From: Jason Merrill <jason@redhat.com>
To: Marek Polacek <polacek@redhat.com>
Cc: GCC Patches <gcc-patches@gcc.gnu.org>
Subject: Re: [PATCH v4] c++: Implement -Wself-move warning [PR81159]
Date: Thu, 25 Aug 2022 09:25:43 -0400 [thread overview]
Message-ID: <ace7f15f-436c-1a1d-c7e5-2777d8cd6d41@redhat.com> (raw)
In-Reply-To: <YwaYk2IiHF7tomQP@redhat.com>
On 8/24/22 17:30, Marek Polacek wrote:
> On Tue, Aug 23, 2022 at 05:27:00PM -0400, Jason Merrill wrote:
>> On 8/23/22 09:39, Marek Polacek wrote:
>>> + tree arg = CALL_EXPR_ARG (fn, 0);
>>> + extract_op (arg);
>>> + if (TREE_CODE (arg) == ADDR_EXPR)
>>> + arg = TREE_OPERAND (arg, 0);
>>> + tree type = TREE_TYPE (lhs);
>>> + lhs = maybe_undo_parenthesized_ref (lhs);
>>> + STRIP_ANY_LOCATION_WRAPPER (lhs);
>>> + const bool print_var_p = (DECL_P (lhs)
>>> + || REFERENCE_REF_P (lhs)
>>> + || TREE_CODE (lhs) == COMPONENT_REF);
>>
>> Why include REFERENCE_REF_P and COMPONENT_REF? Reference refs should be
>> stripped before this test, member refs aren't variables.
>
> I'm checking REFERENCE_REF_P and COMPONENT_REF to say "moving a variable"
> in #1 and #3. The REFERENCE_REF_P check means that we also say "variable"
> for #2. Sure, "A variable is introduced by the declaration of a reference
> other than a non-static data member", but I'm not sure if users care about
> that here?
>
> If I strip REFERENCE_REFs before the check then the result will be the
> same.
That's what I was suggesting, yes: Strip the REFERENCE_REF so DECL_P can
see the decl.
I don't see where COMPONENT_REF comes in?
> Or I could keep only the DECL_P check, but then we'll say "moving
> an expression" for #1 and #2, which seems strange.
>
> struct S {
> int x;
> int &r;
> void foo () {
> x = std::move (x); // #1
> r = std::move (r); // #2
> };
> };
>
> void
> foo (int &r)
> {
> r = std::move (r); // #3
> }
>
> Marek
>
next prev parent reply other threads:[~2022-08-25 13:25 UTC|newest]
Thread overview: 14+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-08-09 16:37 [PATCH] " Marek Polacek
2022-08-15 19:54 ` Jason Merrill
2022-08-18 20:19 ` [PATCH v2] " Marek Polacek
2022-08-19 0:33 ` Jason Merrill
2022-08-19 22:34 ` [PATCH v3] " Marek Polacek
2022-08-20 21:31 ` Jason Merrill
2022-08-23 16:39 ` [PATCH v4] " Marek Polacek
2022-08-23 21:27 ` Jason Merrill
2022-08-24 21:30 ` Marek Polacek
2022-08-25 13:25 ` Jason Merrill [this message]
2022-08-25 21:49 ` Marek Polacek
2022-08-26 0:52 ` Jason Merrill
2022-08-26 17:04 ` [PATCH v5] " Marek Polacek
2022-08-26 17:59 ` Jason Merrill
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