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From: "yasui at icepp dot s.u-tokyo.ac.jp" <gcc-bugzilla@gcc.gnu.org>
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Subject: [Bug c++/99117] New: cannot accumulate std::valarray
Date: Tue, 16 Feb 2021 05:26:10 +0000
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https://gcc.gnu.org/bugzilla/show_bug.cgi?id=3D99117

            Bug ID: 99117
           Summary: cannot accumulate std::valarray
           Product: gcc
           Version: 10.1.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c++
          Assignee: unassigned at gcc dot gnu.org
          Reporter: yasui at icepp dot s.u-tokyo.ac.jp
  Target Milestone: ---

Created attachment 50193
  --> https://gcc.gnu.org/bugzilla/attachment.cgi?id=3D50193&action=3Dedit
source file

The result of the summation of the std::valarrays by std::accumulate is
improper when compiling with -O2.
It works properly with -O1.

option:
g++ -std=3Dc++2a -Wall -Wextra -O2 source.cpp

In the source file, it calculates (1,1) + (2,2) =3D (3,3).
The expected result is outputting nothing.
If compiling with -O2, following message is shown:
a.out: source.cpp:10: int main(): Assertion `sum[0]=3D=3D3' failed.=