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Fall 2018
1 Assignment Description.
In this assignment, you will need to implement a static analysis tool to detect bugs in source code. Static analysis
tools are commonly used as part of the continuous integration process to ensure the quality of the code (more details
in the slides and the papers in week 3). The tool will be implemented in Java. There are two tools that you may use
to help you with analyzing the code:
Eclipse JDT, an Abstract Syntax Tree (AST) parser that is part of the Eclipse IDE.
JavaParser, an open source AST parser for Java.
2 Bug Patterns.
You will need to implement a total of 10 bug patterns. The descriptions of the bug patterns are listed below:
1. Class defines equals() but not hashCode(). This class overrides equals(Object), but does not override hashCode().
Therefore, the class may violate the invariant that equal objects must have equal hashcodes. From FindBugs1
2. Comparison of String objects using == or !=. This code compares java.lang.String objects for reference equality
using the == or != operators. Unless both strings are either constants in a source file, or have been interned
using the String.intern() method, the same string value may be represented by two different String objects.
Consider using the equals(Object) method instead. From FindBugs2
3. Method may fail to close stream on exception. The method creates an IO stream object, does not assign it to
any fields, pass it to other methods, or return it, and does not appear to close it on all possible exception paths
out of the method. This may result in a file descriptor leak. It is generally a good idea to use a finally block to
ensure that streams are closed. From FindBugs3
4. Condition has no effect. This condition always produces the same result as the value of the involved variable
was narrowed before. Namely, the condition or the boolean variable in if/while always returns either true or
false. Probably something else was meant or condition can be removed. From FindBugs4
For example:
if (true) {...}
or
boolean var = false;
if (var) {...}
1http://findbugs.sourceforge.net/bugDescriptions.html#HE EQUALS NO HASHCODE
2http://findbugs.sourceforge.net/bugDescriptions.html#ES COMPARING STRINGS WITH EQ
3http://findbugs.sourceforge.net/bugDescriptions.html#OS OPEN STREAM EXCEPTION PATH
4http://findbugs.sourceforge.net/bugDescriptions.html#UC USELESS CONDITION
SOEN 7481 Fall 2018 Assignment #2
5. Inadequate logging information in catch blocks. Developers usually rely on logs for error diagnostics when
exceptions occur. However, sometimes, duplicate logging statements in different catch blocks of the same try
block may cause debugging difficulties since the logs fail to tell which exception occurred.
For example:
...
} catch (AlreadyClosedException closedException) {
s_logger.warn("Connection to AMQP service is lost.");
} catch (ConnectException connectException) {
s_logger.warn("Connection to AMQP service is lost.");
}
...
6. Unneeded computation in loops. There may be unneeded computation in loops, where you call a method inside
a loop, but the return value is never used.
For example:
...
for (int i = 0; i < 1000; i++){
Result r = computeResult(i); // unneeded computation
doSomething(i);
}
...
7. Unused methods. Detect both private and public methods that are not referenced/called anywhere in the code.
8. Empty exception. There is no debug message when an exception occurs, which may cause debugging difficulties.5
9. Unfinished exception handling code. There is a comment such as TODO or FIXME in the catch block of
exceptions.5
10. Over-catching an exception with system-termination. Developers are over-catching an exception (i.e., catching
very high-level exceptions, such as Exception or RunTimeException), and are calling abort or System.exit() in
the catch block.5
Note that, you can use either FindBugs or SpotBugs, since these two are almost identical (SpotBugs is successor of
FindBugs).
3 Testing your code.
You will need to design test cases for your code. For each bug pattern, you need to design some test cases, and more
importantly, you need to describe your design decision in the final report. You may use any testing framework (e.g.,
JUnit or TestNG) for your test case. There is no right or wrong answer in terms of test case design, but you must
provide a valid reason for your design.
4 Discussing your detection results.
You need to run your tool on two systems: Hadoop 3.0.06 and CloudStack 4.97
.
5From https://www.usenix.org/system/files/conference/osdi14/osdi14-paper-yuan.pdf
6https://github.com/apache/hadoop/tree/branch-3.0.0
7https://github.com/apache/cloudstack/tree/4.9
2
SOEN 7481 Fall 2018 Assignment #2
For bug pattern 1–4, you need to compare your detection results with that of FindBugs (since FindBugs is also able
to detect these bugs). Whenever there is any difference in the detection result, you need to include a discussion in
your final report regarding why the difference exist.
5 Final report.
The final report must be in ACM conference format (i.e., double column). You can find an example here. You can
also find the template file on the course website. Note that you have to follow the template; otherwise, you will lose
marks in the assignment.
You need to use this option in your latex file: \documentclass[sigconf]{acmart}
The final report should contain five or more pages. It needs to include (at least): abstract, introduction, detection
approach, design of the test cases, detection result and discussion, and conclusion. You must include the link to your
GitHub repository in the report.
The final format of the report must be in .pdf format.
6 Hosting code and report on GitHub.
Everything needs to be stored on GitHub, including all of your code, test case, and report. The report should
preferable be written in Latex. However, if you struggle with Latex, you may also use other tools (e.g., Google Doc),
as long as it can show the edit/version history.
Please make your repository private. You may also use BitBucket or GitLab.
7 Submitting your assignment.
Please submit your assignment by emailing the pdf file to:
SOEN7481Concordia@gmail.com
The subject of the email must be: [SOEN7481][Assignment][name1, name2, name3]
8 Evaluation
The final evaluation will be based on all factors in the deliverables. We will look at code quality, design of the test
case, quality of the report, and detection result and discussion.