Bug #1909: Strange behavior IO#ungetc at the beginning of the stream

• Status: Rejected
• Assignee: -
• Target version: -
• ruby -v: ruby 1.8.6 (2008-08-11 patchlevel 287) [i386-mswin32]

[tmat (Tomas Matousek)]

=begin
This works:
io = File.open("a.txt", "r+")
io.read(0)
p io.pos # => 0
io.ungetc(100)
p io.pos # => 0

while this doesn't:
io = File.open("a.txt", "r+")
p io.pos # => 0
io.ungetc(100) # => unread stream (IOError)

I would expect the first case to raise the same error as the second one since ungetc is supposed to shift the position back by 1 and we are at the beginning of the stream.

In ruby 1.9.1p129 (2009-05-12 revision 23412) [i386-mswin32] neither case raises an exception, which is at least consistent but still weird.
=end

[mame (Yusuke Endoh)]

• Status changed from Open to Rejected

=begin
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 [e-mail]
=end