Automated Debugging: CS259 Problem Set 4

#!/usr/bin/env python
# See instructions at line 124 and fill in the functions at 60 and 82
import sys
import copy

#the buggy program
def remove_html_markup(s):

tag   = False
quote = False
out   = “”

for c in s:

if c == ‘<‘ and not quote:

tag = True

elif c == ‘>’ and not quote:

tag = False

elif c == ‘”‘ or c == “‘” and tag:

quote = not quote

elif not tag:

out = out + c

return out

# The delta debugger
def ddmin(s):

#assert test(s) == “FAIL”

n = 2     # Initial granularity
while len(s) >= 2:

start = 0
subset_length = len(s) / n
some_complement_is_failing = False

while start < len(s):

complement = s[:start] + s[start + subset_length:]

if test(complement) == “FAIL”:

s = complement
n = max(n – 1, 2)
some_complement_is_failing = True
break

start += subset_length

if not some_complement_is_failing:

if n == len(s):

break

n = min(n * 2, len(s))

return s

# We use these variables to communicate between callbacks and drivers
the_line      = None
the_iteration = None
the_state     = None
the_diff      = None
the_input     = None

# FILL IN FROM YOUR SOLUTION IN THE PREVIOUS EXERCISE
def trace_fetch_state(frame, event, arg):

global the_line
global the_iteration
global the_state

line_number = frame.f_lineno
line_state = frame.f_locals
#print(line_number)
#print(line_state)
if event == ‘line’:

if line_number == the_line:

the_iteration = the_iteration – 1
#print(the_iteration)
if the_iteration == 0:

the_state = copy.deepcopy(line_state)
#print(the_state)
return None

return trace_fetch_state

# Get the state at LINE/ITERATION
def get_state(input, line, iteration):

global the_line
global the_iteration
global the_state

the_line      = line
the_iteration = iteration

sys.settrace(trace_fetch_state)
y = remove_html_markup(input)
sys.settrace(None)

return the_state

# FILL IN FROM YOUR SOLUTION IN THE PREVIOUS EXERCISE
def trace_apply_diff(frame, event, arg):

global the_line
global the_diff
global the_iteration

line_number = frame.f_lineno
#print(line_number)

if line_number == the_line:

the_iteration = the_iteration – 1

if the_iteration == 0:

frame.f_locals.update(the_diff)
the_line = None
return None

return trace_apply_diff

# Testing function: Call remove_html_output, stop at THE_LINE/THE_ITERATION,
# and apply the diffs in DIFFS at THE_LINE
def test(diffs):

global the_diff
global the_input
global the_line
global the_iteration

line      = the_line
iteration = the_iteration

the_diff = diffs
sys.settrace(trace_apply_diff)
y = remove_html_markup(the_input)
sys.settrace(None)

the_line      = line
the_iteration = iteration

if y.find(‘<‘) == -1:

return “PASS”

else:

return “FAIL”

html_fail = ‘”<b>foo</b>”‘
html_pass = “‘<b>foo</b>'”

locations = [(8, 1), (14, 1), (14, 2), (14, 3), (23, 1)]

def auto_cause_chain(locations):

global html_fail, html_pass, the_input, the_line, the_iteration, the_diff
print “The program was started with”, repr(html_fail)

prev_value = {}
prev_state = {}

# Loop to get touch line and iteration from a particular locations
for (line, iteration) in locations:

# Get the passing and the failing state
state_pass = get_state(html_pass, line, iteration)
state_fail = get_state(html_fail, line, iteration)

if state_pass == None:

state_pass = {}

if state_fail == None:

state_fail = {}

diffs = []

# Compute the differences between the passing and failing runs
for key in state_fail.keys():

if not state_pass.has_key(key) or state_pass[key] != state_fail[key]:

diffs.append((key, state_fail[key]))

# Minimize the failure-inducing set of differences
the_input = html_pass
the_line  = line
the_iteration = iteration
Stop = False
if test(diffs) == “FAIL”:

cause = ddmin(diffs)
print “Then, in Line ” + repr(line) + ” (iteration ” + repr(iteration) + “),”,
for key, value in cause:

if (key not in prev_value or prev_value[key] != value):

print “Then”, key, “became”, repr(value)
prev_value[key] = value

if Stop:

break

print “Then the program failed.”

auto_cause_chain(locations)

# The output should look like this:
“””
The program was started with ‘”<b>foo</b>”‘
Then, in Line 8 (iteration 1), s became ‘”<b>foo</b>”‘
Then, in Line 14 (iteration 1), c became ‘”‘
Then, in Line 14 (iteration 2), quote became True
Then, in Line 14 (iteration 3), out became ‘<‘
Then, in Line 23 (iteration 1), out became ‘<b>foo</b>’
Then the program failed.
“””