Re: [PATCH] Add missing gnu-versioned-namespace symbols

["François Dumont" <frs.dumont@gmail.com>]

On 02/11/20 3:17 pm, Jonathan Wakely wrote:
> On 01/11/20 20:48 +0100, François Dumont via Libstdc++ wrote:
>> Several tests are failing because of those missing symbols.
>>
>> I understand why we need to export symbols relying in the versioned 
>> namespace but I don't understand why we need to do it for 
>> _GLIBCXX_DEBUG symbols which are not version namespace dependant.
>
> If you don't export the symbol, it can't be found by code linking to
> libstdc++.so.8

So I understand that in versioned namespace mode only 
gnu-versioned-namespace.ver is being used and not gnu.ver.

>
> This linker script is the only one used to build libstdc++.so.8 so all
> symbols that need to be exported by that library have to be exported
> by this script. Nothing exports that debug symbol unless you add it
> here.
>
> What I don't understand is why the __istream_extract symbol isn't
> matched by the wildcard in the extern "C++" block at the top of the
> file.

Maybe for the same reason that the std::__copy_streambufs before this 
one and some others symbols in std::__8 had to be explicitely exported too.

But I don't know it.

>
>> Do you want to backport the Debug symbol ?
>>
>>     libstdc++: Add mising gnu-versioned-namespace symbols
>>
>>     libstdc++-v3/ChangeLog:
>>
>>             * config/abi/pre/gnu-versioned-namespace.ver:
>>             Add __istream_extract and 
>> _Safe_local_iterator_base::_M_attach_single
>>             symbols.
>>
>> Tested under Linux x86_64 versioned namespace.
>>
>> Ok to commit ?
>>
>> François
>>
>
>> diff --git a/libstdc++-v3/config/abi/pre/gnu-versioned-namespace.ver 
>> b/libstdc++-v3/config/abi/pre/gnu-versioned-namespace.ver
>> index 0965854fbc3..3b6d7944d06 100644
>> --- a/libstdc++-v3/config/abi/pre/gnu-versioned-namespace.ver
>> +++ b/libstdc++-v3/config/abi/pre/gnu-versioned-namespace.ver
>> @@ -98,6 +98,9 @@ GLIBCXX_8.0 {
>>     _ZNSt3__817__copy_streambufsI*;
>>     _ZNSt3__821__copy_streambufs_eofI*;
>>
>> +    # std::__istream_extract(wistream&, wchar_t*, streamsize)
>> + 
>> _ZNSt3__817__istream_extractIwNS_11char_traitsIwEEEEvRNS_13basic_istreamIT_T0_EEPS4_[ilx];
>> +
>>     # __gnu_cxx::__atomic_add
>>     # __gnu_cxx::__exchange_and_add
>>     _ZN9__gnu_cxx3__812__atomic_addEPV[il][il];
>> @@ -145,6 +148,7 @@ GLIBCXX_8.0 {
>> _ZN11__gnu_debug30_Safe_unordered_container_base13_M_detach_allEv;
>> _ZN11__gnu_debug25_Safe_local_iterator_base9_M_attachEPNS_19_Safe_sequence_baseEb;
>>     _ZN11__gnu_debug25_Safe_local_iterator_base9_M_detachEv;
>> + 
>> _ZN11__gnu_debug25_Safe_local_iterator_base16_M_attach_singleEPNS_19_Safe_sequence_baseEb;
>>
>>     # parallel mode
>>     _ZN14__gnu_parallel9_Settings3getEv;
>