Question

I have a core project which I’m building as a shared library. In one of the headers, I’ve defined a simple class shown below:

typedef pthread_mutex_t Mutex;

class CORE_API AutoLock
{
public:
    AutoLock(Mutex& m);
    ~AutoLock();

private:
    AutoLock();
    AutoLock(const AutoLock&);
    AutoLock& operator=(const AutoLock&);

    Mutex m_Mutex;
};

where CORE_API is defined as:

#ifdef CORE_DLL
#define CORE_API    __attribute__ ((dllexport))
#else
#define CORE_API    __attribute__ ((dllimport))
#endif

In the Android.mk for core, I’ve defined CORE_DLL under LOCAL_CFLAGS. However, when building, I get the warning:

warning: 'dllimporot' attribute directive ignored

When ndk-build gets to the other project where I want to use the AutoLock class, I get the error:

error: 'AutoLock::AutoLock()' is private
error: within this context

Why would the compiler ignore the dllexport attribute? I would hope that once that’s fixed, my other project should build and be able to use the AutoLock class without any problems.

Answer 1

Shared libraries are created differently on Android (Linux) than with Windows.
In Windows you have the special dllimport and dllexport directives but not on Android (Linux).

When using your shared library, you should just compile with -lYourLibraryName

This might help you: http://www.adp-gmbh.ch/cpp/gcc/create_lib.html