R help - Nov 2001 - choosing g/g++ compiler executable in R CMD SHLIB

Dear People,

After considerable effort, I managed to install gcc-3.0 on my Debian
system. However, Debian keeps gcc-2.95 around as the default compiler, and
gcc, g++ point to the 2.95 version. The 3.0 versions need to be explicitly
invoked as gcc-3.0, g++-3.0 etc. How can I get R CMD SHLIB to invoke
gcc-3.0 instead of gcc and g++-3.0 instead of g++? I would like this to be
done by default but only for R. That is, I would like everything except R
CMD SHLIB to call the 2.95 versions by default, but have R CMD SHLIB to
call the 3.0 versions by default.

I didn't see this issue addressed in "Writing R Extensions". Is
there a
way to do this?

                                  Sincerely, Faheem Mitha.

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On Sat, 17 Nov 2001, Faheem Mitha wrote:
>
> Dear People,
>
> After considerable effort, I managed to install gcc-3.0 on my Debian
> system. However, Debian keeps gcc-2.95 around as the default compiler, and
> gcc, g++ point to the 2.95 version. The 3.0 versions need to be explicitly
> invoked as gcc-3.0, g++-3.0 etc. How can I get R CMD SHLIB to invoke
> gcc-3.0 instead of gcc and g++-3.0 instead of g++? I would like this to be
> done by default but only for R. That is, I would like everything except R
> CMD SHLIB to call the 2.95 versions by default, but have R CMD SHLIB to
> call the 3.0 versions by default.
>
> I didn't see this issue addressed in "Writing R Extensions".
Is there a
> way to do this?
It's nothing to do with "Writing R Extensions": it is an
installation
issue.  If you build R with CC=gcc-3.0, CXX=g++-3.0 then these will be
recorded in RHOME/etc/Makeconf and used by R CMD SHLIB (at least, that
works for me).  I suspect manually editing that file will do what you
want.

However, a warning.  FLIBS is also set at build time (configure time),
and the correct specification for gcc 3.0.x is not the same as for gcc
2.95.x.   I think it would be a lot safer to rebuild R under your favoured
compilers.

The FLIBS problem arises if compilers are updated so g77 refers to 3.0.x,
BTW.  It may not be relevant is you only want to compile C and C++.

-- 
Brian D. Ripley,                  ripley at stats.ox.ac.uk
Professor of Applied Statistics,  http://www.stats.ox.ac.uk/~ripley/
University of Oxford,             Tel:  +44 1865 272861 (self)
1 South Parks Road,                     +44 1865 272860 (secr)
Oxford OX1 3TG, UK                Fax:  +44 1865 272595

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"Faheem" == Faheem Mitha <faheem at email.unc.edu> writes:
  Faheem>  Dear People,
  Faheem> 
  Faheem> After considerable effort, I managed to install gcc-3.0 on my
  Faheem> Debian system. However, Debian keeps gcc-2.95 around as the default

Provided you told apt about testing or unstable, all you need is 

     $ apt-get update; apt-get install gcc-3.0

What is wrong with that?

  Faheem> compiler, and gcc, g++ point to the 2.95 version. The 3.0 versions

Depends. Some architectures (hppa) only have the 3.0* branch of gcc.

  Faheem> need to be explicitly invoked as gcc-3.0, g++-3.0 etc. How can I
  Faheem> get R CMD SHLIB to invoke gcc-3.0 instead of gcc and g++-3.0
  Faheem> instead of g++? I would like this to be done by default but only
  Faheem> for R. That is, I would like everything except R CMD SHLIB to call
  Faheem> the 2.95 versions by default, but have R CMD SHLIB to call the 3.0
  Faheem> versions by default.

One full-blown way is to re-configure and build R with these.  An easy is to
(provided you told apt about source archives)

     $ apt-get source r-base
     $ cd r-base-1.3.1
     [ go off and edit debian/rules; just uncomment my stanza about using
       gcc/g++/g77-3.0 on i386 in lines 62-68 in the r-base_1.3.1-5 package
       currently in http://incoming.debian.org ] 
     [ you also want to change debian/changelog to make the revision, say,
       1.3.1-5local to protect it from being overwritten by the one from the
       archive ] 
     $ fakeroot dpkg-buildpackage
     $ su -c "dpkg -i ../r-base_1.3.1-5local_i386.deb"

and you should be all set.

A more hackish way is to simply define CC=gcc-3.0, CXX=g++-3.0, FC=g77-3.0
and to export those. You will end up mixing gcc-2.95 and gcc-3.0, not sure if
that works.
 
  Faheem> I didn't see this issue addressed in "Writing R
Extensions". Is
  Faheem> there a way to do this?

It is way too distribution-specific to be covered there, and almost too
specific for this list.

Hope this helps. Bug me privately if you need more help.

Cheers, Dirk

-- 
Better to have an approximate answer to the right question 
than a precise answer to the wrong question. -- John Tukey
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