如何通过iso_C_绑定从Fortran调用的C函数接收字符串？

我想从Fortran中调用一个C函数，并接收C函数中定义的字符串。我搜索了一下，但到目前为止，我找不到一个有效的、直截了当的答案

实际上，我已经找到了一个解决方法：接收一个字符数组，然后使用内在函数

transfer

将结果放入Fortran字符串中。 这是我的工作代码

Fortran主程序：

program pr
    implicit none
    character(200) :: stringa

    call strfromc(stringa)
    write (6,*) 'FPR stringa: "', trim(stringa),'"'

    stop
end program pr

program pr
    use sfc
    implicit none
    character(200) :: stringa

    call strfromc(stringa)
    write (6,*) 'FPR stringa: "', trim(stringa),'"'

    stop
end program pr

Fortran子程序：

subroutine strfromc(stringa)
    use iso_c_binding
    implicit none

    character(200) :: stringa

    interface
        subroutine getstrfromc(ld,d) bind(c,name='getString')
            import :: c_int, c_ptr
            integer(c_int) :: ld
            type(c_ptr), value :: d
        end subroutine getstrfromc
    end interface

    ! declare a character array of type c_char and sufficient length:
    character(c_char), dimension(200), target :: d1

    integer :: ld1 ! will contain the string length
    integer :: i

    ! the C pointer of character array d1 is passed:
    call getstrfromc(ld1, c_loc(d1))

    ! read the first ld1 elements of array d1 as a character string, which will be returned:
    stringa= transfer(d1(1:ld1), stringa)

    write (6,*) 'SF d1: ', (d1(i),i=1,ld1)
    write (6,*) 'SF stringa: "', trim(stringa),'"'
    write (6,*) ''

    return
end subroutine

module sfc
    use iso_c_binding
    implicit none

    interface
        subroutine getstrfromc(ld,d) bind(c,name='getString')
            import :: c_int, c_ptr
            integer(c_int) :: ld
            type(c_ptr), value :: d
        end subroutine getstrfromc
    end interface

contains

subroutine strfromc(d1)
    use iso_c_binding
    implicit none

    ! declare a character array of type c_char and sufficient length:
    character(c_char), dimension(200), target :: d1

    integer :: ld1 ! will contain the string length
    integer :: i


    ! the C pointer of character array d1 is passed:
    call getstrfromc(ld1, c_loc(d1))

    ! clean elements after the ld1-th:
    d1(ld1+1:)= ''

    write (6,*) 'SF d1: ', (d1(i),i=1,ld1)
    write (6,*) ''

    return
end subroutine

end module sfc

C功能：

#include <stdio.h>
#include <string.h>

void getString(int * lw, char * w) {
    printf("Enter a string:\n");
    scanf("%[^\n]", w); //scanning the whole string, including the white spaces

    *lw= strlen(w);

    printf("C: w: %s\n", w);
    printf("C: lw: %d\n", *lw);
    printf("\n");

    return;
}

#包括
#包括
void getString（int*lw，char*w）{
printf（“输入字符串：\n”）；
scanf（“%[^\n]”，w）；//扫描整个字符串，包括空格
*lw=斯特伦（w）；
printf（“C:w:%s\n”，w）；
printf（“C:lw:%d\n”，*lw）；
printf（“\n”）；
返回；
}

---

有人能给我一个更直接的建议吗？

我把它贴在一个答案里，因为它看起来更干净。 这是我根据@francescalus的建议修改的代码

Fortran主程序：

program pr
    implicit none
    character(200) :: stringa

    call strfromc(stringa)
    write (6,*) 'FPR stringa: "', trim(stringa),'"'

    stop
end program pr

program pr
    use sfc
    implicit none
    character(200) :: stringa

    call strfromc(stringa)
    write (6,*) 'FPR stringa: "', trim(stringa),'"'

    stop
end program pr

Fortran模块，包括与C函数和Fortran子程序的接口：

subroutine strfromc(stringa)
    use iso_c_binding
    implicit none

    character(200) :: stringa

    interface
        subroutine getstrfromc(ld,d) bind(c,name='getString')
            import :: c_int, c_ptr
            integer(c_int) :: ld
            type(c_ptr), value :: d
        end subroutine getstrfromc
    end interface

    ! declare a character array of type c_char and sufficient length:
    character(c_char), dimension(200), target :: d1

    integer :: ld1 ! will contain the string length
    integer :: i

    ! the C pointer of character array d1 is passed:
    call getstrfromc(ld1, c_loc(d1))

    ! read the first ld1 elements of array d1 as a character string, which will be returned:
    stringa= transfer(d1(1:ld1), stringa)

    write (6,*) 'SF d1: ', (d1(i),i=1,ld1)
    write (6,*) 'SF stringa: "', trim(stringa),'"'
    write (6,*) ''

    return
end subroutine

module sfc
    use iso_c_binding
    implicit none

    interface
        subroutine getstrfromc(ld,d) bind(c,name='getString')
            import :: c_int, c_ptr
            integer(c_int) :: ld
            type(c_ptr), value :: d
        end subroutine getstrfromc
    end interface

contains

subroutine strfromc(d1)
    use iso_c_binding
    implicit none

    ! declare a character array of type c_char and sufficient length:
    character(c_char), dimension(200), target :: d1

    integer :: ld1 ! will contain the string length
    integer :: i


    ! the C pointer of character array d1 is passed:
    call getstrfromc(ld1, c_loc(d1))

    ! clean elements after the ld1-th:
    d1(ld1+1:)= ''

    write (6,*) 'SF d1: ', (d1(i),i=1,ld1)
    write (6,*) ''

    return
end subroutine

end module sfc

C函数保持不变

---

。。。其他建议

为什么不简单地使用

C_CHAR

kind？我将您的代码“压缩”了一点：

program main
  use, intrinsic :: iso_c_binding, only: C_INT, C_CHAR
  implicit none
  integer         :: lw ! will contain the string length
  character(256)  :: w = "" ! will contain the string; Initialize to empty

  ! C interface
  interface
    subroutine getstrfromc( lw, w ) bind( c, name='getString' )
      import :: C_INT, C_CHAR
      implicit none
      integer(C_INT), intent(out)     :: lw
      character(C_CHAR), intent(out)  :: w(*)
    end subroutine getstrfromc
  end interface

  ! In Fortran variables are passed by default as "pointers".
  call getstrfromc( lw, w )

  ! Write string
  write (*,*) "Fortran: w: ", trim(w)
  write (*,*) "Fortran: lw:", lw

end program main

---

C函数保持不变。

你知道

字符（len=200）a

实际参数可以是与

字符（len=1）b（*）相关联的参数吗？

（或

b（200）

）伪参数？@francescalus我需要d1作为“目标”。我试着用它作为伪参数，编译器说我需要一个显式接口，用于子程序strfromcys，如果你有一个带有目标伪参数的

strfromc

，你需要这个子程序有一个主程序的显式接口。如果你给它一个（比如说，把strflomc放到一个使用的模块中），那么它能工作吗？是的，它能工作，谢谢！我在“回答”中发布我的新代码。是的！非常感谢。现在我将研究并找出为什么我早期使用c_char的尝试没有成功。。。再次感谢你！