Detect cycles in rlcp_tree.

This will be required when the parser becomes
capable of creating object graphs with cycles.

* parser.c (parser_callgraph_circ_check): New function.

* parser.h (struct circ_stack): New struct.
(parser_callgraph_circ_check): Declared.

* parser.y (rlcp_tree_rec): New static function.
(rlcp_tree): Reduced to wrapper for rlcp_tree_rec.

1 files changed, 16 insertions, 3 deletions

diff --git a/parser.y b/parser.y
index c5874ed8..8ae40e82 100644
--- a/parser.y
+++ b/parser.y
@@ -1501,17 +1501,30 @@ val rlrec(parser_t *parser, val form, val line)
   return form;
 }
 
-val rlcp_tree(val to, val from)
+static val rlcp_tree_rec(val to, val from, struct circ_stack *up)
 {
   val ret = to;
 
-  for (; consp(to); to = cdr(to)) {
+  while (consp(to)) {
+    val a = car(to);
+    struct circ_stack rlcs = { up, a };
     rlcp(to, from);
-    rlcp_tree(car(to), from);
+    if (!parser_callgraph_circ_check(up, a))
+      break;
+    rlcp_tree_rec(a, from, &rlcs);
+    to = cdr(to);
+    if (!parser_callgraph_circ_check(up, to))
+      break;
   }
   return ret;
 }
 
+
+val rlcp_tree(val to, val from)
+{
+  return rlcp_tree_rec(to, from, 0);
+}
+
 static wchar_t char_from_name(const wchar_t *name)
 {
   static struct {