From 501823b0bbf9128acf70a36bf27eca1dbc9adbb5 Mon Sep 17 00:00:00 2001
From: Aleksey Kladov <aleksey.kladov@gmail.com>
Date: Mon, 16 Apr 2018 18:50:25 +0300
Subject: [PATCH] Handle non-rustup cargo + rustup rustc in rustc cache

---
 src/cargo/util/config.rs         |  1 +
 src/cargo/util/rustc.rs          | 31 +++++++++++++++++++++++++------
 tests/testsuite/cargotest/mod.rs | 11 +++++++++--
 3 files changed, 35 insertions(+), 8 deletions(-)

diff --git a/src/cargo/util/config.rs b/src/cargo/util/config.rs
index 1dfefb8c8..c7a37e744 100644
--- a/src/cargo/util/config.rs
+++ b/src/cargo/util/config.rs
@@ -171,6 +171,7 @@ impl Config {
         Rustc::new(
             self.get_tool("rustc")?,
             self.maybe_get_tool("rustc_wrapper")?,
+            &self.home().join("bin").join("rustc").into_path_unlocked(),
             if self.cache_rustc_info {
                 cache_location
             } else {
diff --git a/src/cargo/util/rustc.rs b/src/cargo/util/rustc.rs
index b9ec492c2..53f74e130 100644
--- a/src/cargo/util/rustc.rs
+++ b/src/cargo/util/rustc.rs
@@ -35,11 +35,12 @@ impl Rustc {
     pub fn new(
         path: PathBuf,
         wrapper: Option<PathBuf>,
+        rustup_rustc: &Path,
         cache_location: Option<PathBuf>,
     ) -> CargoResult<Rustc> {
         let _p = profile::start("Rustc::new");
 
-        let mut cache = Cache::load(&path, cache_location);
+        let mut cache = Cache::load(&path, rustup_rustc, cache_location);
 
         let mut cmd = util::process(&path);
         cmd.arg("-vV");
@@ -86,6 +87,9 @@ impl Rustc {
 /// hundred milliseconds! Because we need compiler version info even for no-op
 /// builds, we cache it here, based on compiler's mtime and rustup's current
 /// toolchain.
+///
+/// https://github.com/rust-lang/cargo/issues/5315
+/// https://github.com/rust-lang/rust/issues/49761
 #[derive(Debug)]
 struct Cache {
     cache_location: Option<PathBuf>,
@@ -100,8 +104,8 @@ struct CacheData {
 }
 
 impl Cache {
-    fn load(rustc: &Path, cache_location: Option<PathBuf>) -> Cache {
-        match (cache_location, rustc_fingerprint(rustc)) {
+    fn load(rustc: &Path, rustup_rustc: &Path, cache_location: Option<PathBuf>) -> Cache {
+        match (cache_location, rustc_fingerprint(rustc, rustup_rustc)) {
             (Some(cache_location), Ok(rustc_fingerprint)) => {
                 let empty = CacheData {
                     rustc_fingerprint,
@@ -195,7 +199,7 @@ impl Drop for Cache {
     }
 }
 
-fn rustc_fingerprint(path: &Path) -> CargoResult<u64> {
+fn rustc_fingerprint(path: &Path, rustup_rustc: &Path) -> CargoResult<u64> {
     let mut hasher = SipHasher::new_with_keys(0, 0);
 
     let path = paths::resolve_executable(path)?;
@@ -203,8 +207,20 @@ fn rustc_fingerprint(path: &Path) -> CargoResult<u64> {
 
     paths::mtime(&path)?.hash(&mut hasher);
 
-    match (env::var("RUSTUP_HOME"), env::var("RUSTUP_TOOLCHAIN")) {
-        (Ok(rustup_home), Ok(rustup_toolchain)) => {
+    // Rustup can change the effective compiler without touching
+    // the `rustc` binary, so we try to account for this here.
+    // If we see rustup's env vars, we mix them into the fingerprint,
+    // but we also mix in the mtime of the actual compiler (and not
+    // the rustup shim at `~/.cargo/bin/rustup`), because `RUSTUP_TOOLCHAIN`
+    // could be just `stable-x86_64-unknown-linux-gnu`, i.e, it could
+    // not mention the version of Rust at all, which changes after
+    // `rustup update`.
+    //
+    // If we don't see rustup env vars, but it looks like the compiler
+    // is managed by rustup, we conservatively bail out.
+    let maybe_rustup = rustup_rustc == path;
+    match (maybe_rustup, env::var("RUSTUP_HOME"), env::var("RUSTUP_TOOLCHAIN")) {
+        (_, Ok(rustup_home), Ok(rustup_toolchain)) => {
             debug!("adding rustup info to rustc fingerprint");
             rustup_toolchain.hash(&mut hasher);
             rustup_home.hash(&mut hasher);
@@ -215,6 +231,9 @@ fn rustc_fingerprint(path: &Path) -> CargoResult<u64> {
                 .join("rustc");
             paths::mtime(&rustup_rustc)?.hash(&mut hasher);
         }
+        (true, _, _) => {
+            bail!("probably rustup rustc, but without rustup's env vars")
+        }
         _ => (),
     }
 
diff --git a/tests/testsuite/cargotest/mod.rs b/tests/testsuite/cargotest/mod.rs
index 23efab703..c2852ef14 100644
--- a/tests/testsuite/cargotest/mod.rs
+++ b/tests/testsuite/cargotest/mod.rs
@@ -3,14 +3,21 @@ use std::time::Duration;
 
 use cargo::util::Rustc;
 use cargo;
-use std::path::PathBuf;
+use std::path::{Path, PathBuf};
 
 #[macro_use]
 pub mod support;
 
 pub mod install;
 
-thread_local!(pub static RUSTC: Rustc = Rustc::new(PathBuf::from("rustc"), None, None).unwrap());
+thread_local!(
+pub static RUSTC: Rustc = Rustc::new(
+    PathBuf::from("rustc"),
+    None,
+    Path::new("should be path to rustup rustc, but we don't care in tests"),
+    None,
+).unwrap()
+);
 
 pub fn rustc_host() -> String {
     RUSTC.with(|r| r.host.clone())
-- 
2.30.2