Parallel cross-compiler installs [Was: want a,m,s,w,x whenbuilding gcc-3.1]

[Ralf Corsepius <corsepiu at faw dot uni-ulm dot de>]

Am Die, 2002-04-30 um 02.25 schrieb Richard Henderson:
> On Sun, Apr 28, 2002 at 08:25:59AM +0200, Ralf Corsepius wrote:
> > 3.1 Using the same prefix for gcc as for binutils.
> > No problems, building finishes correctly.
> 
> This is correct.
> 
> > 3.2 Using a different prefix for gcc as for binutils:
> 
> This isn't.  What you are trying to do is at odds with 
> how gcc-as-a-cross-compiler expects to work.
> 
> I.e. working as designed and not a bug per-se.
Hmm, I haven't been aware about this restriction. 

Esp. it was a surprise to me having to notice AS_FOR_TARGET,
LD_FOR_TARGET and --with-as, --with-as to be non-functional for
cross-compilers.

Anyway, this raises another question: 
How to deal with c++-headers for parallel installs of cross-toolchains
for different combinations of targets and versions of libstdc++/gcc.

Example: parallel installs (using the same prefix) of
sparc-rtems/gcc-3.0.4
i386-rtems/gcc-3.1

AFAIU, this would require to install the c++ headers do custom locations
to prevent different gcc's c++/libstdc++ headers from getting mixed.

Using different prefixes would probably work, but would hardly be wanted
by RTEMS, so using --with-gxx-include-dir seems to be an option.

Which setting for --with-gxx-include-dir would be recommended?
--with-gxx-include-dir=$(prefix)/include/g++31-v3
--with-gxx-include-dir=$(exec_prefix)/include

Ralf