smtp: fix compiler warning

- Fix clang string-plus-int warning.

Clang 8 warns about adding a string to an int does not append to the
string. Indeed it doesn't, but that was not the intention either. Use
array indexing as suggested to silence the warning. There should be no
functional changes.

(In other words clang warns about "foo"+2 but not &"foo"[2] so use the
latter.)

smtp.c:1221:29: warning: adding 'int' to a string does not append to the
string [-Wstring-plus-int]
      eob = strdup(SMTP_EOB + 2);
            ~~~~~~~~~~~~~~~~^~~~

Closes https://github.com/curl/curl/pull/3729

1 files changed, 1 insertions, 1 deletions

diff --git a/lib/smtp.c b/lib/smtp.c
index f3db714b5..fec0026a2 100644
--- a/lib/smtp.c
+++ b/lib/smtp.c
@@ -1218,7 +1218,7 @@ static CURLcode smtp_done(struct connectdata *conn, CURLcode status,
        returned CURLE_AGAIN, we duplicate the EOB now rather than when the
        bytes written doesn't equal len. */
     if(smtp->trailing_crlf || !conn->data->state.infilesize) {
-      eob = strdup(SMTP_EOB + 2);
+      eob = strdup(&SMTP_EOB[2]);
       len = SMTP_EOB_LEN - 2;
     }
     else {