Jason Merrill <[EMAIL PROTECTED]> writes: > Gabriel Dos Reis wrote: > > Mark Mitchell <[EMAIL PROTECTED]> writes: > > | I'm just not comfortable with the idea of #pragmas affecting > > | instantiations. (I'm OK with them affecting specializations, though; in > > | that case, the original template has basically no impact, so I think > > | it's fine to treat the specialization case as if it were any other > > | function.) > > I'm undecided whether #pragmas should not affect explicit > > instantiations. They really are not like implicit instantiations > > (which, I agree with you, should not be affected). Explicit > > instantiations behave more like real declarations than implicit > > instantiations. > > Yep. I'm sympathetic to Mark's position, but still tend to believe > that the #pragma should affect explicit instantiations. Explicit > instantiations are a way to make template instantiations conform more > to the traditional declaration/definition model. We ignore the > #pragmas for implicit instantiations because the user doesn't control > the point of instantiation; with explicit instantiations, they do. > > Explicit instantiations don't behave just like implicit > instantiations; there are other differences.
A consequence of this is that if a user instantiates a template that they don't 'own' (that is, a template from a different module), they must make sure that no #pragma is in effect, because the other module may have a specific idea about what visibility should be used. I'm not sure how exactly they can do this. Is there a visibility pragma for "no setting"? It seems like this would be a common enough mistake that there should be a way to get a warning about it. In the traditional declaration/definition model, if you try to change the linkage of something you get an error...
