From 9197f6ea9af095eebbbf42e4ceca5ef762467276 Mon Sep 17 00:00:00 2001
From: Sverker Eriksson <sverker@erlang.org>
Date: Wed, 20 Feb 2019 16:04:58 +0100
Subject: erts: Add enif_set_pid_undefined & enif_is_pid_undefined

---
 erts/emulator/beam/erl_nif.c | 14 ++++++++++++++
 1 file changed, 14 insertions(+)

(limited to 'erts/emulator/beam/erl_nif.c')

diff --git a/erts/emulator/beam/erl_nif.c b/erts/emulator/beam/erl_nif.c
index 82645d4091..0efef37802 100644
--- a/erts/emulator/beam/erl_nif.c
+++ b/erts/emulator/beam/erl_nif.c
@@ -1083,6 +1083,17 @@ int enif_get_local_pid(ErlNifEnv* env, ERL_NIF_TERM term, ErlNifPid* pid)
     return 0;
 }
 
+void enif_set_pid_undefined(ErlNifPid* pid)
+{
+    pid->pid = am_undefined;
+}
+
+int enif_is_pid_undefined(const ErlNifPid* pid)
+{
+    ASSERT(pid->pid == am_undefined || is_internal_pid(pid->pid));
+    return pid->pid == am_undefined;
+}
+
 int enif_get_local_port(ErlNifEnv* env, ERL_NIF_TERM term, ErlNifPort* port)
 {
     if (is_internal_port(term)) {
@@ -3336,6 +3347,9 @@ int enif_monitor_process(ErlNifEnv* env, void* obj, const ErlNifPid* target_pid,
     }
     ASSERT(rsrc->type->down);
 
+    if (target_pid->pid == am_undefined)
+        return 1;
+
     ref = erts_make_ref_in_buffer(tmp);
 
     mdp = erts_monitor_create(ERTS_MON_TYPE_RESOURCE, ref,
-- 
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