compiler construction - Instance of object in flex-bison c++

Question

My main.hpp looks like this :

#include "json.tab.h"
#include "ob.hpp"

extern Ob *ob;

In my test.l, I wrote :

%{
    #include "main.hpp"
%}


%token  KEY
%token  COMMA

%%
KEY_SET         : KEY                                                 {ob->someOp();}
                | KEY_SET COMMA KEY                                   {ob->someOp();}
%%

But this gives me :

C:......c:(.text+0x37a): undefined reference to `ob'
C:......c:(.text+0x38e): undefined reference to `Ob::someop()'

So how can I call that Ob object from anywhere in my parser?

My Ob class(Ob.hpp) :

#include <bits/stdc++.h>
using namespace std;

#ifndef O_H_
#define O_H_

using namespace std;

class Ob {
public:
    Ob();
    ~Ob();
    someop();
};

#endif /*O_H_*/

And Ob.cpp:

Ob::someop()
{
    cout << "c++ is lit" << endl;
}

Now I have made all method in Ob static, so that no need to have an instance. And my build rule looks something like this :

g++ lex.yy.c test.tab.c main.cpp *.hpp -o test.exe

And I made the parser generator plain, without any method call, and it works fine, no error, no warning :

%%
KEY_SET         : KEY     
                | KEY_SET COMMA KEY    
%%

And when I added {Ob::someOp();}, then it gives me the same error again.

All of my codes are here : https://gist.github.com/maifeeulasad/6d0ea58cd70fbe255a4834eb46f2e1fd

Answer 1

You should pass all the the .cpp files, and no .hpp, to the compile command. The .hpp will be automatically included by the preprocessor. If you don't do it (you are not including Ob.cpp in your command), then it can't find the definition of the functions contained in them.

So your compilation command should be this:

g++ lex.yy.c test.tab.c main.cpp Ob.cpp -o test.exe