Create static member in case of several shared libraries

build-clang.sh

#!/usr/bin/env bash

# clean dir if exists
rm -rf build
mkdir build
cd build || exit
CXX=clang++ CC=clang cmake ..
make

build-gnu.sh

#!/usr/bin/env bash

# clean dir if exists
rm -rf build
mkdir build
cd build || exit
CXX=g++ CC=gcc cmake ..
make

CMakeLists.txt

cmake_minimum_required(VERSION 2.8)
project(foo)

# Change the default to hidden, then you need to explicitly set it
# Thus, normally, you shouldn't have the problem
add_compile_options(-fvisibility=hidden) # only for testing the EXPORT define

# Create the shared library
add_library(mylib SHARED mylib.cpp)

# Create EXPORT header
include(GenerateExportHeader)
generate_export_header(mylib)
include_directories(${CMAKE_BINARY_DIR})

add_executable(example main.cpp foo.cpp) # foo also used mylib

# Link the lib
target_link_libraries(example mylib)

foo.cpp

#include "foo.h"

#include <iostream>

#include "mylib.h"

void foo () {
  std::cout << "foo -> A<int>: " << A<int>::x << std::endl;
  std::cout << "foo -> A<bool>: " << A<bool>::x << std::endl;
}

foo.h

#pragma once

void foo();

main.cpp

#include <iostream>

#include "foo.h"
#include "mylib.h"

int main () {
  std::cout << "main -> A<int>: " << A<int>::x << std::endl;
  std::cout << "main -> A<bool>: " << A<bool>::x << std::endl;

  // Making changes
  A<int>::x = 2;
  A<bool>::x = true;

  // Calling from foo
  foo();

  return 0;
}

mylib.cpp

#include "mylib.h"

template<> int A<int>::x = 1;
template<> int A<bool>::x = false;

mylib.h

#pragma once

#include <mylib_export.h>

template<typename T>
struct A {
  MYLIB_EXPORT static int x;
};

mylib_export_CLANG.h

#ifndef MYLIB_EXPORT_H
#define MYLIB_EXPORT_H

#ifdef MYLIB_STATIC_DEFINE
#  define MYLIB_EXPORT
#  define MYLIB_NO_EXPORT
#else
#  ifndef MYLIB_EXPORT
#    ifdef mylib_EXPORTS
        /* We are building this library */
#      define MYLIB_EXPORT __attribute__((visibility("default")))
#    else
        /* We are using this library */
#      define MYLIB_EXPORT __attribute__((visibility("default")))
#    endif
#  endif

#  ifndef MYLIB_NO_EXPORT
#    define MYLIB_NO_EXPORT __attribute__((visibility("hidden")))
#  endif
#endif

#ifndef MYLIB_DEPRECATED
#  define MYLIB_DEPRECATED __attribute__ ((__deprecated__))
#  define MYLIB_DEPRECATED_EXPORT MYLIB_EXPORT __attribute__ ((__deprecated__))
#  define MYLIB_DEPRECATED_NO_EXPORT MYLIB_NO_EXPORT __attribute__ ((__deprecated__))
#endif

#define DEFINE_NO_DEPRECATED 0
#if DEFINE_NO_DEPRECATED
# define MYLIB_NO_DEPRECATED
#endif

#endif

mylib_export_GNU.h

#ifndef MYLIB_EXPORT_H
#define MYLIB_EXPORT_H

#ifdef MYLIB_STATIC_DEFINE
#  define MYLIB_EXPORT
#  define MYLIB_NO_EXPORT
#else
#  ifndef MYLIB_EXPORT
#    ifdef mylib_EXPORTS
        /* We are building this library */
#      define MYLIB_EXPORT __attribute__((visibility("default")))
#    else
        /* We are using this library */
#      define MYLIB_EXPORT __attribute__((visibility("default")))
#    endif
#  endif

#  ifndef MYLIB_NO_EXPORT
#    define MYLIB_NO_EXPORT __attribute__((visibility("hidden")))
#  endif
#endif

#ifndef MYLIB_DEPRECATED
#  define MYLIB_DEPRECATED __attribute__ ((__deprecated__))
#endif

#ifndef MYLIB_DEPRECATED_EXPORT
#  define MYLIB_DEPRECATED_EXPORT MYLIB_EXPORT MYLIB_DEPRECATED
#endif

#ifndef MYLIB_DEPRECATED_NO_EXPORT
#  define MYLIB_DEPRECATED_NO_EXPORT MYLIB_NO_EXPORT MYLIB_DEPRECATED
#endif

#if 0 /* DEFINE_NO_DEPRECATED */
#  ifndef MYLIB_NO_DEPRECATED
#    define MYLIB_NO_DEPRECATED
#  endif
#endif

#endif /* MYLIB_EXPORT_H */

mylib_export_MSVC.h

#ifndef MYLIB_EXPORT_H
#define MYLIB_EXPORT_H

#ifdef MYLIB_STATIC_DEFINE
#  define MYLIB_EXPORT
#  define MYLIB_NO_EXPORT
#else
#  ifndef MYLIB_EXPORT
#    ifdef mylib_EXPORTS
        /* We are building this library */
#      define MYLIB_EXPORT __declspec(dllexport)
#    else
        /* We are using this library */
#      define MYLIB_EXPORT __declspec(dllimport)
#    endif
#  endif

#  ifndef MYLIB_NO_EXPORT
#    define MYLIB_NO_EXPORT 
#  endif
#endif

#ifndef MYLIB_DEPRECATED
#  define MYLIB_DEPRECATED __declspec(deprecated)
#endif

#ifndef MYLIB_DEPRECATED_EXPORT
#  define MYLIB_DEPRECATED_EXPORT MYLIB_EXPORT MYLIB_DEPRECATED
#endif

#ifndef MYLIB_DEPRECATED_NO_EXPORT
#  define MYLIB_DEPRECATED_NO_EXPORT MYLIB_NO_EXPORT MYLIB_DEPRECATED
#endif

#if 0 /* DEFINE_NO_DEPRECATED */
#  ifndef MYLIB_NO_DEPRECATED
#    define MYLIB_NO_DEPRECATED
#  endif
#endif

#endif /* MYLIB_EXPORT_H */