heart: remove garbage appended to heart command

heart:get_cmd/0 is documented to return an empty string if the command is
cleared. get_cmd/0 returns 2 extra bytes: 1 byte for the trailing null,
1 byte from the op (the op is an unsigned char and 2 bytes are allocated
for it in the returned buffer).

1> heart:get_cmd().
{ok,[0,0]}
2> heart:set_cmd("echo hello").
ok
3> heart:get_cmd().
{ok,[101,99,104,111,32,104,101,108,108,111,0,0]}
4> heart:clear_cmd().
ok
5> heart:get_cmd().
{ok,[0,99]}

1 files changed, 3 insertions, 3 deletions

diff --git a/erts/etc/common/heart.c b/erts/etc/common/heart.c
index 778b3569c7..7a5746e630 100644
--- a/erts/etc/common/heart.c
+++ b/erts/etc/common/heart.c
@@ -727,16 +727,16 @@ static int
 heart_cmd_reply(int fd, char *s)
 {
   struct msg m;
-  int len = strlen(s) + 1;	/* Include \0 */
+  int len = strlen(s);
 
   /* if s >= MSG_BODY_SIZE, return a write
    * failure immediately.
    */
-  if (len > sizeof(m.fill))
+  if (len >= sizeof(m.fill))
       return -1;
 
   m.op = HEART_CMD;
-  m.len = htons(len + 2);	/* Include Op */
+  m.len = htons(len + 1);	/* Include Op */
   strcpy((char*)m.fill, s);
 
   return write_message(fd, &m);