Add volatile and replace compound assignment
Add volatile and replace compound assignment

Co-authored-by: Chad Condon <1dd4b516b427880a711ac80c148683aebedc9bf6@users.noreply.github.com>
offa/cpputest,cpputest/cpputest,cpputest/cpputest,cpputest/cpputest,offa/cpputest,cpputest/cpputest,offa/cpputest,offa/cpputest