refactor focusing on xo-alloc2/ xo-gc/ write-barrier

ability to inform allocator of gco->gco mutation, via AAllocator i/face.

include/xo/alloc2/Allocator.hpp

@@ -10,4 +10,6 @@
 #include "alloc/IAllocator_Xfer.hpp"
 #include "alloc/RAllocator.hpp"
 
+#include "alloc/RAllocator_aux.hpp"
+
 /* end Allocator.hpp */

include/xo/alloc2/Allocator_basic.hpp

@@ -0,0 +1,15 @@
+/** @file Allocator_basic.hpp
+ *
+ *  @author Roland Conybeare, Dec 2025
+ **/
+
+#pragma once
+
+#include "alloc/AAllocator.hpp"
+#include "alloc/IAllocator_Any.hpp"
+#include "alloc/IAllocator_Xfer.hpp"
+#include "alloc/RAllocator.hpp"
+
+//#include "alloc/RAllocator_aux.hpp"
+
+/* end Allocator_basic.hpp */

include/xo/alloc2/alloc/AAllocator.hpp

@@ -20,8 +20,8 @@ namespace xo {
         using Copaque = const void *;
         using Opaque = void *;
 
-        // see DArena.hpp
+        class AGCObject;      // see AGCObject.hpp
-        struct DArena;
+        struct DArena;        // see DArena.hpp
 
         /** @class AAllocator
          *  @brief Abstract facet for allocation
@@ -34,6 +34,7 @@ namespace xo {
         public:
             /** @defgroup mm-allocator-type-traits allocator type traits **/
             ///@{
+            using AGCObject = xo::mm::AGCObject;
             /** memory size report **/
             using MemorySizeInfo = xo::mm::MemorySizeInfo;
             /** type used for allocation amounts **/
@@ -155,6 +156,28 @@ namespace xo {
             virtual value_type alloc_copy(Opaque d, value_type src) const = 0;
             /** reset allocator @p d to empty state. **/
             virtual void clear(Opaque d) const = 0;
+            /** assign helper for allocator that may require a write barrier
+             *  (for example Collector). Using obj<AGCObject> here causes
+             *  include cycle, use spelled out form instead;
+             *
+             *  For:
+             *    obj<AGCObject> lhs_ = rhs
+             *  with allocator d, that owns some allocaiton p, would use
+             *    mm.barrier_assign_aux(d, p,
+             *                          lhs_.iface(), lhs_.opaque_data_addr(),
+             *                          rhs.iface(), rhs.opaque_data());
+             *  when lhs has known data type:
+             *    DRepr * lhs_ = rhs.data();
+             *  use
+             *    mm.barrier_assign_aux(d, p,
+             *                          nullptr, lhs_.opaque_data_addr(),
+             *                          rhs.iface(), rhs.opaque_data());
+             *  barrier needs to be able to construct complete fop for rhs
+             *  to administrate write barrier.
+             **/
+            virtual void barrier_assign_aux(Opaque d, void * parent,
+                                            AGCObject * lhs_iface, void ** lhs_data,
+                                            AGCObject * rhs_iface, void * rhs_data) const = 0;
 
             ///@}
         }; /*AAllocator*/

include/xo/alloc2/alloc/IAllocator_Any.hpp

@@ -60,6 +60,10 @@ namespace xo {
             [[noreturn]] value_type      sub_alloc(Opaque, std::size_t, bool) const override { _fatal(); }
             [[noreturn]] value_type     alloc_copy(Opaque, value_type) const override { _fatal(); }
             [[noreturn]] void                clear(Opaque) const override { _fatal(); }
+            [[noreturn]] void   barrier_assign_aux(Opaque,
+                                                   void *,
+                                                   AGCObject *, void **,
+                                                   AGCObject *, void *) const override { _fatal(); }
 
         private:
             [[noreturn]] static void _fatal();

include/xo/alloc2/alloc/IAllocator_Xfer.hpp

@@ -78,6 +78,10 @@ namespace xo {
             value_type    alloc_copy(Opaque d,
                                      value_type src) const override { return I::alloc_copy(_dcast(d), src); }
             void               clear(Opaque d) const override { return I::clear(_dcast(d)); }
+            void  barrier_assign_aux(Opaque d,
+                                     void * parent,
+                                     AGCObject * lhs_iface, void ** lhs_data,
+                                     AGCObject * rhs_iface, void * rhs_data) const override { I::barrier_assign_aux(_dcast(d), parent, lhs_iface, lhs_data, rhs_iface, rhs_data); }
             ///@}
 
         private:

include/xo/alloc2/alloc/RAllocator.hpp

@@ -5,7 +5,7 @@
 
 #pragma once
 
-#include "AAllocator.hpp"
+#include "Allocator_basic.hpp" // omits RAllocator_aux
 #include "AllocIterator.hpp"
 #include <xo/facet/RRouter.hpp>
 #include <string>
@@ -66,13 +66,30 @@ namespace xo {
             AllocInfo   alloc_info(value_type mem) const noexcept { return O::iface()->alloc_info(O::data(), mem); }
             range_type alloc_range(DArena & mm) const noexcept { return O::iface()->alloc_range(O::data(), mm); }
 
+            bool            expand(size_type z) { return O::iface()->expand(O::data(), z); }
             value_type       alloc(typeseq t, size_type z) noexcept { return O::iface()->alloc(O::data(), t, z); }
             value_type super_alloc(typeseq t, size_type z) noexcept { return O::iface()->super_alloc(O::data(), t, z); }
             value_type   sub_alloc(size_type z,
                                    bool complete_flag) noexcept { return O::iface()->sub_alloc(O::data(),
                                                                                              z, complete_flag); }
             value_type  alloc_copy(value_type src) noexcept { return O::iface()->alloc_copy(O::data(), src); }
-            bool            expand(size_type z) { return O::iface()->expand(O::data(), z); }
+            void             clear() { O::iface()->clear(O::data()); }
+            void barrier_assign_aux(void * parent,
+                                    AGCObject * lhs_iface, void ** lhs_data,
+                                    AGCObject * rhs_iface, void * rhs_data) noexcept { O::iface()->barrier_assign_aux(O::data(), parent,
+                                                                                                                      lhs_iface, lhs_data,
+                                                                                                                      rhs_iface, rhs_data); }
+
+            void barrier_assign(void * parent,
+                                obj<AGCObject> * p_lhs,
+                                obj<AGCObject> rhs) noexcept;
+#ifdef NOT_YET
+                this->barrier_assign_aux(parent,
+                                         p_lhs->iface(),
+                                         p_lhs->opaque_data_addr(),
+                                         rhs.iface(),
+                                         rhs.opaque_data());
+#endif
 
             static bool _valid;
         };

include/xo/alloc2/alloc/RAllocator_aux.hpp

@@ -0,0 +1,34 @@
+/** @file RAllocator_aux.hpp
+ *
+ *  Out-of-line definitions for RAllocator template methods
+ *  that depend on RGCObject (avoiding #include cycle in RAllocator.hpp)
+ *
+ *  Would aspire to Include via user_hpp_includes in Allocator.json5,
+ *  if/when that exists
+ *
+ *  @author Roland Conybeare
+ **/
+
+#pragma once
+
+#include "RAllocator.hpp"
+#include "GCObject.hpp"
+
+namespace xo {
+    namespace mm {
+
+        template <typename Object>
+        void
+        RAllocator<Object>::barrier_assign(void * parent,
+                                           obj<AGCObject> * p_lhs,
+                                           obj<AGCObject> rhs) noexcept
+        {
+            (void)parent;
+            (void)p_lhs;
+            (void)rhs;
+        }
+
+    } /*namespace mm*/
+} /*namespace xo*/
+
+/* end RAllocator_aux.hpp */

include/xo/alloc2/arena/IAllocator_DArena.hpp

@@ -75,6 +75,11 @@ namespace xo {
             /** allocate copy of @p src in arena @p d. **/
             static value_type alloc_copy(DArena & d, value_type src);
             static void clear(DArena &);
+            /** perform assignment {*lhs_iface, *lhs_data} = {*rhs_iface, rhs_data} **/
+            static void barrier_assign_aux(DArena &,
+                                           void * parent,
+                                           AGCObject * lhs_iface, void ** lhs_data,
+                                           AGCObject * rhs_iface, void * rhs_data);
             static void destruct_data(DArena &);
         };
 

include/xo/alloc2/gc/ACollector.hpp

@@ -14,7 +14,7 @@
 #pragma once
 
 // includes (via {facet_includes})
-#include <xo/alloc2/Allocator.hpp>
+#include <xo/alloc2/Allocator_basic.hpp>
 #include <xo/alloc2/Generation.hpp>
 #include <xo/alloc2/role.hpp>
 #include <xo/facet/obj.hpp>

include/xo/alloc2/gc/AGCObject.hpp

@@ -14,7 +14,7 @@
 #pragma once
 
 // includes (via {facet_includes})
-#include <xo/alloc2/Allocator.hpp>
+#include <xo/alloc2/Allocator_basic.hpp>
 #include <xo/alloc2/Collector.hpp>
 #include <xo/alloc2/GCObjectVisitor.hpp>
 #include <cstdint>

include/xo/alloc2/gc/ICollector_Xfer.hpp

@@ -13,7 +13,7 @@
 
 #pragma once
 
-#include <xo/alloc2/Allocator.hpp>
+#include <xo/alloc2/Allocator_basic.hpp>
 #include <xo/alloc2/Generation.hpp>
 #include <xo/alloc2/role.hpp>
 

include/xo/alloc2/gc/IGCObject_Xfer.hpp

@@ -13,7 +13,7 @@
 
 #pragma once
 
-#include <xo/alloc2/Allocator.hpp>
+#include <xo/alloc2/Allocator_basic.hpp>
 #include <xo/alloc2/Collector.hpp>
 #include <xo/alloc2/GCObjectVisitor.hpp>
 #include <cstdint>

include/xo/alloc2/gc/RCollector.hpp

@@ -52,7 +52,7 @@ public:
     void * alloc_copy_for(const T * src) noexcept {
         return O::iface()->alloc_copy(O::data(), (std::byte *)const_cast<T *>(src));
     }
-
+    
     /** convenience template for move-constructible T (this is common) **/
     template <typename T>
     T * std_move_for(T * src) noexcept {
@@ -62,28 +62,28 @@ public:
         }
         return nullptr;
     }
-
+    
     /** forward faceted object pointer in place. Defined in GCObject.hpp to avoid #include cycle **/
     template <typename DRepr>
     void forward_inplace(obj<AGCObject,DRepr> * p_obj);
-
+    
     /** another convenience template for forwarding.
      *  Defined in RGCObject.hpp to avoid #include cycle.
     **/
     template <typename DRepr>
     void forward_inplace(DRepr ** pp_repr);
-
+    
     /** convenience template where pointer requires pivot **/
     template <typename AFacet, typename DRepr>
     requires (!std::is_same_v<AFacet, AGCObject>)
     void forward_pivot_inplace(obj<AFacet,DRepr> * p_obj);
-
+    
     /** add root @p p_root **/
     template<typename DRepr>
     void add_gc_root(obj<AGCObject, DRepr> * p_root) {
         O::iface()->add_gc_root_poly(O::data(), (obj<AGCObject> *)p_root);
     }
-
+    
     /** remove root @p p_root **/
     template <typename DRepr>
     void remove_gc_root(obj<AGCObject, DRepr> * p_root) {

include/xo/alloc2/visitor/AResourceVisitor.hpp

@@ -14,7 +14,7 @@
 #pragma once
 
 // includes (via {facet_includes})
-#include "Allocator.hpp"
+#include "Allocator_basic.hpp"
 #include <xo/facet/obj.hpp>
 #include <xo/facet/facet_implementation.hpp>
 #include <xo/facet/typeseq.hpp>

src/alloc2/IAllocator_DArena.cpp

@@ -4,6 +4,7 @@
  **/
 
 #include "AllocIterator.hpp"
+#include "GCObject.hpp"
 #include "arena/IAllocator_DArena.hpp"
 #include "arena/IAllocIterator_DArenaIterator.hpp" // for alloc_range
 #include <xo/arena/DArenaIterator.hpp>
@@ -154,6 +155,31 @@ namespace xo {
             //s.checkpoint_ = s.lo_;
         }
 
+        void
+        IAllocator_DArena::barrier_assign_aux(DArena & s,
+                                              void * parent,
+                                              AGCObject * lhs_iface, void ** lhs_data,
+                                              AGCObject * rhs_iface, void * rhs_data)
+        {
+            (void)s;
+            (void)parent;
+
+            // usually would expect this to just forward to DArena.
+            // That's problematic in this case, because DArena is at lower level
+            // relative to obj<AAllocator,DArena>;
+            // recall that DArena is used in the implementation of xo-facet/
+            //
+            // In any case, for DArena no write barrier is applied.
+            // Instead just perform the fop assignment
+
+            // replacing vtable pointer here
+            if (lhs_iface) {
+                ::memcpy((void *)lhs_iface, (void *)rhs_iface, sizeof(AGCObject));
+            }
+
+            *lhs_data = rhs_data;
+        }
+
         void
         IAllocator_DArena::destruct_data(DArena & s)
         {

utest/DArenaIterator.test.cpp

@@ -5,7 +5,8 @@
 
 #include "Allocator.hpp"
 #include "AllocIterator.hpp"
-#include "arena/IAllocator_DArena.hpp"
+#include "Arena.hpp"
+//#include "arena/IAllocator_DArena.hpp"
 #include "arena/IAllocIterator_DArenaIterator.hpp"
 #include "padding.hpp"
 #include <xo/indentlog/scope.hpp>

utest/arena.test.cpp

@@ -4,8 +4,8 @@
  **/
 
 #include "xo/alloc2/Allocator.hpp"
-#include "xo/alloc2/alloc/IAllocator_Xfer.hpp"
+#include "xo/alloc2/Arena.hpp"
-#include "xo/alloc2/arena/IAllocator_DArena.hpp"
+//#include "xo/alloc2/arena/IAllocator_DArena.hpp"
 #include "xo/arena/print.hpp"
 #include "xo/arena/padding.hpp"
 #include <xo/facet/obj.hpp>