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
>     >
>     >
>