Makefile Compiling Issue for Mixed C++ and Fortran Program - c++

Question

This is my makefile :
PROGRAM = mf2005-GPU.f
# Define the Fortran compile flags
F90FLAGS= -g -fopenmp
F90= gfortran
# Define the C compile flags
# -D_UF defines UNIX naming conventions for mixed language compilation.
CFLAGS= -D_UF -O3
CC= gcc
CPPFLAGS= -Dcpp_variable
CXX= g++
# Define GMG objects
#
GMG = r_vector.o\
solvers.o\
ccfd.o\
mf2kgmg.o\
# Define the libraries
SYSLIBS= -lc
USRLIB =
CUDA_LIB64=/cm/shared/apps/cuda40/toolkit/4.0.17/lib64/
LFLAGS = -L$(CUDA_LIB64) -lcuda -lcudart -lcusparse -lcublas -lpthread -lm -lcufft -lcurand -lnpp -lgomp
# Define all object files which make up MODFLOW
OBJECTS = \
dblas.o\
gwf2bas7.o \
de47.o \
dlapak.o\
pcg7.o \
sip7.o \
gmg7.o \
mhc7.o \
gwf2bcf7.o \
gwf2lpf7.o \
gwf2huf7.o \
gwf2rch7.o \
gwfuzfmodule.o \
gwfsfrmodule.o \
gwf2lak7.o \
gwf2sfr7.o \
gwf2uzf1.o \
gwf2gag7.o \
gwf2chd7.o \
gwf2drn7.o \
gwf2drt7.o \
gwf2ets7.o \
gwf2evt7.o \
gwf2fhb7.o \
gwf2ghb7.o \
gwf2hfb7.o \
gwf2ibs7.o \
gwf2res7.o \
gwf2riv7.o \
gwf2str7.o \
gwf2sub7.o \
gwf2swt7.o \
gwf2wel7.o \
hufutl7.o \
obs2bas7.o \
obs2drn7.o \
obs2ghb7.o \
obs2riv7.o \
obs2chd7.o \
obs2str7.o \
parutl7.o \
gwf2mnw17.o \
gwf2mnw27.o \
gwf2mnw2i7.o \
utl7.o \
lmt7.o \
gwf2hydmod7.o \
upcg7.o \
upcgc.o \
upcg7lanczos.o \
upcg7polya.o \
upcg7polyu.o \
mf2005-GPU.o \
# Define Task Function
all: mf2005-GPU
# Define what mf2005
mf2005-GPU: $(OBJECTS) $(GMG)
-$(F90) $(F90FLAGS) -o mf2005-GPU $(OBJECTS) cuda_kernels.o $(GMG) $(USRLIB) $(SYSLIBS) $(LFLAGS)
# Object codes
.f.o:
$(F90) $(F90FLAGS) -c $<
.c.o:
$(CC) $(CFLAGS) -c $<
.cpp.o:
$(CXX) $(CPPFLAGS) -c $<
# end
This is how I compile cuda_kernels.cu
nvcc -c -arch sm_20 -lcuda -lcudart -lcusparse cuda_kernels.cu
This is what I get for errors
upcg7.o: In function `upcg7ar':
/home/zhangmj/MF2005_MAKE/upcg7.f:731: undefined reference to `upcgc7_init_'
upcg7.o: In function `upcg7ap':
/home/zhangmj/MF2005_MAKE/upcg7.f:1272: undefined reference to `upcgc7_'
upcg7.o: In function `upcg7da':
/home/zhangmj/MF2005_MAKE/upcg7.f:1416: undefined reference to `upcgc7_final_'
upcgc.o: In function `UPCGC7':
upcgc.cpp:(.text+0xf6a): undefined reference to `SUPCGILU0A'
collect2: ld returned 1 exit status
make: [mf2005-GPU] Error 1 (ignored)
Following is upcg7.f (this is not my code, I download it from here)
https://github.com/jdhughes-usgs/modflow-2005-upcg/blob/master/code/src/UPCG/upcg7.f
Following is upcgc.cpp and upcgc.h (this is not my code, I download it from here)
https://github.com/jdhughes-usgs/modflow-2005-upcg/blob/master/code/src/UPCG/upcgc.cpp
**My question is **
SUPCGILU0A is the subroutine defined in upcg7.f. And subroutine SUPCGILU0A is called from the C++ program upcgc.cpp.
upcgc7_init, upcgc7 and upcgc7_final are defined in upcgc.cpp, And these three are called from the fortran program upcg7.f.
I understand from my research that these are likely linker issues,or C++ and Fortran need to translate some function/routine from the other, but I cannot figure out what the problem is. Is there anyone out there who might have some insight into what the issue is?

Answer 1

If the upcgc7 routines reside in the C code, they probably do not have the trailing underscore. The best way to deal with this is to make use of the ISO_C_BINDING interface in Fortran and declare the interfaces to these routines.