From 06d197cdd042392e1551e5e7244c61300a6bb4e3 Mon Sep 17 00:00:00 2001
From: Jude Melton-Houghton <jwmhjwmh@gmail.com>
Date: Tue, 29 Mar 2022 12:07:00 -0400
Subject: Store vector metatable in registry

---
 src/script/common/c_converter.cpp | 19 +++----------------
 src/script/common/c_internal.h    |  1 +
 src/script/cpp_api/s_base.cpp     |  8 ++++++++
 src/script/cpp_api/s_security.cpp |  6 ++++++
 4 files changed, 18 insertions(+), 16 deletions(-)

(limited to 'src')

diff --git a/src/script/common/c_converter.cpp b/src/script/common/c_converter.cpp
index 08fb9ad30..b5ff52f73 100644
--- a/src/script/common/c_converter.cpp
+++ b/src/script/common/c_converter.cpp
@@ -52,25 +52,12 @@ if (value < F1000_MIN || value > F1000_MAX) { \
 
 
 /**
- * A helper which sets (if available) the vector metatable from builtin as metatable
- * for the table on top of the stack
+ * A helper which sets the vector metatable for the table on top of the stack
  */
 static void set_vector_metatable(lua_State *L)
 {
-	// get vector.metatable
-	lua_getglobal(L, "vector");
-	if (!lua_istable(L, -1)) {
-		// there is no global vector table
-		lua_pop(L, 1);
-		errorstream << "set_vector_metatable in c_converter.cpp: " <<
-				"missing global vector table" << std::endl;
-		return;
-	}
-	lua_getfield(L, -1, "metatable");
-	// set the metatable
-	lua_setmetatable(L, -3);
-	// pop vector global
-	lua_pop(L, 1);
+	lua_rawgeti(L, LUA_REGISTRYINDEX, CUSTOM_RIDX_VECTOR_METATABLE);
+	lua_setmetatable(L, -2);
 }
 
 void push_v3f(lua_State *L, v3f p)
diff --git a/src/script/common/c_internal.h b/src/script/common/c_internal.h
index 94cfd61fb..c43db34aa 100644
--- a/src/script/common/c_internal.h
+++ b/src/script/common/c_internal.h
@@ -55,6 +55,7 @@ extern "C" {
 #define CUSTOM_RIDX_CURRENT_MOD_NAME    (CUSTOM_RIDX_BASE + 2)
 #define CUSTOM_RIDX_BACKTRACE           (CUSTOM_RIDX_BASE + 3)
 #define CUSTOM_RIDX_HTTP_API_LUA        (CUSTOM_RIDX_BASE + 4)
+#define CUSTOM_RIDX_VECTOR_METATABLE    (CUSTOM_RIDX_BASE + 5)
 
 
 // Determine if CUSTOM_RIDX_SCRIPTAPI will hold a light or full userdata
diff --git a/src/script/cpp_api/s_base.cpp b/src/script/cpp_api/s_base.cpp
index f7b8a5102..595c9e540 100644
--- a/src/script/cpp_api/s_base.cpp
+++ b/src/script/cpp_api/s_base.cpp
@@ -121,6 +121,14 @@ ScriptApiBase::ScriptApiBase(ScriptingType type):
 	lua_newtable(m_luastack);
 	lua_setglobal(m_luastack, "core");
 
+	// vector.metatable is stored in the registry for quick access from C++.
+	lua_newtable(m_luastack);
+	lua_rawseti(m_luastack, LUA_REGISTRYINDEX, CUSTOM_RIDX_VECTOR_METATABLE);
+	lua_newtable(m_luastack);
+	lua_rawgeti(m_luastack, LUA_REGISTRYINDEX, CUSTOM_RIDX_VECTOR_METATABLE);
+	lua_setfield(m_luastack, -2, "metatable");
+	lua_setglobal(m_luastack, "vector");
+
 	if (m_type == ScriptingType::Client)
 		lua_pushstring(m_luastack, "/");
 	else
diff --git a/src/script/cpp_api/s_security.cpp b/src/script/cpp_api/s_security.cpp
index a6c5114b2..f68cd1777 100644
--- a/src/script/cpp_api/s_security.cpp
+++ b/src/script/cpp_api/s_security.cpp
@@ -98,6 +98,7 @@ void ScriptApiSecurity::initializeSecurity()
 		"type",
 		"unpack",
 		"_VERSION",
+		"vector",
 		"xpcall",
 	};
 	static const char *whitelist_tables[] = {
@@ -254,6 +255,10 @@ void ScriptApiSecurity::initializeSecurity()
 	lua_pushnil(L);
 	lua_setfield(L, old_globals, "core");
 
+	// 'vector' as well.
+	lua_pushnil(L);
+	lua_setfield(L, old_globals, "vector");
+
 	lua_pop(L, 1); // Pop globals_backup
 
 
@@ -296,6 +301,7 @@ void ScriptApiSecurity::initializeSecurityClient()
 		"type",
 		"unpack",
 		"_VERSION",
+		"vector",
 		"xpcall",
 		// Completely safe libraries
 		"coroutine",
-- 
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