Expressions with the * operator runs infinitely

[jack0lantern]

On this page:
http://docs.oracle.com/javase/tutorial/essential/concurrency/procthread.html

I searched s* and it appears to enter an infinite loop in v 1.8. Eventually, the page crashes.

[gsingh93]

Whoa... well this is bad. I'm not sure what the proper fix is for this or when I'll get time to look into it, but thanks for the report.

[ComFreek]

I can confirm this.

Please use s+ (at least one s) instead. It is more efficient than s* (0 or more s) because the latter even matches empty strings all over the page.

[gsingh93]

Maybe we should disallow searching any two character regex where the second character is a '', or the one character regex where '' is the only character. Does that cover all of the bad cases or are there other cases we're missing?

[ComFreek]

Some test cases performed on the website mentioned in the first comment:

1 works:         .*
2 works:         ..........
3 works:         .*.*.*.*.*.*.*
4 works:         (.+)*
5 fails:            s*

It seems that some optimization is done in case 1 as opposed to case 5.

So indeed, it might be a good idea to disallow a regex consisting of any character followed by * only.
Or shall we rather add general hint/warning that usage of '+' is encouraged contrary to '*'

PS: You can escape asterisks and other Markdown syntax by a backslash: \ *