Ubuntu下Fortran与C如何交互

在Ubuntu下，Fortran和C可以通过以下几种方式进行交互：

1. 使用iso_c_binding模块

Fortran 2003引入了iso_c_binding模块，使得Fortran代码可以直接调用C函数，并且C代码也可以调用Fortran函数。

Fortran调用C

! example.f90
module example_mod
  use iso_c_binding, only: c_int, c_double
  implicit none

  interface
    subroutine c_function(x, y) bind(c, name="c_function")
      import c_int, c_double
      integer(c_int), intent(in) :: x
      real(c_double), intent(out) :: y
    end subroutine c_function
  end interface

contains

  subroutine fortran_function(x, y) bind(c, name="fortran_function")
    import c_int, c_double
    integer(c_int), intent(in) :: x
    real(c_double), intent(out) :: y

    y = sin(real(x, c_double))
  end subroutine fortran_function

end module example_mod

C调用Fortran

// example.c
#include <stdio.h>
#include "example.h"  // 生成的C头文件

int main() {
    int x = 5;
    double y;

    c_function(x, &y);
    printf("C function result: %f\n", y);

    fortran_function(x, &y);
    printf("Fortran function result: %f\n", y);

    return 0;
}

2. 使用extern "C"（仅限C++）

如果你在C++中使用Fortran，可以使用extern "C"来避免名称修饰问题。

Fortran代码

! example.f90
module example_mod
  use iso_c_binding, only: c_int, c_double
  implicit none

  interface
    subroutine c_function(x, y) bind(c, name="c_function")
      import c_int, c_double
      integer(c_int), intent(in) :: x
      real(c_double), intent(out) :: y
    end subroutine c_function
  end interface

contains

  subroutine fortran_function(x, y) bind(c, name="fortran_function")
    import c_int, c_double
    integer(c_int), intent(in) :: x
    real(c_double), intent(out) :: y

    y = sin(real(x, c_double))
  end subroutine fortran_function

end module example_mod

C++代码

// example.cpp
#include <iostream>
extern "C" {
    #include "example.h"  // 生成的C头文件
}

int main() {
    int x = 5;
    double y;

    c_function(x, &y);
    std::cout << "C function result: "<< y << std::endl;

    fortran_function(x, &y);
    std::cout << "Fortran function result: "<< y << std::endl;

    return 0;
}

3. 使用共享库

你可以将Fortran代码编译成共享库（.so文件），然后在C代码中链接并调用这些库。

Fortran代码

! example.f90
module example_mod
  use iso_c_binding, only: c_int, c_double
  implicit none

  interface
    subroutine c_function(x, y) bind(c, name="c_function")
      import c_int, c_double
      integer(c_int), intent(in) :: x
      real(c_double), intent(out) :: y
    end subroutine c_function
  end interface

contains

  subroutine fortran_function(x, y) bind(c, name="fortran_function")
    import c_int, c_double
    integer(c_int), intent(in) :: x
    real(c_double), intent(out) :: y

    y = sin(real(x, c_double))
  end subroutine fortran_function

end module example_mod

编译Fortran代码为共享库：

gfortran -fPIC -c example.f90 -o example.o
gfortran -shared -o libexample.so example.o

C代码

// example.c
#include <stdio.h>
#include <dlfcn.h>

typedef void (*fortran_function_t)(int, double*);

int main() {
    void* handle = dlopen("./libexample.so", RTLD_LAZY);
    if (!handle) {
        fprintf(stderr, "%s\n", dlerror());
        return 1;
    }

    fortran_function_t fortran_function = dlsym(handle, "fortran_function");
    if (!fortran_function) {
        fprintf(stderr, "%s\n", dlerror());
        dlclose(handle);
        return 1;
    }

    int x = 5;
    double y;

    fortran_function(x, &y);
    printf("Fortran function result: %f\n", y);

    dlclose(handle);
    return 0;
}

编译C代码并链接共享库：

gcc -o example example.c -ldl

通过这些方法，你可以在Ubuntu下实现Fortran和C之间的交互。选择哪种方法取决于你的具体需求和项目结构。