tree 8c88b5506b49798e1ddd50586db8f66d031f5474
parent 22f1521122402bee88b58a463af58b5ab865dc3f
author Arne Becker <arne_becker@genua.de> 1625601364 +0200
committer Nick Wellnhofer <wellnhofer@aevum.de> 1625601565 +0200

Patch to forbid epsilon-reduction of final states

When building the internal representation of a regexp, it is possible
that a lot of empty transitions are created. Therefore there is a step
to reduce them in the function xmlFAEliminateSimpleEpsilonTransitions.

There is an error there for this case:

* State 1 has a transition with an atom (in this case "a") to state 2.
* State 2 is final and has an epsilon transition to state 1.

After reduction it looked like:
* State 1 has a transition with an atom (in this case "a") to itself
  and is final.

In other words, the empty string is accepted when it shouldn't be.

The attached patch skips the reduction step for final states.
An alternative would be to insert or increment counters when reducing a
final state, but this seemed error prone and unnecessary, since there
aren't that many final states.

Fixes #282