refactor: put the loadstring cstring on the stack, so it can be easily reclaimed

Author: YoRyan

scripts/build.sh

@@ -20,7 +20,7 @@ cd ../..
 if [[ "$1" == "lua-5.0.3" ]]; then
     emcc -Ithirdparty/$1 thirdparty/$1/lib/liblua.a thirdparty/$1/lib/liblualib.a \
         -s WASM=1 -O3 -o dist/glue/glue-$1.js \
-        -s EXPORTED_RUNTIME_METHODS="['cwrap', 'allocateUTF8', 'lengthBytesUTF8']" \
+        -s EXPORTED_RUNTIME_METHODS="['cwrap', 'stackSave', 'stackRestore', 'lengthBytesUTF8', 'allocateUTF8OnStack']" \
         -s MODULARIZE=1 \
         -s ALLOW_TABLE_GROWTH \
         -s EXPORT_NAME="glue" \

src/binding-factory.ts

@@ -165,8 +165,11 @@ const lauxBindings: Record<string, lauxBindingFactoryFunc> = {
                 return (this as LauxLib).luaL_loadstring(L, s) || lua.lua_pcall(L, 0, LUA_MULTRET, 0);
             },
             luaL_loadstring: function(L: LuaState, s: string) {
-                const ptr = luaGlue.allocateUTF8(s) as unknown;
-                return (this as LauxLib).luaL_loadbuffer(L, ptr as string, luaGlue.lengthBytesUTF8(s), s);
+                const lastStack = luaGlue.stackSave();
+                const cstr = luaGlue.allocateUTF8OnStack(s) as unknown;
+                const result = (this as LauxLib).luaL_loadbuffer(L, cstr as string, luaGlue.lengthBytesUTF8(s), s);
+                luaGlue.stackRestore(lastStack);
+                return result;
             },
             // Note that s has a "number" type, so we can pass a raw pointer
             luaL_loadbuffer: luaGlue.cwrap("luaL_loadbuffer", "number", ["number", "number", "number", "string"]),

src/glue/glue.ts

@@ -1,7 +1,9 @@
 export interface LuaEmscriptenModule extends EmscriptenModule {
-    allocateUTF8: typeof allocateUTF8;
-    lengthBytesUTF8: typeof lengthBytesUTF8;
     cwrap: typeof cwrap;
+    stackSave: typeof stackSave;
+    stackRestore: typeof stackRestore;
+    lengthBytesUTF8: typeof lengthBytesUTF8;
+    allocateUTF8OnStack: typeof allocateUTF8;
 }
 
 export type EmscriptenModuleFactorySync<T extends EmscriptenModule = EmscriptenModule> = (