Fix leak in vec::IntoIter when a destructor panics

Author: jonas-schievink

src/liballoc/tests/vec.rs

@@ -765,6 +765,35 @@ fn test_into_iter_clone() {
     assert_eq!(it.next(), None);
 }
 
+#[test]
+fn test_into_iter_leak() {
+    static mut DROPS: i32 = 0;
+
+    struct D(bool);
+
+    impl Drop for D {
+        fn drop(&mut self) {
+            unsafe {
+                DROPS += 1;
+            }
+
+            if self.0 {
+                panic!("panic in `drop`");
+            }
+        }
+    }
+
+    let v = vec![
+        D(false),
+        D(true),
+        D(false),
+    ];
+
+    catch_unwind(move || drop(v.into_iter())).ok();
+
+    assert_eq!(unsafe { DROPS }, 3);
+}
+
 #[test]
 fn test_cow_from() {
     let borrowed: &[_] = &["borrowed", "(slice)"];

src/liballoc/vec.rs

@@ -2620,7 +2620,9 @@ impl<T: Clone> Clone for IntoIter<T> {
 unsafe impl<#[may_dangle] T> Drop for IntoIter<T> {
     fn drop(&mut self) {
         // destroy the remaining elements
-        for _x in self.by_ref() {}
+        unsafe {
+            ptr::drop_in_place(self.as_mut_slice());
+        }
 
         // RawVec handles deallocation
         let _ = unsafe { RawVec::from_raw_parts(self.buf.as_ptr(), self.cap) };