1 files changed, 8 insertions, 5 deletions

diff --git a/src/keeper.c b/src/keeper.c
index 7eda598..05e9a02 100644
--- a/src/keeper.c
+++ b/src/keeper.c
@@ -65,6 +65,8 @@ typedef struct
         lua_Integer limit;
 } keeper_fifo;
 
+static int const CONTENTS_TABLE = 1;
+
 // replaces the fifo ud by its uservalue on the stack
 static keeper_fifo* prepare_fifo_access( lua_State* L, int idx_)
 {
@@ -74,7 +76,7 @@ static keeper_fifo* prepare_fifo_access( lua_State* L, int idx_)
                 idx_ = lua_absindex( L, idx_);
                 STACK_GROW( L, 1);
                 // we can replace the fifo userdata in the stack without fear of it being GCed, there are other references around
-                lua_getuservalue( L, idx_);
+                lua_getiuservalue( L, idx_, CONTENTS_TABLE);
                 lua_replace( L, idx_);
         }
         return fifo;
@@ -86,12 +88,13 @@ static void fifo_new( lua_State* L)
 {
         keeper_fifo* fifo;
         STACK_GROW( L, 2);
-        fifo = (keeper_fifo*) lua_newuserdata( L, sizeof( keeper_fifo));
+        // a fifo full userdata has one uservalue, the table that holds the actual fifo contents
+        fifo = (keeper_fifo*)lua_newuserdatauv( L, sizeof( keeper_fifo), 1);
         fifo->first = 1;
         fifo->count = 0;
         fifo->limit = -1;
         lua_newtable( L);
-        lua_setuservalue( L, -2);
+        lua_setiuservalue( L, -2, CONTENTS_TABLE);
 }
 
 // in: expect fifo ... on top of the stack
@@ -422,7 +425,7 @@ int keepercall_set( lua_State* L)
                                 should_wake_writers = (fifo->limit > 0) && (fifo->count >= fifo->limit);
                                 lua_remove( L, -2);                         // fifos fifo
                                 lua_newtable( L);                           // fifos fifo {}
-                                lua_setuservalue( L, -2);                   // fifos fifo
+                                lua_setiuservalue( L, -2, CONTENTS_TABLE);  // fifos fifo
                                 fifo->first = 1;
                                 fifo->count = 0;
                         }
@@ -450,7 +453,7 @@ int keepercall_set( lua_State* L)
                         should_wake_writers = (fifo->limit > 0) && (fifo->count >= fifo->limit) && (count < fifo->limit);
                         // empty the fifo for the specified key: replace uservalue with a virgin table, reset counters, but leave limit unchanged!
                         lua_newtable( L);                             // fifos key [val [, ...]] fifo {}
-                        lua_setuservalue( L, -2);                     // fifos key [val [, ...]] fifo
+                        lua_setiuservalue( L, -2, CONTENTS_TABLE);    // fifos key [val [, ...]] fifo
                         fifo->first = 1;
                         fifo->count = 0;
                 }