Fix lanes.nameof() crashing when encountering a light userdata

1 files changed, 20 insertions, 12 deletions

diff --git a/src/tools.c b/src/tools.c
index 95104d6..f445068 100644
--- a/src/tools.c
+++ b/src/tools.c
@@ -1359,12 +1359,12 @@ static int discover_object_name_recur( lua_State* L, int shortest_, int depth_)
         lua_pushinteger( L, 1);                                 // o "r" {c} {fqn} ... {?} {?} 1
         lua_rawset( L, cache);                                  // o "r" {c} {fqn} ... {?}
         // scan table contents
-        STACK_CHECK( L);
         lua_pushnil( L);                                        // o "r" {c} {fqn} ... {?} nil
         while( lua_next( L, -2))                                // o "r" {c} {fqn} ... {?} k v
         {
                 //char const *const strKey = (lua_type( L, -2) == LUA_TSTRING) ? lua_tostring( L, -2) : NULL; // only for debugging
                 //lua_Number const numKey = (lua_type( L, -2) == LUA_TNUMBER) ? lua_tonumber( L, -2) : -6666; // only for debugging
+                STACK_MID( L, 2);
                 // append key name to fqn stack
                 ++ depth_;
                 lua_pushvalue( L, -2);                                // o "r" {c} {fqn} ... {?} k v k
@@ -1384,8 +1384,12 @@ static int discover_object_name_recur( lua_State* L, int shortest_, int depth_)
                         STACK_MID( L, 0);
                         break;
                 }
-                else if( lua_istable( L, -1))                         // o "r" {c} {fqn} ... {?} k {}
+                switch( lua_type( L, -1))                             // o "r" {c} {fqn} ... {?} k v
                 {
+                        default: // nil, boolean, light userdata, number and string aren't identifiable
+                        break;
+
+                        case LUA_TTABLE:                                    // o "r" {c} {fqn} ... {?} k {}
                         STACK_MID( L, 2);
                         shortest_ = discover_object_name_recur( L, shortest_, depth_);
                         // search in the table's metatable too
@@ -1402,11 +1406,11 @@ static int discover_object_name_recur( lua_State* L, int shortest_, int depth_)
                                         -- depth_;
                                 }
                                 lua_pop( L, 1);                                   // o "r" {c} {fqn} ... {?} k {}
-                                STACK_MID( L, 2);
                         }
-                }
-                else if( lua_isthread( L, -1))                        // o "r" {c} {fqn} ... {?} k T
-                {
+                        STACK_MID( L, 2);
+                        break;
+
+                        case LUA_TTHREAD:                                   // o "r" {c} {fqn} ... {?} k T
                         // search in the object's uservalue if it is a table
                         lua_getuservalue( L, -1);                           // o "r" {c} {fqn} ... {?} k T {u}
                         if( lua_istable( L, -1))
@@ -1415,9 +1419,9 @@ static int discover_object_name_recur( lua_State* L, int shortest_, int depth_)
                         }
                         lua_pop( L, 1);                                     // o "r" {c} {fqn} ... {?} k T
                         STACK_MID( L, 2);
-                }
-                else if( lua_isuserdata( L, -1))                      // o "r" {c} {fqn} ... {?} k U
-                {
+                        break;
+
+                        case LUA_TUSERDATA:                                 // o "r" {c} {fqn} ... {?} k U
                         STACK_MID( L, 2);
                         // search in the object's metatable (some modules are built that way)
                         if( lua_getmetatable( L, -1))                       // o "r" {c} {fqn} ... {?} k U {mt}
@@ -1433,8 +1437,8 @@ static int discover_object_name_recur( lua_State* L, int shortest_, int depth_)
                                         -- depth_;
                                 }
                                 lua_pop( L, 1);                                   // o "r" {c} {fqn} ... {?} k U
-                                STACK_MID( L, 2);
                         }
+                        STACK_MID( L, 2);
                         // search in the object's uservalue if it is a table
                         lua_getuservalue( L, -1);                           // o "r" {c} {fqn} ... {?} k U {u}
                         if( lua_istable( L, -1))
@@ -1449,15 +1453,17 @@ static int discover_object_name_recur( lua_State* L, int shortest_, int depth_)
                         }
                         lua_pop( L, 1);                                     // o "r" {c} {fqn} ... {?} k U
                         STACK_MID( L, 2);
+                        break;
                 }
                 // make ready for next iteration
                 lua_pop( L, 1);                                       // o "r" {c} {fqn} ... {?} k
                 // remove name from fqn stack
                 lua_pushnil( L);                                      // o "r" {c} {fqn} ... {?} k nil
                 lua_rawseti( L, fqn, depth_);                         // o "r" {c} {fqn} ... {?} k
+                STACK_MID( L, 1);
                 -- depth_;
         }                                                       // o "r" {c} {fqn} ... {?}
-        STACK_END( L, 0);
+        STACK_MID( L, 0);
         // remove the visited table from the cache, in case a shorter path to the searched object exists
         lua_pushvalue( L, -1);                                  // o "r" {c} {fqn} ... {?} {?}
         lua_pushnil( L);                                        // o "r" {c} {fqn} ... {?} {?} nil
@@ -1477,7 +1483,7 @@ int luaG_nameof( lua_State* L)
                 luaL_argerror( L, what, "too many arguments.");
         }
 
-        // numbers, strings, booleans and nil can't be identified
+        // nil, boolean, light userdata, number and string aren't identifiable
         if( lua_type( L, 1) < LUA_TTABLE)
         {
                 lua_pushstring( L, luaL_typename( L, 1));             // o "type"
@@ -1486,6 +1492,7 @@ int luaG_nameof( lua_State* L)
         }
 
         STACK_GROW( L, 4);
+        STACK_CHECK( L);
         // this slot will contain the shortest name we found when we are done
         lua_pushnil( L);                                        // o nil
         // push a cache that will contain all already visited tables
@@ -1496,6 +1503,7 @@ int luaG_nameof( lua_State* L)
         lua_pushglobaltable( L);                                // o nil {c} {fqn} _G
         (void) discover_object_name_recur( L, 6666, 0);
         lua_pop( L, 3);                                         // o "result"
+        STACK_END( L, 1);
         lua_pushstring( L, luaL_typename( L, 1));               // o "result" "type"
         lua_replace( L, -3);                                    // "type" "result"
         return 2;