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

From: Rene Rivera (grafik.list_at_[hidden])
Date: 2005-08-26 10:15:11

Mat Marcus wrote:
> 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>

As far as I understand this is only a problem with the Apple version of 
GCC? I'm curious because the GCC documentation explicitly says that the 
default visibility is for all symbols to be public which is designed for 
backward compatibility, as in this case.

> Questions: 
> 1) What is the right way to make some flags dependent on compiler
> version?

For BBv1, one way is to rely on the toolset name. Another is using the 
SHELL builtin as you did. And yet another is to use the name of the GCC 
executable as it has the version number on some installations. And 
sometimes you can use the version of the OS as the compiler is available 
based on a release. v1/darwin-tools.jam uses a combination of those to 
account for the "-fcoalesce-templates" option.

> 2) Does anyone dislike the idea of making <symbol-visibility> a feature?

Not really. But it's usually good to either consider if such a feature 
should be available for all toolsets (i.e. can it be implemented or 
faked for all compilers), or to limit it to one toolset and/or platform.

I think the important issue to figure out here is where this 
"-fvisibility=hidden" being the default is a problem and limit any fix 
to those contexts.

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