[ruby-core:121618] [Ruby Bug#21260] duping stringio objects shares cursors
From:
"chucke (Tiago Cardoso) via ruby-core" <ruby-core@...>
Date:
2025-04-10 08:25:51 UTC
List:
ruby-core #121618
Issue #21260 has been updated by chucke (Tiago Cardoso).
I see. Alignment with File makes sense. At least my expectation was that, by dup'ing the IO object, I'd receive a separate independent object with which to traverse the file. But perhaps that does not make sense, as at least in the case of File, that'd mean a second OS file descriptor, and that's heavy? Also not sure whether this expectation is general.
----------------------------------------
Bug #21260: duping stringio objects shares cursors
https://bugs.ruby-lang.org/issues/21260#change-112672
* Author: chucke (Tiago Cardoso)
* Status: Feedback
* ruby -v: ruby 3.4.2 (2025-02-15 revision d2930f8e7a) +PRISM [x86_64-darwin23]
* Backport: 3.2: UNKNOWN, 3.3: UNKNOWN, 3.4: UNKNOWN
----------------------------------------
I've found that, if I `.dup` a stringio, when I read one of the objects, the cursor also moves internally on the other:
```ruby
require "stringio"
s1 = StringIO.new("test")
s2 = s1.dup
s1.read #=> "test"
s2.read #=> ""
s1.rewind
s2.rewind
s2.read #=> "test"
s1.read #=> ""
s1.pos #=> 4
s2.pos #=> 4
```
--
https://bugs.ruby-lang.org/
______________________________________________
ruby-core mailing list -- ruby-core@ml.ruby-lang.org
To unsubscribe send an email to ruby-core-leave@ml.ruby-lang.org
ruby-core info -- https://ml.ruby-lang.org/mailman3/lists/ruby-core.ml.ruby-lang.org/