What Does It Mean For a C++ Function To Be Inline?

Question

See title: what does it mean for a C++ function to be inline?

Answer 1

Calling a function imposes a certain performance penalty for the CPU over just having a linear stream of instructions. The CPU's registers have to be written to another location, etc. Obviously the benefits of having functions usually outweigh the performance penalty. But, where performance will be an issue, for example the fabled 'inner loop' function or some other bottleneck, the compiler can insert the machine code for the function into the main stream of execution instead of going through the CPU's tax for calling a function.