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Re: [libvirt] PATCH: 0/28: Thread safety for libvirtd daemon and drivers



On Wed, Dec 03, 2008 at 11:57:54PM +0000, Daniel P. Berrange wrote:
> let isLockableThingNull exp funcheck =
>    match exp with
>      | UnOp (op,exp,typ) -> (
>          match op with
>            LNot -> (
>              match exp with
>                Lval (lhost, off) -> (
>                   match lhost with
>                     Var vi ->
>                       funcheck vi
>                     | _ -> false
>                  )
>                | _ -> false
>             )
>           | _ -> false
>          )
>       | _ ->
>           false

I guess this is better written using a nested pattern, something like:

let isLockableThingNull exp funcheck =
  match exp with
  | UnOp (LNot, Lval (Var vi, off), typ) when funcheck vi -> true
  | _ -> false

> let isLockableObjectNull exp =
>    isLockableThingNull exp isLockableObjectVar
>
> let isLockableDriverNull exp =
>    isLockableThingNull exp isLockableDriverVar

It doesn't really matter, but you can also hide subfunctions (and
static variables) like this:

  let isLockableObjectNull, isLockableDriverNull =
    let isLockableThingNull exp funcheck =  (* this function is hidden *)
      (* the definition above *)
    in
    let isLockableObjectNull exp =          (* visible *)
      (* copy definition from above *)
    in
    let isLockableDriverNull exp =          (* visible *)
      (* copy definition from above *)
    in
    isLockableObjectNull, isLockableDriverNull

> module L = DF.ForwardsDataFlow(Locking)

CIL is kinda crazy isn't it :-(

>       let prefixes = [ "qem"; "uml"; "lxc"; "ope"; "tes"; "net"; "sto"; "nod" ] in
>       if String.length name > 4 then
>           let prefix = String.sub fundec.svar.vname 0 3 in

There's also a function String.starts_with.  It's in extlib, so you
need to compile with '-package extlib' and add 'open ExtString' at the
top of the source file.

Top marks for dealing with the sheer weirdness of CIL :-)

Rich.

-- 
Richard Jones, Emerging Technologies, Red Hat  http://et.redhat.com/~rjones
Read my OCaml programming blog: http://camltastic.blogspot.com/
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http://cocan.org/getting_started_with_ocaml_on_red_hat_and_fedora


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