[Bug c++/59480] New: Missing error diagnostic: friend declaration specifying a default argument must be a definition

[Bug c++/59480] New: Missing error diagnostic: friend declaration specifying a default argument must be a definition

[burnus at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=59480

            Bug ID: 59480
           Summary: Missing error diagnostic: friend declaration
                    specifying a default argument must be a definition
           Product: gcc
           Version: 4.9.0
            Status: UNCONFIRMED
          Keywords: accepts-invalid, diagnostic
          Severity: normal
          Priority: P3
         Component: c++
          Assignee: unassigned at gcc dot gnu.org
          Reporter: burnus at gcc dot gnu.org

The following code compiles with GCC with "g++ -Wall -Werror -std=c++11
-pedantic":

class test {
  friend int bar(int = true);
};

However, with Clang++ it is rejected with:
  error: friend declaration specifying a default argument must be a definition


In N3337, one finds at the end of the paragraph 8.3.6.4 [dcl.fct.default]: "If
a friend declaration specifies a default argument expression, that declaration
shall be a definition and shall be the only declaration of the function or
function template in the translation unit."

[Bug c++/59480] Missing error diagnostic: friend declaration specifying a default argument must be a definition

[burnus at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=59480

--- Comment #1 from Tobias Burnus <burnus at gcc dot gnu.org> ---
See also http://www.open-std.org/jtc1/sc22/wg21/docs/cwg_defects.html#136

[Bug c++/59480] Missing error diagnostic: friend declaration specifying a default argument must be a definition

[paolo.carlini at oracle dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=59480

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

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |filip.roseen at gmail dot com

--- Comment #2 from Paolo Carlini <paolo.carlini at oracle dot com> ---
*** Bug 61470 has been marked as a duplicate of this bug. ***

[Bug c++/59480] Missing error diagnostic: friend declaration specifying a default argument must be a definition

[ville.voutilainen at gmail dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=59480

Ville Voutilainen <ville.voutilainen at gmail dot com> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|UNCONFIRMED                 |NEW
   Last reconfirmed|                            |2014-12-14
                 CC|                            |ville.voutilainen at gmail dot com
     Ever confirmed|0                           |1
      Known to fail|                            |4.8.2, 4.9.1, 5.0

[Bug c++/59480] Missing error diagnostic: friend declaration specifying a default argument must be a definition

[manu at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=59480

Manuel López-Ibáñez <manu at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
   Last reconfirmed|2014-12-14 00:00:00         |2015-8-24
                 CC|                            |manu at gcc dot gnu.org

--- Comment #3 from Manuel López-Ibáñez <manu at gcc dot gnu.org> ---
Strangely enough, this is one of the bugs in GCC that OpenMandriva developers
present as a reason for them switching to Clang as the default compiler.

http://mirror.as35701.net/video.fosdem.org//2015/devroom-llvm_toolchain/openmandriva__CAM_ONLY.mp4
(around 16:00)

class A {
  friend void b(int, const char *s= 0);
};
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Subject: [Bug c++/59480] Missing error diagnostic: friend declaration specifying a default argument must be a definition
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https://gcc.gnu.org/bugzilla/show_bug.cgi?id=59480

--- Comment #4 from Jonathan Wakely <redi at gcc dot gnu.org> ---
(In reply to Manuel López-Ibáñez from comment #3)
> Strangely enough, this is one of the bugs in GCC that OpenMandriva
> developers present as a reason for them switching to Clang as the default
> compiler.
> 
> http://mirror.as35701.net/video.fosdem.org//2015/devroom-llvm_toolchain/
> openmandriva__CAM_ONLY.mp4 (around 16:00)
> 
> class A {
>   friend void b(int, const char *s= 0);
> };

And on the very next slide they give another example of a bug accepted by GCC,
which is rejected by every version of GCC I tried, going back to 4.4, so I
suspect they are looking for reasons to justify a move they wanted to make
anyway, and this bug is incidental.
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https://gcc.gnu.org/bugzilla/show_bug.cgi?idg298

--- Comment #3 from Andrew Pinski <pinskia at gcc dot gnu.org> ---
Also does using -fwrapv fix the problem?  It might be the case gap just has
undefined code in it and now we produce better code.

[Bug c++/59480] Missing error diagnostic: friend declaration specifying a default argument must be a definition

[redi at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=59480

--- Comment #5 from Jonathan Wakely <redi at gcc dot gnu.org> ---
And the next slide shows a "missing warning", that actually GCC has warned
about since 4.8

And the next slide is a gnu89-inline issue, which would also show up with GCC 5
due to the -std=c11 default.

etc. etc.

[Bug c++/59480] Missing error diagnostic: friend declaration specifying a default argument must be a definition

[manu at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=59480

--- Comment #6 from Manuel López-Ibáñez <manu at gcc dot gnu.org> ---
(In reply to Jonathan Wakely from comment #4)
> And on the very next slide they give another example of a bug accepted by
> GCC, which is rejected by every version of GCC I tried, going back to 4.4,
> so I suspect they are looking for reasons to justify a move they wanted to
> make anyway, and this bug is incidental.

Indeed. What surprises me is that, contrary to the *BSD distros, their actual
motivation does not seem to be the license, so what is it?
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https://gcc.gnu.org/bugzilla/show_bug.cgi?idg329

H.J. Lu <hjl.tools at gmail dot com> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|UNCONFIRMED                 |RESOLVED
         Resolution|---                         |FIXED
   Target Milestone|---                         |6.0

--- Comment #3 from H.J. Lu <hjl.tools at gmail dot com> ---
Fixed for GCC 6.