Re: [committed] libstdc++: Export global iostreams with GLIBCXX_3.4.31 symver [PR108969]

[Jonathan Wakely <jwakely@redhat.com>]

On Tue, 18 Apr 2023 at 16:59, Jonathan Wakely via Libstdc++
<libstdc++@gcc.gnu.org> wrote:
> diff --git a/libstdc++-v3/config/abi/pre/gnu.ver b/libstdc++-v3/config/abi/pre/gnu.ver
> index 4ae63094eb7..7c015524b62 100644
> --- a/libstdc++-v3/config/abi/pre/gnu.ver
> +++ b/libstdc++-v3/config/abi/pre/gnu.ver
> @@ -2512,6 +2512,20 @@ GLIBCXX_3.4.31 {
>      _ZNKSt12__shared_ptrINSt10filesystem28recursive_directory_iterator10_Dir_stackELN9__gnu_cxx12_Lock_policyE[012]EEcvbEv;
>      _ZNKSt12__shared_ptrINSt10filesystem7__cxx1128recursive_directory_iterator10_Dir_stackELN9__gnu_cxx12_Lock_policyE[012]EEcvbEv;
>
> +#if defined(_GLIBCXX_SYMVER_GNU) && defined(_GLIBCXX_SHARED) \
> +    && defined(_GLIBCXX_HAVE_AS_SYMVER_DIRECTIVE) \
> +    && defined(_GLIBCXX_HAVE_SYMVER_SYMBOL_RENAMING_RUNTIME_SUPPORT)

I've just noticed that these will never be defined, because this
linker script is preprocessed with config.h not c++config.h, and so it
should be:

#if defined(_GLIBCXX_SYMVER_GNU) && defined(_GLIBCXX_SHARED) \
    && defined(HAVE_AS_SYMVER_DIRECTIVE) \
    && defined(HAVE_SYMVER_SYMBOL_RENAMING_RUNTIME_SUPPORT)


The condition will never be true as currently written (which doesn't
actually seem to matter, but Jakub says that re-exporting the symbols
as the new version is needed in the linker script for older linkers).


> +    # See src/c++98/globals_io.cc
> +    _ZSt3cin;
> +    _ZSt4cout;
> +    _ZSt4cerr;
> +    _ZSt4clog;
> +    _ZSt4wcin;
> +    _ZSt5wcout;
> +    _ZSt5wcerr;
> +    _ZSt5wclog;
> +#endif
> +
>  } GLIBCXX_3.4.30;
>
>  # Symbols in the support library (libsupc++) have their own tag.