C / C++ / MFC

Eikthrynir wrote:

Question 1: Is this scenario valid? Can it happen on a 32 bit machine?

Eikthrynir wrote:

Question 2: What if 32 bits get written to EAX, ThreadB resumes and writes to m_i64Value and after that, ThreadC resumes and the other 32 bits (changed by ThreadB) go to EDX? Is this also a possibility on 32 bit machines? If yes, what is the best way to return such a value (__int64, in this example)?

Eikthrynir wrote:

Question 3: But what if we still want to actually return the value and not copy it to the memory pointed by a_pi64Value? Can this be done somehow thread-safely and using the return instruction?

//Add zero to the value and return the initial value.
LONGLONG GetValue(__int64 *a_pi64Value)
{
	return InterlockedExchangeAdd64(a_pi64Value,0);
}

Eikthrynir wrote:

1. You call InterlockedExchange64 with a_pi64Value as the first parameter, so the __int64 variable pointed by a_pi64Value gets 0. Then, you return the previous value of that __int64 variable which is certainly not the one we are interested in, m_i64Value.

__int64 i64Val = InterlockedExchangeAdd64(m_i64Value,0);

Eikthrynir wrote:

2. GetValue returns a LONGLONG value, so we find ourselves in exactly the same situation from Question 2 (concerning the EAX and EDX registers)...

Abinash Mohanty wrote:

But it is returning zero.

Super Hornet wrote:

HRSRC hrsrc = FindResource(m_hinstLib, lpszName, RT_STRING);

HINSTANCE hinstance = ::LoadLibrary("SampleEN.dll");

if (!hinstance)
{
    AfxMessageBox("Failed to load");
}
else
{
    HINSTANCE hInstResourceClient = AfxGetResourceHandle();

    // Use DLL's instance handle
    AfxSetResourceHandle(hinstance);

    LPCTSTR lpszName = MAKEINTRESOURCE(1); //IDC_STATIC_TOP has been defined as 1 in the dll
    HRSRC hrsrc = FindResource(hinstance, lpszName, RT_STRING);
    if (hrsrc)
    {
        HGLOBAL hglobal = LoadResource(hinstance, hrsrc);
        LockResource(hglobal);

        TCHAR szTemp[256];
        LoadString(hinstance, IDC_STATIC_TOP, szTemp, 255);
    }

    AfxSetResourceHandle(hInstResourceClient);
}