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From: "pdimov at gmail dot com" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug libstdc++/114865] [13/14/15 Regression]
 std::atomic<X>::compare_exchange_strong seems to hang under GCC 13  for C++11
Date: Sat, 27 Apr 2024 00:38:35 +0000
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https://gcc.gnu.org/bugzilla/show_bug.cgi?id=3D114865

--- Comment #11 from Peter Dimov <pdimov at gmail dot com> ---
So, basically, C++14 and above initialize the padding of

```
    std::atomic<state_type> state{{ 0, 0x2222 }};
```

in `main` to zero, which masks the problem in `generate`. (The problem in
`generate` still exists because the assembly is identical - it just doesn't
trigger because the padding is zero. If we manually poke something nonzero =
into
the padding, it would (ought to) still break.)

Static variables work for the same reason - the padding is guaranteed zero.=