error[E0133]: call to unsafe function `before_exec` is unsafe and requires unsafe block
  --> $DIR/unsafe-before_exec.rs:14:5
   |
LL |     cmd.before_exec(|| Ok(()));
   |     ^^^^^^^^^^^^^^^^^^^^^^^^^^ call to unsafe function
   |
   = note: consult the function's documentation for information on how to avoid undefined behavior

error: aborting due to 1 previous error

For more information about this error, try `rustc --explain E0133`.