#253 JTidy goes into infinite loop on specific input document

[Anonymous]

JTidy goes into infinite loop on specific input document:

http://www.takeovers.govt.nz/enforcement/decisions/2004/meeting-wrightson.php

When we call tidy.parse() the stack traces ends in many calls to Node.checkNodeIntegrity()
and the CPU is pegged at 100%

We're using the latest version of JTidy (r938). I've attached a copy of the input document
which triggers the behaviour.

Hopefully it's not too difficult to fix :)

Many thanks,

• Francis.

[Anonymous]

Copy of input which causes infinite loop

[Anonymous]

And here's a more minimal document which exhibits the problem:

[Anonymous]

Sorry - there was typo in the version I gave to Francis there... Make that...

(i.e. the extra opening html tag is not required, and the close html can be present)

From a quick investigation the problem seems to be that parser is producing a cycle of br tags (with A followed by B and B followed by A) below the dd tag.

e.g.

[Node type=RootNode,element=null,content=
[Node type=StartTag,element=html,content=
[Node type=StartTag,element=head,content=
[Node type=StartTag,element=title,content=null]],
[Node type=StartTag,element=body,content=
[Node type=TextNode,element=null,text="",content=null],
[Node type=StartTag,element=dl,content=
[Node type=StartTag,element=dd,content=
[Node type=StartTag,element=br,content=null],
[Node type=StartTag,element=br,content=null],
[Node type=StartTag,element=br,content=null],
[Node type=StartTag,element=br,content=null],
[Node type=StartTag,element=br,content=null],
[Node type=StartTag,element=br,content=null],
[Node type=StartTag,element=br,content=null],
[Node type=StartTag,element=br,content=null],
...

Though not a proper fix, this patch will detect the cycle and throw a RuntimeException (and will also limit the loop in toString to help see what's happening as above).

Index: src/main/java/org/w3c/tidy/Node.java

--- src/main/java/org/w3c/tidy/Node.java (revision 1261)
+++ src/main/java/org/w3c/tidy/Node.java (working copy)
@@ -1311,7 +1311,11 @@

    for (child = this.content; child != null; child = child.next)
    {

• if (child.parent != this || !child.checkNodeIntegrity())
• if (this.next != null && this.next.next == this) {
• throw new RuntimeException("Cycle detected - aborting");
• }
  +

• if (child.parent != this || !child.checkNodeIntegrity())
  {
  return false;
  }
  @@ -1347,8 +1351,15 @@
  String s = "";
  Node n = this;

• int loopLimit = 1024;
  while (n != null)
  {

• if (loopLimit < 0) {
• s += "...TRUNCATED...";
• n = null;
• break;
• }
• loopLimit--;
  s += "[Node type=";
  s += NODETYPE_STRING[n.type];
  s += ",element=";