xo-gc: + CollectorTypeRegistry for streamlined init

cmake/xo_expression2Config.cmake.in

@@ -11,6 +11,7 @@ find_dependency(reflect)
 find_dependency(xo_object2)
 find_dependency(xo_printable2)
 find_dependency(xo_flatstring)
+find_dependency(cmake)
 find_dependency(indentlog)
 
 include("${CMAKE_CURRENT_LIST_DIR}/@PROJECT_NAME@Targets.cmake")

include/xo/expression2/init_expression2.hpp

@@ -0,0 +1,21 @@
+/** @file init_expression2.hpp
+*
+ *  @author Roland Conybeare, Jan 2026
+ **/
+
+#pragma once
+
+#include <xo/subsys/Subsystem.hpp>
+
+namespace xo {
+    /* tag to represent the xo-expression2/ subsystem within ordered initialization */
+    enum S_expression2_tag {};
+
+    template <>
+    struct InitSubsys<S_expression2_tag> {
+        static void init();
+        static InitEvidence require();
+    };
+} /*namespace xo*/
+
+/* end init_expression2.hpp */

src/expression2/CMakeLists.txt

@@ -2,13 +2,16 @@
 
 set(SELF_LIB xo_expression2)
 set(SELF_SRCS
+    init_expression2.cpp
     DConstant.cpp
     TypeRef.cpp
     IExpression_Any.cpp
     IExpression_DConstant.cpp
     StringTable.cpp
     DUniqueString.cpp
+    IGCObject_DUniqueString.cpp
     expression2_register_facets.cpp
+    expression2_register_types.cpp
     )
 
 xo_add_shared_library4(${SELF_LIB} ${PROJECT_NAME}Targets ${PROJECT_VERSION} 1 ${SELF_SRCS})
@@ -18,4 +21,5 @@ xo_dependency(${SELF_LIB} reflect)
 xo_dependency(${SELF_LIB} xo_object2)
 xo_dependency(${SELF_LIB} xo_printable2)
 xo_dependency(${SELF_LIB} xo_flatstring)
+xo_dependency(${SELF_LIB} subsys)
 xo_dependency(${SELF_LIB} indentlog)

src/expression2/init_expression2.cpp

@@ -0,0 +1,41 @@
+/** @file init_expression2.cpp
+*
+ *  @author Roland Conybeare, Jan 2026
+ **/
+
+#include "init_expression2.hpp"
+#include "expression2_register_facets.hpp"
+#include "expression2_register_types.hpp"
+
+#include <xo/object2/init_object2.hpp>
+#include <xo/gc/CollectorTypeRegistry.hpp>
+
+namespace xo {
+    using xo::scm::expression2_register_facets;
+    using xo::scm::expression2_register_types;
+    using xo::mm::CollectorTypeRegistry;
+
+    void
+    InitSubsys<S_expression2_tag>::init()
+        {
+            expression2_register_facets();
+
+            CollectorTypeRegistry::instance().register_types(&expression2_register_types);
+        }
+
+    InitEvidence
+    InitSubsys<S_expression2_tag>::require()
+        {
+            InitEvidence retval;
+
+            /* direct subsystem deps for xo-object2/ */
+            retval ^= InitSubsys<S_object2_tag>::require();
+
+            /* xo-expression2/'s own initialization code */
+            retval ^= Subsystem::provide<S_expression2_tag>("expression2", &init);
+
+            return retval;
+        }
+} /*namespace xo*/
+
+/* end init_expression2.cpp */

utest/expression2_utest_main.cpp

@@ -1,6 +1,24 @@
 /* file expression2_utest_main.cpp */
 
-#define CATCH_CONFIG_MAIN
+#include <xo/subsys/Subsystem.hpp>
+
+#define CATCH_CONFIG_RUNNER
 #include "catch2/catch.hpp"
 
+int
+main(int argc, char* argv[])
+{
+    using xo::Subsystem;
+
+    // Your custom initialization code here
+    Subsystem::initialize_all();
+
+    // Run Catch2's test session
+    int result = Catch::Session().run(argc, argv);
+
+    // cleanup here, if any
+
+    return result;
+}
+
 /* end expression2_utest_main.cpp */