diff --git a/TODO b/TODO
index 4d6a44bf..32131197 100644
--- a/TODO
+++ b/TODO
@@ -1,55 +1,3 @@
-- strange
-
-$ valgrind vips embed Gugg_coloured.jpg x.jpg 100 100 5000 5000 --extend
-mirror
-==32146== Memcheck, a memory error detector
-==32146== Copyright (C) 2002-2010, and GNU GPL'd, by Julian Seward et al.
-==32146== Using Valgrind-3.6.1-Debian and LibVEX; rerun with -h for copyright
-info
-==32146== Command: vips embed Gugg_coloured.jpg x.jpg 100 100 5000 5000
---extend mirror
-==32146== 
-==32146== Thread 2:
-==32146== Conditional jump or move depends on uninitialised value(s)
-==32146==    at 0x4F8ED7D: vips_sink_base_allocate (sink.c:257)
-==32146==    by 0x4F99BC2: vips_thread_allocate (threadpool.c:450)
-==32146==    by 0x4F99CB5: vips_thread_work_unit (threadpool.c:508)
-==32146==    by 0x4F99DF0: vips_thread_main_loop (threadpool.c:547)
-==32146==    by 0x55852B5: ??? (in
-/lib/x86_64-linux-gnu/libglib-2.0.so.0.3000.0)
-==32146==    by 0x5818EFB: start_thread (pthread_create.c:304)
-==32146==    by 0x5B0F89C: clone (clone.S:112)
-==32146== 
-
-it's the 'stop' member of SinkThreadState
-
-	/* Has work requested early termination?
-	 */
-	if( sstate->stop ) {
-		*stop = TRUE;
-
-		return( 0 );
-	}
-
-argh we have ->stop (a bool) and ->stop (a function)
-
-rename the function as stop_fn
-
-sstate is the "state" member of VipsThread
-
-which is created by the ->start member of the thread
-
-which is set by vips_threadpool_run()
-
-which is vips_thread_state_new(), see vips_sink_memory()
-
-which creates a VipsThreadState
-
-
-so .. move ->stop from SinkThreadState into the base class, VipsThreadState
-
-
-
 
 - don't do vips_image_write() at the end of a pipeline, instead try:
 
diff --git a/libvips/conversion/insert.c b/libvips/conversion/insert.c
index 4bc3120a..d179754d 100644
--- a/libvips/conversion/insert.c
+++ b/libvips/conversion/insert.c
@@ -57,8 +57,8 @@
  */
 
 /*
- */
 #define VIPS_DEBUG
+ */
 
 #ifdef HAVE_CONFIG_H
 #include <config.h>
diff --git a/libvips/include/vips/threadpool.h b/libvips/include/vips/threadpool.h
index a4fd67a5..a6eae612 100644
--- a/libvips/include/vips/threadpool.h
+++ b/libvips/include/vips/threadpool.h
@@ -79,6 +79,10 @@ typedef struct _VipsThreadState {
 	VipsRect pos;
 	int x, y;
 
+	/* Set in work to get the allocate to signal stop.
+	 */
+	gboolean stop;
+
 	/* The client data passed to the enclosing vips_threadpool_run().
 	 */
         void *a;
diff --git a/libvips/iofuncs/sink.c b/libvips/iofuncs/sink.c
index 3a73d6f6..1f05ed91 100644
--- a/libvips/iofuncs/sink.c
+++ b/libvips/iofuncs/sink.c
@@ -81,10 +81,6 @@ typedef struct _SinkThreadState {
 	 * parent_object.reg, it's defined on the outer image.
 	 */
 	VipsRegion *reg;
-
-	/* Set this in work to get the allocate to signal stop.
-	 */
-	gboolean stop;
 } SinkThreadState;
 
 typedef struct _SinkThreadStateClass {
@@ -184,11 +180,10 @@ sink_thread_state_init( SinkThreadState *state )
 {
 	state->seq = NULL;
 	state->reg = NULL;
-	state->stop = FALSE;
 }
 
-static VipsThreadState *
-sink_thread_state_new( VipsImage *im, void *a )
+VipsThreadState *
+vips_sink_thread_state_new( VipsImage *im, void *a )
 {
 	return( VIPS_THREAD_STATE( vips_object_new( 
 		sink_thread_state_get_type(), 
@@ -247,14 +242,13 @@ sink_init( Sink *sink,
 int 
 vips_sink_base_allocate( VipsThreadState *state, void *a, gboolean *stop )
 {
-	SinkThreadState *sstate = (SinkThreadState *) state;
 	SinkBase *sink_base = (SinkBase *) a;
 
 	VipsRect image, tile;
 
 	/* Has work requested early termination?
 	 */
-	if( sstate->stop ) {
+	if( state->stop ) {
 		*stop = TRUE;
 
 		return( 0 );
@@ -300,7 +294,7 @@ sink_work( VipsThreadState *state, void *a )
 
 	if( vips_region_prepare( sstate->reg, &state->pos ) ||
 		sink->generate_fn( sstate->reg, sstate->seq, 
-			sink->a, sink->b, &sstate->stop ) ) 
+			sink->a, sink->b, &state->stop ) ) 
 		return( -1 );
 
 	return( 0 );
@@ -379,7 +373,7 @@ vips_sink_tile( VipsImage *im,
 	vips_image_preeval( im );
 
 	result = vips_threadpool_run( im, 
-		sink_thread_state_new,
+		vips_sink_thread_state_new,
 		vips_sink_base_allocate, 
 		sink_work, 
 		vips_sink_base_progress, 
diff --git a/libvips/iofuncs/sink.h b/libvips/iofuncs/sink.h
index 5eb9339e..1df31684 100644
--- a/libvips/iofuncs/sink.h
+++ b/libvips/iofuncs/sink.h
@@ -58,6 +58,7 @@ typedef struct _SinkBase {
 /* Some function we can share.
  */
 void vips_sink_base_init( SinkBase *sink_base, VipsImage *image );
+VipsThreadState *vips_sink_thread_state_new( VipsImage *im, void *a );
 int vips_sink_base_allocate( VipsThreadState *state, void *a, gboolean *stop );
 int vips_sink_base_progress( void *a );
 
diff --git a/libvips/iofuncs/sinkmemory.c b/libvips/iofuncs/sinkmemory.c
index 93188a16..595f701e 100644
--- a/libvips/iofuncs/sinkmemory.c
+++ b/libvips/iofuncs/sinkmemory.c
@@ -51,35 +51,35 @@
 
 /* Per-call state.
  */
-typedef struct _Sink {
+typedef struct _SinkMemory {
 	SinkBase sink_base;
 
 	/* A big region for the image memory. All the threads write to this.
 	 */
 	VipsRegion *all;
-} Sink;
+} SinkMemory;
 
 static void
-sink_free( Sink *sink )
+sink_memory_free( SinkMemory *memory )
 {
-	VIPS_UNREF( sink->all );
+	VIPS_UNREF( memory->all );
 }
 
 static int
-sink_init( Sink *sink, VipsImage *im ) 
+sink_memory_init( SinkMemory *memory, VipsImage *im ) 
 {
 	VipsRect all;
 
-	vips_sink_base_init( &sink->sink_base, im );
+	vips_sink_base_init( &memory->sink_base, im );
 
 	all.left = 0;
 	all.top = 0;
 	all.width = im->Xsize;
 	all.height = im->Ysize;
 
-	if( !(sink->all = vips_region_new( im )) ||
-		vips_region_image( sink->all, &all ) ) {
-		sink_free( sink );
+	if( !(memory->all = vips_region_new( im )) ||
+		vips_region_image( memory->all, &all ) ) {
+		sink_memory_free( memory );
 		return( -1 );
 	}
 
@@ -87,19 +87,19 @@ sink_init( Sink *sink, VipsImage *im )
 }
 
 static int 
-sink_work( VipsThreadState *state, void *a )
+sink_memory_work( VipsThreadState *state, void *a )
 {
-	Sink *sink = (Sink *) a;
+	SinkMemory *memory = (SinkMemory *) a;
 
-	VIPS_DEBUG_MSG( "sink_work: %p "
+	VIPS_DEBUG_MSG( "sink_memory_work: %p "
 		"left = %d, top = %d, width = %d, height = %d\n", 
-		sink,
+		memory,
 		state->pos.left, 
 		state->pos.top, 
 		state->pos.width, 
 		state->pos.height ); 
 
-	if( vips_region_prepare_to( state->reg, sink->all, 
+	if( vips_region_prepare_to( state->reg, memory->all, 
 		&state->pos, state->pos.left, state->pos.top ) )
 		return( -1 );
 
@@ -109,7 +109,7 @@ sink_work( VipsThreadState *state, void *a )
 		state->pos.left, state->pos.top );
 	int i;
 
-	VIPS_DEBUG_MSG( "sink_work: %p\n", sink );
+	VIPS_DEBUG_MSG( "sink_memory_work: %p\n", memory );
 	for( i = 0; i < VIPS_IMAGE_SIZEOF_PEL( state->reg->im ); i++ )
 		printf( "\t%d) %02x\n", i, p[i] );
 }
@@ -132,7 +132,7 @@ sink_work( VipsThreadState *state, void *a )
 int
 vips_sink_memory( VipsImage *image ) 
 {
-	Sink sink;
+	SinkMemory memory;
 	int result;
 
 	VIPS_DEBUG_MSG( "vips_sink_memory: %p\n", image ); 
@@ -144,7 +144,7 @@ vips_sink_memory( VipsImage *image )
 	 */
 	image->Bbits = vips_format_sizeof( image->BandFmt ) << 3;
  
-	if( sink_init( &sink, image ) )
+	if( sink_memory_init( &memory, image ) )
 		return( -1 );
 
 	vips_image_preeval( image );
@@ -152,13 +152,13 @@ vips_sink_memory( VipsImage *image )
 	result = vips_threadpool_run( image, 
 		vips_thread_state_new,
 		vips_sink_base_allocate, 
-		sink_work, 
+		sink_memory_work, 
 		vips_sink_base_progress, 
-		&sink );
+		&memory );
 
 	vips_image_posteval( image );
 
-	sink_free( &sink );
+	sink_memory_free( &memory );
 
 	return( result );
 }
diff --git a/libvips/iofuncs/threadpool.c b/libvips/iofuncs/threadpool.c
index db11cffb..e8874b57 100644
--- a/libvips/iofuncs/threadpool.c
+++ b/libvips/iofuncs/threadpool.c
@@ -287,6 +287,7 @@ vips_thread_state_init( VipsThreadState *state )
 	VIPS_DEBUG_MSG( "vips_thread_state_init:\n" );
 
 	state->reg = NULL;
+	state->stop = FALSE;
 }
 
 void *