xo-gc: move mlog handling to separate tru MutationLogState.*pp

Still entangled with DX1Collector for object spaces

include/xo/gc/X1VerifyStats.hpp

@@ -0,0 +1,51 @@
+/** @file X1VerifyStats.hpp
+ *
+ *  @author Roland Conybeare, Apr 2026
+ **/
+
+#pragma once
+
+#include <cstdint>
+
+namespace xo {
+    namespace mm {
+
+        /** @brief info collected during a @ref DX1Collector::verify_ok call
+         *  (or @ref MutationLogState::verify_ok call)
+         **/
+        class VerifyStats {
+        public:
+            bool is_ok() const noexcept {
+                return (n_from_ == 0) && (n_fwd_ == 0) && (n_no_iface_ == 0);
+            }
+
+            void clear() { *this = VerifyStats(); }
+
+            /** number of gc roots examined **/
+            std::uint32_t n_gc_root_  = 0;
+            std::uint32_t n_ext_      = 0;
+            /** number of from-space objects encountered. Fatal if non-zero **/
+            std::uint32_t n_from_     = 0;
+            /** number of to-space objects encountered. **/
+            std::uint32_t n_to_       = 0;
+            /** counts forwarding object encountered in to-space scan. Fatal if non-zero **/
+            std::uint32_t n_fwd_      = 0;
+            /** counts missing GCObject interface. Fatal if non-zero **/
+            std::uint32_t n_no_iface_ = 0;
+            /** live mlog entry refers to to-space, as expected **/
+            std::uint32_t n_mlog_vital_ = 0;
+            /** stale mlog entry. not troubling to verify these **/
+            std::uint32_t n_mlog_stale_ = 0;
+            /** live mlog entry refers to from-space. Fatal if non-zero **/
+            std::uint32_t n_mlog_from_ = 0;
+            /** live mlog entry refers to either some other generation or outside gc-space.
+             *  Fatal if non-zero
+             **/
+            std::uint32_t n_mlog_wild_ = 0;
+
+        };
+
+    } /*namespace mm*/
+} /*namespace xo*/
+
+/* end X1VerifyStats.hpp */