AFAIU, `MPI_CXX_BOOL` is supposed to [be defined](https://www.mpi-forum.org/docs/mpi-3.1/mpi31-report/node459.htm). At least Boost.MPI (a C++ MPI wrapper) relies on this macro. See https://github.com/boostorg/mpi/issues/172.
AFAIU,
MPI_CXX_BOOLis supposed to be defined. At least Boost.MPI (a C++ MPI wrapper) relies on this macro. See boostorg/mpi#172.