On Wed, 19 Jul 2023 at 19:48, Patrick Palka via Libstdc++ < libstd...@gcc.gnu.org> wrote:
> On Tue, 18 Jul 2023, Ken Matsui via Libstdc++ wrote: > > > This patch defines _GLIBCXX_HAS_BUILTIN_TRAIT, which will be used as a > > flag to toggle built-in traits in the type_traits header. Through this > > macro function and _GLIBCXX_NO_BUILTIN_TRAITS macro, we can switch the > > use of built-in traits without needing to modify the source code. > > > > libstdc++-v3/ChangeLog: > > > > * include/bits/c++config (_GLIBCXX_HAS_BUILTIN_TRAIT): Define. > > The ChangeLog entry should also mention the change to _GLIBCXX_HAS_BUILTIN, > e.g. > > (_GLIBCXX_HAS_BUILTIN): Keep defined. > > > > > Signed-off-by: Ken Matsui <kmat...@gcc.gnu.org> > > --- > > libstdc++-v3/include/bits/c++config | 6 +++++- > > 1 file changed, 5 insertions(+), 1 deletion(-) > > > > diff --git a/libstdc++-v3/include/bits/c++config > b/libstdc++-v3/include/bits/c++config > > index dd47f274d5f..de13f61db71 100644 > > --- a/libstdc++-v3/include/bits/c++config > > +++ b/libstdc++-v3/include/bits/c++config > > @@ -854,7 +854,11 @@ namespace __gnu_cxx > > # define _GLIBCXX_HAVE_BUILTIN_LAUNDER 1 > > #endif > > > > -#undef _GLIBCXX_HAS_BUILTIN > > +// Returns true if _GLIBCXX_NO_BUILTIN_TRAITS is not defined and the > compiler > > +// has a corresponding built-in type trait. _GLIBCXX_NO_BUILTIN_TRAITS > is > > +// defined to disable the use of built-in traits. > > +#define _GLIBCXX_HAS_BUILTIN_TRAIT(BT) \ > > + (!defined(_GLIBCXX_NO_BUILTIN_TRAITS) && _GLIBCXX_HAS_BUILTIN(BT)) > > Since we don't expect _GLIBCXX_NO_BUILTIN_TRAITS to get > defined/undefined in the middle of preprocessing, perhaps we should > factor out the _GLIBCXX_NO_BUILTIN_TRAITS test from the macro function > and instead conditionally define the macro function to 0 according > _GLIBCXX_NO_BUILTIN_TRAITS? > Also a macro that expands to a use of `defined` is undefined, see [cpp.cond] p10. GCC allows it, but Clang warns. > > > > // Mark code that should be ignored by the compiler, but seen by > Doxygen. > > #define _GLIBCXX_DOXYGEN_ONLY(X) > > -- > > 2.41.0 > > > > > >
