Calling Fortran function and subroutines from a C or C++ function

1. 在main() 主函数中调用fortran 定义的子函数；
   基本思想：将fortran定义的函数，在C++函数中采用C接口重新声明为全局函数；为避免C++中函数的重载，通常在声明函数时常使用C的命令extern 声明函数为全局的
   a. Accessing Named Common from C and C++
   The following example is the Fortran subprogram FCTN called by the previous Cray C main program:

C *********** Fortran subprogram (f.f): ***********

     SUBROUTINE FCTN

     COMMON /ST/STI, STA(10), STD
     INTEGER STI
     REAL STA
     DOUBLE PRECISION STD

     INTEGER I

     WRITE(6,100) STI, STD
 100 FORMAT ('IN FORTRAN: STI = ', I5, ', STD = ', D25.20)
     WRITE(6,200) (STA(I), I = 1,10)
 200 FORMAT ('IN FORTRAN: STA =', 10F4.1)
     END

The following Cray C main program calls the Fortran subprogram FCTN:

#include <stdio.h>
struct
{
   int i;
   double a[10];
   long double d;
} ST;

main()
{
   int i;

   /* initialize struct ST */
   ST.i = 12345;

   for (i = 0; i < 10; i++)
      ST.a[i] = i;

   ST.d = 1234567890.1234567890L;

   /* print out the members of struct ST */
   printf("In C: ST.i = %d, ST.d = %20.10Lf\n", ST.i, ST.d);
   printf("In C: ST.a = ");
   for (i = 0; i < 10; i++)
      printf("%4.1f", ST.a[i]);
   printf("\n\n");

   /* call the fortran function */
   FCTN();
}

b.Accessing Blank Common from C or C++
The following example shows how Fortran blank common can be accessed using C or C++ source code:

#include <stdio.h>

struct st
{
  float a;
  float b[10];
} *ST;

#ifdef __cplusplus
  extern "C" struct st *MYCOMMON(void);
  extern "C" void FCTN(void);
#else
  fortran struct st *MYCOMMON(void);
  fortran void FCTN(void);
#endif

main()
{
    int i;

    ST = MYCOMMON();
    ST->a = 1.0;
    for (i = 0; i < 10; i++)
        ST->b[i] = i+2;
    printf("\n In C and C++\n");
    printf("     a = %5.1f\n", ST->a);
    printf("     b = ");
    for (i = 0; i < 10; i++)
        printf("%5.1f ", ST->b[i]);
    printf("\n\n");

    FCTN();
}

This Fortran source code accesses blank common and is accessed from the C or C++ source code in the preceding example:

SUBROUTINE FCTN
COMMON // STA,STB(10)
PRINT *, "IN FORTRAN"
PRINT *, "    STA = ",STA
PRINT *, "    STB = ",STB
STOP
END

FUNCTION MYCOMMON()
COMMON // A
MYCOMMON = LOC(A)
RETURN
END

Looking for detail information of this type of invoking, you can contact with this web-address:http://docs.cray.com/books/S-2179-52/html-S-2179-52/ppgzmrwh.html

1. C++ class functions calling fortran subroutine
   C++中的面向对象与Fortran中的面向对象的比较：
   http://www1.gantep.edu.tr/~bingul/seminar/f90_c++/comparison.html