Re: [Boost-build] adding tests conditional on compiler's C++11 support

Subject: Re: [Boost-build] adding tests conditional on compiler's C++11 support
From: Robert Ramey (ramey_at_[hidden])
Date: 2016-11-11 12:15:37

On 11/11/16 7:04 AM, Steven Watanabe wrote:
> I'm guessing that the problem is that config.requires
> directly uses the tests for Boost.Config.  The macros
> are supposed to be in sync with the tests, so I think
> this is a bug in Boost.Config.

I've considered that.  But if that's the case, then the problem should 
never occur.

I've looked at the test matrix for config.  Looking at row labeled 
config_info and columns Sandia-darwin-c++11/darwin 4.2.1 and 
Sandia-darwin/darwin 4.2.1.  Note the only difference is the C++11 switch.
The outputs for config_info differ in that the one using the C++11 does 
not have BOOST_NO_CXX11_HDR_FORWARD_LIST while the one not using the 
C++11 switch does. This is as it should be.

But b2 is invoking test_forward_list even when config_info suggests it 
shouldn't.  Is is possible that b2 is invoking using the config_info 
test results generated with with the C++11 switch?  The "requires" would 
mean that test_forward_list would be invoked.  But when it actually is 
(with the BOOST_NO_CXX11_HDR_FORWARD_LIST being set), the compilation 
aborts with #error.

This would not surprise me.  When I run C++11 tests, I have to add a c++ 
switch to the compiler command line.  I do this in my user_config.jam 
with the statement

using darwin : 6.2~11 : /hpc-6.2/usr/local/bin/g++ : 
<cxxflags>"-std=c++11" <define>"BOOST_LIB_DIAGNOSTIC=1" ;

I don't know how the test matrix does it.  But in any case I don't see 
how bjam/config would "know" how to set the switch when it does it's 
thing.  I don't know if there is a "global" setting of compiler version. 
  It think there is something fundamental missing here - at at least 
that I'm missing.

It's also odd that it seems to occur in this one special case.  I don't 
know what to make of this.

Any insight you want to share would be appreciated.

Robert Ramey