[boost] Re: assert() replacement?

From: Greg Colvin (gcolvin_at_[hidden])
Date: 1999-08-31 10:56:32

I think the heart of the matter is this: do we wish to enforce that Boost
authors may not use the standard assert macro?

If yes, then we need a replacement.  If no, it is less important.

From: Kevlin Henney <Kevlin.Henney_at_[hidden]>
>    It's not to say that one can't resolve the issue, but the question is,
>    do we wish to impose a single development style on others just because
>    they wish to use polymorphic_cast or numeric_cast? I would hope not.

No, we do not wish to, but we may have to.  Although "impose a single
development style" seems a harsh characterization of "define NDEBUG, or
not, in accordance with the standard".

>    To get it right, we would have to mandate that all of their source code
>    (and that can be a lot) was compiled consistently w/ or w/o NDEBUG set
>    -- goodbye to the benefits of separate compilation :-( -- and that this
>    includes any libraries they themselve used, which may or may not be
>    under their control. This level of intrusion would be a heavy price to
>    pay for using these casts!

Does anyone know how C99, which now has inline functions, handles this
problem, if it does?

>    It doesn't really matter whether or not a compiler diagnoses ODR, you
>    can still get ODR problems: it is the violation not the diagnosis that
>    is the root of the problem. I have come across a couple of instances
>    where ODR violation has lead to problems -- the absence of ODR diagnosis
>    has just meant that it took longer to find, but it didn't mean the
>    problem wouldn't arise.

Yep.  For instance, if you take the address of a function, and get two
copies of the function when you expected one, because of different assert
definitions.

>    I am not sure that relaxing ODR for assert is an issue: it has no
>    linkage! The issue arises for functions that use it, and as far as I can
>    see there is no standard way one could do it. The last thing one would
>    want to see in the standard is an extra paragraph at the end of section
>    3.2 stating "BTW, anything that uses assert is exempt from all of the
>    above. The behavior is implementation defined." :-}

I'm not anticipating a change in the standard, just some compiler magic.
Perhaps that is too much to ask.