xo-alloc2: ++ documentation + threshold size for THP feature

src/alloc2/AllocError.cpp

@@ -0,0 +1,45 @@
+/** @file AllocError.cpp
+ *
+ *  @author Roland Conybeare, Dec 2025
+ **/
+
+#include "AllocError.hpp"
+
+namespace xo {
+    namespace mm {
+
+        const char *
+        AllocError::error_description(error x)
+        {
+            switch (x) {
+            case error::invalid:
+                break;
+            case error::ok:
+                return "ok";
+            case error::reserve_exhausted:
+                return "reserve-exhausted";
+            case error::commit_failed:
+                return "commit-failed";
+            case error::header_size_mask:
+                return "header-size-mask";
+            case error::orphan_sub_alloc:
+                return "orphan-sub-alloc";
+            case error::alloc_info_disabled:
+                return "alloc-info-disabled";
+            case error::alloc_info_address:
+                return "alloc-info-address";
+            case error::alloc_iterator_not_supported:
+                return "alloc-iterator-not-supported";
+            case error::alloc_iterator_deref:
+                return "alloc-iterator-deref";
+            case error::alloc_iterator_next:
+                return "alloc-iterator-next";
+            }
+
+            return "?error";
+        }
+
+    } /*namespace mm*/
+} /*namespace xo*/
+
+/* end AllocError.cpp */