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An Empirical Study of Dormant Bugs
Tse-Hsun(Peter) Chen Meiyappan Nagappan Emad Shihab Ahmed E. Hassan
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Most studies focus on post-release bugs
Version A Version B
File A
Bug 1 Bug 2Bugs Discovered!Assign Bugs to File A
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Some bugs may remain dormant for a long time
Version A Version CVersion B
File A
Bug is waken up, but is counted as post-release bug for Version B
Zzz… Zzz…
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What are dormant bugs?
Version BVersion A Version C Today
File A
Bug 1
File B
Bug 2 Bug 3
Bugs introduced in Version A
Not a dormant bug
Bug 2
Dormant bug (discovered one version after it was introduced )
Dormant bug (discovered many versions after it was introduced )
Bug 1
…
Zzz..Zzz..
Bug 3
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Dormant bugs affect perceived software quality
VersionA Version B
Version A has 5 bugs Version B has 10 bugs
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Dormant bugs affect perceived software quality
VersionA Version B
Version A has 5 bugs Version B has 10 bugs
Version B has 8 dormant bugs!
These dormant bugs were introduced in version A
Case study on 20 systems
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Studied 20 open-source systems in the Apache FoundationAnalyzed all versions
System LOCs: 61K ~ 1.5M
# dormant bugs29%
# non-dormant
bugs71%
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Many bugs are actually dormant bugs
VersionA Version C
Bug introduced in Version A
33% of bugs become dormant bugs!
VersionABugs reported in Version A
Many post-release bugs are actually introduced in MUCH EARLIER versions!
20% of bugs are dormant bugs from prior versions
RQ1: How quickly are dormant bugs fixed?
Research questions
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RQ2: What is the size of a dormant bug fix?
RQ3: Who fixes dormant bugs?
RQ4: What are the root causes of dormant bug fixes?
RQ1: How quickly are dormant bugs fixed?
Research questions
10
RQ2: What is the size of a dormant bug fix?
RQ3: Who fixes dormant bugs?
RQ4: What are the root causes of dormant bug fixes?
Dormant bugs are fixed faster and the fixes are larger
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Dormant Non-dormant
Take 5 days to fix (median)
Takes 60% more time to fix
Dormant Non-dormant
Fix size is 19 LOC (median)
Fix size is 50% smaller
RQ1: How quickly are dormant bugs fixed?
Research questions
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RQ2: What is the size of a dormant bug fix?
RQ3: Who fixes dormant bugs?
RQ4: What are the root causes of dormant bug fixes?
RQ1: How quickly are dormant bugs fixed?
Research questions
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RQ2: What is the size of a dormant bug fix?
RQ3: Who fixes dormant bugs?
RQ4: What are the root causes of dormant bug fixes?
Dormant fixers are more experienced
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Dormant Non-dormant
# of
prio
r com
mits
of b
ug fi
xers
RQ1: How quickly are dormant bugs fixed?
Research questions
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RQ2: What is the size of a dormant bug fix?
RQ3: Who fixes dormant bugs?
RQ4: What are the root causes of dormant bug fixes?
RQ1: How quickly are dormant bugs fixed?
Research questions
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RQ2: What is the size of a dormant bug fix?
RQ3: Who fixes dormant bugs?
RQ4: What are the root causes of dormant bug fixes?
Manual study of the root causes
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All bugs
Randomly sampled 357 dormant bugs and 357 non-dormant bugs
Manually classify the bugs
Manually-derived root causes
18% o
f bug
s be
long
to e
ach
man
ually
-der
ived
root
cau
se
Cornercases
Control flow
MissingFeatures
Process-ing
Implemen-tation
Stacked barplot of:
Dormant bugs are different from non-dormant bugs
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We should consider dormant bugs in future studies to avoid bias
They are different!
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