rustc_session: Add a structure for keeping both explicit and default sysroots

Also avoid creating and cloning sysroot unnecessarily.

Author: petrochenkov

Cargo.lock

@@ -3655,7 +3655,6 @@ dependencies = [
  "rustc_macros",
  "rustc_serialize",
  "rustc_span",
- "smallvec",
  "tracing",
  "unic-langid",
 ]
@@ -4446,7 +4445,6 @@ dependencies = [
  "rustc_serialize",
  "rustc_span",
  "rustc_target",
- "smallvec",
  "termize",
  "tracing",
  "windows",

compiler/rustc_codegen_ssa/src/back/link.rs

@@ -865,7 +865,7 @@ fn link_natively(
                     command: cmd,
                     escaped_output,
                     verbose: sess.opts.verbose,
-                    sysroot_dir: sess.sysroot.clone(),
+                    sysroot_dir: sess.opts.sysroot.path().to_owned(),
                 };
                 sess.dcx().emit_err(err);
                 // If MSVC's `link.exe` was expected but the return code
@@ -1249,10 +1249,10 @@ fn link_sanitizer_runtime(
         if path.exists() {
             sess.target_tlib_path.dir.clone()
         } else {
-            let default_sysroot = filesearch::get_or_default_sysroot();
-            let default_tlib =
-                filesearch::make_target_lib_path(&default_sysroot, sess.opts.target_triple.tuple());
-            default_tlib
+            filesearch::make_target_lib_path(
+                &sess.opts.sysroot.default,
+                sess.opts.target_triple.tuple(),
+            )
         }
     }
 
@@ -1758,7 +1758,7 @@ fn detect_self_contained_mingw(sess: &Session, linker: &Path) -> bool {
     for dir in env::split_paths(&env::var_os("PATH").unwrap_or_default()) {
         let full_path = dir.join(&linker_with_extension);
         // If linker comes from sysroot assume self-contained mode
-        if full_path.is_file() && !full_path.starts_with(&sess.sysroot) {
+        if full_path.is_file() && !full_path.starts_with(sess.opts.sysroot.path()) {
             return false;
         }
     }

compiler/rustc_codegen_ssa/src/back/linker.rs

@@ -1059,7 +1059,7 @@ impl<'a> Linker for MsvcLinker<'a> {
         self.link_arg("/PDBALTPATH:%_PDB%");
 
         // This will cause the Microsoft linker to embed .natvis info into the PDB file
-        let natvis_dir_path = self.sess.sysroot.join("lib\\rustlib\\etc");
+        let natvis_dir_path = self.sess.opts.sysroot.path().join("lib\\rustlib\\etc");
         if let Ok(natvis_dir) = fs::read_dir(&natvis_dir_path) {
             for entry in natvis_dir {
                 match entry {

compiler/rustc_driver_impl/src/lib.rs

@@ -53,13 +53,13 @@ use rustc_metadata::locator;
 use rustc_middle::ty::TyCtxt;
 use rustc_parse::{new_parser_from_file, new_parser_from_source_str, unwrap_or_emit_fatal};
 use rustc_session::config::{
-    CG_OPTIONS, CrateType, ErrorOutputType, Input, OptionDesc, OutFileName, OutputType,
+    CG_OPTIONS, CrateType, ErrorOutputType, Input, OptionDesc, OutFileName, OutputType, Sysroot,
     UnstableOptions, Z_OPTIONS, nightly_options, parse_target_triple,
 };
 use rustc_session::getopts::{self, Matches};
 use rustc_session::lint::{Lint, LintId};
 use rustc_session::output::{CRATE_TYPES, collect_crate_types, invalid_output_for_target};
-use rustc_session::{EarlyDiagCtxt, Session, config, filesearch};
+use rustc_session::{EarlyDiagCtxt, Session, config};
 use rustc_span::FileName;
 use rustc_span::def_id::LOCAL_CRATE;
 use rustc_target::json::ToJson;
@@ -662,7 +662,7 @@ fn print_crate_info(
                 println_info!("{}", targets.join("\n"));
             }
             HostTuple => println_info!("{}", rustc_session::config::host_tuple()),
-            Sysroot => println_info!("{}", sess.sysroot.display()),
+            Sysroot => println_info!("{}", sess.opts.sysroot.path().display()),
             TargetLibdir => println_info!("{}", sess.target_tlib_path.dir.display()),
             TargetSpecJson => {
                 println_info!("{}", serde_json::to_string_pretty(&sess.target.to_json()).unwrap());
@@ -1114,8 +1114,8 @@ fn get_backend_from_raw_matches(
     let debug_flags = matches.opt_strs("Z");
     let backend_name = debug_flags.iter().find_map(|x| x.strip_prefix("codegen-backend="));
     let target = parse_target_triple(early_dcx, matches);
-    let sysroot = filesearch::materialize_sysroot(matches.opt_str("sysroot").map(PathBuf::from));
-    let target = config::build_target_config(early_dcx, &target, &sysroot);
+    let sysroot = Sysroot::new(matches.opt_str("sysroot").map(PathBuf::from));
+    let target = config::build_target_config(early_dcx, &target, sysroot.path());
 
     get_codegen_backend(early_dcx, &sysroot, backend_name, &target)
 }

compiler/rustc_error_messages/Cargo.toml

@@ -16,7 +16,6 @@ rustc_data_structures = { path = "../rustc_data_structures" }
 rustc_macros = { path = "../rustc_macros" }
 rustc_serialize = { path = "../rustc_serialize" }
 rustc_span = { path = "../rustc_span" }
-smallvec = { version = "1.8.1", features = ["union", "may_dangle"] }
 tracing = "0.1"
 unic-langid = { version = "0.9.0", features = ["macros"] }
 # tidy-alphabetical-end

compiler/rustc_error_messages/src/lib.rs

@@ -1,14 +1,15 @@
 // tidy-alphabetical-start
 #![allow(internal_features)]
 #![doc(rust_logo)]
+#![feature(anonymous_lifetime_in_impl_trait)]
 #![feature(rustc_attrs)]
 #![feature(rustdoc_internals)]
 #![feature(type_alias_impl_trait)]
 // tidy-alphabetical-end
 
 use std::borrow::Cow;
 use std::error::Error;
-use std::path::{Path, PathBuf};
+use std::path::Path;
 use std::sync::{Arc, LazyLock};
 use std::{fmt, fs, io};
 
@@ -21,7 +22,6 @@ use intl_memoizer::concurrent::IntlLangMemoizer;
 use rustc_data_structures::sync::{DynSend, IntoDynSyncSend};
 use rustc_macros::{Decodable, Encodable};
 use rustc_span::Span;
-use smallvec::SmallVec;
 use tracing::{instrument, trace};
 pub use unic_langid::{LanguageIdentifier, langid};
 
@@ -107,7 +107,7 @@ impl From<Vec<FluentError>> for TranslationBundleError {
 /// (overriding any conflicting messages).
 #[instrument(level = "trace")]
 pub fn fluent_bundle(
-    sysroot_candidates: SmallVec<[PathBuf; 2]>,
+    sysroot_candidates: &[&Path],
     requested_locale: Option<LanguageIdentifier>,
     additional_ftl_path: Option<&Path>,
     with_directionality_markers: bool,
@@ -141,7 +141,8 @@ pub fn fluent_bundle(
     // If the user requests the default locale then don't try to load anything.
     if let Some(requested_locale) = requested_locale {
         let mut found_resources = false;
-        for mut sysroot in sysroot_candidates {
+        for sysroot in sysroot_candidates {
+            let mut sysroot = sysroot.to_path_buf();
             sysroot.push("share");
             sysroot.push("locale");
             sysroot.push(requested_locale.to_string());

compiler/rustc_interface/src/interface.rs

@@ -18,7 +18,6 @@ use rustc_parse::parser::attr::AllowLeadingUnsafe;
 use rustc_query_impl::QueryCtxt;
 use rustc_query_system::query::print_query_stack;
 use rustc_session::config::{self, Cfg, CheckCfg, ExpectedValues, Input, OutFileName};
-use rustc_session::filesearch::sysroot_with_fallback;
 use rustc_session::parse::ParseSess;
 use rustc_session::{CompilerIO, EarlyDiagCtxt, Session, lint};
 use rustc_span::source_map::{FileLoader, RealFileLoader, SourceMapInputs};
@@ -405,8 +404,11 @@ pub fn run_compiler<R: Send>(config: Config, f: impl FnOnce(&Compiler) -> R + Se
 
     crate::callbacks::setup_callbacks();
 
-    let sysroot = config.opts.sysroot.clone();
-    let target = config::build_target_config(&early_dcx, &config.opts.target_triple, &sysroot);
+    let target = config::build_target_config(
+        &early_dcx,
+        &config.opts.target_triple,
+        config.opts.sysroot.path(),
+    );
     let file_loader = config.file_loader.unwrap_or_else(|| Box::new(RealFileLoader));
     let path_mapping = config.opts.file_path_mapping();
     let hash_kind = config.opts.unstable_opts.src_hash_algorithm(&target);
@@ -426,7 +428,7 @@ pub fn run_compiler<R: Send>(config: Config, f: impl FnOnce(&Compiler) -> R + Se
             let codegen_backend = match config.make_codegen_backend {
                 None => util::get_codegen_backend(
                     &early_dcx,
-                    &sysroot,
+                    &config.opts.sysroot,
                     config.opts.unstable_opts.codegen_backend.as_deref(),
                     &target,
                 ),
@@ -440,7 +442,7 @@ pub fn run_compiler<R: Send>(config: Config, f: impl FnOnce(&Compiler) -> R + Se
             let temps_dir = config.opts.unstable_opts.temps_dir.as_deref().map(PathBuf::from);
 
             let bundle = match rustc_errors::fluent_bundle(
-                sysroot_with_fallback(&config.opts.sysroot),
+                &config.opts.sysroot.all_paths().collect::<Vec<_>>(),
                 config.opts.unstable_opts.translate_lang.clone(),
                 config.opts.unstable_opts.translate_additional_ftl.as_deref(),
                 config.opts.unstable_opts.translate_directionality_markers,
@@ -469,7 +471,6 @@ pub fn run_compiler<R: Send>(config: Config, f: impl FnOnce(&Compiler) -> R + Se
                 locale_resources,
                 config.lint_caps,
                 target,
-                sysroot,
                 util::rustc_version_str().unwrap_or("unknown"),
                 config.ice_file,
                 config.using_internal_features,

compiler/rustc_interface/src/tests.rs

@@ -41,9 +41,11 @@ where
 
     let matches = optgroups().parse(args).unwrap();
     let sessopts = build_session_options(&mut early_dcx, &matches);
-    let sysroot = sessopts.sysroot.clone();
-    let target =
-        rustc_session::config::build_target_config(&early_dcx, &sessopts.target_triple, &sysroot);
+    let target = rustc_session::config::build_target_config(
+        &early_dcx,
+        &sessopts.target_triple,
+        sessopts.sysroot.path(),
+    );
     let hash_kind = sessopts.unstable_opts.src_hash_algorithm(&target);
     let checksum_hash_kind = sessopts.unstable_opts.checksum_hash_algorithm();
     let sm_inputs = Some(SourceMapInputs {
@@ -72,7 +74,6 @@ where
             vec![],
             Default::default(),
             target,
-            sysroot,
             "",
             None,
             &USING_INTERNAL_FEATURES,

compiler/rustc_interface/src/util.rs

@@ -11,7 +11,7 @@ use rustc_data_structures::sync;
 use rustc_metadata::{DylibError, load_symbol_from_dylib};
 use rustc_middle::ty::CurrentGcx;
 use rustc_parse::validate_attr;
-use rustc_session::config::{Cfg, OutFileName, OutputFilenames, OutputTypes, host_tuple};
+use rustc_session::config::{Cfg, OutFileName, OutputFilenames, OutputTypes, Sysroot, host_tuple};
 use rustc_session::lint::{self, BuiltinLintDiag, LintBuffer};
 use rustc_session::output::{CRATE_TYPES, categorize_crate_type};
 use rustc_session::{EarlyDiagCtxt, Session, filesearch};
@@ -305,7 +305,7 @@ fn load_backend_from_dylib(early_dcx: &EarlyDiagCtxt, path: &Path) -> MakeBacken
 /// A name of `None` indicates that the default backend should be used.
 pub fn get_codegen_backend(
     early_dcx: &EarlyDiagCtxt,
-    sysroot: &Path,
+    sysroot: &Sysroot,
     backend_name: Option<&str>,
     target: &Target,
 ) -> Box<dyn CodegenBackend> {
@@ -336,25 +336,24 @@ pub fn get_codegen_backend(
 // This is used for rustdoc, but it uses similar machinery to codegen backend
 // loading, so we leave the code here. It is potentially useful for other tools
 // that want to invoke the rustc binary while linking to rustc as well.
-pub fn rustc_path<'a>() -> Option<&'a Path> {
+pub fn rustc_path<'a>(sysroot: &Sysroot) -> Option<&'a Path> {
     static RUSTC_PATH: OnceLock<Option<PathBuf>> = OnceLock::new();
 
-    const BIN_PATH: &str = env!("RUSTC_INSTALL_BINDIR");
-
-    RUSTC_PATH.get_or_init(|| get_rustc_path_inner(BIN_PATH)).as_deref()
-}
-
-fn get_rustc_path_inner(bin_path: &str) -> Option<PathBuf> {
-    let candidate = filesearch::get_or_default_sysroot()
-        .join(bin_path)
-        .join(if cfg!(target_os = "windows") { "rustc.exe" } else { "rustc" });
-    candidate.exists().then_some(candidate)
+    RUSTC_PATH
+        .get_or_init(|| {
+            let candidate = sysroot
+                .default
+                .join(env!("RUSTC_INSTALL_BINDIR"))
+                .join(if cfg!(target_os = "windows") { "rustc.exe" } else { "rustc" });
+            candidate.exists().then_some(candidate)
+        })
+        .as_deref()
 }
 
 #[allow(rustc::untranslatable_diagnostic)] // FIXME: make this translatable
 fn get_codegen_sysroot(
     early_dcx: &EarlyDiagCtxt,
-    sysroot: &Path,
+    sysroot: &Sysroot,
     backend_name: &str,
 ) -> MakeBackendFn {
     // For now we only allow this function to be called once as it'll dlopen a
@@ -369,10 +368,9 @@ fn get_codegen_sysroot(
     );
 
     let target = host_tuple();
-    let sysroot_candidates = filesearch::sysroot_with_fallback(&sysroot);
 
-    let sysroot = sysroot_candidates
-        .iter()
+    let sysroot = sysroot
+        .all_paths()
         .map(|sysroot| {
             filesearch::make_target_lib_path(sysroot, target).with_file_name("codegen-backends")
         })
@@ -381,8 +379,8 @@ fn get_codegen_sysroot(
             f.exists()
         })
         .unwrap_or_else(|| {
-            let candidates = sysroot_candidates
-                .iter()
+            let candidates = sysroot
+                .all_paths()
                 .map(|p| p.display().to_string())
                 .collect::<Vec<_>>()
                 .join("\n* ");

compiler/rustc_metadata/src/locator.rs

@@ -321,7 +321,7 @@ impl<'a> CrateLocator<'a> {
 
         CrateLocator {
             only_needs_metadata,
-            sysroot: &sess.sysroot,
+            sysroot: sess.opts.sysroot.path(),
             metadata_loader,
             cfg_version: sess.cfg_version,
             crate_name,

compiler/rustc_session/Cargo.toml

@@ -22,7 +22,6 @@ rustc_macros = { path = "../rustc_macros" }
 rustc_serialize = { path = "../rustc_serialize" }
 rustc_span = { path = "../rustc_span" }
 rustc_target = { path = "../rustc_target" }
-smallvec = "1.8.1"
 termize = "0.1.1"
 tracing = "0.1"
 # tidy-alphabetical-end

compiler/rustc_session/src/config.rs

@@ -1296,6 +1296,28 @@ bitflags::bitflags! {
     }
 }
 
+#[derive(Clone, Debug)]
+pub struct Sysroot {
+    pub explicit: Option<PathBuf>,
+    pub default: PathBuf,
+}
+
+impl Sysroot {
+    pub fn new(explicit: Option<PathBuf>) -> Sysroot {
+        Sysroot { explicit, default: filesearch::default_sysroot() }
+    }
+
+    /// Return explicit sysroot if it was passed with `--sysroot`, or default sysroot otherwise.
+    pub fn path(&self) -> &Path {
+        self.explicit.as_deref().unwrap_or(&self.default)
+    }
+
+    /// Returns both explicit sysroot if it was passed with `--sysroot` and the default sysroot.
+    pub fn all_paths(&self) -> impl Iterator<Item = &Path> {
+        self.explicit.as_deref().into_iter().chain(iter::once(&*self.default))
+    }
+}
+
 pub fn host_tuple() -> &'static str {
     // Get the host triple out of the build environment. This ensures that our
     // idea of the host triple is the same as for the set of libraries we've
@@ -1342,7 +1364,7 @@ impl Default for Options {
             describe_lints: false,
             output_types: OutputTypes(BTreeMap::new()),
             search_paths: vec![],
-            sysroot: filesearch::materialize_sysroot(None),
+            sysroot: Sysroot::new(None),
             target_triple: TargetTuple::from_tuple(host_tuple()),
             test: false,
             incremental: None,
@@ -2673,7 +2695,6 @@ pub fn build_session_options(early_dcx: &mut EarlyDiagCtxt, matches: &getopts::M
 
     let cg = cg;
 
-    let sysroot_opt = matches.opt_str("sysroot").map(|m| PathBuf::from(&m));
     let target_triple = parse_target_triple(early_dcx, matches);
     let opt_level = parse_opt_level(early_dcx, matches, &cg);
     // The `-g` and `-C debuginfo` flags specify the same setting, so we want to be able
@@ -2712,10 +2733,10 @@ pub fn build_session_options(early_dcx: &mut EarlyDiagCtxt, matches: &getopts::M
 
     let logical_env = parse_logical_env(early_dcx, matches);
 
-    let sysroot = filesearch::materialize_sysroot(sysroot_opt);
+    let sysroot = Sysroot::new(matches.opt_str("sysroot").map(PathBuf::from));
 
     let real_source_base_dir = |suffix: &str, confirm: &str| {
-        let mut candidate = sysroot.join(suffix);
+        let mut candidate = sysroot.path().join(suffix);
         if let Ok(metadata) = candidate.symlink_metadata() {
             // Replace the symlink bootstrap creates, with its destination.
             // We could try to use `fs::canonicalize` instead, but that might
@@ -2742,7 +2763,7 @@ pub fn build_session_options(early_dcx: &mut EarlyDiagCtxt, matches: &getopts::M
     let mut search_paths = vec![];
     for s in &matches.opt_strs("L") {
         search_paths.push(SearchPath::from_cli_opt(
-            &sysroot,
+            sysroot.path(),
             &target_triple,
             early_dcx,
             s,