On Wed, 2008-07-02 at 02:07 -0400, Brandon S. Allbery KF8NH wrote: > > On 2008 Jul 2, at 1:42, Galchin, Vasili wrote: > > > errno <- throwErrnoIfMinus1 "aioError" (c_aio_error p_aiocb) > > > > "ghc" thinks that "Errno" should be an instance of "Num": > > > > System/Posix/Aio.hsc:117:15: > > No instance for (Num Errno) > > > I expect so it can compare it to -1(throwErrnoIfMinusOne). But if the > return value is actually an errno and not -1 to indicate error (which > it is if I read the manpage correctly), you don't want > throwErrnoIfMinus1 anyway; I suspect you want to wrap the return value > of c_aio_return (which should be IO CInt) in an Errno constructor, > then use errnoToIOError if you really want to raise an IOError. > > > (What were you expecting for "count"? I see none, just an errno.) > > > Note that it *never* returns -1; it returns 0 for successful > completion for the aiocb, EINPROGRESS if it's still working, and the > appropriate errno if it failed.
It seems as though it can return -1 if given non-sensical input. But in that case, the nicely type-correct thing to do would still be to have the C binding return a CInt, and wrap that after the call to throwErrnoIfMinus1 (in this case, `errno' still refers to the global errno, set to EINVAL). jcc _______________________________________________ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
