xo-alloc2: + Allocator.expand() + streamlining _Any

src/alloc2/IAllocator_Any.cpp

@@ -4,6 +4,7 @@
  **/
 
 #include "IAllocator_Any.hpp"
+#include <iostream>
 
 namespace xo {
     using xo::facet::DVariantPlaceholder;
@@ -12,6 +13,17 @@ namespace xo {
 
     namespace mm {
 
+        void
+        IAllocator_Any::_fatal() {
+            /* control here on uninitialized IAllocator_Any.
+             * Initialized instance will have specific implementation type
+             * e.g. IAllocator_Xfer<DArena>
+             */
+
+            std::cerr << "fatal: attempt to call uninitialized IAllocator_Any" << std::endl;
+            std::terminate();
+        }
+
         int32_t
         IAllocator_Any::s_typeseq = typeseq::id<DVariantPlaceholder>();