vips/image: use g_object_unref instead of g_clear_object (as noted by…

… libvips documentation) (#219), add test case for checking return errors of a known corrupted JPEG (#374)

Co-authored-by: Gerdriaan Mulder <[email protected]>

vips/image.c

@@ -3,6 +3,7 @@
 int has_alpha_channel(VipsImage *image) { return vips_image_hasalpha(image); }
 
 void clear_image(VipsImage **image) {
-  // https://developer.gnome.org/gobject/stable/gobject-The-Base-Object-Type.html#g-clear-object
-  if (G_IS_OBJECT(*image)) g_clear_object(image);
+  // Reference-counting in libvips: https://www.libvips.org/API/current/using-from-c.html#using-C-ref
+  // https://docs.gtk.org/gobject/method.Object.unref.html
+  if (G_IS_OBJECT(*image)) g_object_unref(*image);
 }

vips/image_test.go

@@ -1026,6 +1026,20 @@ func TestImageRef_JP2K(t *testing.T) {
 	assert.Equal(t, 1, metadata.Pages)
 }
 
+func TestImageRef_CorruptedJPEG(t *testing.T) {
+	Startup(nil)
+
+	raw, err := ioutil.ReadFile(resources + "jpg-corruption.jpg")
+	require.NoError(t, err)
+
+	img, err := NewImageFromBuffer(raw)
+	require.NoError(t, err)
+	require.NotNil(t, img)
+
+	_, _, err = img.ExportJpeg(nil)
+	assert.Error(t, err, "VipsJpeg: Corrupt JPEG data: bad Huffman code")
+}
+
 // TODO unit tests to cover:
 // NewImageFromReader failing test
 // NewImageFromFile failing test