--- OpenCL/OpenCL.xs	2012/04/29 18:39:31	1.58
+++ OpenCL/OpenCL.xs	2012/04/30 09:38:53	1.60
@@ -1560,8 +1560,8 @@
 void
 acquire_gl_objects (OpenCL::Queue self, SV *objects, ...)
 	ALIAS:
+        release_gl_objects = 1
 	enqueue_acquire_gl_objects = 0
-        ALIAS:
         enqueue_release_gl_objects = 1
 	PPCODE:
         if (!SvROK (objects) || SvTYPE (SvRV (objects)) != SVt_PVAV)
@@ -2195,6 +2195,7 @@
               cl_event   ce;
             } arg;
             size_t size;
+            int nullarg = 0;
 
             switch (type)
               {
@@ -2210,17 +2211,20 @@
                 case 'h': arg.ch = SvUV (sv); size = sizeof (arg.ch); break;
                 case 'f': arg.cf = SvNV (sv); size = sizeof (arg.cf); break;
                 case 'd': arg.cd = SvNV (sv); size = sizeof (arg.cd); break;
-                case 'z': arg.cz = SvUV (sv); size = sizeof (arg.cz); break;
 
-                case 'm': arg.cm = SvCLOBJ ("OpenCL::Kernel::setf", "m", sv, "OpenCL::Memory" ); size = sizeof (arg.cm); break;
-                case 'a': arg.ca = SvCLOBJ ("OpenCL::Kernel::setf", "a", sv, "OpenCL::Sampler"); size = sizeof (arg.ca); break;
-                case 'e': arg.ca = SvCLOBJ ("OpenCL::Kernel::setf", "e", sv, "OpenCL::Event"  ); size = sizeof (arg.ce); break;
+                case 'z': nullarg = 1; size = SvIV (sv); break;
+
+                case 'm': nullarg = !SvOK (sv); arg.cm = SvCLOBJ ("OpenCL::Kernel::setf", "m", sv, "OpenCL::Memory" ); size = sizeof (arg.cm); break;
+                case 'a': nullarg = !SvOK (sv); arg.ca = SvCLOBJ ("OpenCL::Kernel::setf", "a", sv, "OpenCL::Sampler"); size = sizeof (arg.ca); break;
+                case 'e': nullarg = !SvOK (sv); arg.ca = SvCLOBJ ("OpenCL::Kernel::setf", "e", sv, "OpenCL::Event"  ); size = sizeof (arg.ce); break;
 
                 default:
                   croak ("OpenCL::Kernel::setf format character '%c' not supported", type);
               }
 
-            clSetKernelArg (self, i - 2, size, &arg);
+            res = clSetKernelArg (self, i - 2, size, nullarg ? 0 : &arg);
+            if (res)
+              croak ("OpenCL::Kernel::setf kernel parameter '%c' (#%d): %s", type, i - 2, err2str (res));
           }
 
         if (i != items)
@@ -2284,12 +2288,12 @@
 void
 set_memory (OpenCL::Kernel self, cl_uint idx, OpenCL::Memory_ornull value)
 	CODE:
-        clSetKernelArg (self, idx, sizeof (value), &value);
+        clSetKernelArg (self, idx, sizeof (value), value ? &value : 0);
 
 void
 set_buffer (OpenCL::Kernel self, cl_uint idx, OpenCL::Buffer_ornull value)
 	CODE:
-        clSetKernelArg (self, idx, sizeof (value), &value);
+        clSetKernelArg (self, idx, sizeof (value), value ? &value : 0);
 
 void
 set_image (OpenCL::Kernel self, cl_uint idx, OpenCL::Image_ornull value)
@@ -2297,7 +2301,7 @@
         set_image2d = 0
         set_image3d = 0
 	CODE:
-        clSetKernelArg (self, idx, sizeof (value), &value);
+        clSetKernelArg (self, idx, sizeof (value), value ? &value : 0);
 
 void
 set_sampler (OpenCL::Kernel self, cl_uint idx, OpenCL::Sampler value)