Remove SvIsCOW checks from mg.c:mg_localize

It no longer needs to worry about SvIsCOW.  This logic is left over
from when READONLY+FAKE was used for COWs.

Since it is possible for COWs to be read-only now, this logic is actu-
ally faulty, as it doesn’t temporarily stop read-only COWs from being
read-only, as it does for other read-only values.

This actually causes discrepancies with scalar-tied locked hash keys,
which differ in readonliness when localised depending on whether the previous value used copy-on-write.

Whether such scalars should be read-only after localisation is open
to debate, but it should not differ based on the means of storing the
previous value.

1 files changed, 1 insertions, 1 deletions

diff --git a/mg.c b/mg.c
index d22f620c91..0ce58ab5d2 100644
--- a/mg.c
+++ b/mg.c
@@ -526,7 +526,7 @@ Perl_mg_localize(pTHX_ SV *sv, SV *nsv, bool setmagic)
 			    mg->mg_ptr, mg->mg_len);
 
 	/* container types should remain read-only across localization */
-	if (!SvIsCOW(sv)) SvFLAGS(nsv) |= SvREADONLY(sv);
+	SvFLAGS(nsv) |= SvREADONLY(sv);
     }
 
     if (SvTYPE(nsv) >= SVt_PVMG && SvMAGIC(nsv)) {