Re: [racket-dev] foreign struct access different in 5.1.3?

2011-09-17 Thread Matthew Flatt 
At Sat, 17 Sep 2011 07:44:50 -0600, Kevin Tew wrote:
 If you would like document the fact that cstructs are generative only up 
 to version 5.1.3.  I think that improve the docs.

I think the right next step is for you (Kevin) to update
doc/release-notes/racket/HISTORY.txt to describe the change.

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Re: [racket-dev] foreign struct access different in 5.1.3?

2011-09-17 Thread Kevin Tew 

I'll do that.

Kevin
On 09/17/2011 07:53 AM, Matthew Flatt wrote:

At Sat, 17 Sep 2011 07:44:50 -0600, Kevin Tew wrote:

If you would like document the fact that cstructs are generative only up
to version 5.1.3.  I think that improve the docs.

I think the right next step is for you (Kevin) to update
doc/release-notes/racket/HISTORY.txt to describe the change.



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[racket-dev] foreign struct access different in 5.1.3?

2011-09-16 Thread John Clements 
I'm trying to backport working FFI code to 5.1.3, and I'm having trouble 
referring to elements of a C struct. Specifically, in the presence of this 
definition

(define-cstruct _rack-audio-closure
  ([sound _pointer]
   [cur-sample_ulong]
   [num-samples   _ulong]
   [stop-now  _bool]
   [stop-sema-ptr _pointer]))

using the function (rack-audio-closure-cur-sample) on the result of an FFI call 
with signature

(_fun _pointer _ulong _pointer - _rack-audio-closure-pointer)

produces this error:

rack-audio-closure-cur-sample: expected argument of type 
struct:rack-audio-closure; given #cpointer:rack-audio-closure

in 5.1.3, but it works just fine in the git head.

Git log suggests to me that you (Kevin) might have changed/fixed this in 
a810b30b872787a1365c, so here's the question: is there some workaround to 
access the elements of a C struct in 5.1.3?

Many thanks,

John



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Re: [racket-dev] foreign struct access different in 5.1.3?

2011-09-16 Thread John Clements 

On Sep 16, 2011, at 3:06 PM, John Clements wrote:

 I'm trying to backport working FFI code to 5.1.3, and I'm having trouble 
 referring to elements of a C struct. Specifically, in the presence of this 
 definition
 
 (define-cstruct _rack-audio-closure
  ([sound _pointer]
   [cur-sample_ulong]
   [num-samples   _ulong]
   [stop-now  _bool]
   [stop-sema-ptr _pointer]))
 
 using the function (rack-audio-closure-cur-sample) on the result of an FFI 
 call with signature
 
 (_fun _pointer _ulong _pointer - _rack-audio-closure-pointer)
 
 produces this error:
 
 rack-audio-closure-cur-sample: expected argument of type 
 struct:rack-audio-closure; given #cpointer:rack-audio-closure
 
 in 5.1.3, but it works just fine in the git head.

More research suggests that the problem is more limited; it looks like a 
problem of generativity. That is, if I have two modules that declare the same 
cstruct (same name, same fields, same types) then cpointers to these structures 
returned by functions from the first module cannot be accessed in the other 
module.

AFAICT, This is not the case in more recent versions; that is, these cstructs 
are not generative.  Assuming this is deliberate, I could document it.

John



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