问题描述
我挖在论坛上寻找一个解决方案，但我失败了。我的主要问题是我太用C语言和Fortran-C的互操作性小白才能明白我做错了什么究竟。
I digged on the forum looking for a solution but I failed. My main problem is I am too noob with C language and Fortran-C interoperability in order to understand what I am doing wrong exactly.
我要调用的Fortran从一个C程序，但我有与变量的声明问题。我做了一个例子。
I want to call a C routine from Fortran but I'm having problem with the declaration of the variables. I made an example.
这是C例程：
#include <stdio.h>
#include <stdlib.h>
#include <math.h>
#include <complex.h>
#undef I
int photon_trace(double x_init[4], double x_final[4])
//***************************************************
{
double r,m,t,phi;
t = x_init[0];
r = x_init[1];
m = x_init[2];
phi = x_init[3];
t=t+1.0;
r=r+1.0;
m=m+1.0;
phi=phi+1.0;
x_final[0] = t;
x_final[1] = r;
x_final[2] = m;
x_final[3] = phi;
return 0;
}
这是用Fortran主程序：
This is the main program in Fortran:
program main_dummy
! compile: f95 raytracing.f90 main_dummy.f90 dummy_trace.o -o main
use, intrinsic :: ISO_C_BINDING
use raytracing
implicit none
real(C_FLOAT), dimension(0:3) :: x_in, x_fin
x_in = (/1,2,3,4/)
x_fin = (/0,0,0,0/)
write(*,*)'x_in, x_fin before = ', x_in, x_fin
call photon_trace(C_FLOAT(x_in),C_FLOAT(x_fin))
write(*,*)'x_in, x_fin after = ', x_in, x_fin
end program main_dummy
这是与接口模块：
And this is the module with the interface:
module raytracing
Interface
integer (C_INT) function photon_trace(x_init, x_final) &
bind(C, name='photon_trace')
use , intrinsic :: ISO_C_BINDING
implicit none
type (c_ptr), value :: x_init, x_final
end function photon_trace
end interface
end module raytracing
根据谁给我的例程C， x_init 和 x_final 应该是三分球的家伙（右？ ）。
According to the guy who gave me the routine in C, x_init and x_final should be pointers (right?).
当我尝试编译它给了我在 photon_trace 在主程序参数列表当我打电话了错误。
When I try to compile it gives me an error in argument list when I call photon_trace in the main program.
有什么建议？我用gcc 4.8
Any suggestions? I'm using gcc 4.8
P.S。请问GCC 4.4具有对于相同的能力，以 ISO_C_BINDING 或我需要做一些不同的使用它？
P.S. Does gcc 4.4 have the same capabilities with respect to iso_c_binding or will I need to do something different for using it?
修改后VLADIMIR注释：
感谢弗拉基米尔！我打电话的功能，因为我见过这样的例子http://stackoverflow.com/tags/fortran-iso-c-binding/info
Thanks Vladimir! I was calling the function because I saw it on this example http://stackoverflow.com/tags/fortran-iso-c-binding/info
我给你建议的修改，它现在编译！
问题是C例程似乎与变量的地址，而不是变量本身工作。
I made the modification you suggested and it compiles now!Problem is that the C routine seems to work with the address of the variables and not the variables itself.
我把一些印在C程序：
int photon_trace(double x_init[4], double x_final[4])
//***************************************************
{
double r,m,t,phi;
t = x_init[0];
r = x_init[1];
m = x_init[2];
phi = x_init[3];
printf("t0 %f\n", t);
printf("r0 %f\n", r);
printf("m0 %f\n", t);
printf("phi0 %f\n", r);
t=t+1.0;
r=r+1.0;
m=m+1.0;
phi=phi+1.0;
printf("t1 %f\n", t);
printf("r1 %f\n", r);
printf("m1 %f\n", t);
printf("phi1 %f\n", r);
x_final[0] = t;
x_final[1] = r;
x_final[2] = m;
x_final[3] = phi;
return 0;
}
和在主体
program main_dummy
! compile: gcc -c dummy_trace.c
! f95 raytracing.f90 main_dummy.f90 dummy_trace.o -o main
use, intrinsic :: ISO_C_BINDING
use raytracing
implicit none
!real(kind=8) :: x_in(4), x_fin(4)
real(C_FLOAT), dimension(0:3) :: x_in, x_fin
integer :: rt_ok
x_in = (/1,2,3,4/)
x_fin = (/0,0,0,0/)
write(*,*)'x_in, x_fin before = ', x_in, x_fin
rt_ok = photon_trace(x_in,x_fin)
write(*,*)'return rt = ', rt_ok
write(*,*)'x_in, x_fin after = ', x_in, x_fin
end program main_dummy
这就是在屏幕上：
and that's what is on the screen:
x_in, x_fin before = 1.00000000 2.00000000 3.00000000 4.00000000 0.00000000 0.00000000 0.00000000 0.00000000
t0 2.000000
r0 512.000123
m0 2.000000
phi0 512.000123
t1 3.000000
r1 513.000123
m1 3.000000
phi1 513.000123
return rt = 0
x_in, x_fin after = 1.00000000 2.00000000 3.00000000 4.00000000 1.00000000 2.12500000 3.00000000 4.00097656
这里发生了什么？
What's happening here?
在提前为precious帮助非常感谢！
Many thanks in advance for the precious help!!
推荐答案
不要过度复杂化了。不及格的指针，而是通过引用传递数组
Do not over-complicate it. Don't pass the pointers, but pass the arrays by reference
此外，函数必须在离pression使用，而不是在调用语句。
Also, a function must be used in an expression, not in a call statement.
module raytracing
Interface
integer (C_INT) function photon_trace(x_init, x_final) &
bind(C, name='photon_trace')
use , intrinsic :: ISO_C_BINDING
implicit none
real(c_double) :: x_init(4), x_final(4)
end function photon_trace
end interface
end module raytracing
program main_dummy
! compile: f95 raytracing.f90 main_dummy.f90 dummy_trace.o -o main
use, intrinsic :: ISO_C_BINDING
use raytracing
implicit none
real(c_double), dimension(0:3) :: x_in, x_fin
integer ie
x_in = (/1,2,3,4/)
x_fin = (/0,0,0,0/)
write(*,*)'x_in, x_fin before = ', x_in, x_fin
ie = photon_trace(x_in,x_fin)
write(*,*)'x_in, x_fin after = ', x_in, x_fin
end program main_dummy
在C可互操作的Fortran程序通过指针变量，除非你使用值。这就是所谓的按引用传递的
In C interoperable procedures Fortran passes pointers to the variables, unless you use value. This is called pass by reference.
> gfortran ray.c ray.f90
> ./a.out
x_in, x_fin before = 1.0000000000000000 2.0000000000000000 3.0000000000000000 4.0000000000000000 0.0000000000000000 0.0000000000000000 0.0000000000000000 0.0000000000000000
x_in, x_fin after = 1.0000000000000000 2.0000000000000000 3.0000000000000000 4.0000000000000000 2.0000000000000000 3.0000000000000000 4.0000000000000000 5.0000000000000000
P.S。 GCC 4.4很老，但它在理论上它知道的C互操作的东西。试试吧，你会看到的。
P.S. gcc 4.4 very old, but it theoretically it knows the C interop stuff. Try it and you will see.
这篇关于ISO_C_BINDING使用指针调用C例程的Fortran从使用数组的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持！