Re: Turn off checks in dynamic_cast of reference types in release builds

[Erik <esigra at gmail dot com>]

Ian Lance Taylor skrev:
> Erik <esigra@gmail.com> writes:
>
>   
>> Bjarne Stroustrup wrote in his book The C++ programming language that;
>> while a dynamic_cast to a pointer type is a question (the result should
>> be checked), a dynamic_cast to a reference type is like an assertion. We
>> have followed this advice in our project. Now we need to disable these
>> assertions in release builds, so that dynamic_cast<Derived &>(base) is
>> just as efficient as static_cast<Derived &>(base). But I do not know how
>> to tell this to the compiler. I only found some other checks in gcc,
>> that can be disabled for release builds, such as the Ada checks (-gnatp).
>>     
>
> -Ddynamic_cast=static_cast ?
>   
That would of course not work, because it would affect all
dynamic_casts, not just those to references.


>> Or is the feature that I need missing in gcc? Maybe I have to use one of
>> the many hacks called down_cast, safe_cast and so on, that can be found
>> on the web? Like this one:
>> http://smolsky.net/index.php/2009/09/14/down_cast-v2
>> If so, which of those hacks is the correct one that should be used?
>>     
>
> Since you don't care about dynamic type safety you can just use
> static_cast.
>   

That would certainly not work, because then the assertions in the form
of dynamic_casts to reference types would not be checked in debug builds.