Re: [PATCH] libstdc++: Export the __gnu_cxx::zoneinfo_dir_override symbol.

[Jonathan Wakely <jwakely@redhat.com>]

On Sat, 24 Dec 2022 at 12:21, Iain Sandoe <iain@sandoe.co.uk> wrote:
>
>
>
> > On 24 Dec 2022, at 12:12, Jonathan Wakely wrote:
> >
> >
> >
> > On Sat, 24 Dec 2022, 11:35 Iain Sandoe via Libstdc++, <libstdc++@gcc.gnu.org> wrote:
> >  If this is not the right place to export the symbol (or you do not want
> >  to export it in the general case), I can always add a platform-specific
> >  file for it.  So far, tested on x86_64-darwin21, wider testing will
> >  follow over the holidays.
> >
> >  OK for trunk?
> >
> > I'd like to check if this causes the undefined weak symbol to be exported on ELF,
>
> I’d expect so, since it’s in the common file.

hppa-hp-hpux* wants this symbol to be defined anyway (see PR 108228),
so please push your patch to trunk.


>
> > but I suppose that doesn't really cause any harm if it is. The symbol name is in our own namespace so can't clash with user symbols. We can't declare that function in a header, because "zoneinfo_dir_override" is not a reserved name so could clash with user macros (we could prefix it with underscores, but since it's possible to override it without the library providing a declaration, I think it would be "nicer" to not use an ugly reserved name for something users are supposed to define themselves).
>
> I can also investigate the alternate solution for Darwin - where we pass -U,symbolname to the linker.
> In that case, we do not need to provide a weak def. in the library (it looks more ELF-like) but the symbol
> does still need to be exported - however that could Darwin-local too as noted above.
>
> (none of this is urgent, bootstrap is fixed - I was just poking at the problems while they were fresh in
>  my mind;  although the fails are removed when I configure to an installation with tzdata.zi, there are
>  still fails to deal with when using the system installation .. so I’m not ’there’ yet .. )
>
> cheers
> Iain
>
> >
> >
> >
> >
> >  Iain
> >
> >  --- 8< ---
> >
> > This symbol needs to be visible in the library interface for Darwin
> > to override it with a user-provided one.
> >
> > Signed-off-by: Iain Sandoe <iain@sandoe.co.uk>
> >
> > libstdc++-v3/ChangeLog:
> >
> >         * config/abi/pre/gnu.ver (GLIBCXX_3.4):
> >         Add __gnu_cxx::zoneinfo_dir_override().
> > ---
> >  libstdc++-v3/config/abi/pre/gnu.ver | 3 +++
> >  1 file changed, 3 insertions(+)
> >
> > diff --git a/libstdc++-v3/config/abi/pre/gnu.ver b/libstdc++-v3/config/abi/pre/gnu.ver
> > index 570ffca8710..bd4ab450652 100644
> > --- a/libstdc++-v3/config/abi/pre/gnu.ver
> > +++ b/libstdc++-v3/config/abi/pre/gnu.ver
> > @@ -1104,6 +1104,9 @@ GLIBCXX_3.4 {
> >      # std::uncaught_exception()
> >      _ZSt18uncaught_exceptionv;
> >
> > +    # __gnu_cxx::zoneinfo_dir_override()
> > +    _ZN9__gnu_cxx21zoneinfo_dir_overrideEv
> > +
> >    # DO NOT DELETE THIS LINE.  Port-specific symbols, if any, will be here.
> >
> >    local:
> > --
> > 2.37.1 (Apple Git-137.1)
> >
>