[Rd] build 32-bit R on x86_64?

[Vinh Nguyen]

Dear R-Devel,

I'm using Ubuntu on an x86_64 machine and would like to have both the
32-bit and 64-bit versions of R built from source.  By default,
following the usual build procedures yields 64 bit R.  Looking at
[these](http://cran.r-project.org/doc/manuals/R-admin.html#Sub_002darchitectures),
I thought I could build 32-bit R by executing

r_arch=32 ./configure

and building R like usual (make).  However, after seeing this error message,

/usr/bin/install: cannot create regular file
`../../include/32/Rconfig.h': No such file or directory

I realize I am misunderstanding the instructions.  Could someone
please clarify how I could go about compiling both 32-bit and 64-bit
versions of R on my Linux machine?  Thank you!

-- Vinh