CP-Miner: A Tool for Finding Copy-paste and Related Bugs in Operating System Code

Copy-pasted code is very common in large software because programmers prefer reusing code via copy-paste in order to reduce programming effort. Recent studies show that copy-paste is prone to introducing bugs and a significant portion of operating system bugs concentrate in copy-pasted code. Unfortunately, it is challenging to efficiently identify copy-pasted code in large software. Existing copy-paste detection tools are either not scalable to large software, or cannot handle small modifications in copy-pasted code. Furthermore, few tools are available to detect copy-paste related bugs. In this paper we propose a tool, CP-Miner, that uses data mining techniques to efficiently identify copy-pasted code in large software including operating systems, and detects copy-paste related bugs. Specifically, it takes less than 20 minutes for CP-Miner to identify 190,000 copypasted segments in Linux and 150,000 in FreeBSD. Moreover, CP-Miner has detected 28 copy-paste related bugs in the latest version of Linux and 23 in FreeBSD. In addition, we analyze some interesting characteristics of copy-paste in Linux and FreeBSD, including the distribution of copypasted code across different length, granularity, modules, degrees of modification, and various software versions.