[Bug c++/58407] [C++11] Should warn about deprecated implicit generation of copy constructor/assignment

[Bug c++/58407] [C++11] Should warn about deprecated implicit generation of copy constructor/assignment

[paolo.carlini at oracle dot com]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=58407

Paolo Carlini <paolo.carlini at oracle dot com> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
            Summary|[C++1] Should warn about    |[C++11] Should warn about
                   |deprecated implicit         |deprecated implicit
                   |generation of copy          |generation of copy
                   |constructor/assignment      |constructor/assignment

--- Comment #1 from Paolo Carlini <paolo.carlini at oracle dot com> ---
Out of curiosity, are you aware of other compilers emitting such warning? With
which wording, in case? Because I don't seem to be able to get one from current
clang and icc.

[Bug c++/58407] [C++11] Should warn about deprecated implicit generation of copy constructor/assignment

[akrzemi1 at gmail dot com]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=58407

--- Comment #2 from Andrzej Krzemienski <akrzemi1 at gmail dot com> ---
No. Other compilers (Clang and VS 2010) do not emit such warning either.

[Bug c++/58407] [C++11] Should warn about deprecated implicit generation of copy constructor/assignment

[paolo.carlini at oracle dot com]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=58407

--- Comment #3 from Paolo Carlini <paolo.carlini at oracle dot com> ---
I see. Have to double check our policy in this area, I'm not at all sure that
in general anything in Section D gets a warning.

[Bug c++/58407] [C++11] Should warn about deprecated implicit generation of copy constructor/assignment

[redi at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=58407

--- Comment #4 from Jonathan Wakely <redi at gcc dot gnu.org> ---
I don't think anything in appendix D apart from auto_ptr does.

The warning would be useful to help find places where defaulted definitions
could be added, but I'm not sure I'd want it enabled by -Wall. YMMV.

[Bug c++/58407] [C++11] Should warn about deprecated implicit generation of copy constructor/assignment

[daniel.kruegler at googlemail dot com]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=58407

Daniel Krügler <daniel.kruegler at googlemail dot com> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |daniel.kruegler@googlemail.
                   |                            |com

--- Comment #5 from Daniel Krügler <daniel.kruegler at googlemail dot com> ---
(In reply to Jonathan Wakely from comment #4)

-pedantic would seem like a good candidate, no?
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Subject: [Bug c++/58408] New: [C++11] __thread + trivially_constructible -> error
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http://gcc.gnu.org/bugzilla/show_bug.cgi?idX408

            Bug ID: 58408
           Summary: [C++11] __thread + trivially_constructible -> error
           Product: gcc
           Version: unknown
            Status: UNCONFIRMED
          Severity: enhancement
          Priority: P3
         Component: c++
          Assignee: unassigned at gcc dot gnu.org
          Reporter: ppluzhnikov at google dot com

Google ref: b/10727382

This source:

class Test {
 public:
 Test() = default;
 Test(char *b) { }
 int i;
};
__thread Test test;


fails to compile with current trunk (g++ (GCC) 4.9.0 20130911 (experimental)):

g++ -c -std=c++11 /tmp/t.c

/tmp/t.cc:8:15: error: non-local variable 'test' declared '__thread' needs
dynamic initialization
 __thread Test test;
               ^
/tmp/t.cc:8:15: note: C++11 'thread_local' allows dynamic initialization and
destruction


I don't see a good reason to reject this source -- the required dynamic
initialization is defaulted.

[Bug c++/58407] [C++11] Should warn about deprecated implicit generation of copy constructor/assignment

[akrzemi1 at gmail dot com]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=58407

--- Comment #6 from Andrzej Krzemienski <akrzemi1 at gmail dot com> ---
(In reply to Andrzej Krzemienski from comment #2)
> No. Other compilers (Clang and VS 2010) do not emit such warning either.

Correction: The newest version of Clang does give a warning:
"definition of implicit copy constructor for 'W' is deprecated because it has a
user-declared destructor [-Wdeprecated]"

[Bug c++/58407] [C++11] Should warn about deprecated implicit generation of copy constructor/assignment

[akrzemi1 at gmail dot com]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=58407

--- Comment #7 from Andrzej Krzemienski <akrzemi1 at gmail dot com> ---
Just one remark. A warning in this situation is not to just warn about any
deprecated feature, but to indicate something that is very likely to be a bug
(It used to be legal in C++03, so you couldn't legally warn about it; now the
deprecation is just an additional incentive). My guess is that having this copy
constructor implicitly defined when you have a custom destructor is a potential
bug in half of the cases. (Well, "half" is my guess.)

[Bug c++/58407] [C++11] Should warn about deprecated implicit generation of copy constructor/assignment

[alex at suncho dot com]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=58407

Alex Howlett <alex at suncho dot com> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |alex at suncho dot com

--- Comment #8 from Alex Howlett <alex at suncho dot com> ---
I found this thread because I went Googling after I discovered a bug in my code
resulting from the copy operations being generated despite my having written a
destructor.  I was angry that my compiler (Microsoft) hadn't emitted a warning.

Please add this warning if you haven't already.

[Bug c++/58407] [C++11] Should warn about deprecated implicit generation of copy constructor/assignment

[redi at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=58407

Jonathan Wakely <redi at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
           Keywords|                            |diagnostic
             Status|UNCONFIRMED                 |NEW
   Last reconfirmed|                            |2014-04-27
     Ever confirmed|0                           |1

--- Comment #9 from Jonathan Wakely <redi at gcc dot gnu.org> ---
(In reply to Andrzej Krzemienski from comment #7)
> (It used to be legal in C++03, so you couldn't legally warn about it;

That's not  true, the compiler can (and does) warn about legal code.

I'm confirming this, we will want the warning at some point, and it would allow
us to improve this part of the -Weffc++ warnings:

* Item 11: Define a copy constructor and an assignment operator for classes
with dynamically allocated memory.

(see PR 16166 for more details)

Maybe we could call this warning -Wdeprecated-special-members, and have it
enabled -Weffc++ and in C++11 also by -Wdeprecated

[Bug c++/58407] [C++11] Should warn about deprecated implicit generation of copy constructor/assignment

[akrzemi1 at gmail dot com]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=58407

--- Comment #10 from Andrzej Krzemienski <akrzemi1 at gmail dot com> ---
I guess, by now "item 11" should read "either delete or define ..."