[R-SIG-Mac] Source package installation under OSX 10.4 / R 2.10.1

[Rich FitzJohn]

Hello,

Sorry if this is the wrong place to post or if this has been addressed  
elsewhere.  I am running R 2.10.1 under OS X 10.5 (Leopard).  After  
upgrading R from 2.10 to 2.10.1, I found that no source package would  
install, with errors like:
       gcc-4.2 -arch i386 -std=gnu99 -I/Library/Frameworks/ 
R.framework...
       make: gcc-4.2: Command not found
       make: *** [bisse-eqs.o] Error 127
(similar errors for any package containing C code that I tried).  The  
Xcode that U have does not include gcc 4.2, so it is surprising to see  
it being selected.  I think I have the most recent Xcode available for  
Leopard; in any case, the only Xcode I seem to be able to get from  
apple needs OSX 10.6.

I have worked around this problem by creating a ~/.R/Makevars file  
containing
CC = gcc-4.0 -arch i386 -std=gnu99
CFLAGS = -g -O2
CXX = g++-4.0 -arch i386
CXXCPP = g++-4.0 -arch i386 -E
CXXFLAGS = -g -O2
DYLIB_LD = gcc-4.0 -arch i386 -std=gnu99
F77 = gfortran-4.0 -arch i386
FC = gfortran-4.0 -arch i386
FCFLAGS = -g -O2
MAIN_LD = gcc-4.0 -arch i386 -std=gnu99
OBJC = gcc-4.0 -arch i386
OBJCFLAGS = -g -O2
OBJCXX = g++-4.0 -arch i386
SHLIB_CXXLD = g++-4.0 -arch i386
SHLIB_FCLD = gfortran-4.0 -arch i386
SHLIB_LD = gcc-4.0 -arch i386 -std=gnu99

after which compilation succeeds (I had to both switch the version  
numbers from 4.2 to 4.0 compared with R's Makevars and drop the - 
mtune=core flag).

I have a couple of questions
(1) Will anything terrible happen as a consequence of doing this?
(2) Does this situation mean that package compilation is no longer  
supported on leopard?

Thanks,
Rich