question: public void markAsDefinitelyUnknown ( LocalVariableBinding local ) { if ( this != DEAD_END ) { this . tagBits |= NULL_FLAG_MASK ; long mask ; int position ; if ( ( position = local . id + this . maxFieldCount ) < BitCacheSize ) { this . nullBit1 |= ( mask = 1L << position ) ; this . nullBit4 |= mask ; this . nullBit2 &= ( mask = ~ mask ) ; this . nullBit3 &= mask ; if ( COVERAGE_TEST_FLAG ) { if ( CoverageTestId == 26 ) { this . nullBit4 = 0 ; } } } else { int vectorIndex = ( position / BitCacheSize ) - 1 ; if ( this . extra == null ) { int length = vectorIndex + 1 ; this . extra = new long [ extraLength ] [ ] ; for ( int j = 0 ; j < extraLength ; j ++ ) { this . extra [ j ] = new long [ length ] ; } } else { int oldLength ; if ( vectorIndex >= ( oldLength = this . extra [ 0 ] . length ) ) { for ( int j = 0 ; j < extraLength ; j ++ ) { System . arraycopy ( this . extra [ j ] , 0 , ( this . extra [ j ] = new long [ vectorIndex + 1 ] ) , 0 , oldLength ) ; } } } this . extra [ 2 ] [ vectorIndex ] |= ( mask = 1L << ( position % BitCacheSize ) ) ; this . extra [ 5 ] [ vectorIndex ] |= mask ; this . extra [ 3 ] [ vectorIndex ] &= ( mask = ~ mask ) ; this . extra [ 4 ] [ vectorIndex ] &= mask ; if ( COVERAGE_TEST_FLAG ) { if ( CoverageTestId == 27 ) { this . extra [ 5 ] [ vectorIndex ] = 0 ; } } } } }
target:  Mark a local as having been assigned to an unknown value.