.o isnt working right...

Im making this code for mecanum driving, but everytime i go to build and compile, it gives me an error saying that this piece of code isnt defined in it’s .o file. So my question is: How do i fix it!?

Do you have your functions prototyped?


//prototype
void DoDrive(void);

//function code
void DoDrive(void){

pwm01 = 127;

}

What piece of code?