[PATCH] libstdc++: adjust explicit inst of std::basic_string::data()

[Patrick Palka]

On Wed, 17 Jun 2026, Patrick Palka wrote:

> On Mon, 8 Jun 2026, Marek Polacek wrote:
> 
> > Bootstrapped/regtested on ppc64le-pc-linux-gnu, ok for trunk?
> > 
> > -- >8 --
> > r15-2650 removed noexcept from non-const std::basic_string::data()
> > in bits/cow_string.h, but the explicit instantiations in string-inst.cc
> > kept their noexcept.
> > [except.spec] says that in an explicit instantiation
> > a noexcept-specifier may be specified, but is not required, but when it
> > is specified, it must be the same as the exception specification of all
> > other declarations of that function.  So I think we should just remove it.
> 
> LGTM.  Alternatively we could conditionally add the noexcept depending
> on whether the C++11 or COW std::string is in effect but it's simpler to
> just unconditionally omit it.
> 
> > 
> > libstdc++-v3/ChangeLog:
> > 
> > 	* src/c++17/string-inst.cc (basic_string::data): Remove noexcept.
> > ---
> >  libstdc++-v3/src/c++17/string-inst.cc | 4 ++--
> >  1 file changed, 2 insertions(+), 2 deletions(-)
> > 
> > diff --git a/libstdc++-v3/src/c++17/string-inst.cc b/libstdc++-v3/src/c++17/string-inst.cc
> > index ac52adaa7b5..e9ef1bfd0dc 100644
> > --- a/libstdc++-v3/src/c++17/string-inst.cc
> > +++ b/libstdc++-v3/src/c++17/string-inst.cc
> > @@ -42,14 +42,14 @@ template basic_string<char>::basic_string(__sv_wrapper, const allocator_type&);
> >  template basic_string<char>::__sv_wrapper::__sv_wrapper(string_view);
> >  template string_view basic_string<char>::_S_to_string_view(string_view);
> >  template basic_string<char>::operator string_view() const noexcept;

Should we also remove the noexcept here too, for consistency?

> > -template char* basic_string<char>::data() noexcept;
> > +template char* basic_string<char>::data();
> >  
> >  #ifdef _GLIBCXX_USE_WCHAR_T
> >  template basic_string<wchar_t>::basic_string(__sv_wrapper, const allocator_type&);
> >  template basic_string<wchar_t>::__sv_wrapper::__sv_wrapper(wstring_view);
> >  template wstring_view basic_string<wchar_t>::_S_to_string_view(wstring_view);
> >  template basic_string<wchar_t>::operator wstring_view() const noexcept;
> > -template wchar_t* basic_string<wchar_t>::data() noexcept;
> > +template wchar_t* basic_string<wchar_t>::data();
> >  #endif
> >  
> >  _GLIBCXX_END_NAMESPACE_VERSION
> > 
> > base-commit: 32bbd8849a550ad6f936636476c3ab9be8a58807
> > -- 
> > 2.54.0
> > 
> > 
>