pCur = pos.guards.protect( nLevel * 2 + 1, pPred->next( nLevel ), gc_protect );
// pCur.bits() means that pPred is logically deleted
// head cannot be deleted
assert( pCur.bits() == 0 );
pCur = pos.guards.protect( nLevel * 2 + 1, pPred->next( nLevel ), gc_protect );
// pCur.bits() means that pPred is logically deleted
// head cannot be deleted
assert( pCur.bits() == 0 );