xo-arena: + DArena.expand utest

include/xo/arena/DArena.hpp

@@ -105,6 +105,10 @@ namespace xo {
              *  This is the amount of memory guaranteed to be usable for future allocs from this arena.
              **/
             size_type available() const noexcept { return limit_ - free_; }
+            /** VM page size for this arena (likely 4KB) **/
+            size_type page_z() const noexcept { return page_z_; }
+            /** Last error encountered by this arena **/
+            const AllocError & last_error() const noexcept { return last_error_; }
 
             /** True iff address @p addr is owned by this arena,
              *  i.e. falls within [@ref lo_, @ref hi_)

include/xo/arena/print.hpp

@@ -0,0 +1,34 @@
+/** @file print.hpp
+*
+ *  @author Roland Conybeare, Dec 2025
+ **/
+
+#pragma once
+
+#include "AllocError.hpp"
+#include <xo/indentlog/print/tag.hpp>
+#include <iostream>
+
+namespace xo {
+    namespace mm {
+        inline std::ostream &
+        operator<<(std::ostream & os, const error & x) {
+            os << AllocError::error_description(x);
+            return os;
+        }
+
+        inline std::ostream &
+        operator<<(std::ostream & os, const AllocError & x) {
+            os << "<AllocError"
+               << xtag("error", x.error_)
+               << xtag("seq", x.error_seq_)
+               << xtag("req_z", x.request_z_)
+               << xtag("commit_z", x.committed_z_)
+               << xtag("resv_z", x.reserved_z_)
+               << ">";
+            return os;
+        }
+    }
+}
+
+/* end print.hpp */

utest/DArena.test.cpp

@@ -3,12 +3,15 @@
  *  @author Roland Conybeare, Jan 2026
  **/
 
-#include "xo/arena/DArena.hpp"
+#include "DArena.hpp"
+#include "print.hpp"
+#include <xo/indentlog/print/tag.hpp>
 #include <catch2/catch.hpp>
 
 namespace xo {
     using xo::mm::DArena;
     using xo::mm::ArenaConfig;
+    using xo::xtag;
     using std::byte;
 
     namespace ut {
@@ -98,6 +101,33 @@ namespace xo {
             REQUIRE(arena2.committed_z_ == committed_z);
         }
 
+        TEST_CASE("arena-expand-1", "[arena][DArena]")
+        {
+            /* typed allocator a1o */
+            ArenaConfig cfg { .name_ = "testarena",
+                              .size_ = 1,
+                              .debug_flag_ = false };
+            DArena arena = DArena::map(cfg);
+
+            REQUIRE(arena.available() == 0);
+            REQUIRE(arena.allocated() == 0);
+
+            size_t z2 = 512;
+            bool ok = arena.expand(z2);
+
+            INFO(xtag("last_error", arena.last_error()));
+
+            REQUIRE(ok);
+
+            REQUIRE(arena.reserved() % arena.page_z() == 0);
+            REQUIRE(arena.committed() >= z2);
+            REQUIRE(arena.committed() % arena.page_z() == 0);
+            REQUIRE(arena.available() >= z2);
+            REQUIRE(arena.available() == arena.committed());
+            REQUIRE(arena.allocated() == 0);
+
+        }
+
     }
 }