allow wrap-around of PL_cop_seqmax

After a large number of evals, PL_cop_seqmax (a U32) will wrap around
again to zero. Make the code handle this case by:

1) When incrementing PL_cop_seqmax, never allow its value to become
   equal to PERL_PADSEQ_INTRO;
2) When testing for COP_SEQ_RANGE_LOW < seq <= COP_SEQ_RANGE_HIGH,
   allow for the fact that _HIGH may be lower than _LOW.

This is a final fix for  [perl #83364].

1 files changed, 2 insertions, 0 deletions

diff --git a/op.c b/op.c
index ad94f6ef8d..2e15a8dc68 100644
--- a/op.c
+++ b/op.c
@@ -4356,6 +4356,8 @@ Perl_utilize(pTHX_ int aver, I32 floor, OP *version, OP *idop, OP *arg)
     PL_parser->copline = NOLINE;
     PL_parser->expect = XSTATE;
     PL_cop_seqmax++; /* Purely for B::*'s benefit */
+    if (PL_cop_seqmax == PERL_PADSEQ_INTRO) /* not a legal value */
+	PL_cop_seqmax++;
 
 #ifdef PERL_MAD
     if (!PL_madskills) {