* bug#17466: unexpected bytevector contents with get-bytevector-n
@ 2014-05-11 11:00 J Kalbhenn
2014-05-28 15:26 ` Ludovic Courtès
0 siblings, 1 reply; 3+ messages in thread
From: J Kalbhenn @ 2014-05-11 11:00 UTC (permalink / raw)
To: 17466
concerning the following code example
--
(import (rnrs io ports) (ice-9 pretty-print))
(define (problem-part port) (pretty-print (get-bytevector-n port 4096)))
(let loop ((count 100))
(if (> count 0)
(begin (call-with-input-string "22222222222222222222" problem-part)
(loop (- count 1)))))
__
when i run it i get output with portions like this
--
#vu8(50 50 50 50 50 50 50 50 50 50 50 50 50 50 50 50 50 50 50 50)
#vu8(0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0)
#vu8(50 50 50 50 50 50 50 50 50 50 50 50 50 50 50 50 50 50 50 50)
#vu8(50 50 50 50 50 50 50 50 50 50 50 50 50 50 50 50 50 50 50 50)
#vu8(50 50 50 50 50 50 50 50 50 50 50 50 50 50 50 50 50 50 50 50)
#vu8(50 50 50 50 50 50 50 50 50 50 50 50 50 50 50 50 50 50 50 50)
#vu8(50 50 50 50 50 50 50 50 50 50 50 50 50 50 50 50 50 50 50 50)
#vu8(50 50 50 50 50 50 50 50 50 50 50 50 50 50 50 50 50 50 50 50)
#vu8(0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0)
#vu8(50 50 50 50 50 50 50 50 50 50 50 50 50 50 50 50 50 50 50 50)
#vu8(50 50 50 50 50 50 50 50 50 50 50 50 50 50 50 50 50 50 50 50)
#vu8(50 50 50 50 50 50 50 50 50 50 50 50 50 50 50 50 50 50 50 50)
#vu8(50 50 50 50 50 50 50 50 50 50 50 50 50 50 50 50 50 50 50 50)
#vu8(50 50 50 50 50 50 50 50 50 50 50 50 50 50 50 50 50 50 50 50)
#vu8(50 50 50 50 50 50 50 50 16 224 240 0 0 0 0 0 50 50 50 50)
#vu8(50 50 50 50 50 50 50 50 50 50 50 50 50 50 50 50 50 50 50 50)
--
and i would expect the bytevector to always be the same.
this first occurred to me in a more complicated scenario where:
- the input port is a file-port
- pretty-print was used at first and then display instead, but the
problem persisted with a much lower frequency
system info
guile 2.0.11
linux 3.14.2-1-ARCH x86_64
^ permalink raw reply [flat|nested] 3+ messages in thread* bug#17466: unexpected bytevector contents with get-bytevector-n
2014-05-11 11:00 bug#17466: unexpected bytevector contents with get-bytevector-n J Kalbhenn
@ 2014-05-28 15:26 ` Ludovic Courtès
2014-05-28 17:32 ` Ludovic Courtès
0 siblings, 1 reply; 3+ messages in thread
From: Ludovic Courtès @ 2014-05-28 15:26 UTC (permalink / raw)
To: J Kalbhenn; +Cc: 17466
Hello,
J Kalbhenn <jkal@posteo.eu> skribis:
> (import (rnrs io ports) (ice-9 pretty-print))
> (define (problem-part port) (pretty-print (get-bytevector-n port 4096)))
>
> (let loop ((count 100))
> (if (> count 0)
> (begin (call-with-input-string "22222222222222222222" problem-part)
> (loop (- count 1)))))
> __
>
> when i run it i get output with portions like this
> --
> #vu8(50 50 50 50 50 50 50 50 50 50 50 50 50 50 50 50 50 50 50 50)
> #vu8(0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0)
> #vu8(50 50 50 50 50 50 50 50 50 50 50 50 50 50 50 50 50 50 50 50)
> #vu8(50 50 50 50 50 50 50 50 50 50 50 50 50 50 50 50 50 50 50 50)
> #vu8(50 50 50 50 50 50 50 50 50 50 50 50 50 50 50 50 50 50 50 50)
> #vu8(50 50 50 50 50 50 50 50 50 50 50 50 50 50 50 50 50 50 50 50)
> #vu8(50 50 50 50 50 50 50 50 50 50 50 50 50 50 50 50 50 50 50 50)
> #vu8(50 50 50 50 50 50 50 50 50 50 50 50 50 50 50 50 50 50 50 50)
> #vu8(0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0)
> #vu8(50 50 50 50 50 50 50 50 50 50 50 50 50 50 50 50 50 50 50 50)
> #vu8(50 50 50 50 50 50 50 50 50 50 50 50 50 50 50 50 50 50 50 50)
> #vu8(50 50 50 50 50 50 50 50 50 50 50 50 50 50 50 50 50 50 50 50)
> #vu8(50 50 50 50 50 50 50 50 50 50 50 50 50 50 50 50 50 50 50 50)
> #vu8(50 50 50 50 50 50 50 50 50 50 50 50 50 50 50 50 50 50 50 50)
> #vu8(50 50 50 50 50 50 50 50 16 224 240 0 0 0 0 0 50 50 50 50)
> #vu8(50 50 50 50 50 50 50 50 50 50 50 50 50 50 50 50 50 50 50 50)
> --
>
> and i would expect the bytevector to always be the same.
Indeed. I’ve been experiencing that in a more complex scenario too:
<http://bugs.gnu.org/17591>.
The guts of the problem seems to be GC_REALLOC. I’m debugging it now
and your reduced test case will be helpful.
Ludo’.
^ permalink raw reply [flat|nested] 3+ messages in thread
* bug#17466: unexpected bytevector contents with get-bytevector-n
2014-05-28 15:26 ` Ludovic Courtès
@ 2014-05-28 17:32 ` Ludovic Courtès
0 siblings, 0 replies; 3+ messages in thread
From: Ludovic Courtès @ 2014-05-28 17:32 UTC (permalink / raw)
To: J Kalbhenn; +Cc: 17466-done
This is fixed by commit 1baa215, which will be in Guile 2.0.12.
It turns out that when shrinking a bytevector, as happens before
‘get-bytevector-n’ returns, the pointer to the bytevector’s contents
would not be left pointing to the old bytevector. When that old
bytevector was eventually reclaimed, anything could happen.
Thanks!
Ludo’.
^ permalink raw reply [flat|nested] 3+ messages in thread
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2014-05-11 11:00 bug#17466: unexpected bytevector contents with get-bytevector-n J Kalbhenn
2014-05-28 15:26 ` Ludovic Courtès
2014-05-28 17:32 ` Ludovic Courtès
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