SC: SYNC_CALL protocol feature definition and registration

libraries/chain/include/eosio/chain/protocol_feature_manager.hpp

@@ -39,6 +39,7 @@ enum class builtin_protocol_feature_t : uint32_t {
    disable_deferred_trxs_stage_1 = 22,
    disable_deferred_trxs_stage_2 = 23,
    savanna = 24,
+   sync_call = 25,
    reserved_private_fork_protocol_features = 500000,
 };
 

libraries/chain/protocol_feature_manager.cpp

@@ -363,6 +363,17 @@ host function call will trigger a transition to the Savanna consensus algorithm.
               builtin_protocol_feature_t::disable_deferred_trxs_stage_2
             }
          } )
+         (  builtin_protocol_feature_t::sync_call, builtin_protocol_feature_spec{
+            "SYNC_CALL",
+            fc::variant("49f6fbc4fee045bc5c8b09a96b2b5c096afdc320ac29b54e0f3805c660b88483").as<digest_type>(),
+            // SHA256 hash of the raw message below within the comment delimiters (exclude newline after /*) (do not modify message below).
+/*
+Builtin protocol feature: SYNC_CALL
+
+Enables synchronous calls to functions in other and own contracts.
+*/
+            {builtin_protocol_feature_t::savanna}
+         } )
    ;
 
 

unittests/protocol_feature_tests.cpp

@@ -2316,4 +2316,30 @@ BOOST_AUTO_TEST_CASE_TEMPLATE(set_finalizers_test, T, testers) { try {
                        c.error("alice does not have permission to call this API"));
 } FC_LOG_AND_RETHROW() }
 
+BOOST_AUTO_TEST_CASE(sync_call_activation_test) try {
+   tester c( setup_policy::preactivate_feature_and_new_bios );
+   const auto& pfm = c.control->get_protocol_feature_manager();
+
+   // Ensure SYNC_CALL not yet activated
+   BOOST_CHECK( !c.control->is_builtin_activated( builtin_protocol_feature_t::sync_call ) );
+
+   // Activate SYNC_CALL without the dependency met (it depends on SAVANNA).
+   auto d = pfm.get_builtin_digest( builtin_protocol_feature_t::sync_call );
+   BOOST_REQUIRE( d );
+   BOOST_CHECK_EXCEPTION( c.preactivate_protocol_features({ *d }),
+                          protocol_feature_exception,
+                          fc_exception_message_starts_with("not all dependencies of protocol feature with digest") );
+
+   // Activate the depending Savanna
+   c.preactivate_savanna_protocol_features();
+   c.produce_block();
+
+   // Activate SYNC_CALL after the dependency met
+   c.preactivate_protocol_features({ *d });
+   c.produce_block();
+
+   // Ensure SYNC_CALL is now activated
+   BOOST_CHECK( c.control->is_builtin_activated( builtin_protocol_feature_t::sync_call ) );
+} FC_LOG_AND_RETHROW()
+
 BOOST_AUTO_TEST_SUITE_END()