Merge fs and fs_libc tests

Author: Aaron1011

tests/run-pass/fs.rs

@@ -25,6 +25,7 @@ fn main() {
     test_errors();
     test_rename();
     test_directory();
+    test_dup_stdout_stderr();
 }
 
 fn tmp() -> PathBuf {
@@ -335,3 +336,13 @@ fn test_directory() {
     // Reading the metadata of a non-existent directory should fail with a "not found" error.
     assert_eq!(ErrorKind::NotFound, check_metadata(&[], &dir_path).unwrap_err().kind());
 }
+
+fn test_dup_stdout_stderr() {
+    let bytes = b"hello dup fd\n";
+    unsafe {
+        let new_stdout = libc::fcntl(1, libc::F_DUPFD, 0);
+        let new_stderr = libc::fcntl(2, libc::F_DUPFD, 0);
+        libc::write(new_stdout, bytes.as_ptr() as *const libc::c_void, bytes.len());
+        libc::write(new_stderr, bytes.as_ptr() as *const libc::c_void, bytes.len());
+    }
+}