+/* The results of open() in this file are not used with fchdir,
+ therefore save some unnecessary work in fchdir.c. */
+#undef open
+#undef close
+
+/* Many space usage primitives use all 1 bits to denote a value that is
+ not applicable or unknown. Propagate this information by returning
+ a uintmax_t value that is all 1 bits if X is all 1 bits, even if X
+ is unsigned and narrower than uintmax_t. */
+#define PROPAGATE_ALL_ONES(x) \
+ ((sizeof (x) < sizeof (uintmax_t) \
+ && (~ (x) == (sizeof (x) < sizeof (int) \
+ ? - (1 << (sizeof (x) * CHAR_BIT)) \
+ : 0))) \
+ ? UINTMAX_MAX : (uintmax_t) (x))
+
+/* Extract the top bit of X as an uintmax_t value. */
+#define EXTRACT_TOP_BIT(x) ((x) \
+ & ((uintmax_t) 1 << (sizeof (x) * CHAR_BIT - 1)))
+
+/* If a value is negative, many space usage primitives store it into an
+ integer variable by assignment, even if the variable's type is unsigned.
+ So, if a space usage variable X's top bit is set, convert X to the
+ uintmax_t value V such that (- (uintmax_t) V) is the negative of
+ the original value. If X's top bit is clear, just yield X.
+ Use PROPAGATE_TOP_BIT if the original value might be negative;
+ otherwise, use PROPAGATE_ALL_ONES. */
+#define PROPAGATE_TOP_BIT(x) ((x) | ~ (EXTRACT_TOP_BIT (x) - 1))
+
+#ifdef STAT_STATVFS
+/* Return true if statvfs works. This is false for statvfs on systems
+ with GNU libc on Linux kernels before 2.6.36, which stats all
+ preceding entries in /proc/mounts; that makes df hang if even one
+ of the corresponding file systems is hard-mounted but not available. */
+# if ! (__linux__ && (__GLIBC__ || __UCLIBC__))
+/* The FRSIZE fallback is not required in this case. */
+# undef STAT_STATFS2_FRSIZE
+static int statvfs_works (void) { return 1; }
+# else
+# include <string.h> /* for strverscmp */
+# include <sys/utsname.h>
+# include <sys/statfs.h>
+# define STAT_STATFS2_BSIZE 1