[csw-maintainers] Reasons for gcc to have a separate prefix

[Peter FELECAN]

Maciej Bliziński <maciej at opencsw.org> writes:

> However, alternatives are not a viable solution for the buildfarm. We
> all work on the same hosts and we need to make it possible to build
> with gccN and gcc(N+1) at the same time.  You can't have buildfarm
> admins flip symlink every time a maintainer wants to switch between
> e.g. gcc-3 and gcc-4.

Just a follow up on my own advice to look how Debian does it...

* How Debian manages multiple versions of GCC
  Useful information is found, on an installed system, in
  /usr/share/doc/gcc/README.Debian
** Default version
   Each Debian release has a default set of compilers issued by a
   generic source package called gcc-defaults
   (http://ftp.de.debian.org/debian/pool/main/g/gcc-defaults/gcc-defaults_1.107.tar.gz)
   The generated packages supply a symbolic link toward the default
   driver, e.g., for the C compiler, there is /usr/bin/gcc which point
   toward /usr/bin/gcc-4.6
   Note that you find the README.Debian in the above mentioned source
   package.
** Alternatives
   Alternatives are used at a higher level, e.g., /usr/bin/cc is an
   generic name, having cc as the alternative name with a possible
   alternative path of /usr/bin/gcc
** Using a non default version
   When compiling with a non-default version of the compiler you must
   explicitly specify the one that you wish to use, e.g.
   CC=gcc-4.1 ./configure <configure options>
** File-system organization
   each version of GCC provides its specific components installed in
   corresponding directories; e.g., /usr/lib/gcc/i486-linux-gnu/4.3;
   this organization is directly supported by the GCC build system,
   i.e., it doesn't need modifications
** Run-time shared libraries
   The run-time shared libraries conforms with the shared libraries
   policy and thus supports multiple releases installed simultaneously
   with one default version.

* How Open CSW should manage multiple versions of GCC
  I don't discuss here the integration of Sun Studio in the
  alternatives system but that would be a nice feature.
** Default version
   the most recent version of GCC is considered as the default one and
   provides the /usr/bin/gcc symbolic link
** Alternatives
   Use the cc as the generic name
** Using a non default version
   Same as Debian
** File-system organization
   Similar with that of Debian
** Run-time shared libraries
   Similar with that of Debian

-- 
Peter