are scope guards (scope(exit, success, failure)) zero-cost abstractions?

[Mike Parker]

On Thursday, 8 February 2018 at 10:09:12 UTC, Timothee Cour wrote:
> I'm curious whether scope guards add any cost over the naive 
> way, eg:
>
> ```
> void fun(){
>   ...
>   scope(success) {bar;}
>   ...
> }
> ```
>
> vs:
>
> ```
> void fun(){
>   ...
>   if(foo1){
>     bar;  // add this before each return
>     return;
>   }
>   ...
>   bar;
>   return;
> }
> ```
>
> For scope(success) and scope(failure), the naive way would 
> anyway
> involve try/catch statements but what about scope(exit)? Does 
> the
> zero-cost exception model (zero cost being for non-thrown 
> exceptions)
> guarantee us that scope(success) has 0 overhead over naive way?

Scope guards are lowered to the equivalent try/catch/finally 
blocks anyway.