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From: "marat at slonopotamus dot org" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug c++/97151] GCC fails to optimize away uselessly allocated
 arrays (C++)
Date: Tue, 22 Sep 2020 07:18:23 +0000
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https://gcc.gnu.org/bugzilla/show_bug.cgi?id=3D97151

--- Comment #4 from Marat Radchenko <marat at slonopotamus dot org> ---
(In reply to Martin Li=C5=A1ka from comment #3)
> It's caused by what was mentioned as 2) which transforms to:
>=20
>   _6 =3D operator new [] (40);
>   __builtin_memset (_6, 0, 40);
>   operator delete [] (_6);
>=20
> So there's a use of _6 and we probably can't remove it as memset can
> potentially access NULL pointer if operator new [] fails.

1. If operator new[] fails, there would be an exception instead of NULL, no?

2. It doesn't matter, you may guard accessing array with NULL check and sti=
ll
observe described behavior.

What puzzles me the most is why removal of delete[] allows it to optimize.=