1 files changed, 125 insertions, 0 deletions
diff --git a/compiler/rustc_session/src/filesearch.rs b/compiler/rustc_session/src/filesearch.rs
new file mode 100644
index 000000000..c973e3140
--- /dev/null
+++ b/compiler/rustc_session/src/filesearch.rs
@@ -0,0 +1,125 @@
+//! A module for searching for libraries
+
+use std::env;
+use std::fs;
+use std::iter::FromIterator;
+use std::path::{Path, PathBuf};
+
+use crate::search_paths::{PathKind, SearchPath};
+use rustc_fs_util::fix_windows_verbatim_for_gcc;
+use tracing::debug;
+
+#[derive(Copy, Clone)]
+pub enum FileMatch {
+    FileMatches,
+    FileDoesntMatch,
+}
+
+#[derive(Clone)]
+pub struct FileSearch<'a> {
+    sysroot: &'a Path,
+    triple: &'a str,
+    search_paths: &'a [SearchPath],
+    tlib_path: &'a SearchPath,
+    kind: PathKind,
+}
+
+impl<'a> FileSearch<'a> {
+    pub fn search_paths(&self) -> impl Iterator<Item = &'a SearchPath> {
+        let kind = self.kind;
+        self.search_paths
+            .iter()
+            .filter(move |sp| sp.kind.matches(kind))
+            .chain(std::iter::once(self.tlib_path))
+    }
+
+    pub fn get_lib_path(&self) -> PathBuf {
+        make_target_lib_path(self.sysroot, self.triple)
+    }
+
+    pub fn get_self_contained_lib_path(&self) -> PathBuf {
+        self.get_lib_path().join("self-contained")
+    }
+
+    pub fn new(
+        sysroot: &'a Path,
+        triple: &'a str,
+        search_paths: &'a [SearchPath],
+        tlib_path: &'a SearchPath,
+        kind: PathKind,
+    ) -> FileSearch<'a> {
+        debug!("using sysroot = {}, triple = {}", sysroot.display(), triple);
+        FileSearch { sysroot, triple, search_paths, tlib_path, kind }
+    }
+
+    /// Returns just the directories within the search paths.
+    pub fn search_path_dirs(&self) -> Vec<PathBuf> {
+        self.search_paths().map(|sp| sp.dir.to_path_buf()).collect()
+    }
+}
+
+pub fn make_target_lib_path(sysroot: &Path, target_triple: &str) -> PathBuf {
+    let rustlib_path = rustc_target::target_rustlib_path(sysroot, target_triple);
+    PathBuf::from_iter([sysroot, Path::new(&rustlib_path), Path::new("lib")])
+}
+
+/// This function checks if sysroot is found using env::args().next(), and if it
+/// is not found, uses env::current_exe() to imply sysroot.
+pub fn get_or_default_sysroot() -> PathBuf {
+    // Follow symlinks.  If the resolved path is relative, make it absolute.
+    fn canonicalize(path: PathBuf) -> PathBuf {
+        let path = fs::canonicalize(&path).unwrap_or(path);
+        // See comments on this target function, but the gist is that
+        // gcc chokes on verbatim paths which fs::canonicalize generates
+        // so we try to avoid those kinds of paths.
+        fix_windows_verbatim_for_gcc(&path)
+    }
+
+    // Use env::current_exe() to get the path of the executable following
+    // symlinks/canonicalizing components.
+    fn from_current_exe() -> PathBuf {
+        match env::current_exe() {
+            Ok(exe) => {
+                let mut p = canonicalize(exe);
+                p.pop();
+                p.pop();
+                p
+            }
+            Err(e) => panic!("failed to get current_exe: {e}"),
+        }
+    }
+
+    // Use env::args().next() to get the path of the executable without
+    // following symlinks/canonicalizing any component. This makes the rustc
+    // binary able to locate Rust libraries in systems using content-addressable
+    // storage (CAS).
+    fn from_env_args_next() -> Option<PathBuf> {
+        match env::args_os().next() {
+            Some(first_arg) => {
+                let mut p = PathBuf::from(first_arg);
+
+                // Check if sysroot is found using env::args().next() only if the rustc in argv[0]
+                // is a symlink (see #79253). We might want to change/remove it to conform with
+                // https://www.gnu.org/prep/standards/standards.html#Finding-Program-Files in the
+                // future.
+                if fs::read_link(&p).is_err() {
+                    // Path is not a symbolic link or does not exist.
+                    return None;
+                }
+
+                // Pop off `bin/rustc`, obtaining the suspected sysroot.
+                p.pop();
+                p.pop();
+                // Look for the target rustlib directory in the suspected sysroot.
+                let mut rustlib_path = rustc_target::target_rustlib_path(&p, "dummy");
+                rustlib_path.pop(); // pop off the dummy target.
+                if rustlib_path.exists() { Some(p) } else { None }
+            }
+            None => None,
+        }
+    }
+
+    // Check if sysroot is found using env::args().next(), and if is not found,
+    // use env::current_exe() to imply sysroot.
+    from_env_args_next().unwrap_or_else(from_current_exe)
+}