Undefined reference in Eclipse Kepler - c

Question

Hello Stack overflow Community,
I'm developing an C application for a Imx6 development kit from Variscite with yocto project and Eclipse Kepler. I've build an helloworld application according to the guide and written some additional code, which I now want to place in different source and include files to keep things neat and tidy. I've made the following files: uart.c, uart.h, gmttime.c and gmttime.h and included them in the src folder. Now my problem is that when i call any function from any source file that I created, I get the following compilation errors:
Description: Resource
make: *** [all] Error 2 Helloworld C/C++ Problem
make[1]: *** [all-recursive] Error 1 Helloworld C/C++ Problem
make[2]: *** [Helloworld] Error 1 Helloworld C/C++ Problem
undefined reference to `uartInit' Helloworld.c /Helloworld/src
My project files look like this:
Helloworld
/includes
/usr/include
/usr/include/x86_64-linux-gnu
/usr/lib/gcc/x86_64-linux-gnu/4.6/include
/usr/lib/gcc/x86_64-linux-gnu/4.6/include-fixed
/usr/local/include
/Helloworld/src
/src
gmttime.c
gmttime.h
helloworld.c
uart.c
uart.h
makefile
makefile.am
makefile.in
#more files are in this project, which I think are not so interresting or cause or solution to this problem.
On different websites it's mentioned that I should add the directory to the project options under:Project->Properties->C/C++ General/Paths and Symbols to the Includes and Source Location Tabs. I've added /Helloworld/src and /helloworld to both tabs, but I'm still getting errors no matter what i try. I can't find any other solution to this problem, so I hope anyone has encountered the same problem and could tell me how to resolve it.
I'd be most gratefull if anyone could help me out, if anything is wrong with my question or more information is required, just ask.
Regards,
Edit:
uart_init's function prototype is declared in uart.h and the function excists in uart.c, both files are user made, so no library inclusions are required.
I have uart.h included in my helloworld.c file, just as i would include it in any normal c application. The code highlighting does not show any errors at #include "uart.h", although it shows a red underline at each function from uart.h, complaining; undefined reference when i hover my mouse over the function.
I can open a function declaration and then eclipse takes me to uart.c and shows the function's source code. It seems that the compiler does not include additional .c and .h files except those originally made by the Hello World ANSI C project in it's build, eventhough it refers correctly when i use F3 "Open decleration" on a function. I don't know if the make file automaticly includes the new files in a build or my project source location set under Project->Properties->C/C++ General/Paths and Symbols is incorrect.

Answer 1

The solution was quite simple, I had to include uart.c to the project_SOURCES in the makefile.am. I've been searching in the wrong direction all along, as I thought the problem was caused by a wrong or unset project configuration. The solutions I found on the web were all resolved by setting the Includes and source location folders under C/C++ General settings and thus I thought the solution was in the project configurations. With a little bit of trial and error I finally found the solution.