8 files changed, 108 insertions, 59 deletions

diff --git a/src/deep.cpp b/src/deep.cpp
index 6f4da9f..7b287f5 100644
--- a/src/deep.cpp
+++ b/src/deep.cpp
@@ -62,37 +62,6 @@ namespace {
     // #############################################################################################
     // #############################################################################################
 
-    /*
-     * void= mt.__gc( proxy_ud )
-     *
-     * End of life for a proxy object; reduce the deep reference count and clean it up if reaches 0.
-     *
-     */
-    [[nodiscard]]
-    static int DeepGC(lua_State* const L_)
-    {
-        DeepPrelude* const* const _proxy{ luaG_tofulluserdata<DeepPrelude*>(L_, StackIndex{ 1 }) };
-        DeepPrelude* const _p{ *_proxy };
-
-        // can work without a universe if creating a deep userdata from some external C module when Lanes isn't loaded
-        // in that case, we are not multithreaded and locking isn't necessary anyway
-        bool const _isLastRef{ _p->refcount.fetch_sub(1, std::memory_order_relaxed) == 1 };
-
-        if (_isLastRef) {
-            // retrieve wrapped __gc, if any
-            lua_pushvalue(L_, lua_upvalueindex(1));                                                // L_: self __gc?
-            if (!lua_isnil(L_, -1)) {
-                lua_insert(L_, -2);                                                                // L_: __gc self
-                lua_call(L_, 1, 0);                                                                // L_:
-            } else {
-                // need an empty stack in case we are GC_ing from a Keeper, so that empty stack checks aren't triggered
-                lua_pop(L_, 2);                                                                    // L_:
-            }
-            DeepFactory::DeleteDeepObject(L_, _p);
-        }
-        return 0;
-    }
-
     // #############################################################################################
 
     // Pops the key (metatable or factory) off the stack, and replaces with the deep lookup value (factory/metatable/nil).
@@ -121,6 +90,39 @@ namespace {
 // #################################################################################################
 // #################################################################################################
 
+/*
+    * void= mt.__gc( proxy_ud )
+    *
+    * End of life for a proxy object; reduce the deep reference count and clean it up if reaches 0.
+    *
+    */
+[[nodiscard]]
+int DeepFactory::DeepGC(lua_State* const L_)
+{
+    DeepPrelude* const* const _proxy{ luaG_tofulluserdata<DeepPrelude*>(L_, StackIndex{ 1 }) };
+    DeepPrelude* const _p{ *_proxy };
+
+    // can work without a universe if creating a deep userdata from some external C module when Lanes isn't loaded
+    // in that case, we are not multithreaded and locking isn't necessary anyway
+    bool const _isLastRef{ _p->refcount.fetch_sub(1, std::memory_order_relaxed) == 1 };
+
+    if (_isLastRef) {
+        // retrieve wrapped __gc, if any
+        lua_pushvalue(L_, lua_upvalueindex(1));                                                // L_: self __gc?
+        if (!lua_isnil(L_, -1)) {
+            lua_insert(L_, -2);                                                                // L_: __gc self
+            lua_call(L_, 1, 0);                                                                // L_:
+        } else {
+            // need an empty stack in case we are GC_ing from a Keeper, so that empty stack checks aren't triggered
+            lua_pop(L_, 2);                                                                    // L_:
+        }
+        DeepFactory::DeleteDeepObject(L_, _p);
+    }
+    return 0;
+}
+
+// #################################################################################################
+
 // NEVER call deleteDeepObjectInternal by itself, ALWAYS go through DeleteDeepObject()
 void DeepFactory::DeleteDeepObject(lua_State* const L_, DeepPrelude* const o_)
 {
@@ -381,7 +383,7 @@ DeepPrelude* DeepFactory::toDeep(lua_State* const L_, StackIndex const index_) c
 
 // #################################################################################################
 
-void DeepPrelude::push(lua_State* L_) const
+void DeepPrelude::push(lua_State* const L_) const
 {
     STACK_CHECK_START_REL(L_, 0);
     kDeepProxyCacheRegKey.getSubTableMode(L_, "v");                                                // L_: DPC
diff --git a/src/deep.hpp b/src/deep.hpp
index 6fa12b1..e4bdaca 100644
--- a/src/deep.hpp
+++ b/src/deep.hpp
@@ -20,19 +20,26 @@ static constexpr UniqueKey kDeepVersion{ 0x91171AEC6641E9DBull, "kDeepVersion" }
 
 // should be used as header for deep userdata
 // a deep userdata is a full userdata that stores a single pointer to the actual DeepPrelude-derived object
-struct DeepPrelude
+class DeepPrelude
 {
+    friend class DeepFactory;
+
+    private:
     UniqueKey const magic{ kDeepVersion };
     // when stored in a keeper state, the full userdata doesn't have a metatable, so we need direct access to the factory
     DeepFactory& factory;
+
+    protected:
     // data is destroyed when refcount is 0
     std::atomic<int> refcount{ 0 };
 
+    protected:
     DeepPrelude(DeepFactory& factory_)
     : factory{ factory_ }
     {
     }
 
+    public:
     void push(lua_State* L_) const;
 };
 
@@ -63,6 +70,8 @@ class DeepFactory
     virtual std::string_view moduleName() const = 0;
 
     private:
+    [[nodiscard]]
+    static int DeepGC(lua_State* L_);
     void storeDeepLookup(lua_State* L_) const;
 
     public:
diff --git a/src/lanes.cpp b/src/lanes.cpp
index 0b29a8f..83d01fb 100644
--- a/src/lanes.cpp
+++ b/src/lanes.cpp
@@ -86,6 +86,7 @@ THE SOFTWARE.
 #include "intercopycontext.hpp"
 #include "keeper.hpp"
 #include "lane.hpp"
+#include "linda.hpp"
 #include "nameof.hpp"
 #include "state.hpp"
 #include "threading.hpp"
diff --git a/src/linda.cpp b/src/linda.cpp
index 6ebbc1f..7af387f 100644
--- a/src/linda.cpp
+++ b/src/linda.cpp
@@ -130,6 +130,8 @@ namespace {
 // #################################################################################################
 // #################################################################################################
 
+LUAG_FUNC(linda);
+
 // #################################################################################################
 // #################################################################################################
 // #################################### Linda implementation #######################################
@@ -165,6 +167,38 @@ Keeper* Linda::acquireKeeper() const
 
 // #################################################################################################
 
+Linda* Linda::CreateTimerLinda(lua_State* const L_)
+{
+    STACK_CHECK_START_REL(L_, 0);                                                                  // L_:
+    // Initialize 'timerLinda'; a common Linda object shared by all states
+    lua_pushcfunction(L_, LG_linda);                                                               // L_: lanes.linda
+    luaG_pushstring(L_, "lanes-timer");                                                            // L_: lanes.linda "lanes-timer"
+    lua_pushinteger(L_, 0);                                                                        // L_: lanes.linda "lanes-timer" 0
+    lua_call(L_, 2, 1);                                                                            // L_: linda
+    STACK_CHECK(L_, 1);
+
+    // Proxy userdata contents is only a 'DeepPrelude*' pointer
+    auto const _timerLinda{ *luaG_tofulluserdata<Linda*>(L_, kIdxTop) };
+    // increment refcount so that this linda remains alive as long as the universe exists.
+    _timerLinda->refcount.fetch_add(1, std::memory_order_relaxed);
+    lua_pop(L_, 1);                                                                                // L_:
+    STACK_CHECK(L_, 0);
+    return _timerLinda;
+}
+
+// #################################################################################################
+
+void Linda::DeleteTimerLinda(lua_State* const L_, Linda* const linda_)
+{
+    if (linda_ != nullptr) { // test in case some early internal error prevented Lanes from creating the deep timer
+        [[maybe_unused]] auto const _prev_ref_count{ linda_->refcount.fetch_sub(1, std::memory_order_relaxed) };
+        LUA_ASSERT(L_, _prev_ref_count == 1); // this should be the last reference
+        DeepFactory::DeleteDeepObject(L_, linda_);
+    }
+}
+
+// #################################################################################################
+
 void Linda::freeAllocatedName()
 {
     if (std::holds_alternative<std::string_view>(nameVariant)) {
diff --git a/src/linda.hpp b/src/linda.hpp
index aa63316..920db1b 100644
--- a/src/linda.hpp
+++ b/src/linda.hpp
@@ -82,6 +82,9 @@ class Linda
     Linda& operator=(Linda const&&) = delete;
 
     private:
+    [[nodiscard]]
+    static Linda* CreateTimerLinda(lua_State* L_);
+    static void DeleteTimerLinda(lua_State* L_, Linda* linda_);
     void freeAllocatedName();
     void setName(std::string_view const& name_);
 
@@ -89,6 +92,9 @@ class Linda
     [[nodiscard]]
     Keeper* acquireKeeper() const;
     [[nodiscard]]
+    static Linda* CreateTimerLinda(lua_State* const L_, Passkey<Universe>) { return CreateTimerLinda(L_); }
+    static void DeleteTimerLinda(lua_State* const L_, Linda* const linda_, Passkey<Universe>) { DeleteTimerLinda(L_, linda_); }
+    [[nodiscard]]
     std::string_view getName() const;
     [[nodiscard]]
     bool inKeeperOperation() const { return keeperOperationCount.load(std::memory_order_seq_cst) != 0; }
diff --git a/src/macros_and_utils.hpp b/src/macros_and_utils.hpp
index 6850ddf..0897367 100644
--- a/src/macros_and_utils.hpp
+++ b/src/macros_and_utils.hpp
@@ -47,3 +47,16 @@ typename T::value_type const& OptionalValue(T const& x_, Ts... args_)
     }
     return x_.value();
 }
+
+// #################################################################################################
+
+struct PasskeyToken {};
+constexpr PasskeyToken PK{};
+template <typename T>
+class Passkey
+{
+    private:
+    friend T;
+    Passkey(PasskeyToken) {}
+    // rule of 5 ignored out of laziness here
+};
diff --git a/src/universe.cpp b/src/universe.cpp
index ec7d043..b7d11d8 100644
--- a/src/universe.cpp
+++ b/src/universe.cpp
@@ -35,6 +35,7 @@ THE SOFTWARE.
 #include "intercopycontext.hpp"
 #include "keeper.hpp"
 #include "lane.hpp"
+#include "linda.hpp"
 #include "state.hpp"
 
 extern LUAG_FUNC(linda);
@@ -147,7 +148,7 @@ Universe* Universe::Create(lua_State* const L_)
     DEBUGSPEW_CODE(DebugSpewIndentScope _scope{ _U });
     lua_createtable(L_, 0, 1);                                                                     // L_: settings universe {mt}
     std::ignore = luaG_getfield(L_, kIdxSettings, "shutdown_timeout");                             // L_: settings universe {mt} shutdown_timeout
-    lua_pushcclosure(L_, LG_universe_gc, 1);                                                       // L_: settings universe {mt} LG_universe_gc
+    lua_pushcclosure(L_, UniverseGC, 1);                                                           // L_: settings universe {mt} UniverseGC
     lua_setfield(L_, -2, "__gc");                                                                  // L_: settings universe {mt}
     lua_setmetatable(L_, -2);                                                                      // L_: settings universe
     lua_pop(L_, 1);                                                                                // L_: settings
@@ -175,18 +176,7 @@ Universe* Universe::Create(lua_State* const L_)
     STACK_CHECK(L_, 0);
 
     // Initialize 'timerLinda'; a common Linda object shared by all states
-    lua_pushcfunction(L_, LG_linda);                                                               // L_: settings lanes.linda
-    luaG_pushstring(L_, "lanes-timer");                                                            // L_: settings lanes.linda "lanes-timer"
-    lua_pushinteger(L_, 0);                                                                        // L_: settings lanes.linda "lanes-timer" 0
-    lua_call(L_, 2, 1);                                                                            // L_: settings linda
-    STACK_CHECK(L_, 1);
-
-    // Proxy userdata contents is only a 'DeepPrelude*' pointer
-    _U->timerLinda = *luaG_tofulluserdata<DeepPrelude*>(L_, kIdxTop);
-    // increment refcount so that this linda remains alive as long as the universe exists.
-    _U->timerLinda->refcount.fetch_add(1, std::memory_order_relaxed);
-    lua_pop(L_, 1);                                                                                // L_: settings
-    STACK_CHECK(L_, 0);
+    _U->timerLinda = Linda::CreateTimerLinda(L_, PK);
     return _U;
 }
 
@@ -409,7 +399,7 @@ bool Universe::terminateFreeRunningLanes(lua_Duration const shutdownTimeout_, Ca
 // #################################################################################################
 
 // process end: cancel any still free-running threads
-LUAG_FUNC(universe_gc)
+int Universe::UniverseGC(lua_State* const L_)
 {
     lua_Duration const _shutdown_timeout{ lua_tonumber(L_, lua_upvalueindex(1)) };
     STACK_CHECK_START_ABS(L_, 1);
@@ -444,12 +434,7 @@ LUAG_FUNC(universe_gc)
     }
 
     // no need to mutex-protect this as all lanes in the universe are gone at that point
-    if (_U->timerLinda != nullptr) { // test in case some early internal error prevented Lanes from creating the deep timer
-        [[maybe_unused]] int const _prev_ref_count{ _U->timerLinda->refcount.fetch_sub(1, std::memory_order_relaxed) };
-        LUA_ASSERT(L_, _prev_ref_count == 1); // this should be the last reference
-        DeepFactory::DeleteDeepObject(L_, _U->timerLinda);
-        _U->timerLinda = nullptr;
-    }
+    Linda::DeleteTimerLinda(L_, std::exchange(_U->timerLinda, nullptr), PK);
 
     _U->keepers.close();
 
diff --git a/src/universe.hpp b/src/universe.hpp
index 639dcdb..dbf0ece 100644
--- a/src/universe.hpp
+++ b/src/universe.hpp
@@ -10,8 +10,8 @@
 // #################################################################################################
 
 // forwards
-struct DeepPrelude;
 class Lane;
+class Linda;
 
 // #################################################################################################
 
@@ -99,7 +99,7 @@ class Universe
 
     // Initialized by 'init_once_LOCKED()': the deep userdata Linda object
     // used for timers (each lane will get a proxy to this)
-    DeepPrelude* timerLinda{ nullptr };
+    Linda* timerLinda{ nullptr };
 
     LaneTracker tracker;
 
@@ -122,6 +122,9 @@ class Universe
     // The terminal desinit sequence should wait for all such processing to terminate before force-killing threads
     std::atomic<int> selfdestructingCount{ 0 };
 
+    private:
+    static int UniverseGC(lua_State* L_);
+
     public:
     [[nodiscard]]
     static void* operator new([[maybe_unused]] size_t size_, lua_State* L_) noexcept { return luaG_newuserdatauv<Universe>(L_, UserValueCount{ 0 }); };
@@ -171,7 +174,3 @@ inline void Universe::Store(lua_State* L_, Universe* U_)
     kUniverseLightRegKey.setValue(L_, [U = U_](lua_State* L_) { U ? lua_pushlightuserdata(L_, U) : lua_pushnil(L_); });
     STACK_CHECK(L_, 0);
 }
-
-// #################################################################################################
-
-LUAG_FUNC(universe_gc);