+#include <openssl/opensslconf.h> /* OPENSSL_UNISTD */
+
+#ifdef MSDOS
+# define OPENSSL_UNISTD_IO <io.h>
+# define OPENSSL_DECLARE_EXIT extern void exit(int);
+#else
+# define OPENSSL_UNISTD_IO OPENSSL_UNISTD
+# define OPENSSL_DECLARE_EXIT /* declared in unistd.h */
+#endif
+