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Software tools detect bugs by inferring programmer's intentions
James Kloeppel,
Science Editor
217-244-1073, kloeppel@uiuc.edu
7/6/06
|
CHAMPAIGN, Ill.
– The
task of debugging huge computer programs can be made faster and easier
by using new software tools developed by programming experts at the
University of Illinois at Urbana-Champaign.
Computer science professor Yuanyuan
Zhou and her students have assembled a suite of software tools that
can find and correct bugs by inferring the programmer’s intentions.
The tools draw from observations on how programmers write code.
“Most bug-detection tools require reproduction of bugs during
execution,” Zhou said. “The program is slowed down significantly
and monitored by these tools, which watch for certain types of abnormal
behavior. Most of our tools, however, work by only examining the source
code for defects, requiring little effort from programmers.”
Copy-pasted code, for example, often appears in large programs. While
saving considerable programming effort, copy-pasted code can be the
source of numerous bugs. Zhou’s copy-paste tool, called CP-Miner,
uses data-mining techniques to find copy-pasted code in the program
and examine and correct that code for consistent modifications.
CP-Miner has found many bugs in the latest versions of large open-source
software used in the information technology industry, Zhou said. CP-Miner
is fast and efficient – it can scan 3-4 million lines of code
for copy-paste and related bugs in less than 30 minutes.
Large programs also tend to follow many implicit rules and assumptions,
so Zhou and her students developed a related tool, called PR-Miner,
to detect when those rules have been broken. Like CP-Miner, PR-Miner
is based on data-mining techniques.
“First, we mine the source code for patterns, repetitions and
correlations that point to implicit programming rules and assumptions,”
Zhou said. “Then we check that those rules and assumptions have
not been violated.”
PR-Miner also is very fast and has found many bugs in the latest open-source
software. It takes PR-Miner only a few minutes to scan 4 million lines
of code.
Not only are their efforts directed toward detecting, diagnosing and
fixing bugs, Zhou and her students also are exploring techniques that
allow software to survive in the presence of bugs. Rx, for example,
is a recovery tool that allows software to survive by treating bugs
like allergies.
“If you are allergic to cats, you try to avoid cats,” Zhou
said. “In much the same way, Rx is avoidance therapy for software
failure. If the software fails, Rx rolls the program back to a recent
checkpoint, and re-executes the program in a modified environment.”
A fourth tool, called Triage, diagnoses software failures at the end-user
site. Following a human-like diagnosis protocol, Triage rapidly identifies
the nature of the problem and provides valuable input to help programmers
quickly understand the failure and fix the bug.
“If something bad happens or the software crashes, Triage’s
diagnosis protocol will start automatically and quickly suggest a temporary
fix until programmers can release a fixing patch,” Zhou said.
In addition to being fast and efficient, Zhou’s software tools
are scalable and can be tailored for specific software programs, including
programs running on parallel processors.
The work was funded by the National Science Foundation and the Intel
Corp.
Editor’s note:
To reach Yuanyuan Zhou, call 217-244-4563; e-mail: yyzhou@uiuc.edu.
