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

问题描述

我真的需要你的帮助！我在最后期限，我正在努力学习刚刚足以完成一些工作。现在已经过了一个多星期了，我处理的问题似乎是一个直截了当的问题，但是我无法在网上成功实施解决方案。

长篇故事short：我需要从F77调用C ++代码。我编译g ++和gfortran。我是一个完整的新手makefile。当这些代码被编译为它们各自的程序的一部分时，它们是无错误的（我从我的C ++代码，而不是main（）函数，并试图使用它与fortran代码）。这是我的：

 
   #include< cmath> 
 #include< vector> 
 using namespace std; 
 
 externCdouble ShtObFun（double x []，int& tp）
 {
 return // double precision awesomeness 
} 
  

Fortran代码：

 子程序objfun（nv，var，f，impass）
隐含real（8）（ah，oz），integer（in）
c初始化包括tp， 
 $ bf = ShtObFun（var，tp）
 
 return 
 end 
  

b $ b

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：在函数'objfun_'中：
 opcase1.f :( .text + 0xbd）：未定义引用'shtobfun_'
 collect2 ：ld返回1退出状态
  

我尝试过各种其他方法，他们没有工作。如果需要，我可以稍后列出。

我已检查的网站：

从fortran调用C ++函数C ，
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 - 一起使用C / C ++和Fortran

编辑（对第一个答案的回复）：

如果我重写C ++代码为：

  #include< cmath> 
 #include< vector> 
 using namespace std; 
 
 double ShtObFun（double x []，int& tp）
 externCdouble shtobfun_（double * x，int * tp）{
 return ShtObFun * tp）; 
} 
 {
 cout<< reached tp =<< tp<< endl; 
 exit（1）; 
} 
  

我得到这个错误：
error： '
错误：在'{'token

之前的预期未限定标识符如果我将C ++代码重写为：

  #include< cmath> 
 #include< vector> 
 using namespace std; 
 
 double ShtObFun（double x []，int& tp）; 
 
 externCdouble 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reached tp = ，而应该说已达到tp = 1，因为我在fortran代码（整数tp = 1）中将tp初始化为1。如果我简单地声明该函数，我得到相同的问题：

  externCdouble shtobfun_（double * x，int * tp）
 {
 // cout等etc 
} 
  

解决方案

声明或别名

  externCdouble ShtObFun（double x [ int& tp）
  

为

  externCdouble shtobfun_（double x []，int& tp）
  

请参阅 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，而且它传递所有参数作为指针。所以你的F77接口应该声明为：

  externCdouble shtobfun_（double x []，int * tp）; 
  double ShtObFun（double x []，int& tp）
 externCdouble shtobfun_（double * x，int * tp）{
 return ShtObFun * tp）; 
} 
  
 
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.

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++ Code:
#include <cmath>
#include <vector>
using namespace std;

extern"C" double ShtObFun(double x[], int &tp)
{
    return //double precision awesomeness
}
Fortran Code:
    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 (shows only files listed above):
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
Error:
opcase1.o: In function 'objfun_':
opcase1.f:(.text+0xbd): undefined reference to 'shtobfun_'
collect2: ld returned 1 exit status
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?

The sites I've checked:

calling C++ function from fortran not C, 
Linking fortran and c++ binaries using gcc, , Calling C Code from FORTRAN, Cookbook - Calling C from Fortran, YoLinux - Using C/C++ and Fortran together

Edit (response to first answer):

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

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);
}
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
}

解决方案
declare or alias 
extern"C" double ShtObFun(double x[], int &tp)
as
extern"C" double shtobfun_(double x[], int &tp)
see http://gcc.gnu.org/onlinedocs/gcc/Weak-Pragmas.html

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


                        
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