Problem with C++ dll being used in FORTRAN

Hi,
I am stuck at a point where I am using mixed language programming of C++ and FORTRAN. I have a C++ function in a dll which returns a pointer. I tried to call it from my FORTRAN program. I have no problem in compiling, linking and running. However, after the run I get the C pointer returned as 0. It is not a problem with the function in the dl because I have checked with the dll being called from both C++ and C# programs. So I think it is something to dow ith FORTRAN calling the C++ function. Here is the structure of the program:

// C++ Header
// ---------------
# include statements
#ifdef BUILD_DLL
    #define DLL_EXPORT __declspec(dllexport)
#else
//    #define DLL_EXPORT __declspec(dllimport)
#endif

//#ifdef __cplusplus
extern "C"
{
double DLL_EXPORT __cdecl *CalcAirProperties(int InputCombination, double Input1, double Input2, double Pressure);
}
// ---------------
//C++ source code
// ---------------
double DLL_EXPORT __cdecl *CalcAirProperties(int InputCombination, double Input1, double Input2, double Pressure)
{
    double *AirProperties = new double[7];
//Do Calculations
   return AirProperties
}
// ---------------

Here is my FORTRAN code:

!********************
PROGRAM ProgramMain
USE Statements
USE iso_c_binding, ONLY : c_ptr,c_double,c_f_pointer
IMPLICIT NONE
TYPE(c_ptr) :: c_p
REAL(c_double), POINTER :: f_p(:)
INTERFACE
  FUNCTION CalcAirProperties(InputComb, InpValue1,InpValue2,BarometricPressure) BIND(C,NAME='CalcAirProperties')
      USE ISO_C_BINDING
      INTEGER(kind=C_INT), INTENT(IN)    :: InputComb
      REAL(kind=C_DOUBLE), INTENT(IN)    :: InpValue1
      REAL(kind=C_DOUBLE), INTENT(IN)    :: InpValue2
      REAL(kind=C_DOUBLE), INTENT(IN)    :: BarometricPressure
      TYPE(c_ptr)   :: CalcAirProperties
  END FUNCTION
END INTERFACE
    REAL :: TempDB_Test
    REAL :: TempRH_Test
    REAL :: BaroPressure

      TempDB_Test = 308.15
      TempRH_Test = 0.69
      BaroPressure = 101.325
      
      c_p = CalcAirProperties(2,TempDB_Test,TempRH_Test,BaroPr
essure)
      
      CALL c_f_pointer(c_p,f_p,[7])
      
      RHiC = f_p(3)
      RhoAiC = f_p(7)
END ProgramMain
!********************

In the above set up the pointer returned by the c_p=CalcAirProperties() call is 0 and thus the values f_p is not pointing to the right array start.
So to remove all the problems with pointers I converted the C++ function to accept an array (by reference) so that I can set the desired array values inside the C++ function and thus pass the array back to FORTRAN. Here is what I did for that:

// C++ Header
// ---------------
# include statements
#ifdef BUILD_DLL
    #define DLL_EXPORT __declspec(dllexport)
#else
//    #define DLL_EXPORT __declspec(dllimport)
#endif

//#ifdef __cplusplus
extern "C"
{
void DLL_EXPORT __cdecl CalcAirProperties(int InputCombination, double Input1, double Input2, double Pressure,double PropertyArray[]);
}
// ---------------
//C++ source code
// ---------------
void DLL_EXPORT __cdecl CalcAirProperties(int InputCombination, double Input1, double Input2, double Pressure,double PropertyArray[])
{
    double *AirProperties = new double[7];
//Do Calculations
    for(int i =0;i<7;i++)
    {
      PropertyArray(i) = AirProperties(i);
    }
}
// ---------------

Here is my FORTRAN code:

!********************
PROGRAM ProgramMain
USE Statements
USE iso_c_binding, ONLY : c_ptr,c_double,c_f_pointer
IMPLICIT NONE
TYPE(c_ptr) :: c_p
REAL(c_double), POINTER :: f_p(:)
INTERFACE
  SUBROUTINE CalcAirProperties(InputComb, InpValue1,InpValue2,BarometricPressure,PropertyArr
ay) BIND(C,NAME='CalcAirProperties')
      USE ISO_C_BINDING
      INTEGER(kind=C_INT), INTENT(IN)    :: InputComb
      REAL(kind=C_DOUBLE), INTENT(IN)    :: InpValue1
      REAL(kind=C_DOUBLE), INTENT(IN)    :: InpValue2
      REAL(kind=C_DOUBLE), INTENT(IN)    :: BarometricPressure
      REAL(kind=C_DOUBLE), DIMENSION(7), INTENT(OUT)   :: PropertyArray
  END SUBROUTINE
END INTERFACE
    REAL :: TempDB_Test
    REAL :: TempRH_Test
    REAL :: BaroPressure
    REAL(kind=C_DOUBLE), DIMENSION(7)   :: PropertyArray
      TempDB_Test = 308.15
      TempRH_Test = 0.69
      BaroPressure = 101.325
      CALL CalcAirProperties(2,TempDB_Test,TempRH_Test,BaroPr
essure,PropertyArray)
      RHiC = PropertyArray(3)
      RhoAiC = PropertyArray(7)

END ProgramMain
!********************

The above method also did not work. So I am kind of lost. I am still a newbie when it comes to mixed language programming.

I am using gcc with Code::Blocks to create the C++ dll and gfortran with Simply Fortran IDE to create the fortran exe.

I would appreciate any help in this regards.

Regards
SNKP