Is `const` in C 11 Enough to Guarantee Thread Safety?

The True Meaning of Const in C 11 for Thread-Safety

Does const mean thread-safe in C 11?

In a limited sense, yes. The Standard Library expects operations on const objects to be thread-safe, meaning it won't induce data races. However, this is a contract that can be broken, leading to undefined behavior.

Equivalence to Java's synchronized?

No. Unlike synchronized, which enforces exclusive access, const only indicates the expectation of thread-safety. Internal synchronization must be implemented explicitly.

Understanding const for Thread-Safety

• const ensures thread-safety for read-only operations, as there's no possibility of data races.
• However, for operations that potentially modify data, such as caching, synchronization is necessary to maintain thread-safety.

Example: Thread-Safe Area Calculation

To ensure thread-safety in a rect class with area caching, one must internally synchronize write operations, even within a const function. This honors the contract with the Standard Library.

Keyword Scarcity in C

Yes, C has a limited number of keywords. This has been a known limitation since its inception.

Conclusion

While const somewhat implies thread-safety when used with the Standard Library, it's crucial to understand its limitations and ensure proper synchronization for truly thread-safe code. The scarcity of keywords in C has historically constrained its expressive power.

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