Re: [jamboost] Towards a patch for boost build under gcc 4.0, link=shared

From: Doug Gregor (dgregor_at_[hidden])
Date: 2005-08-25 11:49:42

This is a really important bug to get fixed, both for BBv1 and for 
BBv2, especially since we are now planning to roll a 1.33.1 release 
that should address this problem (among others). Could some of the bjam 
experts take a look at this?

Doug

On Aug 24, 2005, at 2:31 PM, Mat Marcus wrote:

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> I am working towards a patch for boost build (both versions) to allow
> executables produced by boost-build to work when linked against shared
> library versions of boost, under gcc 4.0. See for example:
>
> <http://article.gmane.org/gmane.comp.lib.boost.build/10072>
>
> I am more familiar with bbv2 so I will begin with there. The idea is to
> add a new feature <symbol-visibility>, which defaults to
> - -fvisibility=hidden:
>
> ### add to builtins.jam
>
> feature symbol-visibility : exported hidden : propagated ;
>
> ### add to gcc.jam
>
> flags gcc.compile OPTIONS <symbol-visibility>exported :
> - -fvisibility=default ;
> flags gcc.compile OPTIONS <symbol-visibility>hidden :
> - -fvisibility=hidden ;
>
> ### end
>
> That won't quite work, since gcc versions prior to 4.0 don't understand
> this flag (except for some patched versions IIUC). I tried to make it
> conditional, following some code I found in darwin.jam, by wrapping it
> as follows:
>
> local gccversion = [ SHELL "$(command) -dumpversion" ] ;
> if $(version) >= "4.0.0"
> {
> flags gcc.compile OPTIONS <symbol-visibility>exported :
> - -fvisibility=default ;
> flags gcc.compile OPTIONS <symbol-visibility>hidden :
> - -fvisibility=hidden ;
> }
>
> This doesn't work well when under cygwin for me though.
>
> Questions:
> 1) What is the right way to make some flags dependent on compiler
> version?
> 2) Does anyone dislike the idea of making <symbol-visibility> a 
> feature?
>
> Same questions for BBv1.
>
> Thanks,
> Mat
>
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