Error: foo.file on line wxy
    Error: foo.file on line xyz
    .
    .
    .

function abc_1234 (...)
    .
    .
    .


    endfunction

    function def_442 ()
    .
    .
    .
   //Following line number is  WXY
    assign Z ==== X;

    endfunction


    function ghi(...)
    .
    .
    .


  //Following line number is  XYZ
    assign X = X;
    endfunction

   .
   .
   .

# look for function definitions and record the function name
# in the func_name variable
/function [[:alpha:]][[:alnum:]]*[[:blank:]]*([^)]*)/ {
  func_name = substr($2, 1, index($2, "(")-1);
}

# when we reach the target line number, print out the current
# value of func_name
NR == target {
  print func_name
}