print the error message before abort()

src/error.c

@@ -209,6 +209,9 @@ mrb_exc_raise(mrb_state *mrb, mrb_value exc)
   mrb->exc = (struct RObject*)mrb_object(exc);
   exc_debug_info(mrb, mrb->exc);
   if (!mrb->jmp) {
+#ifdef ENABLE_STDIO
+    mrb_p(mrb, exc);
+#endif
     abort();
   }
   longjmp(*(jmp_buf*)mrb->jmp, 1);