[PATCH] libstdc++: Define _GLIBCXX_HAS_BUILTIN_TRAIT

[PATCH] libstdc++: Define _GLIBCXX_HAS_BUILTIN_TRAIT

[Ken Matsui]

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.

Signed-off-by: Ken Matsui <kmatsui@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))
 
 // Mark code that should be ignored by the compiler, but seen by Doxygen.
 #define _GLIBCXX_DOXYGEN_ONLY(X)
-- 
2.41.0

Re: [PATCH] libstdc++: Define _GLIBCXX_HAS_BUILTIN_TRAIT

[Patrick Palka]

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 <kmatsui@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?

>  
>  // Mark code that should be ignored by the compiler, but seen by Doxygen.
>  #define _GLIBCXX_DOXYGEN_ONLY(X)
> -- 
> 2.41.0
> 
> 

Re: [PATCH] libstdc++: Define _GLIBCXX_HAS_BUILTIN_TRAIT

[Ken Matsui]

On Wed, Jul 19, 2023 at 11:48 AM Patrick Palka <ppalka@redhat.com> 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 <kmatsui@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?
>
Hi, thank you for your review! I totally agree with your ideas and
will update this patch.

> >
> >  // Mark code that should be ignored by the compiler, but seen by Doxygen.
> >  #define _GLIBCXX_DOXYGEN_ONLY(X)
> > --
> > 2.41.0
> >
> >
>

[PATCH v2] libstdc++: Define _GLIBCXX_HAS_BUILTIN_TRAIT

[Ken Matsui]

This patch defines _GLIBCXX_HAS_BUILTIN_TRAIT macro, which will be used
as a flag to toggle the use of built-in traits in the type_traits header
through _GLIBCXX_NO_BUILTIN_TRAITS macro, without needing to modify the
source code.

libstdc++-v3/ChangeLog:

	* include/bits/c++config (_GLIBCXX_HAS_BUILTIN_TRAIT): Define.
	(_GLIBCXX_HAS_BUILTIN): Keep defined.

Signed-off-by: Ken Matsui <kmatsui@gcc.gnu.org>
---
 libstdc++-v3/include/bits/c++config | 10 +++++++++-
 1 file changed, 9 insertions(+), 1 deletion(-)

diff --git a/libstdc++-v3/include/bits/c++config b/libstdc++-v3/include/bits/c++config
index dd47f274d5f..984985d6fff 100644
--- a/libstdc++-v3/include/bits/c++config
+++ b/libstdc++-v3/include/bits/c++config
@@ -854,7 +854,15 @@ namespace __gnu_cxx
 # define _GLIBCXX_HAVE_BUILTIN_LAUNDER 1
 #endif
 
-#undef _GLIBCXX_HAS_BUILTIN
+// Returns 1 if _GLIBCXX_NO_BUILTIN_TRAITS is not defined and the compiler
+// has a corresponding built-in type trait, 0 otherwise.
+// _GLIBCXX_NO_BUILTIN_TRAITS can be defined to disable the use of built-in
+// traits.
+#ifndef _GLIBCXX_NO_BUILTIN_TRAITS
+# define _GLIBCXX_HAS_BUILTIN_TRAIT(BT) _GLIBCXX_HAS_BUILTIN(BT)
+#else
+# define _GLIBCXX_HAS_BUILTIN_TRAIT(BT) 0
+#endif
 
 // Mark code that should be ignored by the compiler, but seen by Doxygen.
 #define _GLIBCXX_DOXYGEN_ONLY(X)
-- 
2.41.0

Re: [PATCH v2] libstdc++: Define _GLIBCXX_HAS_BUILTIN_TRAIT

[Patrick Palka]

On Wed, Jul 19, 2023 at 3:33 PM Ken Matsui via Gcc-patches
<gcc-patches@gcc.gnu.org> wrote:
>
> This patch defines _GLIBCXX_HAS_BUILTIN_TRAIT macro, which will be used
> as a flag to toggle the use of built-in traits in the type_traits header
> through _GLIBCXX_NO_BUILTIN_TRAITS macro, without needing to modify the
> source code.

LGTM!

>
> libstdc++-v3/ChangeLog:
>
>         * include/bits/c++config (_GLIBCXX_HAS_BUILTIN_TRAIT): Define.
>         (_GLIBCXX_HAS_BUILTIN): Keep defined.
>
> Signed-off-by: Ken Matsui <kmatsui@gcc.gnu.org>
> ---
>  libstdc++-v3/include/bits/c++config | 10 +++++++++-
>  1 file changed, 9 insertions(+), 1 deletion(-)
>
> diff --git a/libstdc++-v3/include/bits/c++config b/libstdc++-v3/include/bits/c++config
> index dd47f274d5f..984985d6fff 100644
> --- a/libstdc++-v3/include/bits/c++config
> +++ b/libstdc++-v3/include/bits/c++config
> @@ -854,7 +854,15 @@ namespace __gnu_cxx
>  # define _GLIBCXX_HAVE_BUILTIN_LAUNDER 1
>  #endif
>
> -#undef _GLIBCXX_HAS_BUILTIN
> +// Returns 1 if _GLIBCXX_NO_BUILTIN_TRAITS is not defined and the compiler
> +// has a corresponding built-in type trait, 0 otherwise.
> +// _GLIBCXX_NO_BUILTIN_TRAITS can be defined to disable the use of built-in
> +// traits.
> +#ifndef _GLIBCXX_NO_BUILTIN_TRAITS
> +# define _GLIBCXX_HAS_BUILTIN_TRAIT(BT) _GLIBCXX_HAS_BUILTIN(BT)
> +#else
> +# define _GLIBCXX_HAS_BUILTIN_TRAIT(BT) 0
> +#endif
>
>  // Mark code that should be ignored by the compiler, but seen by Doxygen.
>  #define _GLIBCXX_DOXYGEN_ONLY(X)
> --
> 2.41.0
>

[PATCH v3 1/2] libstdc++: Define _GLIBCXX_HAS_BUILTIN_TRAIT

[Ken Matsui]

This patch defines _GLIBCXX_HAS_BUILTIN_TRAIT macro, which will be used
as a flag to toggle the use of built-in traits in the type_traits header
through _GLIBCXX_NO_BUILTIN_TRAITS macro, without needing to modify the
source code.

libstdc++-v3/ChangeLog:

	* include/bits/c++config (_GLIBCXX_HAS_BUILTIN_TRAIT): Define.
	(_GLIBCXX_HAS_BUILTIN): Keep defined.

Signed-off-by: Ken Matsui <kmatsui@gcc.gnu.org>
---
 libstdc++-v3/include/bits/c++config | 10 +++++++++-
 1 file changed, 9 insertions(+), 1 deletion(-)

diff --git a/libstdc++-v3/include/bits/c++config b/libstdc++-v3/include/bits/c++config
index dd47f274d5f..984985d6fff 100644
--- a/libstdc++-v3/include/bits/c++config
+++ b/libstdc++-v3/include/bits/c++config
@@ -854,7 +854,15 @@ namespace __gnu_cxx
 # define _GLIBCXX_HAVE_BUILTIN_LAUNDER 1
 #endif
 
-#undef _GLIBCXX_HAS_BUILTIN
+// Returns 1 if _GLIBCXX_NO_BUILTIN_TRAITS is not defined and the compiler
+// has a corresponding built-in type trait, 0 otherwise.
+// _GLIBCXX_NO_BUILTIN_TRAITS can be defined to disable the use of built-in
+// traits.
+#ifndef _GLIBCXX_NO_BUILTIN_TRAITS
+# define _GLIBCXX_HAS_BUILTIN_TRAIT(BT) _GLIBCXX_HAS_BUILTIN(BT)
+#else
+# define _GLIBCXX_HAS_BUILTIN_TRAIT(BT) 0
+#endif
 
 // Mark code that should be ignored by the compiler, but seen by Doxygen.
 #define _GLIBCXX_DOXYGEN_ONLY(X)
-- 
2.41.0

[PATCH v3 2/2] libstdc++: Use _GLIBCXX_HAS_BUILTIN_TRAIT

[Ken Matsui]

This patch uses _GLIBCXX_HAS_BUILTIN_TRAIT macro instead of
__has_builtin in the type_traits header. This macro supports to toggle
the use of built-in traits in the type_traits header through
_GLIBCXX_NO_BUILTIN_TRAITS macro, without needing to modify the
source code.

libstdc++-v3/ChangeLog:

	* include/std/type_traits (__has_builtin): Replace with ...
	(_GLIBCXX_HAS_BUILTIN): ... this.

Signed-off-by: Ken Matsui <kmatsui@gcc.gnu.org>
---
 libstdc++-v3/include/std/type_traits | 26 +++++++++++++-------------
 1 file changed, 13 insertions(+), 13 deletions(-)

diff --git a/libstdc++-v3/include/std/type_traits b/libstdc++-v3/include/std/type_traits
index 9f086992ebc..12423361b6e 100644
--- a/libstdc++-v3/include/std/type_traits
+++ b/libstdc++-v3/include/std/type_traits
@@ -1411,7 +1411,7 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
     : public __bool_constant<__is_base_of(_Base, _Derived)>
     { };
 
-#if __has_builtin(__is_convertible)
+#if _GLIBCXX_HAS_BUILTIN_TRAIT(__is_convertible)
   template<typename _From, typename _To>
     struct is_convertible
     : public __bool_constant<__is_convertible(_From, _To)>
@@ -1462,7 +1462,7 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
 #if __cplusplus >= 202002L
 #define __cpp_lib_is_nothrow_convertible 201806L
 
-#if __has_builtin(__is_nothrow_convertible)
+#if _GLIBCXX_HAS_BUILTIN_TRAIT(__is_nothrow_convertible)
   /// is_nothrow_convertible_v
   template<typename _From, typename _To>
     inline constexpr bool is_nothrow_convertible_v
@@ -1537,7 +1537,7 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
     { using type = _Tp; };
 
   /// remove_cv
-#if __has_builtin(__remove_cv)
+#if _GLIBCXX_HAS_BUILTIN_TRAIT(__remove_cv)
   template<typename _Tp>
     struct remove_cv
     { using type = __remove_cv(_Tp); };
@@ -1606,7 +1606,7 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
   // Reference transformations.
 
   /// remove_reference
-#if __has_builtin(__remove_reference)
+#if _GLIBCXX_HAS_BUILTIN_TRAIT(__remove_reference)
   template<typename _Tp>
     struct remove_reference
     { using type = __remove_reference(_Tp); };
@@ -2963,7 +2963,7 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
       template<typename _Tp,
 	       bool _Nothrow = noexcept(_S_conv<_Tp>(_S_get())),
 	       typename = decltype(_S_conv<_Tp>(_S_get())),
-#if __has_builtin(__reference_converts_from_temporary)
+#if _GLIBCXX_HAS_BUILTIN_TRAIT(__reference_converts_from_temporary)
 	       bool _Dangle = __reference_converts_from_temporary(_Tp, _Res_t)
 #else
 	       bool _Dangle = false
@@ -3420,7 +3420,7 @@ template<typename _Ret, typename _Fn, typename... _Args>
    */
 #define __cpp_lib_remove_cvref 201711L
 
-#if __has_builtin(__remove_cvref)
+#if _GLIBCXX_HAS_BUILTIN_TRAIT(__remove_cvref)
   template<typename _Tp>
     struct remove_cvref
     { using type = __remove_cvref(_Tp); };
@@ -3515,7 +3515,7 @@ template<typename _Ret, typename _Fn, typename... _Args>
     : public bool_constant<is_unbounded_array_v<_Tp>>
     { };
 
-#if __has_builtin(__is_layout_compatible)
+#if _GLIBCXX_HAS_BUILTIN_TRAIT(__is_layout_compatible)
 
   /// @since C++20
   template<typename _Tp, typename _Up>
@@ -3529,7 +3529,7 @@ template<typename _Ret, typename _Fn, typename... _Args>
     constexpr bool is_layout_compatible_v
       = __is_layout_compatible(_Tp, _Up);
 
-#if __has_builtin(__builtin_is_corresponding_member)
+#if _GLIBCXX_HAS_BUILTIN_TRAIT(__builtin_is_corresponding_member)
 #define __cpp_lib_is_layout_compatible 201907L
 
   /// @since C++20
@@ -3540,7 +3540,7 @@ template<typename _Ret, typename _Fn, typename... _Args>
 #endif
 #endif
 
-#if __has_builtin(__is_pointer_interconvertible_base_of)
+#if _GLIBCXX_HAS_BUILTIN_TRAIT(__is_pointer_interconvertible_base_of)
   /// True if `_Derived` is standard-layout and has a base class of type `_Base`
   /// @since C++20
   template<typename _Base, typename _Derived>
@@ -3554,7 +3554,7 @@ template<typename _Ret, typename _Fn, typename... _Args>
     constexpr bool is_pointer_interconvertible_base_of_v
       = __is_pointer_interconvertible_base_of(_Base, _Derived);
 
-#if __has_builtin(__builtin_is_pointer_interconvertible_with_class)
+#if _GLIBCXX_HAS_BUILTIN_TRAIT(__builtin_is_pointer_interconvertible_with_class)
 #define __cpp_lib_is_pointer_interconvertible 201907L
 
   /// True if `__mp` points to the first member of a standard-layout type
@@ -3590,8 +3590,8 @@ template<typename _Ret, typename _Fn, typename... _Args>
   template<typename _Tp>
     inline constexpr bool is_scoped_enum_v = is_scoped_enum<_Tp>::value;
 
-#if __has_builtin(__reference_constructs_from_temporary) \
-  && __has_builtin(__reference_converts_from_temporary)
+#if _GLIBCXX_HAS_BUILTIN_TRAIT(__reference_constructs_from_temporary) \
+  && _GLIBCXX_HAS_BUILTIN_TRAIT(__reference_converts_from_temporary)
 
 #define __cpp_lib_reference_from_temporary 202202L
 
@@ -3632,7 +3632,7 @@ template<typename _Ret, typename _Fn, typename... _Args>
   template<typename _Tp, typename _Up>
     inline constexpr bool reference_converts_from_temporary_v
       = reference_converts_from_temporary<_Tp, _Up>::value;
-#endif // __has_builtin for reference_from_temporary
+#endif // _GLIBCXX_HAS_BUILTIN_TRAIT for reference_from_temporary
 #endif // C++23
 
 #if _GLIBCXX_HAVE_IS_CONSTANT_EVALUATED
-- 
2.41.0

Re: [PATCH v3 2/2] libstdc++: Use _GLIBCXX_HAS_BUILTIN_TRAIT

[Patrick Palka]

On Thu, 27 Jul 2023, Ken Matsui via Gcc-patches wrote:

> This patch uses _GLIBCXX_HAS_BUILTIN_TRAIT macro instead of
> __has_builtin in the type_traits header. This macro supports to toggle
> the use of built-in traits in the type_traits header through
> _GLIBCXX_NO_BUILTIN_TRAITS macro, without needing to modify the
> source code.
> 
> libstdc++-v3/ChangeLog:
> 
> 	* include/std/type_traits (__has_builtin): Replace with ...
> 	(_GLIBCXX_HAS_BUILTIN): ... this.
> 
> Signed-off-by: Ken Matsui <kmatsui@gcc.gnu.org>
> ---
>  libstdc++-v3/include/std/type_traits | 26 +++++++++++++-------------
>  1 file changed, 13 insertions(+), 13 deletions(-)
> 
> diff --git a/libstdc++-v3/include/std/type_traits b/libstdc++-v3/include/std/type_traits
> index 9f086992ebc..12423361b6e 100644
> --- a/libstdc++-v3/include/std/type_traits
> +++ b/libstdc++-v3/include/std/type_traits
> @@ -1411,7 +1411,7 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
>      : public __bool_constant<__is_base_of(_Base, _Derived)>
>      { };
>  
> -#if __has_builtin(__is_convertible)
> +#if _GLIBCXX_HAS_BUILTIN_TRAIT(__is_convertible)
>    template<typename _From, typename _To>
>      struct is_convertible
>      : public __bool_constant<__is_convertible(_From, _To)>
> @@ -1462,7 +1462,7 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
>  #if __cplusplus >= 202002L
>  #define __cpp_lib_is_nothrow_convertible 201806L
>  
> -#if __has_builtin(__is_nothrow_convertible)
> +#if _GLIBCXX_HAS_BUILTIN_TRAIT(__is_nothrow_convertible)
>    /// is_nothrow_convertible_v
>    template<typename _From, typename _To>
>      inline constexpr bool is_nothrow_convertible_v
> @@ -1537,7 +1537,7 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
>      { using type = _Tp; };
>  
>    /// remove_cv
> -#if __has_builtin(__remove_cv)
> +#if _GLIBCXX_HAS_BUILTIN_TRAIT(__remove_cv)
>    template<typename _Tp>
>      struct remove_cv
>      { using type = __remove_cv(_Tp); };
> @@ -1606,7 +1606,7 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
>    // Reference transformations.
>  
>    /// remove_reference
> -#if __has_builtin(__remove_reference)
> +#if _GLIBCXX_HAS_BUILTIN_TRAIT(__remove_reference)
>    template<typename _Tp>
>      struct remove_reference
>      { using type = __remove_reference(_Tp); };
> @@ -2963,7 +2963,7 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
>        template<typename _Tp,
>  	       bool _Nothrow = noexcept(_S_conv<_Tp>(_S_get())),
>  	       typename = decltype(_S_conv<_Tp>(_S_get())),
> -#if __has_builtin(__reference_converts_from_temporary)
> +#if _GLIBCXX_HAS_BUILTIN_TRAIT(__reference_converts_from_temporary)
>  	       bool _Dangle = __reference_converts_from_temporary(_Tp, _Res_t)
>  #else
>  	       bool _Dangle = false
> @@ -3420,7 +3420,7 @@ template<typename _Ret, typename _Fn, typename... _Args>
>     */
>  #define __cpp_lib_remove_cvref 201711L
>  
> -#if __has_builtin(__remove_cvref)
> +#if _GLIBCXX_HAS_BUILTIN_TRAIT(__remove_cvref)
>    template<typename _Tp>
>      struct remove_cvref
>      { using type = __remove_cvref(_Tp); };
> @@ -3515,7 +3515,7 @@ template<typename _Ret, typename _Fn, typename... _Args>
>      : public bool_constant<is_unbounded_array_v<_Tp>>
>      { };
>  
> -#if __has_builtin(__is_layout_compatible)
> +#if _GLIBCXX_HAS_BUILTIN_TRAIT(__is_layout_compatible)

Hmm, I was thinking we'd use this macro only for traits that have a
fallback non-built-in implementation so that we could easily use/test
their fallback implementation.  For traits that don't have such a
fallback, using this macro would mean that trait would no longer get
defined at all, which doesn't seem as useful.  Perhaps let's initially
adjust only the traits that have a fallback implementation?

We could then verify that using the fallback implementation for all such
traits works as expected by running the testsuite with:

  make check RUNTESTFLAGS="conformance.exp --target_board=unix/-D_GLIBCXX_NO_BUILTIN_TRAITS"

>  
>    /// @since C++20
>    template<typename _Tp, typename _Up>
> @@ -3529,7 +3529,7 @@ template<typename _Ret, typename _Fn, typename... _Args>
>      constexpr bool is_layout_compatible_v
>        = __is_layout_compatible(_Tp, _Up);
>  
> -#if __has_builtin(__builtin_is_corresponding_member)
> +#if _GLIBCXX_HAS_BUILTIN_TRAIT(__builtin_is_corresponding_member)
>  #define __cpp_lib_is_layout_compatible 201907L
>  
>    /// @since C++20
> @@ -3540,7 +3540,7 @@ template<typename _Ret, typename _Fn, typename... _Args>
>  #endif
>  #endif
>  
> -#if __has_builtin(__is_pointer_interconvertible_base_of)
> +#if _GLIBCXX_HAS_BUILTIN_TRAIT(__is_pointer_interconvertible_base_of)
>    /// True if `_Derived` is standard-layout and has a base class of type `_Base`
>    /// @since C++20
>    template<typename _Base, typename _Derived>
> @@ -3554,7 +3554,7 @@ template<typename _Ret, typename _Fn, typename... _Args>
>      constexpr bool is_pointer_interconvertible_base_of_v
>        = __is_pointer_interconvertible_base_of(_Base, _Derived);
>  
> -#if __has_builtin(__builtin_is_pointer_interconvertible_with_class)
> +#if _GLIBCXX_HAS_BUILTIN_TRAIT(__builtin_is_pointer_interconvertible_with_class)
>  #define __cpp_lib_is_pointer_interconvertible 201907L
>  
>    /// True if `__mp` points to the first member of a standard-layout type
> @@ -3590,8 +3590,8 @@ template<typename _Ret, typename _Fn, typename... _Args>
>    template<typename _Tp>
>      inline constexpr bool is_scoped_enum_v = is_scoped_enum<_Tp>::value;
>  
> -#if __has_builtin(__reference_constructs_from_temporary) \
> -  && __has_builtin(__reference_converts_from_temporary)
> +#if _GLIBCXX_HAS_BUILTIN_TRAIT(__reference_constructs_from_temporary) \
> +  && _GLIBCXX_HAS_BUILTIN_TRAIT(__reference_converts_from_temporary)
>  
>  #define __cpp_lib_reference_from_temporary 202202L
>  
> @@ -3632,7 +3632,7 @@ template<typename _Ret, typename _Fn, typename... _Args>
>    template<typename _Tp, typename _Up>
>      inline constexpr bool reference_converts_from_temporary_v
>        = reference_converts_from_temporary<_Tp, _Up>::value;
> -#endif // __has_builtin for reference_from_temporary
> +#endif // _GLIBCXX_HAS_BUILTIN_TRAIT for reference_from_temporary
>  #endif // C++23
>  
>  #if _GLIBCXX_HAVE_IS_CONSTANT_EVALUATED
> -- 
> 2.41.0
> 
> 

Re: [PATCH] libstdc++: Define _GLIBCXX_HAS_BUILTIN_TRAIT

[Jonathan Wakely]

[-- Attachment #1: Type: text/plain, Size: 2150 bytes --]

On Wed, 19 Jul 2023 at 19:48, Patrick Palka via Libstdc++ <
libstdc++@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 <kmatsui@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
> >
> >
>
>

Re: [PATCH v2] libstdc++: Define _GLIBCXX_HAS_BUILTIN_TRAIT

[Jonathan Wakely]

[-- Attachment #1: Type: text/plain, Size: 1734 bytes --]

On Wed, 19 Jul 2023 at 20:33, Ken Matsui via Libstdc++ <
libstdc++@gcc.gnu.org> wrote:

> This patch defines _GLIBCXX_HAS_BUILTIN_TRAIT macro, which will be used
> as a flag to toggle the use of built-in traits in the type_traits header
> through _GLIBCXX_NO_BUILTIN_TRAITS macro, without needing to modify the
> source code.
>
> libstdc++-v3/ChangeLog:
>
>         * include/bits/c++config (_GLIBCXX_HAS_BUILTIN_TRAIT): Define.
>         (_GLIBCXX_HAS_BUILTIN): Keep defined.
>

I think this would be a little better as:

        * include/bits/c++config (_GLIBCXX_HAS_BUILTIN): Do not undef.
        (_GLIBCXX_HAS_BUILTIN_TRAIT): Define.

OK for trunk with that change, thanks.




>
> Signed-off-by: Ken Matsui <kmatsui@gcc.gnu.org>
> ---
>  libstdc++-v3/include/bits/c++config | 10 +++++++++-
>  1 file changed, 9 insertions(+), 1 deletion(-)
>
> diff --git a/libstdc++-v3/include/bits/c++config
> b/libstdc++-v3/include/bits/c++config
> index dd47f274d5f..984985d6fff 100644
> --- a/libstdc++-v3/include/bits/c++config
> +++ b/libstdc++-v3/include/bits/c++config
> @@ -854,7 +854,15 @@ namespace __gnu_cxx
>  # define _GLIBCXX_HAVE_BUILTIN_LAUNDER 1
>  #endif
>
> -#undef _GLIBCXX_HAS_BUILTIN
> +// Returns 1 if _GLIBCXX_NO_BUILTIN_TRAITS is not defined and the compiler
> +// has a corresponding built-in type trait, 0 otherwise.
> +// _GLIBCXX_NO_BUILTIN_TRAITS can be defined to disable the use of
> built-in
> +// traits.
> +#ifndef _GLIBCXX_NO_BUILTIN_TRAITS
> +# define _GLIBCXX_HAS_BUILTIN_TRAIT(BT) _GLIBCXX_HAS_BUILTIN(BT)
> +#else
> +# define _GLIBCXX_HAS_BUILTIN_TRAIT(BT) 0
> +#endif
>
>  // Mark code that should be ignored by the compiler, but seen by Doxygen.
>  #define _GLIBCXX_DOXYGEN_ONLY(X)
> --
> 2.41.0
>
>

Re: [PATCH v2] libstdc++: Define _GLIBCXX_HAS_BUILTIN_TRAIT

[Ken Matsui]

On Tue, Aug 8, 2023 at 1:23 PM Jonathan Wakely <jwakely@redhat.com> wrote:
>
>
>
> On Wed, 19 Jul 2023 at 20:33, Ken Matsui via Libstdc++ <libstdc++@gcc.gnu.org> wrote:
>>
>> This patch defines _GLIBCXX_HAS_BUILTIN_TRAIT macro, which will be used
>> as a flag to toggle the use of built-in traits in the type_traits header
>> through _GLIBCXX_NO_BUILTIN_TRAITS macro, without needing to modify the
>> source code.
>>
>> libstdc++-v3/ChangeLog:
>>
>>         * include/bits/c++config (_GLIBCXX_HAS_BUILTIN_TRAIT): Define.
>>         (_GLIBCXX_HAS_BUILTIN): Keep defined.
>
>
> I think this would be a little better as:
>
>         * include/bits/c++config (_GLIBCXX_HAS_BUILTIN): Do not undef.
>         (_GLIBCXX_HAS_BUILTIN_TRAIT): Define.
>
> OK for trunk with that change, thanks.
>
Thank you for your review! Patrick and I were discussing the naming
conventions for the macros _GLIBCXX_HAS_BUILTIN_TRAIT and
_GLIBCXX_NO_BUILTIN_TRAITS. It was brought to our attention that these
namings might be ambiguous, as there are implementations that have
corresponding built-ins but do not have fallback. Therefore, we
believe that using _GLIBCXX_USE_BUILTIN_TRAIT instead of
_GLIBCXX_HAS_BUILTIN_TRAIT would be more appropriate. Similarly, we
think that _GLIBCXX_AVOID_BUILTIN_TRAITS would be a better choice than
_GLIBCXX_NO_BUILTIN_TRAITS, as the latter implies that there are no
built-ins, when in fact it is meant to express that the use of
built-ins should be avoided when defining this macro. Could you please
let me know your thoughts on these updated namings?
>
>>
>>
>> Signed-off-by: Ken Matsui <kmatsui@gcc.gnu.org>
>> ---
>>  libstdc++-v3/include/bits/c++config | 10 +++++++++-
>>  1 file changed, 9 insertions(+), 1 deletion(-)
>>
>> diff --git a/libstdc++-v3/include/bits/c++config b/libstdc++-v3/include/bits/c++config
>> index dd47f274d5f..984985d6fff 100644
>> --- a/libstdc++-v3/include/bits/c++config
>> +++ b/libstdc++-v3/include/bits/c++config
>> @@ -854,7 +854,15 @@ namespace __gnu_cxx
>>  # define _GLIBCXX_HAVE_BUILTIN_LAUNDER 1
>>  #endif
>>
>> -#undef _GLIBCXX_HAS_BUILTIN
>> +// Returns 1 if _GLIBCXX_NO_BUILTIN_TRAITS is not defined and the compiler
>> +// has a corresponding built-in type trait, 0 otherwise.
>> +// _GLIBCXX_NO_BUILTIN_TRAITS can be defined to disable the use of built-in
>> +// traits.
>> +#ifndef _GLIBCXX_NO_BUILTIN_TRAITS
>> +# define _GLIBCXX_HAS_BUILTIN_TRAIT(BT) _GLIBCXX_HAS_BUILTIN(BT)
>> +#else
>> +# define _GLIBCXX_HAS_BUILTIN_TRAIT(BT) 0
>> +#endif
>>
>>  // Mark code that should be ignored by the compiler, but seen by Doxygen.
>>  #define _GLIBCXX_DOXYGEN_ONLY(X)
>> --
>> 2.41.0
>>

Re: [PATCH v2] libstdc++: Define _GLIBCXX_HAS_BUILTIN_TRAIT

[Jonathan Wakely]

On Thu, 31 Aug 2023 at 13:33, Ken Matsui <kmatsui@cs.washington.edu> wrote:
>
> On Tue, Aug 8, 2023 at 1:23 PM Jonathan Wakely <jwakely@redhat.com> wrote:
> >
> >
> >
> > On Wed, 19 Jul 2023 at 20:33, Ken Matsui via Libstdc++ <libstdc++@gcc.gnu.org> wrote:
> >>
> >> This patch defines _GLIBCXX_HAS_BUILTIN_TRAIT macro, which will be used
> >> as a flag to toggle the use of built-in traits in the type_traits header
> >> through _GLIBCXX_NO_BUILTIN_TRAITS macro, without needing to modify the
> >> source code.
> >>
> >> libstdc++-v3/ChangeLog:
> >>
> >>         * include/bits/c++config (_GLIBCXX_HAS_BUILTIN_TRAIT): Define.
> >>         (_GLIBCXX_HAS_BUILTIN): Keep defined.
> >
> >
> > I think this would be a little better as:
> >
> >         * include/bits/c++config (_GLIBCXX_HAS_BUILTIN): Do not undef.
> >         (_GLIBCXX_HAS_BUILTIN_TRAIT): Define.
> >
> > OK for trunk with that change, thanks.
> >
> Thank you for your review! Patrick and I were discussing the naming
> conventions for the macros _GLIBCXX_HAS_BUILTIN_TRAIT and
> _GLIBCXX_NO_BUILTIN_TRAITS. It was brought to our attention that these
> namings might be ambiguous, as there are implementations that have
> corresponding built-ins but do not have fallback. Therefore, we
> believe that using _GLIBCXX_USE_BUILTIN_TRAIT instead of
> _GLIBCXX_HAS_BUILTIN_TRAIT would be more appropriate. Similarly, we
> think that _GLIBCXX_AVOID_BUILTIN_TRAITS would be a better choice than
> _GLIBCXX_NO_BUILTIN_TRAITS, as the latter implies that there are no
> built-ins, when in fact it is meant to express that the use of
> built-ins should be avoided when defining this macro. Could you please
> let me know your thoughts on these updated namings?

Yes, I agree that makes sense. I think personally I'd go with
"DISABLE" instead of "AVOID", or even "DO_NOT_USE" (to mirror "USE" in
the macro for individual traits), but either is OK.

> >
> >>
> >>
> >> Signed-off-by: Ken Matsui <kmatsui@gcc.gnu.org>
> >> ---
> >>  libstdc++-v3/include/bits/c++config | 10 +++++++++-
> >>  1 file changed, 9 insertions(+), 1 deletion(-)
> >>
> >> diff --git a/libstdc++-v3/include/bits/c++config b/libstdc++-v3/include/bits/c++config
> >> index dd47f274d5f..984985d6fff 100644
> >> --- a/libstdc++-v3/include/bits/c++config
> >> +++ b/libstdc++-v3/include/bits/c++config
> >> @@ -854,7 +854,15 @@ namespace __gnu_cxx
> >>  # define _GLIBCXX_HAVE_BUILTIN_LAUNDER 1
> >>  #endif
> >>
> >> -#undef _GLIBCXX_HAS_BUILTIN
> >> +// Returns 1 if _GLIBCXX_NO_BUILTIN_TRAITS is not defined and the compiler
> >> +// has a corresponding built-in type trait, 0 otherwise.
> >> +// _GLIBCXX_NO_BUILTIN_TRAITS can be defined to disable the use of built-in
> >> +// traits.
> >> +#ifndef _GLIBCXX_NO_BUILTIN_TRAITS
> >> +# define _GLIBCXX_HAS_BUILTIN_TRAIT(BT) _GLIBCXX_HAS_BUILTIN(BT)
> >> +#else
> >> +# define _GLIBCXX_HAS_BUILTIN_TRAIT(BT) 0
> >> +#endif
> >>
> >>  // Mark code that should be ignored by the compiler, but seen by Doxygen.
> >>  #define _GLIBCXX_DOXYGEN_ONLY(X)
> >> --
> >> 2.41.0
> >>
>

Re: [PATCH v2] libstdc++: Define _GLIBCXX_HAS_BUILTIN_TRAIT

[Ken Matsui]

On Mon, Sep 11, 2023 at 7:51 AM Jonathan Wakely <jwakely@redhat.com> wrote:
>
> On Thu, 31 Aug 2023 at 13:33, Ken Matsui <kmatsui@cs.washington.edu> wrote:
> >
> > On Tue, Aug 8, 2023 at 1:23 PM Jonathan Wakely <jwakely@redhat.com> wrote:
> > >
> > >
> > >
> > > On Wed, 19 Jul 2023 at 20:33, Ken Matsui via Libstdc++ <libstdc++@gcc.gnu.org> wrote:
> > >>
> > >> This patch defines _GLIBCXX_HAS_BUILTIN_TRAIT macro, which will be used
> > >> as a flag to toggle the use of built-in traits in the type_traits header
> > >> through _GLIBCXX_NO_BUILTIN_TRAITS macro, without needing to modify the
> > >> source code.
> > >>
> > >> libstdc++-v3/ChangeLog:
> > >>
> > >>         * include/bits/c++config (_GLIBCXX_HAS_BUILTIN_TRAIT): Define.
> > >>         (_GLIBCXX_HAS_BUILTIN): Keep defined.
> > >
> > >
> > > I think this would be a little better as:
> > >
> > >         * include/bits/c++config (_GLIBCXX_HAS_BUILTIN): Do not undef.
> > >         (_GLIBCXX_HAS_BUILTIN_TRAIT): Define.
> > >
> > > OK for trunk with that change, thanks.
> > >
> > Thank you for your review! Patrick and I were discussing the naming
> > conventions for the macros _GLIBCXX_HAS_BUILTIN_TRAIT and
> > _GLIBCXX_NO_BUILTIN_TRAITS. It was brought to our attention that these
> > namings might be ambiguous, as there are implementations that have
> > corresponding built-ins but do not have fallback. Therefore, we
> > believe that using _GLIBCXX_USE_BUILTIN_TRAIT instead of
> > _GLIBCXX_HAS_BUILTIN_TRAIT would be more appropriate. Similarly, we
> > think that _GLIBCXX_AVOID_BUILTIN_TRAITS would be a better choice than
> > _GLIBCXX_NO_BUILTIN_TRAITS, as the latter implies that there are no
> > built-ins, when in fact it is meant to express that the use of
> > built-ins should be avoided when defining this macro. Could you please
> > let me know your thoughts on these updated namings?
>
> Yes, I agree that makes sense. I think personally I'd go with
> "DISABLE" instead of "AVOID", or even "DO_NOT_USE" (to mirror "USE" in
> the macro for individual traits), but either is OK.

I like the idea of mirroring "USE", so I would choose "DO_NOT_USE".
Thank you for your response!

> > >
> > >>
> > >>
> > >> Signed-off-by: Ken Matsui <kmatsui@gcc.gnu.org>
> > >> ---
> > >>  libstdc++-v3/include/bits/c++config | 10 +++++++++-
> > >>  1 file changed, 9 insertions(+), 1 deletion(-)
> > >>
> > >> diff --git a/libstdc++-v3/include/bits/c++config b/libstdc++-v3/include/bits/c++config
> > >> index dd47f274d5f..984985d6fff 100644
> > >> --- a/libstdc++-v3/include/bits/c++config
> > >> +++ b/libstdc++-v3/include/bits/c++config
> > >> @@ -854,7 +854,15 @@ namespace __gnu_cxx
> > >>  # define _GLIBCXX_HAVE_BUILTIN_LAUNDER 1
> > >>  #endif
> > >>
> > >> -#undef _GLIBCXX_HAS_BUILTIN
> > >> +// Returns 1 if _GLIBCXX_NO_BUILTIN_TRAITS is not defined and the compiler
> > >> +// has a corresponding built-in type trait, 0 otherwise.
> > >> +// _GLIBCXX_NO_BUILTIN_TRAITS can be defined to disable the use of built-in
> > >> +// traits.
> > >> +#ifndef _GLIBCXX_NO_BUILTIN_TRAITS
> > >> +# define _GLIBCXX_HAS_BUILTIN_TRAIT(BT) _GLIBCXX_HAS_BUILTIN(BT)
> > >> +#else
> > >> +# define _GLIBCXX_HAS_BUILTIN_TRAIT(BT) 0
> > >> +#endif
> > >>
> > >>  // Mark code that should be ignored by the compiler, but seen by Doxygen.
> > >>  #define _GLIBCXX_DOXYGEN_ONLY(X)
> > >> --
> > >> 2.41.0
> > >>
> >
>