Caller failing to release lock 'lock' before calling function 'func'.

The annotation _Requires_lock_not_held_ imposes a precondition that the lock count for the specified lock can't be greater than zero when the function is called. Warning C26111 is issued when a function fails to release the lock before it calls another function.

The following example generates warning C26111 because the _Requires_lock_not_held_ precondition is violated by the call to DoNotLock within the locked section.

typedef struct _DATA
{
    CRITICAL_SECTION cs;
    int d;
} DATA;

_Requires_lock_not_held_(p->cs)

void DoNotLock(DATA* p)
{
    EnterCriticalSection(&p->cs);
    p->d = 0;
    LeaveCriticalSection(&p->cs);
}

void LockedFunction(DATA* p)
{
    EnterCriticalSection(&p->cs);
    DoNotLock(p); // Warning C26111
    LeaveCriticalSection(&p->cs);
}