[Boost-build] clang-win and clang-linux both try to use GCC --start-group and --end-group and produce spurious warnings on Windows.

From: pbristow_at_[hidden]
Date: 2019-10-10 14:30:13

Clang on Windows 

I have used both b2 bjam toolset=clang and toolset=clang-win but found some subtle configuration issues.

So I tried toolset=clang (which reports a clang-linux) and have now got Boost.Multiprecision to pass tests and examples 😊

This is really useful to allow b2 toolset=msvc,gcc,clang cxxstd=2a …

But I note that clang-win and clang-linux both try to use GCC ‘s  

--start-group and --end-group

 and produce spurious warnings like this

clang-linux.link ..\..\..\bin.v2\libs\multiprecision\example\numeric_limits_snips.test\clng-lnx-9.0.0\rls\cxstd-2a-iso\lnk-sttc\thrd-mlt\vsblt-hdn\numeric_limits_snips.exe
lld-link: warning: ignoring unknown argument '--start-group'
lld-link: warning: ignoring unknown argument '-Bstatic'
lld-link: warning: ignoring unknown argument '-Bdynamic'
lld-link: warning: ignoring unknown argument '--end-group'

if using the lld linker

and similarly using the clang++ (is this really the MSVC linker? Its messages look familiar!  And the warning number is appropriate…)

LINK : warning LNK4044: unrecognized option '/soname'; ignored
LINK : warning LNK4044: unrecognized option '/-start-group'; ignored
LINK : warning LNK4044: unrecognized option '/Bstatic'; ignored
LINK : warning LNK4044: unrecognized option '/Bdynamic'; ignored
LINK : warning LNK4044: unrecognized option '/-end-group'; ignored

(and also clang++: warning: argument unused during compilation: '-pthread' [-Wunused-command-line-argument]  (can be suppressed)

This suggests that both .jam files are not quite right (and that this may cause other problems).

Any suggestions on avoiding these warnings (rather than muffling them)?

I am not expert enough to tackle, let alone cure – is there anyone willing to assist?

Thanks

Paul

Paul A. Bristow
Prizet Farmhouse
Kendal, Cumbria 
LA8 8AB           UK