System.Posix.User.getGroupEntryForName incorrect error for non-existent group

[Eelis]

The following program:

  import System.Posix.User
  main :: IO ()
  main = getGroupEntryForName "monkeys" >> return ()

gives the following output (on a system without a "monkeys" group):

  *** Exception: getGroupEntryForName: failed (Success)

The "(Success)" part is obviously wrong.

The problem is that the getGroupEntryForName implementation throws errno if getgrnam_r wrote NULL to the pointer pointed to by its last parameter, while the  getgrnam_r specification makes no guarantees about errno being set in that case.

[igloo]

The problem is when an error doesn't occur, but the name requested can't be found. The throwErrorIfNonZero_ doesn't happen, because 0 is returned, but the throwErrnoIfNull throws errno. We should throw something else in this situation.

[igloo]

Fixed and merged:

Sat Nov 10 15:58:05 PST 2007  Ian Lynagh <igloo@earth.li>
  * Throw a proper exception if getGroupEntryForName fails to find an entry
  We used to get
   *** Exception: getGroupEntryForName: failed (Success)
  Fixes trac #1655