Re: Our docs about --enable/--disable-visibility

[Paolo Carlini <pcarlini at gmail dot com>]

Hi

> In 4.2 and later, enables or disables visibility attributes. If
> enabled (as by default), and the compiler seems capable of passing the
> simple sanity checks thrown at it, adjusts items in namespace std,
> namespace std::tr1, and namespace __gnu_cxx <INS>to have default
> visibility</INS> so that -fvisibility options <DEL>work</DEL><INS>can
> be used without affecting the external-visibility mandated by the
> Standard for the namespace std
> entities</INS>
> 
> I'm not really sure about "mandated" because the standard is silent on
> the subject of shared libraries, although hiding std entities could
> cause ODR violations.

Great, I'm very happy that we are on the same page on this. I think that if you could commit the above it would be a definite improvement. Or you can figure out something a little more vague about 'mandated', maybe just using standard, lower case, in the wording, would go a long way ;) Maybe take inspiration from the way the gcc docs generally describe the 'default' visibility?

> 
>> Minor detail: I see that --enable/disibility-visibility may give the wrong
>> impression, as something passed at *global* configure time, that it switches
>> on/off the entire visibility mechanism at the compiler level too, maybe
>> something like --enable-libstdcxx-visibility or
>> --enable-libstdcxx-namespaces-visibility?!? But this is a detail at this
>> stage.
> 
> Agreed.  I've wondered sometimes whether all libstdc++-specific
> configure options should start with --enable-libstdcxx-

Great, again. Now, as we discussed a bit already with V, I'm not 100% sure that just renaming is the way to go: are we risking breaking building scripts?!? Certainly the option isn't used by the major distros, since the default is fine for the majority of the users. Ideally it would be nice to deprecate the old one and add the -libstdcxx- variant, but I don't think we have infrastructure in place to do this. Shall we just rename and be done with it?!? Objections?

Thanks,
Paolo