duplicate symbols

[chapmanemma]

There seems to be a problem compiling with the newest implementation of Xcode and the clang used by Brew.

Compilation flags:

#compiler
#cc = /usr/local/opt/llvm/bin/clang
#cc = gcc
cc = /usr/local/Cellar/llvm/11.0.1/bin/clang
#complilation flags

if FFTW uses openmp:

fftwf = -lfftw3f_omp -lfftw3f
fftwd = -lfftw3_omp -lfftw3

if FFTW used pthreads:

#fftwf = -lfftw3f_threads -lfftw3f
#fftwd = -lfftw3_threads -lfftw3

omp = -fopenmp -D_OMPTHREAD_
#omp = -Xpreprocessor -fopenmp -D_OMPTHREAD_
gsl = -lgsl -lgslcblas -lm
deb = -g

#flags = -std=c99 -Wall -O3 -march=native $(fftwd) $(fftwf) $(omp) $(gsl) -lm
#flags = -L/usr/local/opt/llvm/lib -L/usr/local/opt/fftw/lib -L/usr/local/Cellar/gsl/2.6/lib -std=c99 -Wall -O3 $(omp) $(fftwd) $(fftwf) $(gsl) -I/usr/local/opt/fftw/include -I/usr/local/opt/llvm/include -I/usr/local/Cellar/gsl/2.6/include

flags = -L/usr/local/Cellar/llvm/11.0.1/lib -L/usr/local/opt/fftw/lib -L/usr/local/Cellar/gsl/2.6/lib -std=c99 -Wall -O3 $(omp) $(fftwd) $(fftwf) $(gsl) -I/usr/local/opt/fftw/include -I/usr/local/Cellar/llvm/11.0.1/include -I/usr/local/Cellar/gsl/2.6/include -L/usr/local/Cellar/libomp/11.0.1/lib

This error is duplicated if I use the first cc option and the second flags options i.e. with the system llvm.

Error message:

duplicate symbol '_global_n_index' in:
get_densityfield.o
auxiliary.o
...
duplicate symbol '_global_L0' in:
get_densityfield.o
Input_variables.o
ld: 96 duplicate symbols for architecture x86_64

I think this is a problem with the line #include "Input_variables.h" but just commenting out one of these lines in one of the problem files isn't an option.