[PATCH 1/4] libstdc++: Don't use std::__is_scalar in std::valarray initialization [PR115497]

[PATCH 1/4] libstdc++: Don't use std::__is_scalar in std::valarray initialization [PR115497]

[Jonathan Wakely]

We know that valarray's value_type must be DefaultConstructible, so we
don't need to test that. I think __is_trivial is sufficient to tell us
we can use memset to value-initialize the elements.

Tested x86_64-linux.

-- >8 --

This removes the use of the std::__is_scalar trait from <valarray>,
where it can be replaced by __is_trivial. It's used to decide whether we
can use memset to value-initialize valarray elements, but memset is
suitable for any trivial types, because value-initializing them is
equivalent to filling them with zeros.

This is another step towards removing the class templates in
<bits/cpp_type_traits.h> that conflict with Clang built-in names.

libstdc++-v3/ChangeLog:

	PR libstdc++/115497
	* include/bits/valarray_array.h (__valarray_default_construct):
	Use __is_trivial(_Tp). instead of __is_scalar<_Tp>.
---
 libstdc++-v3/include/bits/valarray_array.h | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/libstdc++-v3/include/bits/valarray_array.h b/libstdc++-v3/include/bits/valarray_array.h
index 66b74f9aaac..07c49ce1057 100644
--- a/libstdc++-v3/include/bits/valarray_array.h
+++ b/libstdc++-v3/include/bits/valarray_array.h
@@ -80,7 +80,7 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
   template<typename _Tp>
     struct _Array_default_ctor<_Tp, true>
     {
-      // For fundamental types, it suffices to say 'memset()'
+      // For trivial types, it suffices to say 'memset()'
       inline static void
       _S_do_it(_Tp* __b, _Tp* __e)
       { __builtin_memset(__b, 0, (__e - __b) * sizeof(_Tp)); }
@@ -90,7 +90,7 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
     inline void
     __valarray_default_construct(_Tp* __b, _Tp* __e)
     {
-      _Array_default_ctor<_Tp, __is_scalar<_Tp>::__value>::_S_do_it(__b, __e);
+      _Array_default_ctor<_Tp, __is_trivial(_Tp)>::_S_do_it(__b, __e);
     }
 
   // Turn a raw-memory into an array of _Tp filled with __t
-- 
2.45.2

[PATCH 2/4] libstdc++: Stop using std::__is_pointer in <deque> and <algorithm> [PR115497]

[Jonathan Wakely]

Tested x86_64-linux.

-- >8 --

This replaces all uses of the std::__is_pointer type trait with uses of
the new __is_pointer built-in. Since the class template was only used to
enable some performance optimizations for algorithms, we can use the
built-in when __has_builtin(__is_pointer) is true (which is the case for
GCC trunk and for current versions of Clang) and just forego the
optimization otherwise.

Removing the uses of std::__is_pointer means it can be removed from
<bits/cpp_type_traits.h>, which is another step towards fixing PR
115497.

libstdc++-v3/ChangeLog:

	PR libstdc++/115497
	* include/bits/deque.tcc (__lex_cmp_dit): Replace __is_pointer
	class template with __is_pointer(T) built-in.
	(__lexicographical_compare_aux1): Likewise.
	* include/bits/stl_algobase.h (__equal_aux1): Likewise.
	(__lexicographical_compare_aux1): Likewise.
---
 libstdc++-v3/include/bits/deque.tcc      | 19 ++++++++++++-------
 libstdc++-v3/include/bits/stl_algobase.h | 13 +++++++++----
 2 files changed, 21 insertions(+), 11 deletions(-)

diff --git a/libstdc++-v3/include/bits/deque.tcc b/libstdc++-v3/include/bits/deque.tcc
index 2c12358ca5b..deb010a0ebb 100644
--- a/libstdc++-v3/include/bits/deque.tcc
+++ b/libstdc++-v3/include/bits/deque.tcc
@@ -1271,18 +1271,21 @@ _GLIBCXX_END_NAMESPACE_CONTAINER
 	_GLIBCXX_STD_C::_Deque_iterator<_Tp1, _Ref, _Ptr> __last1,
 	const _Tp2* __first2, const _Tp2* __last2)
     {
+#if _GLIBCXX_USE_BUILTIN_TRAIT(__is_pointer)
       const bool __simple =
 	(__is_memcmp_ordered_with<_Tp1, _Tp2>::__value
-	 && __is_pointer<_Ptr>::__value
+	 && __is_pointer(_Ptr)
 #if __cplusplus > 201703L && __cpp_lib_concepts
 	 // For C++20 iterator_traits<volatile T*>::value_type is non-volatile
 	 // so __is_byte<T> could be true, but we can't use memcmp with
 	 // volatile data.
-	 && !is_volatile_v<_Tp1>
-	 && !is_volatile_v<_Tp2>
+	 && !is_volatile_v<_Tp1> && !is_volatile_v<_Tp2>
 #endif
 	 );
       typedef std::__lexicographical_compare<__simple> _Lc;
+#else
+      typedef std::__lexicographical_compare<false> _Lc;
+#endif
 
       while (__first1._M_node != __last1._M_node)
 	{
@@ -1327,19 +1330,21 @@ _GLIBCXX_END_NAMESPACE_CONTAINER
 		_GLIBCXX_STD_C::_Deque_iterator<_Tp2, _Ref2, _Ptr2> __first2,
 		_GLIBCXX_STD_C::_Deque_iterator<_Tp2, _Ref2, _Ptr2> __last2)
     {
+#if _GLIBCXX_USE_BUILTIN_TRAIT(__is_pointer)
       const bool __simple =
 	(__is_memcmp_ordered_with<_Tp1, _Tp2>::__value
-	 && __is_pointer<_Ptr1>::__value
-	 && __is_pointer<_Ptr2>::__value
+	 && __is_pointer(_Ptr1) && __is_pointer(_Ptr2)
 #if __cplusplus > 201703L && __cpp_lib_concepts
 	 // For C++20 iterator_traits<volatile T*>::value_type is non-volatile
 	 // so __is_byte<T> could be true, but we can't use memcmp with
 	 // volatile data.
-	 && !is_volatile_v<_Tp1>
-	 && !is_volatile_v<_Tp2>
+	 && !is_volatile_v<_Tp1> && !is_volatile_v<_Tp2>
 #endif
 	 );
       typedef std::__lexicographical_compare<__simple> _Lc;
+#else
+      typedef std::__lexicographical_compare<false> _Lc;
+#endif
 
       while (__first1 != __last1)
 	{
diff --git a/libstdc++-v3/include/bits/stl_algobase.h b/libstdc++-v3/include/bits/stl_algobase.h
index 1a0f8c14073..57ff2f7cb08 100644
--- a/libstdc++-v3/include/bits/stl_algobase.h
+++ b/libstdc++-v3/include/bits/stl_algobase.h
@@ -1256,8 +1256,10 @@ _GLIBCXX_END_NAMESPACE_CONTAINER
     {
       typedef typename iterator_traits<_II1>::value_type _ValueType1;
       const bool __simple = ((__is_integer<_ValueType1>::__value
-			      || __is_pointer<_ValueType1>::__value)
-			     && __memcmpable<_II1, _II2>::__value);
+#if _GLIBCXX_USE_BUILTIN_TRAIT(__is_pointer)
+			      || __is_pointer(_ValueType1)
+#endif
+			     ) && __memcmpable<_II1, _II2>::__value);
       return std::__equal<__simple>::equal(__first1, __last1, __first2);
     }
 
@@ -1420,10 +1422,10 @@ _GLIBCXX_END_NAMESPACE_CONTAINER
     {
       typedef typename iterator_traits<_II1>::value_type _ValueType1;
       typedef typename iterator_traits<_II2>::value_type _ValueType2;
+#if _GLIBCXX_USE_BUILTIN_TRAIT(__is_pointer)
       const bool __simple =
 	(__is_memcmp_ordered_with<_ValueType1, _ValueType2>::__value
-	 && __is_pointer<_II1>::__value
-	 && __is_pointer<_II2>::__value
+	 && __is_pointer(_II1) && __is_pointer(_II2)
 #if __cplusplus > 201703L && __glibcxx_concepts
 	 // For C++20 iterator_traits<volatile T*>::value_type is non-volatile
 	 // so __is_byte<T> could be true, but we can't use memcmp with
@@ -1432,6 +1434,9 @@ _GLIBCXX_END_NAMESPACE_CONTAINER
 	 && !is_volatile_v<remove_reference_t<iter_reference_t<_II2>>>
 #endif
 	 );
+#else
+      const bool __simple = false;
+#endif
 
       return std::__lexicographical_compare<__simple>::__lc(__first1, __last1,
 							    __first2, __last2);
-- 
2.45.2

[PATCH 3/4] libstdc++: Remove std::__is_void class template [PR115497]

[Jonathan Wakely]

Tested x86_64-linux.

-- >8 --

This removes the std::__is_void trait, as it conflicts with a Clang
built-in. There is only one use of the trait, which can easily be
replaced by simpler code.

Although Clang has a hack to make the class template work despite using
a reserved name, removing std::__is_void will allow that hack to be
dropped at some future date.

libstdc++-v3/ChangeLog:

	PR libstdc++/115497
	* include/bits/cpp_type_traits.h (__is_void): Remove.
	* include/debug/helper_functions.h (_Distance_traits):
	Adjust partial specialization to match void directly, instead of
	using __is_void<T>::__type and matching __true_type.
---
 libstdc++-v3/include/bits/cpp_type_traits.h   | 15 ---------------
 libstdc++-v3/include/debug/helper_functions.h |  5 ++---
 2 files changed, 2 insertions(+), 18 deletions(-)

diff --git a/libstdc++-v3/include/bits/cpp_type_traits.h b/libstdc++-v3/include/bits/cpp_type_traits.h
index 6834dee5557..4d83b9472e6 100644
--- a/libstdc++-v3/include/bits/cpp_type_traits.h
+++ b/libstdc++-v3/include/bits/cpp_type_traits.h
@@ -105,21 +105,6 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
       typedef __true_type __type;
     };
 
-  // Holds if the template-argument is a void type.
-  template<typename _Tp>
-    struct __is_void
-    {
-      enum { __value = 0 };
-      typedef __false_type __type;
-    };
-
-  template<>
-    struct __is_void<void>
-    {
-      enum { __value = 1 };
-      typedef __true_type __type;
-    };
-
   //
   // Integer types
   //
diff --git a/libstdc++-v3/include/debug/helper_functions.h b/libstdc++-v3/include/debug/helper_functions.h
index 5474399dc67..d686a29e8ee 100644
--- a/libstdc++-v3/include/debug/helper_functions.h
+++ b/libstdc++-v3/include/debug/helper_functions.h
@@ -66,13 +66,12 @@ namespace __gnu_debug
       typedef
 	typename std::iterator_traits<_Iterator>::difference_type _ItDiffType;
 
-      template<typename _DiffType,
-	       typename = typename std::__is_void<_DiffType>::__type>
+      template<typename _DiffType, typename = _DiffType> // PR c++/85282
 	struct _DiffTraits
 	{ typedef _DiffType __type; };
 
       template<typename _DiffType>
-	struct _DiffTraits<_DiffType, std::__true_type>
+	struct _DiffTraits<_DiffType, void>
 	{ typedef std::ptrdiff_t __type; };
 
       typedef typename _DiffTraits<_ItDiffType>::__type _DiffType;
-- 
2.45.2

[PATCH 4/4] libstdc++: Remove std::__is_pointer and std::__is_scalar [PR115497]

[Jonathan Wakely]

We still have __is_arithmetic in <bits/cpp_type_traits.h> after this,
but that needs a lot more work to remove its uses from <cmath> and
<tr1/cmath>.

Tested x86_64-linux.

-- >8 --

This removes the std::__is_pointer and std::__is_scalar traits, as they
conflicts with a Clang built-in.

Although Clang has a hack to make the class templates work despite using
reserved names, removing these class templates will allow that hack to
be dropped at some future date.

libstdc++-v3/ChangeLog:

	PR libstdc++/115497
	* include/bits/cpp_type_traits.h (__is_pointer, __is_scalar):
	Remove.
	(__is_arithmetic): Do not use __is_pointer in the primary
	template. Add partial specialization for pointers.
---
 libstdc++-v3/include/bits/cpp_type_traits.h | 33 ---------------------
 1 file changed, 33 deletions(-)

diff --git a/libstdc++-v3/include/bits/cpp_type_traits.h b/libstdc++-v3/include/bits/cpp_type_traits.h
index 4d83b9472e6..abe0c7603e3 100644
--- a/libstdc++-v3/include/bits/cpp_type_traits.h
+++ b/libstdc++-v3/include/bits/cpp_type_traits.h
@@ -343,31 +343,6 @@ __INT_N(__GLIBCXX_TYPE_INT_N_3)
     };
 #endif
 
-  //
-  // Pointer types
-  //
-#if _GLIBCXX_USE_BUILTIN_TRAIT(__is_pointer)
-  template<typename _Tp, bool _IsPtr = __is_pointer(_Tp)>
-    struct __is_pointer : __truth_type<_IsPtr>
-    {
-      enum { __value = _IsPtr };
-    };
-#else
-  template<typename _Tp>
-    struct __is_pointer
-    {
-      enum { __value = 0 };
-      typedef __false_type __type;
-    };
-
-  template<typename _Tp>
-    struct __is_pointer<_Tp*>
-    {
-      enum { __value = 1 };
-      typedef __true_type __type;
-    };
-#endif
-
   //
   // An arithmetic type is an integer type or a floating point type
   //
@@ -376,14 +351,6 @@ __INT_N(__GLIBCXX_TYPE_INT_N_3)
     : public __traitor<__is_integer<_Tp>, __is_floating<_Tp> >
     { };
 
-  //
-  // A scalar type is an arithmetic type or a pointer type
-  // 
-  template<typename _Tp>
-    struct __is_scalar
-    : public __traitor<__is_arithmetic<_Tp>, __is_pointer<_Tp> >
-    { };
-
   //
   // For use in std::copy and std::find overloads for streambuf iterators.
   //
-- 
2.45.2

Re: [PATCH 4/4] libstdc++: Remove std::__is_pointer and std::__is_scalar [PR115497]

[Jonathan Wakely]

Oops, this patch series actually depends on
https://gcc.gnu.org/pipermail/gcc-patches/2024-June/655267.html which
was posted separately, but needs to be applied before 4/4 in this
series.

On Thu, 20 Jun 2024 at 16:35, Jonathan Wakely <jwakely@redhat.com> wrote:
>
> We still have __is_arithmetic in <bits/cpp_type_traits.h> after this,
> but that needs a lot more work to remove its uses from <cmath> and
> <tr1/cmath>.
>
> Tested x86_64-linux.
>
> -- >8 --
>
> This removes the std::__is_pointer and std::__is_scalar traits, as they
> conflicts with a Clang built-in.
>
> Although Clang has a hack to make the class templates work despite using
> reserved names, removing these class templates will allow that hack to
> be dropped at some future date.
>
> libstdc++-v3/ChangeLog:
>
>         PR libstdc++/115497
>         * include/bits/cpp_type_traits.h (__is_pointer, __is_scalar):
>         Remove.
>         (__is_arithmetic): Do not use __is_pointer in the primary
>         template. Add partial specialization for pointers.
> ---
>  libstdc++-v3/include/bits/cpp_type_traits.h | 33 ---------------------
>  1 file changed, 33 deletions(-)
>
> diff --git a/libstdc++-v3/include/bits/cpp_type_traits.h b/libstdc++-v3/include/bits/cpp_type_traits.h
> index 4d83b9472e6..abe0c7603e3 100644
> --- a/libstdc++-v3/include/bits/cpp_type_traits.h
> +++ b/libstdc++-v3/include/bits/cpp_type_traits.h
> @@ -343,31 +343,6 @@ __INT_N(__GLIBCXX_TYPE_INT_N_3)
>      };
>  #endif
>
> -  //
> -  // Pointer types
> -  //
> -#if _GLIBCXX_USE_BUILTIN_TRAIT(__is_pointer)
> -  template<typename _Tp, bool _IsPtr = __is_pointer(_Tp)>
> -    struct __is_pointer : __truth_type<_IsPtr>
> -    {
> -      enum { __value = _IsPtr };
> -    };
> -#else
> -  template<typename _Tp>
> -    struct __is_pointer
> -    {
> -      enum { __value = 0 };
> -      typedef __false_type __type;
> -    };
> -
> -  template<typename _Tp>
> -    struct __is_pointer<_Tp*>
> -    {
> -      enum { __value = 1 };
> -      typedef __true_type __type;
> -    };
> -#endif
> -
>    //
>    // An arithmetic type is an integer type or a floating point type
>    //
> @@ -376,14 +351,6 @@ __INT_N(__GLIBCXX_TYPE_INT_N_3)
>      : public __traitor<__is_integer<_Tp>, __is_floating<_Tp> >
>      { };
>
> -  //
> -  // A scalar type is an arithmetic type or a pointer type
> -  //
> -  template<typename _Tp>
> -    struct __is_scalar
> -    : public __traitor<__is_arithmetic<_Tp>, __is_pointer<_Tp> >
> -    { };
> -
>    //
>    // For use in std::copy and std::find overloads for streambuf iterators.
>    //
> --
> 2.45.2
>

Re: [PATCH 4/4] libstdc++: Remove std::__is_pointer and std::__is_scalar [PR115497]

[Jonathan Wakely]

This series (and the patch it depends on) have been pushed to trunk now.


On Fri, 21 Jun 2024 at 10:31, Jonathan Wakely <jwakely@redhat.com> wrote:
>
> Oops, this patch series actually depends on
> https://gcc.gnu.org/pipermail/gcc-patches/2024-June/655267.html which
> was posted separately, but needs to be applied before 4/4 in this
> series.
>
> On Thu, 20 Jun 2024 at 16:35, Jonathan Wakely <jwakely@redhat.com> wrote:
> >
> > We still have __is_arithmetic in <bits/cpp_type_traits.h> after this,
> > but that needs a lot more work to remove its uses from <cmath> and
> > <tr1/cmath>.
> >
> > Tested x86_64-linux.
> >
> > -- >8 --
> >
> > This removes the std::__is_pointer and std::__is_scalar traits, as they
> > conflicts with a Clang built-in.
> >
> > Although Clang has a hack to make the class templates work despite using
> > reserved names, removing these class templates will allow that hack to
> > be dropped at some future date.
> >
> > libstdc++-v3/ChangeLog:
> >
> >         PR libstdc++/115497
> >         * include/bits/cpp_type_traits.h (__is_pointer, __is_scalar):
> >         Remove.
> >         (__is_arithmetic): Do not use __is_pointer in the primary
> >         template. Add partial specialization for pointers.
> > ---
> >  libstdc++-v3/include/bits/cpp_type_traits.h | 33 ---------------------
> >  1 file changed, 33 deletions(-)
> >
> > diff --git a/libstdc++-v3/include/bits/cpp_type_traits.h b/libstdc++-v3/include/bits/cpp_type_traits.h
> > index 4d83b9472e6..abe0c7603e3 100644
> > --- a/libstdc++-v3/include/bits/cpp_type_traits.h
> > +++ b/libstdc++-v3/include/bits/cpp_type_traits.h
> > @@ -343,31 +343,6 @@ __INT_N(__GLIBCXX_TYPE_INT_N_3)
> >      };
> >  #endif
> >
> > -  //
> > -  // Pointer types
> > -  //
> > -#if _GLIBCXX_USE_BUILTIN_TRAIT(__is_pointer)
> > -  template<typename _Tp, bool _IsPtr = __is_pointer(_Tp)>
> > -    struct __is_pointer : __truth_type<_IsPtr>
> > -    {
> > -      enum { __value = _IsPtr };
> > -    };
> > -#else
> > -  template<typename _Tp>
> > -    struct __is_pointer
> > -    {
> > -      enum { __value = 0 };
> > -      typedef __false_type __type;
> > -    };
> > -
> > -  template<typename _Tp>
> > -    struct __is_pointer<_Tp*>
> > -    {
> > -      enum { __value = 1 };
> > -      typedef __true_type __type;
> > -    };
> > -#endif
> > -
> >    //
> >    // An arithmetic type is an integer type or a floating point type
> >    //
> > @@ -376,14 +351,6 @@ __INT_N(__GLIBCXX_TYPE_INT_N_3)
> >      : public __traitor<__is_integer<_Tp>, __is_floating<_Tp> >
> >      { };
> >
> > -  //
> > -  // A scalar type is an arithmetic type or a pointer type
> > -  //
> > -  template<typename _Tp>
> > -    struct __is_scalar
> > -    : public __traitor<__is_arithmetic<_Tp>, __is_pointer<_Tp> >
> > -    { };
> > -
> >    //
> >    // For use in std::copy and std::find overloads for streambuf iterators.
> >    //
> > --
> > 2.45.2
> >