io.c: io_set_read_length

* io.c (io_set_read_length): if the read length equals to the buffer
  string size then nothing to do.  or ensure the string modifiable
  before setting the length only when the former is shorter.  based on
  the patch in [ruby-core:47541] by Hiroshi Shirosaki.
  [ruby-core:46586] [Bug #6764]

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@36980 b2dd03c8-39d4-4d8f-98ff-823fe69b080e

1 files changed, 49 insertions, 0 deletions

diff --git a/test/ruby/test_io.rb b/test/ruby/test_io.rb
index f165c640b1..e266f115ba 100644
--- a/test/ruby/test_io.rb
+++ b/test/ruby/test_io.rb
@@ -2446,5 +2446,54 @@ End
       assert_raise(Errno::ESPIPE, Errno::EINVAL) { w.advise(:willneed) }
     end
   end
+
+  def assert_buffer_not_raise_shared_string_error
+    bug6764 = '[ruby-core:46586]'
+    size = 28
+    data = [*"a".."z", *"A".."Z"].shuffle.join("")
+    t = Tempfile.new("test_io")
+    t.write(data)
+    t.close
+    w = Tempfile.new("test_io")
+    assert_nothing_raised(RuntimeError, bug6764) do
+      File.open(t.path, "r") do |r|
+        buf = ''
+        while yield(r, size, buf)
+          w << buf
+        end
+      end
+    end
+    w.close
+    assert_equal(data, w.open.read, bug6764)
+  ensure
+    t.close!
+    w.close!
+  end
+
+  def test_read_buffer_not_raise_shared_string_error
+    assert_buffer_not_raise_shared_string_error do |r, size, buf|
+      r.read(size, buf)
+    end
+  end
+
+  def test_sysread_buffer_not_raise_shared_string_error
+    assert_buffer_not_raise_shared_string_error do |r, size, buf|
+      begin
+        r.sysread(size, buf)
+      rescue EOFError
+        nil
+      end
+    end
+  end
+
+  def test_readpartial_buffer_not_raise_shared_string_error
+    assert_buffer_not_raise_shared_string_error do |r, size, buf|
+      begin
+        r.readpartial(size, buf)
+      rescue EOFError
+        nil
+      end
+    end
+  end
 end