[PATCH] dfa: port to gcc -fsanitize=undefined

[Paul Eggert]

* lib/dfa.c (copy): Don’t pass NULL with size 0 to memcpy,
as this runs afoul of gcc -fsanitize=undefined.
---
 ChangeLog | 6 ++++++
 lib/dfa.c | 3 ++-
 2 files changed, 8 insertions(+), 1 deletion(-)

diff --git a/ChangeLog b/ChangeLog
index f13c784..e0b836b 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,9 @@
+2017-01-15  Paul Eggert  <address@hidden>
+
+       dfa: port to gcc -fsanitize=undefined
+       * lib/dfa.c (copy): Don’t pass NULL with size 0 to memcpy,
+       as this runs afoul of gcc -fsanitize=undefined.
+
 2017-01-14  Paul Eggert  <address@hidden>
 
        strftime: %z is -00 if unknown
diff --git a/lib/dfa.c b/lib/dfa.c
index 5df27ea..f6c3017 100644
--- a/lib/dfa.c
+++ b/lib/dfa.c
@@ -1999,8 +1999,9 @@ copy (position_set const *src, position_set *dst)
       dst->elems = xpalloc (NULL, &dst->alloc, src->nelem - dst->alloc, -1,
                             sizeof *dst->elems);
     }
-  memcpy (dst->elems, src->elems, src->nelem * sizeof *dst->elems);
   dst->nelem = src->nelem;
+  if (src->nelem != 0)
+    memcpy (dst->elems, src->elems, src->nelem * sizeof *dst->elems);
 }
 
 static void
-- 
2.9.3