Replace all the functions!

What this C++ language-feature question tests

This is a straightforward C++ language knowledge question that probes familiarity with compiler optimisation directives. It asks you to identify the keyword that instructs the compiler to eliminate the overhead of a function call by substituting the function body directly into the calling code.

Understanding this mechanism is fundamental to writing performant C++ in latency-sensitive environments. Quant trading systems often rely on these low-level optimisations to keep inner loops tight. The question rewards precise knowledge of the language rather than deep algorithmic thinking.

• Inline function semantics and when the compiler honours the directive
• Trade-offs between code size and execution speed
• Compiler heuristics for inlining decisions