[PATCH] fdatasync: minor improvements

[Eric Blake]

Picks up some ideas by Paul Eggert from here:
https://lists.gnu.org/archive/html/bug-coreutils/2011-07/msg00157.html

* modules/fdatasync (Depends-on): Add condition for fsync.
* lib/fdatasync.c (fdatasync): Add comment.
* tests/test-unistd-c++.cc: Test fdatasync.

Signed-off-by: Eric Blake <address@hidden>
---
 ChangeLog                |    5 +++++
 lib/fdatasync.c          |    2 ++
 modules/fdatasync        |    2 +-
 tests/test-unistd-c++.cc |    4 ++++
 4 files changed, 12 insertions(+), 1 deletions(-)

diff --git a/ChangeLog b/ChangeLog
index c76f3ae..7783d07 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,5 +1,10 @@
 2011-09-16  Eric Blake  <address@hidden>

+       fdatasync: minor improvements
+       * modules/fdatasync (Depends-on): Add condition for fsync.
+       * lib/fdatasync.c (fdatasync): Add comment.
+       * tests/test-unistd-c++.cc: Test fdatasync.
+
        unistd: update refs to newer POSIX
        * lib/unistd.in.h: Prefer POSIX 2008 over 2001.
        Suggested by Bruno Haible.
diff --git a/lib/fdatasync.c b/lib/fdatasync.c
index 54c10fd..3d26793 100644
--- a/lib/fdatasync.c
+++ b/lib/fdatasync.c
@@ -21,5 +21,7 @@
 int
 fdatasync (int fd)
 {
+  /* This does more work than strictly necessary, but is the best we
+     can do portably.  */
   return fsync (fd);
 }
diff --git a/modules/fdatasync b/modules/fdatasync
index 7b78a80..19c1aee 100644
--- a/modules/fdatasync
+++ b/modules/fdatasync
@@ -6,7 +6,7 @@ lib/fdatasync.c
 m4/fdatasync.m4

 Depends-on:
-fsync
+fsync         [test $HAVE_FDATASYNC = 0]
 unistd

 configure.ac:
diff --git a/tests/test-unistd-c++.cc b/tests/test-unistd-c++.cc
index 12e415b..fb7425b 100644
--- a/tests/test-unistd-c++.cc
+++ b/tests/test-unistd-c++.cc
@@ -60,6 +60,10 @@ SIGNATURE_CHECK (GNULIB_NAMESPACE::fchownat, int,
                  (int, char const *, uid_t, gid_t, int));
 #endif

+#if GNULIB_TEST_FDATASYNC
+SIGNATURE_CHECK (GNULIB_NAMESPACE::fdatasync, int, (int));
+#endif
+
 #if GNULIB_TEST_FSYNC
 SIGNATURE_CHECK (GNULIB_NAMESPACE::fsync, int, (int));
 #endif
-- 
1.7.4.4