Safe Programming Research Articles

Safe and Reliable Software

Abstract Pankaj Gupta FBCS examines the importance of Memory Safe Programming and why it is increasingly regarded as necessary.

Safe Adaptive Dynamic Programming for Multiplayer Systems With Static and Moving No-Entry Regions

Safe Adaptive Dynamic Programming for Multiplayer Systems With Static and Moving No-Entry Regions

"If I want to be able to keep going, I must be active." Exploring older adults' perspectives of remote physical activity supports: a mixed-methods study.

Pandemic-related public health restrictions limited older adults' physical activity programs and opportunities. Physical activity supports shifted to remote options, however, information on their adoption and effectiveness is limited. This study aims to describe the remote supports received by older adults and their perceived effectiveness. Additionally, it aims to describe facilitators and barriers to remote supports for physical activity among older adults, particularly those reliant on technology. This study used an explanatory, sequential, mixed-methods design. Community-dwelling older adults (≥ 60 years) were recruited to partake in a web-based survey and an optional semi-structured follow-up interview informed by the COM-B model. Participant characteristics, perceived effectiveness of remote supports, and the presence and severity of barriers were described. Changes in physical activity levels before and during the pandemic were analyzed using the Wilcoxon signed-rank test. Qualitative data underwent inductive thematic analysis. Fifty seven older adults (68.3 ± 7.1 years, 43 Female) completed the survey, of which 15 participants (67.4 ± 5.8 years, 12 Female) participated in interviews. The majority were Caucasian, highly educated, and resided in Canada. Total physical activity levels showed no statistically significant change from before to during the pandemic (p = 0.74); however, at-home exercise participation and technology usage increased. Pre-recorded and real-time virtual exercise supports were perceived as most effective. Main barriers included limited contact with exercise professionals, limited access to exercise equipment or space, and decreased mental wellness. Thematic analysis identified five main themes: (i) Enabled by knowledge and resources; (ii) Diverse motivations for physical activity; (iii) Fostering participation through social connection; (iv) Supervision and safety: enabling adherence; and (v) Virtual exercise: a sustainable option with technological considerations. Virtual platforms show promise in supporting older adults' physical activity at home, especially for those with limited in-person access. Our study suggests that both real-time and pre-recorded virtual exercise supports are feasible, depending on technological capacity and support. While interactive real-time virtual programs allow interaction with professionals and peers, pre-recorded programs provide timing flexibility. Further research is needed to establish best practices for safe and effective virtual exercise programming, promoting its long-term adoption for supporting a wider range of older adults.

Polymorphic Reachability Types: Tracking Freshness, Aliasing, and Separation in Higher-Order Generic Programs

Fueled by the success of Rust, many programming languages are adding substructural features to their type systems. The promise of tracking properties such as lifetimes and sharing is tremendous, not just for low-level memory management, but also for controlling higher-level resources and capabilities. But so are the difficulties in adapting successful techniques from Rust to higher-level languages, where they need to interact with other advanced features, especially various flavors of functional and type-level abstraction. What would it take to bring full-fidelity reasoning about lifetimes and sharing to mainstream languages? Reachability types are a recent proposal that has shown promise in scaling to higher-order but monomorphic settings, tracking aliasing and separation on top of a substrate inspired by separation logic. However, naive extensions on top of the prior reachability type system λ * with type polymorphism and/or precise reachability polymorphism are unsound, making λ * unsuitable for adoption in real languages. Combining reachability and type polymorphism that is precise, sound, and parametric remains an open challenge. This paper presents a rethinking of the design of reachability tracking and proposes new polymorphic reachability type systems. We introduce a new freshness qualifier to indicate variables whose reachability sets may grow during evaluation steps. The new system tracks variables reachable in a single step and computes transitive closures only when necessary, thus preserving chains of reachability over known variables that can be refined using substitution. These ideas yield the simply-typed λ ✦ -calculus with precise lightweight, i.e., quantifier-free, reachability polymorphism, and the F <: ✦ -calculus with bounded parametric polymorphism over types and reachability qualifiers, paving the way for making true tracking of lifetimes and sharing practical for mainstream languages. We prove type soundness and the preservation of separation property in Coq. We discuss various applications (e.g., safe capability programming), possible effect system extensions, and compare our system with Scala’s capture types.

Exercise Training in Non-Hospitalized Patients with Post-COVID-19 Syndrome-A Narrative Review.

Post COVID-19 Syndrome (PCS) is the persistence of symptoms after an infection with SARS-CoV-2 in both hospitalized and non-hospitalized COVID-19 survivors. Exercise was proposed as a rehabilitation measure for PCS and early studies focused on patients post-hospital discharge. The objective of this review is to summarize the results of trials investigating exercise interventions in non-hospitalized subjects with PCS and propose practical recommendations concerning safe exercise programming. A literature search in the databases MEDLINE and Scopus was conducted until 26 July 2023 and resulted in seven studies that met the criteria. In total, 935 subjects with PCS were investigated. Exercise enhanced aerobic fitness and physical function and relieved symptoms of dyspnea, fatigue and depression. Participants reported lower Post COVID-19 Functional Status scores post-intervention. The exercise programs were well tolerated with no adverse events. To ensure safety, medical examinations should take place in advance and there should be a regular evaluation of the individual responses to the training. Caution is advised when working with patients suffering from post-exertional malaise or diagnosed with myalgic encephalomyelitis/chronic fatigue syndrome. There is a growing need for additional randomized controlled trials to investigate the effectiveness and safety of exercise in individuals with PCS.

A Tag-Based Solution for Safer Parallel STL Usage

Abstract The continuous evolution of programming languages creates a challenge not only for the compiler implementers but also for the regular developers. The C++17 standard introduced the Parallel STL library, a parallel extension of the original and fundamental Standard Template Library (STL) with the promise to achieve safe, efficient, and scalable parallel programming in an easy way. While the syntax remained familiar, the new parallel algorithms introduced additional requirements, which are often ignored even by experienced programmers. In this paper, we investigate the root cause of the misuse of the Parallel STL. We carried out a classroom experiment to measure the programmers’ behaviour when programming using the Parallel STL and found that the major issue is not that their code would be erroneous, but the lack of awareness of the semantic requirements of parallel functors. While a fully automatic detection of erroneous constructs is computationally infeasible to achieve, we introduce a framework with which the developer will be able to indicate – axiomatically, based on absolute trust – that an operation has “safe” properties required by the algorithms. We implemented a prototype of the proposed framework to demonstrate its usability and effectiveness.

Pbqff: Push-Button Quartic Force Fields.

pbqff is an open-source program for fully automating the production of quartic force fields (QFFs) and their corresponding anharmonic spectroscopic data. Rather than being a monolithic piece of code, it consists of several key modules including a generic interface to quantum chemistry codes and, notably, queuing systems; a molecular point group symmetry library; an internal-to-Cartesian coordinate conversion module; a module for the ordinary least-squares fitting of potential energy surfaces; and an improved second-order rotational and vibrational perturbation theory package for asymmetric and symmetric tops that handles type-1 and -2 Fermi resonances, Fermi resonance polyads, and Coriolis resonances. All of these pieces are written in Rust, a modern, safe, and performant programming language that has much to offer for scientific programming. This work introduces pbqff and its surrounding ecosystem, in addition to reporting new anharmonic vibrational data for c-(C)C3H2 and describing how the components of pbqff can be leveraged in other projects.

Aliasing Limits on Translating C to Safe Rust

The Rust language was created to provide safe low-level systems programming. There is both industrial and academic interest in the problem of (semi-)automatically translating C code to Rust in order to exploit Rust's safety guarantees. We study the effectiveness and limitations of existing techniques for automatically translating unsafe raw pointers (in Rust programs translated from C) into safe Rust references via ownership and lifetime inference. Our novel evaluation methodology enables our study to extend beyond prior studies, and to discover new information contradicting the conclusions of prior studies. We find that existing translation methods are severely limited by a lack of precision in the Rust compiler's safety checker, causing many safe pointer manipulations to be labeled as potentially unsafe. Leveraging this information, we propose methods for improving translation, based on encoding the results of a more precise analysis in a manner that is understandable to an unmodified Rust compiler. We implement one of our proposed methods, increasing the number of pointers that can be translated to safe Rust references by 75% over the baseline (from 12% to 21% of all pointers).

Does Sex Improve With Experience?: A Latent Transition Analysis of College Students' Penile-Vaginal Sex-related Consequences.

Sex researchers have primarily focused on first penile-vaginal sex and negative consequences. However, because sexual behaviors and attitudes change with age, sex-related consequences may also change. In this study, 275 college students reported on penile-vaginal sex-related consequences the prior day in 733 daily diaries across two or more semesters. Participants were primarily female (63%) and heterosexual (98%). The sample was racially and ethnically diverse, with 30% identifying as Hispanic and, of the non-Hispanic participants, 35% White, 24% Black/African American, 20% Asian-American/Alaskan Native, 2% American Indian, and 2% Hawaiian/Pacific Islander. During their first semester, participants were, on average, 18.4 years old (SD = 0.4). Latent class analysis identified three classes: High Positive (56%), Intimacy and Satisfaction Only (34%), and Moderate Positive With Health Concerns (10%). Over time, students were likely to transition out of the Moderate Positive With Health Concerns and High Positive classes, and into the Intimacy and Satisfaction Only class. The findings suggest that discussing protection from health concerns and positive aspects of sexuality may lead to better student engagement in safe sex programming.

Health education after COVID-19: A time to revisit, revamp, and revitalize?

The educational system plays an integral role in equipping the next generation with the knowledge, skills, and resources needed to flourish as productive citizens. Health education class is a fundamental tool to ensure that students are health literate and encouraged to uptake healthy lifestyles.1 Health education class also serves as a location for intervention, such as student-focused nutrition, drug use prevention, and safe sex programming.2 Unfortunately, the current health education curriculum exemplifies a reactive model of health by focusing - often disproportionately - on individual health topics.

Intrinsically-typed definitional interpreters à la carte

Specifying and mechanically verifying type safe programming languages requires significant effort. This effort can in theory be reduced by defining and reusing pre-verified, modular components. In practice, however, existing approaches to modular mechanical verification require many times as much specification code as plain, monolithic definitions. This makes it hard to develop new reusable components, and makes existing component specifications hard to grasp. We present an alternative approach based on intrinsically-typed interpreters, which reduces the size and complexity of modular specifications as compared to existing approaches. Furthermore, we introduce a new abstraction for safe-by-construction specification and composition of pre-verified type safe language components: language fragments . Language fragments are about as concise and easy to develop as plain, monolithic intrinsically-typed interpreters, but require about 10 times less code than previous approaches to modular mechanical verification of type safety.

Practical generic programming over a universe of native datatypes

Datatype-generic programming makes it possible to define a construction once and apply it to a large class of datatypes. It is often used to avoid code duplication in languages that encourage the definition of custom datatypes, in particular state-of-the-art dependently typed languages where one can have many variants of the same datatype with different type-level invariants. In addition to giving access to familiar programming constructions for free, datatype-generic programming in the dependently typed setting also allows for the construction of generic proofs. However, the current interfaces available for this purpose are needlessly hard to use or are limited in the range of datatypes they handle. In this paper, we describe the design of a library for safe and user-friendly datatype-generic programming in the Agda language. Generic constructions in our library are regular Agda functions over a broad universe of datatypes, yet they can be specialized to native Agda datatypes with a simple one-liner. Furthermore, we provide building blocks so that library designers can too define their own datatype-generic constructions.

From the Editor

I recently reviewed a report performed for the American College of Cardiology (ACC) titled Survey Report: Cardiac Rehab Industry Insights and Best Practices (1). Only a fraction of the cardiac rehabilitation (CR) programs in the United States were assessed (N = 72 of 800+ programs). The survey provided information on a wide array of topics including eligible patient participation, intensive versus traditional CR use (10% and 90%, respectively), the number sessions attended, maintenance program charges, “virtual” CR services (only 13% offering), other offerings (e.g., pulmonary, PAD, oncology), American Association of Cardiovascular and Pulmonary Rehabilitation (AACVPR) program certification (75% certified), program revenues (50% reported positive net revenue), and barriers to growth.Another area of focus was on staffing. Two items related to the reporting of staffing caught my attention. First, and I have mentioned this previously, is the disappointment I had in the listing of “Exercise Physiologist” (EP) and not “Clinical Exercise Physiologist” (CEP). A goal of those individuals who belong to the organizations that allow access to this journal (CEPA, ESSA, and CSEP) should be to promote the specialty of clinical exercise physiology. The American College of Sports Medicine recognizes CEPs and EPs as distinctly separate professionals (2). The CEP is an allied healthcare professional with specific education and practical skills to guide those with existing chronic disease (many who are newly diagnosed and with complex comorbidities) through an exercise and lifestyle modification program. I urge anyone reading this article to recognize the differences between CEPs and EPs, and when the term EP is used when CEP should have been use, please notify the author or organization of this mistake. For example, I recently asked the current president of the AACVPR to change from EP to CEP on their registration to the annual meeting and provided rationale. It was met with acceptance, and he stated they will be making this change.The other area in the staffing section of the ACC CR survey had to do with use of various disciplines for program staffing. It was heartening to read that 95% of programs surveyed employed exercise professionals (stated as EPs in the survey—see above). CR remains the primary location of employment of the CEP, particularly in the United States. Additionally, 89% of the programs reported using a registered nurse. Nursing involvement in CR has been traditional since its inception. However, our program at Henry Ford Hospital has not used nurses for the past 20 years. We have relied solely on appropriately trained and experienced CEPs, with physician support, to implement programming and deal with the variety of medical situations that occur (blood glucose issues, chest pain, hypotensive responses, the need for CPR and/or defibrillation). We have been able to provide safe and effective CR programming in the settings of hospital and standalone clinic while serving an extremely sick and frail population. And this has also included the implementation of several important National Institutes of Health trials (HF-ACTION, CLEVER, iATTEND) (3). Importantly, staffing with only CEPs meets the 2006 Medicare and Medicaid definition for staffing of CR programs (4). I urge you to read the point:counterpoint from the 2015 issue of the Journal of Clinical Exercise Physiology (only 1 issue per year at that time and any article older than 18 months is freely available) in which I debate that the CEP is the best and logical choice for the majority of staffing in CR programs (5). My goal is to continue to promote the primary use of CEPs in all exercise settings catering to those with chronic disease.

Safer Linux Kernel Modules Using the D Programming Language

Since its creation, the Linux kernel has gained international recognition and has been employed on a large range of devices: servers, supercomputers, smart devices and embedded systems. Given its popularity, the security of the kernel has become a critical research topic. As a consequence, a wide range of third party tools were created to detect bugs in its implementation. However, new vulnerabilities are discovered and exploited every year. The explanation for this phenomenon lies in the fact that the programming language that is used for the kernel implementation, C, is designed to allow unsafe memory operations. In this paper, we show that it is possible to incrementally transition the kernel code from C to a memory safe programming language, D, by porting and integrating a device driver. In addition, we propose a series of code transformations that allow the D compiler to reason about the safety of certain memory operations. Our implementation increases the security guarantees of the kernel without incurring any performance penalties.

VIRTUAL, ON-SITE AND HYBRID...HOW DO THE NEW MODELS OF CARDIAC REHAB IN NOVA SCOTIA COMPARE TO THE PRE-COVID PROGRAMS?

BACKGROUND In Nova Scotia (NS) the arrival of COVID-19 led to immediate closures of all cardiac rehabilitation (CR) programs and redeployment of staff. Doors opened again two months later with CR teams needing to quickly develop and implement a virtual version of CR. Months following, with the reduction of COVID cases, programs were transitioned back to in-person on-site/hybrid models. Throughout transitions, the goal was to develop safe, effective and sustainable CR models of care with measured outcomes comparative to core elements of traditional on-site CR. METHODS AND RESULTS The first version of Virtual Cardiac Rehab (VCR 1) was an eight-week program for 99 patients with individual weekly case management calls from the CR team. Two On-Site CR (O-SCR) programs were later implemented;O-SCR1, an 8 week model with 5 patients/class (n=125) and O-SCR 2, a 12 week model with 9 patients per class (n=98). Due to the 2nd wave of COVID in winter 2020, all programming reverted back to virtual care with a new structured VCR2, a 12 week model (n=96) integrating nurses, dietitians and physiotherapists for individual case managed calls, behavior change counselling, Zoom for Healthcare group sessions and rigorous modeling to emulate the physical program as closely as possible, including exercise prescription. In all models; risk factors, medications and medical history were assessed and when possible blood work and exercise stress tests were completed, along with health behaviour change evaluation for activity and eating patterns. There were no adverse events in the virtual groups. 72% of patients completed the VCR1 model with positive changes in eating and activity patterns and effective medical management. 92% of patients completed VCR2 with improved outcome measures including physiologic measures (currently in analysis phase). The O-SCR1 demonstrated 80% attendance, but pandemic restricted stress testing and blood work resulted in most outcome reports as qualitative, based on questionnaires; showing a significant improvement in dietary fat, fibre, sodium and sugar intake patterns, along with 90% of patients reporting improvements in self-management of eating and exercise goals. With O-SCR2, greater stress and lab data availability demonstrates improved exercise tolerance (METS), lipid profiles and food scores. See Results in Table 1. CONCLUSION Keeping CR doors open virtually and on-site can be challenging during a pandemic but the NS models are feasible with measurable outcomes that are comparable to on-site CR when modeled as such. Further modelling continues with building safe, sustainable and effective programming options. In Nova Scotia (NS) the arrival of COVID-19 led to immediate closures of all cardiac rehabilitation (CR) programs and redeployment of staff. Doors opened again two months later with CR teams needing to quickly develop and implement a virtual version of CR. Months following, with the reduction of COVID cases, programs were transitioned back to in-person on-site/hybrid models. Throughout transitions, the goal was to develop safe, effective and sustainable CR models of care with measured outcomes comparative to core elements of traditional on-site CR. The first version of Virtual Cardiac Rehab (VCR 1) was an eight-week program for 99 patients with individual weekly case management calls from the CR team. Two On-Site CR (O-SCR) programs were later implemented;O-SCR1, an 8 week model with 5 patients/class (n=125) and O-SCR 2, a 12 week model with 9 patients per class (n=98). Due to the 2nd wave of COVID in winter 2020, all programming reverted back to virtual care with a new structured VCR2, a 12 week model (n=96) integrating nurses, dietitians and physiotherapists for individual case managed calls, behavior change counselling, Zoom for Healthcare group sessions and rigorous modeling to emulate the physical program as closely as possible, including exercise prescription. In all models; risk factors, medications and medical history were assessed and when possible blood work and exercise stress tests were completed, along with health behaviour change evaluation for activity and eating patterns. There were no adverse events in the virtual groups. 72% of patients completed the VCR1 model with positive changes in eating and activity patterns and effective medical management. 92% of patients completed VCR2 with improved outcome measures including physiologic measures (currently in analysis phase). The O-SCR1 demonstrated 80% attendance, but pandemic restricted stress testing and blood work resulted in most outcome reports as qualitative, based on questionnaires; showing a significant improvement in dietary fat, fibre, sodium and sugar intake patterns, along with 90% of patients reporting improvements in self-management of eating and exercise goals. With O-SCR2, greater stress and lab data availability demonstrates improved exercise tolerance (METS), lipid profiles and food scores. See Results in Table 1. Keeping CR doors open virtually and on-site can be challenging during a pandemic but the NS models are feasible with measurable outcomes that are comparable to on-site CR when modeled as such. Further modelling continues with building safe, sustainable and effective programming options.

GhostCell: separating permissions from data in Rust

The Rust language offers a promising approach to safe systems programming based on the principle of aliasing XOR mutability : a value may be either aliased or mutable, but not both at the same time. However, to implement pointer-based data structures with internal sharing, such as graphs or doubly-linked lists, we need to be able to mutate aliased state. To support such data structures, Rust provides a number of APIs that offer so-called interior mutability : the ability to mutate data via method calls on a shared reference. Unfortunately, the existing APIs sacrifice flexibility, concurrent access, and/or performance, in exchange for safety. In this paper, we propose a new Rust API called GhostCell which avoids such sacrifices by separating permissions from data : it enables the user to safely synchronize access to a collection of data via a single permission. GhostCell repurposes an old trick from typed functional programming: branded types (as exemplified by Haskell’s ST monad), which combine phantom types and rank-2 polymorphism to simulate a lightweight form of state-dependent types. We have formally proven the soundness of GhostCell by adapting and extending RustBelt, a semantic soundness proof for a representative subset of Rust, mechanized in Coq.

Safe systems programming in Rust

The promise and the challenges of the first industry-supported language to master the trade-off between safety and control.

Taming x86-TSO persistency

We study the formal semantics of non-volatile memory in the x86-TSO architecture. We show that while the explicit persist operations in the recent model of Raad et al. from POPL'20 only enforce order between writes to the non-volatile memory, it is equivalent, in terms of reachable states, to a model whose explicit persist operations mandate that prior writes are actually written to the non-volatile memory. The latter provides a novel model that is much closer to common developers' understanding of persistency semantics. We further introduce a simpler and stronger sequentially consistent persistency model, develop a sound mapping from this model to x86, and establish a data-race-freedom guarantee providing programmers with a safe programming discipline. Our operational models are accompanied with equivalent declarative formulations, which facilitate our formal arguments, and may prove useful for program verification under x86 persistency.

Delivering the first internationally accessible Massive Online Open Course (MOOC) on suicide prevention: a case study and insights into best practice

To date, little guidance exists on how to design safe and effective online programming on sensitive and/or controversial topics. Massive online open courses (MOOCs) represent a unique opportunity for delivering inclusive and accessible teaching to international learner audiences. This paper provides an insight into designing and delivering the first internationally accessible MOOC on suicide prevention in the global context in 2019-highlighting insights into best practice as well as pertinent challenges. The results from two runs of this MOOC indicate that there appears to be a global demand for education on suicide prevention. Our practice suggests that new knowledge on extremely sensitive topics such as suicide can be safely and effectively delivered through a MOOC to an international community of learners. Learner safety needs to be carefully considered when developing and delivering online learning. Thorough and careful moderation is essential to ensure that learners engage safely and sensitively with the content and with one another. The involvement of diverse stakeholders, including people with lived experience, in the MOOC design is recommended to enhance the authenticity, inclusiveness and rigour of the curriculum.

Delivering the First Internationally Accessible Massive Online Open Course (MOOC) on Suicide Prevention: A Case Study and Insights into Best Practice

To date, little guidance exists on how to design safe and effective online programming on sensitive and/or controversial topics. Massive online open courses (MOOCs) represent a unique opportunity for delivering inclusive and accessible teaching to international learner audiences. This paper provides an insight into designing and delivering the first internationally accessible MOOC on suicide prevention in the global context in 2019-highlighting insights into best practice as well as pertinent challenges. The results from two runs of this MOOC indicate that there appears to be a global demand for education on suicide prevention. Our practice suggests that new knowledge on extremely sensitive topics such as suicide can be safely and effectively delivered through a MOOC to an international community of learners. Learner safety needs to be carefully considered when developing and delivering online learning. Thorough and careful moderation is essential to ensure that learners engage safely and sensitively with the content and with one another. The involvement of diverse stakeholders, including people with lived experience, in the MOOC design is recommended to enhance the authenticity, inclusiveness and rigour of the curriculum.