如何使用 fortran-C 绑定将 fortran 字符串传递给 c++ 中的 const char*？

Question

我需要将编译时已知的字符串从 fortran 传递到 c++ 库。 我的搜索结果中的所有页面都没有涉及这种特殊的区别。 这是当前代码的样子：

Fortran：

subroutine fci_wmm_associate_variable(array_name, array_pointer)
    implicit none
    character*100, intent(in), value       :: array_name
    type (c_ptr), intent(in)        :: array_pointer
    interface
        subroutine wmm_associate_variable(name_f, pointer_f) bind (c)
            use iso_c_binding
            character (c_char), intent(in)  :: name_f
            type (c_ptr), intent(in), value :: pointer_f
        end subroutine wmm_associate_variable
    end interface
    call wmm_associate_variable(array_name, array_pointer)
end subroutine fci_wmm_associate_variable

C++：

void wmm_associate_variable(char* varname, double* var_pointer)
{
    //do stuf
}

这编译得很好，但我的库需要 C++ function 如下所示：

void wmm_associate_variable(const char* varname, double* var_pointer)
{
    //do stuf
}

发生这种情况时，我得到一个未定义的引用：

undefined reference to `wmm_associate_variable'

如何使它适用于 const char*？

Answer 1

The Fortran-C interoperability feature works with C functions, consequently the C++ function needs to be declared with C linkage ( extern "C" ).

(Note the Fortran declaration of the C function has the first argument as a default character kind scalar with length c_char - what you more than likely want is for it to be a c_char kind, length one assumed size array - character (KIND=c_char), intent(in):: name_f(*) )