[Bug c++/109396] New: Winit-self doesn't warn when std::move()-d

[Bug c++/109396] New: Winit-self doesn't warn when std::move()-d

[barry.revzin at gmail dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=109396

            Bug ID: 109396
           Summary: Winit-self doesn't warn when std::move()-d
           Product: gcc
           Version: 12.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c++
          Assignee: unassigned at gcc dot gnu.org
          Reporter: barry.revzin at gmail dot com
  Target Milestone: ---

In this example:

#include <utility>

struct A {
    int i_;

    A(int i) : i_(i_) { }
};

struct B {
    int i_;

    B(int i) : i_(std::move(i_)) { }
};

Compiling on gcc trunk with -Wall -Wextra gives me these warnings:

<source>:6:5: warning: 'A::i_' is initialized with itself [-Winit-self]
    6 |     A(int i) : i_(i_) { }
      |     ^
<source>:6:11: warning: unused parameter 'i' [-Wunused-parameter]
    6 |     A(int i) : i_(i_) { }
      |       ~~~~^
<source>: In constructor 'B::B(int)':
<source>:12:11: warning: unused parameter 'i' [-Wunused-parameter]
   12 |     B(int i) : i_(std::move(i_)) { }
      |       ~~~~^

-Winit-self warns on the self-initialization of A::i_ but not of B::i_ (which
is just as much a self-initialization, but via std::move). 

It would be nice if -Winit-self caught the std::move (or other explicit rvalue
cast) case as well.

[Bug c++/109396] Winit-self doesn't warn when std::move()-d

[pinskia at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=109396

Andrew Pinski <pinskia at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
           Severity|normal                      |enhancement

[Bug c++/109396] Winit-self doesn't warn when std::move()-d

[mpolacek at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=109396

Marek Polacek <mpolacek at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
     Ever confirmed|0                           |1
                 CC|                            |mpolacek at gcc dot gnu.org
             Status|UNCONFIRMED                 |ASSIGNED
   Last reconfirmed|                            |2023-04-04
           Assignee|unassigned at gcc dot gnu.org      |mpolacek at gcc dot gnu.org

--- Comment #1 from Marek Polacek <mpolacek at gcc dot gnu.org> ---
Confirmed.  I would've thought that -Wself-move caught that but no.

Likely mine for GCC 14.

[Bug c++/109396] Winit-self doesn't warn when std::move()-d

[cvs-commit at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=109396

--- Comment #2 from GCC Commits <cvs-commit at gcc dot gnu.org> ---
The trunk branch has been updated by Marek Polacek <mpolacek@gcc.gnu.org>:

https://gcc.gnu.org/g:efaaae49b307fcc7e771518da3edae49f92c19db

commit r15-871-gefaaae49b307fcc7e771518da3edae49f92c19db
Author: Marek Polacek <polacek@redhat.com>
Date:   Thu May 23 15:49:42 2024 -0400

    c++: extend -Wself-move for mem-init-list [PR109396]

    We already warn for:

      x = std::move (x);

    which triggers:

      warning: moving 'x' of type 'int' to itself [-Wself-move]

    but bug 109396 reports that this doesn't work for a
member-initializer-list:

      X() : x(std::move (x))

    so this patch amends that.

            PR c++/109396

    gcc/cp/ChangeLog:

            * cp-tree.h (maybe_warn_self_move): Declare.
            * init.cc (perform_member_init): Call maybe_warn_self_move.
            * typeck.cc (maybe_warn_self_move): No longer static.  Change the
            return type to bool.  Also warn when called from
            a member-initializer-list.  Drop the inform call.

    gcc/testsuite/ChangeLog:

            * g++.dg/warn/Wself-move2.C: New test.

[Bug c++/109396] Winit-self doesn't warn when std::move()-d

[mpolacek at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=109396

Marek Polacek <mpolacek at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
         Resolution|---                         |FIXED
             Status|ASSIGNED                    |RESOLVED

--- Comment #3 from Marek Polacek <mpolacek at gcc dot gnu.org> ---
Fixed.

[Bug c++/109396] Winit-self doesn't warn when std::move()-d

[sjames at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=109396

Sam James <sjames at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
   Target Milestone|---                         |15.0