Re: [boost] Deprecate BOOST_STATIC_ASSERT?

From: Andrey Semashev (andrey.semashev_at_[hidden])
Date: 2008-06-21 03:08:13

David Abrahams wrote:
> Yesterday someone on the user's list posted a message
> (http://article.gmane.org/gmane.comp.lib.boost.user/36884) about a
> "compilation error in the boost code:"
> 
>   s-test.h:49:   instantiated from here
>   /usr/include/boost/archive/detail/oserializer.hpp:567: error: invalid
>   application of 'sizeof' to incomplete
>   type 'boost::STATIC_ASSERTION_FAILURE<false>'
>   make: *** [stest] Error 1
> 
> and proceeded to try to analyze the BOOST_STATIC_ASSERT implementation
> to see what was wrong with it.  Granted, most people figure out what a
> static assertion is supposed to be, but still, the error message gave no
> clue about what might have gone wrong... no clue to the user, and no
> clue to anyone reading his posting, unless they were going to look up
> the line in the source file... oops, I take it back.  My copy of
> oserializer.hpp doesn't even have a line 567, and the posting doesn't
> indicate which version the user has.
> 
> For several releases now we've had a suite of static assertion tools
> that give far superior error messages to what BOOST_STATIC_ASSERT can
> provide
> (http://www.boost.org/doc/libs/1_35_0/libs/mpl/doc/refmanual/asserts.html).
>  I think <radical-idea>it's time to deprecate
> BOOST_STATIC_ASSERT</radical-idea> or at *least* put a prominent note in
> its documentation directing people at the BOOST_MPL_ASSERT macros.
> 
> Thoughts?

As a user and a library writer I would ask to keep BOOST_STATIC_ASSERT 
as it is without deprecation. I'm using this macro on a regular basis 
and found no problems with it. I usually put a comment near the macro 
that explains what the check does and I'm very sure the comment will be 
far more informative than any compiler-generated error message (unless 
we are speaking of static_assert in C++0x).

I wouldn't like to move to BOOST_MPL_ASSERT since (a) it would require 
to change my code (b) it would complicate condition expressions with 
compile-time constants and (c) it would introduce dependency on MPL 
where there was no such dependency. However, I think pointers to MPL 
docs near BOOST_STATIC_ASSERT description is a good idea.