[regexp] break recursion in mutually recursive capture/back references.

src/ast/ast.cc

Index: src/ast/ast.cc
diff --git a/src/ast/ast.cc b/src/ast/ast.cc
index 3c8eb1ff7f1c109e4e9ee83824bc551815d2f55b..0fd1531387c62cb644fa383acab2c2e392dd0d1d 100644
--- a/src/ast/ast.cc
+++ b/src/ast/ast.cc
@@ -926,6 +926,35 @@ bool RegExpCapture::IsAnchoredAtEnd() {
 }
 
 
+int RegExpBackReference::max_match() {

[erikcorry, 2015/12/15 08:09:19]

Alternative simpler implementation is to return kInfinity here.

+  switch (max_match_) {
+    case kRecursionMarker:
+      // The back reference references a capture that references this back
+      // reference, leading to a recursion, e.g. /(\2)(\1)/.
+      // Such captures cannot be satisfied and have the length 0.
+      max_match_ = 0;
+      break;
+    case kUninitialized:
+      // The max match length of a back reference is the length of the capture.
+      if (capture_->body()) {
+        // Mark this back reference to break possible recursion before
+        // descending into the capture.
+        max_match_ = kRecursionMarker;
+        max_match_ = capture_->max_match();
+      } else {
+        // If the capture has no body, it has not been parsed and does not
+        // exist. Hence the length is 0.
+        max_match_ = 0;
+      }
+      break;
+    default:
+      // max_match_ has already been found.
+      break;
+  }
+  return max_match_;
+}
+
+
 // Convert regular expression trees to a simple sexp representation.
 // This representation should be different from the input grammar
 // in as many cases as possible, to make it more difficult for incorrect