I you are trying to compile software on a new system, and you get this error:
checking how to run the C++ preprocessor... /lib/cpp
configure: error: C++ preprocessor "/lib/cpp" fails sanity check
See `config.log' for more details.
Then you need to install the gcc-c++ compiler:
# yum install gcc-c++
# sudo apt-get install gcc-c++
Installing gpp or gcc themselves is not enough.