Perhaps they won't violate the confession, but there are some State laws that say they must in certain cases. I suppose enforcement might be tough, but I don't see where I would lose much sleep if I heard a priest turned in a child molester. Why should a creep get to unload his/her guilt at the expense of someone else? I guess that's why I prefer the Bible as the final Word rather than the religions of the world.
This link Discussion about confession confidentiality is just one of many available to let you know that some religious practices/covenants may not be given full deference in all cases.
This does not apply to Catholic priests. Under no circumstances are they permitted to share anything heard in the confessional with any third party, even if to protect others or themselves.
It is likely that a child molester who confesses a crime in the confessional will not be given absolution unless said molester turns himself in to the police. Regardless, the priest is still not permitted to share the information with the authorities.
The seal of confession is inviolate.