An approach to safely evolve preprocessor-based C program families.

Desde os anos 70, o pré-processador C é amplamente utilizado na prática para adaptar sistemas para diferentes plataformas e cenários de aplicação. Na academia, no entanto, o pré-processador tem recebido fortes críticas desde o início dos anos 90. Os pesquisadores têm criticado a sua falta de modularidade, a sua propensão para introduzir erros sutis e sua ofuscação do código fonte. Para entender melhor os problemas de usar o pré-processador C,considerando a percepção dos desenvolvedores, realizamos 40 entrevistas e uma pesquisa entre 202 desenvolvedores. Descobrimos que os desenvolvedores lidam com três problemas comuns na prática: erros relacionados à configuração, testes combinatórios e compreensão do código. Os desenvolvedores agravam estes problemas ao usar diretivas não disciplinadas, as quais não respeitam a estrutura sintática do código. Para evoluir famílias de programas de forma segura, foram propostas duas estratégias para a detecção de erros relacionados à configuração e um conjunto de 14 refatoramentos para remover diretivas não disciplinadas. Para lidar melhor com a grande quantidade de configurações do código fonte, a primeira estratégia considera todo o conjunto de configurações do código fonte e a segunda estratégia utiliza amostragem. Para propor um algoritmo de amostragem adequado, foram comparados 10 algoritmos com relação ao esforço (número de configurações para testar) e capacidade de detecção de erros (número de erros detectados nas configurações da amostra). Com base nos resultados deste estudo, foi proposto um algoritmo de amostragem. Estudos empíricos foram realizados usando 40 sistemas C do mundo real. Detectamos 128 erros relacionados à configuração, enviamos 43 correções para erros ainda não corrigidos e os desenvolvedores aceitaram 65% das correções. Os resultados de nossa pesquisa mostram que a maioria dos desenvolvedores preferem usar a versão refatorada,ou seja,disciplinada do código fonte,ao invés do código original com as diretivas não disciplinadas. Além disso,os desenvolvedores aceitaram 21 (75%) das 28 sugestões enviadas para transformar diretivas não disciplinadas em disciplinadas. Nossa pesquisa apresenta resultados úteis para desenvolvedores de código C durante suas tarefas de desenvolvimento, contribuindo para minimizar o número de erros relacionados à configuração, melhorar a compreensão e a manutenção do código fonte e orientar os desenvolvedores para realizar testes combinatórios.Since the 70s, the C preprocessor is still widely used in practice in a numbers of projects, including Apache,Linux ,and Libssh, totail or systems to different platforms and application scenarios. In academia,however, the preprocess or has received strong critic is msinceatl east the early 90s. Researchers have criticized its lack of separation of concerns, its proneness to introduce subtle errors, and its obfuscation of the source code. To better understand the problems of using the C preprocessor, taking the perception of developers into account, we conducted 40 interviewsandasurveyamong 202 developers. We found that developers deal with three common problems in practice: configuration-related bugs, combinatorial testing, and code comprehension. Developers aggravate these problems when using undisciplined directives (i.e., bad smells regarding preprocessor use), which are preprocessor directives thatdo notrespect thesyntactic structureof thesource code. To safely evolve preprocessor based program families, we proposed strategies to detect configuration-relatedbugs and bad smells, and a set of 14 refactorings to remove bad smells. To better deal with exponential configuration spaces, our strategies uses variability-aware analysis that considers the entire set of possible configurations, and sampling, which allows to reuse C tools that consider only one configuration at a time to detect bugs. To propose a suitable sampling algorithm, we compared 10 algorithms with respect to effort (i.e., number of configurations to test) andbug-detection capabilities (i.e.,numberofbugs detected in the sampled configurations). Based on the results, we proposed a sampling algorithm with an useful balance between effort and bug-detection capability. We performed empirical studies using a corpus of 40 C real-world systems. We detected 128 configuration-related bugs, submitted 43 patches to fix bugs not fixed yet, and developers accepted 65% of the patches. The results of our survey show that most developers prefer to use the refactored (i.e., disciplined) version of the code instead of the original code with undisciplined directives. Furthermore, developers accepted 21 (75%) out of 28 patches submitted to refactor undisciplined into disciplined directives. Our work presents useful findings for C developers during their development tasks, contributing to minimize the chances of introducing configuration-related bugs and bad smells, improve code comprehension, and guide developers to perform combinatorial testing

Consistent View-Based Management of Variability in Space and Time

Systeme entwickeln sich schnell weiter und existieren in verschiedenen Variationen, um unterschiedliche und sich ändernde Anforderungen erfüllen zu können. Das führt zu aufeinanderfolgenden Revisionen (Variabilität in Zeit) und zeitgleich existierenden Produktvarianten (Variabilität in Raum). Redundanzen und Abhängigkeiten zwischen unterschiedlichen Produkten über mehrere Revisionen hinweg sowie heterogene Typen von Artefakten führen schnell zu Inkonsistenzen während der Evolution eines variablen Systems. Die Bewältigung der Komplexität sowie eine einheitliche und konsistente Verwaltung beider Variabilitätsdimensionen sind wesentliche Herausforderungen, um große und langlebige Systeme erfolgreich entwickeln zu können. Variabilität in Raum wird primär in der Softwareproduktlinienentwicklung betrachtet, während Variabilität in Zeit im Softwarekonfigurationsmanagement untersucht wird. Konsistenzerhaltung zwischen heterogenen Artefakttypen und sichtbasierte Softwareentwicklung sind zentrale Forschungsthemen in modellgetriebener Softwareentwicklung. Die Isolation der drei angrenzenden Disziplinen hat zu einer Vielzahl von Ansätzen und Werkzeugen aus den unterschiedlichen Bereichen geführt, was die Definition eines gemeinsamen Verständnisses erschwert und die Gefahr redundanter Forschung und Entwicklung birgt. Werkzeuge aus den verschiedenen Disziplinen sind oftmals nicht ausreichend integriert und führen zu einer heterogenen Werkzeuglandschaft sowie hohem manuellen Aufwand während der Evolution eines variablen Systems, was wiederum der Systemqualität schadet und zu höheren Wartungskosten führt. Basierend auf dem aktuellen Stand der Forschung in den genannten Disziplinen werden in dieser Dissertation drei Kernbeiträge vorgestellt, um den Umgang mit der Komplexität während der Evolution variabler Systeme zu unterstützten. Das unifizierte konzeptionelle Modell dokumentiert und unifiziert Konzepte und Relationen für den gleichzeitigen Umgang mit Variabilität in Raum und Zeit basierend auf einer Vielzahl ausgewählter Ansätze und Werkzeuge aus der Softwareproduktlinienentwicklung und dem Softwarekonfigurationsmanagement. Über die bloße Kombination vorhandener Konzepte hinaus beschreibt das unifizierte konzeptionelle Modell neue Möglichkeiten, beide Variabilitätsdimensionen zueinander in Beziehung zu setzen. Die unifizierten Operationen verwenden das unifizierte konzeptionelle Modell als Datenstruktur und stellen die Basis für operative Verwaltung von Variabilität in Raum und Zeit dar. Die unifizierten Operationen werden basierend auf einer Analyse diverser Ansätze konzipiert, welche verschiedene Modalitäten und Paradigmen verfolgen. Während die unifizierten Operationen die Funktionalität von analysierten Werkzeugen abdecken, ermöglichen sie den gleichzeitigen Umgang mit beiden Variabilitätsdimensionen. Der unifizierte Ansatz basiert auf den vorhergehenden Beiträgen und erweitert diese um Konsistenzerhaltung. Zu diesem Zweck wurden Typen von variabilitätsspezifischen Inkonsistenzen identifiziert, die während der Evolution variabler heterogener Systeme auftreten können. Der unifizierte Ansatz ermöglicht automatisierte Konsistenzerhaltung für eine ausgewählte Teilmenge der identifizierten Inkonsistenztypen. Jeder Kernbeitrag wurde empirisch evaluiert. Zur Evaluierung des unifizierten konzeptionellen Modells und der unifizierten Operationen wurden Expertenbefragungen durchgeführt, Metriken zur Bewertung der Angemessenheit einer Unifizierung definiert und angewendet, sowie beispielhafte Anwendungen demonstriert. Die funktionale Eignung des unifizierten Ansatzes wurde mittels zweier Realweltfallstudien evaluiert: Die häufig verwendete ArgoUML-SPL, die auf ArgoUML basiert, einem UML-Modellierungswerkzeug, sowie MobileMedia, eine mobile Applikation für Medienverwaltung. Der unifizierte Ansatz ist mit dem Eclipse Modeling Framework (EMF) und dem Vitruvius Ansatz implementiert. Die Kernbeiträge dieser Arbeit erweitern das vorhandene Wissen hinsichtlich der uniformen Verwaltung von Variabilität in Raum und Zeit und verbinden diese mit automatisierter Konsistenzerhaltung für variable Systeme bestehend aus heterogenen Artefakttypen

Consistent View-Based Management of Variability in Space and Time

Developing variable systems faces many challenges. Dependencies between interrelated artifacts within a product variant, such as code or diagrams, across product variants and across their revisions quickly lead to inconsistencies during evolution. This work provides a unification of common concepts and operations for variability management, identifies variability-related inconsistencies and presents an approach for view-based consistency preservation of variable systems

Consistent View-Based Management of Variability in Space and Time

Developing variable systems faces many challenges. Dependencies between interrelated artifacts within a product variant, such as code or diagrams, across product variants and across their revisions quickly lead to inconsistencies during evolution. This work provides a unification of common concepts and operations for variability management, identifies variability-related inconsistencies and presents an approach for view-based consistency preservation of variable systems

Fundamental Approaches to Software Engineering

This open access book constitutes the proceedings of the 24th International Conference on Fundamental Approaches to Software Engineering, FASE 2021, which took place during March 27–April 1, 2021, and was held as part of the Joint Conferences on Theory and Practice of Software, ETAPS 2021. The conference was planned to take place in Luxembourg but changed to an online format due to the COVID-19 pandemic. The 16 full papers presented in this volume were carefully reviewed and selected from 52 submissions. The book also contains 4 Test-Comp contributions

Fundamental Approaches to Software Engineering

This open access book constitutes the proceedings of the 23rd International Conference on Fundamental Approaches to Software Engineering, FASE 2020, which took place in Dublin, Ireland, in April 2020, and was held as Part of the European Joint Conferences on Theory and Practice of Software, ETAPS 2020. The 23 full papers, 1 tool paper and 6 testing competition papers presented in this volume were carefully reviewed and selected from 81 submissions. The papers cover topics such as requirements engineering, software architectures, specification, software quality, validation, verification of functional and non-functional properties, model-driven development and model transformation, software processes, security and software evolution

Methodology and Ecosystem for the Design of a Complex Network ASIC

Performance of HPC systems has risen steadily. While the 10 Petaflop/s barrier has been breached in the year 2011 the next large step into the exascale era is expected sometime between the years 2018 and 2020. The EXTOLL project will be an integral part in this venture. Originally designed as a research project on FPGA basis it will make the transition to an ASIC to improve its already excelling performance even further. This transition poses many challenges that will be presented in this thesis. Nowadays, it is not enough to look only at single components in a system. EXTOLL is part of complex ecosystem which must be optimized overall since everything is tightly interwoven and disregarding some aspects can cause the whole system either to work with limited performance or even to fail. This thesis examines four different aspects in the design hierarchy and proposes efficient solutions or improvements for each of them. At first it takes a look at the design implementation and the differences between FPGA and ASIC design. It introduces a methodology to equip all on-chip memory with ECC logic automatically without the user’s input and in a transparent way so that the underlying code that uses the memory does not have to be changed. In the next step the floorplanning process is analyzed and an iterative solution is worked out based on physical and logical constraints of the EXTOLL design. Besides, a work flow for collaborative design is presented that allows multiple users to work on the design concurrently. The third part concentrates on the high-speed signal path from the chip to the connector and how it is affected by technological limitations. All constraints are analyzed and a package layout for the EXTOLL chip is proposed that is seen as the optimal solution. The last part develops a cost model for wafer and package level test and raises technological concerns that will affect the testing methodology. In order to run testing internally it proposes the development of a stand-alone test platform that is able to test packaged EXTOLL chips in every aspect