configure: Fix check for fdatasync()
Under Darwin, a symbol exists for the fdatasync() function, so that our
link test succeeds. However _POSIX_SYNCHRONIZED_IO is set to '-1'.
According to POSIX:2008, a value of -1 means the feature is not supported.
A value of 0 means supported at compilation time, and a value greater 0
means supported at both compilation and run time.
Enable fdatasync() only if _POSIX_SYNCHRONIZED_IO is '>0'.
Signed-off-by: Alexandre Raymond <[email protected]>
Signed-off-by: Andreas Färber <[email protected]>
diff --git a/configure b/configure
index c931ae8..6101f4e 100755
--- a/configure
+++ b/configure
@@ -2461,7 +2461,13 @@
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
