Re: [Boost-users] 1.58.0 rc3 is now available

Subject: Re: [Boost-users] 1.58.0 rc3 is now available
From: Marshall Clow (mclow.lists_at_[hidden])
Date: 2015-04-09 11:54:36

On Thu, Apr 9, 2015 at 8:15 AM, Deniz Bahadir <dbahadir_at_[hidden]> wrote:

> Am 09.04.2015 um 16:39 schrieb Marshall Clow:
>
>> On Thu, Apr 9, 2015 at 4:11 AM, Deniz Bahadir <dbahadir_at_[hidden]
>> <mailto:dbahadir_at_[hidden]>> wrote:
>>
>>     Building Boost 1.58.0-rc3 succeeded only partially.
>>
>>
>>     Success:
>>
>>       Debian 7 with GCC 4.8.2 (in C++03 mode) with build-command:
>>         b2 -j4 --build-dir=/opt/build/test --build-type=complete
>>     --layout=versioned address-model=64 architecture=x86 install
>>     --prefix="/opt/install/test" toolset=gcc-4.8 cflags="-fPIC"
>>     cxxflags="-fPIC" dll-path="/opt/test/lib/x86___64-linux-gnu"
>>
>>
>>     Failure:
>>
>>       Debian 7 with GCC 4.8.2 (in C++11 mode) with build-command:
>>         b2 -j4 --build-dir=/opt/build/test --build-type=complete
>>     --layout=versioned address-model=64 architecture=x86 install
>>     --prefix="/opt/install/test" toolset=gcc-4.8 cflags="-fPIC"
>>     cxxflags="-fPIC -std=c++11" dll-path="/opt/test/lib/x86___
>> 64-linux-gnu"
>>
>>
>>     The main-error seems to come from "Boost.Context" and the use of
>>     unknown "std::index_sequence":
>>
>>
>> std::index_sequence is a C++14 feature.
>>
>>
> The question is then: Why is it used when I only enable C++11 features?
>

My guess would be "a bug".

> I suppose, GCC 4.8(.2) is too old to support std::index_sequence. (Or is
> it the bundled stdlibc++?)
> When using C++14 mode ("cxxflags=-fPIC -std=c++1y") the same errors occur.
>

It would not surprise me if gcc 4.8.x did not support index_sequence.
And yes, it would be the libstdc++ that comes with the compiler, not the
compiler itself.

FWIW, index_sequence *is* implemented in gcc 4.9.2, but it is only
available post-c++11.

-- Marshall