include same file twice

Hi,
I'm using functions from one file in two different files, so i include this file in both of them.
I run the functions in those files from another file, so i include both of them in that file.

Example:Files- file_general_func, file1, file2, file_main.
file1: #include "file_general_func"
file2: #include "file_general_func"
file_main: #include "file1", #include "file2"
After build this script i gets "WARNING: already included file:"

Removing the #include "file_general_func" from both files and include it only in "file_main" worked for a while, but after some changes I got error or "undefined function"

How can i solve it?

Thanks,
Shany