add OPpDEREFed flag to avoid double mg_get()

    The previous commit made various ops such as rv2av unconditionally do
    an SvGETMAGIC(). Under some circumstances this could cause a double
    mg_get() (and hence double FETCH etc). In particular, when the
    proceeding op was something like aelem with OPpDEREF, the aelem would
    call vivify_ref(), which would call magic. So in peep(), mark
    OP_RV2[SAH]V ops with the new OPpDEREFed flag if the preceding op was
    OPpDEREF. Then use this flag to avoid a second dose of magic.

    Note that RV2GV probably needs this flag too, but there weren't any
    spare private flag bits left for that op (I think).

1 files changed, 2 insertions, 0 deletions

diff --git a/op.h b/op.h
index b9327bbb1f..b66c4a1563 100644
--- a/op.h
+++ b/op.h
@@ -191,6 +191,8 @@ Deprecated.  Use C<GIMME_V> instead.
 #define OPpDEREF_AV		32	/*   Want ref to AV. */
 #define OPpDEREF_HV		64	/*   Want ref to HV. */
 #define OPpDEREF_SV		(32|64)	/*   Want ref to SV. */
+/* Private for OP_RV2SV, OP_RV2AV, OP_RV2AV */
+#define OPpDEREFed		4	/* prev op was OPpDEREF */
   /* OP_ENTERSUB only */
 #define OPpENTERSUB_DB		16	/* Debug subroutine. */
 #define OPpENTERSUB_HASTARG	32	/* Called from OP tree. */