add fixme comment

Author: Mandragorian

src/shims/unix/sync.rs

@@ -74,6 +74,8 @@ fn mutex_id_offset<'tcx>(ecx: &MiriInterpCx<'tcx>) -> InterpResult<'tcx, u64> {
 
     // Sanity-check this against PTHREAD_MUTEX_INITIALIZER (but only once):
     // the id must start out as 0.
+    // FIXME on some platforms (e.g linux) there are more static initializers for
+    // recursive or error checking mutexes. We should also add thme in this sanity check.
     static SANITY: AtomicBool = AtomicBool::new(false);
     if !SANITY.swap(true, Ordering::Relaxed) {
         let static_initializer = ecx.eval_path(&["libc", "PTHREAD_MUTEX_INITIALIZER"]);