[Patch] [v2] Add Comment to io/fcntl.h

[Patsy Franklin <pfrankli at redhat dot com>]

Thanks Roland.

How about this?

v1
- Initial submission.
v2
- Included missing ChangeLog.
- Adjusted wording.
- Two spaces after periods.
- Reflow text to 80 characters.

2013-02-25  Patsy Franklin<pfrankli@redhat.com>

	* io/fcntl.h: Added a comment about AT_EACCESS and AT_REMOVEDIR.

diff --git a/io/fcntl.h b/io/fcntl.h
index 61834ce..0f37fce 100644
--- a/io/fcntl.h
+++ b/io/fcntl.h
@@ -129,6 +129,12 @@ typedef __pid_t pid_t;
 # define SEEK_END      2       /* Seek from end of file.  */
 #endif /* XPG */

+/* The constants AT_REMOVEDIR and AT_EACCESS have the same value.  The
+   AT_EACCESS value is only used by faccessat() and the AT_REMOVEDIR value is
+   only used by unlinkat().  The two functions do completely different things
+   and therefore the flags can be allowed to overlap.  For example, passing
+   AT_REMOVEDIR to faccessat() would be undefined behavior and thus treating
+   it equivalent to AT_EACCESS is valid undefined behavior.  */
 #ifdef __USE_ATFILE
 # define AT_FDCWD              -100    /* Special value used to indicate
                                           the *at functions should use the
---