+ssize_t readlinkat (int, const char *, char *, size_t);
+int fstatat (int, char const *, struct stat *, int);
+int unsetenv (const char *);
+
+/* Constants. */
+#define EINPROGRESS 112
+/* Gnulib sets O_CLOEXEC to O_NOINHERIT, which gets in the way when we
+ need to redirect standard handles for subprocesses using temporary
+ files created by mkostemp, see callproc.c. */
+#ifdef O_CLOEXEC
+# undef O_CLOEXEC
+#endif
+#define O_CLOEXEC 0