* io.c (io_unread): fix IO#pos with mode 'r' bug on Windows.

  If the end of reading buffer is CR, io_unread() needs to unread one
  more byte.
  [ruby-core:44874] [Bug #6401]

* test/ruby/test_io_m17n.rb (TestIO_M17N#test_pos_with_buffer_end_cr):
  add a test for above.

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@35594 b2dd03c8-39d4-4d8f-98ff-823fe69b080e

1 files changed, 6 insertions, 0 deletions

diff --git a/io.c b/io.c
index c4b7f128e0..5997c29611 100644
--- a/io.c
+++ b/io.c
@@ -457,6 +457,12 @@ io_unread(rb_io_t *fptr)
     /* add extra offset for removed '\r' in rbuf */
     extra_max = (long)(pos - fptr->rbuf.len);
     p = fptr->rbuf.ptr + fptr->rbuf.off;
+
+    /* if the end of rbuf is '\r', rbuf doesn't have '\r' within rbuf.len */
+    if (*(fptr->rbuf.ptr + fptr->rbuf.capa - 1) == '\r') {
+	newlines++;
+    }
+
     for (i = 0; i < fptr->rbuf.len; i++) {
 	if (*p == '\n') newlines++;
 	if (extra_max == newlines) break;