Issue #1909 has been updated by Yusuke Endoh.

Status changed from Open to Rejected

Hi,

The 1.8 behavior depends on stdio.

In 1.9, pushing back behind the beginning should be considered
as implementation-defined.  Not a bug.

-- 
Yusuke Endoh <mame / tsg.ne.jp>
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http://redmine.ruby-lang.org/issues/show/1909

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