raise Vips::Error if copy_memory fails (#443)

vips_image_copy_memory() returns NULL on error, for example when the
source cannot be decoded. copy_memory wrapped that pointer without a
check, so the next call on the returned image segfaulted.

Fixes #442

Author: VitaliiLazebnyi

CHANGELOG.md

@@ -2,6 +2,8 @@
 
 ## master
 
+* raise Vips::Error if `copy_memory` fails [VitaliiLazebnyi]
+
 ## Version 2.3.0 (2025-12-10)
 
 * move library_name out of the global namespace and into FFI [jcupitt]

lib/vips/image.rb

@@ -1018,6 +1018,8 @@ def add_alpha
     # @return [Image] new memory image
     def copy_memory
       new_image = Vips.vips_image_copy_memory self
+      raise Vips::Error if new_image.null?
+
       Vips::Image.new new_image
     end
 

spec/image_spec.rb

@@ -81,6 +81,19 @@
     expect { img.write_to_memory }.to raise_exception(Vips::Error)
   end
 
+  it "can copy an image to memory" do
+    image = (Vips::Image.black(16, 16) + 128).copy_memory
+
+    expect(image.width).to eq(16)
+    expect(image.height).to eq(16)
+    expect(image.avg).to eq(128)
+  end
+
+  it "will raise VipsError if copy_memory fails" do
+    img = Vips::Image.new_from_file simg("coffee.gif")
+    expect { img.copy_memory }.to raise_exception(Vips::Error)
+  end
+
   it "throws an error when trying to load an image from memory with unknown size" do
     data = FFI::Pointer.new(1)
     expect { Vips::Image.new_from_memory(data, 16, 16, 1, :uchar) }.to raise_error(Vips::Error)