Fresh $prefix required to avoid any upgrade trouble?

[Loren James Rittle <rittle at latour dot rsch dot comm dot mot dot com>]

Do we need to inform people installing gcc 3.0 that they should use a
fresh $prefix to avoid any possible trouble?

For background, we current say this in gcc/doc/install.texi:

> Please note that GCC does not support @samp{make uninstall} and probably
> won't do so in the near future as this would open a can of worms. Instead, 
> we suggest that you install GCC into a directory of its own and simply
> remove that directory when you do not need that specific version of GCC
> any longer.

I install the 3.0 branch into a tree that already had a similar gcc
installation (this usage doesn't appear to be against the suggestion
given above).  I normally don't delete the tree at $prefix before
installation since it contains the installation of binutils that I
test with gcc (and it doesn't get updated as frequently as the daily
gcc bootstrap).

While playing with a configuration patch I am about to publicly post,
I found that until I deleted (at the very least):

./alpha-unknown-freebsd4.2/include/g++-v3/bits/c++config.h
./include/g++-v3/bits/c++config.h

the installed compiler was getting an old configuration file.  And it
caused mayhem.  I know this has come up before and I knew how to fix
this problem by cleaning out all the old header files.  Most people
that install gcc won't know about this detail.

Will this affect anyone that is upgrading from 2.95.X (that maybe had
an after-market official snapshot of libstdc++-v3 installed with it)?

If so, then we need to document it or else prepare for a possible
flood of bug reports...

Regards,
Loren