[gcc r15-1550] libstdc++: Don't use std::__is_scalar in std::valarray initialization [PR115497]

[Jonathan Wakely]

https://gcc.gnu.org/g:139d65d1f5a60ac90479653a4f9b63618509f3f9

commit r15-1550-g139d65d1f5a60ac90479653a4f9b63618509f3f9
Author: Jonathan Wakely <jwakely@redhat.com>
Date:   Wed Jun 19 11:19:58 2024 +0100

    libstdc++: Don't use std::__is_scalar in std::valarray initialization [PR115497]
    
    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>.

Diff:
---
 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