القائمة
Mastering C++ Const Correctness and Mutability. Triggers: const, mutable, logically const, bitwise const, data race, mutex, shared_mutex, thread safety.
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Mastering C++ Ownership: Move Semantics, RAII, and Reference Safety. Triggers: std::move, use-after-free, double-free, dangling pointer, copy elision, RVO, reference qualifiers.
Mastering C++ Smart Pointers: unique_ptr, shared_ptr, weak_ptr. Triggers: memory management, cycles, enable_shared_from_this, make_unique, make_shared, custom deleters.
Mastering C++ Polymorphism: Templates, Concepts, and Virtual Functions. Triggers: templates, concepts, vtable, CRTP, static polymorphism, dynamic polymorphism, SFINAE.
Mastering C++ Type-Driven Design. Triggers: strong types, phantom types, type state pattern, builder pattern, invalid state unrepresentable.
Mastering C++ Error Handling. Triggers: exceptions, try-catch, noexcept, std::expected, std::optional, error codes, assert, terminate.
| name | m03-mutability |
| description | Mastering C++ Const Correctness and Mutability. Triggers: const, mutable, logically const, bitwise const, data race, mutex, shared_mutex, thread safety. |
Who is allowed to change this state?
C++ defaults to Mutable. You must opt-in to safety with const.
const methods promise not to change visible state.mutable to change hidden state (like caches) inside const methods.| Issue | Design Question |
|---|---|
| Discarded qualifiers | Are you trying to modify member data in a const function? |
| Data Race | Did you modify a mutable field from multiple threads without locking? |
| Iterator Invalidation | Are you modifying a container while reading it? |
Should this be const?
const or constexpr.const T* (ptr to const) vs T* const (const ptr).Is internal state 'invariant' or 'cache'?
mutable + std::mutex.Is it thread-safe?
const methods implies safe for concurrent readers.mutable members MUST be protected by synchronization in const methods.Trace Up:
const method modified a mutable cache without a lock, assuming const meant safe.std::mutex to the class, lock it in the const method.Trace Down:
std::shared_mutex allowing multiple readers (shared_lock) and one writer (unique_lock).| Keyword | Meaning | Use When |
|---|---|---|
const | Read-only access | Parameters, local vars, getters. |
constexpr | Compile-time constant | Constants, array sizes. |
mutable | Modifiable in const | Caches, Mutexes within a class. |
std::mutex | Exclusive Lock | Protecting mutable state. |
std::shared_mutex | Read/Write Lock | Rare updates, frequent reads. |