#if defined _WIN32 || defined __CYGWIN__
  #define DLL_PUBLIC __declspec(dllexport)
#else
  #if defined __GNUC__
    #define DLL_PUBLIC __attribute__ ((visibility("default")))
  #else
    #pragma message ("Compiler does not support symbol visibility.")
    #define DLL_PUBLIC
  #endif
#endif

#include <stdio.h>

int DLL_PUBLIC printLibraryString(const char *str)
{
    printf("C library says: %s", str);
    return 3;
}