FC_VALUE_AFTER_EXIT() resulting in "unknown"
These are the errors that cause it to fail even when it's not failing for the reason tested:
Going to split missing-prototype part to a new ticket. It's the part that affects all branches. Once it's fixed, there should be no issue for S2_6 or S3_0.
old-style-definition warnings are enabled only in S3_1 and later.
FC_VALUE_AFTER_EXIT() usually results in "unknown" instead of "no". That's not very serious as "unknown" is handled as "no", and it's getting "yes" when it should.