Re: Get address of whole instance with multiple inheritance

From:
Yechezkel Mett <ymett.on.usenet@gmail.com>
Newsgroups:
comp.lang.c++.moderated
Date:
Thu, 11 Dec 2008 13:13:39 CST
Message-ID:
<aa2961f3-2a43-47bf-bfbb-1ca7a068624c@d36g2000prf.googlegroups.com>
On Dec 10, 3:58 pm, "dustin.fri...@googlemail.com"
<dustin.fri...@googlemail.com> wrote:

Hi,

is there any way to get a pointer to the "whole" instance after
casting to a base class.


The term you are looking for is "most derived object".

i.E.:

class Interface1 {
public:
        virtual void foo() = 0;

};

class Interface2 {
public:
        virtual void bar() = 0;

};

class Interface3 {
public:
        virtual void baz() = 0;

};

class Impl : public Interface1, public Interface2, public Interface3 {
public:

....

};

int main(int argc, char** argv) {
        Impl* impl = new Impl();
        printf("impl = %p\n", impl); // impl = 0x603010

....

        Interface2* if2 = impl;
        printf("if2 = %p\n", if2); // if2 = 0x603018

....

}

....

What I need is:
void* ptr = some_magic(if2); // Or any other interface

and ptr should now point to impl(0x603010), not to if2(0x603018).


void* ptr = dynamic_cast<void*>(if2);

Yechezkel Mett

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