Cli 17: cannot locate root cause with RootCauseFinder

[HongshuW]

• Expected debugging procedure: 448 expand CommandLine cl, data slicing on cl.args.last -> 384 ~ 382 control slicing -> 380 data slicing on AbstractList$ListItr iterator -> 299 data slicing on Arrays$ArrayList (tokenList) -> 298 data slicing on String[] -> 297 expand ArrayList (tokens), data slicing on tokens.elementData[3] -> 272 ~ 261 control slicing -> 251 found root cause
• Root cause: missing break statement

[myxxxsquared]

Failure due to nature of the algorithm.

To fix this bug, we need to add a basic block alignment module to align each jump in the code, which is a huge change to the algorithm.

This algorithm will never find root cause in the following programs.

correct

def func():
    global x
    x = 1
    return
    x = 2

func()
assert(x == 1)

buggy

def func():
    global x
    x = 1
    x = 2

func()
assert(x == 1)

To fix this bug, we need to align each basic block and insert fake jump operations. For this example, a fake line in buggy will be added.

buggy

def func():
    global x
    x = 1
    if False: return # Fake line added to align the "return" statement in the correct program.
    x = 2

[myxxxsquared]

This could not be solved by mending. Because, using mending, you will know which trace make a step be executed. But you will not know why a step is not executed. Consider if there is a jump statement, you will not know which jump statement is wrong so that a step is not executed.