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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++/110394] Lambda capture receives wrong value
Date: Sat, 24 Jun 2023 16:15:58 +0000
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https://gcc.gnu.org/bugzilla/show_bug.cgi?id=3D110394

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

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|UNCONFIRMED                 |WAITING
   Last reconfirmed|                            |2023-06-24
     Ever confirmed|0                           |1

--- Comment #2 from Andrew Pinski <pinskia at gcc dot gnu.org> ---
I am almost think this is a bug in your code.
Take:

  auto wait_handle =3D tc::g_postbox->wait(
    "UpdateInputs"sv, [=3D](const msgpack::object& obj) -> bool {
    ....
  });


The temporary for tc::postbox::acceptor_type will end its lifetime at the e=
nd
of that statement but tc::g_postbox->wait stores it off into m_awaiters.

And then gets poped off with:
  wait_handle.await();


You can fix this via extending the temporary via:
```
  tc::postbox::acceptor_type t =3D [=3D](const msgpack::object& obj) -> boo=
l {
    auto [rcv_index, rcv_value] =3D obj.as<std::tuple<int, uint32_t>>();
    tc::tracef(M64MSG_VERBOSE, "index =3D {}", index);
    if (rcv_index !=3D index)
      return false;

    keys->Value =3D rcv_value;
    return true;
  };
  auto wait_handle =3D tc::g_postbox->wait(
    "UpdateInputs"sv, t);

```


Note `-fsantize=3Daddress` should catch this at runtime too.=