Re: [boost] BOOST_STATIC_CONSTANT

Subject: Re: [boost] BOOST_STATIC_CONSTANT
From: Vladimir Batov (Vladimir.Batov_at_[hidden])
Date: 2017-08-17 02:46:13

On 2017-08-17 12:26, Edward Diener via Boost wrote:
> On 8/16/2017 7:22 PM, Vladimir Batov via Boost wrote:
>> There is something seemingly basic that puzzles me greatly. I am 
>> hoping people might clarify something I totally fail to understand.
>> 
>> I've been using BOOST_STATIC_CONSTANT for ages (with GCC). Now I have 
>> something seemingly non-controversial:
>> 
>> template<typename user_type>
>> struct impl_ptr
>> {
>>      using yes_type = boost::type_traits::yes_type;
>>      using  no_type = boost::type_traits::no_type;
>>      using ptr_type = typename std::remove_const<user_type>::type*;
>> 
>>      template<typename Y>
>>      static yes_type test (Y*, typename Y::impl_ptr_type* =nullptr);
>>      static no_type  test (...);
>> 
>>      BOOST_STATIC_CONSTANT(bool, value = (1 == 
>> sizeof(test(ptr_type(nullptr)))));
>> };
>> 
>> When compiled with gcc-.5.4.0, both lines below pass:
>> 
>> BOOST_TEST(true == boost::impl_ptr<Shared>::value);
>> BOOST_TEST(true == boost::impl_ptr<Shared const>::value);
>> 
>> The only difference between them is "const". However, when I compile 
>> with clang-4.0, the second (const) line passes. However, the first one 
>> fails! I refuse to believe it's a clang glitch. It must be me doing 
>> something really stupid. Help?!
> 
> Can you not use tti to do what you want to do ?

Thanks, Ed. The code above was there for god-knows-how-long. I am 
reading TTI docs now to make sure to use it in the future. Tnx.