Compile Fortran Function using g++

  c++, fortran95, macos

Given a very simple fortran (95) function and a very simple c++ call to the program, I should be able to compile the program using:

g++ -c main1.cpp
gfortran -c test.f95
g++ main1.o test.o -o run

However, here I get the following error:

ld: warning: object file (test.o) was built for newer macOS version (11.5) than being linked (11.0)
Undefined symbols for architecture arm64:
  "hello_()", referenced from:
      _main in main1.o
 "__gfortran_st_write", referenced from:
      _hello_ in test.o
  "__gfortran_st_write_done", referenced from:
  _hello_ in test.o

"__gfortran_transfer_character_write", referenced from:
hello in test.o
ld: symbol(s) not found for architecture arm64
clang: error: linker command failed with exit code 1 (use -v to see invocation)

Here, adding a -v tag before the -o tag and after the -o tag and the exe run did   not solve the problem, as suggested by the error message. 

Thank you for your help.

Source: Windows Questions C++