From 49c0904a4a8cdb6f704a7b91d3d61a0836581168 Mon Sep 17 00:00:00 2001
From: Roland Conybeare <rconybeare@gmail.com>
Date: Tue, 6 Jan 2026 17:39:10 -0500
Subject: [PATCH] xo-arena: + DArena.expand utest

---
 xo-alloc2/utest/arena.test.cpp                |  2 +-
 xo-arena/include/xo/arena/DArena.hpp          |  4 +++
 .../include/xo/arena}/print.hpp               |  0
 xo-arena/utest/DArena.test.cpp                | 32 ++++++++++++++++++-
 4 files changed, 36 insertions(+), 2 deletions(-)
 rename {xo-alloc2/include/xo/alloc2 => xo-arena/include/xo/arena}/print.hpp (100%)

diff --git a/xo-alloc2/utest/arena.test.cpp b/xo-alloc2/utest/arena.test.cpp
index 7ece32c7..ed168330 100644
--- a/xo-alloc2/utest/arena.test.cpp
+++ b/xo-alloc2/utest/arena.test.cpp
@@ -6,7 +6,7 @@
 #include "xo/alloc2/Allocator.hpp"
 #include "xo/alloc2/alloc/IAllocator_Xfer.hpp"
 #include "xo/alloc2/arena/IAllocator_DArena.hpp"
-#include "xo/alloc2/print.hpp"
+#include "xo/arena/print.hpp"
 #include "xo/arena/padding.hpp"
 #include <xo/facet/obj.hpp>
 #include <xo/indentlog/scope.hpp>
diff --git a/xo-arena/include/xo/arena/DArena.hpp b/xo-arena/include/xo/arena/DArena.hpp
index 3ad10db6..a3253220 100644
--- a/xo-arena/include/xo/arena/DArena.hpp
+++ b/xo-arena/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_)
diff --git a/xo-alloc2/include/xo/alloc2/print.hpp b/xo-arena/include/xo/arena/print.hpp
similarity index 100%
rename from xo-alloc2/include/xo/alloc2/print.hpp
rename to xo-arena/include/xo/arena/print.hpp
diff --git a/xo-arena/utest/DArena.test.cpp b/xo-arena/utest/DArena.test.cpp
index 6293c7a2..a94b5b09 100644
--- a/xo-arena/utest/DArena.test.cpp
+++ b/xo-arena/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);
+
+        }
+
     }
 }