Possible empty pattern encountered.

#2516   Compile-time warning

Possible empty pattern encountered.

Additional Information

This pattern can match zero characters, and therefore slow the program down.
A sub-pattern in a repetition might repeat without matching any characters.


As of Version 2 Release 4, OmniMark now allows patterns in find and translate rules to match zero characters. This is most useful for moving from one group to another in find rules without actually consuming characters. Note that if a find rule matches no characters, the next successful find rule must match at least one character. This prevents unexpected looping.

The second type of message can occur when a sub-pattern of the form (A? B* lookahead not C)+ is encountered (or a similar combination thereof).