"Arithmetic exception" with modulus operator '%'

["jounijl@yahoo.co.uk" <jounijl@yahoo.co.uk>]

As in the headline. Program stops and prints "Arithmetic exception" at 
the line where the modulus operator '%' is.

I'm compiling in Alpine linux with clang installed from apk:s:

clang -c test.c
clang -o test test.o

The code is:

----- snip -----
         unsigned int unum  = 0;
         unsigned int umod  = 0;
         unsigned int ures  = 0;
         ures = unum % umod; // <-- this one
----- /snip -----

The variables have some values other than 0.

The environment is:
The Alpine Linux is installed in Oracle Virtualbox in FreeBSD 12, 64-bit 
Intel.

$ uname -a
Linux localhost 4.14.89-0-vanilla #1-Alpine SMP Tue Dec 18 16:10:10 UTC 
2018 x86_64 GNU/Linux

$ clang --version
Alpine clang version 5.0.1 (tags/RELEASE_501/final) (based on LLVM 5.0.1)

What does this? Do I need to include some library?

w.b.reg., Jouni