Don't implement Clone on Dir, SignalFd, and PtyMaster

Since they close their file descriptors on Drop, it's almost impossible
to use Clone without creating a double-close situation.

Also, check for EBADF in SignalFd::drop and Dir::drop.

1 files changed, 5 insertions, 2 deletions

diff --git a/src/dir.rs b/src/dir.rs
index 1d48f18c..1898950f 100644
--- a/src/dir.rs
+++ b/src/dir.rs
@@ -25,7 +25,7 @@ use libc::{dirent, readdir_r};
 ///    * returns entries for `.` (current directory) and `..` (parent directory).
 ///    * returns entries' names as a `CStr` (no allocation or conversion beyond whatever libc
 ///      does).
-#[derive(Clone, Debug, Eq, Hash, PartialEq)]
+#[derive(Debug, Eq, Hash, PartialEq)]
 pub struct Dir(
     ptr::NonNull<libc::DIR>
 );
@@ -85,7 +85,10 @@ impl AsRawFd for Dir {
 
 impl Drop for Dir {
     fn drop(&mut self) {
-        unsafe { libc::closedir(self.0.as_ptr()) };
+        let e = Errno::result(unsafe { libc::closedir(self.0.as_ptr()) });
+        if !std::thread::panicking() && e == Err(Error::Sys(Errno::EBADF)) {
+            panic!("Closing an invalid file descriptor!");
+        };
     }
 }