bool IsWritablePtr(PVOID p)
{
__try
{
*(volatile char *) p  = *(volatile char *) p 
}__except(1)
{
return false;
}
return true;
}

for (;;)
{
long l = *p;
if (_InterlockedCompareExchange(p, l, l)==l) break;
}

O>bool IsWritablePtr(PVOID p)
O>{
O>__try
O>{
O>*(volatile char *) p  = *(volatile char *) p 
O>}__except(1)
O>{
O>return false;
O>}
O>return true;
O>}
O>

bool IsWritablePtr(PVOID p)
{
    __try
    {
        __asm 
        {
            mov eax, p
            xor [eax],0
        }
    }
    __except(1)
    {
        return false;
    }
    return true;
}

__declspec (naked) void __fastcall PtrWriteTest(PVOID p)
{
    __asm
    {
        xor [ecx], 0
        ret
    }
}

void __cdecl checker(void *p)
{
    ::SetThreadAffinityMask(::GetCurrentThread(), 1);
    for (;;)
    {
        __try
        {
            PtrWriteTest(p);
        }
        __except(1)
        {
            printf("checker AV!\n");
        }        
    }
}

int _tmain(int argc, _TCHAR* argv[])
{
    ::SetThreadAffinityMask(::GetCurrentThread(), 2);
    volatile int v = 0;
    _beginthread(checker, 0, (void *)&v);
    for (;;)
    {
        volatile int v_prev = v;
        ++v;
        ++v_prev;
        volatile int v_now = v;
        if (v_prev!=v_now)
        {
            printf("%u!=%u\n", v_prev, v_now);
        }        
    }
    return 0;
}