Re: PATCH: Add -fsystem-header-visibility=

["H. J. Lu" <hjl at lucon dot org>]

On Fri, Aug 26, 2005 at 01:34:04PM -0700, Geoffrey Keating wrote:
> "H. J. Lu" <hjl@lucon.org> writes:
> 
> > The current visibility scheme doesn't work too well with symbols from
> > system headers. In most cases, symbols from system headers are defined
> > in libraries which always have default visibility. But when
> > -fvisibililty= or "#pragma GCC visibililty push" is used, symbols from
> > system headers may have non-default visibility. This leads to link-time
> > or run-time problems. This patch adds -fsystem-header-visibility=. It
> > can be used to set the symbols from system headers with different
> > visibility.
> 
> I think this would be better dealt with in another way, for instance
> by changing the headers in question.  Otherwise I see that this is the
> first in a long line of patches which end up with command-line options
> to control visibility for everything individually.

It is impractical to change all those header files come with all
libraries. The only other approach is to require

#pragma GCC visibililty push(default)

#pragma GCC visibililty pop

when a library header file is included. That brings to

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=20303

since you can't use more than 16 nested pushes with gcc 4.0.

> 
> (In particular, I don't see why 'system' headers should be treated
> specially.)

Does -flibrary-visibility sound better? Some C++ symbols don't come
from header files. They are generated by gcc automatically.


H.J.