Warning #225-D - function declared implicitly

Hello,

In a simple test program

#include "DSP281x_Device.h"
void main() {
    InitSysCtrl();
    while(1){
    ;
    }
}

that I wrote for the TMS320F2812 that calls the function InitSysCtrl(), the warning
#225-D - function declared implicitly
appears, caused by the command InitSysCtrl(). InitSysCtrl() is defined in the file DSP281x_SysCtrl.c. This file is provided by TI for the device. I have added it to the project folder.

Despite this, more code that is added to main() works.

I have tried adding the line

#include "DSP281x_SysCtrl.c"

but then a bunch of errors appear:

#10010 errors encountered during linking; "test.out" not built
#10056 symbol "_CsmUnlock" redefined: first defined in "./main.obj"
#10056 symbol "_DisableDog" redefined: first defined in "./main.obj"
#10056 symbol "_InitFlash" redefined: first defined in "./main.obj"
#10056 symbol "_InitPeripheralClocks" redefined: first defined in
#10056 symbol "_InitPll" redefined: first defined in "./main.obj"
#10056 symbol "_InitSysCtrl" redefined: first defined in "./main.obj"
#10056 symbol "_KickDog" redefined: first defined in "./main.obj"

So apparently the file DSP281x_SysCtrl.c is already found without the explicit include command. But then how does one declare the function properly?

Regards,

Adrian