Arms length

What this C++ memory-layout interview question tests

This is a hard systems-level question about cache-line alignment and data-member placement in C++. It probes whether you understand how the compiler lays out class members in memory, and how to exert control over that layout when performance matters.

High-frequency trading and systems programming teams ask questions like this to identify candidates who can reason about memory hierarchies and false sharing. The question rewards knowledge of a specific C++ language feature that lets you enforce separation of adjacent data members, ensuring they land on different cache lines rather than sharing one and causing contention under concurrent access.

• Cache-line size and false sharing
• Memory alignment attributes and specifiers
• Compiler directives vs. language operators
• Performance implications of data layout in multi-threaded code