compiler.whitelist and compiler installation side-effects

[René J.V. Bertin]

Hello,

What are the exact effects in terms of compiler installation when I set?

    compiler.whitelist        clang macports-clang-3.7 macports-clang-3.6 macports-clang-3.5 macports-clang-3.4
	compiler.blacklist-append macports-llvm-gcc-4.2 llvm-gcc-4.2
	compiler.blacklist-append gcc-4.2 apple-gcc-4.2 gcc-4.0
	compiler.blacklist-append macports-clang-3.1 macports-clang-3.0 macports-clang-3.2 macports-clang-3.3
	compiler.blacklist-append {clang < 500}

I have a user telling me clang 3.7 is being installed (from source, I fear) while he has port:clang-3.5 installed (or port:clang-3.6 by now), and as far as I'm concerned that is not desired behaviour.

What I'd expect is:
1- accept either of the installed compilers in the list, e.g. v3.5 if it's available
2- if none are available, install the first from the list (= give the dev a means to prefer the latest version)

1) appears not to be met. 2) doesn't go for the system compiler because clang<500 applies on the user's system.

Thanks,
R.