Re: Why does the compiler cannot pass?

From:

Victor Bazarov <v.bazarov@comcast.invalid>

Newsgroups:

comp.lang.c++

Date:

Mon, 28 Jan 2013 11:45:48 -0500

Message-ID:

<ke69vl$2h4$1@dont-email.me>

On 1/28/2013 11:07 AM, fl wrote:

Hi,
I am compiling the following program below the dot line, which is copied from a website. There are some link errors:

1> overload_Arrow0.cpp
1>overload_Arrow0.obj : error LNK2019: unresolved external symbol "public: struct A * __thiscall B::operator->(void)" (??CB@@QAEPAUA@@XZ) referenced in function _main
1>overload_Arrow0.obj : error LNK2019: unresolved external symbol "public: struct B __thiscall C::operator->(void)" (??CC@@QAE?AUB@@XZ) referenced in function _main
1>overload_Arrow0.obj : error LNK2019: unresolved external symbol "public: struct C __thiscall D::operator->(void)" (??CD@@QAE?AUC@@XZ) referenced in function _main

I do not solve this after several trials. What is wrong with the code?

Just like your linker tells you, it cannot find those functions.

Thanks a lot.

......
#include <iostream>

struct A {
    void foo();
};

void A::foo()
    {
        ;
    }

struct B { A* operator->(); };
struct C { B operator->(); };
struct D { C operator->(); };

The three lines above define classes B, C, D, respectively, and each of
those classes *declares* operator->() function, but there is no
*definition* of those functions (B::operator->, etc.) in your code. You
should consider defining them since you actually call those in your
'main' program.

int main()
{
D d;
d->foo();
}

V
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