The main thread cannot be closed

No thread started with pcall (instead of resume) can be closed,
because coroutine.close would not respect the expected number of
results from the protected call.

1 files changed, 3 insertions, 0 deletions

diff --git a/lcorolib.c b/lcorolib.c
index 5b9736f1..23dd8441 100644
--- a/lcorolib.c
+++ b/lcorolib.c
@@ -190,6 +190,9 @@ static int luaB_close (lua_State *L) {
       }
     }
     case COS_RUN:  /* running coroutine? */
+      lua_geti(L, LUA_REGISTRYINDEX, LUA_RIDX_MAINTHREAD);  /* get main */
+      if (lua_tothread(L, -1) == co)
+        return luaL_error(L, "cannot close main thread");
       lua_closethread(co, L);  /* close itself */
       lua_assert(0);  /* previous call does not return */
       return 0;