For many years now, modern software is known to be developed in multiple languages (hence termed as multilingual or multi-language software). Yet, to date, we still only have very limited knowledge about how multilingual software systems are constructed. For instance, it is not yet really clear how different languages are used, selected together, and why they have been so in multilingual software development. Given the fact that using multiple languages in a single software project has become a norm, understanding language use and selection (i.e., language profile ) as a basic element of the multilingual construction in contemporary software engineering is an essential first step. In this article, we set out to fill this gap with a large-scale characterization study on language use and selection in open-source multilingual software. We start with presenting an updated overview of language use in 7,113 GitHub projects spanning the 5 past years by characterizing overall statistics of language profiles, followed by a deeper look into the functionality relevance/justification of language selection in these projects through association rule mining. We proceed with an evolutionary characterization of 1,000 GitHub projects for each of the 10 past years to provide a longitudinal view of how language use and selection have changed over the years, as well as how the association between functionality and language selection has been evolving. Among many other findings, our study revealed a growing trend of using three to five languages in one multilingual software project and the noticeable stableness of top language selections. We found a non-trivial association between language selection and certain functionality domains, which was less stable than that with individual languages over time. In a historical context, we also have observed major shifts in these characteristics of multilingual systems both in contrast to earlier peer studies and along the evolutionary timeline. Our findings offer essential knowledge on the multilingual construction in modern software development. Based on our results, we also provide insights and actionable suggestions for both researchers and developers of multilingual systems.

Developing software projects that incorporate multiple languages has been a prevalent practice for many years. However, theissuesencountered by developers during the development process, the underlyingchallengescausing these issues, and thesolutionsprovided to developers remain unknown. In this paper, our objective is to provide answers to these questions by conducting a study on developer discussions on Stack Overflow (SO). Through a manual analysis of 586 highly relevant posts spanning 14 years, we revealed that multilingual development is a highly and sustainably active topic on SO, with older questions becoming inactive and newer ones getting first asked (and then mostly remaining active for more than one year). From these posts, we observed a diverse array of issues (11 categories), primarily centered around interfacing and data handling across different languages. Our analysis suggests that error/exception handling issues were the most difficult to resolve among those issue categories, while security related issues were most likely to receive an accepted answer. The primary challenge faced by developers was the complexity and diversity inherent in building multilingual code and ensuring interoperability. Additionally, developers often struggled due to a lack of technical expertise on the varied features of different programming languages (e.g., threading and memory management mechanisms). In addition, properly handling message passing across languages constituted a key challenge with using implicit language interfacing. Notably, Stack Overflow emerged as a crucial source of solutions to these challenges, with the majority (73%) of the posts receiving accepted answers, most within a week (36.5% within 24 hours and 25% in the following six days). Based on our analysis results, we have formulated actionable insights and recommendations that can be utilized by researchers and developers in this field.

Given the widespread use of Python and its sustaining impact, the security and reliability of the Python runtime system is highly and broadly critical. Yet with real-world bugs in Python runtimes being continuously and increasingly reported, technique/tool support for automated detection of such bugs is still largely lacking. In this paper, we present PyRTFuzz, a novel fuzzing technique/tool for holistically testing Python runtimes including the language interpreter and its runtime libraries. PyRTFuzz combines generationand mutation-based fuzzing at the compiler- and application-testing level, respectively, as enabled by static/dynamic analysis for extracting runtime API descriptions, a declarative, specification language for valid and diverse Python code generation, and a custom type-guided mutation strategy for format/structure-aware application input generation. We implemented PyRTFuzz for the primary Python implementation (CPython) and applied it to three versions of the runtime. Our experiments revealed 61 new, demonstrably exploitable bugs including those in the interpreter and most in the runtime libraries. Our results also demonstrated the promising scalability and cost-effectiveness of PyRTFuzz and its great potential for further bug discovery. The two-level collaborative fuzzing methodology instantiated in PyRTFuzz may also apply to other language runtimes especially those of interpreted languages.

Developing a software project using multiple languages together has been a dominant practice for years. Yet it remains unclear what issues developers encounter during the development, which challenges cause the issues, and what solutions developers receive. In this paper, we aim to answer these questions via a study on developer discussions on Stack Overflow. By manually analyzing 586 highly relevant posts spanning 14 years, we observed a large variety (11 categories) of issues, dominated by those with interfacing and data handling among different languages. Behind these issues, we found that a major challenge developers faced is the diversity and complexity in multilingual code building and interoperability. Another key challenge lies in developers' lack of particular technical background on the diverse features of various languages (e.g., threading and memory management mechanisms). Meanwhile, Stack Overflow itself served as a key source of solutions to these challenges-the majority (73%) of the posts received accepted answers eventually, and most in a week (36.5% within 24 hours and 25% in the next 6 days). Based on our findings on these issues, challenges, and solutions, we provide actionable insights and suggestions for both multi-language software researchers and developers.

Analyzing multilingual code holistically is key to systematic quality assurance of real-world software which is mostly developed in multiple computer languages. Toward such analyses, state-of-the-art approaches propose an almost-fully language-agnostic methodology and apply it to dynamic dependence analysis/slicing of multilingual code, showing great promises. We investigated this methodology through a technical analysis followed by a replication study applying it to 10 real-world multilingual projects of diverse language combinations. Our results revealed critical practicality (i.e., having the levels of efficiency/scalability, precision, and extensibility to various language combinations for practical use) challenges to the methodology. Based on the results, we reflect on the underlying pitfalls of the language-agnostic design that leads to such challenges. Finally, looking forward to the prospects of dynamic analysis for multilingual code, we identify a new research direction towards better practicality and precision while not sacrificing extensibility much, as supported by preliminary results. The key takeaway is that pursuing fully language-agnostic analysis may be both impractical and unnecessary, and striving for a better balance between language independence and practicality may be more fruitful.