Context: Companies adopt many software reuse practices, such as software product line, reuse verbatim, and systematic reuse, to improve their internal software development and maximize the benefits. Contemporary software engineering (SE) practices, such as microservices and InnerSource, influence internal software reuse. Objective: In this thesis, we aim to improve internal software reuse in the context of contemporary SE practices. To do that, we want to 1) understand the state-of-the-art and the state-of-the-practice of software reuse costs and benefits and the challenges that companies are currently facing and 2) identify interventions to improve internal software reuse.  Methods: We conducted a systematic literature review to understand the state-of-the-art of software reuse costs and benefits. We performed two exploratory case studies to understand the state-of-the-practice of software reuse costs and benefits, challenges, and improvement areas in the context of contemporary SE practices.  We performed another follow-up improving case study to investigate the medium-sized case company's readiness of adopting InnerSource for software reuse. Results: Existing literature reported more software reuse benefits than costs. The most reported software reuse benefits are better product quality and improved productivity. Verbatim reuse and systematic reuse result in more reuse benefits. Most of the included primary studies are of moderate quality, with only four having high quality. Practitioners think that software reuse costs in developing reusable assets will be paid off when developers start to reuse them. Challenges in software reuse in the context of contemporary SE practices differ between medium-sized and large-sized companies. Both of the companies perceive that InnerSource can help improve internal software reuse. Asking practitioners about both current and desired InnerSource reuse status helps identify the needed InnerSource improvements, thus helping companies succeed in adopting InnerSource for reuse.   Conclusion: Both existing literature and our two case studies investigating software reuse in the context of contemporary SE practices showed that software reuse improves quality and productivity and has costs in developing and integrating reusable assets. However, the overall benefits outweigh the costs. Both case companies faced challenges in improving their internal reuse, where the most common challenges were about developing and maintaining reusable assets. The results showed that InnerSource helps develop and maintain reusable assets and further improves internal software reuse. / <p>Chapters 2 and 4 are papers submitted to journals and therefore removed from the fulltext file.</p>

Object-oriented languages have made a shift towards incorporating functional concepts such as lambdas. Lambdas are anonymous functions that can be used within the scope of other functions. In C++ lambdas are considered difficult to use for inexperienced developers. This implies that there may be problems with lambdas in C++. However, studies about lambdas in C++ repositories are scarce, compared to other object-oriented languages such as Java. This study aims to address a knowledge gap regarding how lambdas are used by developers in C++ repositories. Furthermore, examine how developer experience and software engineering practices, such as unit testing and in-code documentation, correlates with the inclusion of lambdas. To achieve this we create a set of tools that statically analyse repositories to gather results. This study gained insight into the number of repositories utilising lambdas, their usage areas, and documentation but also how these findings compare to similar studies’ results in Java. Further, it is shown that unit testing and developer experience correlates with the usage of lambdas. / Objektorienterade språk har gjort en förskjutning mot att integrera funktionella begrepp som lambdas. Lambdas är anonyma funktioner som kan användas inom ramen för andra funktioner. I C ++ anses lambdas vara svåra att använda för oerfarna utvecklare. Detta innebär att det kan vara problem med lambdas i C ++. Emellertid är studier på lambdas i C ++ repositorier mindre vanliga jämfört med andra objektorienterade språk som Java. Denna studie syftar till att ta itu med ett kunskapsgap beträffande hur lambdas används av utvecklare i C++ repositorier. Dessutom undersöks hur utvecklarvanor och sedvänjor i programvaruutveckling, till exempel enhetstestning och dokumentation, korrelerar med inkluderingen av lambdas. För att uppnå detta skapar vi en uppsättning verktyg som statiskt analyserar repositorier för att samla resultat. Denna studie fick inblick i antalet repositorier som använder lambdas, deras användningsområden och dokumentation men också hur dessa resultat jämför sig med liknande studieresultat i Java. Vidare har det visats att enhetstestning och utvecklaren erfarenhet korrelerar med användningen av lambdas.