adding comment to deprecated method

As Nicholas Smith mentioned in the comments. The solution is:

__attribute((deprecated("use x method")))

if you want you can also use the less convoluted:

__deprecated_msg("use x method")

I would tend to use this:

__deprecated_msg("use method x instead")

rather than:

__attribute((deprecated("use method x instead")))

They're really the same under the hood, but first one is a bit more clear.