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

test/cctest/test-regexp.cc

 // Copyright 2012 the V8 project authors. All rights reserved.
 // Redistribution and use in source and binary forms, with or without
 // modification, are permitted provided that the following conditions are
 // met:
 //
 //     * Redistributions of source code must retain the above copyright
 //       notice, this list of conditions and the following disclaimer.
 //     * Redistributions in binary form must reproduce the above
 //       copyright notice, this list of conditions and the following
 //       disclaimer in the documentation and/or other materials provided
@@ skipping 92 matching lines @@
   v8::HandleScope scope(CcTest::isolate());
   Zone zone;
   FlatStringReader reader(CcTest::i_isolate(), CStrVector(input));
   RegExpCompileData result;
   CHECK(v8::internal::RegExpParser::ParseRegExp(
       CcTest::i_isolate(), &zone, &reader, false, false, &result));
   CHECK(result.tree != NULL);
   CHECK(result.error.is_null());
   std::ostringstream os;
   result.tree->Print(os, &zone);
+  if (strcmp(expected, os.str().c_str()) != 0) {
+    printf("%s | %s\n", expected, os.str().c_str());
+  }
   CHECK_EQ(0, strcmp(expected, os.str().c_str()));
 }
 
 
 static bool CheckSimple(const char* input) {
   v8::HandleScope scope(CcTest::isolate());
   Zone zone;
   FlatStringReader reader(CcTest::i_isolate(), CStrVector(input));
   RegExpCompileData result;
   CHECK(v8::internal::RegExpParser::ParseRegExp(
@@ skipping 139 matching lines @@
                " (# 0 - g '\\x04'))");
   CheckParseEq("(x)(x)(x)(x)(x)(x)(x)(x)(x)(x)\\10",
                "(: (^ 'x') (^ 'x') (^ 'x') (^ 'x') (^ 'x') (^ 'x')"
                " (^ 'x') (^ 'x') (^ 'x') (^ 'x') (<- 10))");
   CheckParseEq("(x)(x)(x)(x)(x)(x)(x)(x)(x)(x)\\11",
                "(: (^ 'x') (^ 'x') (^ 'x') (^ 'x') (^ 'x') (^ 'x')"
                " (^ 'x') (^ 'x') (^ 'x') (^ 'x') '\\x09')");
   CheckParseEq("(a)\\1", "(: (^ 'a') (<- 1))");
   CheckParseEq("(a\\1)", "(^ 'a')");
   CheckParseEq("(\\1a)", "(^ 'a')");
+  CheckParseEq("(\\2)(\\1)", "(: (^ (<- 2)) (^ (<- 1)))");
   CheckParseEq("(?=a)?a", "'a'");
   CheckParseEq("(?=a){0,10}a", "'a'");
   CheckParseEq("(?=a){1,10}a", "(: (-> + 'a') 'a')");
   CheckParseEq("(?=a){9,10}a", "(: (-> + 'a') 'a')");
   CheckParseEq("(?!a)?a", "'a'");
   CheckParseEq("\\1(a)", "(: (<- 1) (^ 'a'))");
   CheckParseEq("(?!(a))\\1", "(: (-> - (^ 'a')) (<- 1))");
   CheckParseEq("(?!\\1(a\\1)\\1)\\1",
                "(: (-> - (: (<- 1) (^ 'a') (<- 1))) (<- 1))");
   CheckParseEq("\\1\\2(a(?:\\1(b\\1\\2))\\2)\\1",
@@ skipping 1554 matching lines @@
 
   ZoneList<CharacterRange> first_only(4, &zone);
   ZoneList<CharacterRange> second_only(4, &zone);
   ZoneList<CharacterRange> both(4, &zone);
 }
 
 
 TEST(Graph) {
   Execute("\\b\\w+\\b", false, true, true);
 }