Fortran C++ binding - wrong value being read in DLL(C++)

问题

I am trying to use Fortran with C++. I created a DLL(C++) by following this guide. However, instead of creating C++ MathClient.cpp program, which calls this DLL (as it is described in the guide), I created Fortran MathClient.F90 program, which calls this DLL.

Fortran main code:

PROGRAM MAIN

  USE MOD_INTERFACE

  IMPLICIT NONE
  
  INTEGER(C_INT) :: A, B
  INTEGER(C_INT) :: INDEX
  INTEGER(C_INT) :: CURRENT
  LOGICAL(C_BOOL) :: BOLEAN
  
  A = 1
  B = 1

  ! Initialize a Fibonacci relation sequence.
  CALL FIBONACCI_INIT(A, B)
  ! Write out the sequence values until overflow.
  DO
      
    BOLEAN = FIBONACCI_NEXT()
    IF (.NOT. BOLEAN) EXIT
    INDEX = FIBONACCI_INDEX()
    CURRENT = FIBONACCI_CURRENT()
    WRITE(*,*) INDEX, ': ', CURRENT
  
  END DO
  
  WRITE(*,*) FIBONACCI_INDEX() + 1, &
  'Fibonacci sequence values fit in an unsigned 64-bit integer.'

  END PROGRAM MAIN

Fortran module code:

MODULE MOD_INTERFACE

USE, INTRINSIC :: ISO_C_BINDING

INTERFACE
    SUBROUTINE FIBONACCI_INIT ( A, B ) bind ( C, name = "fibonacci_init" )
      IMPORT
      IMPLICIT NONE
      INTEGER (C_INT) :: A, B
    END SUBROUTINE FIBONACCI_INIT
    
    LOGICAL(C_BOOL) FUNCTION FIBONACCI_NEXT ( ) bind ( C, name = "fibonacci_next" )
      IMPORT
      IMPLICIT NONE
    END FUNCTION FIBONACCI_NEXT
  
    INTEGER(C_INT) FUNCTION FIBONACCI_CURRENT ( ) bind ( C, name = "fibonacci_current" )
      IMPORT
      IMPLICIT NONE
    END FUNCTION FIBONACCI_CURRENT

    INTEGER(C_INT) FUNCTION FIBONACCI_INDEX ( ) bind ( C, name = "fibonacci_index" )
      IMPORT
      IMPLICIT NONE
    END FUNCTION FIBONACCI_INDEX

END INTERFACE

END MODULE MOD_INTERFACE

The C++ functions in MathLibrary.cpp are the same as in the above-mentioned guide. The only difference is, that I add some std::cout, in order to print values of received variables in C++ functions.

The problem is, that C++ functions receive wrong integer(C_INT) values from Fortran main code. For example, the void fibonacci_init function should receive values current_ = 1, previous_ = 1 during initialization. Instead of that, the values are some huge integer numbers (current_ = 45028402782009632).

I am using Intel Parallel Studio and Visual Studio. I will be grateful for any help.

来源：https://stackoverflow.com/questions/65553923/fortran-c-binding-wrong-value-being-read-in-dllc

标签

c++

fortran

fortran-iso-c-binding