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xo-gc stack: refactor: introduce GCObjectVisitor facet

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Plan using to properly level GCObjectStore and MutationLogStore
below Collector.

[WIP] not used yet
This commit is contained in:
Roland Conybeare 2026-04-05 18:07:14 -04:00
commit df0bbe1b31
9 changed files with 489 additions and 0 deletions
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9
CMakeLists.txt
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@ -35,6 +35,15 @@ xo_add_genfacet(
# ---------------------------------------------------------------- # ----------------------------------------------------------------
# note: manual target; generated code committed to git
xo_add_genfacet(
TARGET xo-alloc2-facet-gcobjectvisitor
FACET GCObjectVisitor
INPUT idl/GCObjectVisitor.json5
)
# ----------------------------------------------------------------
# note: manual target; generated code committed to git # note: manual target; generated code committed to git
xo_add_genfacet( xo_add_genfacet(
TARGET xo-alloc2-facet-resourcevisitor TARGET xo-alloc2-facet-resourcevisitor

75
idl/GCObjectVisitor.json5 Normal file
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@ -0,0 +1,75 @@
{
mode: "facet",
output_cpp_dir: "src/alloc2/facet",
output_hpp_dir: "include/xo/alloc2",
output_impl_subdir: "gc",
includes: [
// "<xo/alloc2/Allocator.hpp>",
// "<xo/alloc2/Collector.hpp>",
// "<cstdint>",
// "<cstddef>",
],
// extra includes in GCObject.hpp, if any
user_hpp_includes: [
// "\"gc/RCollector_aux.hpp\"",
],
namespace1: "xo",
namespace2: "mm",
pretext: [
"// see GCObject.hpp, also in xo-alloc2/",
"namespace xo { namespace mm { class AGCObject; }}",
],
facet: "GCObjectVisitor",
detail_subdir: "gc",
brief: "gc-aware object visitor",
using_doxygen: true,
doc: [
"Visit a gc-aware object. Visitor can traverse and update child pointers in-place."
],
types: [
// using size_type = std::size_t
// {
// name: "size_type",
// doc: ["type for an amount of memory"],
// definition: "std::size_t",
// },
// {
// name: "AAllocator",
// doc: ["fomo allocator type"],
// definition: "xo::mm::AAllocator",
// },
// {
// name: "ACollector",
// doc: ["fomo collector type"],
// definition: "xo::mm::ACollector",
// },
],
const_methods: [
// size_type shallow_size() const noexcept
// {
// name: "shallow_size",
// doc: ["memory consumption for this instance"],
// return_type: "size_type",
// args: [],
// const: true,
// noexcept: true,
// attributes: [],
// },
],
nonconst_methods: [
// void visit_child(AGCObject * iface, void ** pp_data) noexcept;
{
name: "visit_child",
doc: ["visit child of a gc-aware object. May update child in-place!"],
return_type: "void",
args:[
{type: "AGCObject *", name: "iface"},
{type: "void **", name: "pp_data"},
],
const: true, // technical const. I/face not modified
noexcept: true,
attributes: [],
},
],
router_facet_explicit_content: []
}

22
include/xo/alloc2/GCObjectVisitor.hpp Normal file
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@ -0,0 +1,22 @@
/** @file GCObjectVisitor.hpp
*
* Generated automagically from ingredients:
* 1. code generator:
* [xo-facet/codegen/genfacet]
* arguments:
* --input [idl/GCObjectVisitor.json5]
* 2. jinja2 template for facet .hpp file:
* [facet.hpp.j2]
* 3. idl for facet methods
* [idl/GCObjectVisitor.json5]
**/
#pragma once
#include "gc/AGCObjectVisitor.hpp"
#include "gc/IGCObjectVisitor_Any.hpp"
#include "gc/IGCObjectVisitor_Xfer.hpp"
#include "gc/RGCObjectVisitor.hpp"
/* end GCObjectVisitor.hpp */

79
include/xo/alloc2/gc/AGCObjectVisitor.hpp Normal file
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@ -0,0 +1,79 @@
/** @file AGCObjectVisitor.hpp
*
* Generated automagically from ingredients:
* 1. code generator:
* [xo-facet/codegen/genfacet]
* arguments:
* --input [idl/GCObjectVisitor.json5]
* 2. jinja2 template for abstract facet .hpp file:
* [abstract_facet.hpp.j2]
* 3. idl for facet methods
* [idl/GCObjectVisitor.json5]
**/
#pragma once
// includes (via {facet_includes})
#include <xo/facet/obj.hpp>
#include <xo/facet/facet_implementation.hpp>
#include <xo/facet/typeseq.hpp>
// see GCObject.hpp, also in xo-alloc2/
namespace xo { namespace mm { class AGCObject; }}
namespace xo {
namespace mm {
using Copaque = const void *;
using Opaque = void *;
/**
Visit a gc-aware object. Visitor can traverse and update child pointers in-place.
**/
class AGCObjectVisitor {
public:
/** @defgroup mm-gcobjectvisitor-type-traits **/
///@{
// types
/** integer identifying a type **/
using typeseq = xo::facet::typeseq;
using Copaque = const void *;
using Opaque = void *;
///@}
/** @defgroup mm-gcobjectvisitor-methods **/
///@{
// const methods
/** An uninitialized AGCObjectVisitor instance will have zero vtable pointer (per {linux,osx} abi).
* Use case for this is narrow. We go to some lengths to avoid null vtable pointers. For example
* obj<AFacet> will have non-null vtable (via IFacet_Any) with all methods terminating.
**/
bool _has_null_vptr() const noexcept { return *reinterpret_cast<const void * const *>(this) == nullptr; }
/** RTTI: unique id# for actual runtime data representation **/
virtual typeseq _typeseq() const noexcept = 0;
/** destroy instance @p d; calls c++ dtor only for actual runtime type; does not recover memory **/
virtual void _drop(Opaque d) const noexcept = 0;
// nonconst methods
/** visit child of a gc-aware object. May update child in-place! **/
virtual void visit_child(Opaque data, AGCObject * iface, void ** pp_data) const noexcept = 0;
///@}
}; /*AGCObjectVisitor*/
/** Implementation IGCObjectVisitor_DRepr of AGCObjectVisitor for state DRepr
* should provide a specialization:
*
* template <>
* struct xo::facet::FacetImplementation<AGCObjectVisitor, DRepr> {
* using Impltype = IGCObjectVisitor_DRepr;
* };
*
* then IGCObjectVisitor_ImplType<DRepr> --> IGCObjectVisitor_DRepr
**/
template <typename DRepr>
using IGCObjectVisitor_ImplType = xo::facet::FacetImplType<AGCObjectVisitor, DRepr>;
} /*namespace mm*/
} /*namespace xo*/
/* AGCObjectVisitor.hpp */

88
include/xo/alloc2/gc/IGCObjectVisitor_Any.hpp Normal file
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@ -0,0 +1,88 @@
/** @file IGCObjectVisitor_Any.hpp
*
* Generated automagically from ingredients:
* 1. code generator:
* [xo-facet/codegen/genfacet]
* arguments:
* --input [idl/GCObjectVisitor.json5]
* 2. jinja2 template for abstract facet .hpp file:
* [iface_facet_any.hpp.j2]
* 3. idl for facet methods
* [idl/GCObjectVisitor.json5]
**/
#pragma once
#include "AGCObjectVisitor.hpp"
#include <xo/facet/obj.hpp>
namespace xo { namespace mm { class IGCObjectVisitor_Any; } }
namespace xo {
namespace facet {
template <>
struct FacetImplementation<xo::mm::AGCObjectVisitor,
DVariantPlaceholder>
{
using ImplType = xo::mm::IGCObjectVisitor_Any;
};
}
}
namespace xo {
namespace mm {
/** @class IGCObjectVisitor_Any
* @brief AGCObjectVisitor implementation for empty variant instance
**/
class IGCObjectVisitor_Any : public AGCObjectVisitor {
public:
/** @defgroup mm-gcobjectvisitor-any-type-traits **/
///@{
/** integer identifying a type **/
using typeseq = xo::facet::typeseq;
///@}
/** @defgroup mm-gcobjectvisitor-any-methods **/
///@{
const AGCObjectVisitor * iface() const { return std::launder(this); }
// from AGCObjectVisitor
// builtin methods
typeseq _typeseq() const noexcept override { return s_typeseq; }
[[noreturn]] void _drop(Opaque) const noexcept override { _fatal(); }
// const methods
// nonconst methods
[[noreturn]] void visit_child(Opaque, AGCObject *, void **) const noexcept override;
///@}
private:
/** @defgraoup mm-gcobjectvisitor-any-private-methods **/
///@{
[[noreturn]] static void _fatal();
///@}
public:
/** @defgroup mm-gcobjectvisitor-any-member-vars **/
///@{
static typeseq s_typeseq;
static bool _valid;
///@}
};
} /*namespace mm */
} /*namespace xo */
/* IGCObjectVisitor_Any.hpp */

82
include/xo/alloc2/gc/IGCObjectVisitor_Xfer.hpp Normal file
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@ -0,0 +1,82 @@
/** @file IGCObjectVisitor_Xfer.hpp
*
* Generated automagically from ingredients:
* 1. code generator:
* [xo-facet/codegen/genfacet]
* arguments:
* --input [idl/GCObjectVisitor.json5]
* 2. jinja2 template for abstract facet .hpp file:
* [iface_facet_any.hpp.j2]
* 3. idl for facet methods
* [idl/GCObjectVisitor.json5]
**/
#pragma once
namespace xo {
namespace mm {
/** @class IGCObjectVisitor_Xfer
**/
template <typename DRepr, typename IGCObjectVisitor_DRepr>
class IGCObjectVisitor_Xfer : public AGCObjectVisitor {
public:
/** @defgroup mm-gcobjectvisitor-xfer-type-traits **/
///@{
/** actual implementation (not generated; often delegates to DRepr) **/
using Impl = IGCObjectVisitor_DRepr;
/** integer identifying a type **/
using typeseq = AGCObjectVisitor::typeseq;
///@}
/** @defgroup mm-gcobjectvisitor-xfer-methods **/
///@{
static const DRepr & _dcast(Copaque d) { return *(const DRepr *)d; }
static DRepr & _dcast(Opaque d) { return *(DRepr *)d; }
// from AGCObjectVisitor
// builtin methods
typeseq _typeseq() const noexcept override { return s_typeseq; }
void _drop(Opaque d) const noexcept override { _dcast(d).~DRepr(); }
// const methods
// non-const methods
void visit_child(Opaque data, AGCObject * iface, void ** pp_data) const noexcept override {
return I::visit_child(_dcast(data), iface, pp_data);
}
///@}
private:
using I = Impl;
public:
/** @defgroup mm-gcobjectvisitor-xfer-member-vars **/
///@{
/** typeseq for template parameter DRepr **/
static typeseq s_typeseq;
/** true iff satisfies facet implementation **/
static bool _valid;
///@}
};
template <typename DRepr, typename IGCObjectVisitor_DRepr>
xo::facet::typeseq
IGCObjectVisitor_Xfer<DRepr, IGCObjectVisitor_DRepr>::s_typeseq
= xo::facet::typeseq::id<DRepr>();
template <typename DRepr, typename IGCObjectVisitor_DRepr>
bool
IGCObjectVisitor_Xfer<DRepr, IGCObjectVisitor_DRepr>::_valid
= xo::facet::valid_facet_implementation<AGCObjectVisitor,
IGCObjectVisitor_Xfer>();
} /*namespace mm */
} /*namespace xo*/
/* end IGCObjectVisitor_Xfer.hpp */

84
include/xo/alloc2/gc/RGCObjectVisitor.hpp Normal file
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@ -0,0 +1,84 @@
/** @file RGCObjectVisitor.hpp
*
* Generated automagically from ingredients:
* 1. code generator:
* [xo-facet/codegen/genfacet]
* arguments:
* --input [idl/GCObjectVisitor.json5]
* 2. jinja2 template for abstract facet .hpp file:
* [iface_facet_any.hpp.j2]
* 3. idl for facet methods
* [idl/GCObjectVisitor.json5]
**/
#pragma once
#include "AGCObjectVisitor.hpp"
namespace xo {
namespace mm {
/** @class RGCObjectVisitor
**/
template <typename Object>
class RGCObjectVisitor : public Object {
private:
using O = Object;
public:
/** @defgroup mm-gcobjectvisitor-router-type-traits **/
///@{
using ObjectType = Object;
using DataPtr = Object::DataPtr;
using typeseq = xo::reflect::typeseq;
///@}
/** @defgroup mm-gcobjectvisitor-router-ctors **/
///@{
RGCObjectVisitor() {}
RGCObjectVisitor(Object::DataPtr data) : Object{std::move(data)} {}
RGCObjectVisitor(const AGCObjectVisitor * iface, void * data)
requires std::is_same_v<typename Object::DataType, xo::facet::DVariantPlaceholder>
: Object(iface, data) {}
///@}
/** @defgroup mm-gcobjectvisitor-router-methods **/
///@{
// explicit injected content
// builtin methods
typeseq _typeseq() const noexcept { return O::iface()->_typeseq(); }
void _drop() const noexcept { O::iface()->_drop(O::data()); }
// const methods
// non-const methods (still const in router!)
void visit_child(AGCObject * iface, void ** pp_data) noexcept {
return O::iface()->visit_child(O::data(), iface, pp_data);
}
///@}
/** @defgroup mm-gcobjectvisitor-member-vars **/
///@{
static bool _valid;
///@}
};
template <typename Object>
bool
RGCObjectVisitor<Object>::_valid = xo::facet::valid_object_router<Object>();
} /*namespace mm*/
} /*namespace xo*/
namespace xo { namespace facet {
template <typename Object>
struct RoutingFor<xo::mm::AGCObjectVisitor, Object> {
using RoutingType = xo::mm::RGCObjectVisitor<Object>;
};
} }
/* end RGCObjectVisitor.hpp */

2
src/alloc2/CMakeLists.txt
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@ -9,7 +9,9 @@ set(SELF_SRCS
CollectorTypeRegistry.cpp CollectorTypeRegistry.cpp
facet/ICollector_Any.cpp facet/ICollector_Any.cpp
IGCObject_Any.cpp IGCObject_Any.cpp
facet/IGCObjectVisitor_Any.cpp
AAllocator.cpp AAllocator.cpp
IAllocator_Any.cpp IAllocator_Any.cpp

48
src/alloc2/facet/IGCObjectVisitor_Any.cpp Normal file
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@ -0,0 +1,48 @@
/** @file IGCObjectVisitor_Any.cpp
*
**/
#include "gc/IGCObjectVisitor_Any.hpp"
#include <iostream>
#include <exception>
namespace xo {
namespace mm {
using xo::facet::DVariantPlaceholder;
using xo::facet::typeseq;
using xo::facet::valid_facet_implementation;
void
IGCObjectVisitor_Any::_fatal()
{
/* control here on uninitialized IAllocator_Any.
* Initialized instance will have specific implementation type
*/
std::cerr << "fatal"
<< ": attempt to call uninitialized"
<< " IGCObjectVisitor_Any method"
<< std::endl;
std::terminate();
}
typeseq
IGCObjectVisitor_Any::s_typeseq = typeseq::id<DVariantPlaceholder>();
bool
IGCObjectVisitor_Any::_valid
= valid_facet_implementation<AGCObjectVisitor, IGCObjectVisitor_Any>();
// nonconst methods
auto
IGCObjectVisitor_Any::visit_child(Opaque, AGCObject *, void **) const noexcept -> void
{
_fatal();
}
} /*namespace mm*/
} /*namespace xo*/
/* end IGCObjectVisitor_Any.cpp */