How to reference static member variables from a struct within another class

Question

I'm trying to define some static constant strings in C++ and reference them from different files.

Here's how I have the information set up this far:

structClass.h

namespace test {
     typedef struct customstructure{
          static const std::string stringA;
      } customstructure;
}

structClass.cpp

namespace test {
     static const std::string customstructure::stringA = "This is String A";
}

Now I'm wondering how I would call this in a third file?

execute.cpp

void printStringA(){
    printf("stringA is: %s", test::customstructure::stringA.c_str());
}

gives me a compile error that says:

undefined reference to 'test::customstructure::stringA'

You don't need the `static` before the definition of the member. — The Paramagnetic Croissant, Jun 03 '14 at 20:13
`undefined reference` errors come from the linker, not the compiler, and indicate the you failed to include `structClass.cpp` in your link. — Chris Dodd, Jun 03 '14 at 20:31

M.M · Answer 1 · 2014-06-03T23:02:27.383

In this code:

namespace test {
     static const std::string customstructure::stringA = "This is String A";
}

remove the word static. In fact it is an error to have this, your compiler should give a more useful error message (although I suppose 'undefined reference' meets the requirements of "a diagnostic").

Standard reference: [class.static.data]#5 says that static data members have external linkage, however using the keyword static in the definition would specify internal linkage.

How to reference static member variables from a struct within another class

1 Answers1