comment out c_interface to avoid need for std=f2018

src/Makefile.2

@@ -98,10 +98,10 @@ library_interface.o : ../library_interface.F90 \
 	types.o wannier90_readwrite.o wannier90_types.o wannierise.o
 	 $(COMPILER) $(POSTOPTS) $(FCOPTS) -c ../library_interface.F90
 
-c_interface.o : ../c_interface.F90 \
-	library_interface.o comms.o constants.o error_base.o io.o kmesh.o overlap.o plot.o transport.o \
-	types.o wannier90_readwrite.o wannier90_types.o wannierise.o
-	 $(COMPILER) $(POSTOPTS) $(FCOPTS) -c ../c_interface.F90
+#c_interface.o : ../c_interface.F90 \
+#	library_interface.o comms.o constants.o error_base.o io.o kmesh.o overlap.o plot.o transport.o \
+#	types.o wannier90_readwrite.o wannier90_types.o wannierise.o
+#	 $(COMPILER) $(POSTOPTS) $(FCOPTS) -c ../c_interface.F90
 
 constants.o: ../constants.F90
 	 $(COMPILER) $(POSTOPTS) $(FCOPTS) -c ../constants.F90

src/Makefile.header

@@ -1,6 +1,7 @@
 OBJS  =  constants.o io.o utility.o types.o hamiltonian.o overlap.o kmesh.o disentangle.o \
         ws_distance.o wannierise.o plot.o transport.o sitesym.o comms.o wannier90_types.o \
-        wannier90_readwrite.o readwrite.o error.o error_base.o library_interface.o c_interface.o
+        wannier90_readwrite.o readwrite.o error.o error_base.o library_interface.o 
+#c_interface.o
 
 OBJS_POST  = ws_distance.o types.o kmesh.o io.o comms.o utility.o get_oper.o constants.o \
         postw90_common.o wan_ham.o spin.o dos.o berry.o gyrotropic.o kpath.o kslice.o \