I've now prepared the patch to support following config:

--disable-libstdcxx-dual-abi --with-default-libstdcxx-abi=new

and so detected yet another problem with src/c++98/compatibility.cc. We 
need basic_istream<>::ignore(streamsize) definitions that rely here but 
not the rest of it.

François

On 17/08/2023 19:17, François Dumont wrote:
>
> Another fix to define __cow_string(const std::string&) in 
> cxx11-stdexcept.cc even if ! _GLIBCXX_USE_DUAL_ABI.
>
> On 13/08/2023 21:51, François Dumont wrote:
>>
>> Here is another version with enhanced sizeof/alignof static_assert in 
>> string-inst.cc for the std::__cow_string definition from <stdexcept>. 
>> The assertions in cow-stdexcept.cc are now checking the definition 
>> which is in the same file.
>>
>> On 13/08/2023 15:27, François Dumont wrote:
>>>
>>> Here is the fixed patch tested in all 3 modes:
>>>
>>> - _GLIBCXX_USE_DUAL_ABI
>>>
>>> - !_GLIBCXX_USE_DUAL_ABI && !_GLIBCXX_USE_CXX11_ABI
>>>
>>> - !_GLIBCXX_USE_DUAL_ABI && _GLIBCXX_USE_CXX11_ABI
>>>
>>> I don't know what you have in mind for the change below but I wanted 
>>> to let you know that I tried to put COW std::basic_string into a 
>>> nested __cow namespace when _GLIBCXX_USE_CXX11_ABI. But it had more 
>>> impact on string-inst.cc so I preferred the macro substitution approach.
>>>
>>> There are some test failing when !_GLIBCXX_USE_CXX11_ABI that are 
>>> unrelated with my changes. I'll propose fixes in coming days.
>>>
>>>     libstdc++: [_GLIBCXX_INLINE_VERSION] Use cxx11 abi [PR83077]
>>>
>>>     Use cxx11 abi when activating versioned namespace mode. To do 
>>> support
>>>     a new configuration mode where !_GLIBCXX_USE_DUAL_ABI and 
>>> _GLIBCXX_USE_CXX11_ABI.
>>>
>>>     The main change is that std::__cow_string is now defined 
>>> whenever _GLIBCXX_USE_DUAL_ABI
>>>     or _GLIBCXX_USE_CXX11_ABI is true. Implementation is using 
>>> available std::string in
>>>     case of dual abi and a subset of it when it's not.
>>>
>>>     On the other side std::__sso_string is defined only when 
>>> _GLIBCXX_USE_DUAL_ABI is true
>>>     and _GLIBCXX_USE_CXX11_ABI is false. Meaning that 
>>> std::__sso_string is a typedef for the
>>>     cow std::string implementation when dual abi is disabled and cow 
>>> string is being used.
>>>
>>>     libstdcxx-v3/ChangeLog:
>>>
>>>             PR libstdc++/83077
>>>             * acinclude.m4 [GLIBCXX_ENABLE_LIBSTDCXX_DUAL_ABI]: 
>>> Default to "new" libstdcxx abi.
>>>             * config/locale/dragonfly/monetary_members.cc 
>>> [!_GLIBCXX_USE_DUAL_ABI]: Define money_base
>>>             members.
>>>             * config/locale/generic/monetary_members.cc 
>>> [!_GLIBCXX_USE_DUAL_ABI]: Likewise.
>>>             * config/locale/gnu/monetary_members.cc 
>>> [!_GLIBCXX_USE_DUAL_ABI]: Likewise.
>>>             * config/locale/gnu/numeric_members.cc
>>> [!_GLIBCXX_USE_DUAL_ABI](__narrow_multibyte_chars): Define.
>>>             * configure: Regenerate.
>>>             * include/bits/c++config
>>> [_GLIBCXX_INLINE_VERSION](_GLIBCXX_NAMESPACE_CXX11, 
>>> _GLIBCXX_BEGIN_NAMESPACE_CXX11):
>>>             Define empty.
>>> [_GLIBCXX_INLINE_VERSION](_GLIBCXX_END_NAMESPACE_CXX11, 
>>> _GLIBCXX_DEFAULT_ABI_TAG):
>>>             Likewise.
>>>             * include/bits/cow_string.h [!_GLIBCXX_USE_CXX11_ABI]: 
>>> Define a light version of COW
>>>             basic_string as __std_cow_string for use in stdexcept.
>>>             * include/std/stdexcept [_GLIBCXX_USE_CXX11_ABI]: Define 
>>> __cow_string.
>>>             (__cow_string(const char*)): New.
>>>             (__cow_string::c_str()): New.
>>>             * python/libstdcxx/v6/printers.py 
>>> (StdStringPrinter::__init__): Set self.new_string to True
>>>             when std::__8::basic_string type is found.
>>>             * src/Makefile.am 
>>> [ENABLE_SYMVERS_GNU_NAMESPACE](ldbl_alt128_compat_sources): Define 
>>> empty.
>>>             * src/Makefile.in: Regenerate.
>>>             * src/c++11/Makefile.am (cxx11_abi_sources): Rename into...
>>>             (dual_abi_sources): ...this. Also move 
>>> cow-local_init.cc, cxx11-hash_tr1.cc,
>>>             cxx11-ios_failure.cc entries to...
>>>             (sources): ...this.
>>>             (extra_string_inst_sources): Move cow-fstream-inst.cc, 
>>> cow-sstream-inst.cc, cow-string-inst.cc,
>>>             cow-string-io-inst.cc, cow-wtring-inst.cc, 
>>> cow-wstring-io-inst.cc, cxx11-locale-inst.cc,
>>>             cxx11-wlocale-inst.cc entries to...
>>>             (inst_sources): ...this.
>>>             * src/c++11/Makefile.in: Regenerate.
>>>             * src/c++11/cow-fstream-inst.cc 
>>> [_GLIBCXX_USE_CXX11_ABI]: Skip definitions.
>>>             * src/c++11/cow-locale_init.cc [_GLIBCXX_USE_CXX11_ABI]: 
>>> Skip definitions.
>>>             * src/c++11/cow-sstream-inst.cc 
>>> [_GLIBCXX_USE_CXX11_ABI]: Skip definitions.
>>>             * src/c++11/cow-stdexcept.cc [_GLIBCXX_USE_CXX11_ABI]: 
>>> Include <bits/cow_string.h>.
>>>             [_GLIBCXX_USE_DUAL_ABI || 
>>> _GLIBCXX_USE_CXX11_ABI](__cow_string): Redefine before
>>>             including <stdexcept>. Define 
>>> _GLIBCXX_DEFINE_STDEXCEPT_INSTANTIATIONS so that
>>>             __cow_string definition in <stdexcept> is skipped.
>>>             [_GLIBCXX_USE_CXX11_ABI]: Skip Transaction Memory TS 
>>> definitions.
>>>             Move static_assert to check std::_cow_string abi layout 
>>> to...
>>>             * src/c++11/string-inst.cc: ...here.
>>>             (_GLIBCXX_DEFINING_CXX11_ABI_INSTANTIATIONS): Define 
>>> following _GLIBCXX_USE_CXX11_ABI
>>>             value.
>>>             [_GLIBCXX_USE_CXX11_ABI && 
>>> !_GLIBCXX_DEFINING_CXX11_ABI_INSTANTIATIONS]:
>>>             Define _GLIBCXX_DEFINING_COW_STRING_INSTANTIATIONS. 
>>> Include <bits/cow_string.h>.
>>>             Define basic_string as __std_cow_string for the current 
>>> translation unit.
>>>             * src/c++11/cow-string-inst.cc [_GLIBCXX_USE_CXX11_ABI]: 
>>> Skip definitions.
>>>             * src/c++11/cow-string-io-inst.cc 
>>> [_GLIBCXX_USE_CXX11_ABI]: Skip definitions.
>>>             * src/c++11/cow-wstring-inst.cc 
>>> [_GLIBCXX_USE_CXX11_ABI]: Skip definitions.
>>>             * src/c++11/cow-wstring-io-inst.cc 
>>> [_GLIBCXX_USE_CXX11_ABI]: Skip definitions.
>>>             * src/c++11/cxx11-hash_tr1.cc [!_GLIBCXX_USE_CXX11_ABI]: 
>>> Skip definitions.
>>>             * src/c++11/cxx11-ios_failure.cc 
>>> [!_GLIBCXX_USE_CXX11_ABI]: Skip definitions.
>>>             [!_GLIBCXX_USE_DUAL_ABI] (__ios_failure): Remove.
>>>             * src/c++11/cxx11-locale-inst.cc: Cleanup, just include 
>>> locale-inst.cc.
>>>             * src/c++11/cxx11-stdexcept.cc 
>>> [!_GLIBCXX_USE_CXX11_ABI]: Skip definitions.
>>>             * src/c++11/cxx11-wlocale-inst.cc 
>>> [!_GLIBCXX_USE_CXX11_ABI]: Skip definitions.
>>>             * src/c++11/locale-inst-numeric.h
>>> [!_GLIBCXX_USE_DUAL_ABI](std::use_facet<num_get<>>, 
>>> std::use_facet<num_put<>>): Instantiate.
>>> [!_GLIBCXX_USE_DUAL_ABI](std::has_facet<num_get<>>, 
>>> std::has_facet<num_put<>>): Instantiate.
>>>             [!_GLIBCXX_USE_DUAL_ABI](std::num_get<C, 
>>> istreambuf_iterator<C>>): Instantiate.
>>>             [!_GLIBCXX_USE_DUAL_ABI](std::num_put<C, 
>>> ostreambuf_iterator<C>>): Instantiate.
>>>             * src/c++11/locale-inst.cc [!_GLIBCXX_USE_DUAL_ABI]: 
>>> Build only when configured
>>>             _GLIBCXX_USE_CXX11_ABI is equal to currently built abi.
>>> [!_GLIBCXX_USE_DUAL_ABI](__moneypunct_cache<C, false>): Instantiate.
>>> [!_GLIBCXX_USE_DUAL_ABI](__moneypunct_cache<C, true>): Instantiate.
>>> [!_GLIBCXX_USE_DUAL_ABI](__numpunct_cache<C>): Instantiate.
>>>             [!_GLIBCXX_USE_DUAL_ABI](__timepunct<C>): Instantiate.
>>> [!_GLIBCXX_USE_DUAL_ABI](__timepunct_cache<C>): Instantiate.
>>>             [!_GLIBCXX_USE_DUAL_ABI](time_put<C, 
>>> ostreambuf_iterator<C>>): Instantiate.
>>>             [!_GLIBCXX_USE_DUAL_ABI](time_put_byname<C, 
>>> ostreambuf_iterator<C>>): Instantiate.
>>> [!_GLIBCXX_USE_DUAL_ABI](__ctype_abstract_base<C>): Instantiate.
>>>             [!_GLIBCXX_USE_DUAL_ABI](ctype_byname<C>): Instantiate.
>>> [!_GLIBCXX_USE_DUAL_ABI](__codecvt_abstract_base<C, char, 
>>> mbstate_t>): Instantiate.
>>>             [!_GLIBCXX_USE_DUAL_ABI](codecvt_byname<C, char, 
>>> mbstate_t>): Instantiate.
>>> [!_GLIBCXX_USE_DUAL_ABI](use_facet<ctype<C>>(const locale&)): 
>>> Instantiate.
>>> [!_GLIBCXX_USE_DUAL_ABI](use_facet<codecvt<C, char, 
>>> mbstate_t>>(const locale&)): Instantiate.
>>> [!_GLIBCXX_USE_DUAL_ABI](use_facet<__timepunct<C>>(const locale&)): 
>>> Instantiate.
>>> [!_GLIBCXX_USE_DUAL_ABI](use_facet<time_put<C>>(const locale&)): 
>>> Instantiate.
>>> [!_GLIBCXX_USE_DUAL_ABI](has_facet<ctype<C>>(const locale&)): 
>>> Instantiate.
>>> [!_GLIBCXX_USE_DUAL_ABI](has_facet<codecvt<C, char, 
>>> mbstate_t>>(const locale&)): Instantiate.
>>> [!_GLIBCXX_USE_DUAL_ABI](has_facet<__timepunct<C>>(const locale&)): 
>>> Instantiate.
>>> [!_GLIBCXX_USE_DUAL_ABI](has_facet<time_put<C>>(const locale&)): 
>>> Instantiate.
>>> [!_GLIBCXX_USE_DUAL_ABI](__add_grouping<C>): Define.
>>>             [!_GLIBCXX_USE_DUAL_ABI](__pad<C, char_traits<C>>): 
>>> Instantiate.
>>>             [!_GLIBCXX_USE_DUAL_ABI](__int_to_char(C*, unsigned 
>>> long, const C*,
>>>             ios_base::fmtflags, bool)): Define.
>>>             [!_GLIBCXX_USE_DUAL_ABI](__int_to_char(C*, unsigned long 
>>> long, const C*,
>>>             ios_base::fmtflags, bool)): Define.
>>>             * src/c++11/wlocale-inst.cc [!_GLIBCXX_USE_CXX11_ABI]: 
>>> Skip definitions.
>>>             * src/c++98/Makefile.am (cxx11_abi_sources): Remove, 
>>> unique cow-istream-string.cc entry
>>>             move to...
>>>             (inst_sources): ...this.
>>>             * src/c++98/Makefile.in: Regenerate.
>>>             * src/c++98/cow-istream-string.cc: Include 
>>> <bits/c++config.h>.
>>>             [_GLIBCXX_USE_CXX11_ABI]: Skip definitions.
>>>             * src/c++98/hash_tr1.cc [_GLIBCXX_USE_CXX11_ABI]: Skip 
>>> definitions.
>>>             * src/c++98/ios_failure.cc 
>>> [_GLIBCXX_USE_CXX11_ABI][_GLIBCXX_USE_DUAL_ABI]: Skip definitions.
>>>             * src/c++98/istream-string.cc [!_GLIBCXX_USE_DUAL_ABI]: 
>>> Build only when configured
>>>             _GLIBCXX_USE_CXX11_ABI is equal to currently built abi.
>>>             * src/c++98/locale_facets.cc 
>>> [_GLIBCXX_USE_CXX11_ABI](__verify_grouping): Remove.
>>>             * src/c++98/stdexcept.cc
>>>             [_GLIBCXX_USE_CXX11_ABI](logic_error(const string&): Remove.
>>>             [_GLIBCXX_USE_CXX11_ABI](domain_error(const string&): 
>>> Remove.
>>>             [_GLIBCXX_USE_CXX11_ABI](invalid_argument(const 
>>> string&): Remove.
>>>             [_GLIBCXX_USE_CXX11_ABI](length_error(const string&): 
>>> Remove.
>>>             [_GLIBCXX_USE_CXX11_ABI](out_of_range(const string&): 
>>> Remove.
>>>             [_GLIBCXX_USE_CXX11_ABI](runtime_error(const string&): 
>>> Remove.
>>>             [_GLIBCXX_USE_CXX11_ABI](range_error(const string&): Remove.
>>>             [_GLIBCXX_USE_CXX11_ABI](overflow_error(const string&): 
>>> Remove.
>>>             [_GLIBCXX_USE_CXX11_ABI](underflow_error(const string&): 
>>> Remove.
>>>
>>> Ok to commit ?
>>>
>>> François
>>>
>>> On 11/08/2023 09:51, Jonathan Wakely wrote:
>>>>
>>>>
>>>> On Fri, 11 Aug 2023, 06:44 François Dumont via Libstdc++, 
>>>> <libstdc++@gcc.gnu.org <mailto:libstdc%2B%2B@gcc.gnu.org>> wrote:
>>>>
>>>>     I hadn't tested the most basic default configuration and it is
>>>>     failing,
>>>>
>>>>
>>>> I did wonder about that when you said which configurations you had 
>>>> tested :)
>>>>
>>>>
>>>>
>>>>
>>>>     I need some more time yet.
>>>>
>>>>
>>>> OK, no problem.
>>>>
>>>> I actually have an idea for replacing the __cow_string hack with 
>>>> something better, which I will try to work on next week. That might 
>>>> make things simpler for you, as you won't need the __std_cow_string 
>>>> macro.
>>>>
>>>>
>>>>
>>>>
>>>>
>>>>     François
>>>>
>>>>
>>>>     On 10/08/2023 07:13, François Dumont wrote:
>>>>     > Hi
>>>>     >
>>>>     > I've eventually completed this work.
>>>>     >
>>>>     > This evolution will allow to build libstdc++ without dual abi
>>>>     and
>>>>     > using cxx11 abi. For the moment such a config is only accessible
>>>>     > through the --enable-symvers=gnu-versioned-namespace
>>>>     configuration.
>>>>     >
>>>>     >     libstdc++: [_GLIBCXX_INLINE_VERSION] Use cxx11 abi [PR83077]
>>>>     >
>>>>     >     Use cxx11 abi when activating versioned namespace mode.
>>>>     >
>>>>     >     libstdcxx-v3/ChangeLog:
>>>>     >
>>>>     >             PR libstdc++/83077
>>>>     >             * acinclude.m4 [GLIBCXX_ENABLE_LIBSTDCXX_DUAL_ABI]:
>>>>     > Default to "new" libstdcxx abi.
>>>>     >             * config/locale/dragonfly/monetary_members.cc
>>>>     > [!_GLIBCXX_USE_DUAL_ABI]: Define money_base
>>>>     >             members.
>>>>     >             * config/locale/generic/monetary_members.cc
>>>>     > [!_GLIBCXX_USE_DUAL_ABI]: Likewise.
>>>>     >             * config/locale/gnu/monetary_members.cc
>>>>     > [!_GLIBCXX_USE_DUAL_ABI]: Likewise.
>>>>     >             * config/locale/gnu/numeric_members.cc
>>>>     > [!_GLIBCXX_USE_DUAL_ABI](__narrow_multibyte_chars): Define.
>>>>     >             * configure: Regenerate.
>>>>     >             * include/bits/c++config
>>>>     > [_GLIBCXX_INLINE_VERSION](_GLIBCXX_NAMESPACE_CXX11,
>>>>     > _GLIBCXX_BEGIN_NAMESPACE_CXX11):
>>>>     >             Define empty.
>>>>     > [_GLIBCXX_INLINE_VERSION](_GLIBCXX_END_NAMESPACE_CXX11,
>>>>     > _GLIBCXX_DEFAULT_ABI_TAG):
>>>>     >             Likewise.
>>>>     >             * include/bits/cow_string.h
>>>>     [!_GLIBCXX_USE_CXX11_ABI]:
>>>>     > Define a light version of COW
>>>>     >             basic_string as __std_cow_string for use in
>>>>     stdexcept.
>>>>     >             * include/std/stdexcept [_GLIBCXX_USE_CXX11_ABI]:
>>>>     Define
>>>>     > __cow_string.
>>>>     >             (__cow_string(const char*)): New.
>>>>     >             (__cow_string::c_str()): New.
>>>>     >             * python/libstdcxx/v6/printers.py
>>>>     > (StdStringPrinter::__init__): Set self.new_string to True
>>>>     >             when std::__8::basic_string type is found.
>>>>     >             * src/Makefile.am
>>>>     > [ENABLE_SYMVERS_GNU_NAMESPACE](ldbl_alt128_compat_sources):
>>>>     Define empty.
>>>>     >             * src/Makefile.in: Regenerate.
>>>>     >             * src/c++11/Makefile.am (cxx11_abi_sources):
>>>>     Rename into...
>>>>     >             (dual_abi_sources): ...this. Also move
>>>>     cow-local_init.cc,
>>>>     > cxx11-hash_tr1.cc,
>>>>     >             cxx11-ios_failure.cc entries to...
>>>>     >             (sources): ...this.
>>>>     >             (extra_string_inst_sources): Move
>>>>     cow-fstream-inst.cc,
>>>>     > cow-sstream-inst.cc, cow-string-inst.cc,
>>>>     >             cow-string-io-inst.cc, cow-wtring-inst.cc,
>>>>     > cow-wstring-io-inst.cc, cxx11-locale-inst.cc,
>>>>     >             cxx11-wlocale-inst.cc entries to...
>>>>     >             (inst_sources): ...this.
>>>>     >             * src/c++11/Makefile.in: Regenerate.
>>>>     >             * src/c++11/cow-fstream-inst.cc
>>>>     [_GLIBCXX_USE_CXX11_ABI]:
>>>>     > Skip definitions.
>>>>     >             * src/c++11/cow-locale_init.cc
>>>>     [_GLIBCXX_USE_CXX11_ABI]:
>>>>     > Skip definitions.
>>>>     >             * src/c++11/cow-sstream-inst.cc
>>>>     [_GLIBCXX_USE_CXX11_ABI]:
>>>>     > Skip definitions.
>>>>     >             * src/c++11/cow-stdexcept.cc
>>>>     [_GLIBCXX_USE_CXX11_ABI]:
>>>>     > Include <bits/cow_string.h>.
>>>>     >             [_GLIBCXX_USE_DUAL_ABI ||
>>>>     > _GLIBCXX_USE_CXX11_ABI](__cow_string): Redefine before including
>>>>     >             <stdexcept>. Define
>>>>     > _GLIBCXX_DEFINE_STDEXCEPT_INSTANTIATIONS so that __cow_string
>>>>     definition
>>>>     >             in <stdexcept> is skipped.
>>>>     >             [_GLIBCXX_USE_CXX11_ABI]: Skip Transaction Memory TS
>>>>     > definitions.
>>>>     >             * src/c++11/cow-string-inst.cc
>>>>     [_GLIBCXX_USE_CXX11_ABI]:
>>>>     > Skip definitions.
>>>>     >             * src/c++11/cow-string-io-inst.cc
>>>>     > [_GLIBCXX_USE_CXX11_ABI]: Skip definitions.
>>>>     >             * src/c++11/cow-wstring-inst.cc
>>>>     [_GLIBCXX_USE_CXX11_ABI]:
>>>>     > Skip definitions.
>>>>     >             * src/c++11/cow-wstring-io-inst.cc
>>>>     > [_GLIBCXX_USE_CXX11_ABI]: Skip definitions.
>>>>     >             * src/c++11/cxx11-hash_tr1.cc
>>>>     [!_GLIBCXX_USE_CXX11_ABI]:
>>>>     > Skip definitions.
>>>>     >             * src/c++11/cxx11-ios_failure.cc
>>>>     > [!_GLIBCXX_USE_CXX11_ABI]: Skip definitions.
>>>>     >             [!_GLIBCXX_USE_DUAL_ABI] (__ios_failure): Remove.
>>>>     >             * src/c++11/cxx11-locale-inst.cc: Cleanup, just
>>>>     include
>>>>     > locale-inst.cc.
>>>>     >             * src/c++11/cxx11-stdexcept.cc
>>>>     [!_GLIBCXX_USE_CXX11_ABI]:
>>>>     > Skip definitions.
>>>>     >             * src/c++11/cxx11-wlocale-inst.cc
>>>>     > [!_GLIBCXX_USE_CXX11_ABI]: Skip definitions.
>>>>     >             * src/c++11/locale-inst-numeric.h
>>>>     > [!_GLIBCXX_USE_DUAL_ABI](std::use_facet<num_get<>>,
>>>>     > std::use_facet<num_put<>>): Instantiate.
>>>>     > [!_GLIBCXX_USE_DUAL_ABI](std::has_facet<num_get<>>,
>>>>     > std::has_facet<num_put<>>): Instantiate.
>>>>     > [!_GLIBCXX_USE_DUAL_ABI](std::num_get<C,
>>>>     > istreambuf_iterator<C>>): Instantiate.
>>>>     > [!_GLIBCXX_USE_DUAL_ABI](std::num_put<C,
>>>>     > ostreambuf_iterator<C>>): Instantiate.
>>>>     >             * src/c++11/locale-inst.cc
>>>>     [!_GLIBCXX_USE_DUAL_ABI]: Build
>>>>     > only when configured
>>>>     >             _GLIBCXX_USE_CXX11_ABI is equal to currently
>>>>     built abi.
>>>>     > [!_GLIBCXX_USE_DUAL_ABI](__moneypunct_cache<C, false>):
>>>>     > Instantiate.
>>>>     > [!_GLIBCXX_USE_DUAL_ABI](__moneypunct_cache<C, true>):
>>>>     > Instantiate.
>>>>     > [!_GLIBCXX_USE_DUAL_ABI](__numpunct_cache<C>): Instantiate.
>>>>     > [!_GLIBCXX_USE_DUAL_ABI](__timepunct<C>): Instantiate.
>>>>     > [!_GLIBCXX_USE_DUAL_ABI](__timepunct_cache<C>): Instantiate.
>>>>     > [!_GLIBCXX_USE_DUAL_ABI](time_put<C,
>>>>     > ostreambuf_iterator<C>>): Instantiate.
>>>>     > [!_GLIBCXX_USE_DUAL_ABI](time_put_byname<C,
>>>>     > ostreambuf_iterator<C>>): Instantiate.
>>>>     > [!_GLIBCXX_USE_DUAL_ABI](__ctype_abstract_base<C>): Instantiate.
>>>>     > [!_GLIBCXX_USE_DUAL_ABI](ctype_byname<C>): Instantiate.
>>>>     > [!_GLIBCXX_USE_DUAL_ABI](__codecvt_abstract_base<C, char,
>>>>     > mbstate_t>): Instantiate.
>>>>     > [!_GLIBCXX_USE_DUAL_ABI](codecvt_byname<C, char,
>>>>     > mbstate_t>): Instantiate.
>>>>     > [!_GLIBCXX_USE_DUAL_ABI](codecvt_byname<C, char,
>>>>     > mbstate_t>): Instantiate.
>>>>     > [!_GLIBCXX_USE_DUAL_ABI](use_facet<ctype<C>>(const locale&)):
>>>>     > Instantiate.
>>>>     > [!_GLIBCXX_USE_DUAL_ABI](use_facet<codecvt<C, char,
>>>>     > mbstate_t>>(const locale&)): Instantiate.
>>>>     > [!_GLIBCXX_USE_DUAL_ABI](use_facet<__timepunct<C>>(const
>>>>     locale&)):
>>>>     > Instantiate.
>>>>     > [!_GLIBCXX_USE_DUAL_ABI](use_facet<time_put<C>>(const locale&)):
>>>>     > Instantiate.
>>>>     > [!_GLIBCXX_USE_DUAL_ABI](has_facet<ctype<C>>(const locale&)):
>>>>     > Instantiate.
>>>>     > [!_GLIBCXX_USE_DUAL_ABI](has_facet<codecvt<C, char,
>>>>     > mbstate_t>>(const locale&)): Instantiate.
>>>>     > [!_GLIBCXX_USE_DUAL_ABI](has_facet<__timepunct<C>>(const
>>>>     locale&)):
>>>>     > Instantiate.
>>>>     > [!_GLIBCXX_USE_DUAL_ABI](has_facet<time_put<C>>(const locale&)):
>>>>     > Instantiate.
>>>>     > [!_GLIBCXX_USE_DUAL_ABI](__add_grouping<C>): Define.
>>>>     > [!_GLIBCXX_USE_DUAL_ABI](__pad<C, char_traits<C>>):
>>>>     > Instantiate.
>>>>     > [!_GLIBCXX_USE_DUAL_ABI](__int_to_char(C*, unsigned long,
>>>>     > const C*,
>>>>     >             ios_base::fmtflags, bool)): Define.
>>>>     > [!_GLIBCXX_USE_DUAL_ABI](__int_to_char(C*, unsigned long
>>>>     > long, const C*,
>>>>     >             ios_base::fmtflags, bool)): Define.
>>>>     >             * src/c++11/string-inst.cc
>>>>     > (_GLIBCXX_DEFINING_CXX11_ABI_INSTANTIATIONS): Define following
>>>>     >             _GLIBCXX_USE_CXX11_ABI value.
>>>>     >             [_GLIBCXX_USE_CXX11_ABI &&
>>>>     > !_GLIBCXX_DEFINING_CXX11_ABI_INSTANTIATIONS]:
>>>>     >             Define _GLIBCXX_DEFINING_COW_STRING_INSTANTIATIONS.
>>>>     > Include <bits/cow_string.h>.
>>>>     >             Define basic_string as __std_cow_string for the
>>>>     current
>>>>     > translation unit.
>>>>     >             * src/c++11/wlocale-inst.cc
>>>>     [!_GLIBCXX_USE_CXX11_ABI]:
>>>>     > Skip definitions.
>>>>     >             * src/c++98/Makefile.am (cxx11_abi_sources): Remove,
>>>>     > unique cow-istream-string.cc entry
>>>>     >             move to...
>>>>     >             (inst_sources): ...this.
>>>>     >             * src/c++98/Makefile.in: Regenerate.
>>>>     >             * src/c++98/cow-istream-string.cc: Include
>>>>     > <bits/c++config.h>.
>>>>     >             [_GLIBCXX_USE_CXX11_ABI]: Skip definitions.
>>>>     >             * src/c++98/hash_tr1.cc [_GLIBCXX_USE_CXX11_ABI]:
>>>>     Skip
>>>>     > definitions.
>>>>     >             * src/c++98/ios_failure.cc
>>>>     > [_GLIBCXX_USE_CXX11_ABI][_GLIBCXX_USE_DUAL_ABI]: Skip
>>>>     definitions.
>>>>     >             * src/c++98/istream-string.cc
>>>>     [!_GLIBCXX_USE_DUAL_ABI]:
>>>>     > Build only when configured
>>>>     >             _GLIBCXX_USE_CXX11_ABI is equal to currently
>>>>     built abi.
>>>>     >             * src/c++98/locale_facets.cc
>>>>     > [_GLIBCXX_USE_CXX11_ABI](__verify_grouping): Remove.
>>>>     >             * src/c++98/stdexcept.cc
>>>>     > [_GLIBCXX_USE_CXX11_ABI](logic_error(const string&): Remove.
>>>>     > [_GLIBCXX_USE_CXX11_ABI](domain_error(const string&): Remove.
>>>>     > [_GLIBCXX_USE_CXX11_ABI](invalid_argument(const string&):
>>>>     > Remove.
>>>>     > [_GLIBCXX_USE_CXX11_ABI](length_error(const string&): Remove.
>>>>     > [_GLIBCXX_USE_CXX11_ABI](out_of_range(const string&): Remove.
>>>>     > [_GLIBCXX_USE_CXX11_ABI](runtime_error(const string&):
>>>>     > Remove.
>>>>     > [_GLIBCXX_USE_CXX11_ABI](range_error(const string&): Remove.
>>>>     > [_GLIBCXX_USE_CXX11_ABI](overflow_error(const string&):
>>>>     > Remove.
>>>>     > [_GLIBCXX_USE_CXX11_ABI](underflow_error(const string&):
>>>>     > Remove.
>>>>     >
>>>>     > Tested under linux x86_64 with following configs:
>>>>     >
>>>>     > --enable-symvers=gnu-versioned-namespace
>>>>     >
>>>>     > --disable-libstdcxx-dual-abi
>>>>     >
>>>>     > Ok to commit ?
>>>>     >
>>>>     > François
>>>>     >
>>>>     >
>>>>