1. Ruru Yue1, Na Meng2, Qianxiang Wang1 1Peking University 2Virginia Tech
A Characterization Study of Repeated Bug Fixes
Ruru Yue1, Na Meng2, Qianxiang Wang1 1Peking University 2Virginia Tech

2. Motivation
Prior studies showed that developers apply repetitive code changes to multiple locations.
Nguyen et al. found that 17-45% bug fixes were repeated [1].
Tools were built to recommend similar bug fixes.
Clever detects and tracks code clones [2].
LASE suggests similar edits based on program transformation learned from two or more similar edit examples[3].

3. Problem Statement
Some fundamental research questions are still unexplored.
Q1: What is the frequency of repeated bug fixes?
Q2: Where are repeated fixes usually applied?
Q3: What are the common bugs and fix patterns of repeated fixes?

4. Study Findings 48-70% of repeated fixes occurred 2 times
Code change suggestion tools based on single examples are more helpful
73-100% of repeated fixes spanned at most 3 commits
Coding assistance tools should provide edit suggestions as early as possible
39% of repeated fixes added or deleted whole if- structures
Automatic program repair tools should focus more on if- statements

5. Outline
Motivation & Related Work
Study Approach
Experiments

6. Exemplar Patch
diff --git a/dom/CompilationUnit.java b/dom/CompilationUnit.java
-484,8 +484,8
3.0 */
public int getStartPosition(ASTNode node) {
if (this.commentMapper == null) {
- return -1;
+ if (this.commentMapper == null || node !=null) {
+ return node.getStartPosition();
} else {
return this.commentMapper.getStartPosition(node); }

7. Exemplar Hunk
diff --git a/dom/CompilationUnit.java b/dom/CompilationUnit.java
-484,8 +484,8
3.0 */
public int getStartPosition(ASTNode node) {
if (this.commentMapper == null) {
- return -1;
+ if (this.commentMapper == null || node!=null) {
+ return node.getStartPosition();
} else {
return this.commentMapper.getStartPosition(node); }
Hunk

8. Exemplar Hunk Code changes
diff --git a/dom/CompilationUnit.java b/dom/CompilationUnit.java
-484,8 +484,8
3.0 */
public int getStartPosition(ASTNode node) {
if (this.commentMapper == null) {
- return -1;
+ if (this.commentMapper == null || node!=null) {
+ return node.getStartPosition();
} else {
return this.commentMapper.getStartPosition(node); }
Code changes
Hunk

9. Exemplar Hunk Context lines Code changes Context lines
diff --git a/dom/CompilationUnit.java b/dom/CompilationUnit.java
-484,8 +484,8
3.0 */
public int getStartPosition(ASTNode node) {
if (this.commentMapper == null) {
- return -1;
+ if (this.commentMapper == null || node!=null) {
+ return node.getStartPosition();
} else {
return this.commentMapper.getStartPosition(node); }
Context lines
Code changes
Hunk
Context lines

10. Exemplar Fix
diff --git a/dom/CompilationUnit.java b/dom/CompilationUnit.java
-484,8 +484,8
3.0 */
public int getStartPosition(ASTNode node) {
if (this.commentMapper == null) {
- return -1;
+ if (this.commentMapper == null || node!=null) {
+ return node.getStartPosition();
} else {
return this.commentMapper.getStartPosition(node); }
Fix
Hunk

11. Approach Overview
Bug Fix Collection
Repeated Bug Fix Detection

12. Bug Fix Collection Identify Fixing Patches Extract Bug Fixes
Retrieve relevant commits using bug IDs in Bugzilla
Extract Bug Fixes
Exclude less important hunks
e.g. Hunks with changes to documentations
Extract fixes applied to methods
Use AST Parsers to identify methods’ code ranges

13. Repeated Bug Fix Detection
Format Bug Fixes
Identify Clone Regions with CCFinder [4]
Match Edit Operation Sequences

14. Two Exemplar Fixes Fix1 Fix2
- if (this.commentMapper == null) { - return -1; + if (this.commentMapper == null || node !=null) { + return node.getStartPosition();
Fix2
if (this.commentMapper == null) {
return -1;
if (this.commentMapper == null || astNode!= null){
return astNode.getLength();
else{
return this.commentMapper.getLength(astNode);

15. Format Bug Fixes FormattedFix1 FormattedFix2
- if (this.commentMapper == null) { - return -1; + if (this.commentMapper == null || node !=null) { + return node.getStartPosition();
FormattedFix2
if (this.commentMapper == null) {
return -1;
if (this.commentMapper == null || astNode!= null){
return astNode.getLength();
else{
return this.commentMapper.getLength(astNode);

16. Identify Clone Regions by CCFinder
- if (this.commentMapper == null) { - return -1; + if (this.commentMapper == null || node !=null) { + return node.getStartPosition();
CloneRegion2
if (this.commentMapper == null) {
return -1;
if (this.commentMapper == null || astNode!= null){
return astNode.getLength();
else{
return this.commentMapper.getLength(astNode);

17. Match Edit Operation Sequences
EditOperSeq1
- if (this.commentMapper == null) { - return -1; + if (this.commentMapper == null || node !=null) { + return node.getStartPosition();
EditOperSeq2
if (this.commentMapper == null) {
return -1;
if (this.commentMapper == null || astNode!= null){
return astNode.getLength();
else{
return this.commentMapper.getLength(astNode);

18. An Exemplar Repeated-fix Group
Similar fixes (e.g. Fix1 and Fix2) are gathered into the same repeated-fix group.
if (this.commentMapper == null) {
return -1;
if (this.commentMapper == null || node !=null) {
+ return node.getStartPosition();
if (this.commentMapper == null || astNode!= null){
return astNode.getLength();
else{
return this.commentMapper.getLength(astNode);
Fix1
Fix2

19. Outline
Motivation & Related Work
Study Approach
Experiments

20. Data Sets Property Eclipse JDT Mozilla Firefox LibreOffice
Resolved period of bugs
2005
2014
# of bugs
870
380
1,563
# of fixing patches
1,378
10,051
7,846
# fixes
16,289
3,451
33,057

21. Q1.D2. What’s the distribution of repeated-fix groups based on fix instance counts?
For most bugs, repeated fixes did not occur many times.
SYDIT [5] and LibSync [6] may be more helpful than LASE [3].

22. Q3. What are the common bugs and fix patterns of repeated fixes?
Sample Repeated-fix Groups
Randomly select 150 repeated-fix groups, with 50 groups from each project
Manually Analyze Repeated-fix Groups
Bug component: the main syntax component of a fix
Fix pattern: the way to resolve the bug

23. Exemplar Repeated Fix
1. - if (aStart) 2. - currFrame = aStart->GetNextSibling(); 3. - else 4. + if (aStart) { 5. + if (aStart->GetNextSibling()) 6. + currFrame = aStart->GetNextSibling(); 7. + else if (aStart->GetParent()->GetContent() ->IsXUL(nsGkAtom::menugroup)) 8. + currFrame = aStart->GetParent()->GetNextSibling(); 9. + } 10.+ else

24. Similarity Relationship
if (aStart)
currFrame = aStart->GetNextSibling();
else if (aStart) {
if (aStart->GetNextSibling())
currFrame = aStart->GetNextSibling();
else if (aStart->GetParent()->GetContent()
->IsXUL(nsGkAtom::menugroup))
currFrame = aStart->GetParent()->GetNextSibling(); }
else

25. Dependency Relationship
if (aStart)
currFrame = aStart->GetNextSibling();
else if (aStart) {
if (aStart->GetNextSibling())
currFrame = aStart->GetNextSibling();
else if (aStart->GetParent()->GetContent()
->IsXUL(nsGkAtom::menugroup))
currFrame = aStart->GetParent()->GetNextSibling(); }
else
Control depend on

26. Manual Analysis Bug Component: currFrame’s assignment in line 2
1. - if (aStart) 2. - currFrame = aStart->GetNextSibling(); 3. - else 4. + if (aStart) { 5. + if (aStart->GetNextSibling()) 6. + currFrame = aStart->GetNextSibling(); 7. + else if (aStart->GetParent()->GetContent() ->IsXUL(nsGkAtoms::menugroup)) 8. + currFrame = aStart->GetParent()->GetNextSibling(); 9. + } 10.+ else
Bug Component: currFrame’s assignment in line 2
Fix Pattern: modify the value assigned to currFrame

27. Q3. What are the common bugs and fix patterns of repeated fixes?
if-statement and if-condition were the most prevalent bug components.
Program repair tools like Prophet [7] and Angelix [8] can be useful for if-condition correction
We still need new tools to automate if-statement additions or deletions

28. Conclusions
We studied the frequency, edit locations, and semantic meanings of repeated fixes.
48-70% of repeated fixes occurred 2 times.
73-100% of repeated fixes spanned at most 3 commits.
39% of repeated fixes added or deleted whole if- structures.

29. Thank you!

30. Q1.D3:  What’s the distribution of repeated-fix groups based on patch counts?
Tools should generate edit suggestions as early as possible.
Integrating tools to IDE seems more promising than to VCS .

31. References
[1] T. T. Nguyen, H. A. Nguyen, N. H. Pham, J. Al-Kofahi, and T. N. Nguyen. Recurring bug fixes in object-oriented programs. In ACM/IEEE International Conference on Software Engineering, pages 315–324, 2010.
[2] T. T. Nguyen, H. A. Nguyen, N. H. Pham, J. M. Al-Kofahi, and T. N. Nguyen. Clone-aware configuration management. In ASE, pages 123– 134, 2009.
[3] N. Meng, M. Kim, and K. McKinley. LASE: Locating and applying systematic edits. In ICSE, page 10, 2013.
[4]  T. Kamiya, S. Kusumoto, and K. Inoue. CCFinder: A multilinguistic token-based code clone detection system for large scale source code. TSE, pages 654–670, 2002.
[5] N. Meng, M. Kim, and K. S. McKinley. Systematic editing: Generating program transformations from an example. In PLDI, pages 329–342, 2011.
[6] H. A. Nguyen, T. T. Nguyen, G. Wilson, Jr., A. T. Nguyen, M. Kim, and T. N. Nguyen. A graph- based approach to API usage adaptation. pages 302–321, 2010.
[7]  F. Long and M. Rinard. Automatic patch generation by learning correct code. SIGPLAN Not.,
[8] S. Mechtaev, J. Yi, and A. Roychoudhury. Angelix: Scalable multiline program patch synthesis via symbolic analysis. In ACM/IEEE International Conference on Software Engineering, pages 691– 701, 2016.