Code Clone Matching: A Practical and Effective Approach to Find Code Snippets

Finding the same or similar code snippets in source code is one of fundamental activities in software maintenance. Text-based pattern matching tools such as grep is frequently used for such purpose, but making proper queries for the expected result is not easy. Code clone detectors could be used but their features and result are generally excessive. In this paper, we propose Code Clone matching (CC matching for short) that employs a combination of token-based clone detection and meta-patterns enhanced with meta-tokens. The user simply gives a query code snippet possibly with a few meta-tokens and then gets the resulting snippets, forming type 1, 2, or 3 code clone pairs between the query and result. By using a code snippet with meta-tokens as the query, the resulting matches are well controlled by the users. CC matching has been implemented as a practical and efficient tool named ccgrep, with grep-like user interface. The evaluation shows that ccgrep~ is a very effective to find various kinds of code snippets.