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, 12 insertions, 0 deletions

diff --git a/txr.1 b/txr.1
index a8eb365c..5bdf24a6 100644
--- a/txr.1
+++ b/txr.1
@@ -28195,6 +28195,18 @@ be monotonically increasing, after consideration of the
 displacement of negative values.
 
 If
+.meta replacement-sequence
+shares storage with the target range of
+.metn sequence ,
+or, in the case when that range is resized by the
+.code replace
+operation, shares storage with any portion of
+.meta sequence
+above that range, then the effect of
+.code replace
+on either object is unspecified.
+
+If
 .meta sequence
 is a
 .code carray