In-place sort should not leave array read-only

$ ./perl -Ilib -e '@a=1..2; eval { @a=sort{die} @a }; warn "ok so far\n"; @a = 1'
ok so far
Modification of a read-only value attempted at -e line 1.

If something goes wrong inside the sort block and it dies, we still
need to make sure we turn off the read-only flag on that array.

1 files changed, 3 insertions, 0 deletions

diff --git a/pp_sort.c b/pp_sort.c
index 56c0aac5db..a67ad4e335 100644
--- a/pp_sort.c
+++ b/pp_sort.c
@@ -1588,7 +1588,10 @@ PP(pp_sort)
 	    if (SvREADONLY(av))
 		Perl_croak_no_modify();
 	    else
+	    {
 		SvREADONLY_on(av);
+		save_pushptr((void *)av, SAVEt_READONLY_OFF);
+	    }
 	    p1 = p2 = AvARRAY(av);
 	    sorting_av = 1;
 	}