CURLMOPT_SOCKETDATA(3) on macOS
The text e112addce67c, as macOS 26.5, macOS 26.4, macOS 26.3, macOS 26.2, macOS 26.1, macOS 26.0, macOS 15.6, macOS 15.5, macOS 15.4, macOS 15.3, macOS 15.2, macOS 15.1, macOS 15.0, macOS 14.6, macOS 14.5 shipped it. The page shows this text now.
custom pointer passed to the socket callback