Compile Question with _cpumask_t Error

Hello,

I am running 9.0-CURRENT FreeBSD amd64 from Tue Jul 18 16:18:20 PDT 2011. I 
am trying to compile an R-project package that is using g++45 to compile and 
it fails due (apparently) to an error with _cpumask_t as noted below. I have 
seen some discussions about this that I do not completely understand 
(http://lists.freebsd.org/pipermail/freebsd-current/2011-June/025092.html). 
Essentially, I am wondering what the work-around is for this.

Thanks in advance, Aric
----------------------------
freeenv# R CMD INSTALL ./RBGL_1.29.0.tar
* installing to library '/usr/local/lib/R/library'
* installing source package 'RBGL' ...
untarring boost include tree...
** libs
g++45 -I/usr/local/lib/R/include     -IboostIncl -fpic  -O2 -pipe 
-Wl,-rpath=/usr/local/lib/gcc45 -fno-strict-aliasing -c bbc.cpp -o bbc.o
In file included from 
/usr/local/lib/gcc45/include/c++/backward/hash_set:60:0,
                  from boostIncl/boost/graph/adjacency_list.hpp:25,
                  from RBGL.hpp:26,
                  from bbc.cpp:1:
/usr/local/lib/gcc45/include/c++/backward/backward_warning.h:28:2: 
warning: #warning This file includes at least one deprecated or 
antiquated header which may be removed without further notice at a 
future date. Please use a non-deprecated interface with equivalent 
functionality instead. For a listing of replacement headers and 
interfaces, consult the file backward_warning.h. To disable this
warning use -Wno-deprecated.
In file included from 
/usr/local/lib/gcc45/gcc/x86_64-portbld-freebsd9.0/4.5.4/include-
fixed/unistd.h:46:0,
                  from 
/usr/local/lib/gcc45/include/c+
+//x86_64-portbld-freebsd9.0/bits/gthr-default.h:42, from 
/usr/local/lib/gcc45/include/c+
+//x86_64-portbld-freebsd9.0/bits/gthr.h:162, from 
/usr/local/lib/gcc45/include/c++/ext/atomicity.h:34,
                  from 
/usr/local/lib/gcc45/include/c++/bits/ios_base.h:41,
                  from /usr/local/lib/gcc45/include/c++/ios:43,
                  from /usr/local/lib/gcc45/include/c++/ostream:40,
                  from /usr/local/lib/gcc45/include/c++/iostream:40,
                  from RBGL.hpp:7,
                  from bbc.cpp:1:
/usr/local/lib/gcc45/gcc/x86_64-portbld-freebsd9.0/4.5.4/include-
fixed/sys/types.h:111:9: 
error: '__cpumask_t' does not name a type
*** Error code 1

Stop in /tmp/Rtmpd52RCc/R.INSTALL7fb40f0b/RBGL/src.
ERROR: compilation failed for package 'RBGL'
* removing '/usr/local/lib/R/library/RBGL'


freeenv# pkg_info | grep boost
boost-jam-1.45.0    Build tool from the boost.org
boost-libs-1.45.0_1 Free portable C++ libraries (without Boost.Python)
boost-python-libs-1.45.0_1 Framework for interfacing Python and C++