linker: Pass fewer search directories to the linker

compiler/rustc_codegen_ssa/src/back/link.rs

@@ -2065,17 +2065,61 @@ fn add_local_crate_metadata_objects(
 }
 
 /// Add sysroot and other globally set directories to the directory search list.
-fn add_library_search_dirs(cmd: &mut dyn Linker, sess: &Session, self_contained: bool) {
-    // The default library location, we need this to find the runtime.
-    // The location of crates will be determined as needed.
-    let lib_path = sess.target_filesearch(PathKind::All).get_lib_path();
-    cmd.include_path(&fix_windows_verbatim_for_gcc(&lib_path));
+fn add_library_search_dirs(
+    cmd: &mut dyn Linker,
+    sess: &Session,
+    self_contained_components: LinkSelfContainedComponents,
+    apple_sdk_root: Option<&Path>,
+) {
+    if !sess.opts.unstable_opts.link_native_libraries {
+        return;
+    }
 
-    // Special directory with libraries used only in self-contained linkage mode
-    if self_contained {
-        let lib_path = sess.target_filesearch(PathKind::All).get_self_contained_lib_path();
+    // Library search paths explicitly supplied by user (`-L` on the command line).
+    for search_path in sess.target_filesearch(PathKind::Native).cli_search_paths() {
+        cmd.include_path(&fix_windows_verbatim_for_gcc(&search_path.dir));
+    }
+    for search_path in sess.target_filesearch(PathKind::Framework).cli_search_paths() {
+        // Contrary to the `-L` docs only framework-specific paths are considered here.
+        if search_path.kind != PathKind::All {
+            cmd.framework_path(&search_path.dir);
+        }
+    }
+
+    // The toolchain ships some native library components and self-contained linking was enabled.
+    // Add the self-contained library directory to search paths.
+    if self_contained_components.intersects(
+        LinkSelfContainedComponents::LIBC
+            | LinkSelfContainedComponents::UNWIND
+            | LinkSelfContainedComponents::MINGW,
+    ) {
+        let lib_path = sess.target_filesearch(PathKind::Native).get_self_contained_lib_path();
         cmd.include_path(&fix_windows_verbatim_for_gcc(&lib_path));
     }
+
+    // Toolchains for some targets may ship `libunwind.a`, but place it into the main sysroot
+    // library directory instead of the self-contained directories.
+    // Sanitizer libraries have the same issue and are also linked by name on Apple targets.
+    // The targets here should be in sync with `copy_third_party_objects` in bootstrap.
+    // FIXME: implement `-Clink-self-contained=+/-unwind,+/-sanitizers`, move the shipped libunwind
+    // and sanitizers to self-contained directory, and stop adding this search path.
+    if sess.target.vendor == "fortanix"
+        || sess.target.os == "linux"
+        || sess.target.os == "fuchsia"
+        || sess.target.is_like_osx && !sess.opts.unstable_opts.sanitizer.is_empty()
+    {
+        let lib_path = sess.target_filesearch(PathKind::Native).get_lib_path();
+        cmd.include_path(&fix_windows_verbatim_for_gcc(&lib_path));
+    }
+
+    // Mac Catalyst uses the macOS SDK, but to link to iOS-specific frameworks
+    // we must have the support library stubs in the library search path (#121430).
+    if let Some(sdk_root) = apple_sdk_root
+        && sess.target.llvm_target.contains("macabi")
+    {
+        cmd.include_path(&sdk_root.join("System/iOSSupport/usr/lib"));
+        cmd.framework_path(&sdk_root.join("System/iOSSupport/System/Library/Frameworks"));
+    }
 }
 
 /// Add options making relocation sections in the produced ELF files read-only
@@ -2367,7 +2411,7 @@ fn add_order_independent_options(
     // Take care of the flavors and CLI options requesting the `lld` linker.
     add_lld_args(cmd, sess, flavor, self_contained_components);
 
-    add_apple_sdk(cmd, sess, flavor);
+    let apple_sdk_root = add_apple_sdk(cmd, sess, flavor);
 
     add_link_script(cmd, sess, tmpdir, crate_type);
 
@@ -2423,7 +2467,7 @@ fn add_order_independent_options(
 
     cmd.linker_plugin_lto();
 
-    add_library_search_dirs(cmd, sess, self_contained_components.are_any_components_enabled());
+    add_library_search_dirs(cmd, sess, self_contained_components, apple_sdk_root.as_deref());
 
     cmd.output_filename(out_filename);
 
@@ -2637,19 +2681,6 @@ fn add_local_native_libraries(
     tmpdir: &Path,
     link_output_kind: LinkOutputKind,
 ) {
-    if sess.opts.unstable_opts.link_native_libraries {
-        // User-supplied library search paths (-L on the command line). These are the same paths
-        // used to find Rust crates, so some of them may have been added already by the previous
-        // crate linking code. This only allows them to be found at compile time so it is still
-        // entirely up to outside forces to make sure that library can be found at runtime.
-        for search_path in sess.target_filesearch(PathKind::All).search_paths() {
-            match search_path.kind {
-                PathKind::Framework => cmd.framework_path(&search_path.dir),
-                _ => cmd.include_path(&fix_windows_verbatim_for_gcc(&search_path.dir)),
-            }
-        }
-    }
-
     // All static and dynamic native library dependencies are linked to the local crate.
     let link_static = true;
     let link_dynamic = true;
@@ -2944,19 +2975,19 @@ pub(crate) fn are_upstream_rust_objects_already_included(sess: &Session) -> bool
     }
 }
 
-fn add_apple_sdk(cmd: &mut dyn Linker, sess: &Session, flavor: LinkerFlavor) {
+fn add_apple_sdk(cmd: &mut dyn Linker, sess: &Session, flavor: LinkerFlavor) -> Option<PathBuf> {
     let arch = &sess.target.arch;
     let os = &sess.target.os;
     let llvm_target = &sess.target.llvm_target;
     if sess.target.vendor != "apple"
         || !matches!(os.as_ref(), "ios" | "tvos" | "watchos" | "visionos" | "macos")
         || !matches!(flavor, LinkerFlavor::Darwin(..))
     {
-        return;
+        return None;
     }
 
     if os == "macos" && !matches!(flavor, LinkerFlavor::Darwin(Cc::No, _)) {
-        return;
+        return None;
     }
 
     let sdk_name = match (arch.as_ref(), os.as_ref()) {
@@ -2980,14 +3011,14 @@ fn add_apple_sdk(cmd: &mut dyn Linker, sess: &Session, flavor: LinkerFlavor) {
         (_, "macos") => "macosx",
         _ => {
             sess.dcx().emit_err(errors::UnsupportedArch { arch, os });
-            return;
+            return None;
         }
     };
     let sdk_root = match get_apple_sdk_root(sdk_name) {
         Ok(s) => s,
         Err(e) => {
             sess.dcx().emit_err(e);
-            return;
+            return None;
         }
     };
 
@@ -3007,16 +3038,7 @@ fn add_apple_sdk(cmd: &mut dyn Linker, sess: &Session, flavor: LinkerFlavor) {
         _ => unreachable!(),
     }
 
-    if llvm_target.contains("macabi") {
-        // Mac Catalyst uses the macOS SDK, but to link to iOS-specific
-        // frameworks, we must have the support library stubs in the library
-        // search path.
-
-        // The flags are called `-L` and `-F` both in Clang, ld64 and ldd.
-        let sdk_root = Path::new(&sdk_root);
-        cmd.include_path(&sdk_root.join("System/iOSSupport/usr/lib"));
-        cmd.framework_path(&sdk_root.join("System/iOSSupport/System/Library/Frameworks"));
-    }
+    Some(sdk_root.into())
 }
 
 fn get_apple_sdk_root(sdk_name: &str) -> Result<String, errors::AppleSdkRootError<'_>> {

compiler/rustc_session/src/filesearch.rs

@@ -19,6 +19,11 @@ pub struct FileSearch<'a> {
 }
 
 impl<'a> FileSearch<'a> {
+    pub fn cli_search_paths(&self) -> impl Iterator<Item = &'a SearchPath> {
+        let kind = self.kind;
+        self.cli_search_paths.iter().filter(move |sp| sp.kind.matches(kind))
+    }
+
     pub fn search_paths(&self) -> impl Iterator<Item = &'a SearchPath> {
         let kind = self.kind;
         self.cli_search_paths