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

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

src/reader2/DApplySsm.cpp

@@ -233,7 +233,7 @@ namespace xo {
                 assert(expr_gco);
 
                 obj<AAllocator,DArena> mm(&(p_psm->parser_alloc()));
-                auto gc = obj<AAllocator>(mm).try_to_facet<ACollector>();
+                //auto gc = obj<AAllocator>(mm).try_to_facet<ACollector>();
 
                 if (args_expr_v_->size() == args_expr_v_->capacity()) {
                     // need to expand .args_expr_v_ capacity.
@@ -243,14 +243,14 @@ namespace xo {
                     DArray * argv_2x = DArray::_empty(mm, 2 * args_expr_v_->capacity());
 
                     for (DArray::size_type i = 0, n = args_expr_v_->size(); i < n; ++i) {
-                        argv_2x->push_back(gc, (*args_expr_v_)[i]);
+                        argv_2x->push_back(mm, (*args_expr_v_)[i]);
                     }
 
                     this->args_expr_v_ = argv_2x;
                 }
 
                 if (args_expr_v_->size() < args_expr_v_->capacity())
-                    args_expr_v_->push_back(gc, expr_gco);
+                    args_expr_v_->push_back(mm, expr_gco);
 
                 if (tk.tk_type() == tokentype::tk_rightparen) {
                     obj<AExpression> apply_ex = this->assemble_expr(p_psm->expr_alloc());

src/reader2/DExpectFormalArglistSsm.cpp

@@ -201,20 +201,20 @@ namespace xo {
                 obj<AAllocator,DArena> mm(&parser_alloc);
                 DArray * argl_2x = DArray::_empty(mm, 2 * argl_->capacity());
 
-                auto gc = obj<AAllocator>(mm).try_to_facet<ACollector>();
+                //auto gc = obj<AAllocator>(mm).try_to_facet<ACollector>();
 
                 for (DArray::size_type i = 0, n = argl_->size(); i < n; ++i) {
                     // TODO: prefer non-bounds-checked access here
-                    argl_2x->push_back(gc, argl_->at(i));
+                    argl_2x->push_back(mm, argl_->at(i));
                 }
 
                 // update in place
                 this->argl_ = argl_2x;
             }
 
-            auto gc = expr_alloc.try_to_facet<ACollector>();
+            //auto gc = expr_alloc.try_to_facet<ACollector>();
 
-            this->argl_->push_back(gc, var_o);
+            this->argl_->push_back(expr_alloc, var_o);
         }
 
         void

src/reader2/DExpectQArraySsm.cpp

@@ -178,7 +178,7 @@ namespace xo {
         DExpectQArraySsm::on_quoted_literal(obj<AGCObject> lit,
                                            ParserStateMachine * p_psm)
         {
-            auto gc = p_psm->expr_alloc().try_to_facet<ACollector>();
+            //auto gc = p_psm->expr_alloc().try_to_facet<ACollector>();
 
             if(state_.code() == QArrayXst::code::qarray_1a) {
                 // append lit at the end of array_
@@ -195,7 +195,7 @@ namespace xo {
                                                     2 * array_->capacity());
                     }
 
-                    bool ok = array_->push_back(gc, lit);
+                    bool ok = array_->push_back(p_psm->expr_alloc(), lit);
 
                     assert(ok);
                 }

src/reader2/DGlobalEnv.cpp

@@ -8,6 +8,7 @@
 #include <xo/object2/Array.hpp>
 
 namespace xo {
+    using xo::mm::ACollector;
     using xo::mm::AAllocator;
     using xo::mm::AGCObject;
 
@@ -84,8 +85,11 @@ namespace xo {
                 values_->resize(ix.j_slot() + 1);
             }
 
-            log && log("STUB: need write barrier for GC here");
-            (*values_)[ix.j_slot()] = x;
+            //auto gc = mm.try_to_facet<ACollector>();
+
+            values_->assign_at(mm,
+                               ix.j_slot(),
+                               x);
         }
 
         DVariable *