From 92460940337d14caf45c902ab47b8863ca41a9ae Mon Sep 17 00:00:00 2001
From: Kleis Auke Wolthuizen <github@kleisauke.nl>
Date: Tue, 30 Jun 2020 12:10:30 +0200
Subject: [PATCH] Fix function pointer cast issues

It is undefined behavior in C and C++ to cast a function pointer
to another type and call it that way. This does work in most native
platforms, however, despite it being UB, but in WASM it can fail.

See:
https://emscripten.org/docs/porting/guidelines/function_pointer_issues.html
---
 libvips/colour/profile_load.c           |  2 +-
 libvips/conversion/extract.c            | 24 +++++++++++++++++++++++
 libvips/conversion/tilecache.c          |  2 +-
 libvips/convolution/canny.c             |  2 +-
 libvips/deprecated/package.c            |  2 +-
 libvips/deprecated/rename.c             | 10 ++++++++++
 libvips/foreign/analyze2vips.c          | 10 +++++-----
 libvips/foreign/dzsave.c                |  4 ++--
 libvips/foreign/exif.c                  |  4 ++--
 libvips/foreign/foreign.c               | 10 +++++-----
 libvips/foreign/jpeg2vips.c             |  4 ++--
 libvips/foreign/magicksave.c            |  4 +---
 libvips/foreign/matlab.c                |  2 +-
 libvips/foreign/openexr2vips.c          |  2 +-
 libvips/foreign/radiance.c              |  6 +++---
 libvips/foreign/tiff2vips.c             |  4 ++--
 libvips/foreign/tiffsave.c              |  5 +----
 libvips/foreign/vips2tiff.c             |  8 ++++----
 libvips/include/vips/almostdeprecated.h |  4 ++++
 libvips/include/vips/image.h            | 12 ++++++------
 libvips/include/vips/memory.h           |  1 -
 libvips/include/vips/object.h           |  2 +-
 libvips/include/vips/type.h             |  1 +
 libvips/iofuncs/buffer.c                |  2 +-
 libvips/iofuncs/cache.c                 |  4 ++--
 libvips/iofuncs/gate.c                  |  8 +++++---
 libvips/iofuncs/generate.c              | 19 +++++++++---------
 libvips/iofuncs/header.c                |  6 +++---
 libvips/iofuncs/image.c                 | 22 ++++++++++-----------
 libvips/iofuncs/memory.c                | 26 +++++--------------------
 libvips/iofuncs/object.c                | 14 ++++++-------
 libvips/iofuncs/rect.c                  |  2 +-
 libvips/iofuncs/region.c                |  9 ++++-----
 libvips/iofuncs/sink.c                  |  2 +-
 libvips/iofuncs/sinkdisc.c              |  2 +-
 libvips/iofuncs/sinkmemory.c            |  2 +-
 libvips/iofuncs/sinkscreen.c            | 14 ++++++-------
 libvips/iofuncs/source.c                |  6 +++---
 libvips/iofuncs/target.c                |  2 +-
 libvips/iofuncs/type.c                  | 24 ++++++++++++++++-------
 libvips/iofuncs/util.c                  | 12 ++++++------
 libvips/iofuncs/vips.c                  |  4 ++--
 libvips/iofuncs/window.c                |  4 ++--
 43 files changed, 167 insertions(+), 142 deletions(-)

diff --git a/libvips/colour/profile_load.c b/libvips/colour/profile_load.c
index c7fdb4a5a6..4966cb79ed 100644
--- a/libvips/colour/profile_load.c
+++ b/libvips/colour/profile_load.c
@@ -96,7 +96,7 @@ vips_profile_load_build( VipsObject *object )
 	else if( (data = vips__file_read_name( load->name, 
 		vips__icc_dir(), &length )) ) 
 		profile = vips_blob_new( 
-			(VipsCallbackFn) g_free, data, length );
+			(VipsCallbackFn) vips_area_free_cb, data, length );
 	else {
 		vips_error( class->nickname, 
 			_( "unable to load profile \"%s\"" ), load->name );
diff --git a/libvips/conversion/extract.c b/libvips/conversion/extract.c
index 7a60f877ad..e2c8ec7240 100644
--- a/libvips/conversion/extract.c
+++ b/libvips/conversion/extract.c
@@ -172,6 +172,14 @@ vips_extract_area_build( VipsObject *object )
 	return( 0 );
 }
 
+#ifdef __EMSCRIPTEN__
+static void
+vips_crop_class_init_adapter( VipsExtractAreaClass *class, void *dummy )
+{
+	vips_extract_area_class_init( class );
+}
+#endif
+
 static void
 vips_extract_area_class_init( VipsExtractAreaClass *class )
 {
@@ -226,6 +234,14 @@ vips_extract_area_class_init( VipsExtractAreaClass *class )
 
 }
 
+#ifdef __EMSCRIPTEN__
+static void
+vips_crop_init_adapter( VipsExtractArea *extract, void *dummy )
+{
+	vips_extract_area_init( extract );
+}
+#endif
+
 static void
 vips_extract_area_init( VipsExtractArea *extract )
 {
@@ -275,12 +291,20 @@ vips_crop_get_type( void )
 			sizeof( VipsExtractAreaClass ),
 			NULL,           /* base_init */
 			NULL,           /* base_finalize */
+#ifdef __EMSCRIPTEN__
+			(GClassInitFunc) vips_crop_class_init_adapter,
+#else
 			(GClassInitFunc) vips_extract_area_class_init,
+#endif
 			NULL,           /* class_finalize */
 			NULL,           /* class_data */
 			sizeof( VipsExtractArea ),
 			32,             /* n_preallocs */
+#ifdef __EMSCRIPTEN__
+			(GInstanceInitFunc) vips_crop_init_adapter,
+#else
 			(GInstanceInitFunc) vips_extract_area_init,
+#endif
 		};
 
 		type = g_type_register_static( VIPS_TYPE_CONVERSION, 
diff --git a/libvips/conversion/tilecache.c b/libvips/conversion/tilecache.c
index c458254fea..e89853db96 100644
--- a/libvips/conversion/tilecache.c
+++ b/libvips/conversion/tilecache.c
@@ -473,7 +473,7 @@ vips_tile_destroy( VipsTile *tile )
 
 	VIPS_UNREF( tile->region );
 
-	vips_free( tile );
+	g_free( tile );
 }
 
 static void
diff --git a/libvips/convolution/canny.c b/libvips/convolution/canny.c
index ca96f6b1fd..bd732c3711 100644
--- a/libvips/convolution/canny.c
+++ b/libvips/convolution/canny.c
@@ -225,7 +225,7 @@ vips_canny_polar( VipsImage **args, VipsImage **out )
 {
 	static GOnce once = G_ONCE_INIT;
 
-	g_once( &once, (GThreadFunc) vips_atan2_init, NULL );
+	g_once( &once, vips_atan2_init, NULL );
 
 	*out = vips_image_new();
 	if( vips_image_pipeline_array( *out, 
diff --git a/libvips/deprecated/package.c b/libvips/deprecated/package.c
index fb5b4dbc04..2549b2d0a2 100644
--- a/libvips/deprecated/package.c
+++ b/libvips/deprecated/package.c
@@ -910,7 +910,7 @@ im_free_vargv( im_function *fn, im_object *vargv )
 			/* If there is local storage, free it.
 			 */
 			if( fn->argv[i].desc->size != 0 )
-				vips_free( vargv[i] );
+				g_free( vargv[i] );
 
 			/* NULL out pointer.
 			 */
diff --git a/libvips/deprecated/rename.c b/libvips/deprecated/rename.c
index ad3eaa226f..3c7761907b 100644
--- a/libvips/deprecated/rename.c
+++ b/libvips/deprecated/rename.c
@@ -813,3 +813,13 @@ vips_autorot_get_angle( VipsImage *im )
 	return( VIPS_ANGLE_D0 );
 }
 
+/* The old vips_free(), now replaced by g_free() and vips_area_free_cb().
+ */
+int
+vips_free( void *buf )
+{
+	g_free( buf );
+
+	return( 0 );
+}
+
diff --git a/libvips/foreign/analyze2vips.c b/libvips/foreign/analyze2vips.c
index c3802d8c89..9f17f1ff2b 100644
--- a/libvips/foreign/analyze2vips.c
+++ b/libvips/foreign/analyze2vips.c
@@ -309,7 +309,7 @@ read_header( const char *header )
 	if( len != sizeof( struct dsr ) ) {
 		vips_error( "analyze2vips", 
 			"%s", _( "header file size incorrect" ) );
-		vips_free( d );
+		g_free( d );
 		return( NULL );
 	}
 
@@ -354,7 +354,7 @@ read_header( const char *header )
 	if( (int) len != d->hk.sizeof_hdr ) {
 		vips_error( "analyze2vips", 
 			"%s", _( "header size incorrect" ) );
-		vips_free( d );
+		g_free( d );
 		return( NULL );
 	}
 
@@ -444,7 +444,7 @@ attach_meta( VipsImage *out, struct dsr *d )
 	int i;
 
 	vips_image_set_blob( out, "dsr", 
-		(VipsCallbackFn) vips_free, d, d->hk.sizeof_hdr );
+		(VipsCallbackFn) vips_area_free_cb, d, d->hk.sizeof_hdr );
 
 	for( i = 0; i < VIPS_NUMBER( dsr_header ); i++ ) {
 		switch( dsr_header[i].type ) {
@@ -514,7 +514,7 @@ vips__isanalyze( const char *filename )
 	result = get_vips_properties( d, &width, &height, &bands, &fmt );
 	vips_error_thaw();
 
-	vips_free( d );
+	g_free( d );
 
 	return( result == 0 );
 }
@@ -538,7 +538,7 @@ vips__analyze_read_header( const char *filename, VipsImage *out )
 #endif /*DEBUG*/
 
 	if( get_vips_properties( d, &width, &height, &bands, &fmt ) ) {
-		vips_free( d );
+		g_free( d );
 		return( -1 );
 	}
 
diff --git a/libvips/foreign/dzsave.c b/libvips/foreign/dzsave.c
index d0e2a98ac7..c793668e15 100644
--- a/libvips/foreign/dzsave.c
+++ b/libvips/foreign/dzsave.c
@@ -275,7 +275,7 @@ vips_gsf_tree_new( GsfOutput *out, gint deflate_level )
 }
 
 static void *
-vips_gsf_child_by_name_sub( VipsGsfDirectory *dir, const char *name )
+vips_gsf_child_by_name_sub( VipsGsfDirectory *dir, const char *name, void *b )
 {
 	if( strcmp( dir->name, name ) == 0 )
 		return( dir );
@@ -2692,7 +2692,7 @@ vips_foreign_save_dz_buffer_build( VipsObject *object )
 		gsf_output_memory_get_bytes( GSF_OUTPUT_MEMORY( dz->out ) ),
 		olen ); 
 
-	blob = vips_blob_new( (VipsCallbackFn) g_free, obuf, olen );
+	blob = vips_blob_new( (VipsCallbackFn) vips_area_free_cb, obuf, olen );
 	g_object_set( object, "buffer", blob, NULL );
 	vips_area_unref( VIPS_AREA( blob ) );
 
diff --git a/libvips/foreign/exif.c b/libvips/foreign/exif.c
index 6e6c442d8a..3dc35ec510 100644
--- a/libvips/foreign/exif.c
+++ b/libvips/foreign/exif.c
@@ -1258,7 +1258,7 @@ vips_exif_exif_entry( ExifEntry *entry, VipsExifRemove *ve )
 }
 
 static void *
-vips_exif_exif_remove( ExifEntry *entry, VipsExifRemove *ve )
+vips_exif_exif_remove( ExifEntry *entry, VipsExifRemove *ve, void *b )
 {
 #ifdef DEBUG
 {
@@ -1405,7 +1405,7 @@ vips__exif_update( VipsImage *image )
 #endif /*DEBUG*/
 
 	vips_image_set_blob( image, VIPS_META_EXIF_NAME, 
-		(VipsCallbackFn) vips_free, data, length );
+		(VipsCallbackFn) vips_area_free_cb, data, length );
 
 	exif_data_free( ed );
 
diff --git a/libvips/foreign/foreign.c b/libvips/foreign/foreign.c
index f7fdd49637..0459c47fb4 100644
--- a/libvips/foreign/foreign.c
+++ b/libvips/foreign/foreign.c
@@ -390,7 +390,7 @@ file_add_class( VipsForeignClass *class, GSList **files )
 }
 
 static gint
-file_compare( VipsForeignClass *a, VipsForeignClass *b )
+file_compare( VipsForeignClass *a, VipsForeignClass *b, void *user_data )
 {
         return( b->priority - a->priority );
 }
@@ -479,7 +479,7 @@ vips_foreign_load_summary_class( VipsObjectClass *object_class, VipsBuf *buf )
  */
 static void *
 vips_foreign_find_load_sub( VipsForeignLoadClass *load_class, 
-	const char *filename )
+	const char *filename, void *b )
 {
 	VipsObjectClass *object_class = VIPS_OBJECT_CLASS( load_class );
 	VipsForeignClass *class = VIPS_FOREIGN_CLASS( load_class );
@@ -1763,7 +1763,7 @@ vips_foreign_save_init( VipsForeignSave *save )
  */
 static void *
 vips_foreign_find_save_sub( VipsForeignSaveClass *save_class, 
-	const char *filename )
+	const char *filename, void *b )
 {
 	VipsObjectClass *object_class = VIPS_OBJECT_CLASS( save_class );
 	VipsForeignClass *class = VIPS_FOREIGN_CLASS( save_class );
@@ -1919,7 +1919,7 @@ vips_foreign_save( VipsImage *in, const char *name, ... )
  */
 static void *
 vips_foreign_find_save_target_sub( VipsForeignSaveClass *save_class, 
-	const char *suffix )
+	const char *suffix, void *b )
 {
 	VipsObjectClass *object_class = VIPS_OBJECT_CLASS( save_class );
 	VipsForeignClass *class = VIPS_FOREIGN_CLASS( save_class );
@@ -1977,7 +1977,7 @@ vips_foreign_find_save_target( const char *name )
  */
 static void *
 vips_foreign_find_save_buffer_sub( VipsForeignSaveClass *save_class, 
-	const char *suffix )
+	const char *suffix, void *b )
 {
 	VipsObjectClass *object_class = VIPS_OBJECT_CLASS( save_class );
 	VipsForeignClass *class = VIPS_FOREIGN_CLASS( save_class );
diff --git a/libvips/foreign/jpeg2vips.c b/libvips/foreign/jpeg2vips.c
index 26accc4091..c1e87fd580 100644
--- a/libvips/foreign/jpeg2vips.c
+++ b/libvips/foreign/jpeg2vips.c
@@ -334,7 +334,7 @@ readjpeg_free( ReadJpeg *jpeg )
 }
 
 static void
-readjpeg_close_cb( VipsObject *object, ReadJpeg *jpeg )
+readjpeg_close_cb( VipsImage *image, ReadJpeg *jpeg )
 {
 	(void) readjpeg_free( jpeg );
 }
@@ -728,7 +728,7 @@ read_jpeg_header( ReadJpeg *jpeg, VipsImage *out )
 		}
 
 		vips_image_set_blob( out, VIPS_META_ICC_NAME, 
-			(VipsCallbackFn) vips_free, data, data_length );
+			(VipsCallbackFn) vips_area_free_cb, data, data_length );
 	}
 
 	return( 0 );
diff --git a/libvips/foreign/magicksave.c b/libvips/foreign/magicksave.c
index 102252d960..bc1d39872a 100644
--- a/libvips/foreign/magicksave.c
+++ b/libvips/foreign/magicksave.c
@@ -593,9 +593,7 @@ vips_foreign_save_magick_buffer_build( VipsObject *object )
 		return( -1 );
 	}
 
-	/* obuf is a g_free() buffer, not vips_free().
-	 */
-	blob = vips_blob_new( (VipsCallbackFn) g_free, obuf, olen );
+	blob = vips_blob_new( (VipsCallbackFn) vips_area_free_cb, obuf, olen );
 	g_object_set( buffer, "buffer", blob, NULL );
 	vips_area_unref( VIPS_AREA( blob ) );
 
diff --git a/libvips/foreign/matlab.c b/libvips/foreign/matlab.c
index 5335647b11..dde57f2e47 100644
--- a/libvips/foreign/matlab.c
+++ b/libvips/foreign/matlab.c
@@ -92,7 +92,7 @@ read_destroy( Read *read )
 	VIPS_FREEF( Mat_VarFree, read->var );
 	VIPS_FREEF( Mat_Close, read->mat );
 
-	vips_free( read );
+	g_free( read );
 }
 
 static Read *
diff --git a/libvips/foreign/openexr2vips.c b/libvips/foreign/openexr2vips.c
index e36b477e01..523b72b576 100644
--- a/libvips/foreign/openexr2vips.c
+++ b/libvips/foreign/openexr2vips.c
@@ -139,7 +139,7 @@ read_destroy( VipsImage *out, Read *read )
 
 	read_close( read ); 
 
-	vips_free( read );
+	g_free( read );
 }
 
 static Read *
diff --git a/libvips/foreign/radiance.c b/libvips/foreign/radiance.c
index d5ba070b81..c9889b148e 100644
--- a/libvips/foreign/radiance.c
+++ b/libvips/foreign/radiance.c
@@ -739,13 +739,13 @@ vips__rad_israd( VipsSource *source )
 }
 
 static void
-read_destroy( VipsObject *object, Read *read )
+read_destroy( VipsImage *image, Read *read )
 {
 	VIPS_UNREF( read->sbuf );
 }
 
 static void
-read_minimise_cb( VipsObject *object, Read *read )
+read_minimise_cb( VipsImage *image, Read *read )
 {
 	if( read->sbuf )
 		vips_source_minimise( read->sbuf->source );
@@ -994,7 +994,7 @@ write_destroy( Write *write )
 	VIPS_FREE( write->line );
 	VIPS_UNREF( write->target );
 
-	vips_free( write );
+	g_free( write );
 }
 
 static Write *
diff --git a/libvips/foreign/tiff2vips.c b/libvips/foreign/tiff2vips.c
index 6bde6f31ed..cac7139638 100644
--- a/libvips/foreign/tiff2vips.c
+++ b/libvips/foreign/tiff2vips.c
@@ -522,7 +522,7 @@ rtiff_free( Rtiff *rtiff )
 }
 
 static void
-rtiff_close_cb( VipsObject *object, Rtiff *rtiff )
+rtiff_close_cb( VipsImage *image, Rtiff *rtiff )
 {
 	rtiff_free( rtiff ); 
 }
@@ -1926,7 +1926,7 @@ rtiff_fill_region( VipsRegion *out,
 static int
 rtiff_seq_stop( void *seq, void *a, void *b )
 {
-	vips_free( seq );
+	g_free( seq );
 
 	return( 0 );
 }
diff --git a/libvips/foreign/tiffsave.c b/libvips/foreign/tiffsave.c
index 83d9fd94ed..33bc65ea61 100644
--- a/libvips/foreign/tiffsave.c
+++ b/libvips/foreign/tiffsave.c
@@ -503,10 +503,7 @@ vips_foreign_save_tiff_buffer_build( VipsObject *object )
 		tiff->subifd ) )
 		return( -1 );
 
-	/* vips__tiff_write_buf() makes a buffer that needs g_free(), not
-	 * vips_free().
-	 */
-	blob = vips_blob_new( (VipsCallbackFn) g_free, obuf, olen );
+	blob = vips_blob_new( (VipsCallbackFn) vips_area_free_cb, obuf, olen );
 	g_object_set( object, "buffer", blob, NULL );
 	vips_area_unref( VIPS_AREA( blob ) );
 
diff --git a/libvips/foreign/vips2tiff.c b/libvips/foreign/vips2tiff.c
index 5ff5834dc4..9a6244a9e0 100644
--- a/libvips/foreign/vips2tiff.c
+++ b/libvips/foreign/vips2tiff.c
@@ -979,9 +979,9 @@ wtiff_free( Wtiff *wtiff )
 	wtiff_delete_temps( wtiff );
 
 	VIPS_UNREF( wtiff->ready );
-	VIPS_FREEF( vips_free, wtiff->tbuf );
+	VIPS_FREE( wtiff->tbuf );
 	VIPS_FREEF( layer_free_all, wtiff->layer );
-	VIPS_FREEF( vips_free, wtiff->icc_profile );
+	VIPS_FREE( wtiff->icc_profile );
 	VIPS_FREE( wtiff->filename );
 	VIPS_FREE( wtiff );
 }
@@ -1888,11 +1888,11 @@ wtiff_copy_tiff( Wtiff *wtiff, TIFF *out, TIFF *in )
 		len = TIFFReadEncodedTile( in, tile, buf, -1 );
 		if( len < 0 ||
 			TIFFWriteEncodedTile( out, tile, buf, len ) < 0 ) {
-			vips_free( buf );
+			g_free( buf );
 			return( -1 );
 		}
 	}
-	vips_free( buf );
+	g_free( buf );
 
 	return( 0 );
 }
diff --git a/libvips/include/vips/almostdeprecated.h b/libvips/include/vips/almostdeprecated.h
index 1bde7c8482..e397c27f62 100644
--- a/libvips/include/vips/almostdeprecated.h
+++ b/libvips/include/vips/almostdeprecated.h
@@ -294,6 +294,10 @@ void vips_vinfo( const char *domain, const char *fmt, va_list ap );
 
 VipsAngle vips_autorot_get_angle( VipsImage *image );
 
+/* iofuncs
+ */
+int vips_free( void *buf );
+
 #ifdef __cplusplus
 }
 #endif /*__cplusplus*/
diff --git a/libvips/include/vips/image.h b/libvips/include/vips/image.h
index d400ffc4a4..01b5996889 100644
--- a/libvips/include/vips/image.h
+++ b/libvips/include/vips/image.h
@@ -319,27 +319,27 @@ typedef struct _VipsImageClass {
 
 	/* Evaluation is starting.
 	 */
-	void (*preeval)( VipsImage *image, VipsProgress *progress );
+	void (*preeval)( VipsImage *image, VipsProgress *progress, void *data );
 
 	/* Evaluation progress.
 	 */
-	void (*eval)( VipsImage *image, VipsProgress *progress );
+	void (*eval)( VipsImage *image, VipsProgress *progress, void *data );
 
 	/* Evaluation is ending.
 	 */
-	void (*posteval)( VipsImage *image, VipsProgress *progress );
+	void (*posteval)( VipsImage *image, VipsProgress *progress, void *data );
 
 	/* An image has been written to. 
 	 * Used by eg. vips_image_new_mode("x.jpg", "w") to do the 
 	 * final write to jpeg.
 	 * Set *result to non-zero to indicate an error on write.
 	 */
-	void (*written)( VipsImage *image, int *result );
+	void (*written)( VipsImage *image, int *result, void *data );
 
 	/* An image has been modified in some way and all caches 
 	 * need dropping. 
 	 */
-	void (*invalidate)( VipsImage *image );
+	void (*invalidate)( VipsImage *image, void *data );
 
 	/* Minimise this pipeline. 
 	 *
@@ -349,7 +349,7 @@ typedef struct _VipsImageClass {
 	 *
 	 * See vips_tilecache().
 	 */
-	void (*minimise)( VipsImage *image );
+	void (*minimise)( VipsImage *image, void *data );
 
 } VipsImageClass;
 
diff --git a/libvips/include/vips/memory.h b/libvips/include/vips/memory.h
index 99b26e8fef..6469db9fb5 100644
--- a/libvips/include/vips/memory.h
+++ b/libvips/include/vips/memory.h
@@ -66,7 +66,6 @@ G_STMT_START { \
 
 void *vips_malloc( VipsObject *object, size_t size );
 char *vips_strdup( VipsObject *object, const char *str );
-int vips_free( void *buf );
 
 void vips_tracked_free( void *s );
 void *vips_tracked_malloc( size_t size );
diff --git a/libvips/include/vips/object.h b/libvips/include/vips/object.h
index ff500a61cc..f83ee46130 100644
--- a/libvips/include/vips/object.h
+++ b/libvips/include/vips/object.h
@@ -455,7 +455,7 @@ struct _VipsObjectClass {
 
 	/* Just after build ... the object is fully ready for work. 
 	 */
-	int (*postbuild)( VipsObject *object );
+	int (*postbuild)( VipsObject *object, void *data );
 
 	/* Try to print something about the class, handy for help displays.
 	 * Keep to one line.
diff --git a/libvips/include/vips/type.h b/libvips/include/vips/type.h
index ba7512ea1f..4f73d43e0b 100644
--- a/libvips/include/vips/type.h
+++ b/libvips/include/vips/type.h
@@ -92,6 +92,7 @@ typedef struct _VipsArea {
 } VipsArea;
 
 VipsArea *vips_area_copy( VipsArea *area );
+int vips_area_free_cb( void *mem, VipsArea *area );
 void vips_area_unref( VipsArea *area );
 
 VipsArea *vips_area_new( VipsCallbackFn free_fn, void *data );
diff --git a/libvips/iofuncs/buffer.c b/libvips/iofuncs/buffer.c
index 87efa49f41..4462087b12 100644
--- a/libvips/iofuncs/buffer.c
+++ b/libvips/iofuncs/buffer.c
@@ -153,7 +153,7 @@ vips_buffer_dump( VipsBuffer *buffer, size_t *reserve, size_t *alive )
 
 #ifdef DEBUG_CREATE
 static void *
-vips_buffer_cache_dump( VipsBufferCache *cache )
+vips_buffer_cache_dump( VipsBufferCache *cache, void *a, void *b )
 {
 	printf( "VipsBufferCache: %p\n", cache );
 	printf( "\t%d buffers\n", g_slist_length( cache->buffers ) );
diff --git a/libvips/iofuncs/cache.c b/libvips/iofuncs/cache.c
index 3ec4096680..339bbb92e1 100644
--- a/libvips/iofuncs/cache.c
+++ b/libvips/iofuncs/cache.c
@@ -453,7 +453,7 @@ vips_operation_equal( VipsOperation *a, VipsOperation *b )
 }
 
 void *
-vips__cache_once_init( void )
+vips__cache_once_init( void *data )
 {
 	vips_cache_lock = vips_g_mutex_new();
 
@@ -469,7 +469,7 @@ vips__cache_init( void )
 {
 	static GOnce once = G_ONCE_INIT;
 
-	VIPS_ONCE( &once, (GThreadFunc) vips__cache_once_init, NULL );
+	VIPS_ONCE( &once, vips__cache_once_init, NULL );
 }
 
 static void *
diff --git a/libvips/iofuncs/gate.c b/libvips/iofuncs/gate.c
index 0b45ec3eee..5e38d31536 100644
--- a/libvips/iofuncs/gate.c
+++ b/libvips/iofuncs/gate.c
@@ -210,8 +210,8 @@ vips__thread_profile_init_cb( VipsThreadProfile *profile )
 	vips_thread_profile_free( profile );
 }
 
-static void
-vips__thread_profile_init( void )
+static void *
+vips__thread_profile_init( void *data )
 {
 #ifdef HAVE_PRIVATE_INIT
 	static GPrivate private = 
@@ -223,6 +223,8 @@ vips__thread_profile_init( void )
 		vips_thread_profile_key = g_private_new( 
 			(GDestroyNotify) vips__thread_profile_init_cb );
 #endif
+
+	return( NULL );
 }
 
 static VipsThreadGate *
@@ -245,7 +247,7 @@ vips__thread_profile_attach( const char *thread_name )
 
 	VipsThreadProfile *profile;
 
-	VIPS_ONCE( &once, (GThreadFunc) vips__thread_profile_init, NULL );
+	VIPS_ONCE( &once, vips__thread_profile_init, NULL );
 
 	VIPS_DEBUG_MSG( "vips__thread_profile_attach: %s\n", thread_name ); 
 
diff --git a/libvips/iofuncs/generate.c b/libvips/iofuncs/generate.c
index 65be8d9cf1..8e8e53a484 100644
--- a/libvips/iofuncs/generate.c
+++ b/libvips/iofuncs/generate.c
@@ -148,7 +148,7 @@ vips__link_make( VipsImage *image_up, VipsImage *image_down )
 }
 
 static void *
-vips__link_break( VipsImage *image_up, VipsImage *image_down )
+vips__link_break( VipsImage *image_up, VipsImage *image_down, void *b )
 {
 	g_assert( image_up );
 	g_assert( image_down );
@@ -171,9 +171,9 @@ vips__link_break( VipsImage *image_up, VipsImage *image_down )
 }
 
 static void *
-vips__link_break_rev( VipsImage *image_down, VipsImage *image_up )
+vips__link_break_rev( VipsImage *image_down, VipsImage *image_up, void *b )
 {
-	return( vips__link_break( image_up, image_down ) );
+	return( vips__link_break( image_up, image_down, b ) );
 }
 
 /* A VipsImage is going ... break all links.
@@ -203,7 +203,7 @@ typedef struct _LinkMap {
 } LinkMap;
 
 static void *
-vips__link_mapp( VipsImage *image, LinkMap *map ) 
+vips__link_mapp( VipsImage *image, LinkMap *map, void *b ) 
 {
 	void *res;
 
@@ -222,7 +222,7 @@ vips__link_mapp( VipsImage *image, LinkMap *map )
 }
 
 static void *
-vips__link_map_cb( VipsImage *image, GSList **images )
+vips__link_map_cb( VipsImage *image, GSList **images, void *b )
 {
 	*images = g_slist_prepend( *images, image );
 
@@ -265,7 +265,7 @@ vips__link_map( VipsImage *image, gboolean upstream,
 	serial += 1;
 	map.serial = serial;
 
-	vips__link_mapp( image, &map ); 
+	vips__link_mapp( image, &map, NULL ); 
 
 	for( p = images; p; p = p->next ) 
 		g_object_ref( p->data );
@@ -494,7 +494,7 @@ vips_stop_many( void *seq, void *a, void *b )
 
 		for( i = 0; ar[i]; i++ )
 			g_object_unref( ar[i] );
-		vips_free( (char *) ar );
+		g_free( (char *) ar );
 	}
 
 	return( 0 );
@@ -630,7 +630,7 @@ vips_allocate_input_array( VipsImage *out, ... )
 /* A write function for VIPS images. Just write() the pixel data.
  */
 static int
-write_vips( VipsRegion *region, VipsRect *area, void *a, void *b )
+write_vips( VipsRegion *region, VipsRect *area, void *a )
 {
 	size_t nwritten, count;
 	void *buf;
@@ -753,8 +753,7 @@ vips_image_generate( VipsImage *image,
                         return( -1 );
 
                 if( image->dtype == VIPS_IMAGE_OPENOUT ) 
-			res = vips_sink_disc( image,
-				(VipsRegionWrite) write_vips, NULL );
+			res = vips_sink_disc( image, write_vips, NULL );
                 else 
                         res = vips_sink_memory( image );
 
diff --git a/libvips/iofuncs/header.c b/libvips/iofuncs/header.c
index 4109b5d483..b10235b322 100644
--- a/libvips/iofuncs/header.c
+++ b/libvips/iofuncs/header.c
@@ -235,7 +235,7 @@ vips_format_sizeof_unsafe( VipsBandFormat format )
 /* Check that this meta is on the hash table.
  */
 static void *
-meta_sanity_on_hash( VipsMeta *meta, VipsImage *im )
+meta_sanity_on_hash( VipsMeta *meta, VipsImage *im, void *b )
 {
 	VipsMeta *found;
 
@@ -970,7 +970,7 @@ vips_image_init_fields( VipsImage *image,
 }
 
 static void *
-meta_cp_field( VipsMeta *meta, VipsImage *dst )
+meta_cp_field( VipsMeta *meta, VipsImage *dst, void *b )
 {
 #ifdef DEBUG
 {
@@ -1569,7 +1569,7 @@ vips_image_set_blob_copy( VipsImage *image,
 	((unsigned char *) data_copy)[length] = '\0';
 
 	vips_image_set_blob( image, 
-		name, (VipsCallbackFn) vips_free, data_copy, length );
+		name, (VipsCallbackFn) vips_area_free_cb, data_copy, length );
 }
 
 /** 
diff --git a/libvips/iofuncs/image.c b/libvips/iofuncs/image.c
index c5d51b23a3..f2acf931dc 100644
--- a/libvips/iofuncs/image.c
+++ b/libvips/iofuncs/image.c
@@ -651,7 +651,7 @@ vips_image_summary( VipsObject *object, VipsBuf *buf )
 }
 
 static void *
-vips_image_sanity_upstream( VipsImage *up, VipsImage *down )
+vips_image_sanity_upstream( VipsImage *up, VipsImage *down, void *b )
 {
 	if( !g_slist_find( up->downstream, down ) ||
 		!g_slist_find( down->upstream, up ) )
@@ -661,9 +661,9 @@ vips_image_sanity_upstream( VipsImage *up, VipsImage *down )
 }
 
 static void *
-vips_image_sanity_downstream( VipsImage *down, VipsImage *up )
+vips_image_sanity_downstream( VipsImage *down, VipsImage *up, void *b )
 {
-	return( vips_image_sanity_upstream( up, down ) );
+	return( vips_image_sanity_upstream( up, down, b ) );
 }
 
 static void
@@ -738,7 +738,7 @@ vips_image_rewind( VipsObject *object )
 /* From "written" callback: save to image->filename using VipsForeign.
  */
 static void
-vips_image_save_cb( VipsImage *image, int *result )
+vips_image_save_cb( VipsImage *image, int *result, void *data )
 {
 	if( vips_foreign_save( image, image->filename, NULL ) )
 		*result = -1;
@@ -786,7 +786,7 @@ vips_image_eval_cb( VipsImage *image, VipsProgress *progress, int *last )
 }
 
 static void
-vips_image_posteval_cb( VipsImage *image, VipsProgress *progress )
+vips_image_posteval_cb( VipsImage *image, VipsProgress *progress, void *data )
 {
 	/* Spaces at end help to erase the %complete message we overwrite.
 	 */
@@ -1016,7 +1016,7 @@ vips_image_build( VipsObject *object )
 }
 
 static void *
-vips_image_real_invalidate_cb( VipsRegion *reg )
+vips_image_real_invalidate_cb( VipsRegion *reg, void *a, void *b )
 {
 	vips_region_invalidate( reg );
 
@@ -1024,7 +1024,7 @@ vips_image_real_invalidate_cb( VipsRegion *reg )
 }
 
 static void 
-vips_image_real_invalidate( VipsImage *image )
+vips_image_real_invalidate( VipsImage *image, void *data )
 {
 	VIPS_DEBUG_MSG( "vips_image_real_invalidate: %p\n", image );
 
@@ -1041,13 +1041,13 @@ vips_image_real_invalidate( VipsImage *image )
 }
 
 static void 
-vips_image_real_minimise( VipsImage *image )
+vips_image_real_minimise( VipsImage *image, void *data )
 {
 	VIPS_DEBUG_MSG( "vips_image_real_minimise: %p\n", image );
 }
 
 static void 
-vips_image_real_written( VipsImage *image, int *result )
+vips_image_real_written( VipsImage *image, int *result, void *data )
 {
 	VIPS_DEBUG_MSG( "vips_image_real_written: %p\n", image );
 
@@ -1390,7 +1390,7 @@ vips_image_invalidate( VipsImage *image )
 }
 
 static void *
-vips_image_invalidate_all_cb( VipsImage *image )
+vips_image_invalidate_all_cb( VipsImage *image, void *a, void *b )
 {
 	vips_image_invalidate( image );
 
@@ -1430,7 +1430,7 @@ vips_image_minimise( VipsImage *image )
 }
 
 static void *
-vips_image_minimise_all_cb( VipsImage *image )
+vips_image_minimise_all_cb( VipsImage *image, void *a, void *b )
 {
 	vips_image_minimise( image );
 
diff --git a/libvips/iofuncs/memory.c b/libvips/iofuncs/memory.c
index 2233b17b83..b2fa30aa84 100644
--- a/libvips/iofuncs/memory.c
+++ b/libvips/iofuncs/memory.c
@@ -215,24 +215,6 @@ vips_strdup( VipsObject *object, const char *str )
 	return( str_dup );
 }
 
-/**
- * vips_free:
- * @buf: memory to free
- *
- * Frees memory with g_free() and returns 0. Handy for callbacks.
- *
- * See also: vips_malloc().
- *
- * Returns: 0
- */
-int
-vips_free( void *buf )
-{
-	g_free( buf );
-
-	return( 0 );
-}
-
 /**
  * vips_tracked_free:
  * @s: (transfer full): memory to free
@@ -273,10 +255,12 @@ vips_tracked_free( void *s )
 	VIPS_GATE_FREE( size ); 
 }
 
-static void
-vips_tracked_init_mutex( void )
+static void *
+vips_tracked_init_mutex( void *data )
 {
 	vips_tracked_mutex = vips_g_mutex_new(); 
+
+	return( NULL );
 }
 
 static void
@@ -285,7 +269,7 @@ vips_tracked_init( void )
 	static GOnce vips_tracked_once = G_ONCE_INIT;
 
 	VIPS_ONCE( &vips_tracked_once, 
-		(GThreadFunc) vips_tracked_init_mutex, NULL );
+		vips_tracked_init_mutex, NULL );
 }
 
 /**
diff --git a/libvips/iofuncs/object.c b/libvips/iofuncs/object.c
index bbb6ac3c16..36cccdf338 100644
--- a/libvips/iofuncs/object.c
+++ b/libvips/iofuncs/object.c
@@ -1460,7 +1460,7 @@ vips_object_real_build( VipsObject *object )
 }
 
 static int
-vips_object_real_postbuild( VipsObject *object )
+vips_object_real_postbuild( VipsObject *object, void *data )
 {
 #ifdef DEBUG
 	printf( "vips_object_real_postbuild: " ); 
@@ -1701,7 +1701,7 @@ traverse_find_required_priority( void *data, void *a, void *b )
 }
 
 static gint
-traverse_sort( gconstpointer a, gconstpointer b )
+traverse_sort( gconstpointer a, gconstpointer b, void *user_data )
 {
 	VipsArgumentClass *class1 = (VipsArgumentClass *) a;
 	VipsArgumentClass *class2 = (VipsArgumentClass *) b;
@@ -1803,7 +1803,7 @@ vips_object_class_install_argument( VipsObjectClass *object_class,
 	argument_table_traverse = g_slist_prepend(
 		argument_table_traverse, argument_class );
 	argument_table_traverse = g_slist_sort(
-		argument_table_traverse, traverse_sort );
+		argument_table_traverse, (GCompareFunc) traverse_sort );
 	VIPS_SWAP( GSList *, 
 		argument_table_traverse, 
 		object_class->argument_table_traverse ); 
@@ -3045,7 +3045,7 @@ typedef struct {
 } VipsObjectLocal;
 
 static void
-vips_object_local_array_cb( GObject *parent, VipsObjectLocal *local )
+vips_object_local_array_cb( VipsObject *parent, VipsObjectLocal *local )
 {
 	int i;
 
@@ -3111,7 +3111,7 @@ vips_object_set_static( VipsObject *object, gboolean static_object )
 }
 
 static void *
-vips_object_n_static_cb( VipsObject *object, int *n )
+vips_object_n_static_cb( VipsObject *object, int *n, void *b )
 {
 	if( object->static_object )
 		*n += 1;
@@ -3132,7 +3132,7 @@ vips_object_n_static( void )
 }
 
 static void *
-vips_object_print_all_cb( VipsObject *object, int *n )
+vips_object_print_all_cb( VipsObject *object, int *n, void *b )
 {
 	VipsObjectClass *class = VIPS_OBJECT_GET_CLASS( object );
 
@@ -3176,7 +3176,7 @@ vips_object_print_all( void )
 }
 
 static void *
-vips_object_sanity_all_cb( VipsObject *object )
+vips_object_sanity_all_cb( VipsObject *object, void *a, void *b )
 {
 	(void) vips_object_sanity( object );
 
diff --git a/libvips/iofuncs/rect.c b/libvips/iofuncs/rect.c
index 8e5dd5acb6..79ae69f764 100644
--- a/libvips/iofuncs/rect.c
+++ b/libvips/iofuncs/rect.c
@@ -225,7 +225,7 @@ vips_rect_unionrect( const VipsRect *r1, const VipsRect *r2, VipsRect *out )
  * vips_rect_dup: (skip)
  * @r: rectangle to duplicate
  *
- * Duplicate a rect to the heap. You need to free the result with vips_free().
+ * Duplicate a rect to the heap. You need to free the result with g_free().
  *
  * Returns: (transfer full): a pointer to copy of @r allocated on the heap.
  */
diff --git a/libvips/iofuncs/region.c b/libvips/iofuncs/region.c
index 50b4dc8381..89d215ab0e 100644
--- a/libvips/iofuncs/region.c
+++ b/libvips/iofuncs/region.c
@@ -1576,7 +1576,7 @@ vips_region_shrink( VipsRegion *from, VipsRegion *to, const VipsRect *target )
 /* Generate into a region. 
  */
 static int
-vips_region_generate( VipsRegion *reg )
+vips_region_generate( VipsRegion *reg, void *a )
 {
 	VipsImage *im = reg->im;
 
@@ -1659,8 +1659,7 @@ vips_region_prepare( VipsRegion *reg, const VipsRect *r )
 
 	switch( im->dtype ) {
 	case VIPS_IMAGE_PARTIAL:
-		if( vips_region_fill( reg, r, 
-			(VipsRegionFillFn) vips_region_generate, NULL ) )
+		if( vips_region_fill( reg, r, vips_region_generate, NULL ) )
 			return( -1 );
 
 		break;
@@ -1716,7 +1715,7 @@ vips_region_prepare_to_generate( VipsRegion *reg,
 
 	/* Run sequence into reg.
 	 */
-	if( vips_region_generate( reg ) )
+	if( vips_region_generate( reg, NULL ) )
 		return( -1 );
 
 	/* The generate function may not have actually made any pixels ... it
@@ -2007,7 +2006,7 @@ vips_region_invalidate( VipsRegion *reg )
 
 #ifdef VIPS_DEBUG
 static void *
-vips_region_dump_all_cb( VipsRegion *region, size_t *alive )
+vips_region_dump_all_cb( VipsRegion *region, size_t *alive, void *b )
 {
 	char str[2048];
 	VipsBuf buf = VIPS_BUF_STATIC( str );
diff --git a/libvips/iofuncs/sink.c b/libvips/iofuncs/sink.c
index d8cad9b343..17454eda36 100644
--- a/libvips/iofuncs/sink.c
+++ b/libvips/iofuncs/sink.c
@@ -120,7 +120,7 @@ static void
 sink_area_free( SinkArea *area )
 {
 	vips_semaphore_destroy( &area->n_thread );
-	vips_free( area );
+	g_free( area );
 }
 
 static SinkArea *
diff --git a/libvips/iofuncs/sinkdisc.c b/libvips/iofuncs/sinkdisc.c
index 33647b6360..8cd62be6b9 100644
--- a/libvips/iofuncs/sinkdisc.c
+++ b/libvips/iofuncs/sinkdisc.c
@@ -157,7 +157,7 @@ wbuffer_free( WriteBuffer *wbuffer )
 	vips_semaphore_destroy( &wbuffer->go );
 	vips_semaphore_destroy( &wbuffer->nwrite );
 	vips_semaphore_destroy( &wbuffer->done );
-	vips_free( wbuffer );
+	g_free( wbuffer );
 }
 
 static void
diff --git a/libvips/iofuncs/sinkmemory.c b/libvips/iofuncs/sinkmemory.c
index bde9ac0981..0441312f89 100644
--- a/libvips/iofuncs/sinkmemory.c
+++ b/libvips/iofuncs/sinkmemory.c
@@ -126,7 +126,7 @@ static void
 sink_memory_area_free( SinkMemoryArea *area )
 {
 	vips_semaphore_destroy( &area->nwrite );
-	vips_free( area );
+	g_free( area );
 }
 
 static SinkMemoryArea *
diff --git a/libvips/iofuncs/sinkscreen.c b/libvips/iofuncs/sinkscreen.c
index e36644a31b..9c216e59d2 100644
--- a/libvips/iofuncs/sinkscreen.c
+++ b/libvips/iofuncs/sinkscreen.c
@@ -206,12 +206,12 @@ render_thread_state_new( VipsImage *im, void *a )
 }
 
 static void *
-tile_free( Tile *tile )
+tile_free( Tile *tile, void *a, void *b )
 {
 	VIPS_DEBUG_MSG_AMBER( "tile_free\n" );
 
 	VIPS_UNREF( tile->region );
-	vips_free( tile );
+	g_free( tile );
 
 	return( NULL );
 }
@@ -245,7 +245,7 @@ render_free( Render *render )
 
 	VIPS_UNREF( render->in ); 
 
-	vips_free( render );
+	g_free( render );
 
 #ifdef VIPS_DEBUG_AMBER
 	render_num_renders -= 1;
@@ -454,7 +454,7 @@ vips__render_shutdown( void )
 }
 
 static int       
-render_dirty_sort( Render *a, Render *b )
+render_dirty_sort( Render *a, Render *b, void *user_data )
 {
 	return( b->priority - a->priority );
 }
@@ -504,7 +504,7 @@ tile_equal( gconstpointer a, gconstpointer b )
 		rect1->top == rect2->top );
 }
 
-static int
+static void
 render_close_cb( VipsImage *image, Render *render )
 {
 	VIPS_DEBUG_MSG_AMBER( "render_close_cb\n" );
@@ -523,8 +523,6 @@ render_close_cb( VipsImage *image, Render *render )
 	 */
 	VIPS_DEBUG_MSG_GREEN( "render_close_cb: reschedule\n" );
 	render_reschedule = TRUE;
-
-	return( 0 );
 }
 
 static Render *
@@ -617,7 +615,7 @@ tile_new( Render *render )
 	tile->ticks = render->ticks;
 
 	if( !(tile->region = vips_region_new( render->in )) ) {
-		(void) tile_free( tile );
+		(void) tile_free( tile, NULL, NULL );
 		return( NULL );
 	}
 
diff --git a/libvips/iofuncs/source.c b/libvips/iofuncs/source.c
index b20c5b580c..a8d59261d6 100644
--- a/libvips/iofuncs/source.c
+++ b/libvips/iofuncs/source.c
@@ -1000,9 +1000,8 @@ vips_source_map( VipsSource *source, size_t *length_out )
 }
 
 static int
-vips_source_map_cb( void *a, void *b )
+vips_source_map_cb( void *a, VipsArea *area )
 {
-	VipsArea *area = VIPS_AREA( b );
 	GObject *gobject = G_OBJECT( area->client );
 
 	VIPS_UNREF( gobject );
@@ -1027,7 +1026,8 @@ vips_source_map_blob( VipsSource *source )
 	VipsBlob *blob;
 
 	if( !(buf = vips_source_map( source, &len )) ||
-		!(blob = vips_blob_new( vips_source_map_cb, buf, len )) ) 
+		!(blob = vips_blob_new( (VipsCallbackFn) vips_source_map_cb, 
+			buf, len )) ) 
 		return( NULL );
 
 	/* The source must stay alive until the blob is done.
diff --git a/libvips/iofuncs/target.c b/libvips/iofuncs/target.c
index 11ca2fc688..1ca378357e 100644
--- a/libvips/iofuncs/target.c
+++ b/libvips/iofuncs/target.c
@@ -413,7 +413,7 @@ vips_target_finish( VipsTarget *target )
 		data = g_byte_array_free( target->memory_buffer, FALSE );
 		target->memory_buffer = NULL;
 		vips_blob_set( target->blob,
-			(VipsCallbackFn) g_free, data, length );
+			(VipsCallbackFn) vips_area_free_cb, data, length );
 	}
 	else
 		class->finish( target );
diff --git a/libvips/iofuncs/type.c b/libvips/iofuncs/type.c
index 120a71dab0..f706655c02 100644
--- a/libvips/iofuncs/type.c
+++ b/libvips/iofuncs/type.c
@@ -171,6 +171,14 @@ vips_area_copy( VipsArea *area )
 	return( area );
 }
 
+int
+vips_area_free_cb( void *mem, VipsArea *area )
+{
+	g_free( mem );
+
+	return( 0 );
+}
+
 void
 vips_area_free( VipsArea *area )
 {
@@ -314,7 +322,7 @@ vips_area_new_array( GType type, size_t sizeof_type, int n )
 	void *array;
 
 	array = g_malloc( n * sizeof_type );
-	area = vips_area_new( (VipsCallbackFn) g_free, array );
+	area = vips_area_new( (VipsCallbackFn) vips_area_free_cb, array );
 	area->n = n;
 	area->length = n * sizeof_type;
 	area->type = type;
@@ -323,7 +331,7 @@ vips_area_new_array( GType type, size_t sizeof_type, int n )
 	return( area );
 }
 
-static void
+static int
 vips_area_free_array_object( GObject **array, VipsArea *area )
 {
 	int i;
@@ -333,6 +341,8 @@ vips_area_free_array_object( GObject **array, VipsArea *area )
 	VIPS_FREE( array ); 
 
 	area->n = 0;
+
+	return( 0 );
 }
 
 /**
@@ -556,7 +566,7 @@ vips_ref_string_new( const char *str )
 	if( !g_utf8_validate( str, -1, NULL ) ) 
 		str = "<invalid utf-8 string>";
 
-	area = vips_area_new( (VipsCallbackFn) g_free, g_strdup( str ) );
+	area = vips_area_new( (VipsCallbackFn) vips_area_free_cb, g_strdup( str ) );
 
 	/* Handy place to cache this.
 	 */
@@ -655,7 +665,7 @@ vips_blob_copy( const void *data, size_t length )
 
 	data_copy = vips_malloc( NULL, length );
 	memcpy( data_copy, data, length );
-	area = vips_area_new( (VipsCallbackFn) g_free, data_copy );
+	area = vips_area_new( (VipsCallbackFn) vips_area_free_cb, data_copy );
 	area->length = length;
 
 	return( (VipsBlob *) area );
@@ -737,7 +747,7 @@ transform_blob_save_string( const GValue *src_value, GValue *dest_value )
 	blob = vips_value_get_blob( src_value, &length );
 	if( (b64 = g_base64_encode( blob, length )) ) {
 		vips_value_set_save_string( dest_value, b64 );
-		vips_free( b64 );
+		g_free( b64 );
 	}
 	else
 		/* No error return from transform, but we should set it to
@@ -756,7 +766,7 @@ transform_save_string_blob( const GValue *src_value, GValue *dest_value )
 	b64 = vips_value_get_save_string( src_value );
 	if( (blob = g_base64_decode( b64, &length )) )
 		vips_value_set_blob( dest_value, 
-			(VipsCallbackFn) vips_free, blob, length );
+			(VipsCallbackFn) vips_area_free_cb, blob, length );
 	else
 		/* No error return from transform, but we should set it to
 		 * something.
@@ -1641,7 +1651,7 @@ vips_value_set_blob_free( GValue *value, void *data, size_t length )
 
 	g_assert( G_VALUE_TYPE( value ) == VIPS_TYPE_BLOB );
 
-	blob = vips_blob_new( (VipsCallbackFn) g_free, data, length );
+	blob = vips_blob_new( (VipsCallbackFn) vips_area_free_cb, data, length );
 	g_value_set_boxed( value, blob );
 	vips_area_unref( VIPS_AREA( blob ) );
 }
diff --git a/libvips/iofuncs/util.c b/libvips/iofuncs/util.c
index f99deb81fb..0629adab79 100644
--- a/libvips/iofuncs/util.c
+++ b/libvips/iofuncs/util.c
@@ -222,10 +222,10 @@ vips_slist_filter( GSList *list, VipsSListMap2Fn fn, void *a, void *b )
 static void
 vips_slist_free_all_cb( void * thing, void * dummy )
 {
-	vips_free( thing );
+	g_free( thing );
 }
 
-/* Free a g_slist of things which need vips_free()ing.
+/* Free a g_slist of things which need g_free()ing.
  */
 void
 vips_slist_free_all( GSList *list )
@@ -815,7 +815,7 @@ vips__file_read( FILE *fp, const char *filename, size_t *length_out )
 		rewind( fp );
 		read = fread( str, sizeof( char ), (size_t) len, fp );
 		if( read != (size_t) len ) {
-			vips_free( str );
+			g_free( str );
 			vips_error( "vips__file_read", 
 				_( "error reading from file \"%s\"" ), 
 				filename );
@@ -944,7 +944,7 @@ vips__gvalue_copy( GValue *value )
 }
 
 static void
-vips__gvalue_free( GValue *value )
+vips__gvalue_free( GValue *value, void *user_data )
 {
 	g_value_unset( value );
 	g_free( value );
@@ -2031,7 +2031,7 @@ vips__icc_dir( void )
 	static GOnce once = G_ONCE_INIT;
 
 	return( (const char *) g_once( &once, 
-		(GThreadFunc) vips_icc_dir_once, NULL ) );
+		vips_icc_dir_once, NULL ) );
 }
 
 #ifdef OS_WIN32
@@ -2069,7 +2069,7 @@ vips__windows_prefix( void )
 	static GOnce once = G_ONCE_INIT;
 
 	return( (const char *) g_once( &once, 
-		(GThreadFunc) vips__windows_prefix_once, NULL ) );
+		vips__windows_prefix_once, NULL ) );
 }
 
 char *
diff --git a/libvips/iofuncs/vips.c b/libvips/iofuncs/vips.c
index 16e7475971..a1b61ab8aa 100644
--- a/libvips/iofuncs/vips.c
+++ b/libvips/iofuncs/vips.c
@@ -490,7 +490,7 @@ read_chunk( int fd, gint64 offset, size_t length )
 	if( !(buf = vips_malloc( NULL, length + 1 )) )
 		return( NULL );
 	if( read( fd, buf, length ) != (ssize_t) length ) {
-		vips_free( buf );
+		g_free( buf );
 		vips_error( "VipsImage", "%s", _( "unable to read history" ) );
 		return( NULL );
 	}
@@ -828,7 +828,7 @@ target_write_quotes( VipsTarget *target, const char *str )
 }
 
 static void *
-build_xml_meta( VipsMeta *meta, VipsTarget *target )
+build_xml_meta( VipsMeta *meta, VipsTarget *target, void *b )
 {
 	GType type = G_VALUE_TYPE( &meta->value );
 
diff --git a/libvips/iofuncs/window.c b/libvips/iofuncs/window.c
index 8b98683d2f..875c895ef2 100644
--- a/libvips/iofuncs/window.c
+++ b/libvips/iofuncs/window.c
@@ -129,7 +129,7 @@ vips_window_free( VipsWindow *window )
 
 	window->im = NULL;
 
-	vips_free( window );
+	g_free( window );
 
 	return( 0 );
 }
@@ -307,7 +307,7 @@ typedef struct {
 } request_t;
 
 static void *
-vips_window_fits( VipsWindow *window, request_t *req )
+vips_window_fits( VipsWindow *window, request_t *req, void *b )
 {
 	if( window->top <= req->top && 
 		window->top + window->height >= req->top + req->height )