Drop files explicitly when closing them

Author: pvdrz

src/shims/fs.rs

@@ -143,7 +143,13 @@ pub trait EvalContextExt<'mir, 'tcx: 'mir>: crate::MiriEvalContextExt<'mir, 'tcx
         let fd = this.read_scalar(fd_op)?.to_i32()?;
 
         if let Some(handle) = this.machine.file_handler.handles.remove(&fd) {
-            this.try_unwrap_io_result(handle.file.sync_all().map(|_| 0i32))
+            // `File::sync_all` does the checks that are done when closing a file. We do this to
+            // to handle possible errors correctly.
+            let result = this.try_unwrap_io_result(handle.file.sync_all().map(|_| 0i32));
+            // Now we actually drop the handle.
+            drop(handle);
+            // And return the result.
+            result
         } else {
             this.handle_not_found()
         }