Re: [boost] [type_traits] possible regression on is_function trait

Subject: Re: [boost] [type_traits] possible regression on is_function trait
From: Jeffrey Lee Hellrung, Jr. (jeffrey.hellrung_at_[hidden])
Date: 2012-11-05 22:40:25

On Mon, Nov 5, 2012 at 9:56 AM, Vicente J. Botet Escriba <
vicente.botet_at_[hidden]> wrote:

> Le 05/11/12 18:26, Vicente J. Botet Escriba a écrit :
>
>> Hi,
>>
>> I don't know if this is a regression on Boost.TypeTraits or if I'm using
>> incorrectly the is_function trait.
>>
>> John, could you confirm there is a bug  in is_function?
>>
>> Best,
>> Vicente
>>
>> Test output: Sandia-darwin-4.4 - thread - async__async_p / darwin-4.4
>> Rev 81191 / Mon, 5 Nov 2012 06:30:00 +0000
>> *Report Time: *Mon, 5 Nov 2012 14:19:58 +0000
>> Compile [2012-11-05 07:50:44 UTC]: fail
>>
>>     "/opt/local/bin/g++-mp-4.4"  -ftemplate-depth-128 -O0 -fno-inline
>> -Wall -pedantic -g -dynamic -gdwarf-2 -fexceptions -fPIC -Wextra
>> -Wno-long-long -fpermissive -pedantic -DBOOST_ALL_NO_LIB=1
>> -DBOOST_CHRONO_DYN_LINK=1 -DBOOST_SYSTEM_DYN_LINK=1
>> -DBOOST_SYSTEM_NO_DEPRECATED -DBOOST_THREAD_BUILD_DLL=1
>> -DBOOST_THREAD_POSIX -DBOOST_THREAD_THROW_IF_**PRECONDITION_NOT_SATISFIED
>> -DBOOST_THREAD_USE_DLL=1  -I".." -c -o "/Volumes/scratch/kbelco/**
>> boost/results/boost/bin.v2/**libs/thread/test/async__async_**
>> p.test/darwin-4.4/debug/**threading-multi/sync/futures/**async/async_pass.o"
>> "../libs/thread/test/sync/**futures/async/async_pass.cpp"
>>
>> In file included from ../boost/type_traits/is_**convertible.hpp:28,
>>                  from ../boost/thread/detail/move.**hpp:13,
>>                  from ../boost/thread/future.hpp:20,
>>                  from ../libs/thread/test/sync/**
>> futures/async/async_pass.cpp:**28:
>> ../boost/type_traits/is_**function.hpp: In instantiation of
>> 'boost::detail::is_function_**chooser<false>::result_<boost:**
>> :rv<boost::rv<boost::packaged_**task<int()> > >&>':
>> ../boost/type_traits/is_**function.hpp:60:   instantiated from
>> 'boost::detail::is_function_**impl<boost::rv<boost::rv<**boost::packaged_task<int()>
>> > >&>'
>> ../boost/type_traits/is_**function.hpp:102:   instantiated from
>> 'boost::is_function<boost::rv<**boost::rv<boost::packaged_**task<int()>
>> > >&>'
>> ../boost/type_traits/is_**convertible.hpp:354:   instantiated from
>> 'const bool boost::detail::is_convertible_**impl<boost::rv<boost::**packaged_task<int()>
>> >&, boost::rv<boost::rv<boost::**packaged_task<int()> > >&>::value'
>> ../boost/type_traits/is_**convertible.hpp:480:   instantiated from
>> 'boost::is_convertible<boost::**rv<boost::packaged_task<int()> >&,
>> boost::rv<boost::rv<boost::**packaged_task<int()> > >&>'
>> ../boost/thread/future.hpp:**2717:   instantiated from 'boost::future<T>
>> boost::async(boost::launch, R (*)()) [with R = int]'
>> ../libs/thread/test/sync/**futures/async/async_pass.cpp:**117:
>> instantiated from here
>> ../boost/type_traits/is_**function.hpp:52: error: forming pointer to
>> reference type 'boost::rv<boost::rv<boost::**packaged_task<int()> > >&'
>>
>>
>>
>>  I don't know what is going wrong, but the instantiation seems to think
> that boost::rv<boost::rv<boost::**packaged_task<int()> > >& is not a
> reference.
>

Red flag seeing boost::rv< boost::rv< ... > > :/

Aside from that, looks strange; is this the only tester with an issue?

> Could someone check this?
>
> Thanks,
> Vicente
>
> template<bool is_ref = true>
> struct is_function_chooser
>     : public ::boost::type_traits::false_**result
> {
> };
>
> template <>
> struct is_function_chooser<false>
> {
>     template< typename T > struct result_
>         : public ::boost::type_traits::is_**function_ptr_helper<T*>
>     { //line 52
>     };
> };
>
> template <typename T>
> struct is_function_impl
>     : public is_function_chooser< ::boost::is_reference<T>::**value >
>         ::BOOST_NESTED_TEMPLATE result_<T>
> { //line 60
> };
>

- Jeff