Nopol: Automatic Repair of Conditional Statement Bugs in Java Programs

Abstract

International audienceWe propose NOPOL, an approach to automatic repair of buggy conditional statements (i.e., if-then-else statements). This approach takes a buggy program as well as a test suite as input and generates a patch with a conditional expression as output. The test suite is required to contain passing test cases to model the expected behavior of the program and at least one failing test case that reveals the bug to be repaired. The process of NOPOL consists of three major phases. First, NOPOL employs angelic fix localization to identify expected values of a condition during the test execution. Second, runtime trace collection is used to collect variables and their actual values, including primitive data types and objected-oriented features (e.g., nullness checks), to serve as building blocks for patch generation. Third, NOPOL encodes these collected data into an instance of a Satisfiability Modulo Theory (SMT) problem; then a feasible solution to the SMT instance is translated back into a code patch. We evaluate NOPOL on 22 real-world bugs (16 bugs with buggy IF conditions and 6 bugs with missing preconditions) on two large open-source projects, namely Apache Commons Math and Apache Commons Lang. Empirical analysis on these bugs shows that our approach can effectively fix bugs with buggy IF conditions and missing preconditions. We illustrate the capabilities and limitations of NOPOL using case studies of real bug fixes

Watch out for this commit! A study of influential software changes

“…While GenProg relies on randomness, utilizing program synthesis techniques can directly generate patches even though they are limited to a certain subset of bugs. Other notable approaches include contract‐based fixing, program repair based on behavior models, and conditional statement repair …”

Contract-based program repair without the contracts

“…"Semantic" fix actions-based on the information captured by the state in suspicious snapshotsare usefully complemented by a few "syntactic" fix actionsbased on simple mutation operators that capture common sources of programming mistakes such as off-by-one errors. Following an approach adopted by other APR techniques [13], [36] (a 1 , . . .…”

“…GenProg [33] pioneered the "generate-and-validate" approach, where many plausible fixes are generated based on heuristics, and then are validated against the available tests. More recently, others [5], [21], [22], [24], [36] have pursued the "constraint-based" approach, where fixes are constructed to satisfy suitable constraints that correspond to their validity. The two approaches are not sharply distinct, in that fixes generated by constraintbased techniques may still require validation if the constraints they satisfy by construction are not sufficiently precise to ensure that they are correct-as it often happens when dealing with incomplete specifications.…”

“…Nopol [36] only targets conditional expressions, and uses a form of angelic debugging [3], [37] to reconstruct the expected value of a condition in passing vs. failing runs; based on it, it synthesizes a new conditional expression using an SMT solver. SPR [16] also combines condition synthesis with a dynamic analysis of the value each abstract conditional expression should take to make all tests pass, which helps aggressively prune the search space when no plausible repair exists.…”

Towards the Quality Improvement of Cross-Platform Mobile Applications

“…Recent years, researchers have proposed approaches for automatically repair bugs such as [8,18,24]. Test-based repair repair approaches [8] use test suite as correctness oracles, i.e., they are used as proxies of the program specification.…”