cgen: fix fn voidptr param calling with nonpointer rvalue (fix #18424) (#18462)

vlib/v/gen/c/fn.v

@@ -2204,7 +2204,7 @@ fn (mut g Gen) ref_or_deref_arg(arg ast.CallArg, expected_type ast.Type, lang as
 					if atype.has_flag(.generic) {
 						atype = g.unwrap_generic(atype)
 					}
-					if atype.has_flag(.generic) {
+					if atype.has_flag(.generic) || arg.expr is ast.StructInit {
 						g.write('(voidptr)&/*qq*/')
 					} else {
 						needs_closing = true

vlib/v/tests/fn_voidptr_param_call_with_nonpointer_rvalue_test.v

@@ -0,0 +1,23 @@
+import eventbus
+
+struct MyMessage {
+	msg string
+}
+
+fn test_fn_call_with_nonpointer_rvalue() {
+	eb := eventbus.new()
+	mut subscriber := eb.subscriber
+
+	subscriber.subscribe('my_publish', subscriber_method)
+
+	do_something(eb)
+	assert true
+}
+
+fn subscriber_method(receiver voidptr, ev &MyMessage, sender voidptr) {
+	println(ev)
+}
+
+fn do_something(eb &eventbus.EventBus) {
+	eb.publish('my_publish', eb, MyMessage{ msg: 'this is my message' })
+}