Hi,
SBCL pays careful attention to the distinction between a STYLE-WARNING (a condition strong enough to warrant returning from COMPILE-FILE with WARNINGSP set) and a compiler note (generally an optimization note, but sometimes a code deletion note or something similar), which aren't counted as warnings.
Attached is a patch to implement this. I know cmucl doesn't have this distinction; I'm unsure as to whether OpenMCL does, so I've just implemented it for SBCL; the behaviour of other lisps should be unchanged.
Cheers,
Christophe