Re: [boost] [type_traits] is_base_of<> GCC error for v1.42.0

Subject: Re: [boost] [type_traits] is_base_of<> GCC error for v1.42.0
From: Lorenzo Caminiti (lorcaminiti_at_[hidden])
Date: 2010-05-09 09:07:42

On Sun, May 9, 2010 at 5:04 AM, John Maddock <boost.regex_at_[hidden]> wrote:
>> The following code gives the GCC compiler error below for Boost 1.42.0
>> while it compiles just fine for Boost 1.34.1.
>>
>> Is this a bug in Boost.TypeTraits for 1.42.0?
>
> No it's a feature... sort of.
>
> Part of the requirements on the template parameters for is_base_of are that
> they are complete types, if they're not complete types then our
> implementation can silently do the wrong thing, so we assert that they are
> complete inside the implementation.  The change was introduced as a bug fix
> to another issue, and simply asserts what we have always documented, so I'm
> afraid you're out of luck in that particular use case :-(
>
> The same applies to std::is_base_of I believe as well.

OK, I see (and now I remember reading about this requirement in the
documentation a while back).

I was (incorrectly) using this together with MPL_ASSERT just to raise
a more descriptive error message. However, this static check is not
necessary as my code will eventually fail somehow if `y` is not a base
of `x`.

Thank you for the clarification.

-- 
Lorenzo