From 706cabeebddb414be5537873d95f9a8c57fd425b Mon Sep 17 00:00:00 2001
From: MihailRis <mexaruc@gmail.com>
Date: Sun, 18 Aug 2024 23:26:37 +0300
Subject: [PATCH] add lua::stackguard

---
 src/logic/scripting/lua/lua_commons.hpp       | 24 +++++++++++++++++--
 .../scripting/scripting_world_generation.cpp  |  3 +--
 2 files changed, 23 insertions(+), 4 deletions(-)

diff --git a/src/logic/scripting/lua/lua_commons.hpp b/src/logic/scripting/lua/lua_commons.hpp
index d0b99f67..ff94ade7 100644
--- a/src/logic/scripting/lua/lua_commons.hpp
+++ b/src/logic/scripting/lua/lua_commons.hpp
@@ -24,9 +24,29 @@ namespace lua {
         luaerror(const std::string& message);
     };
 
-    void log_error(const std::string& text);
-
     using State = lua_State;
     using Number = lua_Number;
     using Integer = lua_Integer;
+
+    /// @brief Automatically resets stack top element index to the initial state
+    /// (when stackguard was created). Prevents Lua stack leak on exception
+    /// occurred out of Lua execution time, when engine controls scripting.
+    ///
+    ///
+    /// stackguard allows to not place lua::pop(...) into 'catch' blocks.
+    class stackguard {
+        int top;
+        State* state;
+    public:
+        stackguard(State* state) : state(state) {
+            top = lua_gettop(state);
+        }
+
+        ~stackguard() {
+            lua_settop(state, top);
+        }
+    };
+
+    void log_error(const std::string& text);
+
 }
diff --git a/src/logic/scripting/scripting_world_generation.cpp b/src/logic/scripting/scripting_world_generation.cpp
index 712aaa13..a1abee83 100644
--- a/src/logic/scripting/scripting_world_generation.cpp
+++ b/src/logic/scripting/scripting_world_generation.cpp
@@ -101,7 +101,6 @@ static inline BlocksLayers load_layers(
                 layers.push_back(
                     load_layer(L, -1, lastLayersHeight, hasResizeableLayer));
             } catch (const std::runtime_error& err) {
-                lua::pop(L, 2);
                 throw std::runtime_error(
                     fieldname+" #"+std::to_string(i)+": "+err.what());
             }
@@ -117,6 +116,7 @@ std::unique_ptr<GeneratorScript> scripting::load_generator(
 ) {
     auto env = create_environment();
     auto L = lua::get_main_thread();
+    lua::stackguard _(L);
 
     lua::pop(L, load_script(*env, "generator", file));
 
@@ -139,7 +139,6 @@ std::unique_ptr<GeneratorScript> scripting::load_generator(
         groundLayers = load_layers(L, "layers");
         seaLayers = load_layers(L, "sea_layers");
     } catch (const std::runtime_error& err) {
-        lua::pop(L);
         throw std::runtime_error(file.u8string()+": "+err.what());
     }
     lua::pop(L);