Around line 527 of configure.ac in R-2.1.1 appears the following:
darwin*)
## MacOS 10.3 and 10.4 do
AM_CONDITIONAL(BUILD_DLFCN_DARWIN, false)
## SI says we want '-lcc_dynamic' on Darwin, although currently
## http://developer.apple.com /documentation/MacOSX/ has nothing
## official.
AC_CHECK_LIB(cc_dynamic, main)
;;
*)
AM_CONDITIONAL(BUILD_DLFCN_DARWIN, false)
AC_CHECK_LIB(dl, dlopen)
;;
The purpose of this is to add -lcc_dynamic to the link options when
linking Fortran code built with an FSF g77 with C libraries built
with Apple's gcc-3.xx compilers. (see http://www.astro.gla.ac.uk/
users/norman/note/2004/restFP/ for the full story.).
The fixed worked because /usr/lib/libcc_dynamic.dylib was a symlink
to /usr/lib/gcc/powerpc-apple-darwin/$VERSION/libgcc.a.
I write 'was' because as of gcc-4.0 on Tiger (10.4) this has
changed. gcc-4.0 is the default compiler for Tiger, and it does not
have the symlink. This is for the very good reason that it would not
work. I have tried it. If gcc_select is used to changed the default
compiler, the symlink is created, but it is destroyed again if the
default is set back to 4.0.
As far as I can see at this point, there are two ways to build R on
MacOS X 10.4 Tiger:
1. use gcc-3.3 with g77 and ensure that -lcc_dynamic is in the link
options.
or
2. use gcc-4.0 with gfortran in which case -lcc_dynamic is not
required and the configure.ac test above is redundant.
AFAIK gcc-4.0 cannot be used with g77.
Apple have been adding 'APPLE LOCAL' mods to gfortran and it can now
be built from current Apple sources simply by adding f95 to the --
enable-languages on line 102 of the build_gcc script. I suspect that
in the not too distant future gfortran will become part of the Xcode
packages.
Bill Northcott
