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From: "redi at gcc dot gnu.org" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug libstdc++/99117] [11/12/13/14 Regression] cannot accumulate
 std::valarray
Date: Thu, 08 Feb 2024 21:34:47 +0000
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https://gcc.gnu.org/bugzilla/show_bug.cgi?id=3D99117

--- Comment #22 from Jonathan Wakely <redi at gcc dot gnu.org> ---
Instead of adding yet another __valarray_copy overload, we can just not use=
 it:

--- a/libstdc++-v3/include/std/valarray
+++ b/libstdc++-v3/include/std/valarray
@@ -840,7 +840,13 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
       // _GLIBCXX_RESOLVE_LIB_DEFECTS
       // 630. arrays of valarray.
       if (_M_size =3D=3D __e.size())
-       std::__valarray_copy(__e, _M_size, _Array<_Tp>(_M_data));
+       {
+         // Copy manually instead of using __valarray_copy, because __e mi=
ght
+         // alias _M_data and the _Array param type of __valarray_copy uses
+         // restrict which doesn't allow aliasing.
+         for (size_t __i =3D 0; __i < _M_size; ++__i)
+           _M_data[__i] =3D __e[__i];
+       }
       else
        {
          if (_M_data)


That would actually allow us to remove that __valarray_copy overload, becau=
se
this is the only caller.=