keep magicksave delay array alive for longer

fixes a segv in magicksave_buffer ... we could try to use delay after im
had been unreffed in some circumstances

libvips/foreign/magicksave.c

@@ -72,6 +72,7 @@ typedef struct _VipsForeignSaveMagick {
 	Image *current_image;
 
 	int page_height;
+	GValue delay_gvalue;
 	int *delays;
 	int delays_length;
 
@@ -99,6 +100,7 @@ vips_foreign_save_magick_dispose( GObject *gobject )
 	VIPS_FREEF( DestroyImageList, magick->images );
 	VIPS_FREEF( DestroyImageInfo, magick->image_info );
 	VIPS_FREEF( magick_destroy_exception, magick->exception );
+	g_value_unset( &magick->delay_gvalue );
 
 	G_OBJECT_CLASS( vips_foreign_save_magick_parent_class )->
 		dispose( gobject );
@@ -349,10 +351,15 @@ vips_foreign_save_magick_build( VipsObject *object )
 
 	magick->page_height = vips_image_get_page_height( im );
 
-	if( vips_image_get_typeof( im, "delay" ) &&
-		vips_image_get_array_int( im,
-			"delay", &magick->delays, &magick->delays_length ) ) 
+	/* Get as a gvalue so we can keep a ref to the delay array while we
+	 * need it.
+	 */
+	if( vips_image_get_typeof( im, "delay" ) ) {
+		if( vips_image_get( im, "delay", &magick->delay_gvalue ) ) 
 			return( -1 );
+		magick->delays = vips_value_get_array_int( 
+			&magick->delay_gvalue, &magick->delays_length );
+	}
 
 	if( vips_sink_disc( im, 
 		vips_foreign_save_magick_write_block, magick ) ) 

test/test-suite/test_foreign.py

@@ -459,6 +459,15 @@ class TestForeign:
         self.save_load_buffer("magicksave_buffer", "magickload_buffer",
                               self.colour, 40, format="JPG")
 
+        # try an animation
+        if have("gifload"):
+            x1 = pyvips.Image.new_from_file(GIF_ANIM_FILE, n=-1)
+            w1 = x1.magicksave_buffer(format="GIF")
+            x2 = pyvips.Image.new_from_buffer(w1, "", n=-1)
+            assert x1.get("delay") == x2.get("delay")
+            assert x1.get("page-height") == x2.get("page-height")
+            assert x1.get("gif-loop") == x2.get("gif-loop")
+
     @skip_if_no("webpload")
     def test_webp(self):
         def webp_valid(im):
@@ -517,7 +526,7 @@ class TestForeign:
             x2 = pyvips.Image.new_from_buffer(w1, "", n=-1)
             assert x1.width == x2.width
             assert x1.height == x2.height
-            assert x1.get("gif-delay") == x2.get("gif-delay")
+            assert x1.get("delay") == x2.get("delay")
             assert x1.get("page-height") == x2.get("page-height")
             assert x1.get("gif-loop") == x2.get("gif-loop")
 
@@ -636,6 +645,8 @@ class TestForeign:
 
             x2 = pyvips.Image.new_from_file(GIF_ANIM_FILE, n=-1)
             assert x2.height == 5 * x1.height
+            # our test gif has delay 0 for the first frame set in error
+            assert x2.get("delay") == [0, 50, 50, 50, 50]
 
             x2 = pyvips.Image.new_from_file(GIF_ANIM_FILE, page=1, n=-1)
             assert x2.height == 4 * x1.height