+ extern const char *os_strsignal(int); /* char to match strsignal in some OS */
+#endif
+#ifndef os_unsetenv
+ extern int os_unsetenv(const uschar *);
+#endif
+#ifndef os_getcwd
+ extern uschar *os_getcwd(uschar *, size_t);
+#endif
+
+#ifdef OS_PIPE_RW_EINTR
+ extern ssize_t os_pipe_read(int fd, void * buf, size_t count);
+ extern ssize_t os_pipe_write(int fd, void * buf, size_t count);
+ extern ssize_t os_pipe_writev(int fd, const struct iovec * iov, int iovcnt);
+#else
+# define os_pipe_read(fd, buf, count) read(fd, buf, count)
+# define os_pipe_write(fd, buf, count) write(fd, buf, count)
+# define os_pipe_writev(fd, buf, count) writev(fd, buf, count)