xo-gc xo-object2 xo-facet: builds w/ ISequence,Dlist

xo-cmake/cmake/xo_macros/xo_cxx.cmake

@@ -1646,14 +1646,17 @@ macro(xo_add_genfacet)
         REQUIRED)
     message(STATUS "GENFACET_EXECUTABLE=${GENFACET_EXECUTABLE}")
 
+    set(generatedFiles
+        ${GF_OUTPUT_HPP_DIR}/${FACET}.hpp
+        ${GF_OUTPUT_HPP_DIR}/${GF_OUTPUT_IMPL_SUBDIR}/A${FACET}.hpp
+        ${GF_OUTPUT_HPP_DIR}/${GF_OUTPUT_IMPL_SUBDIR}/I${FACET}_Any.hpp
+        ${GF_OUTPUT_HPP_DIR}/${GF_OUTPUT_IMPL_SUBDIR}/I${FACET}_Xfer.hpp
+        ${GF_OUTPUT_HPP_DIR}/${GF_OUTPUT_IMPL_SUBDIR}/R${FACET}.hpp
+        ${GF_OUTPUT_CPP_DIR}/I${FACET}_Any.cpp)
+
     # Build the genfacet command
     add_custom_command(
-        OUTPUT ${GF_OUTPUT_HPP_DIR}/${FACET}.hpp
+        OUTPUT $generatedFiles
-            ${GF_OUTPUT_HPP_DIR}/${GF_OUTPUT_IMPL_SUBDIR}/A${FACET}.hpp
-            ${GF_OUTPUT_HPP_DIR}/${GF_OUTPUT_IMPL_SUBDIR}/I${FACET}_Any.hpp
-            ${GF_OUTPUT_HPP_DIR}/${GF_OUTPUT_IMPL_SUBDIR}/I${FACET}_Xfer.hpp
-            ${GF_OUTPUT_HPP_DIR}/${GF_OUTPUT_IMPL_SUBDIR}/R${FACET}.hpp
-            ${GF_OUTPUT_CPP_DIR}/I${FACET}_Any.cpp
         COMMAND ${GENFACET_EXECUTABLE}
             --input ${GF_INPUT}
             --output-hpp ${GF_OUTPUT_HPP_DIR}
@@ -1666,7 +1669,50 @@ macro(xo_add_genfacet)
     )
 
     # Create a target for this generation
-    add_custom_target(${GF_TARGET}
+    add_custom_target(${GF_TARGET} DEPENDS ${generatedFiles})
-        DEPENDS ${GF_GENERATED_FILES}
+endmacro()
-    )
+
+macro(xo_add_genfacetimpl)
+    # Parse arguments
+    set(options "")
+    set(oneValueArgs
+        TARGET              # Name for this generation target
+        FACET               # facet name
+        REPR                # representation name
+        INPUT               # Input .json5 file
+        OUTPUT_HPP_DIR      # Directory for .hpp files
+        OUTPUT_IMPL_SUBDIR  # Subdirectory name for impl headers
+        OUTPUT_CPP_DIR      # Directory for .cpp files
+    )
+    set(multiValueArgs "")
+
+    cmake_parse_arguments(GF "${options}" "${oneValueArgs}" "${multiValueArgs}" ${ARGN})
+
+    find_program(GENFACET_EXECUTABLE NAMES genfacet
+        HINTS ${CMAKE_SOURCE_DIR}/xo-facet/codegen
+        DOC "path to xo genfacet code generator"
+        REQUIRED)
+    message(STATUS "GENFACET_EXECUTABLE=${GENFACET_EXECUTABLE}")
+
+    set(generatedFiles
+        ${GF_OUTPUT_HPP_DIR}/${FACET}.hpp
+        ${GF_OUTPUT_HPP_DIR}/${GF_OUTPUT_IMPL_SUBDIR}/I${FACET}_D${REPR}.hpp
+        ${GF_OUTPUT_CPP_DIR}/I${FACET}_D${REPR}.cpp)
+
+    # Build the genfacet command
+    add_custom_command(
+        OUTPUT ${generatedFiles}
+        COMMAND ${GENFACET_EXECUTABLE}
+            --input ${GF_INPUT}
+            --output-hpp ${GF_OUTPUT_HPP_DIR}
+            --output-impl-hpp ${GF_OUTPUT_IMPL_SUBDIR}
+            --output-cpp ${GF_OUTPUT_CPP_DIR}
+        DEPENDS ${GF_INPUT}
+        WORKING_DIRECTORY ${CMAKE_CURRENT_SOURCE_DIR}
+        COMMENT "Generating facet source files from ${GF_INPUT}"
+        VERBATIM
+    )
+
+    # Create a target for this generation
+    add_custom_target(${GF_TARGET} DEPENDS ${generatedFiles})
 endmacro()

xo-facet/codegen/genfacet

@@ -15,12 +15,22 @@ def format_method_qualifiers(method):
     """
     quals = []
     if method.get('const', False):
-        quals.append('const')
+        quals.append(' const')
     if method.get('noexcept', False):
-        quals.append('noexcept')
+        quals.append(' noexcept')
 
     return ' '.join(quals)
 
+def format_method_staticqual(method):
+    """ Build qualifier string for a static method: noexcet
+    """
+    quals = []
+    if method.get('noexcept', False):
+        quals.append(' noexcept')
+
+    return ' '.join(quals)
+
+
 def format_args(args, include_names=True):
     """ Format argument list for a method
     """
@@ -40,6 +50,12 @@ def format_arg_names(args):
     names = [p['name'] for p in args]
     return ', '.join([f"_dcast({names[0]})"] + names[1:])
 
+def format_arg_names_nodata(args):
+    """ Format argument names for forwarding, omit data ('self') arg
+    """
+    names = [p['name'] for p in args[1:]]
+    return ', '.join(names)
+
 def format_args_nodata(args):
     """ Format arguments, but exclude data arg
     """
@@ -51,46 +67,21 @@ def format_args_routing(args):
     names = [p['name'] for p in args]
     return ', '.join([f"O::data()"] + names[1:])
 
-def main():
+def format_args_impl(args, drepr):
-    parser = argparse.ArgumentParser()
+    """ Format argument names, for implementation (IFoo_DRepr)
-    parser.add_argument('--input', required=True, help='input IDL JSON5 file')
+    """
-    parser.add_argument('--output-impl-hpp', required=True, help='.hpp detail subdir')
+    names = [f"{p['type']} {p['name']}" for p in args]
-    parser.add_argument('--output-hpp', required=True, help='.hpp output directory')
+    return ', '.join([f"const {drepr} & self"] + names[1:])
-    parser.add_argument('--output-cpp', required=True, help='.cpp output directory')
 
-    args = parser.parse_args()
 
-    idl_fname = args.input
+def gen_facet(env,
-    idl = load_idl(idl_fname)
+              idl_fname,
-    #
+              idl,
-    output_hpp_dir = Path(args.output_hpp)
+              input_json5,
-    output_hpp_dir.mkdir(parents=False, exist_ok=True)
+              output_hpp_dir,
-    #
+              output_impl_hpp_dir,
-    output_impl_hpp_subdir = Path(args.output_impl_hpp)
+              output_cpp_dir):
-    output_impl_hpp_dir = Path(args.output_hpp) / output_impl_hpp_subdir
-    output_impl_hpp_dir.mkdir(parents=False, exist_ok=True)
-    #
-    output_cpp_dir = Path(args.output_cpp)
-    output_cpp_dir.mkdir(parents=False, exist_ok=True)
 
-    # setup jinja2
-    #template_dir = Path(args.templates)
-    template_dir = Path(__file__).parent
-    #template_dir = Path(__file__).parent / 'codegen'
-
-    print(f'template_dir: [{template_dir}]')
-
-    env = Environment(loader = FileSystemLoader(template_dir),
-                      trim_blocks = True,
-                      lstrip_blocks = True)
-
-    # custom filters
-    env.filters['qualifiers'] = format_method_qualifiers
-    env.filters['args'] = format_args
-    env.filters['argtypes'] = format_args_nonames
-    env.filters['argnames'] = format_arg_names
-    env.filters['argsnodata'] = format_args_nodata
-    env.filters['argrouting'] = format_args_routing
 
     # true to insert doxygen markup in generated .hpp/.cpp files
     using_dox = idl['using_doxygen']
@@ -150,7 +141,7 @@ def main():
 
     context = {
         'genfacet': __file__,
-        'genfacet_input': args.input,
+        'genfacet_input': idl_fname,
         'using_dox': using_dox,
         'impl_hpp_subdir': output_impl_hpp_subdir,
         #
@@ -225,5 +216,282 @@ def main():
         print(f"Generated {out_dir}/{out_file}")
 
 
+
+def gen_facet_impl(env,
+                   idl_fname,
+                   idl,
+                   facet_idl,
+                   output_hpp_dir,
+                   output_impl_hpp_subdir,
+                   output_cpp_dir):
+
+
+    # true to insert doxygen markup in generated .hpp/.cpp files
+    using_dox = idl['using_doxygen']
+
+    # extra include files (or perhaps other definitions)
+
+    # facet_includes: include section for AFoo.hpp:
+    # <xo/gc/GCObject.hpp>
+    facet_includes = facet_idl['includes']
+    # sequence
+    facet_detail_subdir = facet_idl['detail_subdir']
+    # xo - facet_ns1: outer namespace for facet [e.g. xo]
+    facet_ns1 = facet_idl['namespace1']
+    # scm - facet_ns2: nested namespace for facet [e.g. scm]
+    facet_ns2 = facet_idl['namespace2']
+
+    # Sequence - facet_name: facet name
+    facet_name = facet_idl['facet']
+    # sequence - facet_name_lc: lower case [e.g. sequence]
+    facet_name_lc = facet_name.lower()
+    # brief doc for facet
+    facet_brief = idl['brief']
+    # doc section for facet
+    facet_doc = '\n'.join(idl['doc'])
+
+    types = facet_idl['types']
+    for ty in types:
+        ty['doc'] = '\n'.join(ty['doc'])
+
+    const_methods = facet_idl['const_methods']
+    for md in const_methods:
+        md['args'] = [{'type': "Copaque",
+                       'name': "data"}] + md['args']
+        md['doc'] = '\n'.join(md['doc'])
+
+    nonconst_methods = facet_idl['nonconst_methods']
+    for md in nonconst_methods:
+        md['args'] = [{'type': "Opaque",
+                       'name': "data"}] + md['args']
+        md['doc'] = '\n'.join(md['doc'])
+
+    # Foo.hpp
+    facet_hpp_fname = f'{facet_name}.hpp'
+    # AFoo
+    abstract_facet = f'A{facet_name}'
+    # AFoo.hpp
+    abstract_facet_fname = f'{abstract_facet}.hpp'
+    # IFoo
+    iface_facet = f'I{facet_name}'
+    # IFoo_ImplType
+    iface_facet_impltype = f'{iface_facet}_ImplType'
+    #
+    # IFoo_Any
+    iface_facet_any = f'{iface_facet}_Any'
+    # IFoo_Any.hpp
+    iface_facet_any_hpp_fname = f'{iface_facet_any}.hpp'
+    # IFoo_Any.cpp
+    iface_facet_any_cpp_fname = f'{iface_facet_any}.cpp'
+    #
+    # IFoo_Xfer
+    iface_facet_xfer = f'{iface_facet}_Xfer'
+    # IFoo_Xfer.hpp
+    iface_facet_xfer_hpp_fname = f'{iface_facet_xfer}.hpp'
+    # IFoo_Xfer.cpp
+    iface_facet_xfer_cpp_fname = f'{iface_facet_xfer}.cpp'
+    #
+    # RFoo
+    router_facet = f'R{facet_name}'
+    # RFoo.hpp
+    router_facet_hpp_fname = f'{router_facet}.hpp'
+
+    # ================================================================
+    # vars for IFacet_DRepr
+    # ----------------------------------------------------------------
+
+    # DList
+    data_repr = idl['repr']
+    # dlist
+    data_repr_lc = data_repr.lower()
+    # DList.hpp
+    data_repr_hpp_fname = f'{data_repr}.hpp'
+
+    # repr_ns1: outer namespace for repr [e.g. xo].
+    #           (need not match facet)
+    repr_ns1 = idl['namespace1']
+    # repr_ns2: nested namespace for repr [e.g. scm].
+    repr_ns2 = idl['namespace2']
+
+
+    # iface_facet_repr: IFoo_DRepr
+    iface_facet_repr = f'{iface_facet}_{data_repr}'
+    # iface_facet_repr_hpp_fname: IFoo_DRepr.hpp
+    iface_facet_repr_hpp_fname = f'{iface_facet_repr}.hpp'
+    # iface_facet_repr_cpp_fname: IFoo_DRepr.cpp
+    iface_facet_repr_cpp_fname = f'{iface_facet_repr}.cpp'
+
+    # ================================================================
+
+    context = {
+        'genfacet': __file__,
+        'genfacet_input': idl_fname,
+        'using_dox': using_dox,
+        'impl_hpp_subdir': output_impl_hpp_subdir,
+        #
+        'facet_hpp_j2': 'facet.hpp.j2',
+        'facet_includes': facet_includes,
+        'facet_detail_subdir': facet_detail_subdir,
+        'facet_ns1': facet_ns1,
+        'facet_ns2': facet_ns2,
+        'facet_name': facet_name,
+        'facet_name_lc': facet_name_lc,
+        'facet_hpp_fname': facet_hpp_fname,
+        #'name': facet_name,
+        'idl_fname': idl_fname,
+        #
+        'abstract_facet_hpp_j2': 'abstract_facet.hpp.j2',
+        'abstract_facet': abstract_facet,
+        'abstract_facet_fname': abstract_facet_fname,
+        'abstract_facet_doc': facet_doc,
+        #
+        'iface_facet': iface_facet,
+        'iface_facet_impltype': iface_facet_impltype,
+        #
+        'iface_facet_any': iface_facet_any,
+        'iface_facet_any_hpp_j2': 'iface_facet_any.hpp.j2',
+        'iface_facet_any_cpp_j2': 'iface_facet_any.cpp.j2',
+        'iface_facet_any_hpp_fname': iface_facet_any_hpp_fname,
+        'iface_facet_any_cpp_fname': iface_facet_any_cpp_fname,
+        #
+        'iface_facet_xfer': iface_facet_xfer,
+        'iface_facet_xfer_hpp_j2': 'iface_facet_xfer.hpp.j2',
+        'iface_facet_xfer_cpp_j2': 'iface_facet_xfer.cpp.j2',
+        'iface_facet_xfer_hpp_fname': iface_facet_xfer_hpp_fname,
+        'iface_facet_xfer_cpp_fname': iface_facet_xfer_cpp_fname,
+        #
+        'router_facet': router_facet,
+        'router_facet_hpp_j2': 'router_facet.hpp.j2',
+        'router_facet_hpp_fname': router_facet_hpp_fname,
+        #
+        'types': types,
+        #
+        'const_methods': const_methods,
+        #
+        'nonconst_methods': nonconst_methods,
+
+        # ----------------------------------------------------------------
+        # vars for IFacet_DRepr
+        # ----------------------------------------------------------------
+
+        'repr_ns1': repr_ns1,
+        'repr_ns2': repr_ns2,
+        #
+        'data_repr': data_repr,
+        'data_repr_lc': data_repr_lc,
+        'data_repr_hpp_fname': data_repr_hpp_fname,
+        #
+        'iface_facet_repr': iface_facet_repr,
+        'iface_facet_repr_hpp_j2': 'iface_facet_repr.hpp.j2',
+        'iface_facet_repr_hpp_fname': iface_facet_repr_hpp_fname,
+        'iface_facet_repr_cpp_j2': 'iface_facet_repr.cpp.j2',
+        'iface_facet_repr_cpp_fname': iface_facet_repr_cpp_fname,
+        #
+
+    }
+
+    # generate .hpp files
+
+    templates = {}
+    templates[iface_facet_repr_hpp_fname] = [output_hpp_dir,
+                                             context['iface_facet_repr_hpp_j2']]
+    templates[iface_facet_repr_cpp_fname] = [output_cpp_dir,
+                                             context['iface_facet_repr_cpp_j2']]
+
+#    templates[facet_hpp_fname] = [output_hpp_dir,
+#                                  context['facet_hpp_j2']]
+#    templates[abstract_facet_fname] = [output_impl_hpp_dir,
+#                                       context['abstract_facet_hpp_j2']]
+#    templates[iface_facet_any_hpp_fname] = [output_impl_hpp_dir,
+#                                            context['iface_facet_any_hpp_j2']]
+#    templates[iface_facet_any_cpp_fname] = [output_cpp_dir,
+#                                            context['iface_facet_any_cpp_j2']]
+#    templates[iface_facet_xfer_hpp_fname] = [output_impl_hpp_dir,
+#                                             context['iface_facet_xfer_hpp_j2']]
+#    templates[router_facet_hpp_fname] = [output_impl_hpp_dir,
+#                                         context['router_facet_hpp_j2']]
+
+    for out_file, record in templates.items():
+        out_dir = record[0]
+        template_name = record[1]
+
+        print(f'out_dir: [{out_dir}]')
+        print(f'out_file: [{out_file}]')
+        print(f'template_name: [{template_name}]')
+
+        template = env.get_template(template_name)
+        content = template.render(**context)
+
+        (out_dir / out_file).write_text(content)
+        print(f"Generated {out_dir}/{out_file}")
+
+def main():
+    parser = argparse.ArgumentParser()
+    parser.add_argument('--input', required=True, help='input IDL JSON5 file')
+    # --output-impl-hpp: putting this in .json5, will be able to drop this.
+    parser.add_argument('--output-impl-hpp', required=True, help='.hpp detail subdir')
+    parser.add_argument('--output-hpp', required=True, help='.hpp output directory')
+    parser.add_argument('--output-cpp', required=True, help='.cpp output directory')
+
+    args = parser.parse_args()
+
+    idl_fname = args.input
+    idl = load_idl(idl_fname)
+
+    output_hpp_dir = Path(args.output_hpp)
+    output_hpp_dir.mkdir(parents=False, exist_ok=True)
+
+    # TODO: output_impl_hpp_subdir: use idl['detail_subdir'] instead
+    output_impl_hpp_subdir = Path(args.output_impl_hpp)
+    output_impl_hpp_dir = Path(args.output_hpp) / output_impl_hpp_subdir
+    output_impl_hpp_dir.mkdir(parents=False, exist_ok=True)
+
+    output_cpp_dir = Path(args.output_cpp)
+    output_cpp_dir.mkdir(parents=False, exist_ok=True)
+
+    # setup jinja2
+    #template_dir = Path(args.templates)
+    template_dir = Path(__file__).parent
+    #template_dir = Path(__file__).parent / 'codegen'
+
+    print(f'template_dir: [{template_dir}]')
+
+    env = Environment(loader = FileSystemLoader(template_dir),
+                      trim_blocks = True,
+                      lstrip_blocks = True)
+
+    # custom filters.
+    # A filter 'foo' provides ability to write '{{var | foo}}' to expand
+    # j2 variable 'var' to 'filters[foo](var)'
+    #
+    env.filters['qualifiers'] = format_method_qualifiers
+    env.filters['staticqual'] = format_method_staticqual
+    env.filters['args'] = format_args
+    env.filters['argtypes'] = format_args_nonames
+    env.filters['argnames'] = format_arg_names
+    env.filters['argnamesnodata'] = format_arg_names_nodata
+    env.filters['argsnodata'] = format_args_nodata
+    env.filters['argrouting'] = format_args_routing
+    env.filters['argimpl'] = format_args_impl
+
+    if idl['mode'] == 'facet':
+        gen_facet(env,
+                  idl_fname,
+                  idl,
+                  output_hpp_dir,
+                  output_impl_hpp_dir,
+                  output_cpp_dir)
+    elif idl['mode'] == 'implementation':
+        facet_idl_fname = idl['facet_idl']
+        facet_idl = load_idl(facet_idl_fname)
+
+        gen_facet_impl(env,
+                       idl_fname,
+                       idl,
+                       facet_idl,
+                       output_hpp_dir,
+                       output_impl_hpp_dir,
+                       output_cpp_dir)
+
 if __name__ == '__main__':
     main()

xo-facet/codegen/iface_facet_repr.cpp.j2

@@ -0,0 +1,34 @@
+/** @file {{iface_facet_repr_cpp_fname}}
+ *
+ *  Generated automagically from ingredients:
+ *  1. code generator:
+ *       [{{genfacet}}]
+ *     arguments:
+ *       --input [{{genfacet_input}}]
+ *  2. jinja2 template for abstract facet .hpp file:
+ *       [{{ iface_facet_any_hpp_j2 }}]
+ *  3. idl for facet methods
+ *       [{{ idl_fname }}]
+**/
+
+#include "{{iface_facet_repr_hpp_fname}}"
+
+namespace {{repr_ns1}} {
+    namespace {{repr_ns2}} {
+        {% for md in const_methods %}
+        auto
+        {{iface_facet_repr}}::{{md.name}}({{md.args | argimpl(data_repr)}}){{md | staticqual}} -> {{md.return_type}}
+        {
+            {% if md.return_type == "void" %}
+            self.{{md.name}}({{md.args | argnamesnodata}});
+            {% else %}
+            return self.{{md.name}}({{md.args | argnamesnodata}});
+            {% endif %}
+        }
+
+        {% endfor %}
+
+    } /*namespace {{repr_ns2}}*/
+} /*namespace {{repr_ns1}}*/
+
+/* end {{iface_facet_repr_cpp_fname}} */

xo-facet/codegen/iface_facet_repr.hpp.j2

@@ -0,0 +1,70 @@
+/** @file {{iface_facet_repr_hpp_fname}}
+ *
+ *  Generated automagically from ingredients:
+ *  1. code generator:
+ *       [{{genfacet}}]
+ *     arguments:
+ *       --input [{{genfacet_input}}]
+ *  2. jinja2 template for abstract facet .hpp file:
+ *       [{{ iface_facet_any_hpp_j2 }}]
+ *  3. idl for facet methods
+ *       [{{ idl_fname }}]
+ **/
+
+#pragma once
+
+#include "{{facet_hpp_fname}}"
+#include "{{facet_detail_subdir}}/{{iface_facet_xfer_hpp_fname}}"
+#include "{{data_repr_hpp_fname}}"
+
+namespace {{repr_ns1}} { namespace {{repr_ns2}} { class {{iface_facet_repr}}; } }
+
+namespace xo {
+    namespace facet {
+        template <>
+        struct FacetImplementation<{{facet_ns1}}::{{facet_ns2}}::{{abstract_facet}},
+                                   {{repr_ns1}}::{{repr_ns2}}::{{data_repr}}>
+        {
+            using ImplType = {{facet_ns1}}::{{facet_ns2}}::{{iface_facet_xfer}}
+              <{{repr_ns1}}::{{repr_ns2}}::{{data_repr}},
+               {{repr_ns1}}::{{repr_ns2}}::{{iface_facet_repr}}>;
+        };
+    }
+}
+
+namespace {{repr_ns1}} {
+    namespace {{repr_ns2}} {
+        /** @class {{iface_facet_repr}}
+         **/
+        class {{iface_facet_repr}} {
+        public:
+            {% if using_dox %}
+            /** @defgroup {{repr_ns2}}-{{facet_name_lc}}-{{data_repr_lc}}-type-traits **/
+            ///@{
+            {% endif %}
+            {% for ty in types %}
+            using {{ty.name}} = {{abstract_facet}}::{{ty.name}};
+            {% endfor %}
+            {% if using_dox %}
+            ///@}
+            /** @defgroup {{repr_ns2}}-{{facet_name_lc}}-{{data_repr_lc}}-methods **/
+            ///@{
+            {% endif %}
+            {% for md in const_methods %}
+            /** {{md.doc}} **/
+            static {{md.return_type}} {{md.name}}({{md.args | argimpl(data_repr)}}){{md | staticqual}};
+            {% endfor %}
+
+            {% for md in methods %}
+            /** {{md.doc}} **/
+            static {{md.return_type}} {{md.name}}({{md.args | argimpl(data_repr)}}){{md | staticqual}};
+            {% endfor %}
+            {% if using_dox %}
+            ///@}
+            {% endif %}
+        };
+
+    } /*namespace {{repr_ns2}}*/
+} /*namespace {{repr_ns1}}*/
+
+/* end */

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

@@ -5,7 +5,7 @@
 
 #pragma once
 
-#include "IGCObject_Any.hpp"
+//#include "IGCObject_Any.hpp"
 
 #include <xo/facet/facet_implementation.hpp>
 #include <xo/facet/typeseq.hpp>
@@ -22,6 +22,7 @@ namespace xo {
         using Copaque = const void *;
         using Opaque = void *;
 
+        struct AGCObject;
         struct IGCObject_Any; // see IGCObject_Any.hpp
 
         /** @class ACollector
@@ -53,10 +54,12 @@ namespace xo {
             virtual void install_type(Opaque d, int32_t tseq, IGCObject_Any & iface) = 0;
             virtual void add_gc_root(Opaque d, int32_t tseq, Opaque * root) = 0;
 
-            /** evacuate @p *lhs to to-space and replace with forwarding pointer
+            /** evacuate @p *lhs, that refers to state with interface @p lhs_iface,
+             *  to collector @p d's to-space. Replace *lhs_data with forwarding pointer
+             *
              *  Require: gc in progress
              **/
-            virtual void forward_inplace(Opaque d, obj<AGCObject> * lhs) = 0;
+            virtual void forward_inplace(Opaque d, AGCObject * lhs_iface, void ** lhs_data) = 0;
         };
     }
 

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

@@ -17,6 +17,8 @@ namespace xo {
         using Copaque = const void *;
         using Opaque = void *;
 
+        struct ACollector;
+
         /** @class AObject
          *  @brief Abstract facet for collector-eligible data
          *
@@ -30,9 +32,10 @@ namespace xo {
             virtual int32_t _typeseq() const noexcept = 0;
 
             virtual size_type shallow_size(Copaque d) const noexcept = 0;
-            virtual Opaque * shallow_copy(Copaque d,
+            virtual Opaque shallow_copy(Copaque d,
-                                          obj<AAllocator> mm) const noexcept = 0;
+                                        obj<AAllocator> mm) const noexcept = 0;
-            virtual size_type forward_children(Opaque d) const noexcept = 0;
+            virtual size_type forward_children(Opaque d,
+                                               obj<ACollector>) const noexcept = 0;
         };
 
         // implementation IGCObject_DRepr of AGCObject for state DRepr

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

@@ -36,7 +36,7 @@ namespace xo {
             // non-const methods
             [[noreturn]] void install_type(Opaque, int32_t, IGCObject_Any &) noexcept override { _fatal(); }
             [[noreturn]] void add_gc_root(Opaque, int32_t, Opaque *) override { _fatal(); }
-            [[noreturn]] void forward_inplace(Opaque, obj<AGCObject> *) override { _fatal(); }
+            [[noreturn]] void forward_inplace(Opaque, AGCObject *, void **) override { _fatal(); }
 
         private:
             [[noreturn]] static void _fatal();

xo-gc/include/xo/gc/detail/ICollector_DX1Collector.hpp

@@ -44,7 +44,7 @@ namespace xo {
             static void install_type(DX1Collector & d,
                                      int32_t seq, IGCObject_Any & iface);
             static void add_gc_root(DX1Collector & d, int32_t tseq, Opaque * root);
-            static void forward_inplace(DX1Collector & d, obj<AGCObject> * lhs);
+            static void forward_inplace(DX1Collector & d, AGCObject * lhs_iface, void ** lhs_data);
 
             static int32_t s_typeseq;
             static bool _valid;

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

@@ -49,8 +49,8 @@ namespace xo {
             void add_gc_root(Opaque d, int32_t tseq, Opaque * root) override {
                 I::add_gc_root(_dcast(d), tseq, root);
             }
-            void forward_inplace(Opaque d, obj<AGCObject> * lhs) override {
+            void forward_inplace(Opaque d, AGCObject * lhs_iface, void ** lhs_data) override {
-                I::forward_inplace(_dcast(d), lhs);
+                I::forward_inplace(_dcast(d), lhs_iface, lhs_data);
             }
 
         private:

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

@@ -6,6 +6,7 @@
 #pragma once
 
 #include "AGCObject.hpp"
+#include "Collector.hpp"
 #include <new>
 
 namespace xo {
@@ -31,9 +32,10 @@ namespace xo {
             int32_t _typeseq() const noexcept override { return s_typeseq; }
 
             [[noreturn]] size_type shallow_size(Copaque) const noexcept override { _fatal(); }
-            [[noreturn]] Opaque * shallow_copy(Copaque,
+            [[noreturn]] Opaque shallow_copy(Copaque,
-                                               obj<AAllocator>) const noexcept override { _fatal(); }
+                                             obj<AAllocator>) const noexcept override { _fatal(); }
-            [[noreturn]] size_type forward_children(Opaque) const noexcept override { _fatal(); }
+            [[noreturn]] size_type forward_children(Opaque,
+                                                    obj<ACollector>) const noexcept override { _fatal(); }
 
         private:
             [[noreturn]] static void _fatal();

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

@@ -6,6 +6,7 @@
 #pragma once
 
 #include "AGCObject.hpp"
+#include "ACollector.hpp"
 
 namespace xo {
     namespace mm {
@@ -28,16 +29,17 @@ namespace xo {
 
             int32_t _typeseq() const noexcept override { return s_typeseq; }
             size_type shallow_size(Copaque d) const noexcept override {
-                return I::shallow_copy(_dcast(d));
+                return I::shallow_size(_dcast(d));
             }
-            Opaque * shallow_copy(Copaque d, obj<AAllocator> mm) const noexcept override {
+            Opaque shallow_copy(Copaque d, obj<AAllocator> mm) const noexcept override {
-                return I::shallow_size(_dcast(d), mm);
+                return I::shallow_copy(_dcast(d), mm);
             }
 
             // non-const methods
 
-            size_type forward_children(Opaque d) const noexcept override {
+            size_type forward_children(Opaque d,
-                return I::forward_children(d);
+                                       obj<ACollector> gc) const noexcept override {
+                return I::forward_children(_dcast(d), gc);
             }
 
         private:

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

@@ -30,7 +30,7 @@ namespace xo {
             void install_type(int32_t tseq, IGCObject_Any & iface) { return O::iface()->install_type(O::data(), tseq, iface); }
             void add_gc_root(int32_t tseq, Opaque * root) { O::iface()->add_gc_root(O::data(), tseq, root); }
 
-            void forward_inplace(obj<AGCObject> * lhs) { O::iface()->forward_inplace(O::data(), lhs); }
+            void forward_inplace(AGCObject * lhs_iface, void ** lhs_data) { O::iface()->forward_inplace(O::data(), lhs_iface, lhs_data); }
 
             static bool _valid;
         };

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

@@ -25,7 +25,7 @@ namespace xo {
 
             int32_t _typeseq() const noexcept { return O::iface()->_typeseq(); }
             size_type shallow_size() const noexcept { O::iface()->shallow_size(O::data()); }
-            Opaque * shallow_copy(obj<AAllocator> mm) const noexcept { O::iface()->shallow_copy(O::data(), mm); }
+            Opaque shallow_copy(obj<AAllocator> mm) const noexcept { O::iface()->shallow_copy(O::data(), mm); }
             size_type forward_children() noexcept { O::iface()->forward_children(O::data()); }
 
             static bool _valid;

xo-gc/src/gc/ICollector_DX1Collector.cpp

@@ -73,8 +73,10 @@ namespace xo {
 
         void
         ICollector_DX1Collector::forward_inplace(DX1Collector & d,
-                                                 obj<AGCObject> * lhs)
+                                                 AGCObject * lhs_iface,
+                                                 void ** lhs_data)
         {
+            (void)lhs_iface;
             assert(d.runstate_.is_running());
 
             /*
@@ -90,7 +92,7 @@ namespace xo {
              *                                    +----------+
              */
 
-            void * object_data = (byte *)(*lhs).opaque_data();
+            void * object_data = (byte *)lhs_data;
 
             if (!d.contains(role::from_space(), object_data)) {
                 /* *lhs isn't in GC-allocated space.
@@ -143,7 +145,7 @@ namespace xo {
                 void * dest = *(void**)object_data;
 
                 /* update *lhs in-place */
-                (*lhs).reset_opaque(dest);
+                *lhs_data = dest;
             } else if (check_move_policy(d, alloc_hdr, object_data)) {
                 /* copy object *lhs + replace with forwarding pointer */
 

xo-object2/CMakeLists.txt

@@ -27,6 +27,16 @@ xo_add_genfacet(
     OUTPUT_CPP_DIR src/object2
 )
 
+xo_add_genfacetimpl(
+    TARGET xo-object2-facetimpl-sequence-list
+    FACET Sequence
+    REPR List
+    INPUT idl/ISequence_DList.json5
+    OUTPUT_HPP_DIR include/xo/object2
+    OUTPUT_IMPL_SUBDIR sequence
+    OUTPUT_CPP_DIR src/object2
+)
+
 # ----------------------------------------------------------------
 
 # must complete definition of expression lib before configuring examples

xo-object2/idl/ISequence_DList.json5

@@ -0,0 +1,12 @@
+{
+    mode: "implementation",
+    includes: [],
+    namespace1: "xo",
+    namespace2: "scm",
+    facet_idl: "idl/Sequence.json5",
+    brief: "provide ASequence interface for DList state",
+    using_doxygen: true,
+    repr: "DList",
+    doc: [ "doc for something or other"
+    ],
+}

xo-object2/idl/Sequence.json5

@@ -1,8 +1,10 @@
 {
+    mode: "facet",
     includes: ["<xo/gc/GCObject.hpp>"],
     namespace1: "xo",
     namespace2: "scm",
     facet: "Sequence",
+    detail_subdir: "sequence",
     brief: "an ordered collection of variants",
     using_doxygen: true,
     doc: [

xo-object2/include/xo/object2/DList.hpp

@@ -11,13 +11,23 @@ namespace xo {
     namespace scm {
 
         struct DList {
+            using size_type = std::size_t;
             using AGCObject = xo::mm::AGCObject;
 
             DList(xo::obj<AGCObject> h,
-                  xo::obj<AGCObject> r) : head_{h}, rest_{r} {}
+                  DList * r) : head_{h}, rest_{r} {}
+
+            /** DList length is at least 1 **/
+            bool is_empty() const noexcept { return false; };
+            /** DList models a finite sequence **/
+            bool is_finite() const noexcept { return true; };
+            /** return number of elements in this DList **/
+            size_type size() const noexcept;
+            /** return element at 0-based index @p ix **/
+            obj<AGCObject> at(size_type ix) const;
 
             obj<AGCObject> head_;
-            obj<AGCObject> rest_;
+            DList * rest_ = nullptr;
         };
 
     } /*namespace scm*/

xo-object2/include/xo/object2/IGCObject_DFloat.hpp

@@ -5,6 +5,7 @@
 
 #pragma once
 
+#include <xo/gc/Collector.hpp>
 #include <xo/alloc2/alloc/AAllocator.hpp>
 #include <xo/gc/detail/AGCObject.hpp>
 #include <xo/gc/detail/IGCObject_Xfer.hpp>

xo-object2/include/xo/object2/IGCObject_DInteger.hpp

@@ -5,6 +5,7 @@
 
 #pragma once
 
+#include <xo/gc/Collector.hpp>
 #include "xo/alloc2/alloc/AAllocator.hpp"
 #include <xo/gc/detail/AGCObject.hpp>
 #include <xo/gc/detail/IGCObject_Xfer.hpp>

xo-object2/include/xo/object2/IGCObject_DList.hpp

@@ -13,6 +13,19 @@
 #include "DList.hpp"
 
 namespace xo {
+    namespace scm { struct IGCObject_DList; }
+
+    namespace facet {
+        template <>
+        struct FacetImplementation<xo::mm::AGCObject,
+                                   xo::scm::DList>
+        {
+            using ImplType = xo::mm::IGCObject_Xfer
+                <xo::scm::DList,
+                 xo::scm::IGCObject_DList>;
+        };
+    }
+
     namespace scm {
         /* changes here coordinate with:
          *  IGCObject_XFer

xo-object2/include/xo/object2/ISequence_DList.hpp

@@ -0,0 +1,61 @@
+/** @file ISequence_DList.hpp
+ *
+ *  Generated automagically from ingredients:
+ *  1. code generator:
+ *       [/Users/roland/proj/xo-umbrella2/xo-facet/codegen/genfacet]
+ *     arguments:
+ *       --input [idl/ISequence_DList.json5]
+ *  2. jinja2 template for abstract facet .hpp file:
+ *       [iface_facet_any.hpp.j2]
+ *  3. idl for facet methods
+ *       [idl/ISequence_DList.json5]
+ **/
+
+#pragma once
+
+#include "Sequence.hpp"
+#include "sequence/ISequence_Xfer.hpp"
+#include "DList.hpp"
+
+namespace xo { namespace scm { class ISequence_DList; } }
+
+namespace xo {
+    namespace facet {
+        template <>
+        struct FacetImplementation<xo::scm::ASequence,
+                                   xo::scm::DList>
+        {
+            using ImplType = xo::scm::ISequence_Xfer
+              <xo::scm::DList,
+               xo::scm::ISequence_DList>;
+        };
+    }
+}
+
+namespace xo {
+    namespace scm {
+        /** @class ISequence_DList
+         **/
+        class ISequence_DList {
+        public:
+            /** @defgroup scm-sequence-dlist-type-traits **/
+            ///@{
+            using size_type = ASequence::size_type;
+            using AGCObject = ASequence::AGCObject;
+            ///@}
+            /** @defgroup scm-sequence-dlist-methods **/
+            ///@{
+            /** true iff sequence is empty **/
+            static bool is_empty(const DList & self) noexcept;
+            /** true iff sequence is finite **/
+            static bool is_finite(const DList & self) noexcept;
+            /** return element @p index of this sequence **/
+            static obj<AGCObject> at(const DList & self, size_type index);
+
+            ///@}
+        };
+
+    } /*namespace scm*/
+} /*namespace xo*/
+
+/* end */

xo-object2/src/object2/CMakeLists.txt

@@ -6,9 +6,12 @@ set(SELF_SRCS
     IGCObject_DInteger.cpp
     IGCObject_DList.cpp
     ISequence_Any.cpp
+    ISequence_DList.cpp
+    DList.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_gc)
 #xo_dependency(${SELF_LIB} indentlog)
+#add_dependencies(${SELF_LIB} xo-object2-facetimpl-sequence-list)

xo-object2/src/object2/DList.cpp

@@ -0,0 +1,54 @@
+/** @file DList.cpp
+ *
+ *  @author Roland Conybeare, Dec 2025
+ **/
+
+#include "DList.hpp"
+#include <xo/indentlog/print/tag.hpp>
+
+namespace xo {
+    namespace scm {
+        auto
+        DList::size() const noexcept -> size_type
+        {
+            const DList * l = this;
+
+            size_type z = 0;
+
+            while (l) {
+                ++z;
+                l = l->rest_;
+            }
+
+            return z;
+        }
+
+        auto
+        DList::at(size_type index) const -> obj<AGCObject>
+        {
+            size_type ix = index;
+            const DList * l = this;
+
+            while (l->rest_ && (ix > 0)) {
+                --ix;
+                l = l->rest_;
+            }
+
+            if (ix > 0) {
+                assert(l == nullptr);
+
+                throw std::runtime_error
+                    (tostr("DList::at: out-of-range index where [0..z) expected",
+                           xtag("index", index),
+                           xtag("z", this->size())));
+            }
+
+            assert(l);
+
+            return l->head_;
+        }
+
+    } /*namespace scm*/
+} /*namespace xo*/
+
+/* end DList.cpp */

xo-object2/src/object2/IGCObject_DList.cpp

@@ -6,7 +6,9 @@
 #include "IGCObject_DList.hpp"
 
 namespace xo {
+    using xo::mm::AGCObject;
     using xo::mm::AAllocator;
+    using xo::facet::with_facet;
     using xo::facet::obj;
     using std::size_t;
 
@@ -33,8 +35,11 @@ namespace xo {
         IGCObject_DList::forward_children(DList & src,
                                           obj<ACollector> gc) noexcept
         {
-            gc.forward_inplace(&src.head_);
+            gc.forward_inplace(src.head_.iface(), (void **)&(src.head_.data_));
-            gc.forward_inplace(&src.rest_);
+
+            //auto rest = with_facet<AGCObject>::mkobj(src.rest_);
+            xo::facet::FacetImplementation<xo::mm::AGCObject, DList>::ImplType iface;
+            gc.forward_inplace(&iface, (void **)(&src.rest_));
 
             return shallow_size(src);
         }

xo-object2/src/object2/ISequence_DList.cpp

@@ -0,0 +1,40 @@
+/** @file ISequence_DList.cpp
+ *
+ *  Generated automagically from ingredients:
+ *  1. code generator:
+ *       [/Users/roland/proj/xo-umbrella2/xo-facet/codegen/genfacet]
+ *     arguments:
+ *       --input [idl/ISequence_DList.json5]
+ *  2. jinja2 template for abstract facet .hpp file:
+ *       [iface_facet_any.hpp.j2]
+ *  3. idl for facet methods
+ *       [idl/ISequence_DList.json5]
+**/
+
+#include "ISequence_DList.hpp"
+
+namespace xo {
+    namespace scm {
+        auto
+        ISequence_DList::is_empty(const DList & self) noexcept -> bool
+        {
+            return self.is_empty();
+        }
+
+        auto
+        ISequence_DList::is_finite(const DList & self) noexcept -> bool
+        {
+            return self.is_finite();
+        }
+
+        auto
+        ISequence_DList::at(const DList & self, size_type index) -> obj<AGCObject>
+        {
+            return self.at(index);
+        }
+
+
+    } /*namespace scm*/
+} /*namespace xo*/
+
+/* end ISequence_DList.cpp */