = env::args_os().skip(1).collect::<Vec<_>>();
+    // Detect whether or not we're a build script depending on whether --target
+    // is passed (a bit janky...)
+    let target = args.windows(2).find(|w| &*w[0] == "--target")
+                                .and_then(|w| w[1].to_str());
+
+    // Build scripts always use the snapshot compiler which is guaranteed to be
+    // able to produce an executable, whereas intermediate compilers may not
+    // have the standard library built yet and may not be able to produce an
+    // executable. Otherwise we just use the standard compiler we're
+    // bootstrapping with.
+    let (rustc, libdir) = if target.is_none() {
+        ("RUSTC_SNAPSHOT", "RUSTC_SNAPSHOT_LIBDIR")
+    } else {
+        ("RUSTC_REAL", "RUSTC_LIBDIR")
+    };
+    let stage = env::var("RUSTC_STAGE").unwrap();
+
+    let rustc = env::var_os(rustc).unwrap();
+    let libdir = env::var_os(libdir).unwrap();
+    let mut dylib_path = bootstrap::util::dylib_path();
+    dylib_path.insert(0, PathBuf::from(libdir));
+
+    let mut cmd = Command::new(rustc);
+    cmd.args(&args)
+       .arg("--cfg").arg(format!("stage{}", stage))
+       .env(bootstrap::util::dylib_path_var(),
+            env::join_paths(&dylib_path).unwrap());
+
+    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.
+        cmd.arg("--sysroot").arg(env::var_os("RUSTC_SYSROOT").unwrap());
+
+        // 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.
+        cmd.arg("-Cprefer-dynamic");
+
+        // Help the libc crate compile by assisting it in finding the MUSL
+        // native libraries.
+        if let Some(s) = env::var_os("MUSL_ROOT") {
+            let mut root = OsString::from("native=");
+            root.push(&s);
+            root.push("/lib");
+            cmd.arg("-L").arg(&root);
+        }
+
+        // Pass down extra flags, commonly used to configure `-Clinker` when
+        // cross compiling.
+        if let Ok(s) = env::var("RUSTC_FLAGS") {
+            cmd.args(&s.split(" ").filter(|s| !s.is_empty()).collect::<Vec<_>>());
+        }
+
+        // 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.
+        let is_panic_abort = args.windows(2).any(|a| {
+            &*a[0] == "--crate-name" && &*a[1] == "panic_abort"
+        });
+        // FIXME(stage0): remove this `stage != "0"` condition
+        if is_panic_abort && stage != "0" {
+            cmd.arg("-C").arg("panic=abort");
+        }
+
+        // Set various options from config.toml to configure how we're building
+        // code.
+        if env::var("RUSTC_DEBUGINFO") == Ok("true".to_string()) {
+            cmd.arg("-g");
+        }
+        let debug_assertions = match env::var("RUSTC_DEBUG_ASSERTIONS") {
+            Ok(s) => if s == "true" {"y"} else {"n"},
+            Err(..) => "n",
+        };
+        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));
+        }
+
+        // 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") {
+                Some("-Wl,-rpath,@loader_path/../lib")
+            } else if !target.contains("windows") {
+                Some("-Wl,-rpath,$ORIGIN/../lib")
+            } else {
+                None
+            };
+            if let Some(rpath) = rpath {
+                cmd.arg("-C").arg(format!("link-args={}", rpath));
+            }
+        }
+    }
+
+    // Actually run the compiler!
+    std::process::exit(match cmd.status() {
+        Ok(s) => s.code().unwrap_or(1),
+        Err(e) => panic!("\n\nfailed to run {:?}: {}\n\n", cmd, e),
+    })
+}