xo-gc stack: + request-gc-statistics() primitive

1. xo-gc now depends on xo-object2.
2. use genfacet for ICollector_DX1Collector
3. moves xo-gc utest previously in xo-object2 to more natural
   location in xo-gc/

idl/RuntimeContext.json5

@@ -61,6 +61,15 @@
             noexcept: true,
             attributes: [],
         },
+        {
+            name: "error_allocator",
+            doc: [ "last-resort allocator for erros. e.g. regular allocator exhausted" ],
+            return_type: "obj<AAllocator>",
+            args: [],
+            const: true,
+            noexcept: true,
+            attributes: [],
+        },
         {
             name: "stringtable",
             doc: [ "stringtable for unique symbols" ],

include/xo/procedure2/DSimpleRcx.hpp

@@ -23,16 +23,19 @@ namespace xo {
             using MemorySizeVisitor = xo::mm::MemorySizeVisitor;
 
         public:
-            DSimpleRcx(obj<AAllocator> mm, StringTable * st)
+            DSimpleRcx(obj<AAllocator> mm, obj<AAllocator> error_mm, StringTable * st)
-            : allocator_{mm}, stringtable_{st} {}
+            : allocator_{mm}, error_allocator_{error_mm},
+              stringtable_{st} {}
 
             obj<AAllocator> allocator() const noexcept { return allocator_; }
             obj<ACollector> collector() const noexcept;
+            obj<AAllocator> error_allocator() const noexcept { return error_allocator_; }
             StringTable * stringtable() const noexcept { return stringtable_; }
             void visit_pools(const MemorySizeVisitor & visitor) const;
 
         private:
             obj<AAllocator> allocator_;
+            obj<AAllocator> error_allocator_;
             StringTable * stringtable_ = nullptr;
         };
 

include/xo/procedure2/GcPrimitives.hpp

@@ -5,6 +5,7 @@
 
 #pragma once
 
+#include "Primitive_gco_0.hpp"
 #include "Primitive_gco_1_gco.hpp"
 
 namespace xo {
@@ -18,6 +19,10 @@ namespace xo {
             using AAllocator = xo::mm::AAllocator;
 
         public:
+            /** create primitive: report gc statistics **/
+            static DPrimitive_gco_0 * make_report_gc_statistics_pm(obj<AAllocator> mm,
+                                                                   StringTable * stbl);
+
             /** create primitive: request collection **/
             static DPrimitive_gco_1_gco * make_request_gc_pm(obj<AAllocator> mm,
                                                              StringTable * stbl);

include/xo/procedure2/detail/AProcedure.hpp

@@ -47,6 +47,11 @@ public:
     /** @defgroup scm-procedure-methods **/
     ///@{
     // const methods
+    /** An uninitialized AProcedure 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 **/

include/xo/procedure2/detail/ARuntimeContext.hpp

@@ -51,6 +51,11 @@ public:
     /** @defgroup scm-runtimecontext-methods **/
     ///@{
     // const methods
+    /** An uninitialized ARuntimeContext 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 **/
@@ -59,6 +64,8 @@ public:
     virtual obj<AAllocator> allocator(Copaque data)  const  noexcept = 0;
     /** collector facet for allocator. If non-null, same data pointer as allocator **/
     virtual obj<ACollector> collector(Copaque data)  const  noexcept = 0;
+    /** last-resort allocator for erros. e.g. regular allocator exhausted **/
+    virtual obj<AAllocator> error_allocator(Copaque data)  const  noexcept = 0;
     /** stringtable for unique symbols **/
     virtual StringTable * stringtable(Copaque data)  const  noexcept = 0;
     /** invoke visitor for each distinct memory pool **/

include/xo/procedure2/detail/IRuntimeContext_Any.hpp

@@ -63,6 +63,7 @@ namespace scm {
         // const methods
         [[noreturn]] obj<AAllocator> allocator(Copaque)  const  noexcept override { _fatal(); }
         [[noreturn]] obj<ACollector> collector(Copaque)  const  noexcept override { _fatal(); }
+        [[noreturn]] obj<AAllocator> error_allocator(Copaque)  const  noexcept override { _fatal(); }
         [[noreturn]] StringTable * stringtable(Copaque)  const  noexcept override { _fatal(); }
         [[noreturn]] void visit_pools(Copaque, MemorySizeVisitor)  const override { _fatal(); }
 

include/xo/procedure2/detail/IRuntimeContext_DSimpleRcx.hpp

@@ -52,6 +52,8 @@ namespace xo {
             static obj<AAllocator> allocator(const DSimpleRcx & self) noexcept;
             /** collector facet for allocator. If non-null, same data pointer as allocator **/
             static obj<ACollector> collector(const DSimpleRcx & self) noexcept;
+            /** last-resort allocator for erros. e.g. regular allocator exhausted **/
+            static obj<AAllocator> error_allocator(const DSimpleRcx & self) noexcept;
             /** stringtable for unique symbols **/
             static StringTable * stringtable(const DSimpleRcx & self) noexcept;
             /** invoke visitor for each distinct memory pool **/

include/xo/procedure2/detail/IRuntimeContext_Xfer.hpp

@@ -54,6 +54,9 @@ namespace scm {
         obj<ACollector> collector(Copaque data)  const  noexcept override {
             return I::collector(_dcast(data));
         }
+        obj<AAllocator> error_allocator(Copaque data)  const  noexcept override {
+            return I::error_allocator(_dcast(data));
+        }
         StringTable * stringtable(Copaque data)  const  noexcept override {
             return I::stringtable(_dcast(data));
         }

include/xo/procedure2/detail/RRuntimeContext.hpp

@@ -61,6 +61,9 @@ public:
     obj<ACollector> collector()  const  noexcept {
         return O::iface()->collector(O::data());
     }
+    obj<AAllocator> error_allocator()  const  noexcept {
+        return O::iface()->error_allocator(O::data());
+    }
     StringTable * stringtable()  const  noexcept {
         return O::iface()->stringtable(O::data());
     }

src/procedure2/GcPrimitives.cpp

@@ -21,23 +21,35 @@ namespace xo {
 
         // ----- report-gc-status -----
 
-#ifdef NOT_YET
         obj<AGCObject>
-        xfer_report_gc_status(obj<ARuntimeContext> rcx)
+        xfer_report_gc_statistics(obj<ARuntimeContext> rcx)
         {
-            bool have_gc = false;
-
             if (rcx.collector()) {
                 // status currently only implemented for X1 collector
 
-                auto gc = obj<ACollector,DX1Collector>::from(rcx.collector());
+                obj<AGCObject> stats;
-
+                bool ok = rcx.collector().report_statistics(rcx.allocator(),
+                                                            rcx.error_allocator(),
+                                                            &stats);
 
+                if (ok && stats)
+                    return stats;
             }
 
             return DBoolean::box(rcx.allocator(), false);
         }
-#endif
+
+        DPrimitive_gco_0 *
+        GcPrimitives::make_report_gc_statistics_pm(obj<AAllocator> mm,
+                                                   StringTable * stbl)
+        {
+            (void)stbl;
+
+            auto any_ty = DAtomicType::make(mm, Metatype::t_any());
+            auto pm_ty = obj<AType,DFunctionType>(DFunctionType::_make(mm, any_ty));
+
+            return DPrimitive_gco_0::_make(mm, "report-gc-statistics", pm_ty, &xfer_report_gc_statistics);
+        }
 
         // ----- request-gc -----
 

src/procedure2/SetupProcedure2.cpp

@@ -130,6 +130,13 @@ namespace xo {
                             ObjectPrimitives::make_fn_n_args_pm(mm, stbl),
                             flags & InstallFlags::f_generalpurpose));
 
+            // ----- gc primitives -----
+
+            ok = ok & (PrimitiveRegistry::install_aux
+                           (sink,
+                            GcPrimitives::make_report_gc_statistics_pm(mm, stbl),
+                            flags & InstallFlags::f_generalpurpose));
+
             ok = ok & (PrimitiveRegistry::install_aux
                            (sink,
                             GcPrimitives::make_request_gc_pm(mm, stbl),

src/procedure2/facet/IRuntimeContext_DSimpleRcx.cpp

@@ -27,6 +27,12 @@ namespace xo {
             return self.collector();
         }
 
+        auto
+        IRuntimeContext_DSimpleRcx::error_allocator(const DSimpleRcx & self) noexcept -> obj<AAllocator>
+        {
+            return self.error_allocator();
+        }
+
         auto
         IRuntimeContext_DSimpleRcx::stringtable(const DSimpleRcx & self) noexcept -> StringTable *
         {

utest/DSimpleRcx.test.cpp

@@ -39,7 +39,7 @@ namespace xo {
             auto stbl = StringTable(1024 /*hint_max_capacity*/,
                                     false /*!debug_flag*/);
 
-            DSimpleRcx rcx(alloc, &stbl);
+            DSimpleRcx rcx(alloc, alloc, &stbl);
 
             REQUIRE((void*)rcx.allocator().data() == (void*)alloc.data());
             REQUIRE(rcx.stringtable() == &stbl);
@@ -54,7 +54,7 @@ namespace xo {
             auto stbl = StringTable(1024 /*hint_max_capacity*/,
                                     false /*!debug_flag*/);
 
-            DSimpleRcx rcx(alloc, &stbl);
+            DSimpleRcx rcx(alloc, alloc, &stbl);
             obj<ARuntimeContext> rcx_obj = with_facet<ARuntimeContext>::mkobj(&rcx);
 
             // verify we can recover allocator from obj<ARuntimeContext>