RustPython
diff --git a/Lib/test/test_importlib/resources/test_files.py b/Lib/test/test_importlib/resources/test_files.py
@@ -52,7 +52,7 @@ class OpenDiskTests(FilesTests, unittest.TestCase):
     def setUp(self):
         self.data = data01
 
-    @unittest.expectedFailureIfWindows("TODO: RUSTPYTHON")
+    @unittest.expectedFailureIfWindows("TODO: RUSTPYTHON, line ending issue")
     def test_read_bytes(self):
         super().test_read_bytes()
 
@@ -67,10 +67,11 @@ def setUp(self):
 
         self.data = namespacedata01
 
-    @unittest.expectedFailureIfWindows("TODO: RUSTPYTHON")
+    @unittest.expectedFailureIfWindows("TODO: RUSTPYTHON, line ending issue")
     def test_read_bytes(self):
         super().test_read_bytes()
 
+
 class SiteDir:
     def setUp(self):
         self.fixtures = contextlib.ExitStack()

diff --git a/Lib/test/test_sys.py b/Lib/test/test_sys.py
@@ -1310,7 +1310,6 @@ def test_module_names(self):
         for name in sys.stdlib_module_names:
             self.assertIsInstance(name, str)
 
-    @unittest.expectedFailure # TODO: RUSTPYTHON; AttributeError: module 'sys' has no attribute '_stdlib_dir'
     def test_stdlib_dir(self):
         os = import_helper.import_fresh_module('os')
         marker = getattr(os, '__file__', None)

diff --git a/crates/pylib/build.rs b/crates/pylib/build.rs
@@ -11,15 +11,25 @@ fn main() {
         process_python_libs("./Lib/**/*");
     }
 
-    if cfg!(windows)
-        && let Ok(real_path) = std::fs::read_to_string("Lib")
-    {
-        let canonicalized_path = std::fs::canonicalize(real_path)
-            .expect("failed to resolve RUSTPYTHONPATH during build time");
-        // Strip the extended path prefix (\\?\) that canonicalize adds on Windows
-        let path_str = canonicalized_path.to_str().unwrap();
-        let path_str = path_str.strip_prefix(r"\\?\").unwrap_or(path_str);
-        println!("cargo:rustc-env=win_lib_path={path_str}");
+    if cfg!(windows) {
+        // On Windows, the Lib entry can be either:
+        // 1. A text file containing the relative path (git without symlink support)
+        // 2. A proper symlink (git with symlink support)
+        // We handle both cases to resolve to the actual Lib directory.
+        let lib_path = if let Ok(real_path) = std::fs::read_to_string("Lib") {
+            // Case 1: Text file containing relative path
+            std::path::PathBuf::from(real_path.trim())
+        } else {
+            // Case 2: Symlink or directory - canonicalize directly
+            std::path::PathBuf::from("Lib")
+        };
+
+        if let Ok(canonicalized_path) = std::fs::canonicalize(&lib_path) {
+            // Strip the extended path prefix (\\?\) that canonicalize adds on Windows
+            let path_str = canonicalized_path.to_str().unwrap();
+            let path_str = path_str.strip_prefix(r"\\?\").unwrap_or(path_str);
+            println!("cargo:rustc-env=win_lib_path={path_str}");
+        }
     }
 }
 

diff --git a/crates/vm/src/getpath.rs b/crates/vm/src/getpath.rs
@@ -174,6 +174,9 @@ pub fn init_path_config(settings: &Settings) -> Paths {
     paths.module_search_paths =
         build_module_search_paths(settings, &paths.prefix, &paths.exec_prefix);
 
+    // Step 9: Calculate stdlib_dir
+    paths.stdlib_dir = calculate_stdlib_dir(&paths.prefix);
+
     paths
 }
 
@@ -301,6 +304,22 @@ fn calculate_base_executable(executable: Option<&PathBuf>, home_dir: &Option<Pat
         .unwrap_or_default()
 }
 
+/// Calculate stdlib_dir (sys._stdlib_dir)
+/// Returns None if the stdlib directory doesn't exist
+fn calculate_stdlib_dir(prefix: &str) -> Option<String> {
+    #[cfg(not(windows))]
+    let stdlib_dir = PathBuf::from(prefix).join(platform::stdlib_subdir());
+
+    #[cfg(windows)]
+    let stdlib_dir = PathBuf::from(prefix).join(platform::STDLIB_SUBDIR);
+
+    if stdlib_dir.is_dir() {
+        Some(stdlib_dir.to_string_lossy().into_owned())
+    } else {
+        None
+    }
+}
+
 /// Build the complete module_search_paths (sys.path)
 fn build_module_search_paths(settings: &Settings, prefix: &str, exec_prefix: &str) -> Vec<String> {
     let mut paths = Vec::new();

diff --git a/crates/vm/src/stdlib/sys.rs b/crates/vm/src/stdlib/sys.rs
@@ -148,6 +148,10 @@ mod sys {
     fn platlibdir(_vm: &VirtualMachine) -> &'static str {
         option_env!("RUSTPYTHON_PLATLIBDIR").unwrap_or("lib")
     }
+    #[pyattr]
+    fn _stdlib_dir(vm: &VirtualMachine) -> PyObjectRef {
+        vm.state.config.paths.stdlib_dir.clone().to_pyobject(vm)
+    }
 
     // alphabetical order with segments of pyattr and others
 

diff --git a/crates/vm/src/vm/setting.rs b/crates/vm/src/vm/setting.rs
@@ -16,6 +16,8 @@ pub struct Paths {
     pub exec_prefix: String,
     /// sys.base_exec_prefix
     pub base_exec_prefix: String,
+    /// sys._stdlib_dir
+    pub stdlib_dir: Option<String>,
     /// Computed module_search_paths (complete sys.path)
     pub module_search_paths: Vec<String>,
 }

diff --git a/src/interpreter.rs b/src/interpreter.rs
@@ -113,18 +113,13 @@ pub fn init_stdlib(vm: &mut VirtualMachine) {
 /// Setup frozen standard library (compiled into the binary)
 #[cfg(all(feature = "stdlib", feature = "freeze-stdlib"))]
 fn setup_frozen_stdlib(vm: &mut VirtualMachine) {
+    use rustpython_vm::common::rc::PyRc;
+
     vm.add_frozen(rustpython_pylib::FROZEN_STDLIB);
 
-    // FIXME: Remove this hack once sys._stdlib_dir is properly implemented
-    // or _frozen_importlib doesn't depend on it anymore.
-    assert!(vm.sys_module.get_attr("_stdlib_dir", vm).is_err());
-    vm.sys_module
-        .set_attr(
-            "_stdlib_dir",
-            vm.new_pyobj(rustpython_pylib::LIB_PATH.to_owned()),
-            vm,
-        )
-        .unwrap();
+    // Set stdlib_dir to the frozen stdlib path
+    let state = PyRc::get_mut(&mut vm.state).unwrap();
+    state.config.paths.stdlib_dir = Some(rustpython_pylib::LIB_PATH.to_owned());
 }
 
 /// Setup dynamic standard library loading from filesystem
@@ -135,6 +130,11 @@ fn setup_dynamic_stdlib(vm: &mut VirtualMachine) {
     let state = PyRc::get_mut(&mut vm.state).unwrap();
     let paths = collect_stdlib_paths();
 
+    // Set stdlib_dir to the first stdlib path if available
+    if let Some(first_path) = paths.first() {
+        state.config.paths.stdlib_dir = Some(first_path.clone());
+    }
+
     // Insert at the beginning so stdlib comes before user paths
     for path in paths.into_iter().rev() {
         state.config.paths.module_search_paths.insert(0, path);