10 files changed, 281 insertions, 125 deletions

diff --git a/CHANGES b/CHANGES
index 538acba..134b64f 100644
--- a/CHANGES
+++ b/CHANGES
@@ -1,5 +1,15 @@
 CHANGES:
 
+CHANGE 67: BGe 2-Aug-13
+   * version 3.6.3
+   * lane:cancel(<negative-timeout>) only causes cancel_test() to return true but won't interrupt execution of the lane during linda operations
+
+CHANGE 66: BGe 31-Jul-13
+   * more explicit errors when trying to transfer unknown source functions (with new configure option verbose_errors)
+
+CHANGE 65: BGe 23-Jul-13
+   * default options wrap allocator around a mutex when run by LuaJIT
+
 CHANGE 64: BGe 20-Jul-13
    * WIN32 builds against pre-Vista versions no longer use PulseEvent to fix occasional hangs when a wake event is missed
 
diff --git a/docs/index.html b/docs/index.html
index 617403a..0e32504 100644
--- a/docs/index.html
+++ b/docs/index.html
@@ -70,7 +70,7 @@
                         </p>
 
                         <p>
-                                This document was revised on 20-May-13, and applies to version <tt>3.6.2</tt>.
+                                This document was revised on 02-Aug-13, and applies to version <tt>3.6.3</tt>.
                         </p>
                 </font>
         </center>
@@ -294,6 +294,19 @@
 
                 <tr valign=top>
                         <td>
+                                <code>.verbose_errors</code>
+                        </td>
+                        <td>
+                                <tt>nil</tt>/<tt>false</tt>/<tt>true</tt>
+                        </td>
+                        <td>
+                                (Since v3.6.3) If equal to <tt>true</tt>, Lanes will collect more information when transfering stuff across Lua states to help identify errors (with a cost).
+                                Default is <tt>false</tt>.
+                        </td>
+                </tr>
+
+                <tr valign=top>
+                        <td>
                                 <code>.protect_allocator</code>
                         </td>
                         <td>
@@ -539,7 +552,7 @@
                         </td>
                         <td>integer >= 1/<tt>true</tt></td>
                         <td>
-                                By default, lanes are only cancellable when they <u>enter</u> a pending <tt>:receive()</tt> or <tt>:send()</tt> call. With this option, one can set cancellation check to occur every <tt>N</tt> Lua statements. The value <tt>true</tt> uses a default value (100).
+                                By default, lanes are only cancellable when they <u>enter</u> a pending <tt>:receive()</tt> or <tt>:send()</tt> call. With this option, one can set <a href="#cancelling">cancellation</a> check to occur every <tt>N</tt> Lua statements. The value <tt>true</tt> uses a default value (100).
                                 It is also possible to manually test for cancel requests with <tt>cancel_test()</tt>.
                         </td>
                 </tr>
@@ -705,7 +718,7 @@
                         </td>
                         <td/>
                         <td>
-                                received cancellation and finished itself.
+                                received <a href="#cancelling">cancellation</a> and finished itself.
                         </td>
                 </tr>
                 <tr>
@@ -833,8 +846,10 @@
 </pre></td></tr></table>
 
 <p>
-        <tt>cancel()</tt>sends a cancellation request to the lane. If <tt>timeout_secs</tt> is non-zero, waits for the request to be processed, or a timeout to occur.
-        Returns <tt>true</tt> if the lane was already done (in <tt>"done"</tt>, <tt>"error"</tt> or <tt>"cancelled"</tt> status) or if the cancellation was fruitful within timeout period.
+        <tt>cancel()</tt>sends a cancellation request to the lane.<br/>
+        If <tt>timeout_secs</tt> is positive (aka "hard cancel"), waits for the request to be processed, or a timeout to occur.<br/>
+        If <tt>timeout_secs</tt> is negative (aka "soft cancel"), starting with version 3.6.3, will only cause <tt>cancel_test()</tt> to return true, so that the lane can cleanup manually. You can't provide a second argument in that case.<br/>
+        Returns <tt>true</tt> if soft cancelling, or the lane was already done (in <tt>"done"</tt>, <tt>"error"</tt> or <tt>"cancelled"</tt> status), or the cancellation was fruitful within timeout period.
 </p>
 
 <p>
@@ -887,7 +902,7 @@
                                 -- no special error: true error
                                 print( " error: "..tostring(err))
                         elseif type( err) == "userdata" then
-                                -- lane cancellation is performed by throwing a special userdata as error
+                                -- lane <a href="#cancelling">cancellation</a> is performed by throwing a special userdata as error
                                 print( "after cancel")
                         else
                                 -- no error: we just got finalized
@@ -977,11 +992,15 @@
 </p>
 
 <p>
-        <tt>send</tt> returns <tt>true</tt> if the sending succeeded, and <tt>false</tt> if the queue limit was met, and the queue did not empty enough during the given timeout, or the operation was <a href="#cancelling">cancelled</a>.
+        <a href="#cancelling">Hard cancellation</a> will cause pending linda operations to abort execution of the lane through a cancellation error. This means that you have to install a <a href="#finalizers">finalizer</a> in your lane if you want to run some code in that situation.
+</p>
+
+<p>
+        <tt>send</tt> returns <tt>true</tt> if the sending succeeded, and <tt>false</tt> if the queue limit was met, and the queue did not empty enough during the given timeout.
 </p>
 
 <p>
-        Equally, <tt>receive</tt> returns a key and the value extracted from it, or nothing for timeout or <a href="#cancelling">cancellation</a>. Note that <tt>nil</tt>s can be sent and received; the <tt>key</tt> value will tell it apart from a timeout.
+        Equally, <tt>receive</tt> returns a key and the value extracted from it, or nothing for timeout. Note that <tt>nil</tt>s can be sent and received; the <tt>key</tt> value will tell it apart from a timeout.
         <br>
         Version 3.4.0 introduces an API change in the returned values: <tt>receive</tt> returns the key followed by the value(s), in that order, and not the other way around.
 </p>
diff --git a/lanes-3.6.2-1.rockspec b/lanes-3.6.3-1.rockspec
index 8679c08..18bae0a 100644
--- a/lanes-3.6.2-1.rockspec
+++ b/lanes-3.6.3-1.rockspec
@@ -7,11 +7,11 @@
 
 package = "Lanes"
 
-version = "3.6.2-1"
+version = "3.6.3-1"
 
 source= {
         url= "git://github.com/LuaLanes/lanes.git",
-        branch= "v3.6.2"
+        branch= "v3.6.3"
 }
 
 description = {
diff --git a/src/lanes.c b/src/lanes.c
index 08bdb9a..e36a073 100644
--- a/src/lanes.c
+++ b/src/lanes.c
@@ -52,7 +52,7 @@
  *      ...
  */
 
-char const* VERSION = "3.6.2";
+char const* VERSION = "3.6.3";
 
 /*
 ===============================================================================
@@ -115,10 +115,21 @@ THE SOFTWARE.
 */
 #define ERROR_FULL_STACK
 
+/*
+ * Lane cancellation request modes
+ */
+enum e_cancel_request
+{
+        CANCEL_NONE, // no pending cancel request
+        CANCEL_SOFT, // user wants the lane to cancel itself manually on cancel_test()
+        CANCEL_HARD  // user wants the lane to be interrupted (meaning code won't return from those functions) from inside linda:send/receive calls
+};
+
 // NOTE: values to be changed by either thread, during execution, without
 //       locking, are marked "volatile"
 //
-struct s_lane {
+struct s_lane
+{
         THREAD_T thread;
         //
         // M: sub-thread OS thread
@@ -140,7 +151,7 @@ struct s_lane {
         //
         // When status is WAITING, points on the linda's signal the thread waits on, else NULL
 
-        volatile bool_t cancel_request;
+        volatile enum e_cancel_request cancel_request;
         //
         // M: sets to FALSE, flags TRUE for cancel request
         // S: reads to see if cancel is requested
@@ -178,7 +189,7 @@ struct s_lane {
         // For tracking only
 };
 
-static bool_t cancel_test( lua_State*L );
+static enum e_cancel_request cancel_test( lua_State* L);
 static void cancel_error( lua_State*L );
 
 #define CANCEL_TEST_KEY ((void*)cancel_test)    // used as registry key
@@ -372,7 +383,7 @@ LUAG_FUNC( linda_send)
 {
         struct s_Linda *linda = lua_toLinda( L, 1);
         bool_t ret;
-        bool_t cancel = FALSE;
+        enum e_cancel_request cancel = CANCEL_NONE;
         int pushed;
         time_d timeout= -1.0;
         uint_t key_i = 2; // index of first key, if timeout not there
@@ -434,7 +445,7 @@ LUAG_FUNC( linda_send)
                         /* limit faced; push until timeout */
 
                         cancel = cancel_test( L);   // testing here causes no delays
-                        if (cancel)
+                        if( cancel != CANCEL_NONE) // if user wants to cancel, the call returns without sending anything
                         {
                                 break;
                         }
@@ -486,7 +497,8 @@ LUAG_FUNC( linda_send)
                 return luaL_error( L, "tried to copy unsupported types");
         }
 
-        if( cancel)
+        // raise an error interrupting execution only in case of hard cancel
+        if( cancel == CANCEL_HARD)
                 cancel_error( L);
 
         lua_pushboolean( L, ret);
@@ -510,7 +522,7 @@ LUAG_FUNC( linda_receive)
 {
         struct s_Linda *linda = lua_toLinda( L, 1);
         int pushed, expected_pushed_min, expected_pushed_max;
-        bool_t cancel = FALSE;
+        enum e_cancel_request cancel = CANCEL_NONE;
         keeper_api_t keeper_receive;
         
         time_d timeout = -1.0;
@@ -592,16 +604,16 @@ LUAG_FUNC( linda_receive)
                         /* nothing received; wait until timeout */
 
                         cancel = cancel_test( L);   // testing here causes no delays
-                        if( cancel)
+                        if( cancel != CANCEL_NONE) // if user wants to cancel, the call returns without providing anything
                         {
                                 break;
                         }
 
                         // change status of lane to "waiting"
                         {
-                                struct s_lane *s;
+                                struct s_lane* s;
                                 enum e_status prev_status = ERROR_ST; // prevent 'might be used uninitialized' warnings
-                                STACK_GROW(L,1);
+                                STACK_GROW( L, 1);
 
                                 STACK_CHECK( L);
                                 lua_pushlightuserdata( L, CANCEL_TEST_KEY);
@@ -643,7 +655,8 @@ LUAG_FUNC( linda_receive)
                 return luaL_error( L, "tried to copy unsupported types");
         }
 
-        if( cancel)
+        // raise an error interrupting execution only in case of hard cancel
+        if( cancel == CANCEL_HARD)
                 cancel_error( L);
 
         return pushed;
@@ -1176,31 +1189,41 @@ static cancel_result thread_cancel( struct s_lane *s, double secs, bool_t force)
         }
         else if( s->status < DONE)
         {
-                s->cancel_request = TRUE;    // it's now signaled to stop
                 // signal the linda the wake up the thread so that it can react to the cancel query
                 // let us hope we never land here with a pointer on a linda that has been destroyed...
+                if( secs < 0.0)
+                {
+                        s->cancel_request = CANCEL_SOFT;    // it's now signaled to stop
+                        // negative timeout: we don't want to truly abort the lane, we just want it to react to cancel_test() on its own
+                        // say we succeeded though
+                        result = CR_Cancelled;
+                }
+                else
                 {
-                        SIGNAL_T *waiting_on = s->waiting_on;
-                        if( s->status == WAITING && waiting_on != NULL)
+                        s->cancel_request = CANCEL_HARD;    // it's now signaled to stop
                         {
-                                SIGNAL_ALL( waiting_on);
+                                SIGNAL_T *waiting_on = s->waiting_on;
+                                if( s->status == WAITING && waiting_on != NULL)
+                                {
+                                        SIGNAL_ALL( waiting_on);
+                                }
                         }
-                }
 
-                result = THREAD_WAIT( &s->thread, secs, &s->done_signal, &s->done_lock, &s->status) ? CR_Cancelled : CR_Timeout;
+                        result = THREAD_WAIT( &s->thread, secs, &s->done_signal, &s->done_lock, &s->status) ? CR_Cancelled : CR_Timeout;
 
-                if( (result == CR_Timeout) && force)
-                {
-                        // Killing is asynchronous; we _will_ wait for it to be done at
-                        // GC, to make sure the data structure can be released (alternative
-                        // would be use of "cancellation cleanup handlers" that at least
-                        // PThread seems to have).
-                        //
-                        THREAD_KILL( &s->thread);
-                        s->mstatus = KILLED;     // mark 'gc' to wait for it
-                        // note that s->status value must remain to whatever it was at the time of the kill
-                        // because we need to know if we can lua_close() the Lua State or not.
-                        result = CR_Killed;
+                        if( (result == CR_Timeout) && force)
+                        {
+                                // Killing is asynchronous; we _will_ wait for it to be done at
+                                // GC, to make sure the data structure can be released (alternative
+                                // would be use of "cancellation cleanup handlers" that at least
+                                // PThread seems to have).
+                                //
+                                THREAD_KILL( &s->thread);
+                                s->mstatus = KILLED;     // mark 'gc' to wait for it
+                                // note that s->status value must remain to whatever it was at the time of the kill
+                                // because we need to know if we can lua_close() the Lua State or not.
+                                result = CR_Killed;
+                        }
                 }
         }
         else
@@ -1307,7 +1330,7 @@ static int selfdestruct_gc( lua_State* L)
                         struct s_lane* s = selfdestruct_first;
                         while( s != SELFDESTRUCT_END )
                         {
-                                // attempt a regular unforced cancel with a small timeout
+                                // attempt a regular unforced hard cancel with a small timeout
                                 bool_t cancelled = THREAD_ISNULL( s->thread) || thread_cancel( s, 0.0001, FALSE);
                                 // if we failed, and we know the thread is waiting on a linda
                                 if( cancelled == FALSE && s->status == WAITING && s->waiting_on != NULL)
@@ -1353,7 +1376,7 @@ static int selfdestruct_gc( lua_State* L)
                                                 struct s_lane* s = selfdestruct_first;
                                                 while( s != SELFDESTRUCT_END)
                                                 {
-                                                        if( s->cancel_request)
+                                                        if( s->cancel_request == CANCEL_HARD)
                                                                 ++ n;
                                                         s = s->selfdestruct_next;
                                                 }
@@ -1444,21 +1467,22 @@ static int selfdestruct_gc( lua_State* L)
 * Returns TRUE if any locks are to be exited, and 'cancel_error()' called,
 * to make execution of the lane end.
 */
-static bool_t cancel_test( lua_State*L ) {
-    struct s_lane *s;
+static enum e_cancel_request cancel_test( lua_State* L)
+{
+        struct s_lane* s;
 
-    STACK_GROW(L,1);
+        STACK_GROW( L, 1);
 
-  STACK_CHECK( L);
-    lua_pushlightuserdata( L, CANCEL_TEST_KEY );
-    lua_rawget( L, LUA_REGISTRYINDEX );
-    s= lua_touserdata( L, -1 );     // lightuserdata (true 's_lane' pointer) / nil
-    lua_pop(L,1);
-  STACK_END( L, 0);
+        STACK_CHECK( L);
+        lua_pushlightuserdata( L, CANCEL_TEST_KEY);
+        lua_rawget( L, LUA_REGISTRYINDEX);
+        s = lua_touserdata( L, -1);     // lightuserdata (true 's_lane' pointer) / nil
+        lua_pop( L, 1);
+        STACK_END( L, 0);
 
-    // 's' is NULL for the original main state (no-one can cancel that)
-    //
-    return s && s->cancel_request;
+        // 's' is NULL for the original main state (no-one can cancel that)
+        //
+        return s ? s->cancel_request : CANCEL_NONE;
 }
 
 static void cancel_error( lua_State*L ) {
@@ -1467,22 +1491,24 @@ static void cancel_error( lua_State*L ) {
     lua_error(L);   // no return
 }
 
-static void cancel_hook( lua_State*L, lua_Debug *ar ) {
-    (void)ar;
-    if (cancel_test(L)) cancel_error(L);
+static void cancel_hook( lua_State*L, lua_Debug *ar )
+{
+        (void)ar;
+        if( cancel_test( L) != CANCEL_NONE)
+                cancel_error( L);
 }
 
 
 //---
-// bool= cancel_test()
+// bool = cancel_test()
 //
 // Available inside the global namespace of lanes
 // returns a boolean saying if a cancel request is pending
 //
 LUAG_FUNC( cancel_test)
 {
-        bool_t test = cancel_test( L);
-        lua_pushboolean( L, test);
+        enum e_cancel_request test = cancel_test( L);
+        lua_pushboolean( L, test != CANCEL_NONE);
         return 1;
 }
 
@@ -1724,7 +1750,7 @@ static THREAD_RETURN_T THREAD_CALLCONV lane_main( void *vs)
     // Tie "cancel_test()" to the state
     //
     lua_pushcfunction( L, LG_cancel_test);
-    lua_setglobal( L, "cancel_test" );
+    lua_setglobal( L, "cancel_test");
 
 #ifdef ERROR_FULL_STACK
     // Tie "set_error_reporting()" to the state
@@ -2065,7 +2091,7 @@ LUAG_FUNC( thread_new)
         s->status= PENDING;
         s->waiting_on = NULL;
         s->debug_name = NULL;
-        s->cancel_request= FALSE;
+        s->cancel_request = CANCEL_NONE;
 
 #if THREADWAIT_METHOD == THREADWAIT_CONDVAR
         MUTEX_INIT( &s->done_lock);
@@ -2183,6 +2209,10 @@ LUAG_FUNC( thread_cancel)
                 if( lua_isnumber( L, 2))
                 {
                         secs = lua_tonumber( L, 2);
+                        if( secs < 0.0 && lua_gettop( L) > 2)
+                        {
+                                return luaL_error( L, "can't force a soft cancel");
+                        }
                         ++ force_i;
                 }
                 else if( lua_isnil( L, 2))
@@ -2611,8 +2641,9 @@ void register_core_libfuncs_for_keeper( lua_State* L)
 /*
 ** One-time initializations
 */
-static void init_once_LOCKED( lua_State* L, int const _on_state_create, int const nbKeepers, lua_Number _shutdown_timeout, bool_t _track_lanes)
+static void init_once_LOCKED( lua_State* L, int const _on_state_create, int const nbKeepers, lua_Number _shutdown_timeout, bool_t _track_lanes, bool_t verbose_errors)
 {
+        GVerboseErrors = verbose_errors;
 #if (defined PLATFORM_WIN32) || (defined PLATFORM_POCKETPC)
         now_secs();     // initialize 'now_secs()' internal offset
 #endif
@@ -2724,10 +2755,12 @@ LUAG_FUNC( configure)
         char const* name = luaL_checkstring( L, lua_upvalueindex( 1));
         // all parameter checks are done lua-side
         int const nbKeepers = (int)lua_tointeger( L, 1);
+        // all these can be nil when lanes.core is required internally! (but are only processed at first init anyway)
         int const on_state_create = lua_isfunction( L, 2) ? 2 : 0;
         lua_Number shutdown_timeout = lua_tonumber( L, 3);
         bool_t track_lanes = lua_toboolean( L, 4);
         bool_t protect_allocator = lua_toboolean( L, 5);
+        bool_t verbose_errors = lua_toboolean( L, 6);
 
         DEBUGSPEW_CODE( fprintf( stderr, INDENT_BEGIN "%p: lanes.configure() BEGIN\n" INDENT_END, L));
         DEBUGSPEW_CODE( ++ debugspew_indent_depth);
@@ -2738,11 +2771,14 @@ LUAG_FUNC( configure)
         {
                 void* ud;
                 lua_Alloc allocf = lua_getallocf( L, &ud);
-                struct ProtectedAllocator_s* s = (struct ProtectedAllocator_s*) allocf( ud, NULL, 0, sizeof( struct ProtectedAllocator_s));
-                s->allocf = allocf;
-                s->ud = ud;
-                MUTEX_INIT( &s->lock);
-                lua_setallocf( L, protected_lua_Alloc, s);
+                if( allocf != protected_lua_Alloc) // just in case
+                {
+                        struct ProtectedAllocator_s* s = (struct ProtectedAllocator_s*) allocf( ud, NULL, 0, sizeof( struct ProtectedAllocator_s));
+                        s->allocf = allocf;
+                        s->ud = ud;
+                        MUTEX_INIT( &s->lock);
+                        lua_setallocf( L, protected_lua_Alloc, s);
+                }
         }
 
         // Create main module interface table
@@ -2818,7 +2854,7 @@ LUAG_FUNC( configure)
                 static volatile int /*bool*/ go_ahead; // = 0
                 if( InterlockedCompareExchange( &s_initCount, 1, 0) == 0)
                 {
-                        init_once_LOCKED( L, on_state_create, nbKeepers, shutdown_timeout, track_lanes);
+                        init_once_LOCKED( L, on_state_create, nbKeepers, shutdown_timeout, track_lanes, verbose_errors);
                         go_ahead = 1;    // let others pass
                 }
                 else
@@ -2836,7 +2872,7 @@ LUAG_FUNC( configure)
                         //
                         if( s_initCount == 0)
                         {
-                                init_once_LOCKED( L, on_state_create, nbKeepers, shutdown_timeout, track_lanes);
+                                init_once_LOCKED( L, on_state_create, nbKeepers, shutdown_timeout, track_lanes, verbose_errors);
                                 s_initCount = 1;
                         }
                 }
diff --git a/src/lanes.lua b/src/lanes.lua
index ac3da26..175002a 100644
--- a/src/lanes.lua
+++ b/src/lanes.lua
@@ -69,6 +69,7 @@ lanes.configure = function( _params)
                 shutdown_timeout = 0.25,
                 with_timers = true,
                 track_lanes = 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
         }
@@ -105,6 +106,14 @@ lanes.configure = function( _params)
                 track_lanes = function( _val)
                         -- track_lanes may be nil or boolean
                         return _val and type( _val) == "boolean" or true
+                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
         }
 
@@ -138,7 +147,7 @@ lanes.configure = function( _params)
         assert( type( core)=="table")
 
         -- configure() is available only the first time lanes.core is required process-wide, and we *must* call it to have the other functions in the interface
-        if core.configure then core.configure( _params.nb_keepers, _params.on_state_create, _params.shutdown_timeout, _params.track_lanes, _params.protect_allocator) end
+        if core.configure then core.configure( _params.nb_keepers, _params.on_state_create, _params.shutdown_timeout, _params.track_lanes, _params.protect_allocator, _params.verbose_errors) end
 
         local thread_new = assert( core.thread_new)
 
diff --git a/src/tools.c b/src/tools.c
index d2dfdf5..a3cc6b7 100644
--- a/src/tools.c
+++ b/src/tools.c
@@ -42,6 +42,10 @@ THE SOFTWARE.
 #include <string.h>
 #include <ctype.h>
 #include <stdlib.h>
+#include <malloc.h>
+
+// for verbose errors
+bool_t GVerboseErrors = FALSE;
 
 /*
 ** Copied from Lua 5.2 loadlib.c
@@ -1285,9 +1289,9 @@ static bool_t push_cached_table( lua_State *L2, uint_t L2_cache_i, lua_State *L,
  *
  * Always pushes a function to 'L2'.
  */
-static void inter_copy_func( lua_State* L2, uint_t L2_cache_i, lua_State* L, uint_t i);
+static void inter_copy_func( lua_State* L2, uint_t L2_cache_i, lua_State* L, uint_t i, char const* upName_);
 
-static void push_cached_func( lua_State* L2, uint_t L2_cache_i, lua_State* L, uint_t i)
+static void push_cached_func( lua_State* L2, uint_t L2_cache_i, lua_State* L, uint_t i, char const* upName_)
 {
         void* const aspointer = (void*)lua_topointer( L, i);
         // TBD: Merge this and same code for tables
@@ -1319,7 +1323,7 @@ static void push_cached_func( lua_State* L2, uint_t L2_cache_i, lua_State* L, ui
                 // via upvalues
                 //
                 // pushes a copy of the func, stores a reference in the cache
-                inter_copy_func( L2, L2_cache_i, L, i);                     // ... {cache} ... function
+                inter_copy_func( L2, L2_cache_i, L, i, upName_);            // ... {cache} ... function
         }
         else // found function in the cache
         {
@@ -1363,16 +1367,19 @@ 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 key = lua_tostring( L, -2); // only for debugging (BEWARE, IT MAY CHANGE THE VALUE IF IT IS CONVERTIBLE, AND WRECK THE LOOP ITERATION PROCESS!)
+                //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
                 // append key name to fqn stack
                 ++ depth_;
                 lua_pushvalue( L, -2);                                // o "r" {c} {fqn} ... {?} k v k
                 lua_rawseti( L, fqn, depth_);                         // o "r" {c} {fqn} ... {?} k v
                 if( lua_rawequal( L, -1, what)) // is it what we are looking for?
                 {
+                        STACK_MID( L, 2);
                         // update shortest name
                         if( depth_ < shortest_)
                         {
@@ -1382,32 +1389,74 @@ static int discover_object_name_recur( lua_State* L, int shortest_, int depth_)
                         }
                         // no need to search further at this level
                         lua_pop( L, 2);                                     // o "r" {c} {fqn} ... {?}
+                        STACK_MID( L, 0);
                         break;
                 }
-                else if( lua_istable( L, -1))
+                else if( lua_istable( L, -1))                         // o "r" {c} {fqn} ... {?} k {}
                 {
+                        STACK_MID( L, 2);
                         shortest_ = discover_object_name_recur( L, shortest_, depth_);
                         // search in the table's metatable too
-                        if( lua_getmetatable( L, -1))
+                        if( lua_getmetatable( L, -1))                       // o "r" {c} {fqn} ... {?} k {} {mt}
                         {
                                 if( lua_istable( L, -1))
                                 {
+                                        ++ depth_;
+                                        lua_pushliteral( L, "__metatable");             // o "r" {c} {fqn} ... {?} k {} {mt} "__metatable"
+                                        lua_rawseti( L, fqn, depth_);                   // o "r" {c} {fqn} ... {?} k {} {mt}
                                         shortest_ = discover_object_name_recur( L, shortest_, depth_);
+                                        lua_pushnil( L);                                // o "r" {c} {fqn} ... {?} k {} {mt} nil
+                                        lua_rawseti( L, fqn, depth_);                   // o "r" {c} {fqn} ... {?} k {} {mt}
+                                        -- depth_;
                                 }
-                                lua_pop( L, 1);
+                                lua_pop( L, 1);                                   // o "r" {c} {fqn} ... {?} k {}
+                                STACK_MID( L, 2);
                         }
                 }
-                else if( lua_isuserdata( L, -1))
+                else if( lua_isthread( L, -1))                        // 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))
+                        {
+                                shortest_ = discover_object_name_recur( L, shortest_, 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
+                {
+                        STACK_MID( L, 2);
                         // search in the object's metatable (some modules are built that way)
-                        if( lua_getmetatable( L, -1))
+                        if( lua_getmetatable( L, -1))                       // o "r" {c} {fqn} ... {?} k U {mt}
                         {
                                 if( lua_istable( L, -1))
                                 {
+                                        ++ depth_;
+                                        lua_pushliteral( L, "__metatable");             // o "r" {c} {fqn} ... {?} k U {mt} "__metatable"
+                                        lua_rawseti( L, fqn, depth_);                   // o "r" {c} {fqn} ... {?} k U {mt}
                                         shortest_ = discover_object_name_recur( L, shortest_, depth_);
+                                        lua_pushnil( L);                                // o "r" {c} {fqn} ... {?} k U {mt} nil
+                                        lua_rawseti( L, fqn, depth_);                   // o "r" {c} {fqn} ... {?} k U {mt}
+                                        -- depth_;
                                 }
-                                lua_pop( L, 1);
+                                lua_pop( L, 1);                                   // o "r" {c} {fqn} ... {?} k U
+                                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))
+                        {
+                                ++ depth_;
+                                lua_pushliteral( L, "uservalue");                 // o "r" {c} {fqn} ... {?} k v {u} "uservalue"
+                                lua_rawseti( L, fqn, depth_);                     // o "r" {c} {fqn} ... {?} k v {u}
+                                shortest_ = discover_object_name_recur( L, shortest_, depth_);
+                                lua_pushnil( L);                                  // o "r" {c} {fqn} ... {?} k v {u} nil
+                                lua_rawseti( L, fqn, depth_);                     // o "r" {c} {fqn} ... {?} k v {u}
+                                -- depth_;
                         }
+                        lua_pop( L, 1);                                     // o "r" {c} {fqn} ... {?} k U
+                        STACK_MID( L, 2);
                 }
                 // make ready for next iteration
                 lua_pop( L, 1);                                       // o "r" {c} {fqn} ... {?} k
@@ -1416,6 +1465,7 @@ static int discover_object_name_recur( lua_State* L, int shortest_, int depth_)
                 lua_rawseti( L, fqn, depth_);                         // o "r" {c} {fqn} ... {?} k
                 -- depth_;
         }                                                       // o "r" {c} {fqn} ... {?}
+        STACK_END( 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
@@ -1442,6 +1492,7 @@ int luaG_nameof( lua_State* L)
                 lua_insert( L, -2);                                   // "type" o
                 return 2;
         }
+
         STACK_GROW( L, 4);
         // this slot will contain the shortest name we found when we are done
         lua_pushnil( L);                                        // o nil
@@ -1461,7 +1512,7 @@ int luaG_nameof( lua_State* L)
 /*
 * Push a looked-up native/LuaJIT function.
 */
-static void lookup_native_func( lua_State* L2, lua_State* L, uint_t i)
+static void lookup_native_func( lua_State* L2, lua_State* L, uint_t i, char const* upName_)
 {
         char const* fqn;                                         // L                        // L2
         size_t len;
@@ -1478,14 +1529,28 @@ static void lookup_native_func( lua_State* L2, lua_State* L, uint_t i)
         lua_pop( L, 2);                                          // ... f ...
         if( !fqn)
         {
-                char const* from;
+                char const *from, *typewhat, *what, *gotchaA, *gotchaB;
                 // try to discover the name of the function we want to send
-                lua_pushcfunction( L, luaG_nameof);                    // ... f ...luaG_nameof
-                lua_pushvalue( L, i);                                  // ... f ... luaG_nameof f
-                lua_call( L, 1, 2);                                    // ... f ... "type" "name"
-                lua_getglobal( L, "decoda_name");                      // ... f ... "type" "name" decoda_name
+                lua_getglobal( L, "decoda_name");                      // ... f ... decoda_name
                 from = lua_tostring( L, -1);
-                (void) luaL_error( L, "%s '%s' not found in %s origin transfer database.", lua_tostring( L, -3), lua_tostring( L, -2), from ? from : "main");
+                lua_pushcfunction( L, luaG_nameof);                    // ... f ... decoda_name luaG_nameof
+                lua_pushvalue( L, i);                                  // ... f ... decoda_name luaG_nameof f
+                lua_call( L, 1, 2);                                    // ... f ... decoda_name "type" "name"|nil
+                typewhat = (lua_type( L, -2) == LUA_TSTRING) ? lua_tostring( L, -2) : luaL_typename( L, -2);
+                // second return value can be nil if the function was not found
+                // probable reason: the function was removed from the source Lua state before Lanes was required.
+                if( lua_isnil( L, -1))
+                {
+                        gotchaA = " referenced by";
+                        gotchaB = "\n(did you remove it from the source Lua state before requiring Lanes?)";
+                        what = upName_;
+                }
+                else
+                {
+                        gotchaB = "";
+                        what = (lua_type( L, -1) == LUA_TSTRING) ? lua_tostring( L, -1) : luaL_typename( L, -1);
+                }
+                (void) luaL_error( L, "%s%s '%s' not found in %s origin transfer database.%s", typewhat, gotchaA, what, from ? from : "main", gotchaB);
                 return;
         }
         STACK_END( L, 0);
@@ -1516,9 +1581,9 @@ static void lookup_native_func( lua_State* L2, lua_State* L, uint_t i)
 enum e_vt {
     VT_NORMAL, VT_KEY, VT_METATABLE
 };
-static bool_t inter_copy_one_( lua_State *L2, uint_t L2_cache_i, lua_State *L, uint_t i, enum e_vt value_type );
+static bool_t inter_copy_one_( lua_State* L2, uint_t L2_cache_i, lua_State* L, uint_t i, enum e_vt value_type, char const* upName_);
 
-static void inter_copy_func( lua_State* L2, uint_t L2_cache_i, lua_State* L, uint_t i)
+static void inter_copy_func( lua_State* L2, uint_t L2_cache_i, lua_State* L, uint_t i, char const* upName_)
 {
         FuncSubType funcSubType;
         /*lua_CFunction cfunc =*/ luaG_tocfunction( L, i, &funcSubType); // NULL for LuaJIT-fast && bytecode functions
@@ -1612,14 +1677,14 @@ static void inter_copy_func( lua_State* L2, uint_t L2_cache_i, lua_State* L, uin
                         * instead, the function shall have LUA_RIDX_GLOBALS taken in the destination state!
                         */
                         {
-                                DEBUGSPEW_CODE( char const* upname);
+                                char const* upname;
 #if LUA_VERSION_NUM == 502
                                 // With Lua 5.2, each Lua function gets its environment as one of its upvalues (named LUA_ENV, aka "_ENV" by default)
                                 // Generally this is LUA_RIDX_GLOBALS, which we don't want to copy from the source to the destination state...
                                 // -> if we encounter an upvalue equal to the global table in the source, bind it to the destination's global table
                                 lua_pushglobaltable( L);                           // ... _G
 #endif // LUA_VERSION_NUM
-                                for( n = 0; (DEBUGSPEW_CODE( upname =) lua_getupvalue( L, i, 1 + n)) != NULL; ++ n)
+                                for( n = 0; (upname = lua_getupvalue( L, i, 1 + n)) != NULL; ++ n)
                                 {                                                  // ... _G up[n]
                                         DEBUGSPEW_CODE( fprintf( stderr, INDENT_BEGIN "UPNAME[%d]: %s\n" INDENT_END, n, upname));
 #if LUA_VERSION_NUM == 502
@@ -1630,8 +1695,10 @@ static void inter_copy_func( lua_State* L2, uint_t L2_cache_i, lua_State* L, uin
                                         else
 #endif // LUA_VERSION_NUM
                                         {
-                                                if( !inter_copy_one_( L2, L2_cache_i, L, lua_gettop( L), VT_NORMAL))    // ... {cache} ... function <upvalues>
+                                                if( !inter_copy_one_( L2, L2_cache_i, L, lua_gettop( L), VT_NORMAL, upname))    // ... {cache} ... function <upvalues>
+                                                {
                                                         luaL_error( L, "Cannot copy upvalue type '%s'", luaL_typename( L, -1));
+                                                }
                                         }
                                         lua_pop( L, 1);                                  // ... _G
                                 }
@@ -1664,7 +1731,7 @@ static void inter_copy_func( lua_State* L2, uint_t L2_cache_i, lua_State* L, uin
         {
                 lua_pop( L2, 1);                                                                // ... {cache} ...
                 // No need to transfer upvalues for C/JIT functions since they weren't actually copied, only looked up
-                lookup_native_func( L2, L, i);                                                  // ... {cache} ... function
+                lookup_native_func( L2, L, i, upName_);                                         // ... {cache} ... function
         }
         STACK_END( L, 0);
 }
@@ -1679,7 +1746,7 @@ static void inter_copy_func( lua_State* L2, uint_t L2_cache_i, lua_State* L, uin
 *
 * Returns TRUE if value was pushed, FALSE if its type is non-supported.
 */
-static bool_t inter_copy_one_( lua_State* L2, uint_t L2_cache_i, lua_State* L, uint_t i, enum e_vt vt)
+static bool_t inter_copy_one_( lua_State* L2, uint_t L2_cache_i, lua_State* L, uint_t i, enum e_vt vt, char const* upName_)
 {
         bool_t ret = TRUE;
 
@@ -1762,25 +1829,9 @@ static bool_t inter_copy_one_( lua_State* L2, uint_t L2_cache_i, lua_State* L, u
                         break;
                 }
                 {
-                        /* 
-                        * Passing C functions is risky; if they refer to LUA_ENVIRONINDEX
-                        * and/or LUA_REGISTRYINDEX they might work unintended (not work)
-                        * at the target.
-                        *
-                        * On the other hand, NOT copying them causes many self tests not
-                        * to work (timer, hangtest, ...)
-                        *
-                        * The trouble is, we cannot KNOW if the function at hand is safe
-                        * or not. We cannot study it's behaviour. We could trust the user,
-                        * but they might not even know they're sending lua_CFunction over
-                        * (as upvalues etc.).
-                        */
-#if 0
-                        if( lua_iscfunction( L, i))
-                                luaL_error( L, "Copying lua_CFunction between Lua states is risky, and currently disabled." ); 
-#endif
+                        DEBUGSPEW_CODE( fprintf( stderr, INDENT_BEGIN "FUNCTION\n" INDENT_END));
                         STACK_CHECK( L2);
-                        push_cached_func( L2, L2_cache_i, L, i);
+                        push_cached_func( L2, L2_cache_i, L, i, upName_);
                         STACK_END( L2, 1);
                 }
                 break;
@@ -1822,13 +1873,28 @@ static bool_t inter_copy_one_( lua_State* L2, uint_t L2_cache_i, lua_State* L, u
 
                                 /* Only basic key types are copied over; others ignored
                                 */
-                                if( inter_copy_one_( L2, 0 /*key*/, L, key_i, VT_KEY))
+                                if( inter_copy_one_( L2, 0 /*key*/, L, key_i, VT_KEY, upName_))
                                 {
+                                        char* valPath = (char*) upName_;
+                                        if( GVerboseErrors)
+                                        {
+                                                // for debug purposes, let's try to build a useful name
+                                                if( lua_type( L, key_i) == LUA_TSTRING)
+                                                {
+                                                        valPath = (char*) alloca( strlen( upName_) + strlen( lua_tostring( L, key_i)) + 2);
+                                                        sprintf( valPath, "%s.%s", upName_, lua_tostring( L, key_i));
+                                                }
+                                                else if( lua_type( L, key_i) == LUA_TNUMBER)
+                                                {
+                                                        valPath = (char*) alloca( strlen( upName_) + 32 + 3);
+                                                        sprintf( valPath, "%s[" LUA_NUMBER_FMT "]", upName_, lua_tonumber( L, key_i));
+                                                }
+                                        }
                                         /*
                                         * Contents of metatables are copied with cache checking;
                                         * important to detect loops.
                                         */
-                                        if( inter_copy_one_( L2, L2_cache_i, L, val_i, VT_NORMAL))
+                                        if( inter_copy_one_( L2, L2_cache_i, L, val_i, VT_NORMAL, valPath))
                                         {
                                                 ASSERT_L( lua_istable(L2,-3));
                                                 lua_rawset( L2, -3);    // add to table (pops key & val)
@@ -1870,7 +1936,7 @@ static bool_t inter_copy_one_( lua_State* L2, uint_t L2_cache_i, lua_State* L, u
                                         lua_pop( L2, 1);
                                         STACK_MID( L2, 2);
                                         ASSERT_L( lua_istable(L,-1));
-                                        if( inter_copy_one_( L2, L2_cache_i /*for function cacheing*/, L, lua_gettop(L) /*[-1]*/, VT_METATABLE))
+                                        if( inter_copy_one_( L2, L2_cache_i /*for function cacheing*/, L, lua_gettop(L) /*[-1]*/, VT_METATABLE, upName_))
                                         {
                                                 //
                                                 // L2 ([-3]: copied table)
@@ -1942,7 +2008,9 @@ int luaG_inter_copy( lua_State* L, lua_State* L2, uint_t n)
 {
         uint_t top_L = lua_gettop( L);
         uint_t top_L2 = lua_gettop( L2);
-        uint_t i;
+        uint_t i, j;
+        char tmpBuf[16];
+        char* pBuf = GVerboseErrors ? tmpBuf : "?";
         bool_t copyok = TRUE;
 
         if( n > top_L)
@@ -1960,9 +2028,13 @@ int luaG_inter_copy( lua_State* L, lua_State* L2, uint_t n)
         */
         lua_newtable( L2);
 
-        for( i = top_L - n + 1; i <= top_L; ++ i)
+        for( i = top_L - n + 1, j = 1; i <= top_L; ++ i, ++ j)
         {
-                copyok = inter_copy_one_( L2, top_L2 + 1, L, i, VT_NORMAL);
+                if( GVerboseErrors)
+                {
+                        sprintf( tmpBuf, "arg_%d", j);
+                }
+                copyok = inter_copy_one_( L2, top_L2 + 1, L, i, VT_NORMAL, pBuf);
                 if( !copyok)
                 {
                         break;
diff --git a/src/tools.h b/src/tools.h
index 2fe7259..93ed92c 100644
--- a/src/tools.h
+++ b/src/tools.h
@@ -107,5 +107,8 @@ void populate_func_lookup_table( lua_State* L, int _i, char const* _name);
 void serialize_require( lua_State *L);
 extern MUTEX_T require_cs;
 
+// for verbose errors
+extern bool_t GVerboseErrors;
+
 #endif
     // TOOLS_H
diff --git a/tests/fifo.lua b/tests/fifo.lua
index b68d8a4..47db4c9 100644
--- a/tests/fifo.lua
+++ b/tests/fifo.lua
@@ -4,10 +4,9 @@
 -- Sample program for Lua Lanes
 --
 
-local lanes = require "lanes"
-lanes.configure()
+local lanes = require "lanes".configure{shutdown_timeout=3,with_timers=true}
 
-local linda= lanes.linda()
+local linda= lanes.linda( "atom")
 local atomic_inc= lanes.genatomic( linda, "FIFO_n" )
 
 assert( atomic_inc()==1 )
@@ -46,3 +45,5 @@ print( B:receive( 2.0 ) )
 -- Note: A and B can be passed between threads, or used as upvalues
 --       by multiple threads (other parts will be copied but the 'linda'
 --       handle is shared userdata and will thus point to the single place)
+lanes.timer_lane:cancel()
+lanes.timer_lane:join()
\ No newline at end of file
diff --git a/tests/linda_perf.lua b/tests/linda_perf.lua
index be582ce..ebe9eac 100644
--- a/tests/linda_perf.lua
+++ b/tests/linda_perf.lua
@@ -84,8 +84,10 @@ local tests =
         { 4000000, 0, 21},
         { 4000000, 0, 44},]]
 }
+print "tests #1"
 for k, v in pairs( tests) do
         local pre, loop, batch = v[1], v[2], v[3]
+        print( "testing", pre, loop, batch)
         print( pre, loop, batch, "duration = " .. ziva( pre, loop, batch))
 end
 
@@ -188,8 +190,11 @@ local tests2 =
         { 4000000, 0, 21},
         { 4000000, 0, 44},
 }
+
+print "tests #2"
 for k, v in pairs( tests2) do
         local pre, loop, batch = v[1], v[2], v[3]
+        print( "testing", pre, loop, batch)
         print( pre, loop, batch, "duration = " .. ziva2( pre, loop, batch))
 end
 
diff --git a/tests/require.lua b/tests/require.lua
index 1d081b4..656a7dd 100644
--- a/tests/require.lua
+++ b/tests/require.lua
@@ -4,9 +4,10 @@
 -- Test that 'require' works from sublanes
 --
 lanes = require "lanes"
-lanes.configure()
+lanes.configure{with_timers = false}
 
 local function a_lane()
+                print "IN A LANE"
     -- To require 'math' we still actually need to have it initialized for
     -- the lane.
     --
@@ -15,7 +16,7 @@ local function a_lane()
     assert( math.sqrt(4)==2 )
 
     assert( lanes==nil )
-    local lanes = require "lanes".configure()
+    local lanes = require "lanes".configure{with_timers = false}
     assert( lanes and lanes.gen )
 
     local h= lanes.gen( function() return 42 end ) ()
@@ -24,7 +25,7 @@ local function a_lane()
     return v==42
 end
 
-local gen= lanes.gen( "math,package,string,table", a_lane )
+local gen= lanes.gen( "math,package,string,table", {package={}},a_lane )
 
 local h= gen()
 local ret= h[1]