title: Debugging ANTLR4 grammar
body: <p>I'm a n00b to ANTLR and going big by trying to get an ASN.1 parser running in ANTLR4.  I am presently at the stage where I'm passing in an input file to grun and seeing errors like "line 1:12029 no viable alternative at input ..."</p>
  
  <p>I'm trying to relate this back to some problem with my rules but locating the offending input by character count is a challenge.  Is it normal for an ANTLR parser to see the input as a single line, or am I failing to recognize EOLs because of a rule problem (I'm on an OSX system)?  If it is normal to see the input as one long line, can someone recommend a tool for locating a given character position in a file?</p>