g++ on freebsd

I want to create 3d platonic solids using gnuplot. A source code can be found at

http://math.lbl.gov/voro++/download/

However, compilation fails with

olivares@coolermaster:~/tmp/kerTeX/Documents/voro++-0.4.6 $ make all
make -C src
g++  -Wall -ansi -pedantic -O3 -c cell.cc -o cell.o
make[1]: exec(g++) failed (No such file or directory)
*** Error code 1

Stop.
make[1]: stopped in /usr/home/olivares/tmp/kerTeX/Documents/voro++-0.4.6/src
*** Error code 1

Stop.
make: stopped in /usr/home/olivares/tmp/kerTeX/Documents/voro++-0.4.6
olivares@coolermaster:~/tmp/kerTeX/Documents/voro++-0.4.6 $ gmake all
gmake -C src
gmake[1]: Entering directory
'/usr/home/olivares/tmp/kerTeX/Documents/voro++-0.4.6/src'
g++ -Wall -ansi -pedantic -O3 -c cell.cc
gmake[1]: g++: No such file or directory
gmake[1]: *** [Makefile:31: cell.o] Error 127
gmake[1]: Leaving directory
'/usr/home/olivares/tmp/kerTeX/Documents/voro++-0.4.6/src'
gmake: *** [Makefile:14: all] Error 2


How can I make it work with clang on FreeBSD?

Thanks & Best Regards,

Antonio