io.c: not shorten buffer unless succeeded

* io.c (io_setstrbuf, io_read): should not shorten the given buffer until
  read succeeds.  [ruby-core:55951] [Bug #8625]

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@46360 b2dd03c8-39d4-4d8f-98ff-823fe69b080e

1 files changed, 8 insertions, 0 deletions

diff --git a/test/ruby/test_io.rb b/test/ruby/test_io.rb
index dca78603c7..fab142a5ee 100644
--- a/test/ruby/test_io.rb
+++ b/test/ruby/test_io.rb
@@ -1230,6 +1230,14 @@ class TestIO < Test::Unit::TestCase
       t.value
       assert_equal("", s)
     end
+    with_pipe do |r, w|
+      s = "xxx"
+      t = Thread.new {r.read(2, s)}
+      Thread.pass until t.stop?
+      t.kill
+      t.value
+      assert_equal("xxx", s)
+    end
   end
 
   def test_write_nonblock