wrap op_sibling field access in OP_SIBLING* macros

Remove (almost all) direct access to the op_sibling field of OP structs,
and use these three new macros instead:

    OP_SIBLING(o);
    OP_HAS_SIBLING(o);
    OP_SIBLING_set(o, new_value);

OP_HAS_SIBLING is intended to be a slightly more efficient version of
OP_SIBLING when only boolean context is needed.

For now these three macros are just defined in the obvious way:

    #define OP_SIBLING(o)          (0 + (o)->op_sibling)
    #define OP_HAS_SIBLING(o)      (cBOOL((o)->op_sibling))
    #define OP_SIBLING_set(o, sib) ((o)->op_sibling = (sib))

but abstracting them out will allow us shortly to make the last pointer in
an op_sibling chain point back to the parent rather than being null, with
a new flag indicating whether this is the last op.

Perl_ck_fun() still has a couple of direct uses of op_sibling, since it
takes the field's address, which is not covered by these macros.

1 files changed, 1 insertions, 1 deletions

diff --git a/regexec.c b/regexec.c
index 9100e474f8..58b3f60245 100644
--- a/regexec.c
+++ b/regexec.c
@@ -5318,7 +5318,7 @@ S_regmatch(pTHX_ regmatch_info *reginfo, char *startpos, regnode *prog)
 			assert(o->op_targ == OP_LEAVE);
 			o = cUNOPo->op_first;
 			assert(o->op_type == OP_ENTER);
-			o = o->op_sibling;
+			o = OP_SIBLING(o);
 		    }
 
 		    if (o->op_type != OP_STUB) {