C / C++ / MFC

//in header file of whatever class
CRITICAL_SECTION m_criticalsection;

//in constructor or initdialog in cpp
InitializeCriticalSection(&m_criticalsection);

//now safe to use anyhere you want
EnterCriticalSection(&m_criticalsection);
..
//do some really freaky stuff in the same function
..
LeaveCriticalSection(&m_crticalsection);

class CriticalSection
{
private :
    CRITICAL_SECTION cs_ ;
public :
    CriticalSection ()
    {
        ::InitializeCriticalSection ( &cs_ ) ;
    }
    ~CriticalSection ()
    {
        ::UninitializeCriticalSection ( &cs_ ) ;
    }
    operator CRITICAL_SECTION* ()
    {
        return &cs_ ;
    }
} ;

class CriticalSectionGuard
{
private :
    CRITICAL_SECTION * pcs_ ;
public :
    CriticalSectionGuard ( CRITICAL_SECTION * pcs ) : pcs_ ( pcs )
    {
        ::EnterCriticalSection ( pcs_ ) ;
    }
    ~CriticalSectionGuard ()
    {
        ::LeaveCriticalSection ( pcs_ ) ;
    }
} ;

class SharingSomeResource
{
private :
    CriticalSection cs_ ;
    ...
public :
    SomeMethodRequiringSynchronisation ()
    {
        CriticalSectionGuard csg ( cs_ ) ;
        // do your worst one at a time
    }
    ...
} ;

"The pointy end goes in the other man." - Antonio Banderas (Zorro, 1998)