C++ Visual Studio 2015 “non-standard syntax; use '&' to create a pointer to member”

Question

I work with TaskScheduler COM, this is my code:

typedef HRESULT(*FuncOfBoll)(_Out_ VARIANT_BOOL* b);

static bool GetBool(FuncOfBoll func)
{
    VARIANT_BOOL b = VARIANT_FALSE;
    HRESULT hr = func(&b);
    if (FAILED(hr)) return FALSE;
    return b == VARIANT_TRUE;
}

void test(ITaskSettings* settings)
{
    bool b = GetBool(settings->get_StopIfGoingOnBatteries); // <= The error here
    // ...
}

and I get the following error:

Error C3867 'ITaskSettings::get_StopIfGoingOnBatteries': non-standard syntax; use '&' to create a pointer to member

What is my mistake and how to correct it?

Answer 1

The correct definition for a pointer to member function is:

typedef HRESULT(ITaskSettings::*FuncOfBoll)(_Out_ VARIANT_BOOL* b);

Then, you should pass the pointer to the object instance to function GetBool:

static bool GetBool(ITaskSettings* setting, FuncOfBoll func)
{
    VARIANT_BOOL b = VARIANT_FALSE;
    HRESULT hr = (setting->*func)(&b);
    ...
}

Or, with template:

template<class C>
static bool GetBool(C* p, HRESULT(C::*func)(_Out_ VARIANT_BOOL*))
{
    VARIANT_BOOL b = VARIANT_FALSE;
    HRESULT hr = (p->*func)(&b);
    ...
}

Invocation:

void test(ITaskSettings* settings)
{
    currentSetttings = settings;
    bool b = GetBool(settings, &ITaskSettings::mb_function);
}