[perl #92254, #92256] Fix SAVE_DEFSV to do refcounting

The current definition of SAVE_DEFSV doesn’t take reference count-
ing into account.  Every instance of it in the perl core is buggy
as a result.

Most are also followed by DEFSV_set, which is likewise buggy.

This commit implements SAVE_DEFSV in terms of save_gp and
SAVEGENERICSV if PERL_CORE is defined.  save_gp and SAVEGENERICSV are
what local(*_) = \$foo uses.  Changing the definition for XS code is
probably too risky this close to 5.16.  It should probably be changed
later, though.

DEFSV_set is now changed to do reference counting too.

1 files changed, 9 insertions, 1 deletions

diff --git a/t/op/grep.t b/t/op/grep.t
index 0a1f8c9090..94fa43cf6c 100644
--- a/t/op/grep.t
+++ b/t/op/grep.t
@@ -10,7 +10,7 @@ BEGIN {
     require "test.pl";
 }
 
-plan( tests => 61 );
+plan( tests => 62 );
 
 {
     my @lol = ([qw(a b c)], [], [qw(1 2 3)]);
@@ -214,3 +214,11 @@ plan( tests => 61 );
     like($@, qr/Missing comma after first argument to grep function/,
          "proper error on variable as block. [perl #37314]");
 }
+
+# [perl #92254] freeing $_ in gremap block
+{
+    my $y;
+    grep { undef *_ } $y;
+    map { undef *_ } $y;
+}
+pass 'no double frees with grep/map { undef *_ }';