Fix CvOUTSIDE for state subs in predeclared subs

use 5.018;
use experimental 'lexical_subs';
$::x = "global";
sub x;
sub x {
    state $x = 42;
    state sub x { print eval '$x', "\n" }
    \&x;
}
x()->();
__END__

Output:

Segmentation fault: 11

Because this line in pad.c:S_findpadlex:

1141	    const PADLIST * const padlist = CvPADLIST(cv);

is trying to read this SV:

SV = UNKNOWN(0x76) (0xaa170e4fd) at 0x10060c928
  REFCNT = 1697135711
  FLAGS = (PADSTALE,TEMP,GMG,SMG,IOK,pNOK,pPOK,UTF8)

(i.e., gibberish).

During compilation, ‘sub x{’ creates a new CV.  When the sub is about
to be installed (when the final ‘}’ is reached), the existing stub
must be reused.  So everything is copied from the new CV (PL_compcv)
to the stub.  Also, any CvOUTSIDE pointers of nested subs get updated
to point to the erstwhile stub.

State subs were not getting their CvOUTSIDE pointers updated.  This
patch implements that.

1 files changed, 13 insertions, 1 deletions

diff --git a/t/op/lexsub.t b/t/op/lexsub.t
index f43285f115..2ba7635e14 100644
--- a/t/op/lexsub.t
+++ b/t/op/lexsub.t
@@ -7,7 +7,7 @@ BEGIN {
     *bar::is = *is;
     *bar::like = *like;
 }
-plan 147;
+plan 148;
 
 # -------------------- Errors with feature disabled -------------------- #
 
@@ -431,6 +431,18 @@ is runperl(switches => ['-lXMfeature=:all'],
   like $@, qr/^Undefined subroutine &φου called at /,
     'state sub with utf8 name';
 }
+# This used to crash, but only as a standalone script
+is runperl(switches => ['-lXMfeature=:all'],
+           prog     => '$::x = global=>;
+                        sub x;
+                        sub x {
+                          state $x = 42;
+                          state sub x { print eval q|$x| }
+                          x()
+                        }
+                        x()',
+           stderr   => 1), "42\n",
+  'closure behaviour of state sub in predeclared package sub';
 
 # -------------------- my -------------------- #