In a method of modifying code of a running computer program so as to modify the running computer program without having to restart the running computer program for changes to the running computer program to take effect, the improvement is disclosed of: (a) comparing differences in the running program's running binary code versus object code produced by compiling the running program's source code and (b) using the results of step (a), determining what values to use for symbols in said changes to the program. The compiling may be performed using either the compiler originally used to compile the running program or a different compiler. A data storage medium having instructions stored therein for a computer to perform the improved method is also disclosed.