Re: [Boost-build] question regarding "requires cxx11_hdr_array" clause in Jamfile

Subject: Re: [Boost-build] question regarding "requires cxx11_hdr_array" clause in Jamfile
From: Edward Diener (eldiener_at_[hidden])
Date: 2016-12-06 14:22:07

On 12/6/2016 2:03 PM, Robert Ramey wrote:
> In tests of the boost seriaization library here:
>
> https://api.travis-ci.org/jobs/181492138/log.txt?deansi=true
>
> I have a test failure with the test "test_array".  The test includes
> boost/serialization/array.hpp.  This header file morphed from
> implementing the serialization of native arrays (which was moved to the
> core of the library) to implementing serialization of <array>.  So the
> test shouldn't be run if the <array> header doesn't exist and will fail
> if it does.
>
> To this end, boost/serialization/array.hpp contains the following:
>
> #ifndef BOOST_NO_CXX11_HDR_ARRAY
>
> #include <array>
> #include <boost/serialization/nvp.hpp>
>
> ...
>
>
> To implement the above I've included the following in my jamfile:
>
>      [ test-bsl-run_files test_array : A : :  [ requires cxx11_hdr_array
> ] ] # BOOST_NO_CXX11_HDR_ARRAY
>
> Which I understand should condition the invocation of the test on
> config.hpp not defining BOOST_NO_CXX11_HDR_ARRAY.  In general this
> approach seems to work well.  But I'm having a problem with this
> specific case.
>
> Interesting parts of the log file above are:
>
> $ TOOLSET=gcc,clang
>
> The command "TOOLSET=gcc,clang" exited with 0.
> $ if [ $TRAVIS_OS_NAME == osx ]; then TOOLSET=clang; fi
>
> The command "if [ $TRAVIS_OS_NAME == osx ]; then TOOLSET=clang; fi"
> exited with 0.
> $ ./b2 libs/serialization/test toolset=$TOOLSET
> Performing configuration checks
>
>     - 32-bit                   : no
>     - 64-bit                   : yes
>     - arm                      : no
>     - mips1                    : no
>     - power                    : no
>     - sparc                    : no
>     - x86                      : yes
>     - symlinks supported       : yes
>     - Boost.Config Feature Check: cxx11_hdr_array : yes
>     - Boost.Config Feature Check: cxx11_hdr_forward_list : yes
>     - Boost.Config Feature Check: hash : no
>     - Boost.Config Feature Check: cxx11_hdr_unordered_map : yes
>     - Boost.Config Feature Check: cxx11_hdr_unordered_set : yes
>     - Boost.Config Feature Check: slist : no
>     - Boost.Config Feature Check: std_wstreambuf : yes
> ...patience...
>
> So this shows that BOOST_NO_CXX11_HDR_ARRAY is not defined. So I would
> expect test_array to run - which it does.  BUT when the test is actually
> run, it fails because the code in <array> is not included.

What do you mean by "the code in <array> is not included" ? Are you 
referring to your own serialization array header or are you referring to 
the C++ standard array header ?

>  This leads
> me to believe that when the test is actually run
> BOOST_NO_CXX11_HDR_ARRAY IS in fact defined.
>
> In other words, it looks like boost build checks for the existence of
> <array> while boost config checks for the C++ version to see if <array>
> is supported.  This would explain the behavior I'm seeing.
>
> I would like someone else's informed opinion on this and what I might do
> about it.
>
> Note: I intend to change the name of test_array to test_std_array but I
> don't want to do this until the current problem is sorted out.
>
> Robert Ramey