merges r20954 from trunk into ruby_1_9_1.

* io.c (rb_io_init_copy): call io_seek only if io_tell succeeds.

git-svn-id: http://svn.ruby-lang.org/repos/ruby/branches/ruby_1_9_1@21018 b2dd03c8-39d4-4d8f-98ff-823fe69b080e

2 files changed, 8 insertions, 1 deletions

diff --git a/ChangeLog b/ChangeLog
index b0fd4eb63..6a9e200ea 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,7 @@
+Tue Dec 23 23:49:37 2008  Tanaka Akira  <akr@fsij.org>
+
+	* io.c (rb_io_init_copy): call io_seek only if io_tell succeeds.
+
 Tue Dec 23 20:28:28 2008  Yuki Sonoda (Yugui)  <yugui@yugui.jp>
 
 	* io.c: rdoc for File::open and 1.9 feature in file modes.
diff --git a/io.c b/io.c
index 27da626ff..605799259 100644
--- a/io.c
+++ b/io.c
@@ -5338,6 +5338,7 @@ rb_io_init_copy(VALUE dest, VALUE io)
     rb_io_t *fptr, *orig;
     int fd;
     VALUE write_io;
+    off_t pos;
 
     io = rb_io_get_io(io);
     if (dest == io) return dest;
@@ -5356,7 +5357,9 @@ rb_io_init_copy(VALUE dest, VALUE io)
 
     fd = ruby_dup(orig->fd);
     fptr->fd = fd;
-    io_seek(fptr, io_tell(orig), SEEK_SET);
+    pos = io_tell(orig);
+    if (0 <= pos)
+        io_seek(fptr, pos, SEEK_SET);
     if (fptr->mode & FMODE_BINMODE) {
 	rb_io_binmode(dest);
     }