Re: [PATCH] libstdc++: use __bool_constant instead of integral_constant

[Jonathan Wakely <jwakely@redhat.com>]

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On Thu, 23 Mar 2023 at 02:06, Ken Matsui via Libstdc++ <
libstdc++@gcc.gnu.org> wrote:

> In the type_traits header, both integral_constant<bool> and __bool_constant
> are used.


Yes, this is just because we didn't have __bool_constant originally, and
nobody has needed to touch the traits that still use integral_constant, so
they never got updated.



> This patch unifies those usages into __bool_constant.
>

Thanks, doing this for consistency seems reasonable, and safe to do now
instead of waiting until after the GCC 13 release. I'll test and push the
patch.

Do you have a GCC copyright assignment on file with the FSF?
If not, either you need to complete that paperwork, or add a DCO sign-off
to all your patches:
https://gcc.gnu.org/dco.html


>
> libstdc++-v3/ChangeLog:
>
>         * include/std/type_traits: Use __bool_constant instead of
>         integral_constant.
> ---
>  libstdc++-v3/include/std/type_traits | 32 ++++++++++++++--------------
>  1 file changed, 16 insertions(+), 16 deletions(-)
>
> diff --git a/libstdc++-v3/include/std/type_traits
> b/libstdc++-v3/include/std/type_traits
> index 2bd607a8b8f..bc6982f9e64 100644
> --- a/libstdc++-v3/include/std/type_traits
> +++ b/libstdc++-v3/include/std/type_traits
> @@ -578,19 +578,19 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
>    /// is_enum
>    template<typename _Tp>
>      struct is_enum
> -    : public integral_constant<bool, __is_enum(_Tp)>
> +    : public __bool_constant<__is_enum(_Tp)>
>      { };
>
>    /// is_union
>    template<typename _Tp>
>      struct is_union
> -    : public integral_constant<bool, __is_union(_Tp)>
> +    : public __bool_constant<__is_union(_Tp)>
>      { };
>
>    /// is_class
>    template<typename _Tp>
>      struct is_class
> -    : public integral_constant<bool, __is_class(_Tp)>
> +    : public __bool_constant<__is_class(_Tp)>
>      { };
>
>    /// is_function
> @@ -784,7 +784,7 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
>    /// is_trivial
>    template<typename _Tp>
>      struct is_trivial
> -    : public integral_constant<bool, __is_trivial(_Tp)>
> +    : public __bool_constant<__is_trivial(_Tp)>
>      {
>
>  static_assert(std::__is_complete_or_unbounded(__type_identity<_Tp>{}),
>         "template argument must be a complete class or an unbounded
> array");
> @@ -793,7 +793,7 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
>    /// is_trivially_copyable
>    template<typename _Tp>
>      struct is_trivially_copyable
> -    : public integral_constant<bool, __is_trivially_copyable(_Tp)>
> +    : public __bool_constant<__is_trivially_copyable(_Tp)>
>      {
>
>  static_assert(std::__is_complete_or_unbounded(__type_identity<_Tp>{}),
>         "template argument must be a complete class or an unbounded
> array");
> @@ -802,7 +802,7 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
>    /// is_standard_layout
>    template<typename _Tp>
>      struct is_standard_layout
> -    : public integral_constant<bool, __is_standard_layout(_Tp)>
> +    : public __bool_constant<__is_standard_layout(_Tp)>
>      {
>
>  static_assert(std::__is_complete_or_unbounded(__type_identity<_Tp>{}),
>         "template argument must be a complete class or an unbounded
> array");
> @@ -817,7 +817,7 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
>      struct
>      _GLIBCXX20_DEPRECATED_SUGGEST("is_standard_layout && is_trivial")
>      is_pod
> -    : public integral_constant<bool, __is_pod(_Tp)>
> +    : public __bool_constant<__is_pod(_Tp)>
>      {
>
>  static_assert(std::__is_complete_or_unbounded(__type_identity<_Tp>{}),
>         "template argument must be a complete class or an unbounded
> array");
> @@ -831,7 +831,7 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
>      struct
>      _GLIBCXX17_DEPRECATED
>      is_literal_type
> -    : public integral_constant<bool, __is_literal_type(_Tp)>
> +    : public __bool_constant<__is_literal_type(_Tp)>
>      {
>
>  static_assert(std::__is_complete_or_unbounded(__type_identity<_Tp>{}),
>         "template argument must be a complete class or an unbounded
> array");
> @@ -840,13 +840,13 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
>    /// is_empty
>    template<typename _Tp>
>      struct is_empty
> -    : public integral_constant<bool, __is_empty(_Tp)>
> +    : public __bool_constant<__is_empty(_Tp)>
>      { };
>
>    /// is_polymorphic
>    template<typename _Tp>
>      struct is_polymorphic
> -    : public integral_constant<bool, __is_polymorphic(_Tp)>
> +    : public __bool_constant<__is_polymorphic(_Tp)>
>      { };
>
>  #if __cplusplus >= 201402L
> @@ -855,14 +855,14 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
>    /// @since C++14
>    template<typename _Tp>
>      struct is_final
> -    : public integral_constant<bool, __is_final(_Tp)>
> +    : public __bool_constant<__is_final(_Tp)>
>      { };
>  #endif
>
>    /// is_abstract
>    template<typename _Tp>
>      struct is_abstract
> -    : public integral_constant<bool, __is_abstract(_Tp)>
> +    : public __bool_constant<__is_abstract(_Tp)>
>      { };
>
>    /// @cond undocumented
> @@ -873,7 +873,7 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
>
>    template<typename _Tp>
>      struct __is_signed_helper<_Tp, true>
> -    : public integral_constant<bool, _Tp(-1) < _Tp(0)>
> +    : public __bool_constant<_Tp(-1) < _Tp(0)>
>      { };
>    /// @endcond
>
> @@ -1333,7 +1333,7 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
>    /// has_virtual_destructor
>    template<typename _Tp>
>      struct has_virtual_destructor
> -    : public integral_constant<bool, __has_virtual_destructor(_Tp)>
> +    : public __bool_constant<__has_virtual_destructor(_Tp)>
>      {
>
>  static_assert(std::__is_complete_or_unbounded(__type_identity<_Tp>{}),
>         "template argument must be a complete class or an unbounded
> array");
> @@ -1392,7 +1392,7 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
>    template<typename _Tp, typename _Up>
>      struct is_same
>  #ifdef _GLIBCXX_HAVE_BUILTIN_IS_SAME
> -    : public integral_constant<bool, __is_same(_Tp, _Up)>
> +    : public __bool_constant<__is_same(_Tp, _Up)>
>  #else
>      : public false_type
>  #endif
> @@ -1408,7 +1408,7 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
>    /// is_base_of
>    template<typename _Base, typename _Derived>
>      struct is_base_of
> -    : public integral_constant<bool, __is_base_of(_Base, _Derived)>
> +    : public __bool_constant<__is_base_of(_Base, _Derived)>
>      { };
>
>  #if __has_builtin(__is_convertible)
> --
> 2.40.0
>
>