Hello, gcc-help. I experienced "undefined reference to template function ." when I am compiling my program with gcc 4.1.2. Almost everyone says that's because template functions weren't be implemented in the same unit where they are prototyped. (I used .cpp file for implementation and .h file for declaration). But, It works if I use gcc 3.4.6 compiler without any change of options. Why is this happening?... I am working with my customer, I can't make them understand the common rule for using template because it works on gcc 3.4.6. Can you explain this situation to me? (Something like it is changed after 4.0 or you have any options to avoid this.) Please, help me. Thank you. Her, Il Technology Consulting Technology Service Korea TEL : +82-2-2199-4475 Mobile : +82-10-4765-5597 il.her@xxxxxx