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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 20:52:58 -0400	[thread overview]
Message-ID: <f036d0b6-f68c-404c-f853-762b19cc5123@redhat.com> (raw)
In-Reply-To: <YwfuTuK4lyZOw0tL@redhat.com>

On 8/25/22 17:49, Marek Polacek wrote:
> On Thu, Aug 25, 2022 at 09:25:43AM -0400, Jason Merrill wrote:
>> 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.
> 
> Ok, I've added the REFERENCE_REF stripping.  But I've still left the
> COMPONENT_REF in.  Perhaps we could say "moving a member" to itself for
> COMPONENT_REFs.  Or just say "moving 'x' of type 'int' to itself" and
> avoid all of this.  :)

Sure, that would be simpler.  In any case, we shouldn't call member 
references variables.

Jason


  reply	other threads:[~2022-08-26  0:53 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
2022-08-25 21:49                   ` Marek Polacek
2022-08-26  0:52                     ` Jason Merrill [this message]
2022-08-26 17:04                       ` [PATCH v5] " Marek Polacek
2022-08-26 17:59                         ` Jason Merrill

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