[Findit] findit algorithms and a cluster-fuzz implementation.

tools/findit/findit_for_crash.py

+# Copyright (c) 2014 The Chromium Authors. All rights reserved.
+# Use of this source code is governed by a BSD-style license that can be
+# found in the LICENSE file.
+
+import os
+from threading import Lock, Thread
+
+import blame
+from common import utils
+import component_dictionary
+import crash_utils
+import git_repository_parser
+import match_set
+import svn_repository_parser
+
+
+LINE_CHANGE_PRIORITY = 1
+FILE_CHANGE_PRIORITY = 2
+_THIS_DIR = os.path.abspath(os.path.dirname(__file__))
+PARSED_CONFIG = crash_utils.ParseURLsFromConfig(os.path.join(_THIS_DIR,
+                                                             'config.ini'))
+
+
+def GenerateMatchEntry(
+    matches, revision, cl, file_path, file_name, function, component_path,

[stgao, 2014/08/18 22:37:09]

|revision| -> |revision_info|?
|cl| -> |cl_revision|?

[jeun, 2014/08/18 23:52:15]

Done.

+    component_name, crashed_lines, stack_frame_indices, file_change_type,
+    repository_parser):
+  """Generates a match object and adds it to the match set.
+
+  Args:
+    matches: A matchset object, a map from CL to a match object.
+    revision: The revision information, as returned from a function
+              ParseChangelog in parser.
+    cl: The SVN revision number or git hash.
+    file_path: The path of the file.
+    file_name: The name of the file that this CL might be the culprit cl.
+    function: The function that caused an crash.
+    component_path: The path of the component this file is from.
+    component_name: The name of the component the file is from.
+    crashed_lines: The list of the lines in the file that caused the crash.

[stgao, 2014/08/18 22:37:08]

Line number or line content?

[jeun, 2014/08/18 23:52:15]

Changed to crashed_line_numbers

+    stack_frame_indices: The list of positions of this file within a stack.
+    file_change_type: Whether file is modified, added or deleted.
+    repository_parser: The parser object to parse line diff.
+  """
+  # Check if this CL should be ignored.
+  with matches.matches_lock:
+    if cl in matches.cls_to_ignore:
+      return
+
+    # If this CL is not already identified as suspected, create a new entry.
+    if cl not in matches.matches:
+      match = match_set.Match(revision, component_name)
+      message = revision['message']
+      # TODO(jeun): Don't hold lock while issuing http request.
+      match.ParseMessage(message, matches.codereview_api_url)
+
+      # If this match is a revert, add to the set of CLs to be ignored.
+      if match.is_reverted:
+        matches.cls_to_ignore.add(cl)
+
+        # If this match has info on what CL it is reverted from, add that CL.
+        if match.revert_of:
+          matches.cls_to_ignore.add(match.revert_of)

[stgao, 2014/08/18 22:37:07]

What if |match.revert_of| is None?

It is not true that we could tell whether it is a revert or not by just the
"message".

[jeun, 2014/08/18 23:52:14]

I check in line 62 if match.revert_of is None
 
In match_set.py, I'm trying to be very conservative by marking it as a revert
only if it contains some sort of "reverting/revert of/reverts xxxxx". Also,
revert_of checks whether this CL reverts some other CL.

+
+        # Return because we do not need to look at this CL anymore.
+        return
+
+      # Add this CL to the set of matches.
+      matches.matches[cl] = match
+
+    # Else, bring in the existing result.
+    else:
+      match = matches.matches[cl]
+
+  # Parse line diff information for this file.
+  (diff_url, changed_line_numbers, changed_line_contents) = (
+      repository_parser.ParseLineDiff(
+          file_path, component_path, file_change_type, cl))
+
+  # Ignore this match if the component is not supported for svn.
+  if not diff_url:
+    return
+
+  # Find the intersection between the lines that this file crashed on and
+  # the changed lines.
+  (line_intersection, stack_frame_index_intersection) = (

[stgao, 2014/08/18 22:37:07]

line_number_intersection?

[jeun, 2014/08/18 23:52:14]

Done.

+      crash_utils.Intersection(
+          crashed_lines, stack_frame_indices, changed_line_numbers))
+
+  # Find the minimum distance between the changed lines and crashed lines.
+  min_distance = crash_utils.FindMinLineDistance(crashed_lines,
+                                                 changed_line_numbers)
+
+  # Check whether this CL changes the crashed lines or not.
+  if line_intersection:
+    priority = LINE_CHANGE_PRIORITY
+  else:
+    priority = FILE_CHANGE_PRIORITY
+
+  # Add the parsed information to the object.
+  with matches.matches_lock:
+    match.crashed_line_numbers.append(line_intersection)
+    match.changed_files.append(file_name)
+
+    # Update the min distance only if it is less than the current one.
+    if min_distance < match.min_distance:
+      match.min_distance = min_distance
+
+    # If this CL does not change the crashed line, all occurrence of this
+    # file in the stack has the same priority.
+    if not stack_frame_index_intersection:
+      stack_frame_index_intersection = stack_frame_indices
+    match.stack_frame_indices.append(stack_frame_index_intersection)
+    match.changed_file_urls.append(diff_url)
+
+    # Only record the highest rank of this CL.
+    if priority < match.rank:

[stgao, 2014/08/18 22:37:08]

If priority and rank are the same, could we just use one of them instead of
both?

[jeun, 2014/08/18 23:52:14]

match.rank is same as the highest priority. I will remove it.

+      match.rank = priority
+    match.priorities.append(priority)
+    match.function_list.append(function)
+
+
+def FindMatch(revisions, file_map, file_dict, component_path, component_name,
+              repository_parser, codereview_api_url):
+  """Finds a CL that modifies file in the stacktrace.
+
+  Args:
+    revisions: A dictionary mapping revision number to the CL information.

[stgao, 2014/08/18 22:37:09]

revision_info_map?

[jeun, 2014/08/18 23:52:14]

Done.

+    file_map: A dictionary mapping file to the revision that modifies it.

[stgao, 2014/08/18 22:37:08]

file_to_revision_info?

[jeun, 2014/08/18 23:52:14]

Done.

+    file_dict: A dictionary mapping file to its occurrence in stacktrace.

[stgao, 2014/08/18 22:37:08]

file_to_frames?

[jeun, 2014/08/18 23:52:14]

Renamed to file_to_crash_map

+    component_path: The path of the component to search for.
+    component_name: The name of the component to search for.
+    repository_parser: The parser object to parse the line diff.
+    codereview_api_url: A code review url to retrieve data from.
+
+  Returns:
+    Matches, a set of match objects.
+  """
+  matches = match_set.MatchSet(codereview_api_url)
+  threads = []
+
+  # For all files in stacktrace, if it is not header file, check against
+  # all CLs to see if any CL changes this file. If so, add to the set of
+  # suspected CLs.
+  for file_name in file_dict:
+    # Ignore header file.
+    if file_name.endswith('.h'):
+      continue
+
+    # If the file in the stacktrace is not changed in any commits, continue.
+    if file_name not in file_map:
+      continue
+
+    path_dict = file_dict.GetPathDic(file_name)
+    # There can be two files that are in different path but have same
+    # names, so also has to check path.
+    for path in path_dict:
+      crashed_lines = file_dict.GetCrashedLineNumbers(path)
+      stack_frame_nums = file_dict.GetCrashStackFrameindex(path)
+      function = file_dict.GetCrashFunction(path)
+
+      # Iterate through the revisions that this file is changed.
+      for (cl, file_change_type, file_path) in file_map[file_name]:
+        # If path of two files are different or if a commit deletes a file,
+        # continue.
+        if not crash_utils.GuessIfSameSubPath(path, file_path) or (
+            file_change_type == 'D'):
+          continue
+
+        revision = revisions[cl]
+
+        # Create a new thread for adding this CL.
+        match_thread = Thread(
+            target=GenerateMatchEntry,
+            args=[matches, revision, cl, file_path, file_name, function,
+                  component_path, component_name, crashed_lines,
+                  stack_frame_nums, file_change_type,
+                  repository_parser])
+        threads.append(match_thread)
+        match_thread.start()
+
+  # Make sure all threads finish before returning.
+  for match_thread in threads:
+    match_thread.join()
+
+  # Remove CLs that are revert.
+  matches.RemoveRevertedCLs()
+
+  return matches
+
+
+def FindMatchForComponent(component_path, file_dict, changelog,
+                          callstack_priority, results, results_lock):
+  """Parses changelog and finds suspected CLs for a given component.
+
+  Args:
+    component_path: The path of component to look for the culprit CL.
+    file_dict: A dictionary mapping file to its occurrence in stackframe.

[stgao, 2014/08/18 22:37:08]

file_to_frames?

Same for other occurrences of this name.

[jeun, 2014/08/18 23:52:15]

Done.

+    changelog: The parsed changelog for this component.
+    callstack_priority: The priority of this call stack, 0 if from crash stack,
+                        1 if from freed, 2 if from previously allocated.
+    results: A dictionary to store the result.
+    results_lock: A lock that guards results.
+  """
+  (repository_parser, component_name, revisions, file_to_revision_map) = \
+      changelog
+
+  # Find match for this component.
+  codereview_api_url = PARSED_CONFIG['codereview']['review_url']
+  component_result = FindMatch(
+      revisions, file_to_revision_map, file_dict, component_path,
+      component_name, repository_parser, codereview_api_url)
+  matches = component_result.matches
+
+  # For all the match results in a dictionary, add to the list so that it
+  # can be sorted.
+  with results_lock:
+    for cl in matches:
+      match = matches[cl]
+      results.append((callstack_priority, cl, match))
+
+
+def FindMatchForCallstack(
+    callstack, components, component_to_changelog_map, results,
+    results_lock):
+  """Finds culprit cl for a stack within a stacktrace.
+
+  For each components to look for, create new thread that computes the matches
+  and join the results at the end.
+  Args:

[stgao, 2014/08/18 22:37:09]

One empty line before this.

[jeun, 2014/08/18 23:52:14]

Done.

+    callstack: A callstack in a stacktrace to find the result for.
+    components: A set of components to look for.
+    component_to_changelog_map: A map from component to its parsed changelog.
+    results: A list to aggregrate results from all stacktraces.
+    results_lock: A lock that guards results.
+  """
+  # Create component dictionary from the component and call stack.
+  component_dict = component_dictionary.ComponentDictionary(callstack,
+                                                            components)
+  callstack_priority = callstack.priority
+
+  # Iterate through all components and create new thread for each component.
+  threads = []
+  for component_path in component_dict:
+    file_dict = component_dict.GetFileDict(component_path)

[stgao, 2014/08/18 22:37:08]

Not clear for var name |file_dict|.
Please rename it to a better one.

[jeun, 2014/08/18 23:52:14]

Done.

+
+    if component_path not in component_to_changelog_map:
+      continue

[stgao, 2014/08/18 22:37:08]

Why continue?
Please add a comment.

[jeun, 2014/08/18 23:52:15]

Done.

+    changelog = component_to_changelog_map[component_path]
+
+    t = Thread(
+        target=FindMatchForComponent,
+        args=[component_path, file_dict, changelog,
+              callstack_priority, results, results_lock])
+    threads.append(t)
+    t.start()
+
+  # Join the threads before returning.
+  for t in threads:
+    t.join()
+
+
+def FindMatchForStacktrace(stacktrace, components, regression_dict):

[stgao, 2014/08/18 22:37:07]

stack_trace?

[jeun, 2014/08/18 23:52:15]

I will go consistent with the variable name in other files. They are named
stacktrace.

+  """Finds the culprit CL for stacktrace.
+
+  The passed stacktrace is either from release build stacktrace
+  or debug build stacktrace.
+
+  Args:
+    stacktrace: A list of parsed stacks within a stacktrace.
+    components: A set of components to look for.
+    regression_dict: A dictionary mapping component path to its regression.
+
+  Returns:
+    A list of match results from all stacks.
+  """
+  # A list to aggregate results from the whole stacktrace.

[stgao, 2014/08/18 22:37:07]

multiple call stacks in the whole stack trace?

[jeun, 2014/08/18 23:52:14]

Done.

+  results = []
+  results_lock = Lock()
+
+  # Parse changelog for each of the components and store it.
+  svn_parser = svn_repository_parser.SVNParser(PARSED_CONFIG['svn'])
+  git_parser = git_repository_parser.GitParser(regression_dict,
+                                               PARSED_CONFIG['git'])
+
+  component_to_changelog_map = {}
+  for component_path in components:
+    component_object = regression_dict[component_path]
+    range_start = component_object['old_revision']
+    range_end = component_object['new_revision']
+    if range_start == '0':
+      continue

[stgao, 2014/08/18 22:37:09]

Why continue? Should we just return a message "Regression from 0 to * is too big
and not supported." ?

Please add a comment.

[jeun, 2014/08/18 23:52:15]

We are continuing because this loop is going over all the components, and if we
just return here, we are ignoring all other components which might not have 0 as
starting range. Should I just log an error message here?

+
+    component_name = regression_dict[component_path]['name']
+
+    # Check if the regression is git hash or a revision number, and create
+    # appropriate parser object.
+    is_git = utils.IsGitHash(range_start)
+    if is_git:
+      repository_parser = git_parser
+    else:
+      repository_parser = svn_parser
+
+    # Parse revisions and changed files in regression.
+    (revisions, file_to_revision_map) = repository_parser.ParseChangelog(
+        component_path, range_start, range_end)
+
+    if not (revisions and file_to_revision_map):
+      continue

[stgao, 2014/08/18 22:37:07]

Why continue?

Please add a comment.

For other code like this, please add comments.

[jeun, 2014/08/18 23:52:15]

Done.

+
+    component_to_changelog_map[component_path] = (repository_parser,
+                                                  component_name,
+                                                  revisions,
+                                                  file_to_revision_map)
+
+  # Create separate threads for each of the call stack in the stacktrace.
+  threads = []
+  for callstack in stacktrace.stack_list:
+    t = Thread(
+        target=FindMatchForCallstack,
+        args=[callstack, components, component_to_changelog_map,
+              results, results_lock])
+    threads.append(t)
+    t.start()
+
+  # Join the threads before returning.
+  for t in threads:
+    t.join()
+
+  return results
+
+
+def SortAndFilterMatches(matches):
+  """Filters the list of potential culprit CLs to remove noise.
+
+  Args:
+    matches: A list containing match results.
+
+  Returns:
+    Filtered match results.
+  """
+  new_matches = []
+  line_changed = False
+  in_crash_state = False

[stgao, 2014/08/18 22:37:09]

What's crash state?
Do you need this concept?
If so, please add some explanation what it is.

[jeun, 2014/08/18 23:52:14]

Added additional parameter to the function and explained the concept.

+  highest_priority_stack = crash_utils.INFINITY
+
+  # Sort the matches in specific order.

[stgao, 2014/08/18 22:37:09]

Please add more details on what order it is and why in that order.

This will help to understand the algorithm behind it.

[jeun, 2014/08/18 23:52:15]

Done.

+  matches.sort(key=lambda (stack_index, cl, match):
+               (match.rank, stack_index,
+                crash_utils.FindMinStackFrameNumber(match.stack_frame_indices,
+                                                    match.priorities),
+                -len(match.changed_files), match.min_distance))
+
+  # Iterate through the matches to find out what results are significant.
+  for stack_index, cl, match in matches:
+    # Check if the current match changes crashed line.
+    is_line_change = (match.rank == LINE_CHANGE_PRIORITY)
+
+    # Check which thread this match is from.
+    current_stack = stack_index
+    if current_stack < highest_priority_stack:

[stgao, 2014/08/18 22:37:07]

Will two stacks have the same priority? If so, what should we do?
Please also add comments to algorithm-related code.

[jeun, 2014/08/18 23:52:15]

Added more detailed comments. Two stacks having same priority is not a special
case.

+      highest_priority_stack = current_stack
+
+    # Check if current match changes a file that occurs in crash state.
+    flattened_stack_frame_indices = [i for sl in match.stack_frame_indices

[stgao, 2014/08/18 22:37:09]

Use full name for |sl|.

[jeun, 2014/08/18 23:52:15]

Done.

+                                     for i in sl]
+    current_in_crash_state = min(flattened_stack_frame_indices) < 5
+
+    # This match and anything lower than this should be ignored if:
+    # - Current match does not change crashed lines but there are matches
+    # that do so.
+    # - Current match is not in crash state but there are matches in it.
+    # - There are other matches that came from higher priority stack.
+    if (line_changed and not is_line_change) or (
+        in_crash_state and not current_in_crash_state) or (
+            current_stack > highest_priority_stack):
+      break
+
+    # Update the variables.
+    if is_line_change:
+      line_changed = True
+    if current_in_crash_state:
+      in_crash_state = True
+
+    # Add current match to the filtered result.
+    new_matches.append((stack_index, cl, match))
+
+  return new_matches
+
+
+def GenerateReasonForMatches(matches):
+  """Generates a reason that a match (CL) is a culprit cl.
+
+  Args:
+    matches: A list of match objects.
+  """
+  # Iterate through the matches in the list.
+  for i, _, match in matches:
+    reason = []
+
+    # Zip the files in the match by the reason they are suspected
+    # (how the file is modified) and sort it in specific order.

[stgao, 2014/08/18 22:37:08]

What order it is and why?

[jeun, 2014/08/18 23:52:14]

Done.

+    match_by_priority = zip(
+        match.priorities, match.crashed_line_numbers, match.changed_files,
+        match.changed_file_urls)
+
+    match_by_priority.sort(
+        key=lambda (priority, crashed_line_number, file_name, file_url):
+        (priority, len(file_name)))
+
+    # Iterate through the sorted match.
+    for i in range(len(match_by_priority)):
+      (priority, crashed_line_number, file_name, file_url) = \
+          match_by_priority[i]
+
+      # If the file in the match is a line change, append a explanation.
+      if priority == LINE_CHANGE_PRIORITY:
+        reason.append(
+            '      Line %s of file %s      which caused the crash according '

[stgao, 2014/08/18 22:37:09]

Why blank space at the beginning?
Formatting like indent here should be the responsibility of the end user.
Here we just provide the raw data without any format.

[jeun, 2014/08/18 23:52:14]

Done.

+            'to the stacktrace, is changed in this cl.\n' %
+            (crash_utils.PrettifyList(crashed_line_number),
+             crash_utils.PrettifyFiles([(file_name, file_url)])))
+
+      else:
+        # Get all the files that are not line change.
+        rest_of_the_files = match_by_priority[i:]
+
+        # Take care of single/multiple files in string.
+        if len(rest_of_the_files) == 1:
+          file_string = '      File %s      is changed in this cl.\n'

[stgao, 2014/08/18 22:37:07]

Same as above.

[jeun, 2014/08/18 23:52:15]

Done.

+        else:
+          file_string = '      Files %s      are changed in this cl.\n'
+
+        # Create a list of file name and its url, and prettify the list.
+        file_name_with_url = [(file_name, file_url)
+                              for (_, _, file_name, file_url)
+                              in rest_of_the_files]
+        pretty_file_name_url = crash_utils.PrettifyFiles(file_name_with_url)
+
+        # Add the reason, break because we took care of the rest of the files.
+        reason.append(file_string % pretty_file_name_url)
+        break
+
+    # Set the reason as string.
+    match.reason = ''.join(reason)
+
+
+def CombineMatches(matches):

[stgao, 2014/08/18 22:37:08]

CombineReasonsForMatches?

[jeun, 2014/08/18 23:52:15]

This is not only combining reasons, but also combine matches overall, because
different callstacks can have same CL as the match, so the matches list can
contain two same CLs.

+  """Combine possible duplicates in matches.
+
+  Args:
+    matches: A list of matches object, along with its callstack priority and
+             CL it is from.
+  Returns:
+    A combined list of matches.
+  """
+  combined_matches = []
+
+  for stack_index, cl, match in matches:
+    found_match = None
+
+    # Iterate through the list of combined matches.
+    for _, cl_combined, match_combined in combined_matches:
+      # Check for if current match is already higher up in the result.
+      if cl == cl_combined:
+        found_match = match_combined

[stgao, 2014/08/18 22:37:09]

add a break?

[jeun, 2014/08/18 23:52:14]

Done.

+
+    # If current match is not already in, add it to the list of matches.
+    if not found_match:
+      combined_matches.append((stack_index, cl, match))
+      continue
+
+    # Combine the reason if the current match is already in there.
+    found_match.reason += match.reason
+
+  return combined_matches
+
+
+def FilterAndGenerateReasonForMatches(result):
+  """A wrapper function.
+
+  It generates reasons for the matches and returns string representation
+  of filtered results.
+
+  Args:
+    result: A list of match objects.
+
+  Returns:
+    A string representation of filtered results.
+  """
+  new_result = SortAndFilterMatches(result)
+  GenerateReasonForMatches(new_result)
+  combined_matches = CombineMatches(new_result)
+  return crash_utils.MatchListToResultList(combined_matches)
+
+
+def ParseCrashComponents(main_stack, top_n_frames=3):

[stgao, 2014/08/18 22:37:09]

Why default is 3?
Would you mind a comment and explanation here?

[jeun, 2014/08/18 23:52:14]

It is an arbitrary number (it is because clusterfuzz seems to take top 3 frames
as the crash state), I'm not sure if I have to explain how I chose the number. 

+  """Parses the crashing component.
+
+  Args:
+    main_stack: Main stack from the stacktrace.
+    top_n_frames: A number of frames to regard as crashing frame.
+  Returns:
+    A set of components.
+  """
+  frame_list = main_stack.GetTopNFrames(top_n_frames)
+  components = set()
+
+  for frame in frame_list:
+    components.add(frame.component_path)
+
+  return components
+
+
+def GenerateAndFilterBlameList(callstack, crash_revision_dict, regression_dict):
+  """A wrapper function.
+
+  Finds blame information for stack and returns string representation.
+
+  Args:
+    callstack: A callstack to find the blame information.
+    crash_revision_dict: A dictionary mapping component to its crash revision.

[stgao, 2014/08/18 22:37:08]

component_to_revision_info?

[jeun, 2014/08/18 23:52:14]

Done.

+    regression_dict: A dictionary mapping component to its regression.
+
+  Returns:
+    A list of blame results.
+  """
+  # Setup parser objects to use for parsing blame information.
+  svn_parser = svn_repository_parser.SVNParser(PARSED_CONFIG['svn'])
+  git_parser = git_repository_parser.GitParser(regression_dict,
+                                               PARSED_CONFIG['git'])
+  parsers = {}
+  parsers['svn'] = svn_parser
+  parsers['git'] = git_parser
+
+  # Create and generate the blame objects from the callstack.
+  blame_list = blame.BlameList()
+  blame_list.FindBlame(callstack, crash_revision_dict, regression_dict,
+                       parsers)
+
+  blame_list.FilterAndSortBlameList()
+  return crash_utils.BlameListToResultList(blame_list)
+
+
+def FindItForCrash(stacktrace_list,
+                   callstack,
+                   parsed_regression,
+                   parsed_crash_revision):
+  """Finds the culprit CL from the list of stacktrace.
+
+  Args:
+    stacktrace_list: A list of stacktraces to look for, in the order of
+                     decreasing significance.
+    callstack: A callstack object to show blame information for, if there are
+               no results for all stacktraces in the stacktrace_list.
+    parsed_regression: A parsed regression information as a result of parsing

[stgao, 2014/08/18 22:37:08]

component_to_regression_info?

[jeun, 2014/08/18 23:52:14]

Done.

+                       DEPS file.
+    parsed_crash_revision: A parsed crash revision information.

[stgao, 2014/08/18 22:37:09]

Prefix "parsed" is not needed.

Same for other occurrences in all code.

[jeun, 2014/08/18 23:52:14]

Done.

+
+  Returns:
+    A list of result objects, with the message how the result is created.
+  """
+  # If regression information is not available, return blame information.
+  if not parsed_regression:
+    return_message = (
+        'Regression information is not available. The result is '
+        'the blame information.')
+    result = GenerateAndFilterBlameList(callstack, parsed_crash_revision,
+                                        parsed_regression)
+    return (return_message, result)
+
+  for stacktrace in stacktrace_list:
+    # Check the next stacktrace if current one is empty.
+    if not stacktrace.stack_list:
+      continue
+
+    # Get the crash stack for this stacktrace, and extract crashing components
+    # from it.
+    main_stack = stacktrace.GetCrashStack()
+    components = ParseCrashComponents(main_stack)

[stgao, 2014/08/18 22:37:08]

Why do we handle the first 3 frames only?
Add an explanation for the reason behind that.

[jeun, 2014/08/18 23:52:15]

Done.

+
+    result_for_stacktrace = FindMatchForStacktrace(stacktrace, components,
+                                                   parsed_regression)
+
+    # If the result is empty, check the next stacktrace. Else, return the
+    # filtered result.
+    if not result_for_stacktrace:
+      continue
+
+    return_message = (
+        'The result is a list of CLs that change the crashed files.')

[stgao, 2014/08/18 22:37:08]

Also add "Wrong result? Please email findit-for-me-eng@."

[jeun, 2014/08/18 23:52:15]

I will add it after discussing with Abhishek/Marty.

+    result = FilterAndGenerateReasonForMatches(result_for_stacktrace)
+    return (return_message, result)
+
+  # If not match is found, return the blame information for the input

[stgao, 2014/08/18 22:37:08]

"not" -> "no"?

[jeun, 2014/08/18 23:52:14]

Done.

+  # callstack.
+  return_message = (
+      'There are no CLs that change the crashed files. The result is the '
+      'blame information.')
+  result = GenerateAndFilterBlameList(callstack, parsed_crash_revision,
+                                      parsed_regression)
+  return (return_message, result)
+