Re: [Boost-build] gcc visibility support

Subject: Re: [Boost-build] gcc visibility support
From: Jürgen Hunold (juergen.hunold_at_[hidden])
Date: 2010-08-23 14:35:54

Hi Robert,

On Monday, 23. August 2010 20:52:48 you wrote:
> I'm interested in adding support for -fvisibility=hidden to the gcc library
> compilations.
> 
> I can include the following in the Jamfile.v2 of the build directory.
> 
> <toolset>gcc:<cxxflags>"-fvisibility=hidden"
> 
> which bjam seems to accept without complaint.  Indeed the gcc command line
> includes -fvisibility=hidden.
> 
> So, so good.

The best solution is direct Boost.Build support as described in issue #2114.

> any help appreciated.

Please find a patch with "works-for-me" status attached.

Invoking "bjam visibility=hidden" should then do the right thing.

> a) visibility is supported in version 4+ compilers.  What syntax does one
> use to specify that that the above should only apply to these compilers.

I copied the "real-version" query from darwin.jam and used the version 
reported by gcc.

> b) If one is building a static library, presuably the above shouldn't be
> included (though it probably does no harm).  How does this modify the above
> syntax?

<toolset>gcc,<link>shared:<cxxfkags>-fvisibility=hidden

> c) The cygwin system I use to test has gcc-4.3.4 installed.  BUT, the usage
> of -fvisibility=hidden evokes a compile time warning for file.  The warning
> says that visibility is not supported on this build - which presumably is
> cygwin. So the above would also have to be conditioned upon the fact that
> cygwin is not being used.

Good question. The idea was to add this logic to "configure-version-specific" by 
adding the current properties. I hope this would work somehow.

Hope this little helps.

Yours,

Jürgen
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