title: Find sourcecode line which causes undefined reference error
body: <p>sooner or later when programming in C/C++ everyone will face the "undefined reference error". </p>
  
  <p>Often this is caused by missing libraries and most of those errors are fixed within seconds by linking against the missing libraries.
  However, when for instance one uses templates with seperate files for declaration and implementation, one may get undefined reference caused by "unintended" template instantiation. Unfortunately, all information we now get is an instance of "undefined reference error", without possible hints for the cause such as line numbers of the callers, etc.</p>
  
  <p>What I am curious about: 
  Is there an easy way to spot the actual sourcecode line(s) that calls the function/the template causing the undefined reference error?</p>