--- Begin Message ---
Subject: |
unexpected bytevector contents with get-bytevector-n |
Date: |
Sun, 11 May 2014 13:00:23 +0200 |
User-agent: |
Mozilla/5.0 (X11; Linux x86_64; rv:24.0) Gecko/20100101 Thunderbird/24.5.0 |
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
--- End Message ---
--- Begin Message ---
Subject: |
Re: bug#17466: unexpected bytevector contents with get-bytevector-n |
Date: |
Wed, 28 May 2014 19:32:22 +0200 |
User-agent: |
Gnus/5.130009 (Ma Gnus v0.9) Emacs/24.3 (gnu/linux) |
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’.
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