Re: [boost] [iterator][type_traits] A test is failing with gcc in c++03mode

Subject: Re: [boost] [iterator][type_traits] A test is failing with gcc in c++03mode
From: Edward Diener (eldiener_at_[hidden])
Date: 2016-12-17 12:11:58

On 12/17/2016 11:45 AM, Peter Dimov wrote:
> Edward Diener wrote:
>> The zip_iterator_test_std_pair is failing with gcc in c++-03 mode. The
>> problem reduces viqa Boost type traits to the fact that in gcc c++03
>> mode the expression:
>>
>> __is_abstract(std::pair<int&, std::string&>)
>>
>> where __is_abstract is a compiler intrinsic, gives an error of:
>>
>> error: forming reference to reference type
>> 'std::__cxx11::basic_string<char>&'
>>         pair(const _T1& __a, const _T2& __b)
>>         ^~~~
>>
>> Is this a valid error according to the C++ 2003 standard ?
>
> References to references were invalid in C++98, but were made
> conditionally valid in C++03 by
>
> http://www.open-std.org/jtc1/sc22/wg21/docs/cwg_defects.html#106
>
> However, __is_abstract is nonstandard, so who knows what it does. It
> might be worth trying -std=gnu++03 instead of -std=c++03.

Your suggestion worked brilliantly. With -std=gnu++03 references to 
references are fine. However it looks like zip_iterator may need to be 
changed so that if references to references are not supported it should 
not be used. I did not write or update zip_iterator; Kohei Takahashi did 
the work of updating it.