-#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)
+#ifndef EXIM_HAVE_STRCHRNUL
+extern char * strchrnul(const char *, int);