Abstract
Many empirical software engineering studies show that there is a need for repositories where source codes are acquired, filtered and classified. During the last few years, Ethereum block explorer services have emerged as a popular project to explore and search for Ethereum blockchain data such as transactions, addresses, tokens, smart contracts’ source codes, prices and other activities taking place on the Ethereum blockchain. Despite the availability of this kind of service, retrieving specific information useful to empirical software engineering studies, such as the study of smart contracts’ software metrics, might require many subtasks, such as searching for specific transactions in a block, parsing files in HTML format, and filtering the smart contracts to remove duplicated code or unused smart contracts. In this paper, we afford this problem by creating Smart Corpus, a corpus of smart contracts in an organized, reasoned and up-to-date repository where Solidity source code and other metadata about Ethereum smart contracts can easily and systematically be retrieved. We present Smart Corpus’s design and its initial implementation, and we show how the data set of smart contracts’ source codes in a variety of programming languages can be queried and processed to get useful information on smart contracts and their software metrics. Smart Corpus aims to create a smart-contract repository where smart-contract data (source code, application binary interface (ABI) and byte code) are freely and immediately available and are classified based on the main software metrics identified in the scientific literature. Smart contracts’ source codes have been validated by EtherScan, and each contract comes with its own associated software metrics as computed by the freely available software PASO. Moreover, Smart Corpus can be easily extended as the number of new smart contracts increases day by day.
Highlights
With the advent of blockchain technology as a mainstream technological innovation, many researchers and software developers started investigating the new possibilities for software products relying on such an infrastructure
Smart Corpus has been in use for 10 months, since December 2019, and 100 K smart contracts have been downloaded via the user interface
We described the Smart Corpus project, an effort to bring smart-contract data to the hands of the research community, providing help to reproducible research and a less time-consuming way to gather data and to perform static analysis
Summary
With the advent of blockchain technology as a mainstream technological innovation, many researchers and software developers started investigating the new possibilities for software products relying on such an infrastructure. Second-generation blockchains offer the possibility to code so-called smart contracts in a Turing complete programming language on which all the main operations of traditional software systems can be carried out. Coding smart contracts which run in a blockchain environment has its peculiarities and constraints and differs from coding in traditional out-of-chain contexts. One of the major differences is the immutability of deployed code: if bugs or bad smells are introduced into a smart contract, these cannot be fixed afterwards with patches. Another contract must be deployed in substitution of the former and users must be well advised not to use the wrong code. Memory occupation on blockchain typically has a cost that developers want to reduce, and chaining all the blocks poses limitations to the reasonable space available for each smart contract imposing practical constraints to source code size
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