
456 Intermediate C Programming
FIGURE C.9: When you click Project and select Build Project, Eclipse will say “undefined
reference to addtwo” and “undefined reference to subtwo”. This should be expected because
these functions have not been implemented. Eclipse’s error message is displayed in the
Console. Eclipse also highlights the two lines that have the errors.
FIGURE C.10: To solve the build problem, we add another source file called addsub.c
and in this file we define the two functions.