各位大神，请问fortran调用C++函数时变量的传递方式是咋样的？

Question

我想将C++函数运行后的变量值返回到Fortran中，请问如何实现？以下是我的代码：我想得到经过abs()函数作用后的tn值fortran部分：program mainimplicit noneINTERFACESUBROUTINE abs(i) BIND(C)USE,INTRINSIC :: ISO_C_BINDINGINTEGER(C_INT), VALUE,INTENT(IN) :: iEND SUBROUTINE absEND INTERFACEinteger(4)::tncall trans(tn)write(*,*) tn............endC++部分extern "C" void trans(int *tempt){*temp=5;cout<<*tempt;}

Answer 1

// cplusplus source: cmain.cpp
#include <iostream>
extern "C" void get(int& tmp) {
std::cin >> tmp;
if (std::cin.good())
std::cout << "function \"get\" in C++:\t" << tmp << std::endl;
else {
std::cerr << "ERROR: get a value failure" << std::endl;
tmp = 0;
}
}

extern "C" void put(const int& tmp) {
// output numeric: 0xnnn formatting
std::cout.setf(std::ios_base::hex, std::ios_base::basefield);
std::cout.setf(std::ios_base::showbase);
std::cout << "function \"put\" in C++:\t" << tmp << std::endl;
}

!!! Fortran source: fmain.f08
module croutine
interface
!names difference between C++ and Fortran routine here
subroutine rcget(item) bind(C, name='get')
use, intrinsic :: iso_c_binding
integer(c_int), intent(inout) :: item
end subroutine rcget
subroutine put(item) bind(C)
use, intrinsic :: iso_c_binding
integer(c_int), intent(in) :: item
end subroutine put
end interface
end module croutine;

program main
use croutine
use, intrinsic :: iso_c_binding
integer(c_int) :: dat = 0
print *, "value in Fortran: ", dat
call rcget(dat)
print *, "value after called C++ function", dat
call put(dat)
print *, "Finish, has returned to Fortran"
end program