[Boost-build] gcc visibility support

Subject: [Boost-build] gcc visibility support
From: Robert Ramey (ramey_at_[hidden])
Date: 2010-08-23 14:52:48

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.

But now I have some problems.

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.

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?

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.

any help appreciated.

Robert Ramey