## +24 ## Back To Basics Lifetime Management ## PHIL NASH ## 20 24 September 15 - 20 ## C++ is complex  mostly for historical on the stack~T() operator=(T&&)Unique ManagersSingle ownership - can be stored. Expensive or nonsensical to copyRule of Five with disabled copy~T() https://www.sonarsource.com/blog/beyond-the-rules-of-three-five-and-zero/ ## +24 ## Back To Basics Lifetime Management ## PHIL NASH ## 20 24 September 15 - 20

## +23 ## Object Lifetime: From Start to Finish ## THAMARA ANDRADE ## 20 23 October 01 - 06 ## Object Lifetime ## From Start to Finish int main() { if (doSomething(Foo().getBar())) { // realizing I didn’t really understand the rules for object lifetime. ## What is object lifetime anyway? ### 6.8 Object lifetime [basic.life] The lifetime of an object or reference is a runtime property of the Initialization by a trivial copy/move constructor is non-vacuous initialization. — end note] The lifetime of an object of type T begins when: (1.1) — storage with the proper alignment and size for type

## 20 23 October 01 - 06 ## +23 ## Lifetime Safety in C++: Past, Present and Future #### GABOR HORVATH Gabor.Horvath@microsoft.com ## Welcome to CppCon 2023! Come by our booth and join #visual_studio https://aka.ms/cppcon/lifetime 0  Approaches to safety ## ↑ C++ is getting safer The lifetime safety toolbox What nts/9/d/0/5/9d05b80becbd0a2aac297caf075ed3c2/p24_2.jpg) • ASAN, GWP-ASAN, HWASAN + Fuzzing • Lifetime Safety Profile, Crubit • C26815, C26816 • Cyclone, P2771 -Wdangling-gsl -Wdangling-reference

optimization opportunities. ## Container Level Variables Container level variables have static lifetime and are order-independent and lazily analyzed. The initialization value of container level variables tests passed. ## Static Local Variables It is also possible to have local variables with static lifetime by using containers inside functions. static local variable.zig const std = @import("std"); will provide such protection, with some degree of cooperation from Zig code required. ## Lifetime and Ownership It is the Zig programmer's responsibility to ensure that a pointer is not accessed when

and talking about C++ makers.f.dev@gmail.com ## Outline • Motivation • Overview • Patterns • Lifetime • Exceptions • RAII • Synchronization ## • Conclusions ## Motivation • 40 years of • Experience /8/e20839ae14710dcbb38ddda7e6a7f799/p14_1.jpg) ## Patterns • Lifetime • Exceptions • RAII • Synchronization ## Lifetime ## Lifetime • Lots of worries • Use Structured Concurrency $ ^{[1]} $ • https://ericniebler.com/2020/11/08/structured-concurrence/ ## Lifetime Member coroutines implicitly capture this ## Lifetime Let's play a game ## Lifetime struct Bar { int data = 0; Task mul_2(Task

share/vehicle semantics across the set of source files making up a component ## Module Ownership ## Module Ownership - Supporting programming in the large (componentization) - Non-interference between between module-local entities (module linkage) - Interface provenance: - Weak ownership – good - Strong ownership – better - ODR guarantees - An entity is owned by exactly one module - Reachability - Allows implementation freedom to enforce ownership - Throughout the entire toolchain, from parser to linker - MSVC implements a 'strong ownership' model. - Hope: More C++ toolsets offer

breaking the potential ownership cycle Service objects are owned by an ExecutionContext ExecutionContext destroys all services (and therefore completion handlers) as its lifetime ends struct my_service is established lifetime of Executor corresponds to lifetime of outstanding work against the underlying ExecutionContext In case of std::net::io_context::run will not return until lifetime of all such Executor guarantees of Networking TS from scratch Completion handlers must be stored in a Service to avoid ownership cycles Outstanding work must be tracked to ensure underlying ExecutionContext still available upon

} } } } ); Manual lifetime management ## 原生 原生 原生 // read length auto len = make_unique(); async_read(socket .handle data... ## Coroutines may simplify things • Easier reasoning • Easier object lifetime management • Easier error propagation But we need some structure ## Structured concurrency And of the program ## Detached tasks considered harmful No way to figure out task lifetime => no automatic object lifetime management // don't do this void bad(tcp::socket& s) { std::array

in the right direction.” • Agile tie-in: Scrum and the use of time boxes ## The High Price of Ownership – Why We Overvalue What We Have - Example: Duke basketball tickets – students must camp out in transaction from the same perspective as we do.” “Ownership is not limited to material things. It can also apply to points of view. Once we take ownership of an idea—whether its about politics or sports—what

. . 65 3.5 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 66 4 Understanding Ownership 77 4.1 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 77 4.2 . . . . . . . . . as variables, data types, and functions, and shows how to use them in Rust. Chapter 4 explores ownership, which is a Rust feature that is most different from other languages. Chapter 5 discusses structs concept in Rust that doesn’t commonly exist in other programming languages: ownership. 78 Chapter 4 Understanding Ownership Ownership is Rust’s most unique feature, and it enables Rust to make memory safety