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From: "arthur.j.odwyer at gmail dot com" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug libstdc++/114817] Wrong codegen for std::copy of "trivially copyable but not trivially assignable" type
Date: Fri, 26 Apr 2024 18:43:37 +0000	[thread overview]
Message-ID: <bug-114817-4-pG9uqQXl6o@http.gcc.gnu.org/bugzilla/> (raw)
In-Reply-To: <bug-114817-4@http.gcc.gnu.org/bugzilla/>

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=114817

--- Comment #3 from Arthur O'Dwyer <arthur.j.odwyer at gmail dot com> ---
https://github.com/boostorg/container/issues/153 , from 2020, is another
similar issue. There, boost::container::vector had assumed that if
__has_trivial_copy(T) and is_copy_constructible_v<T>, then T could be relocated
via memcpy; but in fact __has_trivial_copy(T) is also true for move-only types.
So it was possible to create a type such that (__has_trivial_copy(T) &&
__is_constructible(T, T&)) and yet not __is_trivially_constructible(T, T&).

// https://godbolt.org/z/x5Wda1M6E
struct T {
    template<class U> T(U&&);
    T(T&&);
    ~T();
};
static_assert(__has_trivial_copy(T) && __is_constructible(T, T&));
  // ...and yet...
static_assert(not __is_trivially_constructible(T, T&));

      parent reply	other threads:[~2024-04-26 18:43 UTC|newest]

Thread overview: 4+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2024-04-23  4:02 [Bug libstdc++/114817] New: " arthur.j.odwyer at gmail dot com
2024-04-23 18:29 ` [Bug libstdc++/114817] " arthur.j.odwyer at gmail dot com
2024-04-24  3:31 ` de34 at live dot cn
2024-04-26 18:43 ` arthur.j.odwyer at gmail dot com [this message]

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