replace: deal with overlapping.

* buf.c (replace_buf): In the same-type case, use memmove
rather than memcpy in case the objects overlap, so we
don't invoke C undefined behavior.

* lib.c (replace_str, replace_vec): Likewise.

* txr.1: Specify that if the replacement sequence overlaps
with the target range of the destination sequence, or
with any portion that has to be relocated if range
changes size, then the behavior is unspecified.

1 files changed, 1 insertions, 1 deletions

diff --git a/buf.c b/buf.c
index d95a9033..928eaece 100644
--- a/buf.c
+++ b/buf.c
@@ -339,7 +339,7 @@ val replace_buf(val buf, val items, val from, val to)
     if (zerop(len_it))
       return buf;
     if (bufp(items)) {
-      memcpy(buf->b.data + c_num(from), items->b.data, c_num(len_it));
+      memmove(buf->b.data + c_num(from), items->b.data, c_num(len_it));
     } else {
       seq_iter_t item_iter;
       seq_iter_init(self, &item_iter, items);