Re: nlffi memory problems on power ppc

Hi Brian,

I tried to experiment a bit with this code, and it is quite  
frustrating... :-(

Indeed, I can reproduce your problem on my G5 using the code you posted.
However, adding a bit of instrumentation seems to make the problem
go away.  In particular, I added a routine for printing the contents
of a C array. Putting an invocation of this routine any place where it
makes sense makes the problem completely vanish.

In other words, this looks more and more like a "Heisenbug".  Right
now I don't have a good guess at what's causing this.  I'll keep
looking.

Matthias


On Mar 8, 2007, at 12:10 AM, brian wrote:

> OK.  I have a reasonably coherent example and a specific set of
> failure conditions, so perhaps someone can tell me what's wrong.
>
> I should preface this with some info:
>
> Mac Power PC G5
> Standard ML of New Jersey v110.60 [built: Thu Nov  9 15:44:30 2006]
>
> Here's the test code:
>
> fun memtest() =
>      let fun set(p, i, x) = C.Set.double (C.Ptr.|*| (C.Ptr.|+| (p,
> i)), x)
>          fun fromArray(values) =
>              let val n = Array.length(values)
>                  val m = C.alloc C.T.double (Word.fromInt n)
>                  val _ = Array.appi (fn (i, x) => set(m, i, x)) values
>              in
>                  (* return a read-write version of the pointer *)
>                  C.Ptr.rw m
>              end
>          val a1 = Array.fromList([0.0, 1.0, 2.0, 3.0, 4.0, 5.0, 6.0])
>          val a2 = Array.fromList([0.0, 1.0, 2.0, 3.0, 4.0, 5.0, 6.0])
>          val b1 = fromArray(a1)
>          (* val b2 = fromArray(a2) *)
>      in
>          C.free b1;
>          (* C.free b2; *)
>          ()
>      end
>
> The test code as is WORKS.
> If the "val b2 = ..." line is uncommented, then the test code gives
> me a bus error.
> If the "C.free b2" line is uncommented, then the code gives me a
> segmentation fault.
>
> Thanks
>
> Brian
>
>
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