xo-alloc2: register DArena facet + subsystem init

include/xo/alloc2/alloc2_register_facets.hpp

@@ -0,0 +1,15 @@
+/** @file alloc2_register_facets.hpp
+ *
+ *  @author Roland Conybeare, Feb 2026
+ **/
+
+#pragma once
+
+namespace xo {
+    namespace mm {
+        /** Register alloc2 (facet,impl) combinations with Facet Registry **/
+        bool alloc2_register_facets();
+    }
+}
+
+/* end alloc2_register_facets.hpp */

include/xo/alloc2/init_alloc2.hpp

@@ -0,0 +1,23 @@
+/** @file init_alloc2.hpp
+ *
+ *  @author Roland Conybeare, Feb 2026
+ **/
+
+#pragma once
+
+#include <xo/subsys/Subsystem.hpp>
+
+namespace xo {
+    /* tag to represent the xo-alloc2/ subsystem within ordered initialization */
+    enum S_alloc2_tag {};
+
+    template <>
+    struct InitSubsys<S_alloc2_tag> {
+        static void init();
+        static InitEvidence require();
+    };
+
+
+} /*namespace xo*/
+
+/* end init_alloc2.hpp */

src/alloc2/CMakeLists.txt

@@ -3,26 +3,22 @@
 set(SELF_LIB xo_alloc2)
 set(SELF_SRCS
 
-#    AllocError.cpp
-#    AllocInfo.cpp
-#    cmpresult.cpp
+    init_alloc2.cpp
+    alloc2_register_facets.cpp
 
     AAllocator.cpp
-#    ArenaConfig.cpp
-#    DArena.cpp
     IAllocator_Any.cpp
     IAllocator_DArena.cpp
 
     IAllocIterator_Any.cpp
-#    DArenaIterator.cpp
     IAllocIterator_DArenaIterator.cpp
 
     IResourceVisitor_Any.cpp
-
     )
 
 xo_add_shared_library4(${SELF_LIB} ${PROJECT_NAME}Targets ${PROJECT_VERSION} 1 ${SELF_SRCS})
 # note: deps here must also appear in cmake/xo_alloc2Config.cmake.in
 xo_dependency(${SELF_LIB} xo_arena)
 xo_dependency(${SELF_LIB} xo_facet)
+xo_dependency(${SELF_LIB} subsys)
 xo_dependency(${SELF_LIB} indentlog)

src/alloc2/alloc2_register_facets.cpp

@@ -0,0 +1,33 @@
+/** @file alloc2_register_facets.cpp
+ *
+ * @author Roland Conybeare, Feb 2026
+ **/
+
+#include "alloc2_register_facets.hpp"
+#include <xo/alloc2/Arena.hpp>
+#include <xo/facet/FacetRegistry.hpp>
+#include <xo/indentlog/scope.hpp>
+
+namespace xo {
+    using xo::facet::FacetRegistry;
+    //using xo::facet::TypeRegistry;
+    using xo::reflect::typeseq;
+
+    namespace mm {
+
+        bool
+        alloc2_register_facets()
+        {
+            scope log(XO_DEBUG(true));
+
+            FacetRegistry::register_impl<AAllocator, DArena>();
+
+            log && log(xtag("DArena.tseq", typeseq::id<DArena>()));
+
+            return true;
+        }
+
+    } /*namespace scm*/
+} /*namespace xo*/
+
+/* end alloc2_register_facets.cpp */

src/alloc2/init_alloc2.cpp

@@ -0,0 +1,36 @@
+/** @file init_alloc2.cpp
+ *
+ *  @author Roland Conybeare, Feb 2026
+ **/
+
+#include "init_alloc2.hpp"
+#include "alloc2_register_facets.hpp"
+
+namespace xo {
+    using xo::mm::alloc2_register_facets;
+    // using xo::mm::alloc2_register_types;
+    // using xo::mm::CollectorTypeRegistry;
+
+    void
+    InitSubsys<S_alloc2_tag>::init()
+    {
+        alloc2_register_facets();
+    }
+
+    InitEvidence
+    InitSubsys<S_alloc2_tag>::require()
+    {
+        InitEvidence retval;
+
+        /* direct subsystem deps for xo-alloc2/ (if/when) */
+        //retval ^= InitSubsys<S_foo_tag>>::require();
+
+        /* xo-alloc2/'s own initialization code */
+        retval ^= Subsystem::provide<S_alloc2_tag>("alloc2", &init);
+
+        return retval;
+    }
+
+} /*namespace xo*/
+
+/* end init_alloc2.cpp */