Hello!

  In Emacs 21.3 the etags utility seg. faults. To recreate the error you 
need to do the following steps:

    * create a file named t.erl and add the following two lines:

        -module(t).
        -define().

    * Then we execute the etags command:

        etags -o TAGS t.erl

This results in a segfault and a core dumped. The reason to the segfault 
was that in the routine erlang_attribute() it calculates the length of 
the string between ( and ) to be -1. The if statement only checks if the 
value isn't 0 to continue working with the string, while it should only 
continue if its a possitive value greather then 0.

The patch attached should correct this problem.

Cheers,
Daniel