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

this makefile :

    program = mf2005-gpu.f      # define fortran compile flags     f90flags= -g -fopenmp     f90= gfortran      # define c compile flags     # -d_uf defines unix naming conventions 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 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 object files make 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 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 how compile cuda_kernels.cu nvcc -c -arch sm_20 -lcuda -lcudart -lcusparse cuda_kernels.cu

this errors

    upcg7.o: in function `upcg7ar':     /home/zhangmj/mf2005_make/upcg7.f:731: undefined reference `upcgc7_init_'     upcg7.o: in function `upcg7ap':     /home/zhangmj/mf2005_make/upcg7.f:1272: undefined reference `upcgc7_'     upcg7.o: in function `upcg7da':     /home/zhangmj/mf2005_make/upcg7.f:1416: undefined reference `upcgc7_final_'     upcgc.o: in function `upcgc7':     upcgc.cpp:(.text+0xf6a): undefined reference `supcgilu0a'     collect2: ld returned 1 exit status     make: [mf2005-gpu] error 1 (ignored) 

following upcg7.f (this not code, download here) https://github.com/jdhughes-usgs/modflow-2005-upcg/blob/master/code/src/upcg/upcg7.f

following upcgc.cpp , upcgc.h (this not code, download here) https://github.com/jdhughes-usgs/modflow-2005-upcg/blob/master/code/src/upcg/upcgc.cpp

**my question ** supcgilu0a subroutine defined in upcg7.f. , subroutine supcgilu0a called c++ program upcgc.cpp. upcgc7_init, upcgc7 , upcgc7_final defined in upcgc.cpp, , these 3 called fortran program upcg7.f.

i understand research these linker issues,or c++ , fortran need translate function/routine other, cannot figure out problem is. there out there might have insight issue is?

if upcgc7 routines reside in c code, not have trailing underscore. best way deal make use of iso_c_binding interface in fortran , declare interfaces these routines.