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From: "cuzdav at gmail dot com" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug tree-optimization/80635] [8/9/10/11 regression] std::optional
 and bogus -Wmaybe-uninitialized warning
Date: Thu, 15 Oct 2020 18:02:31 +0000
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https://gcc.gnu.org/bugzilla/show_bug.cgi?id=3D80635

Chris Uzdavinis <cuzdav at gmail dot com> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |cuzdav at gmail dot com

--- Comment #54 from Chris Uzdavinis <cuzdav at gmail dot com> ---
I'm not sure if this is the same bug or a different one, but it's in the sa=
me
family (I think).  Visible in current trunk, 10.2 release, and as far back =
as
8.1.

I found optimize level -Os is necessary=20

https://godbolt.org/z/Ta55jM


#include <optional>
using Opt =3D std::optional<int>;

Opt f(int x) {=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20
    Opt ret;=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20
    Opt val =3D (x =3D=3D 1) ? 999 : (x =3D=3D 2) ? Opt(2) : std::nullopt;
    if (val.has_value())
        ret =3D val.value();
    return ret;
}


<source>: In function 'Opt f(int)':
<source>:9:12: error: 'val.std::_Optional_payload_base<int>::_Storage<int,
true>::_M_value' may be used uninitialized in this function
[-Werror=3Dmaybe-uninitialized]

    9 |     return ret;

      |            ^~~=