Allow a null length pointer to sv_pvn_force_flags.

Add SvPV_force_nolen and use it to remove some C<n_a>s

p4raw-id: //depot/perl@24759

1 files changed, 1 insertions, 2 deletions

diff --git a/pp.c b/pp.c
index 4feb59d8f7..0e528cdf07 100644
--- a/pp.c
+++ b/pp.c
@@ -3121,8 +3121,7 @@ PP(pp_substr)
 	else if (lvalue) {		/* it's an lvalue! */
 	    if (!SvGMAGICAL(sv)) {
 		if (SvROK(sv)) {
-		    STRLEN n_a;
-		    SvPV_force(sv,n_a);
+		    SvPV_force_nolen(sv);
 		    if (ckWARN(WARN_SUBSTR))
 			Perl_warner(aTHX_ packWARN(WARN_SUBSTR),
 				"Attempt to use reference as lvalue in substr");