Beep: Fine-grained Fix Localization by Learning to Predict Buggy Code Elements

TL;DR

This paper introduces Beep, a neural network architecture that predicts precise buggy code elements and necessary changes, improving fault localization and aiding automated program repair with higher accuracy and efficiency.

Contribution

Beep is the first neural approach to fine-grained fix localization using AST paths, significantly enhancing bug localization and repair effectiveness.

Findings

Beep outperforms baseline methods in localizing buggy tokens.

It achieves 30-45% recall@1 in predicting repair operators.

Both repair pipelines using Beep achieved 100% correctness in patches.

Abstract

Software Fault Localization refers to the activity of finding code elements (e.g., statements) that are related to a software failure. The state-of-the-art fault localization techniques, however, produce coarse-grained results that can deter manual debugging or mislead automated repair tools. In this work, we focus specifically on the fine-grained identification of code elements (i.e., tokens) that must be changed to fix a buggy program: we refer to it as fix localization. This paper introduces a neural network architecture (named Beep) that builds on AST paths to predict the buggy code element as well as the change action that must be applied to repair a program. Leveraging massive data of bugs and patches within the CoCoNut dataset, we trained a model that was (1) effective in localizing the buggy tokens with the Mean First Rank significantly higher than a statistics based baseline and a machine learning-based baseline, and (2) effective in predicting the repair operators (with the associated buggy code elements) with a Recall@1= 30-45% and the Mean First Rank=7-12 (evaluated by CoCoNut, ManySStuBs4J, and Defects4J datasets). To showcase how fine-grained fix localization can help program repair, we employ it in two repair pipelines where we use either a code completion engine to predict the correct token or a set of heuristics to search for the suitable donor code. A key strength of accurate fix localization for program repair is that it reduces the chance of patch overfitting, a challenge in generate-and-validate automated program repair: both two repair pipelines achieve a correctness ratio of 100%, i.e., all generated patches are found to be correct. Moreover, accurate fix localization helps enhance the efficiency of program repair.