mem/pool: Alloc-bound pooled things

These pieces of metadata (specifically, the Allocator structures) are never
deallocated at the moment, so we need not consider how we might amplify these
bounded pointers back to higher authority.

src/snmalloc/mem/pool.h

@@ -29,7 +29,7 @@ namespace snmalloc
   private:
     MPMCStack<T, PreZeroed> stack;
     FlagWord lock{};
-    T* list{nullptr};
+    capptr::Alloc<T> list{nullptr};
 
   public:
     constexpr PoolState() = default;
@@ -121,12 +121,12 @@ namespace snmalloc
     static T* acquire(Args&&... args)
     {
       PoolState<T>& pool = get_state();
-      T* p = pool.stack.pop();
+      auto p = capptr::Alloc<T>::unsafe_from(pool.stack.pop());
 
       if (p != nullptr)
       {
         p->set_in_use();
-        return p;
+        return p.unsafe_ptr();
       }
 
       auto raw =
@@ -137,14 +137,18 @@ namespace snmalloc
         Config::Pal::error("Failed to initialise thread local allocator.");
       }
 
-      p = new (raw.unsafe_ptr()) T(std::forward<Args>(args)...);
+      p = capptr_to_user_address_control(
+        Aal::capptr_bound<T, capptr::bounds::AllocFull>(
+          capptr::Arena<T>::unsafe_from(new (raw.unsafe_ptr())
+                                          T(std::forward<Args>(args)...)),
+          sizeof(T)));
 
       FlagLock f(pool.lock);
       p->list_next = pool.list;
       pool.list = p;
 
       p->set_in_use();
-      return p;
+      return p.unsafe_ptr();
     }
 
     /**
@@ -185,9 +189,9 @@ namespace snmalloc
     static T* iterate(T* p = nullptr)
     {
       if (p == nullptr)
-        return get_state().list;
+        return get_state().list.unsafe_ptr();
 
-      return p->list_next;
+      return p->list_next.unsafe_ptr();
     }
   };
 } // namespace snmalloc

src/snmalloc/mem/pooled.h

@@ -23,7 +23,7 @@ namespace snmalloc
     /// Used by the pool for chaining together entries when not in use.
     std::atomic<T*> next{nullptr};
     /// Used by the pool to keep the list of all entries ever created.
-    T* list_next;
+    capptr::Alloc<T> list_next;
     std::atomic_flag in_use = ATOMIC_FLAG_INIT;
 
   public: