avoid undefined behaviour in fetch and modify of SP from 0a0e3cc51e

pp_sys.c: In function ‘Perl_pp_send’:
pp_sys.c:1845: warning: operation on ‘sp’ may be undefined

1 files changed, 2 insertions, 1 deletions

diff --git a/pp_sys.c b/pp_sys.c
index 3f43e495a1..711f93aad7 100644
--- a/pp_sys.c
+++ b/pp_sys.c
@@ -1842,7 +1842,8 @@ PP(pp_send)
 	MAGIC * const mg = SvTIED_mg((const SV *)io, PERL_MAGIC_tiedscalar);
 	if (mg) {
 	    if (MARK == SP - 1) {
-		mXPUSHi(sv_len(*SP));
+		SV *sv = *SP;
+		mXPUSHi(sv_len(sv));
 		PUTBACK;
 	    }