将接口模块过程从fortran导入C [英] importing interface module procedure from fortran into C

问题描述

如何使用extern将fortran interface导入到C中?

How should I import a fortran interface into C using extern?

假设我有以下fortran模块:

Suppose I have the following fortran module:

!swapper module
module swapper
   interface swap
      module procedure swap_r, swap_i, swap_c
   end interface
contains
    !subroutine implementations here:
    !swap_r takes two double precision as argument
    !swap_i takes two integers as argument
    !swap_c takes two characters as argument
end module swapper

那么我可以在C语言中执行以下操作吗?

Then can I just do in C, the following?

extern "C" void __swapper_MOD_swap(double*, double*)
extern "C" void __swapper_MOD_swap(int*, int*)
extern "C" void __swapper_MOD_swap(char*, char*)

或者，如果我保证只用双精度数字调用swap，我可以专门这样做吗?

Alternatively, if I promise to call swap with only double precision numbers, may I exclusively do this?

extern "C" void __swapper_MOD_swap(double*, double*)

推荐答案

看起来您实际上正在使用C ++.但是首先让我们为C或C风格的C ++回答:

It looks like you are actually using C++. But first lets answer for C or C-style C++:

不，你不能做

extern "C" void __swapper_MOD_swap(double*, double*)

您无法针对三种不同类型的参数执行此操作，即使对于单一类型的参数也无法执行此操作.

you cannot do it for three different types of arguments, you cannot do it even for a single type of arguments.

首先，库中实际上应该没有任何__swapper_MOD_swap.

There actually should not be any __swapper_MOD_swap in the library in the first place.

Fortran所做的是，它为三个特定的子例程swap_r, swap_i, swap_c保留了一个接口(这只是如何调用某事物的描述)，并允许您使用名称swap进行调用.

What Fortran does is that it keeps an interface (which is just a description how to call something) for the three specific subroutines swap_r, swap_i, swap_c and lets you call it by name swap.

但是该模块中没有实际的子例程swap！ Fortran只允许您使用不同的名称来调用这三个细节，仅此而已.

But there is NO actual subroutine swap in the module!!! Fortran will just let you call those three specifics under a different name, that's all.

没有办法像普通方法一样从C调用这些函数. C没有这种类型的泛型！(它确实有一些功能可以使用void*在任何类型上运行).

There is no way how to call those functions from C like a generic. C does not have this type of generics! (It does have some functions which operate on any type using void*).

在C ++中，您实际上可以制作专门针对不同类型的泛型，并且可以将Fortran过程称为泛型，但是您必须自己告诉C ++！您可以制作一个模板，然后手动对该模板进行特殊化处理，以调用相应的extern "C"函数.

In C++ you can actually make generics which are specialized for different types and you can call the Fortran procedures as a generic, but you have to tell that to C++ yourself! You can make a template and manually specialize this template to call the appropriate extern "C" functions.

例如，请参阅我的标题 https://github.com/LadaF/PoisFFT/blob/master/src/poisfft.h ，在这里我创建了一个C ++类，该类链接到extern "C" struct和一些extern "C"函数，但是这些函数都在Fortran中实现.

For an example see my header https://github.com/LadaF/PoisFFT/blob/master/src/poisfft.h where I make a C++ class which is linked to an extern "C" struct and some extern "C" functions which are however all implemented in Fortran.

最后，请勿使用__swapper_MOD_符号.使用bind(C,name="some_name")创建一些Fortran绑定，并通过extern "C"调用some_name，因为不同的Fortran编译器确实使用不同的名称处理方案.

Finally, DO NOT use the __swapper_MOD_ symbols. Create some Fortran binding using bind(C,name="some_name") and call some_name through extern "C", because different Fortran compilers DO use different name mangling schemes.

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