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From: "pinskia at gcc dot gnu.org" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug c++/96538] Integer overflow when there are multiple operands in
 addition operation.
Date: Sat, 08 Aug 2020 22:51:31 +0000
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https://gcc.gnu.org/bugzilla/show_bug.cgi?id=3D96538

Andrew Pinski <pinskia at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|UNCONFIRMED                 |RESOLVED
         Resolution|---                         |INVALID

--- Comment #2 from Andrew Pinski <pinskia at gcc dot gnu.org> ---
There is NO BUG here:
sum =3D arr[1]+arr[2]+arr[3];

Is done in integer type and then casted to long.
that is it is the same as:
sum =3D (long)(arr[1]+arr[2]+arr[3]);

While:
for(int j=3D0;j<5;j++)
{
sum =3D sum+ arr[j];
}
Is Done in long type.

You can fix the original code by doing:
sum =3D ((long)arr[1])+((long)arr[2])+((long)arr[3]);=