xo-gc stack: refactor: introduce GCObjectVisitor facet

Plan using to properly level GCObjectStore and MutationLogStore
below Collector.

[WIP] not used yet

CMakeLists.txt

@@ -25,6 +25,13 @@ xo_add_genfacetimpl(
     INPUT idl/ICollector_DX1Collector.json5
 )
 
+# note: manual target; generated code committed to git
+xo_add_genfacetimpl(
+    TARGET xo-gc-facetimpl-gcobjectvisitor-x1collector
+    FACET_PKG xo_alloc2
+    INPUT idl/IGCObjectVisitor_DX1Collector.json5
+)
+
 # ----------------------------------------------------------------
 
 xo_add_genfacet_all(xo-gc-genfacet-all)

idl/IGCObjectVisitor_DX1Collector.json5

@@ -0,0 +1,27 @@
+{
+    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 DX1Collector",
+    using_doxygen: true,
+    repr: "DX1Collector",
+    doc: [
+        "Implement AGCObjectVisitor for DX1Collector.",
+        "Evacuate object pointer (migrate to to-space) during collection phase"
+    ],
+}

include/xo/gc/DX1Collector.hpp

@@ -279,14 +279,10 @@ namespace xo {
              **/
             void forward_inplace(AGCObject * lhs_iface, void ** lhs_data);
 
-#ifdef OBSOLETE
-            /** true iff {alloc_hdr, object_data} should move for
-             *  currently-running collection.
-             *
-             *  Require: runstate_.is_running()
+            /** Supports the GCObjectVisitor facet.
+             *  Synonym for forward_inplace
              **/
-            bool check_move_policy(header_type alloc_hdr, void * object_data) const noexcept;
-#endif
+            void visit_child(AGCObject * lhs_iface, void ** lhs_data);
 
             // ----- allocation -----
 

include/xo/gc/detail/IGCObjectVisitor_DX1Collector.hpp

@@ -0,0 +1,58 @@
+/** @file IGCObjectVisitor_DX1Collector.hpp
+ *
+ *  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_repr.hpp.j2]
+ *  3. idl for facet methods
+ *       [idl/IGCObjectVisitor_DX1Collector.json5]
+ **/
+
+#pragma once
+
+#include "GCObjectVisitor.hpp"
+#include "DX1Collector.hpp"
+
+namespace xo { namespace mm { class IGCObjectVisitor_DX1Collector; } }
+
+namespace xo {
+    namespace facet {
+        template <>
+        struct FacetImplementation<xo::mm::AGCObjectVisitor,
+                                   xo::mm::DX1Collector>
+        {
+            using ImplType = xo::mm::IGCObjectVisitor_Xfer
+              <xo::mm::DX1Collector,
+               xo::mm::IGCObjectVisitor_DX1Collector>;
+        };
+    }
+}
+
+namespace xo {
+    namespace mm {
+        /** @class IGCObjectVisitor_DX1Collector
+         **/
+        class IGCObjectVisitor_DX1Collector {
+        public:
+            /** @defgroup mm-gcobjectvisitor-dx1collector-type-traits **/
+            ///@{
+            using Copaque = xo::mm::AGCObjectVisitor::Copaque;
+            using Opaque = xo::mm::AGCObjectVisitor::Opaque;
+            ///@}
+            /** @defgroup mm-gcobjectvisitor-dx1collector-methods **/
+            ///@{
+            // const methods
+
+            // non-const methods
+            /** visit child of a gc-aware object. May update child in-place! **/
+            static void visit_child(DX1Collector & self, AGCObject * iface, void ** pp_data) noexcept;
+            ///@}
+        };
+
+    } /*namespace mm*/
+} /*namespace xo*/
+
+/* end */

src/gc/CMakeLists.txt

@@ -12,6 +12,7 @@ set(SELF_SRCS
     X1CollectorConfig.cpp
     DX1Collector.cpp
     facet/ICollector_DX1Collector.cpp
+    facet/IGCObjectVisitor_DX1Collector.cpp
 
     DX1CollectorIterator.cpp
 

src/gc/DX1Collector.cpp

@@ -587,6 +587,10 @@ namespace xo {
         DX1Collector::forward_inplace(AGCObject * lhs_iface,
                                       void ** lhs_data)
         {
+            // TODO: streamline once GCObject refactored so that
+            //       forward_children takes GCObjectVisitor instead of Collector
+            //       argument.
+
             Generation upto = runstate_.gc_upto();
 
             if (runstate_.is_running()) {
@@ -601,6 +605,22 @@ namespace xo {
             }
         }
 
+        void
+        DX1Collector::visit_child(AGCObject * lhs_iface,
+                                  void ** lhs_data)
+        {
+            if (runstate_.is_running()) {
+                // called during collection phase
+                this->forward_inplace(lhs_iface, lhs_data);
+            } else if (runstate_.is_verify()) {
+                // called during verify_ok
+                this->_verify_aux(lhs_iface, *lhs_data);
+            } else {
+                // should be unreachable
+                assert(false);
+            }
+        }
+
         void
         DX1Collector::_verify_aux(AGCObject * iface, void * data)
         {

src/gc/facet/IGCObjectVisitor_DX1Collector.cpp

@@ -0,0 +1,27 @@
+/** @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::visit_child(DX1Collector & self, AGCObject * iface, void ** pp_data) noexcept -> void
+        {
+            self.visit_child(iface, pp_data);
+        }
+
+    } /*namespace mm*/
+} /*namespace xo*/
+
+/* end IGCObjectVisitor_DX1Collector.cpp */