Check if the patched sysroot source is up to date before using it

Fixes rust-lang#1181

Author: bjorn3

.gitignore

@@ -10,6 +10,7 @@ perf.data.old
 /build
 /build_sysroot/sysroot_src
 /build_sysroot/compiler-builtins
+/build_sysroot/rustc_version
 /rust
 /rand
 /regex

build_system/build_sysroot.rs

@@ -3,7 +3,7 @@ use std::fs;
 use std::path::Path;
 use std::process::{self, Command};
 
-use crate::rustc_info::get_file_name;
+use crate::rustc_info::{get_file_name, get_rustc_version};
 use crate::utils::{spawn_and_wait, try_hard_link};
 use crate::SysrootKind;
 
@@ -145,6 +145,24 @@ fn build_clif_sysroot_for_triple(
     triple: &str,
     linker: Option<&str>,
 ) {
+    match fs::read_to_string(Path::new("build_sysroot").join("rustc_version")) {
+        Err(e) => {
+            eprintln!("Failed to get rustc version for patched sysroot source: {}", e);
+            eprintln!("Hint: Try `./y.rs prepare` to patch the sysroot source");
+            process::exit(1);
+        }
+        Ok(source_version) => {
+            let rustc_version = get_rustc_version();
+            if source_version != rustc_version {
+                eprintln!("The patched sysroot source is outdated");
+                eprintln!("Source version: {}", source_version.trim());
+                eprintln!("Rustc version:  {}", rustc_version.trim());
+                eprintln!("Hint: Try `./y.rs prepare` to update the patched sysroot source");
+                process::exit(1);
+            }
+        }
+    }
+
     let build_dir = Path::new("build_sysroot").join("target").join(triple).join(channel);
 
     let keep_sysroot =

build_system/prepare.rs

@@ -5,7 +5,7 @@ use std::fs;
 use std::path::Path;
 use std::process::Command;
 
-use crate::rustc_info::{get_file_name, get_rustc_path};
+use crate::rustc_info::{get_file_name, get_rustc_path, get_rustc_version};
 use crate::utils::{copy_dir_recursively, spawn_and_wait};
 
 pub(crate) fn prepare() {
@@ -59,6 +59,13 @@ fn prepare_sysroot() {
     eprintln!("[COPY] sysroot src");
     copy_dir_recursively(&sysroot_src_orig.join("library"), &sysroot_src.join("library"));
 
+    let rustc_version = get_rustc_version();
+    fs::write(
+        Path::new("build_sysroot").join("rustc_version"),
+        &rustc_version,
+    )
+    .unwrap();
+
     eprintln!("[GIT] init");
     let mut git_init_cmd = Command::new("git");
     git_init_cmd.arg("init").arg("-q").current_dir(&sysroot_src);

build_system/rustc_info.rs

@@ -1,6 +1,12 @@
 use std::path::{Path, PathBuf};
 use std::process::{Command, Stdio};
 
+pub(crate) fn get_rustc_version() -> String {
+    let version_info =
+        Command::new("rustc").stderr(Stdio::inherit()).args(&["-V"]).output().unwrap().stdout;
+    String::from_utf8(version_info).unwrap()
+}
+
 pub(crate) fn get_host_triple() -> String {
     let version_info =
         Command::new("rustc").stderr(Stdio::inherit()).args(&["-vV"]).output().unwrap().stdout;

clean_all.sh

@@ -1,5 +1,6 @@
 #!/usr/bin/env bash
 set -e
 
-rm -rf target/ build/ build_sysroot/{sysroot_src/,target/,compiler-builtins/} perf.data{,.old}
+rm -rf build_sysroot/{sysroot_src/,target/,compiler-builtins/,rustc_version}
+rm -rf target/ build/ perf.data{,.old}
 rm -rf rand/ regex/ simple-raytracer/