xo-interpreter2 stack: work on runtime error representation [WIP]

xo-interpreter2/include/xo/interpreter2/VirtualSchematikaMachine.hpp

@@ -10,6 +10,7 @@
 #include "VsmFrame.hpp"
 #include "DLocalEnv.hpp"
 #include "DGlobalEnv.hpp"
+#include <xo/object2/RuntimeError.hpp>
 #include <xo/reader2/SchematikaReader.hpp>
 #include <xo/expression2/Expression.hpp>
 #include <xo/gc/GCObject.hpp>
@@ -17,6 +18,10 @@
 
 namespace xo {
     namespace scm {
+#ifdef OBSOLETE // see DVsmError
+        // TODO: move error to collected space?
+        //       or special arena?
+        // 
         struct EvaluationError {
             /** source location (in vsm implementation) at which error identified **/
             std::string_view src_function_;
@@ -24,6 +29,7 @@ namespace xo {
             std::string_view error_description_;
             // TODO: info about location in schematika source
         };
+#endif
 
         /** similar to @ref xo::scm::ReaderResult **/
         struct VsmResult {
@@ -31,17 +37,17 @@ namespace xo {
             using span_type = xo::mm::span<const char>;
 
             VsmResult() = default;
-            VsmResult(obj<AGCObject> value) : result_{value} {}
+            explicit VsmResult(obj<AGCObject> value) : result_{value} {}
-            VsmResult(TokenizerError err) : result_{err} {}
+            explicit VsmResult(TokenizerError err) : result_{err} {}
 
             bool is_value() const { return std::holds_alternative<obj<AGCObject>>(result_); }
             bool is_tk_error() const { return std::holds_alternative<TokenizerError>(result_); }
-            bool is_eval_error() const { return std::holds_alternative<EvaluationError>(result_); }
+            bool is_eval_error() const;
 
             const obj<AGCObject> * value() const { return std::get_if<obj<AGCObject>>(&result_); }
 
             /** result of evaluating first expression encountered in input **/
-            std::variant<obj<AGCObject>, TokenizerError, EvaluationError> result_;
+            std::variant<obj<AGCObject>, TokenizerError> result_;
         };
 
         /** vsm result + reamining span **/
@@ -72,6 +78,8 @@ namespace xo {
 
             /** allocator for schematika data **/
             obj<AAllocator> allocator() const noexcept;
+            /** allocator for runtime errors **/
+            obj<AAllocator> error_allocator() const noexcept;
 
             /** visit vsm-owned memory pools; call visitor(info) for each **/
             void visit_pools(const MemorySizeVisitor & visitor) const;
@@ -185,11 +193,19 @@ namespace xo {
             /** configuration **/
             VsmConfig config_;
 
-            /** allocator (likely collector) for
+            /** allocator (likely DX1Collector or similar) for
              *  expressions and values
              **/
             box<AAllocator> mm_;
 
+            /** Sidecar allocator for error reporting.
+             *  Separate to mitigate interference with @ref mm_
+             *  (separate memory so we can for example report 
+             *   an out-of-memory error).
+             *  Likely DArena or similar
+             **/
+            box<AAllocator> error_mm_;
+
             /** runtime context for this vsm.
              *  For example, provides allocator to primitives
              **/

xo-interpreter2/include/xo/interpreter2/VsmConfig.hpp

@@ -7,6 +7,7 @@
 
 #include <xo/reader2/ReaderConfig.hpp>
 #include <xo/gc/X1CollectorConfig.hpp>
+#include <xo/arena/ArenaConfig.hpp>
 
 namespace xo {
     namespace scm {
@@ -14,6 +15,7 @@ namespace xo {
          **/
         struct VsmConfig {
             using X1CollectorConfig = xo::mm::X1CollectorConfig;
+            using ArenaConfig = xo::mm::ArenaConfig;
 
             VsmConfig() = default;
 
@@ -26,6 +28,10 @@ namespace xo {
              *  TODO: may want to make CollectorConfig polymorphic
              **/
             X1CollectorConfig x1_config_ = X1CollectorConfig().with_size(4*1024*1024);
+            /** Configuration for error allocator
+             *  TODO: may want to make ArenaConfig polymorphic
+             **/
+            ArenaConfig error_config_ = ArenaConfig().with_size(64*1024);
         };
     } /*namespace scm*/
 } /*namespace xo*/

xo-interpreter2/src/interpreter2/DClosure.cpp

@@ -6,6 +6,8 @@
 #include "Closure.hpp"
 #include "LambdaExpr.hpp"
 #include "LocalEnv.hpp"
+#include "VsmRcx.hpp"
+#include <xo/indentlog/scope.hpp>
 #include <cstddef>
 
 namespace xo {
@@ -33,7 +35,30 @@ namespace xo {
         DClosure::apply_nocheck(obj<ARuntimeContext> rcx,
                                 const DArray * args)
         {
-            (void)rcx;
+            scope log(XO_DEBUG(true));
+
+            auto vsm_rcx
+                = obj<ARuntimeContext,DVsmRcx>::from(rcx);
+
+            log && log(xtag("vsm_rcx.data", (void*)vsm_rcx.data()));
+
+            // let's try a not-implemented error
+
+            // don't want to clutter Procedure facet, since it's
+            // lower-level than xo-interpreter2
+
+#ifdef NOT_YET
+            // TODO: verify arguments against type signature.
+            //       unless we have evidence that program is type correct
+
+            int32_t n_args = this->n_args();
+
+            if (n_args != args->size()) {
+                // 
+            }
+#endif
+
+
             (void)args;
 
             assert(false);

xo-interpreter2/src/interpreter2/VirtualSchematikaMachine.cpp

@@ -15,6 +15,7 @@
 //#include <xo/procedure2/SimpleRcx.hpp>
 #include <xo/gc/DX1Collector.hpp>
 #include <xo/gc/detail/IAllocator_DX1Collector.hpp>
+#include <xo/alloc2/Arena.hpp>
 #include <xo/printable2/Printable.hpp>
 #include <xo/facet/FacetRegistry.hpp>
 #include <cassert>
@@ -27,12 +28,25 @@ namespace xo {
     //using xo::mm::MemorySizeInfo;  // not used yet
     using xo::mm::AAllocator;
     using xo::mm::DX1Collector;
+    using xo::mm::DArena;
     using xo::facet::FacetRegistry;
     using std::cout;
 
     namespace scm {
 
-        // NOTE: using heap here for {DX1Collector, DVsmRcx} instances
+        bool
+        VsmResult::is_eval_error() const
+        {
+            if (std::holds_alternative<obj<AGCObject>>(result_)) {
+                auto err = obj<AGCObject,DRuntimeError>::from(*(this->value()));
+
+                return err;
+            } else {
+                return false;
+            }
+        }
+
+        // NOTE: using heap here for {DX1Collector, DArena, DVsmRcx} instances
         //       (though DX1Collector allocations will be from explictly mmap'd memory)
         //
         VirtualSchematikaMachine::VirtualSchematikaMachine(const VsmConfig & config)
@@ -41,6 +55,14 @@ namespace xo {
           rcx_(box<ARuntimeContext,DVsmRcx>(new DVsmRcx(this))),
           reader_{config.rdr_config_, mm_.to_op()}
         {
+            {
+                DArena * arena = new DArena();
+                assert(arena);
+                *arena = DArena::map(config_.error_config_);
+
+                error_mm_.adopt(obj<AAllocator,DArena>(arena));
+            }
+                
             // TODO: allocate global_env
         }
 
@@ -50,6 +72,12 @@ namespace xo {
             return mm_.to_op();
         }
 
+        obj<AAllocator>
+        VirtualSchematikaMachine::error_allocator() const noexcept
+        {
+            return error_mm_.to_op();
+        }
+
         void
         VirtualSchematikaMachine::visit_pools(const MemorySizeVisitor & visitor) const
         {
@@ -113,7 +141,7 @@ namespace xo {
         {
             this->pc_ = VsmInstr::c_eval;
             this->expr_ = expr;
-            this->value_ = obj<AGCObject>();
+            this->value_ = VsmResult(obj<AGCObject>());
             this->cont_ = VsmInstr::c_halt;
 
             this->run();
@@ -200,7 +228,7 @@ namespace xo {
             auto expr
                 = obj<AExpression,DConstant>::from(expr_);
 
-            this->value_ = expr.data()->value();
+            this->value_ = VsmResult(expr.data()->value());
             this->pc_ = this->cont_;
         }
 
@@ -250,7 +278,7 @@ namespace xo {
                                                 local_env_);
 
             this->value_
-                = obj<AGCObject>(obj<AGCObject,DClosure>(closure));
+                = VsmResult(obj<AGCObject>(obj<AGCObject,DClosure>(closure)));
             this->pc_ = this->cont_;
         }
 
@@ -341,7 +369,7 @@ namespace xo {
 
             // TODO: check argument types
 
-            this->value_ = fn_.apply_nocheck(rcx_.to_op(), args_);
+            this->value_ = VsmResult(fn_.apply_nocheck(rcx_.to_op(), args_));
             this->pc_ = cont_;
 
             return;

xo-interpreter2/utest/VirtualSchematikaMachine.test.cpp

@@ -225,7 +225,6 @@ namespace xo {
             vsm.visit_pools(visitor);
         }
 
-#ifdef NOT_YET
         TEST_CASE("VirtualSchematikaMachine-apply2", "[interpreter2][VSM]")
         {
             scope log(XO_DEBUG(true));
@@ -265,7 +264,6 @@ namespace xo {
             FacetRegistry::instance().visit_pools(visitor);
             vsm.visit_pools(visitor);
         }
-#endif
     } /*namespace ut*/
 } /*namespace xo*/
 

xo-object2/CMakeLists.txt

@@ -208,6 +208,34 @@ xo_add_genfacetimpl(
     OUTPUT_CPP_DIR src/object2
 )
 
+# ----------------------------------------------------------------
+
+# note: manual target; generated code committed to git
+xo_add_genfacetimpl(
+    TARGET xo-object2-facetimpl-printable-runtimeerror
+    FACET_PKG xo_printable2
+    FACET Printable
+    REPR RuntimeError
+    INPUT idl/IPrintable_DRuntimeError.json5
+    OUTPUT_HPP_DIR include/xo/object2
+    OUTPUT_IMPL_SUBDIR error
+    OUTPUT_CPP_DIR src/object2
+)
+
+# note: manual target; generated code committed to git
+xo_add_genfacetimpl(
+    TARGET xo-object2-facetimpl-gcobject-runtimeerror
+    FACET_PKG xo_gc
+    FACET GCObject
+    REPR RuntimeError
+    INPUT idl/IGCObject_DRuntimeError.json5
+    OUTPUT_HPP_DIR include/xo/object2
+    OUTPUT_IMPL_SUBDIR error
+    OUTPUT_CPP_DIR src/object2
+)
+
+# ----------------------------------------------------------------
+
 xo_add_genfacet_all(xo-object2-genfacet-all)
 
 # ----------------------------------------------------------------

xo-object2/idl/IGCObject_DRuntimeError.json5

@@ -0,0 +1,15 @@
+{
+    mode: "implementation",
+    includes: [
+//        "<xo/gc/GCObject.hpp>",
+//        "<xo/alloc2/Allocator.hpp>"
+    ],
+    local_types: [ ],
+    namespace1: "xo",
+    namespace2: "scm",
+    facet_idl: "idl/GCObject.json5",
+    brief: "provide AGCObject interface for DRuntimeError",
+    using_doxygen: true,
+    repr: "DRuntimeError",
+    doc: [ "implement AGCObject for DRuntimeError" ],
+}

xo-object2/idl/IPrintable_DRuntimeError.json5

@@ -0,0 +1,13 @@
+{
+    mode: "implementation",
+    includes: [ "<xo/printable2/Printable.hpp>",
+                "<xo/printable2/detail/IPrintable_Xfer.hpp>" ],
+    local_types: [ ],
+    namespace1: "xo",
+    namespace2: "scm",
+    facet_idl: "idl/Printable.json5",
+    brief: "provide APrintable interface for DRuntimeError",
+    using_doxygen: true,
+    repr: "DRuntimeError",
+    doc: [ "implement APrintable for DRuntimeError" ],
+}

xo-object2/include/xo/object2/DRuntimeError.hpp

@@ -0,0 +1,61 @@
+/** @file DRuntimeError.hpp
+ *
+ *  @author Roland Conybeare, Feb 2026
+ **/
+
+#pragma once
+
+#include "String.hpp"
+#include <xo/alloc2/Allocator.hpp>
+
+namespace xo {
+    namespace scm {
+
+        /** @brief representation for runtime errors
+         **/
+        class DRuntimeError {
+        public:
+            using ACollector = xo::mm::ACollector;
+            using AAllocator = xo::mm::AAllocator;
+            using ppindentinfo = xo::print::ppindentinfo;
+
+        public:
+            /** create instance using memory from allocator @p mm
+             *  @p src_fn identifies the (c++) function/method in which
+             *  error detercted.
+             *  @p error_descr contains human-readable error message;
+             *  will be copied by this function.
+             **/
+            DRuntimeError * _make(obj<AAllocator> mm,
+                                  DString * src_fn,
+                                  DString * error_descr);
+
+            /** @defgroup scm-runtimeerror-printable-facet printable facet **/
+            ///@{
+            
+            bool pretty(const ppindentinfo & ppii) const;
+
+            ///@}
+            /** @defgroup scm-runtimeerror-gcobject-facet gcobject facet **/
+            ///@{
+
+            std::size_t shallow_size() const noexcept;
+            DRuntimeError * shallow_copy(obj<AAllocator> mm) const noexcept;
+            std::size_t forward_children(obj<ACollector> gc) noexcept;
+
+            ///@}
+
+        private:
+            DRuntimeError(DString * src_fn, DString * error_descr);
+
+        private:
+            /** source location at which error identified **/
+            DString * src_function_ = nullptr;
+            /** error description (allocated from ErrorArena) **/
+            DString * error_descr_ = nullptr;
+        };
+
+    } /*namespace scm*/
+} /*namespace xo*/
+
+/* end DRuntimeError.hpp */

xo-object2/include/xo/object2/RuntimeError.hpp

@@ -0,0 +1,12 @@
+/** @file RuntimeError.hpp
+ *
+ *  @author Roland Conybeare, Feb 2026
+ **/
+
+#pragma once
+
+#include "DRuntimeError.hpp"
+#include "error/IGCObject_DRuntimeError.hpp"
+#include "error/IPrintable_DRuntimeError.hpp"
+
+/* end RuntimeError.hpp */

xo-object2/include/xo/object2/error/IGCObject_DRuntimeError.hpp

@@ -0,0 +1,65 @@
+/** @file IGCObject_DRuntimeError.hpp
+ *
+ *  Generated automagically from ingredients:
+ *  1. code generator:
+ *       [xo-facet/codegen/genfacet]
+ *     arguments:
+ *       --input [idl/IGCObject_DRuntimeError.json5]
+ *  2. jinja2 template for abstract facet .hpp file:
+ *       [iface_facet_repr.hpp.j2]
+ *  3. idl for facet methods
+ *       [idl/IGCObject_DRuntimeError.json5]
+ **/
+
+#pragma once
+
+#include "GCObject.hpp"
+#include "DRuntimeError.hpp"
+
+namespace xo { namespace scm { class IGCObject_DRuntimeError; } }
+
+namespace xo {
+    namespace facet {
+        template <>
+        struct FacetImplementation<xo::mm::AGCObject,
+                                   xo::scm::DRuntimeError>
+        {
+            using ImplType = xo::mm::IGCObject_Xfer
+              <xo::scm::DRuntimeError,
+               xo::scm::IGCObject_DRuntimeError>;
+        };
+    }
+}
+
+namespace xo {
+    namespace scm {
+        /** @class IGCObject_DRuntimeError
+         **/
+        class IGCObject_DRuntimeError {
+        public:
+            /** @defgroup scm-gcobject-druntimeerror-type-traits **/
+            ///@{
+            using size_type = xo::mm::AGCObject::size_type;
+            using AAllocator = xo::mm::AGCObject::AAllocator;
+            using ACollector = xo::mm::AGCObject::ACollector;
+            using Copaque = xo::mm::AGCObject::Copaque;
+            using Opaque = xo::mm::AGCObject::Opaque;
+            ///@}
+            /** @defgroup scm-gcobject-druntimeerror-methods **/
+            ///@{
+            // const methods
+            /** memory consumption for this instance **/
+            static size_type shallow_size(const DRuntimeError & self) noexcept;
+            /** copy instance using allocator **/
+            static Opaque shallow_copy(const DRuntimeError & self, obj<AAllocator> mm) noexcept;
+
+            // non-const methods
+            /** during GC: forward immdiate children **/
+            static size_type forward_children(DRuntimeError & self, obj<ACollector> gc) noexcept;
+            ///@}
+        };
+
+    } /*namespace scm*/
+} /*namespace xo*/
+
+/* end */

xo-object2/include/xo/object2/error/IPrintable_DRuntimeError.hpp

@@ -0,0 +1,62 @@
+/** @file IPrintable_DRuntimeError.hpp
+ *
+ *  Generated automagically from ingredients:
+ *  1. code generator:
+ *       [xo-facet/codegen/genfacet]
+ *     arguments:
+ *       --input [idl/IPrintable_DRuntimeError.json5]
+ *  2. jinja2 template for abstract facet .hpp file:
+ *       [iface_facet_repr.hpp.j2]
+ *  3. idl for facet methods
+ *       [idl/IPrintable_DRuntimeError.json5]
+ **/
+
+#pragma once
+
+#include "Printable.hpp"
+#include <xo/printable2/Printable.hpp>
+#include <xo/printable2/detail/IPrintable_Xfer.hpp>
+#include "DRuntimeError.hpp"
+
+namespace xo { namespace scm { class IPrintable_DRuntimeError; } }
+
+namespace xo {
+    namespace facet {
+        template <>
+        struct FacetImplementation<xo::print::APrintable,
+                                   xo::scm::DRuntimeError>
+        {
+            using ImplType = xo::print::IPrintable_Xfer
+              <xo::scm::DRuntimeError,
+               xo::scm::IPrintable_DRuntimeError>;
+        };
+    }
+}
+
+namespace xo {
+    namespace scm {
+        /** @class IPrintable_DRuntimeError
+         **/
+        class IPrintable_DRuntimeError {
+        public:
+            /** @defgroup scm-printable-druntimeerror-type-traits **/
+            ///@{
+            using ppindentinfo = xo::print::APrintable::ppindentinfo;
+            using Copaque = xo::print::APrintable::Copaque;
+            using Opaque = xo::print::APrintable::Opaque;
+            ///@}
+            /** @defgroup scm-printable-druntimeerror-methods **/
+            ///@{
+            // const methods
+            /** Pretty-printing support for this object.
+See [xo-indentlog/xo/indentlog/pretty.hpp] **/
+            static bool pretty(const DRuntimeError & self, const ppindentinfo & ppii);
+
+            // non-const methods
+            ///@}
+        };
+
+    } /*namespace scm*/
+} /*namespace xo*/
+
+/* end */

xo-object2/src/object2/CMakeLists.txt

@@ -5,29 +5,41 @@ set(SELF_SRCS
     init_object2.cpp
     object2_register_types.cpp
     object2_register_facets.cpp
+
     GCObjectConversion_DFloat.cpp
     GCObjectConversion_DInteger.cpp
-    IGCObject_DArray.cpp
+
-    IGCObject_DFloat.cpp
-    IGCObject_DBoolean.cpp
-    IGCObject_DInteger.cpp
-    IGCObject_DList.cpp
-    IGCObject_DString.cpp
     ISequence_Any.cpp
-    ISequence_DArray.cpp
+
-    ISequence_DList.cpp
-    IPrintable_DArray.cpp
-    IPrintable_DList.cpp
-    IPrintable_DBoolean.cpp
-    IPrintable_DFloat.cpp
-    IPrintable_DInteger.cpp
-    IPrintable_DString.cpp
     DArray.cpp
+    ISequence_DArray.cpp
+    IGCObject_DArray.cpp
+    IPrintable_DArray.cpp
+
     DList.cpp
+    ISequence_DList.cpp
+    IGCObject_DList.cpp
+    IPrintable_DList.cpp
+
     DFloat.cpp
+    IGCObject_DFloat.cpp
+    IPrintable_DFloat.cpp
+
     DInteger.cpp
+    IGCObject_DInteger.cpp
+    IPrintable_DInteger.cpp
+
     DBoolean.cpp
+    IGCObject_DBoolean.cpp
+    IPrintable_DBoolean.cpp
+
     DString.cpp
+    IGCObject_DString.cpp
+    IPrintable_DString.cpp
+
+    DRuntimeError.cpp
+    IGCObject_DRuntimeError.cpp
+    IPrintable_DRuntimeError.cpp
     )
 
 xo_add_shared_library4(${SELF_LIB} ${PROJECT_NAME}Targets ${PROJECT_VERSION} 1 ${SELF_SRCS})

xo-object2/src/object2/DList.cpp

@@ -148,6 +148,8 @@ namespace xo {
             }
         }
 
+        // ----- GCObject facet ------
+
         auto
         DList::shallow_size() const noexcept -> size_type
         {
@@ -175,7 +177,7 @@ namespace xo {
             auto iface = xo::facet::impl_for<AGCObject,DList>();
             gc.forward_inplace(&iface, (void **)(&rest_));
 
-            return shallow_size();
+            return this->shallow_size();
         }
     } /*namespace scm*/
 } /*namespace xo*/

xo-object2/src/object2/DRuntimeError.cpp

@@ -0,0 +1,82 @@
+/** @file DRuntimeError.cpp
+*
+ *  @author Roland Conybeare, Feb 2026
+ **/
+
+#include "DRuntimeError.hpp"
+
+namespace xo {
+    using xo::mm::AGCObject;
+    using xo::facet::typeseq;
+
+    namespace scm {
+
+        DRuntimeError *
+        DRuntimeError::_make(obj<AAllocator> mm,
+                             DString * src_fn,
+                             DString * error_descr)
+        {
+            void * mem
+                = mm.alloc(typeseq::id<DRuntimeError>(),
+                           sizeof(DRuntimeError));
+
+            DRuntimeError * err
+                = new (mem) DRuntimeError(src_fn, error_descr);
+
+            return err;
+        }
+
+        DRuntimeError::DRuntimeError(DString * src_fn,
+                                     DString * error_descr) : src_function_{src_fn},
+                                                              error_descr_{error_descr}
+        {}
+
+        // ----- GCObject facet -----
+
+        std::size_t
+        DRuntimeError::shallow_size() const noexcept
+        {
+            return sizeof(DRuntimeError);
+        }
+
+        DRuntimeError *
+        DRuntimeError::shallow_copy(obj<AAllocator> mm) const noexcept
+        {
+            DRuntimeError * copy = (DRuntimeError *)mm.alloc_copy((std::byte *)this);
+
+            if (copy)
+                *copy = *this;
+
+            return copy;
+        }
+
+        std::size_t
+        DRuntimeError::forward_children(obj<ACollector> gc) noexcept
+        {
+            {
+                auto iface = xo::facet::impl_for<AGCObject,DString>();
+                gc.forward_inplace(&iface, (void **)(&src_function_));
+            }
+
+            {
+                auto iface = xo::facet::impl_for<AGCObject,DString>();
+                gc.forward_inplace(&iface, (void **)(&error_descr_));
+            }
+
+            return this->shallow_size();
+        }
+
+        // ----- Printable facet -----
+
+        bool
+        DRuntimeError::pretty(const ppindentinfo & ppii) const
+        {
+            return ppii.pps()->pretty_struct(ppii,
+                                             "DRuntimeError");
+        }
+
+    } /*namespace scm*/
+} /*namespace xo*/
+
+/* end DRuntimeError.cpp */
+

xo-object2/src/object2/IGCObject_DRuntimeError.cpp

@@ -0,0 +1,39 @@
+/** @file IGCObject_DRuntimeError.cpp
+ *
+ *  Generated automagically from ingredients:
+ *  1. code generator:
+ *       [xo-facet/codegen/genfacet]
+ *     arguments:
+ *       --input [idl/IGCObject_DRuntimeError.json5]
+ *  2. jinja2 template for abstract facet .hpp file:
+ *       [iface_facet_any.hpp.j2]
+ *  3. idl for facet methods
+ *       [idl/IGCObject_DRuntimeError.json5]
+**/
+
+#include "error/IGCObject_DRuntimeError.hpp"
+
+namespace xo {
+    namespace scm {
+        auto
+        IGCObject_DRuntimeError::shallow_size(const DRuntimeError & self) noexcept -> size_type
+        {
+            return self.shallow_size();
+        }
+
+        auto
+        IGCObject_DRuntimeError::shallow_copy(const DRuntimeError & self, obj<AAllocator> mm) noexcept -> Opaque
+        {
+            return self.shallow_copy(mm);
+        }
+
+        auto
+        IGCObject_DRuntimeError::forward_children(DRuntimeError & self, obj<ACollector> gc) noexcept -> size_type
+        {
+            return self.forward_children(gc);
+        }
+
+    } /*namespace scm*/
+} /*namespace xo*/
+
+/* end IGCObject_DRuntimeError.cpp */

xo-object2/src/object2/IPrintable_DRuntimeError.cpp

@@ -0,0 +1,28 @@
+/** @file IPrintable_DRuntimeError.cpp
+ *
+ *  Generated automagically from ingredients:
+ *  1. code generator:
+ *       [xo-facet/codegen/genfacet]
+ *     arguments:
+ *       --input [idl/IPrintable_DRuntimeError.json5]
+ *  2. jinja2 template for abstract facet .hpp file:
+ *       [iface_facet_any.hpp.j2]
+ *  3. idl for facet methods
+ *       [idl/IPrintable_DRuntimeError.json5]
+**/
+
+#include "error/IPrintable_DRuntimeError.hpp"
+
+namespace xo {
+    namespace scm {
+        auto
+        IPrintable_DRuntimeError::pretty(const DRuntimeError & self, const ppindentinfo & ppii) -> bool
+        {
+            return self.pretty(ppii);
+        }
+
+
+    } /*namespace scm*/
+} /*namespace xo*/
+
+/* end IPrintable_DRuntimeError.cpp */

xo-object2/src/object2/object2_register_facets.cpp

@@ -4,6 +4,7 @@
  **/
 
 #include "object2_register_facets.hpp"
+#include "RuntimeError.hpp"
 
 #include <xo/object2/array/IGCObject_DArray.hpp>
 #include <xo/object2/list/IGCObject_DList.hpp>
@@ -66,6 +67,9 @@ namespace xo {
             FacetRegistry::register_impl<APrintable, DArray>();
             FacetRegistry::register_impl<ASequence, DArray>();
 
+            FacetRegistry::register_impl<AGCObject, DRuntimeError>();
+            FacetRegistry::register_impl<APrintable, DRuntimeError>();
+
             log && log(xtag("DVariantPlaceholder.tseq", typeseq::id<DVariantPlaceholder>()));
 
             log && log(xtag("DList.tseq", typeseq::id<DList>()));
@@ -74,6 +78,7 @@ namespace xo {
             log && log(xtag("DInteger.tseq", typeseq::id<DInteger>()));
             log && log(xtag("DString.tseq", typeseq::id<DString>()));
             log && log(xtag("DArray.tseq", typeseq::id<DArray>()));
+            log && log(xtag("DRuntimeError.tseq", typeseq::id<DRuntimeError>()));
 
             log && log(xtag("AAllocator.tseq", typeseq::id<AAllocator>()));
             log && log(xtag("APrintable.tseq", typeseq::id<APrintable>()));