xo-alloc2: + Allocator::alloc_info()

Also extend unit test

xo-alloc2/include/xo/alloc2/arena/DArena.hpp

@@ -88,6 +88,18 @@ namespace xo {
             /** get header from allocated object address **/
             header_type * obj2hdr(void * obj) noexcept;
 
+            /** report alloc book-keeping info for allocation at @p mem
+             *
+             *  Require:
+             *  1. @p mem is address returned by allocation on this arena
+             *     i.e. by @ref IAllocator_DArena::alloc() or @ref IAllocator_DArena::alloc_super()
+             *  2. @p mem has not been invalidated since it was allocated
+             *     i.e. by call to @ref DArena::clear
+             *
+             *  Note: non-const, may stash error details
+             **/
+            AllocInfo alloc_info(value_type mem) noexcept;
+
             /** discard all allocated memory, return to empty state
              *  Promise:
              *  - committed memory unchanged

xo-alloc2/include/xo/alloc2/arena/IAllocator_DArena.hpp

@@ -45,6 +45,8 @@ namespace xo {
             static bool contains(const DArena &, const void * p) noexcept;
             static AllocatorError last_error(const DArena &) noexcept;
 
+            /** retrieve allocation bookkeeping info for @p mem from arena @p d **/
+            static AllocInfo alloc_info(DArena &, value_type mem) noexcept;
             /** expand committed space in arena @p d
              *  to size at least @p z
              *  In practice will round up to a multiple of @ref page_z_.