Can't install gcc 3.2 alongside gcc 2.96 on Red Hat 7.3

[Jonathan Watt]

Claudio Bley wrote:

> A "temporary staging area" refers to the packages process -- if you intend
> to package gcc in a RPM for example, you need to install it somewhere else
> before you're going to install the real package on the system. 
> 
> With chroot you can start programs (you don't trust or which might operate
> insecurely) under a special root directory. It's like a jail because the
> programs just run below this directory and can't access the files outside.
> 
> See http://www.linux-mag.com/2002-12/chroot_01.html for an in-depth
> explanation.

That's great! I didn't realise you could do something like that. Very 
useful for the future, thanks.

> Well, the libstdc++ headers are more tightly coupled with the GCC they come
> with and that's why each gcc uses its own version by default. So, you will
> get a new c++ compiler with a shiny new c++ standard library.

I see.

> I see. You're right of course, the filesystem hierarchy standard
> (http://www.pathname.com/fhs/) specifies that /usr/local should only be used
> for site specific software and no RPM from Redhat will write anything into
> this hierarchy (unless it's buggy).

Thanks for that link, I was thinking I should find some docs to learn 
about how the filesystem is structured. That looks ideal.

>>>Try 'cat /dev/null | gcc -v -E -':
>>
>>What is this doing? 
> 
> 
> It just preprocesses (the -E switch) an empty source file being verbose
> about its operation (the -v switch) as you already found out. 
> 
> 
>>What should it tell me? 
> 
> 
> The part I quoted just shows where the gcc that came with my Debian
> distribution searches for header files by default. Redhat's default gcc
> should behave the same. It just demonstrates that by default
> /usr/local/include is also searched for header files.

I see, do you know why is it that when I use -v for an empty file I get 
the following search paths:

#include <...> search starts here:
  /usr/local/include
  /home/jwatt/gcc/include
  /home/jwatt/gcc/lib/gcc-lib/i686-pc-linux-gnu/3.2.3/include
  /usr/include

but when I use -v on an actual C++ file I get more search paths, 
specifically the following:

#include <...> search starts here:
  /home/jwatt/gcc/include/c++/3.2.3
  /home/jwatt/gcc/include/c++/3.2.3/i686-pc-linux-gnu
  /home/jwatt/gcc/include/c++/3.2.3/backward
  /usr/local/include
  /home/jwatt/gcc/include
  /home/jwatt/gcc/lib/gcc-lib/i686-pc-linux-gnu/3.2.3/include
  /usr/include

> Actually, it means to read standard input, i.e. the output of `cat /dev/null'.

Ah, that makes more sense.

>>Can I add a more up-to-date version of the standard C++ library to gcc 
>>if I install gcc under my $HOME directory? Which version normally goes 
>>with gcc 3.2.3? Can anyone tell me how I would get my install of gcc to 
>>use this library automatically?
> 
> 
> At first, you may use different C++ standard libraries with GCC. GCC by
> default ships with its own incarnation called libstdc++. With gcc 3.2.3 you
> get the GNU Standard C++ Library v3 (-3.2.x) which BTW does not work with
> any version prior to GCC 3.0.
> 
> There's also a commercial implementaion of the C++ STL from Dinkumware for
> GCC and there's STLport (www.stlport.org) which is available for free. 
> 
> STLport should also work with gcc 2.96 and provides more backward
> compatibility and obsolete features (e.g. vector iterators are implemented
> as pointers -- yes, this is not assured by the C++ standard, but some
> (broken) programs do rely on that).
> 
> The bottom line is that you can definitely install GCC 3.2 and expect that
> you get a more up-to-date version of the standard C++ library with it and
> there's no need to specify any special options.
> 
> Cheers.

I think I will stick with the library that comes with gcc 3.2.3 for the 
moment.

Thanks for all that Claudio.

Jonathan