13 files changed, 80 insertions, 62 deletions

diff --git a/src/cancel.h b/src/cancel.h
index e5dfe23..c1bee4e 100644
--- a/src/cancel.h
+++ b/src/cancel.h
@@ -46,17 +46,17 @@ typedef enum
 } CancelOp;
 
 // crc64/we of string "CANCEL_ERROR" generated at http://www.nitrxgen.net/hashgen/
-static DECLARE_CONST_UNIQUE_KEY(CANCEL_ERROR, 0xe97d41626cc97577); // 'cancel_error' sentinel
+static constexpr UniqueKey CANCEL_ERROR{ 0xe97d41626cc97577ull }; // 'cancel_error' sentinel
 
 // crc64/we of string "CANCEL_TEST_KEY" generated at http://www.nitrxgen.net/hashgen/
-static DECLARE_CONST_UNIQUE_KEY(CANCEL_TEST_KEY, 0xe66f5960c57d133a); // used as registry key
+static constexpr UniqueKey CANCEL_TEST_KEY{ 0xe66f5960c57d133aull }; // used as registry key
 
 cancel_result thread_cancel( lua_State* L, Lane* s, CancelOp op_, double secs_, bool force_, double waitkill_timeout_);
 
 static inline int cancel_error( lua_State* L)
 {
     STACK_GROW( L, 1);
-    push_unique_key( L, CANCEL_ERROR); // special error value
+    CANCEL_ERROR.push(L); // special error value
     return lua_error( L); // doesn't return
 }
 
diff --git a/src/deep.cpp b/src/deep.cpp
index 897dc63..c0aa25b 100644
--- a/src/deep.cpp
+++ b/src/deep.cpp
@@ -59,13 +59,13 @@ THE SOFTWARE.
 *   idfunc      ->  metatable
 */
 // crc64/we of string "DEEP_LOOKUP_KEY" generated at http://www.nitrxgen.net/hashgen/
-static DECLARE_CONST_UNIQUE_KEY( DEEP_LOOKUP_KEY, 0x9fb9b4f3f633d83d);
+static constexpr UniqueKey DEEP_LOOKUP_KEY{ 0x9fb9b4f3f633d83dull };
 
 /*
  * The deep proxy cache is a weak valued table listing all deep UD proxies indexed by the deep UD that they are proxying
  * crc64/we of string "DEEP_PROXY_CACHE_KEY" generated at http://www.nitrxgen.net/hashgen/
 */
-static DECLARE_CONST_UNIQUE_KEY( DEEP_PROXY_CACHE_KEY, 0x05773d6fc26be106);
+static constexpr UniqueKey DEEP_PROXY_CACHE_KEY{ 0x05773d6fc26be106ull };
 
 /*
 * Sets up [-1]<->[-2] two-way lookups, and ensures the lookup table exists.
@@ -390,7 +390,7 @@ int luaG_newdeepuserdata( lua_State* L, luaG_IdFunction idfunc, int nuv_)
         {
             return luaL_error( L, "idfunc(eDO_new) failed to create deep userdata (out of memory)");
         }
-        if( prelude->magic.value != DEEP_VERSION.value)
+        if( prelude->magic != DEEP_VERSION)
         {
             // just in case, don't leak the newly allocated deep userdata object
             lua_pushlightuserdata( L, prelude);
diff --git a/src/deep.h b/src/deep.h
index 728aa2a..d8a1772 100644
--- a/src/deep.h
+++ b/src/deep.h
@@ -42,18 +42,17 @@ typedef void* (*luaG_IdFunction)( lua_State* L, DeepOp op_);
 // ################################################################################################
 
 // fnv164 of string "DEEP_VERSION_2" generated at https://www.pelock.com/products/hash-calculator
-static DECLARE_CONST_UNIQUE_KEY( DEEP_VERSION, 0xB4B0119C10642B29);
+static constexpr UniqueKey DEEP_VERSION{ 0xB4B0119C10642B29ull };
 
 // should be used as header for full userdata
-struct s_DeepPrelude
+struct DeepPrelude
 {
-    DECLARE_UNIQUE_KEY( magic); // must be filled by the Deep userdata idfunc that allocates it on eDO_new operation
+    UniqueKey const magic{ DEEP_VERSION };
     // when stored in a keeper state, the full userdata doesn't have a metatable, so we need direct access to the idfunc
-    luaG_IdFunction idfunc;
+    luaG_IdFunction idfunc { nullptr };
     // data is destroyed when refcount is 0
-    volatile int refcount;
+    volatile int refcount{ 0 };
 };
-typedef struct s_DeepPrelude DeepPrelude;
 
 char const* push_deep_proxy( Universe* U, lua_State* L, DeepPrelude* prelude, int nuv_, LookupMode mode_);
 void free_deep_prelude( lua_State* L, DeepPrelude* prelude_);
diff --git a/src/keeper.cpp b/src/keeper.cpp
index 1e344f2..697fe71 100644
--- a/src/keeper.cpp
+++ b/src/keeper.cpp
@@ -166,7 +166,7 @@ static void fifo_pop( lua_State* L, keeper_fifo* fifo_, lua_Integer count_)
 // in: linda_ud expected at *absolute* stack slot idx
 // out: fifos[ud]
 // crc64/we of string "FIFOS_KEY" generated at http://www.nitrxgen.net/hashgen/
-static DECLARE_CONST_UNIQUE_KEY( FIFOS_KEY, 0xdce50bbc351cd465);
+static constexpr UniqueKey FIFOS_KEY{ 0xdce50bbc351cd465ull };
 static void push_table( lua_State* L, int idx_)
 {
     STACK_GROW( L, 4);
@@ -769,13 +769,13 @@ void keeper_toggle_nil_sentinels( lua_State* L, int val_i_, LookupMode const mod
         {
             if( lua_isnil( L, i))
             {
-                push_unique_key( L, NIL_SENTINEL);
+                NIL_SENTINEL.push(L);
                 lua_replace( L, i);
             }
         }
         else
         {
-            if( equal_unique_key( L, i, NIL_SENTINEL))
+            if (NIL_SENTINEL.equals(L, i))
             {
                 lua_pushnil( L);
                 lua_replace( L, i);
diff --git a/src/keeper.h b/src/keeper.h
index 33118be..4cf3605 100644
--- a/src/keeper.h
+++ b/src/keeper.h
@@ -43,7 +43,7 @@ void keeper_toggle_nil_sentinels( lua_State* L, int val_i_, LookupMode const mod
 int keeper_push_linda_storage( Universe* U, lua_State* L, void* ptr_, ptrdiff_t magic_);
 
 // crc64/we of string "NIL_SENTINEL" generated at http://www.nitrxgen.net/hashgen/
-static DECLARE_CONST_UNIQUE_KEY( NIL_SENTINEL, 0x7eaafa003a1d11a1);
+static constexpr UniqueKey NIL_SENTINEL{ 0x7eaafa003a1d11a1ull };
 
 typedef lua_CFunction keeper_api_t;
 #define KEEPER_API( _op) keepercall_ ## _op
diff --git a/src/lanes.cpp b/src/lanes.cpp
index fa69656..126f65c 100644
--- a/src/lanes.cpp
+++ b/src/lanes.cpp
@@ -128,7 +128,7 @@ static void securize_debug_threadname( lua_State* L, Lane* s)
 #if ERROR_FULL_STACK
 static int lane_error( lua_State* L);
 // crc64/we of string "STACKTRACE_REGKEY" generated at http://www.nitrxgen.net/hashgen/
-static DECLARE_CONST_UNIQUE_KEY( STACKTRACE_REGKEY, 0x534af7d3226a429f);
+static constexpr UniqueKey STACKTRACE_REGKEY{ 0x534af7d3226a429full };
 #endif // ERROR_FULL_STACK
 
 /*
@@ -140,7 +140,7 @@ static DECLARE_CONST_UNIQUE_KEY( STACKTRACE_REGKEY, 0x534af7d3226a429f);
 * anyways complicate that approach.
 */
 // crc64/we of string "FINALIZER_REGKEY" generated at http://www.nitrxgen.net/hashgen/
-static DECLARE_CONST_UNIQUE_KEY( FINALIZER_REGKEY, 0x188fccb8bf348e09);
+static constexpr UniqueKey FINALIZER_REGKEY{ 0x188fccb8bf348e09ull };
 
 struct s_Linda;
 
@@ -649,7 +649,7 @@ LUAG_FUNC( set_singlethreaded)
 #if ERROR_FULL_STACK
 
 // crc64/we of string "EXTENDED_STACKTRACE_REGKEY" generated at http://www.nitrxgen.net/hashgen/
-static DECLARE_CONST_UNIQUE_KEY( EXTENDED_STACKTRACE_REGKEY, 0x2357c69a7c92c936); // used as registry key
+static constexpr UniqueKey EXTENDED_STACKTRACE_REGKEY{ 0x2357c69a7c92c936ull }; // used as registry key
 
 LUAG_FUNC( set_error_reporting)
 {
@@ -683,7 +683,7 @@ static int lane_error( lua_State* L)
 
     // Don't do stack survey for cancelled lanes.
     //
-    if( equal_unique_key( L, 1, CANCEL_ERROR))
+    if (CANCEL_ERROR.equals(L, 1))
     {
         return 1;   // just pass on
     }
@@ -769,7 +769,7 @@ static void push_stack_trace( lua_State* L, int rc_, int stk_base_)
 
             // For cancellation the error message is CANCEL_ERROR, and a stack trace isn't placed
             // For other errors, the message can be whatever was thrown, and we should have a stack trace table
-            ASSERT_L( lua_type( L, 1 + stk_base_) == (equal_unique_key( L, stk_base_, CANCEL_ERROR) ? LUA_TNIL : LUA_TTABLE));
+            ASSERT_L(lua_type(L, 1 + stk_base_) == (CANCEL_ERROR.equals(L, stk_base_) ? LUA_TNIL : LUA_TTABLE));
             // Just leaving the stack trace table on the stack is enough to get it through to the master.
             break;
         }
@@ -779,14 +779,15 @@ static void push_stack_trace( lua_State* L, int rc_, int stk_base_)
         case LUA_ERRERR: // error while running the error handler (if any, for example an out-of-memory condition)
         default:
         // we should have a single value which is either a string (the error message) or CANCEL_ERROR
-        ASSERT_L( (lua_gettop( L) == stk_base_) && ((lua_type( L, stk_base_) == LUA_TSTRING) || equal_unique_key( L, stk_base_, CANCEL_ERROR)));
+        ASSERT_L((lua_gettop(L) == stk_base_) && ((lua_type(L, stk_base_) == LUA_TSTRING) || CANCEL_ERROR.equals(L, stk_base_)));
         break;
     }
 }
 
 LUAG_FUNC( set_debug_threadname)
 {
-    DECLARE_CONST_UNIQUE_KEY( hidden_regkey, LG_set_debug_threadname);
+    // fnv164 of string "debug_threadname" generated at https://www.pelock.com/products/hash-calculator
+    constexpr UniqueKey hidden_regkey{ 0x79C0669AAAE04440ull };
     // C s_lane structure is a light userdata upvalue
     Lane* s = (Lane*) lua_touserdata( L, lua_upvalueindex( 1));
     luaL_checktype( L, -1, LUA_TSTRING);                           // "name"
@@ -959,7 +960,7 @@ static THREAD_RETURN_T THREAD_CALLCONV lane_main( void* vs)
     {
         // leave results (1..top) or error message + stack trace (1..2) on the stack - master will copy them
 
-        enum e_status st = (rc == 0) ? DONE : equal_unique_key( L, 1, CANCEL_ERROR) ? CANCELLED : ERROR_ST;
+        enum e_status st = (rc == 0) ? DONE : CANCEL_ERROR.equals(L, 1) ? CANCELLED : ERROR_ST;
 
         // Posix no PTHREAD_TIMEDJOIN:
         // 'done_lock' protects the -> DONE|ERROR_ST|CANCELLED state change
@@ -1024,7 +1025,7 @@ LUAG_FUNC( register)
 }
 
 // crc64/we of string "GCCB_KEY" generated at http://www.nitrxgen.net/hashgen/
-static DECLARE_CONST_UNIQUE_KEY( GCCB_KEY, 0xcfb1f046ef074e88);
+static constexpr UniqueKey GCCB_KEY{ 0xcfb1f046ef074e88ull };
 
 //---
 // lane_ud = lane_new( function
@@ -1267,7 +1268,7 @@ LUAG_FUNC( lane_new)
     // Store the gc_cb callback in the uservalue
     if( gc_cb_idx > 0)
     {
-        push_unique_key( L, GCCB_KEY);                               // func libs priority globals package required gc_cb lane uv k
+        GCCB_KEY.push(L);                                            // func libs priority globals package required gc_cb lane uv k
         lua_pushvalue( L, gc_cb_idx);                                // func libs priority globals package required gc_cb lane uv k gc_cb
         lua_rawset( L, -3);                                          // func libs priority globals package required gc_cb lane uv
     }
@@ -1307,7 +1308,7 @@ LUAG_FUNC( thread_gc)
 
     // if there a gc callback?
     lua_getiuservalue( L, 1, 1);                                        // ud uservalue
-    push_unique_key( L, GCCB_KEY);                                      // ud uservalue __gc
+    GCCB_KEY.push(L);                                                   // ud uservalue __gc
     lua_rawget( L, -2);                                                 // ud uservalue gc_cb|nil
     if( !lua_isnil( L, -1))
     {
@@ -1986,7 +1987,7 @@ LUAG_FUNC( configure)
     lua_pushinteger(L, THREAD_PRIO_MAX);                                                   // settings M THREAD_PRIO_MAX
     lua_setfield( L, -2, "max_prio");                                                      // settings M
 
-    push_unique_key( L, CANCEL_ERROR);                                                     // settings M CANCEL_ERROR
+    CANCEL_ERROR.push(L);                                                                  // settings M CANCEL_ERROR
     lua_setfield( L, -2, "cancel_error");                                                  // settings M
 
     STACK_MID( L, 2); // reference stack contains only the function argument 'settings'
diff --git a/src/linda.cpp b/src/linda.cpp
index fa27871..4cc356a 100644
--- a/src/linda.cpp
+++ b/src/linda.cpp
@@ -137,7 +137,7 @@ LUAG_FUNC( linda_send)
         ++ key_i;
     }
 
-    bool const as_nil_sentinel{ equal_unique_key(L, key_i, NIL_SENTINEL) };// if not nullptr, send() will silently send a single nil if nothing is provided
+    bool const as_nil_sentinel{ NIL_SENTINEL.equals(L, key_i) }; // if not nullptr, send() will silently send a single nil if nothing is provided
     if( as_nil_sentinel)
     {
         // the real key to send data to is after the NIL_SENTINEL marker
@@ -155,7 +155,7 @@ LUAG_FUNC( linda_send)
         if( as_nil_sentinel)
         {
             // send a single nil if nothing is provided
-            push_unique_key( L, NIL_SENTINEL);
+            NIL_SENTINEL.push(L);
         }
         else
         {
@@ -243,7 +243,7 @@ LUAG_FUNC( linda_send)
     {
         case CANCEL_SOFT:
         // if user wants to soft-cancel, the call returns lanes.cancel_error
-        push_unique_key( L, CANCEL_ERROR);
+        CANCEL_ERROR.push(L);
         return 1;
 
         case CANCEL_HARD:
@@ -397,7 +397,7 @@ LUAG_FUNC( linda_receive)
     {
         case CANCEL_SOFT:
         // if user wants to soft-cancel, the call returns CANCEL_ERROR
-        push_unique_key( L, CANCEL_ERROR);
+        CANCEL_ERROR.push(L);
         return 1;
 
         case CANCEL_HARD:
@@ -458,7 +458,7 @@ LUAG_FUNC( linda_set)
         else // linda is cancelled
         {
             // do nothing and return lanes.cancel_error
-            push_unique_key( L, CANCEL_ERROR);
+            CANCEL_ERROR.push(L);
             pushed = 1;
         }
     }
@@ -522,7 +522,7 @@ LUAG_FUNC( linda_get)
         else // linda is cancelled
         {
             // do nothing and return lanes.cancel_error
-            push_unique_key( L, CANCEL_ERROR);
+            CANCEL_ERROR.push(L);
             pushed = 1;
         }
         // an error can be raised if we attempt to read an unregistered function
@@ -570,7 +570,7 @@ LUAG_FUNC( linda_limit)
         else // linda is cancelled
         {
             // do nothing and return lanes.cancel_error
-            push_unique_key( L, CANCEL_ERROR);
+            CANCEL_ERROR.push(L);
             pushed = 1;
         }
     }
@@ -798,7 +798,7 @@ static void* linda_id( lua_State* L, DeepOp op_)
             }
             if( s)
             {
-                s->prelude.magic.value = DEEP_VERSION.value;
+                s->prelude.DeepPrelude::DeepPrelude();
                 SIGNAL_INIT( &s->read_happened);
                 SIGNAL_INIT( &s->write_happened);
                 s->U = universe_get( L);
@@ -901,7 +901,7 @@ static void* linda_id( lua_State* L, DeepOp op_)
             lua_pushliteral( L, BATCH_SENTINEL);
             lua_setfield( L, -2, "batched");
 
-            push_unique_key( L, NIL_SENTINEL);
+            NIL_SENTINEL.push(L);
             lua_setfield( L, -2, "null");
 
             STACK_END( L, 1);
diff --git a/src/macros_and_utils.h b/src/macros_and_utils.h
index 8a4ffb3..ae93e97 100644
--- a/src/macros_and_utils.h
+++ b/src/macros_and_utils.h
@@ -83,14 +83,14 @@ extern char const* debugspew_indent;
 // non-string keyed registry access
 #define REGISTRY_SET( L, key_, value_) \
 { \
-    push_unique_key( L, key_); \
+    key_.push(L); \
     value_; \
     lua_rawset( L, LUA_REGISTRYINDEX); \
 }
 
 #define REGISTRY_GET( L, key_) \
 { \
-    push_unique_key( L, key_); \
+    key_.push(L); \
     lua_rawget( L, LUA_REGISTRYINDEX); \
 }
 
diff --git a/src/tools.cpp b/src/tools.cpp
index e6ebdba..ac2cf75 100644
--- a/src/tools.cpp
+++ b/src/tools.cpp
@@ -328,7 +328,7 @@ static lua_CFunction luaG_tocfunction( lua_State *L, int _i, FuncSubType *_out)
 }
 
 // crc64/we of string "LOOKUPCACHE_REGKEY" generated at http://www.nitrxgen.net/hashgen/
-static DECLARE_CONST_UNIQUE_KEY( LOOKUPCACHE_REGKEY, 0x837a68dfc6fcb716);
+static constexpr UniqueKey LOOKUPCACHE_REGKEY{ 0x837a68dfc6fcb716ull };
 
 // inspired from tconcat() in ltablib.c
 static char const* luaG_pushFQN( lua_State* L, int t, int last, size_t* length)
@@ -627,7 +627,7 @@ void populate_func_lookup_table( lua_State* L, int _i, char const* name_)
 /*---=== Inter-state copying ===---*/
 
 // crc64/we of string "REG_MTID" generated at http://www.nitrxgen.net/hashgen/
-static DECLARE_CONST_UNIQUE_KEY( REG_MTID, 0x2e68f9b4751584dc);
+static constexpr UniqueKey REG_MTID{ 0x2e68f9b4751584dcull };
 
 /*
 * Get a unique ID for metatable at [i].
@@ -845,7 +845,7 @@ static bool lookup_table( lua_State* L2, lua_State* L, uint_t i, LookupMode mode
 static bool push_cached_table( lua_State* L2, uint_t L2_cache_i, lua_State* L, uint_t i)
 {
     bool not_found_in_cache;                                                                         // L2
-    DECLARE_CONST_UNIQUE_KEY( p, lua_topointer( L, i));
+    void const* p{ lua_topointer(L, i) };
 
     ASSERT_L( L2_cache_i != 0);
     STACK_GROW( L2, 3);
@@ -854,7 +854,7 @@ static bool push_cached_table( lua_State* L2, uint_t L2_cache_i, lua_State* L, u
     // We don't need to use the from state ('L') in ID since the life span
     // is only for the duration of a copy (both states are locked).
     // push a light userdata uniquely representing the table
-    push_unique_key( L2, p);                                                                         // ... p
+    lua_pushlightuserdata(L2, const_cast<void*>(p));                                                 // ... p
 
     //fprintf( stderr, "<< ID: %s >>\n", lua_tostring( L2, -1));
 
@@ -864,7 +864,7 @@ static bool push_cached_table( lua_State* L2, uint_t L2_cache_i, lua_State* L, u
     {
         lua_pop( L2, 1);                                                                             // ...
         lua_newtable( L2);                                                                           // ... {}
-        push_unique_key( L2, p);                                                                     // ... {} p
+        lua_pushlightuserdata(L2, const_cast<void*>(p));                                             // ... {} p
         lua_pushvalue( L2, -2);                                                                      // ... {} p {}
         lua_rawset( L2, L2_cache_i);                                                                 // ... {}
     }
@@ -1508,7 +1508,7 @@ static void inter_copy_keyvaluepair( Universe* U, lua_State* L2, uint_t L2_cache
 * The clone cache is a weak valued table listing all clones, indexed by their userdatapointer
 * fnv164 of string "CLONABLES_CACHE_KEY" generated at https://www.pelock.com/products/hash-calculator
 */
-static DECLARE_CONST_UNIQUE_KEY( CLONABLES_CACHE_KEY, 0xD04EE018B3DEE8F5);
+static constexpr UniqueKey CLONABLES_CACHE_KEY{ 0xD04EE018B3DEE8F5ull };
 
 static bool copyclone( Universe* U, lua_State* L2, uint_t L2_cache_i, lua_State* L, uint_t source_i_, LookupMode mode_, char const* upName_)
 {
diff --git a/src/tools.h b/src/tools.h
index 9214d85..928a149 100644
--- a/src/tools.h
+++ b/src/tools.h
@@ -47,7 +47,7 @@ void cleanup_allocator_function( Universe* U, lua_State* L);
 // ################################################################################################
 
 // crc64/we of string "CONFIG_REGKEY" generated at http://www.nitrxgen.net/hashgen/
-static DECLARE_CONST_UNIQUE_KEY( CONFIG_REGKEY, 0x31cd24894eae8624); // 'cancel_error' sentinel
+static constexpr UniqueKey CONFIG_REGKEY{ 0x31cd24894eae8624ull }; // registry key to access the configuration
 
 // crc64/we of string "LOOKUP_REGKEY" generated at http://www.nitrxgen.net/hashgen/
-static DECLARE_CONST_UNIQUE_KEY( LOOKUP_REGKEY, 0x5051ed67ee7b51a1); // 'cancel_error' sentinel
+static constexpr UniqueKey LOOKUP_REGKEY{ 0x5051ed67ee7b51a1ull }; // registry key to access the lookup database
diff --git a/src/uniquekey.h b/src/uniquekey.h
index f219ab1..fb98628 100644
--- a/src/uniquekey.h
+++ b/src/uniquekey.h
@@ -2,21 +2,40 @@
 
 #include "compat.h"
 
-// Lua light userdata can hold a pointer.
-struct s_UniqueKey
+class UniqueKey
 {
-    void* value;
-};
-typedef struct s_UniqueKey UniqueKey;
+    private:
+
+    uintptr_t m_storage;
+
+    public:
 
+    constexpr UniqueKey(uintptr_t val_)
 #if LUAJIT_FLAVOR() == 64 // building against LuaJIT headers for 64 bits, light userdata is restricted to 47 significant bits, because LuaJIT uses the other bits for internal optimizations
-#define MAKE_UNIQUE_KEY( p_) ((void*)((ptrdiff_t)(p_) & 0x7fffffffffffull))
+    : m_storage{ val_ & 0x7fffffffffffull }
 #else // LUAJIT_FLAVOR()
-#define MAKE_UNIQUE_KEY( p_) ((void*)(ptrdiff_t)(p_))
+    : m_storage{ val_ }
 #endif // LUAJIT_FLAVOR()
+    {
+    }
+    constexpr UniqueKey(UniqueKey const& rhs_) = default;
+    constexpr bool operator!=(UniqueKey const& rhs_) const
+    {
+        return m_storage != rhs_.m_storage;
+    }
+    constexpr bool operator==(UniqueKey const& rhs_) const
+    {
+        return m_storage == rhs_.m_storage;
+    }
 
-#define DECLARE_UNIQUE_KEY( name_) UniqueKey name_
-#define DECLARE_CONST_UNIQUE_KEY( name_, p_) UniqueKey const name_ = { MAKE_UNIQUE_KEY( p_)}
-
-#define push_unique_key( L, key_) lua_pushlightuserdata( L, key_.value)
-#define equal_unique_key( L, i, key_) (lua_touserdata( L, i) == key_.value)
+    void push(lua_State* const L) const
+    {
+        // unfortunately, converting a scalar to a pointer must go through a C cast
+        lua_pushlightuserdata(L, (void*) m_storage);
+    }
+    bool equals(lua_State* const L, int i) const
+    {
+        // unfortunately, converting a scalar to a pointer must go through a C cast
+        return lua_touserdata(L, i) == (void*) m_storage;
+    }
+};
diff --git a/src/universe.cpp b/src/universe.cpp
index d5cc9e2..a31189c 100644
--- a/src/universe.cpp
+++ b/src/universe.cpp
@@ -37,7 +37,7 @@ THE SOFTWARE.
 #include "uniquekey.h"
 
 // crc64/we of string "UNIVERSE_REGKEY" generated at http://www.nitrxgen.net/hashgen/
-static DECLARE_CONST_UNIQUE_KEY( UNIVERSE_REGKEY, 0x9f877b2cf078f17f);
+static constexpr UniqueKey UNIVERSE_REGKEY{ 0x9f877b2cf078f17full };
 
 // ################################################################################################
 
diff --git a/src/universe.h b/src/universe.h
index 77b3ea5..0599302 100644
--- a/src/universe.h
+++ b/src/universe.h
@@ -12,8 +12,7 @@ extern "C" {
 #include "macros_and_utils.h"
 
 // forwards
-struct s_DeepPrelude;
-typedef struct s_DeepPrelude DeepPrelude;
+struct DeepPrelude;
 struct s_Keepers;
 typedef struct s_Keepers Keepers;
 struct s_Lane;