I think it's controlled by *COMPILE-FILE-FAILURE-BEHAVIOUR* and *COMPILE-FILE-WARNINGS-BEHAVIOUR* both taking as value one of :WARN, :ERROR or :IGNORE.
Robert Goldman writes:
What is the proper way to make ASDF fail on ANY warning (including STYLE-WARNINGs)? I thought I knew how to do this, but I'm having trouble making it work, possible because of the DEFERRED-WARNINGS.
Thx, r