xo-gc: + CollectorTypeRegistry for streamlined init

xo-expression2/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")

xo-expression2/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 */

xo-expression2/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)

xo-expression2/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 */

xo-expression2/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 */

xo-gc/include/xo/gc/CollectorTypeRegistry.hpp

@@ -0,0 +1,74 @@
+/** @file CollectorTypeRegistry.hpp
+ *
+ *  @brief Runtime type registration for gc-aware types
+ *
+ *  @author Roland Conybeare, Jan 2026
+ **/
+
+#pragma once
+
+#include "Collector.hpp"
+#include <functional>
+
+namespace xo {
+    namespace mm {
+        /** @class CollectorTypeRegistry
+         *
+         *  @brief Runtime registry for gc-aware types
+         *
+         *  Singleton to remember known gc-aware types;
+         *  use to simplify registering such types
+         *  with a collector instance.
+         *
+         *  Remark: splitting work here between
+         *  1. static initializer work: tracking gc-aware types,
+         *  2. runtime post-configuration work: report
+         *     gc-aware types to GC instances
+         *
+         *  Use:
+         *  1. subsystem foo provides function foo_register_types(obj<ACollector> gc)
+         *     Function calls
+         *       gc.install_type(impl_for<AGCObject, DQuux>())
+         *     for each gc-aware type provided by subsystem foo
+         *
+         *     Example: in file xo-object2/src/object2/object2_register_types.cpp, see
+         *       object2_register_types()
+         *
+         *  2. during subsystem init, call
+         *       CollectorTypeRegistry::instance().register_types(&foo_register_types);
+         *
+         *     Example: in file xo-object2/src/object2/init_object2.cpp, see
+         *       InitSubsys<S_object2_tag>::init()
+         *
+         *  3. during Collector setup, call
+         *       obj<ACollector> gc = ...;
+         *       CollectorTypeRegistry::instance().install_types(gc);
+         *
+         *    Example: in file xo-object2/utest/X1Collector.test.cpp
+         *       TEST_CASE("x1")
+         **/
+        class CollectorTypeRegistry {
+        public:
+            using init_function_type = std::function<bool (obj<ACollector>)>;
+
+        public:
+            /** singleton instance **/
+            static CollectorTypeRegistry & instance();
+
+            /** remember a gc-aware type-registration function **/
+            void register_types(init_function_type init_fn);
+
+            /** register known GC-aware types with @p gc.
+             *  Calls @c gc.isntall_type() for each
+             *  such type.
+             **/
+            bool install_types(obj<ACollector> gc);
+
+        private:
+            /** initialization steps for a new Collector instance **/
+            std::vector<init_function_type> init_seq_v_;
+        };
+    }
+}
+
+/* end CollectorTypeRegistry.hpp */

xo-gc/src/gc/CMakeLists.txt

@@ -3,8 +3,11 @@
 set(SELF_LIB xo_gc)
 set(SELF_SRCS
 
+    CollectorTypeRegistry.cpp
+
     ICollector_Any.cpp
     IGCObject_Any.cpp
+
     IAllocator_DX1Collector.cpp
     ICollector_DX1Collector.cpp
     IAllocIterator_DX1CollectorIterator.cpp

xo-gc/src/gc/CollectorTypeRegistry.cpp

@@ -0,0 +1,45 @@
+/** @file CollectorTypeRegistry.cpp
+ **/
+
+#include "CollectorTypeRegistry.hpp"
+#include <xo/indentlog/scope.hpp>
+
+namespace xo {
+    namespace mm {
+        CollectorTypeRegistry &
+        CollectorTypeRegistry::instance() {
+            static CollectorTypeRegistry s_instance;
+
+            return s_instance;
+        }
+
+        void
+        CollectorTypeRegistry::register_types(init_function_type fn) {
+            scope log(XO_DEBUG(true));
+
+            init_seq_v_.push_back(fn);
+        }
+
+        bool
+        CollectorTypeRegistry::install_types(obj<ACollector> gc) {
+            scope log(XO_DEBUG(true));
+
+            bool ok = true;
+
+            size_t i = 0;
+            size_t n = init_seq_v_.size();
+            log && log("run n init steps", xtag("n", n));
+
+            for (const auto & fn : init_seq_v_) {
+                log && log("do install fn (", i+1, "/", n, ")");
+
+                ok = ok & fn(gc);
+            }
+
+            return ok;
+        }
+
+    } /*namespace mm*/
+} /*namespace xo*/
+
+/* end CollectorTypeRegistry.cpp */

xo-object2/cmake/xo_object2Config.cmake.in

@@ -3,6 +3,7 @@
 include(CMakeFindDependencyMacro)
 find_dependency(xo_gc)
 find_dependency(xo_printable2)
+find_dependency(subsys)
 find_dependency(indentlog)
 include("${CMAKE_CURRENT_LIST_DIR}/@PROJECT_NAME@Targets.cmake")
 check_required_components("@PROJECT_NAME@")

xo-object2/include/xo/object2/init_object2.hpp

@@ -0,0 +1,21 @@
+/** @file init_object2.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_object2_tag {};
+
+    template <>
+    struct InitSubsys<S_object2_tag> {
+        static void init();
+        static InitEvidence require();
+    };
+} /*namespace xo*/
+
+/* end init_object2.hpp */

xo-object2/src/object2/CMakeLists.txt

@@ -19,6 +19,7 @@ set(SELF_SRCS
     DFloat.cpp
     DInteger.cpp
     DString.cpp
+    init_object2.cpp
     object2_register_types.cpp
     object2_register_facets.cpp
     )
@@ -27,4 +28,5 @@ xo_add_shared_library4(${SELF_LIB} ${PROJECT_NAME}Targets ${PROJECT_VERSION} 1 $
 # note: deps here must also appear in cmake/xo_object2Config.cmake.in
 xo_dependency(${SELF_LIB} xo_gc)
 xo_dependency(${SELF_LIB} xo_printable2)
+xo_dependency(${SELF_LIB} subsys)
 xo_dependency(${SELF_LIB} indentlog)

xo-object2/src/object2/init_object2.cpp

@@ -0,0 +1,39 @@
+/** @file init_object2.cpp
+*
+ *  @author Roland Conybeare, Jan 2026
+ **/
+
+#include "init_object2.hpp"
+#include "object2_register_facets.hpp"
+#include "object2_register_types.hpp"
+#include <xo/gc/CollectorTypeRegistry.hpp>
+
+namespace xo {
+    using xo::scm::object2_register_facets;
+    using xo::scm::object2_register_types;
+    using xo::mm::CollectorTypeRegistry;
+
+    void
+    InitSubsys<S_object2_tag>::init()
+        {
+            object2_register_facets();
+
+            CollectorTypeRegistry::instance().register_types(&object2_register_types);
+        }
+
+    InitEvidence
+    InitSubsys<S_object2_tag>::require()
+        {
+            InitEvidence retval;
+
+            /* direct subsystem deps for xo-object2/ */
+            // retval ^= InitSubsys<S_somedep_tag>::require();
+
+            /* xo-expression2/'s own initialization code */
+            retval ^= Subsystem::provide<S_object2_tag>("object2", &init);
+
+            return retval;
+        }
+} /*namespace xo*/
+
+/* end init_object2.cpp */

xo-object2/utest/DString.test.cpp

@@ -3,7 +3,8 @@
  *  @author Roland Conybeare, Jan 2026
  **/
 
-#include <xo/object2/StringOps.hpp>
+#include "init_object2.hpp"
+#include "StringOps.hpp"
 #include <xo/alloc2/arena/IAllocator_DArena.hpp>
 #include <catch2/catch.hpp>
 #include <cctype>
@@ -19,6 +20,14 @@ namespace xo {
     using xo::facet::obj;
 
     namespace ut {
+        static InitEvidence s_init = (InitSubsys<S_object2_tag>::require());
+
+        TEST_CASE("DString-init", "[object2][DString]")
+        {
+            // real purpose: ensure s_init survives static linking
+            REQUIRE(s_init.evidence());
+        }
+
         TEST_CASE("DString-empty", "[object2][DString]")
         {
             ArenaConfig cfg { .name_ = "testarena",

xo-object2/utest/X1Collector.test.cpp

@@ -3,6 +3,7 @@
  *  @author Roland Conybeare, Dec 2025
  **/
 
+#include "init_object2.hpp"
 #include "ListOps.hpp"
 #include "DFloat.hpp"
 #include "DInteger.hpp"
@@ -14,6 +15,7 @@
 #include "number/IGCObject_DInteger.hpp"
 #include "list/IGCObject_DList.hpp"
 
+#include <xo/gc/CollectorTypeRegistry.hpp>
 #include <xo/gc/Collector.hpp>
 #include <xo/gc/DX1Collector.hpp>
 
@@ -23,18 +25,22 @@
 #include <xo/arena/AllocInfo.hpp>
 #include <xo/arena/padding.hpp>
 
+#include <xo/subsys/Subsystem.hpp>
+
 #include <xo/indentlog/scope.hpp>
 #include <xo/indentlog/print/tag.hpp>
 
 #include <catch2/catch.hpp>
 
 namespace ut {
+    using xo::S_object2_tag;
     using xo::scm::object2_register_types;
     using xo::scm::ListOps;
     using xo::scm::DList;
     using xo::scm::DArray;
     using xo::scm::DFloat;
     using xo::scm::DInteger;
+    using xo::mm::CollectorTypeRegistry;
     using xo::mm::AAllocator;
     using xo::mm::ACollector;
     using xo::mm::AllocHeader;
@@ -49,6 +55,9 @@ namespace ut {
     using xo::mm::padding;
     using xo::facet::with_facet;
     using xo::facet::typeseq;
+    using xo::Subsystem;
+    using xo::InitEvidence;
+    using xo::InitSubsys;
     using xo::scope;
     using xo::xtag;
 
@@ -79,8 +88,13 @@ namespace ut {
         };
     }
 
+    static InitEvidence s_init = (InitSubsys<S_object2_tag>::require());
+
     TEST_CASE("x1", "[gc][x1]")
     {
+        // real purpose: ensure s_init survives static linking
+        REQUIRE(s_init.evidence());
+
         /**
          *  This is a basic Collector test for xo-object2 data types
          **/
@@ -89,6 +103,8 @@ namespace ut {
         scope log(XO_DEBUG(c_debug_flag));
 
         for (std::size_t i_tc = 0, n_tc = s_testcase_v.size(); i_tc < n_tc; ++i_tc) {
+            scope log(XO_DEBUG(true), xtag("i_tc", i_tc));
+
             try {
                 const testcase_x1 & tc = s_testcase_v[i_tc];
 
@@ -169,7 +185,7 @@ namespace ut {
                 auto c_o = with_facet<ACollector>::mkobj(&gc);
 
                 /* register object types */
-                bool ok = object2_register_types(c_o);
+                bool ok = CollectorTypeRegistry::instance().install_types(c_o);
 
                 REQUIRE(ok);
 

xo-object2/utest/object2_utest_main.cpp

@@ -1,6 +1,24 @@
 /* file object2_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 object2_utest_main.cpp */

xo-subsys/include/xo/subsys/Subsystem.hpp

@@ -130,8 +130,8 @@ namespace xo {
     public:
         SubsystemImpl() = default;
         SubsystemImpl(bool require_flag,
-                  std::string_view subsys_name,
+                      std::string_view subsys_name,
-                  std::function<void ()> init_fn)
+                      std::function<void ()> init_fn)
             : require_flag_{require_flag},
               subsys_name_{subsys_name},
               init_fn_{init_fn} {}