On Mon, 23 Mar 2009, Risto Saarelma wrote:
> I'm trying to read the exit status of a process run with MLton.Process. I use
> this code:
>
>
> open MLton.Process
>
> val () =
> let
> val proc = MLton.Process.create {
> args = [],
> env = NONE,
> path = "/usr/bin/ls",
> stderr = Param.pipe,
> stdin = Param.null,
> stdout = Param.pipe}
> val exitStatus = reap proc
>
> in
> case exitStatus of
> Posix.Process.W_EXITSTATUS st => print "Error code.\n"
> | _ => print "Something else.\n"
> end
>
>
> Using MLton 20070826, I get the following error:
>
> $ mlton proctest.sml
> Error: proctest.sml 15.9.
> Case object and rules disagree.
> object type: [?.PosixProcess.exit_status]
> rules expect: [Unix.exit_status]
> in: case exitStatus of (Posix.Process ... "Something else.\n")
> compilation aborted: parseAndElaborate reported errors
>
> MLton.Process.reap is supposed to return a value of type
> Posix.Process.exit_status, and the actual Posix.Process.exit_status is
> apparently just an alias for Unix.exit_status. So why am I getting the type
> error?
There was a missing type constraint in the implementation of the Basis
Library. If you would like to fix a local install, apply the patch from:
http://mlton.org/cgi-bin/viewsvn.cgi?view=rev&rev=7029
to
/usr/local/lib/mlton/sml/basis/libs/basis-extra/top-level/basis.sig
-Matthew