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From: "redi at gcc dot gnu.org" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug c++/97435] Lifetime of temporaries not correctly extending when optiimzation are enabled
Date: Thu, 15 Oct 2020 08:51:38 +0000 [thread overview]
Message-ID: <bug-97435-4-2NHznzviMl@http.gcc.gnu.org/bugzilla/> (raw)
In-Reply-To: <bug-97435-4@http.gcc.gnu.org/bugzilla/>
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=97435
Jonathan Wakely <redi at gcc dot gnu.org> changed:
What |Removed |Added
----------------------------------------------------------------------------
Status|UNCONFIRMED |RESOLVED
Resolution|--- |INVALID
--- Comment #2 from Jonathan Wakely <redi at gcc dot gnu.org> ---
Yes, this is undefined behaviour.
It's equivalent to:
const int& f(const int& i) { return i; }
const int& i = f(5);
int j = i; // undefined
Lifetime is only extended if the reference is bound directly to the temporary
object, not to another reference that happens to be bound to it inside some
function.
Consider the case where the body of A::operator+= is not visible to the
compiler. How is it supposed to know whether the returned value refers to *this
or not, and therefore how is it supposed to know whether to destroy the
temporary A(5) immediately or not?
prev parent reply other threads:[~2020-10-15 8:51 UTC|newest]
Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-10-15 6:44 [Bug c++/97435] New: " chris at chrissavoie dot com
2020-10-15 7:33 ` [Bug c++/97435] " rguenth at gcc dot gnu.org
2020-10-15 8:51 ` redi at gcc dot gnu.org [this message]
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