Re: [Boost-build] Building with clang for Windows/MingW

Subject: Re: [Boost-build] Building with clang for Windows/MingW
From: Edward Diener (eldiener_at_[hidden])
Date: 2014-02-04 01:25:29

On 2/3/2014 11:07 PM, Joshua Boyce wrote:
> On 2 February 2014 08:10, Edward Diener <eldiener_at_[hidden]
> <mailto:eldiener_at_[hidden]>> wrote:
>
>     On 2/1/2014 12:30 PM, Vladimir Prus wrote:
>
>         On 31.01.2014 03:18, Edward Diener wrote:
>
>             When trying to test clang under Windows which is built with
>             MingW,
>             which essentially becomes clang-linux as a toolset, Boost
>             Build runs with
>             the options:
>
>             -c -x c++ -O0 -g -fno-inline -Wall -g -mthreads
>
>             However clang does not recognize -mthreads and flags it as
>             an error.
>             Is there anything I can do to remove this option from the
>             clang++.exe
>             command line when invoking Boost Build ?
>
>
>         I though there's another clang-win somewhere in the works?
>
>
>     According to clang web site there are two possible versions of clang
>     on Windows. One uses the VC++ RTL while the other uses the MingW/gcc
>     RTL.
>
>     I am able to create either version on Windows7. However the VC++ RTL
>     version ( clang-cl ) has numerous problems with Boost because it
>     does not support VC++-style exception handling nor RTTI, issues
>     already reported to clang. Also I pointed out to you a minor issue
>     with the Boost build setup of that version which was created by
>     another person and tweaked only very slightly by me. You did not
>     seem very interested in helping to correct that issue and I am not
>     knowledgable enough with Boost build to do so. Nonetheless that is
>     currently a moot issue since the issue produced a warning only (
>     although annoyingly repeatedly with each compile ), and clang-cl
>     does not work with most of Boost because of the shortcomings of the
>     clang-cl compiler itself mentioned above.
>
>     So now I am interested to see if I can run Boost tests in Windows
>     with the version of clang that can be built using MingW/gcc RTL.
>
>
>         Picking
>         clang-linux seems suspicious to me, on Windows.
>
>
>     MingW is supposed to emulate a *Nix environment. To what extent in
>     relation to using Boost build as clang-linux I do not know.
>
>
>         If you want to make
>         clang-linux work, you probably can declare a function
>         setup-threading in
>         clang-linux.jam which basically forwards to gcc.setup-threading,
>         except for the case of target-os=windows, where it should do
>         nothing.
>
>         Does this help?
>
>
>     I get the idea. Thanks !
>
>
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>
> Hi Edward,
>
> Would you mind posting (or even better - committing) a patch if you get
> this working? I hit the same roadblock (and I expect others may have
> also) and didn't have the time or Boost.Build knowledge to overcome it.

I just added to 'clang-linux.jam' these lines taken from 'gcc.jam' and 
altered slightly:

rule setup-threading ( targets * : sources * : properties * )
{
     local threading = [ feature.get-values threading : $(properties) ] ;
     if $(threading) = multi
     {
         local target = [ feature.get-values target-os : $(properties) ] ;
         local option ;
         local libs ;

         switch $(target)
         {
             case windows : # No threading options.
#            case windows : option = -mthreads ;
             case cygwin  : option = -mthreads ;
             case solaris : option = -pthreads ; libs = rt ;
             case beos    : # No threading options.
             case *bsd    : option = -pthread ;  # There is no -lrt on BSD.
             case sgi     : # gcc on IRIX does not support multi-threading.
             case darwin  : # No threading options.
             case *       : option = -pthread ; libs = rt ;
         }

         if $(option)
         {
             OPTIONS on $(targets) += $(option) ;
         }
         if $(libs)
         {
             FINDLIBS-SA on $(targets) += $(libs) ;
         }
     }
}

However I also found out that clang on Windows using MingW/gcc RTL does 
NOT support multi-threading at all. So IMO it is particularly useless 
when used with Boost libraries. Basically I decided, at least for 
myself, that I will forgo trying to test with clang under Windows, 
whether with clang with MingW/gcc RTL or clang-cl with VC++ RTL, until 
clang under Windows gets those features which make it usable with 
current Boost libraries. Your own choice may be different.