xo-interpreter2: virtual root for VSM itself

BACKLOG.md

@@ -1,20 +1,20 @@
 # reader2
 
-## globalsymtab for essential primitives
-
-rework essential primitives (*,/,+,-,==,!=,..)
-so parser doesn't rely on magic globalsymtab lookup strings.
-
-## support missing primitives
-
-tokenizer support + utest for !=,<,>,<=,>=
-
 ## boolean operators
 
 ^ (xor), | (or), & (and), ~ (not)
 
 # gc
 
+## add_virtual_root
+
+Explicit alternative to `add_gc_root_poly()` for virtual roots.
+Since gc doesn't touch data pointer for virtual roots, we can pass
+`obj<AGCObject>` instead of `obj<AGCObject>*`.
+
+Will evolve some awkwardness in VSM: having to construct a purposeless
+`obj<AGCObject,DVirtualSchematikaMachine>` just to appease the `add_gc_root_poly` signature.
+
 ## remove_root
 
 Remove root doesn't work.

xo-interpreter2/src/interpreter2/DVirtualSchematikaMachine.cpp

@@ -47,6 +47,7 @@ namespace xo {
     using xo::mm::AGCObject;
     using xo::mm::MemorySizeInfo;
     using xo::mm::AAllocator;
+    using xo::mm::ACollector;
     using xo::mm::DX1Collector;
     using xo::mm::DArena;
     using xo::facet::FacetRegistry;
@@ -73,6 +74,7 @@ namespace xo {
         DVirtualSchematikaMachine::DVirtualSchematikaMachine(const VsmConfig & config,
                                                              obj<AAllocator> aux_mm)
         : config_{config},
+          self_vroot_{obj<AGCObject,DVirtualSchematikaMachine>(this)},
           aux_mm_{aux_mm},
           mm_(abox<AAllocator,DX1Collector>::make(aux_mm_, config.x1_config_)),
           rcx_(abox<ARuntimeContext,DVsmRcx>::make(aux_mm_, this)),
@@ -88,7 +90,13 @@ namespace xo {
             this->global_env_
                 = obj<AGCObject,DGlobalEnv>(reader_.global_env());
 
-            //this->_add_gc_roots();
+            // TODO:
+            // annoying to have to create self_vroot_ to appease
+            // add_gc_root_poly() signature.
+            // In practice gc won't modify the pointer
+            // (instead traverses it to find +update children)
+            //
+            mm_.to_op().to_facet<ACollector>().add_gc_root_poly(&self_vroot_);
         }
 
         DVirtualSchematikaMachine *