regexp hangs forever

[dvega]

This code hangs forever (or is incredible slow). Tested in Rhino 1.7.14

var aregex = /^[A-Z]+\.([A-Z]+)*$/;
aregex.test('ABCDEFV.HSAKSHKASHSKAHSKAHSKJAHSQWWQIUEIUWEYWIEI@ABCDEFV.COM')

Also the regexp code is non-interruptible. Please add if (Thread.interrupted()) ... to the regexp evaluation loop

[p-bakker]

Hi,

Its unfortunate that you ran into this. Tested this in Chrome and also quite slow there. Think this is just a limitation of many regex implementations out there, see https://v8.dev/blog/non-backtracking-regexp for an explanation of the problem/challenge.

As for your request for adding the if (Thread.interrupted()) call: if you can provide a PR for it, it can be looked at

[tuchida]

https://github.com/makenowjust-labs/recheck
I have not tried it, but it seems that time-consuming RegExp can be detected by such a library.

[blutorange]

In general, JavaScript regexp are powerful enough that there will always be some that are very slow, even in browsers. For example:

regexp: (.*){1,32000}[bc]
input: aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa

(If you try this in Chrome dev tools, be prepared to kill the browser tab)

We are currently still using Rhino to run JavaScript regexps, in order to perform server validation of some client side browser code.

Until now we started a separate thread and used the deprecated Thread#stop method to kill the thread if it did not complete within a certain timeout (as that is the only way to kill unresponsive threads).

Somewhere between Java 17 and 21, Thead#stop was changed not to work anymore and just throw a UnsupportedOperationException.

As such, a way to interrupt long running regexp would definitely be great. I'll try and clone this repo locally to see if the check for Thread.interrupted would work.