从 Fortran 调用 C++(链接问题?)

Calling C++ from Fortran (linking issue?)(从 Fortran 调用 C++(链接问题?))

问题描述

我真的需要你的帮助！我在最后期限内，我正在努力学习足以完成一些工作.一个多星期以来，我正在处理一个看似简单的问题，但我无法成功地在线实施解决方案.

I really need your help! I'm on a deadline and I'm trying to learn just enough to get some work done. It's been well over a week now that I'm dealing with what appears to be a straightforward issue but I haven't been able to successfully implement solutions online.

长话短说:我需要从 F77 调用 C++ 代码.我正在用 g++ 和 gfortran 编译.我是makefile的新手.当这些代码被编译为它们各自程序的一部分时，它们没有错误(我从我的 C++ 代码中获取一个函数，而不是 main()，并尝试将它与 fortran 代码一起使用).这是我得到的:

Long story short: I need to call C++ code from F77. I'm compiling with g++ and gfortran. I'm a complete newb to makefiles. When these codes are compiled as part of their respective programs, they are bug free (I'm taking a function from my C++ code, not main(), and trying to use it with the fortran code). Here's what I've got:

C++ 代码:

#include <cmath>
#include <vector>
using namespace std;

extern"C" double ShtObFun(double x[], int &tp)
{
    return //double precision awesomeness
}

Fortran 代码:

    subroutine objfun(nv, var, f, impass)
    implicit real(8) (a-h,o-z), integer (i-n)
c   initializations including tp, used below

    f = ShtObFun(var, tp)

    return
    end

Makefile(仅显示上面列出的文件):

all:
    g++ -c Objective_Functions.cpp
    gfortran -c -O3 opcase1.f
    gfortran opcase1.o Objective_Functions.o -fbounds-check -lstdc++ -g -o Program.out
    rm *.o

错误:

opcase1.o: In function 'objfun_':
opcase1.f:(.text+0xbd): undefined reference to 'shtobfun_'
collect2: ld returned 1 exit status

我已经尝试了多种其他方法，但都没有奏效.如果需要，我可以稍后列出.有人看到这里的问题吗?

I have tried this a variety of other ways and they did not work. I can list those later if requested. Does anyone see the issue here?

我检查过的网站:

从 fortran 而非 C 调用 C++ 函数，使用 gcc 链接 fortran 和 c++ 二进制文件, , 从 FORTRAN 调用 C 代码, Cookbook - 从 Fortran 调用 C, YoLinux - 将 C/C++ 和 Fortran 结合使用

编辑(回复第一个答案):

如果我将 C++ 代码重写为:

If I rewrite C++ code as:

#include <cmath>
#include <vector>
using namespace std;

double ShtObFun(double x[], int &tp)
extern"C" double shtobfun_(double *x, int *tp) {
    return ShtObFun(x, *tp);
}
{
    cout << "reached tp = " << tp << endl;
    exit(1);
}

我收到此错误:错误:extern"之前的预期初始化程序错误:{"令牌之前的预期 unqualified-id

I get this error: error: expected initializer before 'extern' error: expected unqualified-id before '{' token

如果我将 C++ 代码重写为:

If I rewrite C++ code as:

#include <cmath>
#include <vector>
using namespace std;

double ShtObFun(double x[], int &tp);

extern"C" double shtobfun_(double *x, int *tp) {
    return ShtObFun(x, *tp);
}

double ShtObFun(double x[], int &tp)
{
    cout << "reached tp = " << tp << endl;
    exit(1);
}

代码将编译，但我得到的结果是达到 tp = 0"，而它应该说达到 tp = 1"，因为我在 fortran 代码中将 tp 初始化为 1(整数 tp = 1).如果我简单地将函数声明为:

The code will compile but the result I get is "reached tp = 0", while it should say "reached tp = 1" because I initialized tp to 1 in the fortran code (integer tp = 1). And I get the same issue if I simply declare the function as:

extern"C" double shtobfun_(double *x, int *tp)
{
     //cout, etc
}

推荐答案

声明或别名

extern"C" double ShtObFun(double x[], int &tp)

作为

extern"C" double shtobfun_(double x[], int &tp)

参见 http://gcc.gnu.org/onlinedocs/gcc/Weak-Pragmas.html

这是你的第一步.第二步是认识到 Fortran 不知道引用，而且它将所有参数作为指针传递.所以你的 F77 接口应该声明为:

That's you first step. Second step is to recognize that Fortran has no idea about references, moreover it passes all arguments as a pointer. so you F77 interface should be declared as:

extern"C" double shtobfun_(double x[], int *tp);

把它们放在一起:

double ShtObFun(double x[], int &tp)
extern"C" double shtobfun_(double *x, int *tp) {
    return ShtObFun(x, *tp);
}

这篇关于从 Fortran 调用 C++(链接问题?)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编程学习网！