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What this C++ concurrency interview question tests

This is an easy concurrency question that probes understanding of the compare_exchange_weak operation on atomic types in C++. It targets candidates' awareness of a subtle but critical behaviour: spurious failure, where a compare-and-swap instruction can report failure even when the expected value matches the current value.

The question asks you to identify the correct pattern for guarding against spurious failure in a real code snippet. Firms like Intel ask this to ensure candidates writing lock-free code understand the difference between weak and strong compare-exchange operations, and know when (and how) to retry atomically.

• Weak vs. strong atomic compare-exchange semantics
• Loop patterns for atomic operations
• Memory ordering and synchronisation