Money laundering 2

What this C++ compiler-optimization interview question tests

This is a medium-difficulty question that probes your understanding of how modern C++ compilers reason about undefined behavior and side effects. It sits at the intersection of language semantics and compiler optimization — a critical area for systems engineers and anyone writing performance-sensitive code.

To answer correctly, you need to reason carefully about what the C++ standard permits a compiler to do when it encounters certain patterns. The question rewards candidates who can distinguish between what code looks like it should do and what it's actually allowed to do under aggressive optimization. This is especially relevant in competitive programming and low-latency trading systems, where unexpected behavior can be costly.

• Undefined behavior and the as-if rule
• Compiler freedom under the C++ standard
• Side effects and observable behavior
• Optimization passes and their legal bounds