title: Fortran compile error -- In function X undefined reference to Y where function is public and use is implemented
body: <p>As stated in the title, when I compile an executable binary from many fortran object files, I experience an error in <code>W.f90</code> and <code>X.f90</code> of the type:</p>
  
  <p><code>In function 'X_mp_average_list_add_': X.f90:(.text+0x2fa): undefined reference to 'Y_mp_vlist_var_new_'</code></p>
  
  <p>I saw in a response to a previous, similar question (avoiding necromancy) that this issue was likely a result of either not declaring <code>vlist_var_new</code> as <code>PUBLIC</code> in <code>Y.f90</code> or <code>W|X.f90</code> files did not correctly implement <code>USE: Y, only vlist_var_new</code>. However, these are correctly implemented in the Fortran files and the compile worked previously, since such time the files have not been changed. </p>
  
  <p>Can someone indicate other potential sources for these errors? </p>
  
  <p>For reference, I'm using the intel fortran compiler v5.1.3.223</p>