xo-gc: refactor for MutationLogStore bugs [TESTFAIL]

src/gc/MutationLogEntry.cpp

@@ -4,8 +4,11 @@
  **/
 
 #include "MutationLogEntry.hpp"
+#include <xo/gc/GCObjectStore.hpp>
 
 namespace xo {
+    using xo::reflect::typeseq;
+
     namespace mm {
 
         MutationLogEntry::MutationLogEntry(void * parent,
@@ -16,6 +19,71 @@ namespace xo {
                   snap_{snap}
         {}
 
+        bool
+        MutationLogEntry::refresh_snapshot(Generation parent_gen,
+                                           GCObjectStore * gcos) noexcept
+        {
+            void * child_data = *p_data_;
+            // note: never the same child_info as computed at the top of
+            //       MutationLogEntry._preserve_child_of_live_parent()
+            //       Child pointer was either forwarding pointer or moved.
+            //       In either case must pickup info for new location.
+            //
+            AllocInfo child_info = gcos->alloc_info((std::byte*)child_data);
+
+            if (child_info.is_forwarding_tseq()) {
+                // code salvaged from MutationLogStore._check_keep_mutation_aux()
+                // as reminder.  But if caller is gc will have to know this anyway,
+                // so it can move child
+
+                // if (info.is_forwarding_tseq()) {
+                //    child_data = *(void **)child_data;
+                //    info = gcos->alloc_info((std::byte *)child_data);
+                //}
+
+                assert(false);  // for now assuming caller forward child
+            }
+
+            Generation child_gen_to
+                = gcos->generation_of(Role::to_space(), child_data);
+
+            if (child_gen_to.is_sentinel()) {
+                // child no longer points to gc-owned space.
+                // 1. may not have an alloc header (could be a static global for example),
+                //    so AllocInfo not available
+                // 2. doesn't need a mutation log entry since this gc can't move destination
+
+                snap_.data_ = nullptr; // hygiene
+
+                return false;
+            }
+
+            const GCObjectStoreConfig & config = gcos->config();
+
+            bool need_mlog_entry
+                = ((child_gen_to + 1 < config.n_generation_)
+                   && (config.promotion_threshold(parent_gen)
+                       > config.promotion_threshold(child_gen_to)));
+
+            if (need_mlog_entry) {
+                AGCObject * iface = gcos->lookup_type(typeseq(child_info.tseq()));
+
+                if (iface) {
+                    this->snap_ = obj<AGCObject>(iface, child_data);
+
+                    // snapshot updated, keep mlog entry
+                    return true;
+                } else {
+                    assert(false);
+
+                    return false;
+                }
+            } else {
+                // retire this entry.
+                return false;
+            }
+        }
+
     } /*namespace mm*/
 } /*namespace xo*/