Nios II 13 Main program function can be viewed with open Declaration, but the compile time said undefined reference to ... Why is this?

In doing 12864 IP nuclear test, wrote three files first is a timing file qc12864.v The second is QC12864.H this file mainly includes the declaration and the macro definition, the third file is qc12864.c This file contains the definition of the function. Please see http://www.cnblogs.com/yuphone/archive/2010/03/25/1694547.html for details. When I make this error and compile three files and a file, the compilation error changes. More refinement of the errors that were pointed out. Points to the implied information contained in the original error line. I had a lot of grammatical errors in my file. So undefined reference to this error is just an approximate wrong location and needs to be further searched for errors.

Nios II 13 Main program function can be viewed with open Declaration, but the compile time said undefined reference to ... Why is this?