--- a/lib/erl_interface/src/misc/ei_portio.h	2021-08-03 11:40:41.087250211 +0800
+++ b/lib/erl_interface/src/misc/ei_portio.h	2021-08-03 11:40:19.690906742 +0800
@@ -47,7 +47,7 @@
 int ei_socket_callbacks_have_writev__(ei_socket_callbacks *cbs);
 #endif

-ei_socket_callbacks ei_default_socket_callbacks;
+extern ei_socket_callbacks ei_default_socket_callbacks;

 #define EI_FD_AS_CTX__(FD)                                              \
     ((void *) (long) (FD))
