I want several versions of g++ and libg++ to co-exist.
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   I recommend against using the `-V' flag to make multiple versions of
gcc/g++ co-exist, unless they are different minor releases that can use
the same compiled version of libg++.  The reason is that all these
versions will try to use the same libg++ version, which usually will
not work.

   Instead, use the `--prefix' flag when configuring gcc.  Use a
different value of `--prefix' for each gcc version.  Use the same value
of `--prefix' when configuring libg++.  You can then have any number of
co-existing gcc/libg++ pairs.  Symbolic links can be used so that users
don't need to put all these different directories on their paths.

   One possible system to use is to set `--prefix' to
`/usr/local/gcc-2.x.y' for version 2.x.y of gcc, and to link whichever
version of gcc you wish to be the default into `/usr/local/bin/gcc' and
`/usr/local/bin/g++'.