Re: Possible Memory Leak with stream-for-each

[Tristan Colgate <tcolgate@gmail.com>]

FWIW, the code in srfi-41 now works out of the box (thanks to some
recent r6rs library fixes), with the exception of all the negative
unit tests, due to some exception handling issue I didn't really look
at. I don't know if it still shows the memory leak though.

On 20 July 2010 21:36, Andy Wingo <wingo@pobox.com> wrote:
> On Mon 19 Jul 2010 20:08, Abhijeet More <abhijeet.more@gmail.com> writes:
>
>> 1. Can it be confirmed that this is a leak in guile's garbage
>> collection?
>
> Hi,
>
> I can confirm this for Guile 1.9/2.0 at least. Gross... The code that I
> used was, to first generate a test file:
>
>  (with-output-to-file "/tmp/test"
>    (lambda ()
>      (let lp ((n 0))
>        (if (< n 10000000)
>            (begin
>              (write '(foo))
>              (lp (1+ n)))))))
>
> Then execute the following code:
>
>  (define stream-null? null?)
>  (define the-empty-stream '())
>  (define (stream-car stream) (car stream))
>  (define (stream-cdr stream) (force (cdr stream)))
>  (define-syntax cons-stream
>    (syntax-rules ()
>      ((_ ?car ?cdr) (cons ?car (delay ?cdr)))))
>
>  (define (stream-for-each proc s)
>    (if (not (stream-null? s))
>        (begin (proc (stream-car s))
>               (stream-for-each proc (stream-cdr s)))))
>
>  (define (port->stream port readproc)
>    (cons-stream (readproc port) (port->stream port readproc)))
>
>  (stream-for-each
>   identity
>   (port->stream (open-input-file "/tmp/test") read))
>
> And I see memory usage explode, yes, at the REPL, even if I disable
> position recording via (read-disable 'positions).
>
>> 2. Are there any workarounds (for instance doing an explicit "(gc)"
>> somewhere in the definitions?
>> 3. Any pointers on fixing the underlying issue?
>
> I don't know. Ludovic? :) You have certainly found a bug, though. We
> probably won't look into it for 1.8, but we will certainly try to fix it
> for 2.0 (soon!).
>
>> 4. I noticed that streams in guile (ice-9 streams) were not
>> implemented in the SICP way. In-fact they were implemented in a way
>> that makes recursive definitions impossible. Was this intentional?
>
> I don't know TBH. SICP streams do have a problem, amply explored in
> http://www.cs.rice.edu/~taha/publications/conference/sml98.pdf; but
> beyond that, I don't know.
>
> Perturbedly yours,
>
> Andy
> --
> http://wingolog.org/
>
>



-- 
Tristan Colgate-McFarlane
----
  "You can get all your daily vitamins from 52 pints of guiness, and a
glass of milk"