Change how class tables are created and recreated for greater robustness

luprex/cpp/core/luastack.cpp

@@ -75,7 +75,20 @@ static void *l_alloc(void *ud, void *ptr, size_t osize, size_t nsize) {
 lua_State *LuaStack::newstate (lua_Alloc allocf) {
     if (allocf == nullptr) allocf = l_alloc;
     lua_State *L = lua_newstate(allocf, NULL);
-    if (L) lua_atpanic(L, &panicf);
+    assert(L != nullptr);
+    lua_atpanic(L, &panicf);
+
+    // We want all states to have a classes table and
+    // a tangibles table so that LS.makeclass and LS.maketan
+    // work out-of-the-box.
+
+    lua_pushstring(L, "classes");
+    lua_newtable(L);
+    lua_rawset(L, LUA_REGISTRYINDEX);
+    lua_pushstring(L, "tangibles");
+    lua_newtable(L);
+    lua_rawset(L, LUA_REGISTRYINDEX);
+
     return L;
 }
 
@@ -256,27 +269,35 @@ bool LuaStack::validclassname(LuaSlot slot) const {
 
 eng::string LuaStack::classname(LuaSlot tab) const {
     eng::string result;
-    if (istable(tab)) {
+    if ((istable(tab)) && (gettabletype(tab) == LUA_TT_CLASS)) {
-        lua_pushstring(L_, "__class");
+        LuaVar classes, name, dup;
-        lua_rawget(L_, tab);
+        LuaStack LS(L_, classes, name, dup);
-        if (lua_type(L_, -1) == LUA_TSTRING) {
+        // Get the classes table from the registry.
-            lua_pushglobaltable(L_); // cname table
+        LS.rawget(classes, LuaRegistry, "classes");
-            lua_pushvalue(L_, -2); // cname table cname
+
-            lua_rawget(L_, -2); // cname table ctab
+        // Try the efficient approach: get the class name from
-            if (lua_rawequal(L_, -1, tab)) {
+        // the class, and confirm it by checking the classes table.
-                size_t len;
+        LS.rawget(name, tab, "__class");
-                const char *s = lua_tolstring(L_, -3, &len);
+        if (LS.isstring(name)) {
-                result = eng::string(s, len);
+            LS.rawget(dup, classes, name);
-                if (!validclassname(result)) {
+            if (LS.rawequal(dup, tab)) {
-                    result = "";
+                result = LS.ckstring(name);
-                }
+                LS.result();
+                return result;
+            }
+        }
+
+        // Do it the brute force way: scan the classes table.
+        LS.set(name, LuaNil);
+        while (LS.next(classes, name, dup)) {
+            if (LS.rawequal(dup, tab)) {
+                result = LS.ckstring(name);
+                LS.result();
+                return result;
             }
-            lua_pop(L_, 3);
-        } else {
-            lua_pop(L_, 1);
         }
     }
-    return result;
+    return "";
 }
 
 eng::string LuaStack::getclass(LuaSlot classtab, LuaSlot classname) const {
@@ -342,24 +363,31 @@ eng::string LuaStack::getclass(LuaSlot tab, std::string_view name) const {
 
 void LuaStack::makeclass(LuaSlot classtab, LuaSlot classname) const {
     lua_checkstack(L_, 20);
-    LuaVar globtab, cname;
+    LuaVar classes, globtab, cname;
-    LuaStack LS(L_, globtab, cname);
+    LuaStack LS(L_, classes, globtab, cname);
 
     // Validate the class name.
     assert(LS.validclassname(classname));
     
+    // Fetch the classes table from the registry.
+    LS.rawget(classes, LuaRegistry, "classes");
+    assert(LS.istable(classes));
+
     // Fetch the global environment from the registry.
     LS.getglobaltable(globtab);
     
-    // Get the classtab from the global environment.
+    // Get the classtab from the classes table.
-    LS.rawget(classtab, globtab, classname);
+    LS.rawget(classtab, classes, classname);
 
     // Make a new table if necessary.
     if (!LS.istable(classtab)) {
         LS.newtable(classtab);
-        LS.rawset(globtab, classname, classtab);
+        LS.rawset(classes, classname, classtab);
     }
     
+    // Put the table into the global environment.
+    LS.rawset(globtab, classname, classtab);
+
     // Repair the special fields.
     LS.settabletype(classtab, LUA_TT_CLASS);
     LS.rawset(classtab, "__class", classname);

luprex/cpp/core/luastack.hpp

@@ -458,9 +458,11 @@ public:
     void makeclass(LuaSlot tab, std::string_view name) const;
 
     // Create a tangible, or look up an existing tangible.
-    // This doesn't do the entire process of tangible creation.  It
+    // If the tangible doesn't exist yet, this creates a tangible stub.
-    // just creates an empty table, marks it as a tangible, creates
+    // It is possible to use World::tangible_make to transform a tangible
-    // the metatable, stores the tangible ID, and stores it in the tangible table.
+    // stub into a full blown tangible, and World::tangible_delete to turn
+    // a full-blown tangible back into a stub.  A stub doesn't have a
+    // class or a thread table.
     void maketan(LuaSlot tab, int64_t id) const;
 
     // Return true if a tangible is empty (deleted or not yet created).

luprex/cpp/core/source.cpp

@@ -245,26 +245,24 @@ void SourceDB::update(const util::LuaSourceVec &source) {
     LS.result();
 }
 
-// Delete everything from the global environment except
+// Delete everything from the global environment.
-// the class tables.
+// Clear all the classes in the registry classes table.
 //
 static void source_clear_globals(lua_State *L) {
-    LuaVar classname, classtab, key, globtab;
+    LuaVar classname, classtab, key, globtab, classes;
-    LuaStack LS(L, classname, classtab, key, globtab);
+    LuaStack LS(L, classname, classtab, key, globtab, classes);
 
     LS.getglobaltable(globtab);
-    LS.rawset(globtab, "_G", LuaNil);
+    LS.cleartable(globtab, true);
-    LS.set(classname, LuaNil);
-    while (LS.next(globtab, classname, classtab) != 0) {
-        if (LS.rawequal(globtab, classtab)) {
-            LS.rawset(globtab, classname, LuaNil);
-        } else if (LS.istable(classtab)) {
-            LS.cleartable(classtab, true);
-        } else {
-            LS.rawset(globtab, classname, LuaNil);
-        }
-    }
     LS.rawset(globtab, "_G", globtab);
+
+    LS.rawget(classes, LuaRegistry, "classes");
+    assert(LS.istable(classes));
+    LS.set(classname, LuaNil);
+    while (LS.next(classes, classname, classtab) != 0) {
+        assert(LS.istable(classtab));
+        LS.cleartable(classtab, true);
+    }
     LS.result();
 }
 

luprex/cpp/core/world-core.cpp

@@ -60,9 +60,6 @@ World::World(WorldType wt) {
     LS.getglobaltable(globtab);
     LS.settabletype(globtab, LUA_TT_GLOBALENV);
 
-    // Create the tangibles table in the registry.
-    LS.rawset(LuaRegistry, "tangibles", LuaNewTable);
-
     // Store the world type in the registry.
     LS.rawset(LuaRegistry, "worldtype", wt);
         
@@ -592,7 +589,7 @@ void World::invoke_flush_prints(int64_t actor_id, int64_t place_id, const eng::s
 void World::invoke_lua(int64_t actor_id, int64_t place_id, const eng::string &action, const InvocationData &data) {
     assert(stack_is_clear());
 
-    // Make sure that actor and place exist.
+    // Make sure that actor and place exist and are not stubs.
     Tangible *tactor = tangible_get(actor_id);
     Tangible *tplace = tangible_get(place_id);
     if ((tactor == nullptr) || (tplace == nullptr)) {