Exceptional C++ Style 40 New Engineering Puzzles, Programming Problems, and Solutions

Chapter 24. Constant Optimization?

Difficulty: 3

Does const correctness help the compiler optimize code? A typical programmer's reaction is that, yes, they suppose it probably does. Which brings us to the interesting thing…

JG Question

1. Consider the following code:

   const Y& f(const X& x) {
   
    // … do something with x and find a Y object …
   
    return someY;
   
   }
   

   Does declaring the parameter and/or the return value as const help the compiler generate more optimal code or otherwise improve its code generation? Why or why not?

Guru Question

1. In general, explain why or why not the presence or absence of const can help the compiler enhance the code it generates.

2. Consider the following code:

   void f(const Z z) {
   
    // ...
   
   }
   

   The questions:

   1. Under what circumstances and for what ...