Allow sending messages to registered process with !

Enables sending messages to registered processes using the shorhand `!`
operator. If a message is sent to an atom name that is not registered using the
`!` operator a `badarg` run-time error occurs, matching OTP behaviour.

closes atomvm#1011
closes atomvm#98

Signed-off-by: Winford <winford@object.stream>

CHANGELOG.md

@@ -9,6 +9,7 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 ### Fixed
 
 - ESP32: fix i2c_driver_acquire and i2c_driver_release functions, that were working only once.
+- Sending messages to registered processes using the `!` operator now works.
 
 ## [0.6.0-beta.0] - 2024-02-08
 

src/libAtomVM/opcodesswitch.h

@@ -2213,7 +2213,18 @@ HOT_FUNC int scheduler_entry_point(GlobalContext *glb)
                 #endif
 
                 #ifdef IMPL_EXECUTE_LOOP
-                    int local_process_id = term_to_local_process_id(x_regs[0]);
+                    term recipient_term = x_regs[0];
+                    int local_process_id;
+                    if (term_is_pid(recipient_term)) {
+                        local_process_id = term_to_local_process_id(recipient_term);
+                    } else if (term_is_atom(recipient_term)) {
+                        local_process_id = globalcontext_get_registered_process(ctx->global, term_to_atom_index(recipient_term));
+                        if (UNLIKELY(local_process_id == 0 )) {
+                            RAISE_ERROR(BADARG_ATOM);
+                        }
+                    } else {
+                        RAISE_ERROR(BADARG_ATOM);
+                    }
                     TRACE("send/0 target_pid=%i\n", local_process_id);
                     TRACE_SEND(ctx, x_regs[0], x_regs[1]);
                     globalcontext_send_message(ctx->global, local_process_id, x_regs[1]);

tests/erlang_tests/send_receive.erl

@@ -23,10 +23,44 @@
 -export([start/0, send_test/2]).
 
 start() ->
+    Test0 = test_send2(),
+    Test1 = test_send(),
+    Test2 = test_send_to_int(),
+    Test3 = test_send_to_atom(),
+    Test0 + Test1 + Test2 + Test3.
+
+send_test(V, P) ->
+    P ! V.
+
+%priv
+
+%% test send to pid
+test_send2() ->
     send_test(9, self()),
     receive
-        Value -> Value * 2
+        Value -> Value
     end.
 
-send_test(V, P) ->
-    P ! V.
+%% test send to registered process
+test_send() ->
+    erlang:register(tester, self()),
+    send_test(6, tester),
+    receive
+        RegisteredVal -> RegisteredVal
+    end.
+
+%% test send to integer
+test_send_to_int() ->
+    try 1 ! 1 of
+        _Any -> 0
+    catch
+        error:badarg -> 2
+    end.
+
+%% test send to non-registered atom
+test_send_to_atom() ->
+    try test ! nobody of
+        _Any -> 0
+    catch
+        error:badarg -> 1
+    end.