unify bootstrap and shim binaries

they are now dispatched based on the binary name it is called with.
`target/debug/rust{c, doc}` are now hard linked to `bootstrap`.

src/bootstrap/Cargo.toml

@@ -3,35 +3,15 @@ name = "bootstrap"
 version = "0.0.0"
 edition = "2021"
 build = "build.rs"
-default-run = "bootstrap"
+default-run = "rustbuild-binary-dispatch-shim"
 
 [lib]
 path = "lib.rs"
 doctest = false
 
 [[bin]]
-name = "bootstrap"
-path = "bin/main.rs"
-test = false
-
-[[bin]]
-name = "rustc"
-path = "bin/rustc.rs"
-test = false
-
-[[bin]]
-name = "rustdoc"
-path = "bin/rustdoc.rs"
-test = false
-
-[[bin]]
-name = "sccache-plus-cl"
-path = "bin/sccache-plus-cl.rs"
-test = false
-
-[[bin]]
-name = "llvm-config-wrapper"
-path = "bin/llvm-config-wrapper.rs"
+name = "rustbuild-binary-dispatch-shim"
+path = "entrypoints/dispatcher.rs"
 test = false
 
 [dependencies]

src/bootstrap/bootstrap.py

@@ -837,10 +837,15 @@ def bootstrap_binary(self):
         >>> rb = RustBuild()
         >>> rb.build_dir = "build"
         >>> rb.bootstrap_binary() == os.path.join("build", "bootstrap",
-        ... "debug", "bootstrap")
+        ... "debug", "{}{}".format("rustbuild-binary-dispatch-shim", rb.exe_suffix()))
         True
         """
-        return os.path.join(self.build_dir, "bootstrap", "debug", "bootstrap")
+        return os.path.join(
+            self.build_dir,
+            "bootstrap",
+            "debug",
+            "{}{}".format("rustbuild-binary-dispatch-shim", self.exe_suffix())
+        )
 
     def build_bootstrap(self):
         """Build bootstrap"""

src/bootstrap/bin/main.rs → src/bootstrap/entrypoints/bootstrap.rs

@@ -1,15 +1,8 @@
-//! rustbuild, the Rust build system
-//!
-//! This is the entry point for the build system used to compile the `rustc`
-//! compiler. Lots of documentation can be found in the `README.md` file in the
-//! parent directory, and otherwise documentation can be found throughout the `build`
-//! directory in each respective module.
-
 use std::env;
 
 use bootstrap::{Build, Config, Subcommand, VERSION};
 
-fn main() {
+pub fn main() {
     let args = env::args().skip(1).collect::<Vec<_>>();
     let config = Config::parse(&args);
 

src/bootstrap/entrypoints/dispatcher.rs

@@ -0,0 +1,37 @@
+//! rustbuild, the Rust build system
+//!
+//! This is the entry point for the build system used to compile the `rustc`
+//! compiler. Lots of documentation can be found in the `README.md` file in the
+//! parent directory, and otherwise documentation can be found throughout the `build`
+//! directory in each respective module.
+
+use std::env;
+use std::env::consts::EXE_SUFFIX;
+use std::ffi::OsStr;
+use std::path::Path;
+
+mod bootstrap;
+mod llvm_config_wrapper;
+mod rustc;
+mod rustdoc;
+mod sccache_plus_cl;
+
+fn main() {
+    match env::args_os()
+        .next()
+        .as_deref()
+        .map(Path::new)
+        .and_then(Path::file_name)
+        .and_then(OsStr::to_str)
+        .map(|s| s.strip_suffix(EXE_SUFFIX).unwrap_or(s))
+    {
+        // the shim name is here to make default-run work.
+        Some("bootstrap" | "rustbuild-binary-dispatch-shim") => bootstrap::main(),
+        Some("rustc") => rustc::main(),
+        Some("rustdoc") => rustdoc::main(),
+        Some("sccache-plus-cl") => sccache_plus_cl::main(),
+        Some("llvm-config-wrapper") => llvm_config_wrapper::main(),
+        Some(arg) => panic!("invalid executable name: {}", arg),
+        None => panic!("argv[0] does not exist"),
+    }
+}

src/bootstrap/bin/llvm-config-wrapper.rs → src/bootstrap/entrypoints/llvm_config_wrapper.rs

@@ -5,7 +5,7 @@ use std::env;
 use std::io::{self, Write};
 use std::process::{self, Command, Stdio};
 
-fn main() {
+pub fn main() {
     let real_llvm_config = env::var_os("LLVM_CONFIG_REAL").unwrap();
     let mut cmd = Command::new(real_llvm_config);
     cmd.args(env::args().skip(1)).stderr(Stdio::piped());

src/bootstrap/bin/rustc.rs → src/bootstrap/entrypoints/rustc.rs

@@ -15,15 +15,14 @@
 //! switching compilers for the bootstrap and for build scripts will probably
 //! never get replaced.
 
-include!("../dylib_util.rs");
-
+use bootstrap::util::{dylib_path, dylib_path_var};
 use std::env;
 use std::path::PathBuf;
 use std::process::{Child, Command};
 use std::str::FromStr;
 use std::time::Instant;
 
-fn main() {
+pub fn main() {
     let args = env::args_os().skip(1).collect::<Vec<_>>();
 
     // Detect whether or not we're a build script depending on whether --target

src/bootstrap/bin/rustdoc.rs → src/bootstrap/entrypoints/rustdoc.rs

@@ -2,14 +2,13 @@
 //!
 //! See comments in `src/bootstrap/rustc.rs` for more information.
 
+use bootstrap::util::{dylib_path, dylib_path_var};
 use std::env;
 use std::ffi::OsString;
 use std::path::PathBuf;
 use std::process::Command;
 
-include!("../dylib_util.rs");
-
-fn main() {
+pub fn main() {
     let args = env::args_os().skip(1).collect::<Vec<_>>();
     let rustdoc = env::var_os("RUSTDOC_REAL").expect("RUSTDOC_REAL was not set");
     let libdir = env::var_os("RUSTDOC_LIBDIR").expect("RUSTDOC_LIBDIR was not set");

src/bootstrap/bin/sccache-plus-cl.rs → src/bootstrap/entrypoints/sccache_plus_cl.rs

@@ -1,7 +1,7 @@
 use std::env;
 use std::process::{self, Command};
 
-fn main() {
+pub fn main() {
     let target = env::var("SCCACHE_TARGET").unwrap();
     // Locate the actual compiler that we're invoking
     env::set_var("CC", env::var_os("SCCACHE_CC").unwrap());

src/bootstrap/lib.rs

@@ -106,6 +106,7 @@
 use std::cell::{Cell, RefCell};
 use std::collections::{HashMap, HashSet};
 use std::env;
+use std::env::consts::EXE_SUFFIX;
 use std::fs::{self, File};
 use std::path::{Path, PathBuf};
 use std::process::{self, Command};
@@ -450,15 +451,10 @@ impl Build {
         let bootstrap_out = if std::env::var("BOOTSTRAP_PYTHON").is_ok() {
             out.join("bootstrap").join("debug")
         } else {
-            let workspace_target_dir = std::env::var("CARGO_TARGET_DIR")
+            std::env::var("CARGO_TARGET_DIR")
                 .map(PathBuf::from)
-                .unwrap_or_else(|_| src.join("target"));
-            let bootstrap_out = workspace_target_dir.join("debug");
-            if !bootstrap_out.join("rustc").exists() && !cfg!(test) {
-                // this restriction can be lifted whenever https://github.com/rust-lang/rfcs/pull/3028 is implemented
-                panic!("run `cargo build --bins` before `cargo run`")
-            }
-            bootstrap_out
+                .unwrap_or_else(|_| src.join("target"))
+                .join("debug")
         };
 
         let mut build = Build {
@@ -502,6 +498,20 @@ impl Build {
             tool_artifacts: Default::default(),
         };
 
+        let bootstrap_out = &build.bootstrap_out;
+        let dispatcher = bootstrap_out.join(format!("rustbuild-binary-dispatch-shim{EXE_SUFFIX}"));
+        if dispatcher.exists() && !cfg!(test) {
+            build.copy(&dispatcher, &bootstrap_out.join(format!("bootstrap{EXE_SUFFIX}")));
+            build.copy(&dispatcher, &bootstrap_out.join(format!("rustc{EXE_SUFFIX}")));
+            build.copy(&dispatcher, &bootstrap_out.join(format!("rustdoc{EXE_SUFFIX}")));
+            build.copy(&dispatcher, &bootstrap_out.join(format!("sccache-plus-cl{EXE_SUFFIX}")));
+            build
+                .copy(&dispatcher, &bootstrap_out.join(format!("llvm-config-wrapper{EXE_SUFFIX}")));
+        } else if !cfg!(test) {
+            // tests do not need these files to be copied.
+            panic!("bootstrap binary shim ({}) does not exist", dispatcher.display());
+        }
+
         build.verbose("finding compilers");
         cc_detect::find(&mut build);
         // When running `setup`, the profile is about to change, so any requirements we have now may

src/bootstrap/util.rs

@@ -72,7 +72,29 @@ pub fn add_dylib_path(path: Vec<PathBuf>, cmd: &mut Command) {
     cmd.env(dylib_path_var(), t!(env::join_paths(list)));
 }
 
-include!("dylib_util.rs");
+/// Returns the environment variable which the dynamic library lookup path
+/// resides in for this platform.
+pub fn dylib_path_var() -> &'static str {
+    if cfg!(target_os = "windows") {
+        "PATH"
+    } else if cfg!(target_os = "macos") {
+        "DYLD_LIBRARY_PATH"
+    } else if cfg!(target_os = "haiku") {
+        "LIBRARY_PATH"
+    } else {
+        "LD_LIBRARY_PATH"
+    }
+}
+
+/// Parses the `dylib_path_var()` environment variable, returning a list of
+/// paths that are members of this lookup path.
+pub fn dylib_path() -> Vec<std::path::PathBuf> {
+    let var = match env::var_os(dylib_path_var()) {
+        Some(v) => v,
+        None => return vec![],
+    };
+    env::split_paths(&var).collect()
+}
 
 /// Adds a list of lookup paths to `cmd`'s link library lookup path.
 pub fn add_link_lib_path(path: Vec<PathBuf>, cmd: &mut Command) {