Re: [boost] VC8 no ADL in some cases

From: Andy Little (andy_at_[hidden])
Date: 2006-01-24 18:21:27

"Tobias Schwinger"  wrote

> Your operator- (in the code of your initial post) is not the problem it must
> be
> the context it's used in.
>
> I got a copy of your lib and comented the workaround and operator- and added
>
>    template<typename T0,typename T1> T0 operator-(T0 const &, T1 const &);
>
> and it didn't change anything.
>
>>>Does it instantiate templates that use sizeof- or conditional tricks (as
>>>BOOST_TYPEOF_TPL does)?
>>
>>
>> The pqs::meta::binary_operation result_type scheme in the operator+
>> definition
>> above uses SFINAE quite heavily though. I shall try reducing it to a minimal
>> example.
>
> SFINAE (at least SFINAE alone) is not the problem, either. I wrote this little
> test which compiles fine (it would have been too easy, I guess) ;-(.

[ cut code that fails to fail ]

I tried something similar with no luck.

Both  my quantities library and Spirit have in common that types are complicated
I think. Maybe this is the cause of the problem. Say where there is a large
number of contexts  to look up, the first or last one gets missed or
overwritten.  It might be worth sprinkling likely operations around in some
other namespaces mentioned in 3.4.2   to see if  there is any sign of two phase
lookup occurring.
Whatever my first strategy is going to be to strip back my pqs library bit by
bit until the bug disappears.
I feel better about that than building something waiting for the bug to appear.
;-)

>> Boost.Typeof use in the implementation (for operations on built-in types) is
>> optional though I havent tried  turning it off yet
>
> BOOST_TYPEOF_TPL in particular messes up ADL for the expression passed to it
> (the
> thread I linked to). Guessing from VC8's extremely strange behaviour in that
> case
> TYPEOF_TPL might act as some sort of "bug attractant"... I'd definitely give
> it a
> try!

I have tried it but It makes no difference in this particular case. FWIW if you
go into <boost/pqs/config.hpp> and

comment out  line 30 :

 #define BOOST_PQS_USE_BOOST_TYPEOF_BINARY_OPERATION .

Then Boost.Typeof is knocked out ... though it  adds in another synthesized type
deduction scheme.

regards
Andy Little