new config option demote_full_userdata

use demote_full_userdata to select between light userdata demotion or
raising an error when attempting to transfer a non-deep full userdata

2 files changed, 38 insertions, 37 deletions

diff --git a/src/lanes.lua b/src/lanes.lua
index 6e2a736..4856a2d 100644
--- a/src/lanes.lua
+++ b/src/lanes.lua
@@ -71,52 +71,34 @@ lanes.configure = function( settings_)
                 shutdown_timeout = 0.25,
                 with_timers = true,
                 track_lanes = false,
+                demote_full_userdata = nil,
                 verbose_errors = false,
                 -- LuaJIT provides a thread-unsafe allocator by default, so we need to protect it when used in parallel lanes
                 protect_allocator = (jit and jit.version) and true or false
         }
+        local boolean_param_checker = function( val_)
+                -- non-'boolean-false' should be 'boolean-true' or nil
+                return val_ and (val_ == true) or true
+        end
         local param_checkers =
         {
-                nb_keepers = function( _val)
+                nb_keepers = function( val_)
                         -- nb_keepers should be a number > 0
-                        return type( _val) == "number" and _val > 0
-                end,
-                with_timers = function( _val)
-                        -- with_timers may be nil or boolean
-                        if _val then
-                                return type( _val) == "boolean"
-                        else
-                                return true -- _val is either false or nil
-                        end
+                        return type( val_) == "number" and val_ > 0
                 end,
-                protect_allocator = function( _val)
-                        -- protect_allocator may be nil or boolean
-                        if _val then
-                                return type( _val) == "boolean"
-                        else
-                                return true -- _val is either false or nil
-                        end
-                end,
-                on_state_create = function( _val)
+                with_timers = boolean_param_checker,
+                protect_allocator = boolean_param_checker,
+                on_state_create = function( val_)
                         -- on_state_create may be nil or a function
-                        return _val and type( _val) == "function" or true
+                        return val_ and type( val_) == "function" or true
                 end,
-                shutdown_timeout = function( _val)
+                shutdown_timeout = function( val_)
                         -- shutdown_timeout should be a number >= 0
-                        return type( _val) == "number" and _val >= 0
-                end,
-                track_lanes = function( _val)
-                        -- track_lanes may be nil or boolean
-                        return _val and type( _val) == "boolean" or true
+                        return type( val_) == "number" and val_ >= 0
                 end,
-                verbose_errors = function( _val)
-                        -- verbose_errors may be nil or boolean
-                        if _val then
-                                return type( _val) == "boolean"
-                        else
-                                return true -- _val is either false or nil
-                        end
-                end
+                track_lanes = boolean_param_checker,
+                demote_full_userdata = boolean_param_checker,
+                verbose_errors = boolean_param_checker
         }
 
         local params_checker = function( settings_)
diff --git a/src/tools.c b/src/tools.c
index b5f2f4b..e743393 100644
--- a/src/tools.c
+++ b/src/tools.c
@@ -1886,9 +1886,28 @@ static bool_t inter_copy_one_( lua_State* L2, uint_t L2_cache_i, lua_State* L, u
                 DEBUGSPEW_CODE( fprintf( stderr, INDENT_BEGIN "USERDATA\n" INDENT_END));
                 if( !luaG_copydeep( L, L2, i))
                 {
-                        // Cannot copy it full; copy as light userdata
-                        //
-                        lua_pushlightuserdata( L2, lua_touserdata( L, i));
+                        // Not a deep full userdata
+                        bool_t demote = FALSE;
+                        lua_getfield( L, LUA_REGISTRYINDEX, CONFIG_REGKEY);
+                        if( lua_istable( L, -1)) // should not happen, but who knows...
+                        {
+                                lua_getfield( L, -1, "demote_full_userdata");
+                                demote = lua_toboolean( L, -1);
+                                lua_pop( L, 2);
+                        }
+                        else
+                        {
+                                lua_pop( L, 1);
+                        }
+                        if( demote) // attempt demotion to light userdata
+                        {
+                                void* lud = lua_touserdata( L, i);
+                                lua_pushlightuserdata( L2, lud);
+                        }
+                        else // raise an error
+                        {
+                                (void) luaL_error( L, "can't copy non-deep full userdata across lanes");
+                        }
                 }
                 break;