title: Compiler error message line / column number reporting with Unicode
body: <p>Is there a standard/common way to give compiler-style error messages that point to a line and column when the input is in a Unicode format?</p>
  
  <p>For example, a very common compiler error messages format is:
  "filename:line_number:column_number: error message", e.g.:</p>
  
  <ul>
  <li>(From GCC): <code>bad.c:1:10: syntax error, unexpected STRING</code></li>
  <li>(From a custom tool) <code>input.dat:45:3: expected String_Literal, found ';'</code>,</li>
  </ul>
  
  <p>This is unambiguous when the input is a fixed 8-bit encoding, such as ISO-8859-1. But when the input is Unicode (UTF-8, UTF-16, etc), what does (or should) "column" mean in this case? Which byte? Which code-point? Which grapheme? Is there any tool that sets a precedent choosing one or the other?</p>