[Bug c++/61174] New: [4.9 Regression] Bad resolving of specialized template with const-qualified member function

[Bug c++/61174] New: [4.9 Regression] Bad resolving of specialized template with const-qualified member function

[ncornu@aldebaran-robotics.com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=61174

            Bug ID: 61174
           Summary: [4.9 Regression] Bad resolving of specialized template
                    with const-qualified member function
           Product: gcc
           Version: 4.9.0
            Status: UNCONFIRMED
          Severity: major
          Priority: P3
         Component: c++
          Assignee: unassigned at gcc dot gnu.org
          Reporter: ncornu@aldebaran-robotics.com

Created attachment 32788
  --> https://gcc.gnu.org/bugzilla/attachment.cgi?id=32788&action=edit
A file reproducing the bug

With 4.8 it compiles.

With 4.9.0 we got:
main.cpp: In instantiation of ‘struct A<int (C::*)() const>’:
main.cpp:22:8:   required from ‘void make(T) [with T = int (C::*)() const]’
main.cpp:27:13:   required from here
main.cpp:6:18: attention : invalid application of ‘sizeof’ to a function type
[-Wpointer-arith]
   int fail[sizeof(T) - 1000];
                  ^
main.cpp: In function ‘void make(T) [with T = int (C::*)() const]’:
main.cpp:22:8: erreur: size of variable ‘a’ is too large
   A<T> a;
        ^

Because it use the attribute specialization of our template.
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From: "paolo.carlini at oracle dot com" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug c++/61174] Bad resolving of specialized template with const-qualified member function
Date: Tue, 13 May 2014 13:18:00 -0000
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https://gcc.gnu.org/bugzilla/show_bug.cgi?ida174

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

           What    |Removed                     |Added
----------------------------------------------------------------------------
            Summary|[4.9 Regression] Bad        |Bad resolving of
                   |resolving of specialized    |specialized template with
                   |template with               |const-qualified member
                   |const-qualified member      |function
                   |function                    |
           Severity|major                       |normal

--- Comment #1 from Paolo Carlini <paolo.carlini at oracle dot com> ---
Pretty sure this is invalid, thus not a regression (clang & SolarisStudio
agree)

[Bug c++/61174] Bad resolving of specialized template with const-qualified member function

[paolo.carlini at oracle dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=61174

--- Comment #2 from Paolo Carlini <paolo.carlini at oracle dot com> ---
By the way, this does *not* compile with 4.8, neither with 4.7, ...

[Bug c++/61174] Bad resolving of specialized template with const-qualified member function

[ncornu@aldebaran-robotics.com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=61174

--- Comment #3 from alkino <ncornu@aldebaran-robotics.com> ---
It works with ideone (gcc-4.8.1) https://ideone.com/t8Jww2

[Bug c++/61174] Bad resolving of specialized template with const-qualified member function

[paolo.carlini at oracle dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=61174

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

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|UNCONFIRMED                 |RESOLVED
         Resolution|---                         |INVALID

--- Comment #4 from Paolo Carlini <paolo.carlini at oracle dot com> ---
But the testcase is invalid.

[Bug c++/61174] Bad resolving of specialized template with const-qualified member function

[ncornu@aldebaran-robotics.com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=61174

--- Comment #5 from alkino <ncornu@aldebaran-robotics.com> ---
Can you tell me why, please?

Thanks to look at it.

[Bug c++/61174] Bad resolving of specialized template with const-qualified member function

[paolo.carlini at oracle dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=61174

--- Comment #6 from Paolo Carlini <paolo.carlini at oracle dot com> ---
Instead of starting from scratch, why don't you use
std::is_member_function_pointer? It handles correctly all sorts of member
functions. Alternately, study the implementation and learn from it.

In any case, you have of course a problem with the constness of g, you would
have to add:

template<typename C, typename T> struct A<T (C::*)() const>
{
  int ok;
};

because otherwise the first specialization - as you can easily learn from
<type_traits> - matches f and all sorts of member pointers, for that matter.

[Bug c++/61174] Bad resolving of specialized template with const-qualified member function

[ncornu@aldebaran-robotics.com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=61174

--- Comment #7 from alkino <ncornu@aldebaran-robotics.com> ---
I only spot the wrong bug. Here it is: 
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=61182