core/std: Fix race condition in os::mkdir_recursive tests

Added a change_dir_locked function to os, and use it in the
mkdir_recursive tests so that the tests don't clobber each other's
directory changes.

src/libcore/os.rs

@@ -818,6 +818,36 @@ pub fn change_dir(p: &Path) -> bool {
     }
 }
 
+/// Changes the current working directory to the specified
+/// path while acquiring a global lock, then calls `action`.
+/// If the change is successful, releases the lock and restores the
+/// CWD to what it was before, returning true.
+/// Returns false if the directory doesn't exist or if the directory change
+/// is otherwise unsuccessful.
+pub fn change_dir_locked(p: &Path, action: &fn()) -> bool {
+    use unstable::global::global_data_clone_create;
+    use unstable::{Exclusive, exclusive};
+
+    fn key(_: Exclusive<()>) { }
+
+    let result = unsafe {
+        global_data_clone_create(key, || {
+            ~exclusive(())
+        })
+    };
+
+    do result.with_imm() |_| {
+        let old_dir = os::getcwd();
+        if change_dir(p) {
+            action();
+            change_dir(&old_dir)
+        }
+        else {
+            false
+        }
+    }
+}
+
 /// Copies a file from one location to another
 pub fn copy_file(from: &Path, to: &Path) -> bool {
     return do_copy_file(from, to);

src/libstd/tempfile.rs

@@ -42,13 +42,18 @@ mod tests {
         use core::libc::consts::os::posix88::{S_IRUSR, S_IWUSR, S_IXUSR};
         use core::os;
 
-        let root = mkdtemp(&os::tmpdir(), "temp").expect("recursive_mkdir_rel");
-        os::change_dir(&root);
-        let path = Path("frob");
-        assert!(os::mkdir_recursive(&path,  (S_IRUSR | S_IWUSR | S_IXUSR) as i32));
-        assert!(os::path_is_dir(&path));
-        assert!(os::mkdir_recursive(&path,  (S_IRUSR | S_IWUSR | S_IXUSR) as i32));
-        assert!(os::path_is_dir(&path));
+        let root = mkdtemp(&os::tmpdir(), "recursive_mkdir_rel").
+            expect("recursive_mkdir_rel");
+        assert!(do os::change_dir_locked(&root) {
+            let path = Path("frob");
+            debug!("recursive_mkdir_rel: Making: %s in cwd %s [%?]", path.to_str(),
+                   os::getcwd().to_str(),
+                   os::path_exists(&path));
+            assert!(os::mkdir_recursive(&path,  (S_IRUSR | S_IWUSR | S_IXUSR) as i32));
+            assert!(os::path_is_dir(&path));
+            assert!(os::mkdir_recursive(&path,  (S_IRUSR | S_IWUSR | S_IXUSR) as i32));
+            assert!(os::path_is_dir(&path));
+        });
     }
 
     #[test]
@@ -67,18 +72,21 @@ mod tests {
         use core::libc::consts::os::posix88::{S_IRUSR, S_IWUSR, S_IXUSR};
         use core::os;
 
-        let root = mkdtemp(&os::tmpdir(), "temp").expect("recursive_mkdir_rel_2");
-        os::change_dir(&root);
-        let path = Path("./frob/baz");
-        debug!("...Making: %s in cwd %s", path.to_str(), os::getcwd().to_str());
-        assert!(os::mkdir_recursive(&path, (S_IRUSR | S_IWUSR | S_IXUSR) as i32));
-        assert!(os::path_is_dir(&path));
-        assert!(os::path_is_dir(&path.pop()));
-        let path2 = Path("quux/blat");
-        debug!("Making: %s in cwd %s", path2.to_str(), os::getcwd().to_str());
-        assert!(os::mkdir_recursive(&path2, (S_IRUSR | S_IWUSR | S_IXUSR) as i32));
-        assert!(os::path_is_dir(&path2));
-        assert!(os::path_is_dir(&path2.pop()));
+        let root = mkdtemp(&os::tmpdir(), "recursive_mkdir_rel_2").
+            expect("recursive_mkdir_rel_2");
+        assert!(do os::change_dir_locked(&root) {
+            let path = Path("./frob/baz");
+            debug!("recursive_mkdir_rel_2: Making: %s in cwd %s [%?]", path.to_str(),
+                   os::getcwd().to_str(), os::path_exists(&path));
+            assert!(os::mkdir_recursive(&path, (S_IRUSR | S_IWUSR | S_IXUSR) as i32));
+                assert!(os::path_is_dir(&path));
+            assert!(os::path_is_dir(&path.pop()));
+            let path2 = Path("quux/blat");
+            debug!("recursive_mkdir_rel_2: Making: %s in cwd %s", path2.to_str(),
+                   os::getcwd().to_str());
+            assert!(os::mkdir_recursive(&path2, (S_IRUSR | S_IWUSR | S_IXUSR) as i32));
+                assert!(os::path_is_dir(&path2));
+            assert!(os::path_is_dir(&path2.pop()));
+        });
     }
-
-}
+}