I am trying to install Octopus 9.1 program on MacOSX by following the instructions given here https://octopus-code.org/wiki/Manual:Installation#Configuring. I have made sure I have all the required libraries installed before installing this program. I also set some recommended environment variables beforehand, using gfortran as my fortran compiler,
export FCFLAGS="-march=athlon64 -msse2 -mfpmath=sse -malign-double -funroll-loops -O3".
The above flags are what is recommended here. Then when running the configure script I got this error:
configure: error: Could not find preprocessor usable for Fortran.
I look at the preprocessor page of that wiki and it says that the preprocessor is controlled by
FCCPP variable and for MacOS the recommended value is
clang -E -ansi. Setting this variable and running the configure script again does not get rid of the error.