What does the “undefined reference to varName” in C mean?

Question

I have 2 files: a.c and b.c

In a.c I am sending a signal to a function located in b.c

signal(SIGU         


        

Answer 1

An initial reaction to this would be to ask and ensure that the two object files are being linked together. This is done at the compile stage by compiling both files at the same time:

gcc -o programName a.c b.c

Or if you want to compile separately, it would be:

gcc -c a.c
gcc -c b.c
gcc -o programName a.o b.o