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.

2 files changed, 10 insertions, 9 deletions

diff --git a/ext/Devel-Peek/Peek.pm b/ext/Devel-Peek/Peek.pm
index d0ed3943b6..c17401b66d 100644
--- a/ext/Devel-Peek/Peek.pm
+++ b/ext/Devel-Peek/Peek.pm
@@ -3,7 +3,7 @@
 
 package Devel::Peek;
 
-$VERSION = '1.17';
+$VERSION = '1.18';
 $XS_VERSION = $VERSION;
 $VERSION = eval $VERSION;
 
diff --git a/ext/Devel-Peek/Peek.xs b/ext/Devel-Peek/Peek.xs
index 0d8b833267..cb3d0ba553 100644
--- a/ext/Devel-Peek/Peek.xs
+++ b/ext/Devel-Peek/Peek.xs
@@ -360,12 +360,13 @@ S_ck_dump(pTHX_ OP *entersubop, GV *namegv, SV *cv)
 			   newSVpvn_flags("$;$", 3, SVs_TEMP));
 
     aop = cUNOPx(entersubop)->op_first;
-    if (!aop->op_sibling)
+    if (!OP_HAS_SIBLING(aop))
 	aop = cUNOPx(aop)->op_first;
     prev = aop;
-    aop = aop->op_sibling;
+    aop = OP_SIBLING(aop);
     first = aop;
-    prev->op_sibling = first->op_sibling;
+    OP_SIBLING_set(prev, OP_SIBLING(first));
+
     if (first->op_type == OP_RV2AV ||
 	first->op_type == OP_PADAV ||
 	first->op_type == OP_RV2HV ||
@@ -374,7 +375,7 @@ S_ck_dump(pTHX_ OP *entersubop, GV *namegv, SV *cv)
 	first->op_flags |= OPf_REF;
     else
 	first->op_flags &= ~OPf_MOD;
-    aop = aop->op_sibling;
+    aop = OP_SIBLING(aop);
     if (!aop) {
 	/* It doesn’t really matter what we return here, as this only
 	   occurs after yyerror.  */
@@ -384,12 +385,12 @@ S_ck_dump(pTHX_ OP *entersubop, GV *namegv, SV *cv)
 
     /* aop now points to the second arg if there is one, the cvop otherwise
      */
-    if (aop->op_sibling) {
-	prev->op_sibling = aop->op_sibling;
+    if (OP_HAS_SIBLING(aop)) {
+	OP_SIBLING_set(prev, OP_SIBLING(aop));
 	second = aop;
-	second->op_sibling = NULL;
+	OP_SIBLING_set(second, NULL);
     }
-    first->op_sibling = second;
+    OP_SIBLING_set(first, second);
 
     op_free(entersubop);