Mutable shared state
Mutable shared state is data or computational state that multiple components or execution contexts can access and whose value can change over time.
C++ Concurrency in Action, Second Edition
Shared mutable data is information accessible by multiple threads that can also be modified during execution.
- How it is used
- Coordinates access to data shared between threads and highlights the rules needed to avoid concurrency bugs.
- How deep it goes
- Explains mutex protection, encapsulation, and pointer or reference backdoors through a shared-list example.
- Examples
- Uses an apartment-sharing analogy and a shared std::list<int> protected during list operations.
- What you can do after
- Apply std::mutex and std::lock_guard to guard shared-list operations, while designing interfaces that do not leak pointers or references.
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100 Go Mistakes and How to Avoid Them
Mutable shared state is data that can be modified and is accessible by multiple parts of a program or concurrent executions.
- How it is used
- Controls time-dependent cache trimming in tests by making the current time replaceable.
- How deep it goes
- Explains how a global clock couples tests, then contrasts struct-level clock injection with caller-supplied timestamps.
- Examples
- Uses a cache that trims timestamped events, a global clock variable, and a fixed-time test dependency.
- What you can do after
- Apply clock injection or caller-supplied cutoffs to make time-dependent tests deterministic and isolated.
Read how 100 Go Mistakes and How to Avoid Them explains mutable shared state →
Related concepts
- integration testused by · An integration test evaluates whether multiple software components, or a component and an external dependency, interact and behave correctly together.
- threadused by · A thread is an independently schedulable sequence or context of execution within a program or process.
- actorused by · An actor is an independent entity or participant that performs actions, maintains or pursues state or goals, and interacts with other entities or systems.
- synchronizationconfigured by · Synchronization coordinates operations, events, clocks, data, or states to establish required timing, ordering, visibility, or consistency relationships.
- immutable collectionaddressed by · An immutable collection is a collection whose membership and contents cannot be changed after creation.
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