Re: [boost] [proto] _value doesn't enforce zero arity

Subject: Re: [boost] [proto] _value doesn't enforce zero arity
From: troy d. straszheim (troy_at_[hidden])
Date: 2009-04-08 18:39:13

Dave Jenkins wrote:
> "David Abrahams" <dave_at_[hidden]> wrote in message 
> news:m28wmbf91i.fsf_at_boostpro.com...
>>
>> on Tue Apr 07 2009, "troy d. straszheim" <troy-AT-resophonic.com> wrote:
>>
>>> Gevorg Voskanyan wrote:
>>>
>>>> How about a macro BOOST_PROTO_EXTRA_CHECKING or something like that 
>>>> to have those
>>> kind of checks conditionally?
>>>
>>> I could see a BOOST_MPL_DISABLE_ASSERTS token, behavior analogous to
>>> BOOST_DISABLE_ASSERTS.
>>
>> It's a very good idea, IMO.  Open a ticket?
> 
> This flag sounds the same as the BOOST_COMPILE_TIME_DEBUG flag proposed 
> by Eric
> Niebler here: http://lists.boost.org/boost-users/2009/01/44451.php.
> Joel de Guzman suggested making it an integer (0 == no CT debug, 1..3 CT 
> debug levels) here:
> http://lists.boost.org/boostusers/2009/01/44452.php.
> 
> My thought is to have one of the integer debug levels enable 
> compile-time tracing of
> "interesting" template instantiations using Steven Watanabe's 
> template_profiler.
> For this to work, the library author would have to mark the "interesting"
> template classes and functions with "PROFILE_TRACER()" and bypass
> Steven's preprocessing stage.  Is this workable and/or a good idea?
> 

Interesting ideas...

At first glance it still seems to me like stuff that belongs in the MPL. 
  I could see an MPL_TRACE() macro that expanded by default to nothing. 
  The user could set it as appropriate to use Steven's tracer or some 
future tracer, for instance one built in to clang.

I'm not sure I agree with the debug-levels idea, as these are asserts, 
not warning severity levels.  If they were warnings, it is still 
difficult to coordinate between developers, ie I don't really know if 
I'm using level '2' to mean the same level of 'debugginess' as somebody 
else is.  It is also impossible to enforce.

In the case where debug levels are going to regulate the number of 
traces you see, I don't see that as very useful either, since when 
tracing template instantiations you're dealing with a spectacular amount 
of compiler-spew no matter what.  Now, per-class trace control (maybe 
via a trait?) this would be imho more useful.

-t