Skip to content

Commit

Permalink
Add an optimization when running under rustup.
Browse files Browse the repository at this point in the history
  • Loading branch information
ehuss committed Mar 31, 2023
1 parent 18ed848 commit 7263f3b
Show file tree
Hide file tree
Showing 2 changed files with 42 additions and 2 deletions.
42 changes: 42 additions & 0 deletions src/cargo/util/config/mod.rs
Original file line number Diff line number Diff line change
Expand Up @@ -1644,6 +1644,48 @@ impl Config {
/// as a path.
fn get_tool(&self, tool: &str, from_config: &Option<ConfigRelativePath>) -> PathBuf {
self.maybe_get_tool(tool, from_config)
.or_else(|| {
// This is an optimization to circumvent the rustup proxies
// which can have a significant performance hit. The goal here
// is to determine if calling `rustc` from PATH would end up
// calling the proxies.
//
// This is somewhat cautious trying to determine if it is safe
// to circumvent rustup, because there are some situations
// where users may do things like modify PATH, call cargo
// directly, use a custom rustup toolchain link without a
// cargo executable, etc. However, there is still some risk
// this may make the wrong decision in unusual circumstances.
//
// First, we must be running under rustup in the first place.
let toolchain = self.get_env_os("RUSTUP_TOOLCHAIN")?;
// If the tool on PATH is the same as `rustup` on path, then
// there is pretty good evidence that it will be a proxy.
let tool_resolved = paths::resolve_executable(Path::new(tool)).ok()?;
let rustup_resolved = paths::resolve_executable(Path::new("rustup")).ok()?;
let tool_meta = tool_resolved.metadata().ok()?;
let rustup_meta = rustup_resolved.metadata().ok()?;
// This works on the assumption that rustup and its proxies
// use hard links to a single binary. If rustup ever changes
// that setup, then I think the worst consequence is that this
// optimization will not work, and it will take the slow path.
if tool_meta.len() != rustup_meta.len() {
return None;
}
// Try to find the tool in rustup's toolchain directory.
let tool_exe = Path::new(tool).with_extension(env::consts::EXE_EXTENSION);
let toolchain_exe = home::rustup_home()
.ok()?
.join("toolchains")
.join(&toolchain)
.join("bin")
.join(&tool_exe);
if toolchain_exe.exists() {
Some(toolchain_exe)
} else {
None
}
})
.unwrap_or_else(|| PathBuf::from(tool))
}

Expand Down
2 changes: 0 additions & 2 deletions tests/testsuite/rustup.rs
Original file line number Diff line number Diff line change
Expand Up @@ -165,7 +165,6 @@ fn typical_rustup() {
.with_stderr(
"\
[CHECKING] foo v0.0.1 [..]
rustc proxy running
real rustc running
[FINISHED] [..]
",
Expand All @@ -184,7 +183,6 @@ real rustc running
.with_stderr(
"\
[CHECKING] foo v0.0.1 [..]
rustc proxy running
real rustc running
[FINISHED] [..]
",
Expand Down

0 comments on commit 7263f3b

Please sign in to comment.