Cabal semantics for multiple compilers

[Yitzchak Gale]

In anticipation of the upcoming release of the
Mac OS X Tiger installer for GHC 6.8.2, the
following questions arise:

I currently have GHC 6.8.2 installed via MacPorts
in /opt/local. When I use Cabal to install packages
manually, they install into /usr/local. I think that
is the correct behavior - if that package someday
becomes a supported port, the port will install
into /opt/local and I don't want to conflict with that.
In general, I leave the entire /opt/local tree under
the control of the automated port system.

Now, what will happen when I install a second
copy of GHC 6.8.2 into /usr/local using the installer?

First question: What will --with-compiler=ghc-6.8.2
now mean if I forget to specify the full path? Will Cabal
do something reasonable and not get confused?
(Will it not get confused if I do remember to specify
the full path?)

Second question: When I install packages, both copies
of GHC 6.8.2 will want to install them into /usr/local. Cabal
uses directory names like "ghc-6.8.2" to keep installations
for different compilers separate from each other. But what
if both of the compilers are called "ghc-6.8.2"?

Thanks,
Yitz