xo-gc: refactor: demote GCObjectVisitor to GCObjectStore

No longer needed by DX1Collector
Also retires utest/MockCollector

xo-gc/CMakeLists.txt

@@ -27,9 +27,9 @@ xo_add_genfacetimpl(
 
 # note: manual target; generated code committed to git
 xo_add_genfacetimpl(
-    TARGET xo-gc-facetimpl-gcobjectvisitor-x1collector
+    TARGET xo-gc-facetimpl-gcobjectvisitor-gcobjectstorevisitor
     FACET_PKG xo_alloc2
-    INPUT idl/IGCObjectVisitor_DX1Collector.json5
+    INPUT idl/IGCObjectVisitor_DGCObjectStoreVisitor.json5
 )
 
 # ----------------------------------------------------------------

xo-gc/idl/IGCObjectVisitor_DGCObjectStoreVisitor.json5

@@ -0,0 +1,28 @@
+{
+    mode: "implementation",
+    output_cpp_dir: "src/gc/facet",
+    output_hpp_dir: "include/xo/gc",
+    output_impl_subdir: "detail",
+    includes: [
+//        "<xo/alloc2/GCObject.hpp>",
+//        "<xo/alloc2/Allocator.hpp>"
+    ],
+    local_types: [
+//        {
+//            name: "typeseq",
+//            doc: ["identifies a c++ type"],
+//            definition: "xo::reflect::typeseq"
+//        },
+    ],
+    namespace1: "xo",
+    namespace2: "mm",
+    facet_idl: "idl/GCObjectVisitor.json5",
+    brief: "provide AGCObjectVisitor interface for DGCObjectStoreVisitor",
+    using_doxygen: true,
+    repr: "DGCObjectStoreVisitor",
+    doc: [
+        "Implement AGCObjectVisitor for DGCObjectStoreVisitor.",
+        "Visit a gc-aware object. Either evacuate+forward (for gc cycle),",
+        "or check consistency (for verify_ok)",
+    ],
+}

xo-gc/include/xo/gc/DGCObjectStoreVisitor.hpp

@@ -0,0 +1,49 @@
+/** @file DGCObjectStoreVisitor.hpp
+ *
+ *  @author Roland Conybeare, Apr 2026
+ **/
+
+#pragma once
+
+#include <xo/alloc2/GCObjectVisitor.hpp>
+#include <xo/alloc2/VisitReason.hpp>
+#include <xo/alloc2/Generation.hpp>
+#include <xo/alloc2/role.hpp>
+#include <xo/arena/AllocInfo.hpp>
+#include <xo/facet/obj.hpp>
+
+namespace xo {
+    namespace mm {
+
+        class GCObjectStore; // see GCObjectStore.hpp
+        class AGCObject; // see AGCObject.hpp
+
+        /** @brief visitor shim for GCObjectStore
+         *
+         *  For a GC cycle, remembers which generations
+         *  are being collected
+         **/
+        class DGCObjectStoreVisitor {
+        public:
+            DGCObjectStoreVisitor(GCObjectStore * gcos, Generation upto);
+            
+            template <typename AFacet = AGCObjectVisitor>
+            obj<AFacet,DGCObjectStoreVisitor> ref() { return obj<AFacet,DGCObjectStoreVisitor>(this); }
+
+            Generation generation_of(Role r, const void * addr) const noexcept;
+            AllocInfo alloc_info(void * mem) const noexcept;
+
+            void visit_child(VisitReason reason, AGCObject * lhs_iface, void ** lhs_data);
+            std::byte * alloc_copy(void * src) noexcept;
+
+        private:
+            /** object storage **/
+            GCObjectStore * p_gco_store_ = nullptr;
+            /** collecting generations up to this bound **/
+            Generation upto_;
+        };
+
+    } /*namespace mm*/
+} /*namespace xo*/
+
+/* end DGCObjectVisitor.hpp */

xo-gc/include/xo/gc/GCObjectStore.hpp

@@ -134,7 +134,7 @@ namespace xo {
              *  to call AGCObject visitor method (forward_children()) on each
              *  object stored here.
              **/
-            void verify_ok(obj<AGCObjectVisitor> gc) noexcept;
+            void verify_ok() noexcept;
 
             /** Register object type with this collector.
              *  Provides shallow copy and pointer forwarding for instances of this
@@ -156,8 +156,7 @@ namespace xo {
              *
              *  Require: runstate_.is_running()
              **/
-            void * deep_move_root(obj<AGCObjectVisitor> gc,
+            void * deep_move_root(const AGCObject * root_iface,
-                                  const AGCObject * root_iface,
                                   void ** root_data,
                                   Generation upto);
 
@@ -170,15 +169,16 @@ namespace xo {
                                       void * from_src,
                                       Generation upto);
 
-#ifdef NOT_YET
             /** Target for GCObjectVisitor facet
              *  During gc phase (@p reason is 'forward')
              *  1. evacuate object at @p *lhs_data to to-space.
              *  2. replace @p *lhs_data with forwarding pointer
              *     to new location.
              **/
-            void visit_child(VisitReason reason, AGCObject * lhs_iface, void ** lhs_data);
+            void visit_child_aux(VisitReason reason,
-#endif
+                                 AGCObject * lhs_iface,
+                                 void ** lhs_data,
+                                 Generation upto);
 
             /** Evacuate object at @p *lhs_data to to-space, during collection phase
              *  acting on generations g in [0 ,.., upto).

xo-gc/include/xo/gc/GCObjectStoreVisitor.hpp

@@ -0,0 +1,11 @@
+/** @file GCObjectStoreVisitor.hpp
+*
+ *  @author Roland Conybeare, Apr 2026
+ **/
+
+#pragma once
+
+#include "DGCObjectStoreVisitor.hpp"
+#include "detail/IGCObjectVisitor_DGCObjectStoreVisitor.hpp"
+
+/* end GCObjectStoreVisitor.hpp */

xo-gc/include/xo/gc/X1Collector.hpp

@@ -8,6 +8,5 @@
 #include "DX1Collector.hpp"
 #include "detail/ICollector_DX1Collector.hpp"
 #include "detail/IAllocator_DX1Collector.hpp"
-#include "detail/IGCObjectVisitor_DX1Collector.hpp"
 
 /* end X1Collector.hpp */

xo-gc/include/xo/gc/detail/IGCObjectVisitor_DGCObjectStoreVisitor.hpp

@@ -1,64 +1,64 @@
-/** @file IGCObjectVisitor_DX1Collector.hpp
+/** @file IGCObjectVisitor_DGCObjectStoreVisitor.hpp
  *
  *  Generated automagically from ingredients:
  *  1. code generator:
  *       [xo-facet/codegen/genfacet]
  *     arguments:
- *       --input [idl/IGCObjectVisitor_DX1Collector.json5]
+ *       --input [idl/IGCObjectVisitor_DGCObjectStoreVisitor.json5]
  *  2. jinja2 template for abstract facet .hpp file:
  *       [iface_facet_repr.hpp.j2]
  *  3. idl for facet methods
- *       [idl/IGCObjectVisitor_DX1Collector.json5]
+ *       [idl/IGCObjectVisitor_DGCObjectStoreVisitor.json5]
  **/
 
 #pragma once
 
 #include "GCObjectVisitor.hpp"
-#include "DX1Collector.hpp"
+#include "DGCObjectStoreVisitor.hpp"
 
-namespace xo { namespace mm { class IGCObjectVisitor_DX1Collector; } }
+namespace xo { namespace mm { class IGCObjectVisitor_DGCObjectStoreVisitor; } }
 
 namespace xo {
     namespace facet {
         template <>
         struct FacetImplementation<xo::mm::AGCObjectVisitor,
-                                   xo::mm::DX1Collector>
+                                   xo::mm::DGCObjectStoreVisitor>
         {
             using ImplType = xo::mm::IGCObjectVisitor_Xfer
-              <xo::mm::DX1Collector,
+              <xo::mm::DGCObjectStoreVisitor,
-               xo::mm::IGCObjectVisitor_DX1Collector>;
+               xo::mm::IGCObjectVisitor_DGCObjectStoreVisitor>;
         };
     }
 }
 
 namespace xo {
     namespace mm {
-        /** @class IGCObjectVisitor_DX1Collector
+        /** @class IGCObjectVisitor_DGCObjectStoreVisitor
          **/
-        class IGCObjectVisitor_DX1Collector {
+        class IGCObjectVisitor_DGCObjectStoreVisitor {
         public:
-            /** @defgroup mm-gcobjectvisitor-dx1collector-type-traits **/
+            /** @defgroup mm-gcobjectvisitor-dgcobjectstorevisitor-type-traits **/
             ///@{
             using Copaque = xo::mm::AGCObjectVisitor::Copaque;
             using Opaque = xo::mm::AGCObjectVisitor::Opaque;
             ///@}
-            /** @defgroup mm-gcobjectvisitor-dx1collector-methods **/
+            /** @defgroup mm-gcobjectvisitor-dgcobjectstorevisitor-methods **/
             ///@{
             // const methods
             /** allocation metadata for gc-aware data at address @p gco.
 @p gco must be the result of a call to collector's alloc() function **/
-            static AllocInfo alloc_info(const DX1Collector & self, void * addr);
+            static AllocInfo alloc_info(const DGCObjectStoreVisitor & self, void * addr);
             /** generation to which pointer @p addr belongs, given role @p r;
 sentinel if @p addr is not owned by collector **/
-            static Generation generation_of(const DX1Collector & self, Role r, const void * addr) noexcept;
+            static Generation generation_of(const DGCObjectStoreVisitor & self, Role r, const void * addr) noexcept;
 
             // non-const methods
             /** allocate copy of source object at address @p src.
 Source must be owned by this collector.
 Increments object age **/
-            static void * alloc_copy(DX1Collector & self, std::byte * src);
+            static void * alloc_copy(DGCObjectStoreVisitor & self, std::byte * src);
             /** visit child of a gc-aware object. May update child in-place! **/
-            static void visit_child(DX1Collector & self, VisitReason reason, AGCObject * iface, void ** pp_data) noexcept;
+            static void visit_child(DGCObjectStoreVisitor & self, VisitReason reason, AGCObject * iface, void ** pp_data) noexcept;
             ///@}
         };
 

xo-gc/src/gc/CMakeLists.txt

@@ -12,10 +12,12 @@ set(SELF_SRCS
     X1CollectorConfig.cpp
     DX1Collector.cpp
     facet/ICollector_DX1Collector.cpp
-    facet/IGCObjectVisitor_DX1Collector.cpp
 
     DX1CollectorIterator.cpp
 
+    DGCObjectStoreVisitor.cpp
+    facet/IGCObjectVisitor_DGCObjectStoreVisitor.cpp
+
     GCObjectStoreConfig.cpp
     GCObjectStore.cpp
 

xo-gc/src/gc/DGCObjectStoreVisitor.cpp

@@ -1,27 +1,34 @@
-/** @file DMockCollector.cpp
+/** @file DGCObjectStoreVisitor.cpp
  *
  *  @author Roland Conybeare, Apr 2026
  **/
 
-#include "MockCollector.hpp"
+#include "GCObjectStoreVisitor.hpp"
+#include "GCObjectStore.hpp"
 
 namespace xo {
     namespace mm {
 
+        DGCObjectStoreVisitor::DGCObjectStoreVisitor(GCObjectStore * gcos,
+                                                     Generation upto)
+        : p_gco_store_{gcos}, upto_{upto}
+        {}
+
         Generation
-        DMockCollector::generation_of(Role r, const void * addr) const noexcept
+        DGCObjectStoreVisitor::generation_of(Role r, const void * addr) const noexcept
         {
             return p_gco_store_->generation_of(r, addr);
         }
 
         AllocInfo
-        DMockCollector::alloc_info(void * mem) const noexcept
+        DGCObjectStoreVisitor::alloc_info(void * mem) const noexcept
         {
             return p_gco_store_->alloc_info((std::byte *)mem);
         }
 
         void
-        DMockCollector::visit_child(VisitReason reason, AGCObject * lhs_iface, void ** lhs_data)
+        DGCObjectStoreVisitor::visit_child(VisitReason reason,
+                                           AGCObject * lhs_iface, void ** lhs_data)
         {
             switch (reason.code()) {
             case VisitReason::code::forward:
@@ -37,11 +44,11 @@ namespace xo {
         }
 
         std::byte *
-        DMockCollector::alloc_copy(void * src) noexcept {
+        DGCObjectStoreVisitor::alloc_copy(void * src) noexcept {
             return p_gco_store_->new_space()->alloc_copy((std::byte *)src);
         }
 
     } /*namespace mm*/
 } /*namespace xo*/
 
-/* end DMockCollector.cpp */
+/* end DGCObjectVisitor.cpp */

xo-gc/src/gc/DX1Collector.cpp

@@ -4,6 +4,7 @@
  **/
 
 #include "X1Collector.hpp"
+#include "GCObjectStoreVisitor.hpp"
 #include <xo/gc/DX1CollectorIterator.hpp>
 
 #include <xo/object2/Dictionary.hpp>
@@ -13,7 +14,6 @@
 #include <xo/stringtable2/String.hpp>
 
 #include <xo/alloc2/GCObject.hpp>
-#include <xo/alloc2/GCObjectVisitor.hpp>
 #include <xo/alloc2/Allocator.hpp>
 #include <xo/alloc2/Arena.hpp>
 #include "object_age.hpp"
@@ -383,7 +383,8 @@ namespace xo {
             // Add run state so DX1Collector can recognize forward_inplace()
             // calls made for the purpose of checking child pointers.
 
-            auto self = this->ref<AGCObjectVisitor>();
+            DGCObjectStoreVisitor visitor(&gco_store_,
+                                          Generation{0} /*not used for verify*/);
 
             GCRunState saved_runstate = runstate_;
             {
@@ -404,8 +405,7 @@ namespace xo {
                         // - X1Collector::forward_inplace() -> _verify_aux()
                         //
 
-                        gco.visit_gco_children(VisitReason::verify(), self);
+                        gco.visit_gco_children(VisitReason::verify(), visitor.ref());
-
                     }
 
                     X1VerifyStats post = verify_stats_;
@@ -417,7 +417,7 @@ namespace xo {
                 }
 
                 // 3. scan to-space for each generation
-                gco_store_.verify_ok(this->ref<AGCObjectVisitor>());
+                gco_store_.verify_ok();
 
                 // 4. scan mutation logs
                 mlog_store_.verify_ok(&gco_store_,
@@ -483,7 +483,7 @@ namespace xo {
             //auto t0 = std::chrono::steady_clock::now();
 
             log && log("memory");
-            auto visitor = [&log](const MemorySizeInfo & info) {
+            auto resource_visitor = [&log](const MemorySizeInfo & info) {
                 log && log(xtag("resource", info.resource_name_),
                            xtag("used", info.used_),
                            xtag("alloc", info.allocated_),
@@ -492,7 +492,7 @@ namespace xo {
                            xtag("lo", info.lo_),
                            xtag("hi", info.hi_));
             };
-            this->visit_pools(visitor);
+            this->visit_pools(resource_visitor);
 
             if (config_.sanitize_flag_) {
                 log && log("step 0a : verify");
@@ -500,6 +500,8 @@ namespace xo {
 
             }
 
+            DGCObjectStoreVisitor gco_visitor(&gco_store_, upto);
+
             log && log("step 0b : update run state");
             this->runstate_ = GCRunState::gc_upto(upto);
 
@@ -519,7 +521,7 @@ namespace xo {
             log && log("step 2b : [STUB] copy pinned");
 
             log && log("step 3  : [STUB] forward mutation log");
-            mlog_store_.forward_mutation_log(this->ref<AGCObjectVisitor>(), upto);
+            mlog_store_.forward_mutation_log(gco_visitor.ref(), upto);
 
             log && log("step 4a : [STUB] run destructors");
             log && log("step 4b : [STUB] keep reachable weak pointers");
@@ -576,8 +578,7 @@ namespace xo {
                            xtag("slot.root()", slot.root()),
                            xtag("slot.root()->data_", slot.root()->data_));
 
-                void * root_to = gco_store_.deep_move_root(this->ref<AGCObjectVisitor>(),
+                void * root_to = gco_store_.deep_move_root(slot.root()->iface(),
-                                                           slot.root()->iface(),
                                                            (void **)&(slot.root()->data_), upto);
 
                 slot.root()->reset_opaque(root_to);
@@ -594,24 +595,9 @@ namespace xo {
             // MAYBE: adapter distinct from DX1Collector that supports GCObjectVisitor facet,
             //        calls DX1Collector::_verify_aux()
 
-            switch (reason.code()) {
+            Generation upto = runstate_.gc_upto();
-            case VisitReason::code::forward:
-            {
-                Generation upto = runstate_.gc_upto();
 
-                // called during collection phase
+            gco_store_.visit_child_aux(reason, lhs_iface, lhs_data, upto);
-                gco_store_.forward_inplace_aux
-                    (this->ref<AGCObjectVisitor>(), lhs_iface, lhs_data, upto);
-                break;
-            }
-            case VisitReason::code::verify:
-                // called during verify_ok
-                gco_store_.verify_aux(lhs_iface, *lhs_data);
-                break;
-            default:
-                // should be unreachable
-                assert(false);
-            }
         }
 
         auto

xo-gc/src/gc/GCObjectStore.cpp

@@ -4,6 +4,7 @@
  **/
 
 #include "GCObjectStore.hpp"
+#include "GCObjectStoreVisitor.hpp"
 #include "X1VerifyStats.hpp"
 
 #include <xo/object2/Dictionary.hpp>
@@ -475,35 +476,33 @@ namespace xo {
             return (g < upto);
         }
 
-#ifdef NOT_YET
         void
-        GCObjectStore::visit_child(VisitReason reason,
+        GCObjectStore::visit_child_aux(VisitReason reason,
-                                   AGCObject * lhs_iface,
+                                       AGCObject * lhs_iface,
-                                   void ** lhs_data)
+                                       void ** lhs_data,
+                                       Generation upto)
         {
-            // MAYBE: adapter distinct from DX1Collector that supports GCObjectVisitor facet,
-            //        calls DX1Collector::_verify_aux()
-
             switch (reason.code()) {
             case VisitReason::code::forward:
             {
-                Generation upto = runstate_.gc_upto();
+                DGCObjectStoreVisitor gcos_visitor(this, upto);
+                auto gcos_visitor_obj
+                    = obj<AGCObjectVisitor,DGCObjectStoreVisitor>(&gcos_visitor);
 
                 // called during collection phase
                 this->forward_inplace_aux
-                    (this->ref<AGCObjectVisitor>(), lhs_iface, lhs_data, upto);
+                    (gcos_visitor_obj, lhs_iface, lhs_data, upto);
                 break;
             }
             case VisitReason::code::verify:
                 // called during verify_ok
-                gco_store_.verify_aux(lhs_iface, *lhs_data);
+                this->verify_aux(lhs_iface, *lhs_data);
                 break;
             default:
                 // should be unreachable
                 assert(false);
             }
         }
-#endif
 
         void
         GCObjectStore::forward_inplace_aux(obj<AGCObjectVisitor> gc,
@@ -768,8 +767,11 @@ namespace xo {
         }
 
         void
-        GCObjectStore::verify_ok(obj<AGCObjectVisitor> gc) noexcept
+        GCObjectStore::verify_ok() noexcept
         {
+            Generation unused_gen; 
+            DGCObjectStoreVisitor visitor{this, unused_gen};
+
             for (Generation g(0); g < config_.n_generation_; ++g) {
                 const DArena * space = this->get_space(Role::to_space(), g);
 
@@ -789,7 +791,7 @@ namespace xo {
                             // assembled fop for gc-aware object
                             obj<AGCObject> gco(iface, const_cast<void *>(data));
 
-                            gco.visit_gco_children(VisitReason::verify(), gc);
+                            gco.visit_gco_children(VisitReason::verify(), visitor.ref());
                         } else {
                             ++(p_verify_stats_->n_no_iface_);
                             continue;
@@ -830,8 +832,7 @@ namespace xo {
         }
 
         void *
-        GCObjectStore::deep_move_root(obj<AGCObjectVisitor> gc,
+        GCObjectStore::deep_move_root(const AGCObject * root_iface,
-                                      const AGCObject * root_iface,
                                       void ** root_data,
                                       Generation upto)
         {
@@ -849,8 +850,10 @@ namespace xo {
 
             bool src_in_from_space = this->contains(Role::from_space(), *root_data);
 
+            DGCObjectStoreVisitor visitor(this, upto);
+
             if (src_in_from_space) {
-                *root_data = this->_deep_move_gc_owned(gc, *root_data, upto);
+                *root_data = this->_deep_move_gc_owned(visitor.ref(), *root_data, upto);
             } else {
                 // we aren't moving from_src, it's not gc-owned.
                 // However we are moving all its gc-owned children
@@ -860,7 +863,7 @@ namespace xo {
 
                 auto root = obj<AGCObject>(root_iface, *root_data);
 
-                root.visit_gco_children(VisitReason::forward(), gc);
+                root.visit_gco_children(VisitReason::forward(), visitor.ref());
 
                 // For each generation g:
                 //   traverse objects newer than gray_lo_v[g], to make sure children
@@ -868,7 +871,7 @@ namespace xo {
                 //   Remember that forwarding may promote objects to older generation,
                 //   so need multiple passes
                 //
-                this->_forward_children_until_fixpoint(gc, upto, gray_lo_v);
+                this->_forward_children_until_fixpoint(visitor.ref(), upto, gray_lo_v);
 
                 // reminder: *root_data preserved
 

xo-gc/src/gc/SetupGc.cpp

@@ -5,6 +5,7 @@
 
 #include "SetupGc.hpp"
 #include "X1Collector.hpp"
+#include "GCObjectStoreVisitor.hpp"
 #include <xo/facet/FacetRegistry.hpp>
 #include <xo/indentlog/scope.hpp>
 
@@ -24,9 +25,11 @@ namespace xo {
 
             FacetRegistry::register_impl<AAllocator, DX1Collector>();
             FacetRegistry::register_impl<ACollector, DX1Collector>();
-            FacetRegistry::register_impl<AGCObjectVisitor, DX1Collector>();
+
+            FacetRegistry::register_impl<AGCObjectVisitor, DGCObjectStoreVisitor>();
 
             log && log(xtag("DX1Collector.tseq", typeseq::id<DX1Collector>()));
+            log && log(xtag("DGCObjectStoreVisitor.tseq", typeseq::id<DGCObjectStoreVisitor>()));
 
             log && log(xtag("ACollector.tseq",  typeseq::id<ACollector>()));
             log && log(xtag("AGCObjectVisitor.tseq",  typeseq::id<AGCObjectVisitor>()));

xo-gc/src/gc/facet/IGCObjectVisitor_DGCObjectStoreVisitor.cpp

@@ -0,0 +1,44 @@
+/** @file IGCObjectVisitor_DGCObjectStoreVisitor.cpp
+ *
+ *  Generated automagically from ingredients:
+ *  1. code generator:
+ *       [xo-facet/codegen/genfacet]
+ *     arguments:
+ *       --input [idl/IGCObjectVisitor_DGCObjectStoreVisitor.json5]
+ *  2. jinja2 template for abstract facet .hpp file:
+ *       [iface_facet_any.hpp.j2]
+ *  3. idl for facet methods
+ *       [idl/IGCObjectVisitor_DGCObjectStoreVisitor.json5]
+**/
+
+#include "detail/IGCObjectVisitor_DGCObjectStoreVisitor.hpp"
+
+namespace xo {
+    namespace mm {
+        auto
+        IGCObjectVisitor_DGCObjectStoreVisitor::alloc_info(const DGCObjectStoreVisitor & self, void * addr) -> AllocInfo
+        {
+            return self.alloc_info(addr);
+        }
+
+        auto
+        IGCObjectVisitor_DGCObjectStoreVisitor::generation_of(const DGCObjectStoreVisitor & self, Role r, const void * addr) noexcept -> Generation
+        {
+            return self.generation_of(r, addr);
+        }
+
+        auto
+        IGCObjectVisitor_DGCObjectStoreVisitor::alloc_copy(DGCObjectStoreVisitor & self, std::byte * src) -> void *
+        {
+            return self.alloc_copy(src);
+        }
+        auto
+        IGCObjectVisitor_DGCObjectStoreVisitor::visit_child(DGCObjectStoreVisitor & self, VisitReason reason, AGCObject * iface, void ** pp_data) noexcept -> void
+        {
+            self.visit_child(reason, iface, pp_data);
+        }
+
+    } /*namespace mm*/
+} /*namespace xo*/
+
+/* end IGCObjectVisitor_DGCObjectStoreVisitor.cpp */

xo-gc/src/gc/facet/IGCObjectVisitor_DX1Collector.cpp

@@ -1,44 +0,0 @@
-/** @file IGCObjectVisitor_DX1Collector.cpp
- *
- *  Generated automagically from ingredients:
- *  1. code generator:
- *       [xo-facet/codegen/genfacet]
- *     arguments:
- *       --input [idl/IGCObjectVisitor_DX1Collector.json5]
- *  2. jinja2 template for abstract facet .hpp file:
- *       [iface_facet_any.hpp.j2]
- *  3. idl for facet methods
- *       [idl/IGCObjectVisitor_DX1Collector.json5]
-**/
-
-#include "detail/IGCObjectVisitor_DX1Collector.hpp"
-
-namespace xo {
-    namespace mm {
-        auto
-        IGCObjectVisitor_DX1Collector::alloc_info(const DX1Collector & self, void * addr) -> AllocInfo
-        {
-            return self.alloc_info(addr);
-        }
-
-        auto
-        IGCObjectVisitor_DX1Collector::generation_of(const DX1Collector & self, Role r, const void * addr) noexcept -> Generation
-        {
-            return self.generation_of(r, addr);
-        }
-
-        auto
-        IGCObjectVisitor_DX1Collector::alloc_copy(DX1Collector & self, std::byte * src) -> void *
-        {
-            return self.alloc_copy(src);
-        }
-        auto
-        IGCObjectVisitor_DX1Collector::visit_child(DX1Collector & self, VisitReason reason, AGCObject * iface, void ** pp_data) noexcept -> void
-        {
-            self.visit_child(reason, iface, pp_data);
-        }
-
-    } /*namespace mm*/
-} /*namespace xo*/
-
-/* end IGCObjectVisitor_DX1Collector.cpp */

xo-gc/utest/CMakeLists.txt

@@ -10,20 +10,10 @@ set(UTEST_SRCS
     GCObjectStore.test.cpp
     Object2.test.cpp
 
-    DMockCollector.cpp
-    IGCObjectVisitor_DMockCollector.cpp
-
     init_gc_utest.cpp
     random_allocs.cpp
 )
 
-# mock collector for unit test
-xo_add_genfacetimpl(
-    TARGET xo-gc-facetimpl-gcobjectvisitor-mockcollector
-    FACET_PKG xo_alloc2
-    INPUT idl/IGCObjectVisitor_DMockCollector.json5
-)
-
 if (ENABLE_TESTING)
     xo_add_utest_executable(${UTEST_EXE} ${UTEST_SRCS})
     xo_headeronly_dependency(${UTEST_EXE} randomgen)

xo-gc/utest/DMockCollector.hpp

@@ -1,40 +0,0 @@
-/** @file DMockCollector.hpp
- *
- *  @author Roland Conybeare, Apr 2026
- **/
-
-#pragma once
-
-#include <xo/gc/GCObjectStore.hpp>
-#include <xo/arena/AllocInfo.hpp>
-
-namespace xo {
-    namespace mm {
-
-        /** @brief Mock Collector
-         *
-         *  Intended to help unit test a GCObjectSotre instance.
-         *  Mock a Collector in collection phase for generations 0 <= g < @ref upto_.
-         **/
-        class DMockCollector {
-        public:
-            explicit DMockCollector(GCObjectStore * gcos, Generation upto) : p_gco_store_{gcos}, upto_{upto} {}
-
-            template <typename AFacet>
-            obj<AFacet,DMockCollector> ref() { return obj<AFacet,DMockCollector>(this); }
-
-            Generation generation_of(Role r, const void * addr) const noexcept;
-            AllocInfo alloc_info(void * mem) const noexcept;
-
-            void visit_child(VisitReason reason, AGCObject * lhs_iface, void ** lhs_data);
-            std::byte * alloc_copy(void * src) noexcept;
-
-        private:
-            GCObjectStore * p_gco_store_ = nullptr;
-            Generation upto_;
-        };
-
-    } /*namespace mm*/
-} /*namespaace xo*/
-
-/* end DMockCollector.hpp */

xo-gc/utest/GCObjectStore.test.cpp

@@ -5,8 +5,6 @@
 
 #include <xo/gc/GCObjectStore.hpp>
 #include <xo/gc/X1VerifyStats.hpp>
-#include "MockCollector.hpp"
-
 #include <xo/object2/ListOps.hpp>
 #include <xo/object2/List.hpp>
 #include <xo/object2/Integer.hpp>
@@ -27,7 +25,6 @@ namespace ut {
     using xo::scm::DList;
     using xo::scm::DInteger;
     using xo::scm::DBoolean;
-    using xo::mm::DMockCollector;
     using xo::mm::GCObjectStoreConfig;
     using xo::mm::GCObjectStore;
     using xo::mm::X1VerifyStats;
@@ -395,7 +392,6 @@ namespace ut {
                            const GCObjectStore & gcos)
         {
             Generation g0{0};
-            //Generation g1{1};
             Generation gn{tc.n_gen_};
 
 
@@ -413,6 +409,13 @@ namespace ut {
             }
         }
 
+        /** Generate two copies of a random object graph for test case @p tc.
+         *  Store first graph in @p *p_x1_v, allocating
+         *  entirely from @p p_gcos new-space.
+         *  Store second graph in @p *p_x2_v, allocating
+         *  entirely from @p p_arena2.
+         *  Use random number generator @p_rgen
+         **/
         void
         gcos_construct_ab_object_graphs(const Testcase & tc,
                                         GCObjectStore * p_gcos,
@@ -444,24 +447,26 @@ namespace ut {
             //                    typeseq::id<DBoolean>()));
         }
 
+        /** Invoke built-in consistency verification for @p *p_gcos.
+         **/
         void
-        gcos_verify_consistency(obj<AGCObjectVisitor> mock_gc_visitor,
+        gcos_verify_consistency(GCObjectStore * p_gcos)
-                                GCObjectStore * p_gcos,
-                                const X1VerifyStats & verify_stats)
         {
             // traverses stored objects, updates counters
             // in verify_stats (= gco.p_verify_stats_, via ctor)
             //
-            p_gcos->verify_ok(mock_gc_visitor);
+            p_gcos->verify_ok();
 
-            INFO(tostr(xtag("n_gc_root", verify_stats.n_gc_root_),
+            X1VerifyStats * verify_stats = p_gcos->verify_stats();
-                       xtag("n_ext", verify_stats.n_ext_),
-                       xtag("n_from", verify_stats.n_from_),
-                       xtag("n_to", verify_stats.n_to_),
-                       xtag("n_fwd", verify_stats.n_fwd_),
-                       xtag("n_no_iface", verify_stats.n_no_iface_)));
 
-            REQUIRE(verify_stats.is_ok());
+            INFO(tostr(xtag("n_gc_root", verify_stats->n_gc_root_),
+                       xtag("n_ext", verify_stats->n_ext_),
+                       xtag("n_from", verify_stats->n_from_),
+                       xtag("n_to", verify_stats->n_to_),
+                       xtag("n_fwd", verify_stats->n_fwd_),
+                       xtag("n_no_iface", verify_stats->n_no_iface_)));
+
+            REQUIRE(verify_stats->is_ok());
         }
 
         void
@@ -635,7 +640,7 @@ namespace ut {
         void
         gcos_move_roots_and_verify(const Testcase & tc,
                                    GCObjectStore * p_gcos,
-                                   obj<AGCObjectVisitor> mock_gc_visitor,
+                                   Generation upto,
                                    const std::vector<Recd> & x1_v,
                                    const std::vector<Recd> & x2_v,
                                    bool debug_flag)
@@ -690,9 +695,9 @@ namespace ut {
                     obj<AGCObject> x1_gco = x1.gco_;
 
                     // modifies x1.gco_ in place
-                    auto x1p_data = p_gcos->deep_move_root(mock_gc_visitor,
+                    auto x1p_data
-                                                           x1p_iface, (void **)&(x1.gco_.data_),
+                        = p_gcos->deep_move_root(x1p_iface, (void **)&(x1.gco_.data_), upto);
-                                                           g1);
+
                     REQUIRE(x1p_data);
                     REQUIRE(x1p_data == x1.gco_.data_);
 
@@ -713,8 +718,7 @@ namespace ut {
                     // but will fail since type isn't registered
 
                     auto x1p_data
-                        = p_gcos->deep_move_root(mock_gc_visitor,
+                        = p_gcos->deep_move_root(x1.gco_.iface(),
-                                                 x1.gco_.iface(),
                                                  (void **)&(x1.gco_.data_),
                                                  g1);
 
@@ -812,10 +816,6 @@ namespace ut {
             Generation g1{1};
             Generation gn{tc.n_gen_};
 
-            // scaffold mock collector doing incremental collection
-            DMockCollector mock_gc(&gcos, g1);
-            auto mock_gc_visitor = mock_gc.ref<AGCObjectVisitor>();
-
             REQUIRE(gcos.is_type_installed(typeseq::id<DList>()) == false);
             REQUIRE(gcos.is_type_installed(typeseq::id<DBoolean>()) == false);
 
@@ -836,9 +836,7 @@ namespace ut {
 
             log1 && log1("verify before any gcos side effects");
 
-            gcos_verify_consistency(mock_gc_visitor,
+            gcos_verify_consistency(&gcos);
-                                    &gcos,
-                                    verify_stats);
 
             // someday: print the graph. Need a cycle-detecting printer
 
@@ -851,7 +849,7 @@ namespace ut {
 
             gcos_verify_gen0_fromspace_only_allocated(tc, gcos, x1_v);
 
-            gcos_move_roots_and_verify(tc, &gcos, mock_gc_visitor, x1_v, x2_v, tc.debug_flag_);
+            gcos_move_roots_and_verify(tc, &gcos, g1, x1_v, x2_v, tc.debug_flag_);
 
             // Things to test:
             // - deep_move_interior()   // used from MutationLogStore
@@ -870,7 +868,7 @@ namespace ut {
                 // traverses stored objects, updates counters
                 // in verify_stats (= gco.p_verify_stats_, via ctor)
                 //
-                gcos.verify_ok(mock_gc_visitor);
+                gcos.verify_ok();
 
                 INFO(tostr(xtag("n_gc_root", verify_stats.n_gc_root_),
                            xtag("n_ext", verify_stats.n_ext_),

xo-gc/utest/IGCObjectVisitor_DMockCollector.cpp

@@ -1,44 +0,0 @@
-/** @file IGCObjectVisitor_DMockCollector.cpp
- *
- *  Generated automagically from ingredients:
- *  1. code generator:
- *       [xo-facet/codegen/genfacet]
- *     arguments:
- *       --input [idl/IGCObjectVisitor_DMockCollector.json5]
- *  2. jinja2 template for abstract facet .hpp file:
- *       [iface_facet_any.hpp.j2]
- *  3. idl for facet methods
- *       [idl/IGCObjectVisitor_DMockCollector.json5]
-**/
-
-#include "./IGCObjectVisitor_DMockCollector.hpp"
-
-namespace xo {
-    namespace mm {
-        auto
-        IGCObjectVisitor_DMockCollector::alloc_info(const DMockCollector & self, void * addr) -> AllocInfo
-        {
-            return self.alloc_info(addr);
-        }
-
-        auto
-        IGCObjectVisitor_DMockCollector::generation_of(const DMockCollector & self, Role r, const void * addr) noexcept -> Generation
-        {
-            return self.generation_of(r, addr);
-        }
-
-        auto
-        IGCObjectVisitor_DMockCollector::alloc_copy(DMockCollector & self, std::byte * src) -> void *
-        {
-            return self.alloc_copy(src);
-        }
-        auto
-        IGCObjectVisitor_DMockCollector::visit_child(DMockCollector & self, VisitReason reason, AGCObject * iface, void ** pp_data) noexcept -> void
-        {
-            self.visit_child(reason, iface, pp_data);
-        }
-
-    } /*namespace mm*/
-} /*namespace xo*/
-
-/* end IGCObjectVisitor_DMockCollector.cpp */

xo-gc/utest/IGCObjectVisitor_DMockCollector.hpp

@@ -1,68 +0,0 @@
-/** @file IGCObjectVisitor_DMockCollector.hpp
- *
- *  Generated automagically from ingredients:
- *  1. code generator:
- *       [xo-facet/codegen/genfacet]
- *     arguments:
- *       --input [idl/IGCObjectVisitor_DMockCollector.json5]
- *  2. jinja2 template for abstract facet .hpp file:
- *       [iface_facet_repr.hpp.j2]
- *  3. idl for facet methods
- *       [idl/IGCObjectVisitor_DMockCollector.json5]
- **/
-
-#pragma once
-
-#include "GCObjectVisitor.hpp"
-#include "DMockCollector.hpp"
-
-namespace xo { namespace mm { class IGCObjectVisitor_DMockCollector; } }
-
-namespace xo {
-    namespace facet {
-        template <>
-        struct FacetImplementation<xo::mm::AGCObjectVisitor,
-                                   xo::mm::DMockCollector>
-        {
-            using ImplType = xo::mm::IGCObjectVisitor_Xfer
-              <xo::mm::DMockCollector,
-               xo::mm::IGCObjectVisitor_DMockCollector>;
-        };
-    }
-}
-
-namespace xo {
-    namespace mm {
-        /** @class IGCObjectVisitor_DMockCollector
-         **/
-        class IGCObjectVisitor_DMockCollector {
-        public:
-            /** @defgroup mm-gcobjectvisitor-dmockcollector-type-traits **/
-            ///@{
-            using Copaque = xo::mm::AGCObjectVisitor::Copaque;
-            using Opaque = xo::mm::AGCObjectVisitor::Opaque;
-            ///@}
-            /** @defgroup mm-gcobjectvisitor-dmockcollector-methods **/
-            ///@{
-            // const methods
-            /** allocation metadata for gc-aware data at address @p gco.
-@p gco must be the result of a call to collector's alloc() function **/
-            static AllocInfo alloc_info(const DMockCollector & self, void * addr);
-            /** generation to which pointer @p addr belongs, given role @p r;
-sentinel if @p addr is not owned by collector **/
-            static Generation generation_of(const DMockCollector & self, Role r, const void * addr) noexcept;
-
-            // non-const methods
-            /** allocate copy of source object at address @p src.
-Source must be owned by this collector.
-Increments object age **/
-            static void * alloc_copy(DMockCollector & self, std::byte * src);
-            /** visit child of a gc-aware object. May update child in-place! **/
-            static void visit_child(DMockCollector & self, VisitReason reason, AGCObject * iface, void ** pp_data) noexcept;
-            ///@}
-        };
-
-    } /*namespace mm*/
-} /*namespace xo*/
-
-/* end */

xo-gc/utest/MockCollector.hpp

@@ -1,13 +0,0 @@
-/** @file MockCollector.hpp
- *
- *  @author Roland Conybeare, Apr 2026
- **/
-
-#pragma once
-
-#include "DMockCollector.hpp"
-#include "IGCObjectVisitor_DMockCollector.hpp"
-//#include "ICollector_DMockCollector.hpp"
-//#include "IAllocator_DMockCollector.hpp"
-
-/* end MockCollector.hpp */

xo-gc/utest/init_gc_utest.cpp

@@ -4,7 +4,7 @@
  **/
 
 #include "init_gc_utest.hpp"
-#include "MockCollector.hpp"
+//#include "MockCollector.hpp"
 #include <xo/gc/init_gc.hpp>
 #include <xo/facet/FacetRegistry.hpp>
 #include <xo/indentlog/scope.hpp>
@@ -19,9 +19,9 @@ namespace xo {
     {
         scope log(XO_DEBUG(false));
 
-        FacetRegistry::register_impl<AGCObjectVisitor, DMockCollector>();
+        //FacetRegistry::register_impl<AGCObjectVisitor, DMockCollector>();
 
-        log && log(xtag("DMockCollector.tseq", typeseq::id<DMockCollector>()));
+        //log && log(xtag("DMockCollector.tseq", typeseq::id<DMockCollector>()));
 
         return true;
     }