Re: [scope] Some random thoughts

From: Andrey Semashev (andrey.semashev_at_[hidden])
Date: 2023-12-02 21:19:55

On 12/2/23 23:12, Andrzej Krzemienski via Boost wrote:
> Hi All,
> Two observations from reading the docs.
> 
> Why do I need a condition in scope_exit when I have a scope_fail?

There is a discussion about this in this section:

https://lastique.github.io/scope/libs/scope/doc/html/scope/scope_guards.html#scope.scope_guards.condition_functions

In short, scope_fail implies processing a failure event (for whatever
definition of "failure") and scope_exit has no such connotation and can
be used with arbitrary conditions. The different scope guards have
different default conditions, too.

Internally, both scope_success and scope_fail are implemented on top of
scope_exit and leverage its support for custom condition functions.

> I recommend putting warning somewhere in the docs that while using scope
> guards you may inadvertently read an object after move:
> 
> std::string checked(std::string name)
> {
>   scope::scope_exit g{[&]{
>     std::clog << "checked " << name <<std::endl;
>   }};
> 
>   validate(name);
>   return name; // name becomes moved-from
> }

Interesting observation, thanks.