[Qemu-trivial] [PATCH 1/6] Fix incorrect check for fdatasync() in configure

[Alexandre Raymond]

For some reason, darwin provides a symbol for fdatasync(), but
doesn't officially support it.

The manpage for fdatasync on Linux states the following:

"On POSIX  systems  on  which fdatasync() is available,
_POSIX_SYNCHRONIZED_IO is defined in <unistd.h> to a value greater than 0."

In fact, unistd.h defines this value to "-1", at least on OSX 10.6.7.

Add this check to the configure file.

Signed-off-by: Alexandre Raymond <address@hidden>
---
 configure |    8 +++++++-
 1 files changed, 7 insertions(+), 1 deletions(-)

diff --git a/configure b/configure
index a318d37..b21ef75 100755
--- a/configure
+++ b/configure
@@ -2477,7 +2477,13 @@ fi
 fdatasync=no
 cat > $TMPC << EOF
 #include <unistd.h>
-int main(void) { return fdatasync(0); }
+int main(void) {
+#if defined(_POSIX_SYNCHRONIZED_IO) && _POSIX_SYNCHRONIZED_IO > 0
+return fdatasync(0);
+#else
+#abort Not supported
+#endif
+}
 EOF
 if compile_prog "" "" ; then
     fdatasync=yes
-- 
1.7.5