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From: "lopresti at gmail dot com" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug middle-end/32667] block copy with exact overlap is expanded as
 memcpy
Date: Fri, 06 Jan 2023 18:48:22 +0000
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https://gcc.gnu.org/bugzilla/show_bug.cgi?id=3D32667

--- Comment #22 from Patrick J. LoPresti <lopresti at gmail dot com> ---
I disagree that bug 108296 is a duplicate. That bug requires code that, at
least arguably, invokes undefined behavior. See e.g.
https://stackoverflow.com/q/7292862/ and https://stackoverflow.com/q/610708=
28/.

This bug is about clearly valid C++ code (object self-assignment) for which=
 GCC
emits clearly invalid calls to memcpy() (with dest =3D=3D src).

Now, I suspect what Andrew is thinking is that both of these bugs could be
resolved by invoking memmove() instead of memcpy(). That seems like a
reasonable idea to me, since small assignments get inlined and large
assignments can amortize the overhead.

But this bug could also be resolved in other ways, a few of which have been
suggested in these comments.=