How to define a static member struct in C++

Question

I have a class that has a static member struct

class SharedMem
{
public:     

    struct memory { 
        char buff[100]; 
        int status, pid1, pid2; 
    }; 

    static struct memory* shmptr; 
}

I would like to define the static struct using SharedMem::memory shmptr;

But I'm getting errors undefined reference to 'SharedMem::shmptr'

How do I properly define the struct in C++?

And follow up question, how can I define this struct if my class is entirely in the header file, can I define it after the class declaration at the bottom of the header file?

Thanks

Does this answer your question? [Undefined reference to static variable c++](https://stackoverflow.com/questions/16284629/undefined-reference-to-static-variable-c) — Ruzihm, Jan 13 '20 at 23:07
And [here](https://stackoverflow.com/questions/18860895/how-to-initialize-static-members-in-the-header) answers your second question. — Douglas Oliveira, Jan 13 '20 at 23:13

score 5 · Accepted Answer · edited Jan 14 '20 at 00:13

5

class SharedMem
{
public:     

    struct memory { 
        char buff[100]; 
        int status, pid1, pid2; 
    }; 

    static memory* shmptr; 
};

// must add this in the cpp file!
SharedMem::memory* SharedMem::shmptr = nullptr;

edited Jan 14 '20 at 00:13

Remy Lebeau

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answered Jan 13 '20 at 23:06

robthebloke

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How to define a static member struct in C++

1 Answers1