Build with object files without sources

Hi,
i try to build some "libraries" having only the .h and .o files.
I add the .h in the IDE and the .o in the project settings builder in the section C/C++ Build → Settings → Tool Settings → C Linker → Miscellaneous → Other objects.
But when i build i got error in linker operations "undefined reference to 'mycustomFunction'.

I do this operation with other eclipse enviroment and i'havent any problem.

I'm missing something??

Thanks
S.