- tem = (char *) xrealloc (buf, bufp->size + 1);
- bufp->ptr = (bufp->ptr - buf) + tem;
- append_end = (append_end - buf) + tem;
- bufp->beg = buf = tem;
+ ptrdiff_t size = bufp->size + 1;
+ bufp->beg = buf = xpalloc (buf, &size, 1, -1, 1);
+ bufp->size = size - 1;
+ bufp->ptr = buf + ptr_offset;
+ append_end = buf + append_end_offset;