Update behavior of luaL_tolstring().

1 files changed, 10 insertions, 3 deletions

diff --git a/c-api/compat-5.3.c b/c-api/compat-5.3.c
index b913196..1e985f9 100644
--- a/c-api/compat-5.3.c
+++ b/c-api/compat-5.3.c
@@ -238,7 +238,8 @@ COMPAT53_API void *luaL_testudata (lua_State *L, int i, const char *tname) {
 
 COMPAT53_API const char *luaL_tolstring (lua_State *L, int idx, size_t *len) {
   if (!luaL_callmeta(L, idx, "__tostring")) {
-    int t = lua_type(L, idx);
+    int t = lua_type(L, idx), tt = 0;
+    char const* name = NULL;
     switch (t) {
       case LUA_TNIL:
         lua_pushliteral(L, "nil");
@@ -254,10 +255,16 @@ COMPAT53_API const char *luaL_tolstring (lua_State *L, int idx, size_t *len) {
           lua_pushliteral(L, "false");
         break;
       default:
-        lua_pushfstring(L, "%s: %p", lua_typename(L, t),
-                                     lua_topointer(L, idx));
+        tt = luaL_getmetafield(L, idx, "__name");
+        name = (tt == LUA_TSTRING) ? lua_tostring(L, -1) : lua_typename(L, t);
+        lua_pushfstring(L, "%s: %p", name, lua_topointer(L, idx));
+        if (tt != LUA_TNIL)
+          lua_replace(L, -2);
         break;
     }
+  } else {
+    if (!lua_isstring(L, -1))
+      luaL_error(L, "'__tostring' must return a string");
   }
   return lua_tolstring(L, -1, len);
 }