Auto merge of #94480 - bjorn3:no_build_helper, r=Mark-Simulacrum

Remove build_helper

The majority of the code is only used by either rustbuild or
rustc_llvm's build script. Rust_build is compiled once for rustbuild and
once for every stage. This means that the majority of the code in this
crate is needlessly compiled multiple times. By moving only the code
actually used by the respective crates to rustbuild and rustc_llvm's
build script, this needless duplicate compilation is avoided.

Author: bors

Cargo.lock

@@ -214,7 +214,6 @@ dependencies = [
 name = "bootstrap"
 version = "0.0.0"
 dependencies = [
- "build_helper",
  "cc",
  "cmake",
  "filetime",
@@ -256,10 +255,6 @@ dependencies = [
  "toml",
 ]
 
-[[package]]
-name = "build_helper"
-version = "0.1.0"
-
 [[package]]
 name = "bump-stage0"
 version = "0.1.0"
@@ -3891,7 +3886,6 @@ dependencies = [
 name = "rustc_llvm"
 version = "0.0.0"
 dependencies = [
- "build_helper",
  "cc",
  "libc",
 ]

compiler/rustc_llvm/Cargo.toml

@@ -11,5 +11,4 @@ emscripten = []
 libc = "0.2.73"
 
 [build-dependencies]
-build_helper = { path = "../../src/build_helper" }
 cc = "1.0.69"

compiler/rustc_llvm/build.rs

@@ -1,8 +1,8 @@
 use std::env;
+use std::ffi::{OsStr, OsString};
+use std::fmt::Display;
 use std::path::{Path, PathBuf};
-use std::process::Command;
-
-use build_helper::{output, tracked_env_var_os};
+use std::process::{Command, Stdio};
 
 fn detect_llvm_link() -> (&'static str, &'static str) {
     // Force the link mode we want, preferring static by default, but
@@ -14,13 +14,74 @@ fn detect_llvm_link() -> (&'static str, &'static str) {
     }
 }
 
+// Because Cargo adds the compiler's dylib path to our library search path, llvm-config may
+// break: the dylib path for the compiler, as of this writing, contains a copy of the LLVM
+// shared library, which means that when our freshly built llvm-config goes to load it's
+// associated LLVM, it actually loads the compiler's LLVM. In particular when building the first
+// compiler (i.e., in stage 0) that's a problem, as the compiler's LLVM is likely different from
+// the one we want to use. As such, we restore the environment to what bootstrap saw. This isn't
+// perfect -- we might actually want to see something from Cargo's added library paths -- but
+// for now it works.
+fn restore_library_path() {
+    let key = tracked_env_var_os("REAL_LIBRARY_PATH_VAR").expect("REAL_LIBRARY_PATH_VAR");
+    if let Some(env) = tracked_env_var_os("REAL_LIBRARY_PATH") {
+        env::set_var(&key, &env);
+    } else {
+        env::remove_var(&key);
+    }
+}
+
+/// Reads an environment variable and adds it to dependencies.
+/// Supposed to be used for all variables except those set for build scripts by cargo
+/// <https://doc.rust-lang.org/cargo/reference/environment-variables.html#environment-variables-cargo-sets-for-build-scripts>
+fn tracked_env_var_os<K: AsRef<OsStr> + Display>(key: K) -> Option<OsString> {
+    println!("cargo:rerun-if-env-changed={}", key);
+    env::var_os(key)
+}
+
+fn rerun_if_changed_anything_in_dir(dir: &Path) {
+    let mut stack = dir
+        .read_dir()
+        .unwrap()
+        .map(|e| e.unwrap())
+        .filter(|e| &*e.file_name() != ".git")
+        .collect::<Vec<_>>();
+    while let Some(entry) = stack.pop() {
+        let path = entry.path();
+        if entry.file_type().unwrap().is_dir() {
+            stack.extend(path.read_dir().unwrap().map(|e| e.unwrap()));
+        } else {
+            println!("cargo:rerun-if-changed={}", path.display());
+        }
+    }
+}
+
+#[track_caller]
+fn output(cmd: &mut Command) -> String {
+    let output = match cmd.stderr(Stdio::inherit()).output() {
+        Ok(status) => status,
+        Err(e) => {
+            println!("\n\nfailed to execute command: {:?}\nerror: {}\n\n", cmd, e);
+            std::process::exit(1);
+        }
+    };
+    if !output.status.success() {
+        panic!(
+            "command did not execute successfully: {:?}\n\
+             expected success, got: {}",
+            cmd, output.status
+        );
+    }
+    String::from_utf8(output.stdout).unwrap()
+}
+
 fn main() {
     if tracked_env_var_os("RUST_CHECK").is_some() {
         // If we're just running `check`, there's no need for LLVM to be built.
         return;
     }
 
-    build_helper::restore_library_path();
+    restore_library_path();
 
     let target = env::var("TARGET").expect("TARGET was not set");
     let llvm_config =
@@ -160,7 +221,7 @@ fn main() {
         cfg.debug(false);
     }
 
-    build_helper::rerun_if_changed_anything_in_dir(Path::new("llvm-wrapper"));
+    rerun_if_changed_anything_in_dir(Path::new("llvm-wrapper"));
     cfg.file("llvm-wrapper/PassWrapper.cpp")
         .file("llvm-wrapper/RustWrapper.cpp")
         .file("llvm-wrapper/ArchiveWrapper.cpp")

src/bootstrap/Cargo.toml

@@ -34,7 +34,6 @@ path = "bin/llvm-config-wrapper.rs"
 test = false
 
 [dependencies]
-build_helper = { path = "../build_helper" }
 cmake = "0.1.38"
 filetime = "0.2"
 getopts = "0.2.19"

src/bootstrap/builder.rs

@@ -11,8 +11,6 @@ use std::path::{Component, Path, PathBuf};
 use std::process::Command;
 use std::time::{Duration, Instant};
 
-use build_helper::{output, t};
-
 use crate::cache::{Cache, Interned, INTERNER};
 use crate::check;
 use crate::compile;
@@ -25,7 +23,7 @@ use crate::native;
 use crate::run;
 use crate::test;
 use crate::tool::{self, SourceType};
-use crate::util::{self, add_dylib_path, add_link_lib_path, exe, libdir};
+use crate::util::{self, add_dylib_path, add_link_lib_path, exe, libdir, output, t};
 use crate::EXTRA_CHECK_CFGS;
 use crate::{Build, CLang, DocTests, GitRepo, Mode};
 

src/bootstrap/cc_detect.rs

@@ -26,9 +26,8 @@ use std::path::{Path, PathBuf};
 use std::process::Command;
 use std::{env, iter};
 
-use build_helper::output;
-
 use crate::config::{Target, TargetSelection};
+use crate::util::output;
 use crate::{Build, CLang, GitRepo};
 
 // The `cc` crate doesn't provide a way to obtain a path to the detected archiver,

src/bootstrap/channel.rs

@@ -8,8 +8,7 @@
 use std::path::Path;
 use std::process::Command;
 
-use build_helper::output;
-
+use crate::util::output;
 use crate::Build;
 
 pub enum GitInfo {

src/bootstrap/clean.rs

@@ -9,8 +9,7 @@ use std::fs;
 use std::io::{self, ErrorKind};
 use std::path::Path;
 
-use build_helper::t;
-
+use crate::util::t;
 use crate::Build;
 
 pub fn clean(build: &Build, all: bool) {

src/bootstrap/compile.rs

@@ -16,7 +16,6 @@ use std::path::{Path, PathBuf};
 use std::process::{exit, Command, Stdio};
 use std::str;
 
-use build_helper::{output, t, up_to_date};
 use serde::Deserialize;
 
 use crate::builder::Cargo;
@@ -26,7 +25,7 @@ use crate::config::{LlvmLibunwind, TargetSelection};
 use crate::dist;
 use crate::native;
 use crate::tool::SourceType;
-use crate::util::{exe, is_debug_info, is_dylib, symlink_dir};
+use crate::util::{exe, is_debug_info, is_dylib, output, symlink_dir, t, up_to_date};
 use crate::LLVM_TOOLS;
 use crate::{CLang, Compiler, DependencyType, GitRepo, Mode};
 

src/bootstrap/config.rs

@@ -17,8 +17,7 @@ use crate::cache::{Interned, INTERNER};
 use crate::channel::GitInfo;
 pub use crate::flags::Subcommand;
 use crate::flags::{Color, Flags};
-use crate::util::exe;
-use build_helper::t;
+use crate::util::{exe, t};
 use serde::Deserialize;
 
 macro_rules! check_ci_llvm {