As far as I'm aware a copy of the initial environment from emerge's parent isn't saved prior to being mangled by make.defaults. This makes it impossible to be certain whether a variable like USE or CFLAGS was set interactively (or at least passed to emerge). It would be nice if portage could create an associative array with the key/value pairs of the original environment prior to sourcing /etc/portage/bashrc so that it's possible to directly test for them instead of having to define special variables like `CFLAGS_OVERRIDE' and test for those. Is there a more reasonable approach that works now? This should be a simple feature. Reproducible: Always