CURLOPT_XFERINFODATA(3) on macOS
The text d5ea91598067, as macOS 11.5, macOS 11.4, macOS 11.3, macOS 11.2, macOS 11.1, macOS 11.0.1, macOS 10.15.6, macOS 10.15.5, macOS 10.15.4, macOS 10.15.3, macOS 10.15.2, macOS 10.15.1, macOS 10.15 shipped it.
custom pointer passed to the progress callback