hWaitForInput cannot be interrupted by async exceptions on unix

http://hackage.haskell.org/package/base-4.6.0.1/docs/System-Timeout.html

claims that timeout can interrupt hWaitForInput, but in fact that's false (e.g. mentioned in #7353 (closed)#ticket:8684#comment:78734).

-- import Control.Concurrent
import System.IO
import System.Timeout

main = timeout (1 * 1000000) $ hWaitForInput stdin (5 * 1000)

will not be killed after 1 second, but instead wait for the full 5 seconds timeout passed to hWaitForInput.

The implementation is ready at https://downloads.haskell.org/~ghc/7.6.3/docs/html/libraries/base/src/GHC-IO-FD.html, where we have two foreign calls: safe fdReady and unsafe unsafe_fdReady.

The actual C implementation is at https://github.com/ghc/packages-base/blob/52c0b09036c36f1ed928663abb2f295fd36a88bb/cbits/inputReady.c#L16. It uses select on Unix, and does check for EINTR, so I believe that according to http://www.haskell.org/ghc/docs/7.6.3/html/users_guide/ffi.html#ffi-interruptible both foreign calls can be replaced by a single interruptible one.

Is that true?

If not, it's a documentation bug in timeout at least.

Also, does interruptible, apart from allowing the function to be interrupted, behave more like safe or unsafe?