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From: "redi at gcc dot gnu.org" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug tree-optimization/108374] [12/13 Regression] unexpected
 -Wstringop-overflow when using std::atomic and std::shared_ptr
Date: Thu, 12 Jan 2023 10:10:34 +0000
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https://gcc.gnu.org/bugzilla/show_bug.cgi?id=3D108374

--- Comment #5 from Jonathan Wakely <redi at gcc dot gnu.org> ---
(In reply to Richard Biener from comment #4)
> Hmm, but then the program is bogus, no?  And a diagnostic warranted.

No.

> At least if it is well-defined to have a nullptr =3D=3D pointer.

It's well defined, but that doesn't mean the program is bogus. It just means
you can't call that function with such a value.

> So I'd be inclined to close as INVALID?

No, I don't think so. It would only be invalid if you called f(nullptr) or
similar.

The code is basically doing something like:

int f(const A* p, bool is_valid)
{
  const A* q =3D is_valid ? p : nullptr;
  return *q;
}

Instead of complaining that q might be null, we can optimize that to return=
 *p.

It might be nicer to optimize it to:

  if (!p)
    __builtin_trap();
  return *p;

but either way, we can't just declare the whole program to be invalid becau=
se
it's possible to call the function incorrectly.=