[Bug c++/54325] New: C++11 uniform initialization syntax for argument-less abstract base class constructor fails

[Bug c++/54325] New: C++11 uniform initialization syntax for argument-less abstract base class constructor fails

[moritz at bunkus dot org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=54325

             Bug #: 54325
           Summary: C++11 uniform initialization syntax for argument-less
                    abstract base class constructor fails
    Classification: Unclassified
           Product: gcc
           Version: 4.7.1
            Status: UNCONFIRMED
          Severity: minor
          Priority: P3
         Component: c++
        AssignedTo: unassigned@gcc.gnu.org
        ReportedBy: moritz@bunkus.org


Using {} syntax for base class initialization fails with "cannot allocate an
object of abstract type 'Base'" for abstract base classes with argument-less
constructors. I'll include two code samples. The first one does work with g++
4.6.1 (Ubuntu 11.10), g++ 4.6.3 (Ubuntu 12.04) and clang 3.1 but does NOT work
with g++ 4.7.0 (Ubuntu 12.04) and g++ 4.7.1 (self-compiled). The second one
works with 4.7.0 and 4.7.1 as well.

Example code that does NOT work with 4.7.x but does with older versions/other
compilers:

class Base {
public:
  Base() {};
  virtual ~Base() {};

  virtual void do_stuff() = 0;
};

class Derived: public Base {
public:
  Derived() : Base{} {};
  virtual ~Derived() {};

  virtual void do_stuff() {};
};

int
main() {
  Derived d;

  return 0;
}


Changing Base's constructor to take an additional argument lets it work
suddenly:

class Base {
public:
  int m_dummy;

  Base(int dummy): m_dummy{dummy} {};
  virtual ~Base() {};

  virtual void do_stuff() = 0;
};

class Derived: public Base {
public:
  Derived() : Base{42}  {};
  virtual ~Derived() {};

  virtual void do_stuff() {};
};

int
main() {
  Derived d;

  return 0;
}

$ ~/opt/gcc/4.7.1/bin/g++ -v
Using built-in specs.
COLLECT_GCC=/home/mosu/opt/gcc/4.7.1/bin/g++
COLLECT_LTO_WRAPPER=/home/mosu/opt/gcc/4.7.1/libexec/gcc/x86_64-unknown-linux-gnu/4.7.1/lto-wrapper
Target: x86_64-unknown-linux-gnu
Configured with: ./configure --enable-checking=release --enable-languages=c,c++
--prefix=/home/mosu/opt/gcc/4.7.1
Thread model: posix
gcc version 4.7.1 (GCC)

Actual error message:

$ ~/opt/gcc/4.7.1/bin/g++ -std=c++11 -o fails fails.cpp
fails.cpp: In constructor ‘Derived::Derived()’:
fails.cpp:11:20: error: cannot allocate an object of abstract type ‘Base’
fails.cpp:1:7: note:   because the following virtual functions are pure within
‘Base’:
fails.cpp:6:16: note:   virtual void Base::do_stuff()

[Bug c++/54325] C++11 uniform initialization syntax for argument-less abstract base class constructor fails

[drtwox at tpg dot com.au]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=54325

drtwox at tpg dot com.au changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |drtwox at tpg dot com.au

--- Comment #1 from drtwox at tpg dot com.au 2012-09-07 21:34:57 UTC ---
The failing example can be simplified somewhat.

class base
{
    protected:
        base()
        {}
};

class derived : public base
{
    public:
        derived()
            : base{} // <-- Note the c++11 curly brace syntax
        {}
};

int main()
{
    derived d1;
    return 0;
}

Output:
$ g++-4.7 -std=c++11 -Wall -Wextra -pedantic curly.cpp -o curly
curly.cpp: In constructor ‘derived::derived()’:
curly.cpp:4:13: error: ‘base::base()’ is protected
curly.cpp:19:24: error: within this context

Replace g++4.7 with g++4.6 or clang++3.1 and it compiles without warnings or
errors.

[Bug c++/54325] [4.7/4.8 Regression] C++11 uniform initialization syntax for argument-less abstract base class constructor fails

[paolo.carlini at oracle dot com]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=54325

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

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|UNCONFIRMED                 |NEW
   Last reconfirmed|                            |2012-10-01
            Summary|C++11 uniform               |[4.7/4.8 Regression] C++11
                   |initialization syntax for   |uniform initialization
                   |argument-less abstract base |syntax for argument-less
                   |class constructor fails     |abstract base class
                   |                            |constructor fails
     Ever Confirmed|0                           |1

--- Comment #2 from Paolo Carlini <paolo.carlini at oracle dot com> 2012-10-01 16:56:21 UTC ---
Looks like a regression then.

[Bug c++/54325] [4.7/4.8 Regression] C++11 uniform initialization syntax for argument-less abstract base class constructor fails

[jakub at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=54325

Jakub Jelinek <jakub at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |jakub at gcc dot gnu.org,
                   |                            |jason at gcc dot gnu.org
   Target Milestone|---                         |4.7.3

--- Comment #3 from Jakub Jelinek <jakub at gcc dot gnu.org> 2012-11-19 13:33:41 UTC ---
I think this is probably caused by
http://gcc.gnu.org/viewcvs?root=gcc&view=rev&rev=175674 change.

[Bug c++/54325] [4.7/4.8 Regression] C++11 uniform initialization syntax for argument-less abstract base class constructor fails

[paolo.carlini at oracle dot com]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=54325

--- Comment #4 from Paolo Carlini <paolo.carlini at oracle dot com> 2012-11-20 19:08:21 UTC ---
I just tried and r175673 also rejects the reduced code in Comment #1. Let's see
if I can find the exact revision where we regressed.

[Bug c++/54325] [4.7/4.8 Regression] C++11 uniform initialization syntax for argument-less abstract base class constructor fails

[paolo.carlini at oracle dot com]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=54325

--- Comment #5 from Paolo Carlini <paolo.carlini at oracle dot com> 2012-11-21 00:41:19 UTC ---
We regressed with r175639, the implementation of DR 990:

  http://gcc.gnu.org/ml/gcc-cvs/2011-06/msg01130.html

[Bug c++/54325] [4.7/4.8 Regression] C++11 uniform initialization syntax for argument-less abstract base class constructor fails

[paolo.carlini at oracle dot com]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=54325

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

           What    |Removed                     |Added
----------------------------------------------------------------------------
           Severity|minor                       |normal

--- Comment #6 from Paolo Carlini <paolo.carlini at oracle dot com> 2012-11-21 03:14:14 UTC ---
It seems that the build_value_init calls added by r175639 have issues because
it doesn't have the information that the value initialization is happening from
the default constructor of a derived type.

[Bug c++/54325] [4.7/4.8 Regression] C++11 uniform initialization syntax for argument-less abstract base class constructor fails

[rguenth at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=54325

Richard Biener <rguenth at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
           Keywords|                            |rejects-valid
           Priority|P3                          |P2

[Bug c++/54325] [4.7/4.8 Regression] C++11 uniform initialization syntax for argument-less abstract base class constructor fails

[jason at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=54325

--- Comment #7 from Jason Merrill <jason at gcc dot gnu.org> 2012-12-07 04:54:42 UTC ---
Author: jason
Date: Fri Dec  7 04:54:27 2012
New Revision: 194284

URL: http://gcc.gnu.org/viewcvs?root=gcc&view=rev&rev=194284
Log:
    PR c++/54325
    * tree.c (build_aggr_init_expr): Don't check for abstract class.

Added:
    trunk/gcc/testsuite/g++.dg/cpp0x/initlist-pure.C
Modified:
    trunk/gcc/cp/ChangeLog
    trunk/gcc/cp/tree.c
    trunk/gcc/testsuite/g++.dg/other/abstract3.C

[Bug c++/54325] [4.7/4.8 Regression] C++11 uniform initialization syntax for argument-less abstract base class constructor fails

[jason at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=54325

--- Comment #8 from Jason Merrill <jason at gcc dot gnu.org> 2012-12-07 05:13:42 UTC ---
Author: jason
Date: Fri Dec  7 05:13:33 2012
New Revision: 194290

URL: http://gcc.gnu.org/viewcvs?root=gcc&view=rev&rev=194290
Log:
    PR c++/54325
    * tree.c (build_aggr_init_expr): Don't check for abstract class.

Added:
    branches/gcc-4_7-branch/gcc/testsuite/g++.dg/cpp0x/initlist-pure.C
Modified:
    branches/gcc-4_7-branch/gcc/cp/ChangeLog
    branches/gcc-4_7-branch/gcc/cp/tree.c
    branches/gcc-4_7-branch/gcc/testsuite/g++.dg/other/abstract3.C

[Bug c++/54325] [4.7/4.8 Regression] C++11 uniform initialization syntax for argument-less abstract base class constructor fails

[jason at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=54325

Jason Merrill <jason at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|NEW                         |RESOLVED
         Resolution|                            |FIXED
         AssignedTo|unassigned at gcc dot       |jason at gcc dot gnu.org
                   |gnu.org                     |

--- Comment #9 from Jason Merrill <jason at gcc dot gnu.org> 2012-12-07 05:15:03 UTC ---
Fixed.

[Bug c++/54325] [4.7/4.8 Regression] C++11 uniform initialization syntax for argument-less abstract base class constructor fails

[paolo.carlini at oracle dot com]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=54325

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

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

--- Comment #10 from Paolo Carlini <paolo.carlini at oracle dot com> 2012-12-27 08:41:13 UTC ---
Let's reopen this: testcase in Comment #1 isn't fixed yet.

[Bug c++/54325] [4.7/4.8 Regression] C++11 uniform initialization syntax for argument-less abstract base class constructor fails

[jason at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=54325

--- Comment #11 from Jason Merrill <jason at gcc dot gnu.org> 2013-01-02 20:54:46 UTC ---
Author: jason
Date: Wed Jan  2 20:54:42 2013
New Revision: 194820

URL: http://gcc.gnu.org/viewcvs?root=gcc&view=rev&rev=194820
Log:
    PR c++/54325
    * call.c (build_new_method_call_1): Don't use build_value_init for
    user-provided default constructors.

Added:
    trunk/gcc/testsuite/g++.dg/cpp0x/initlist-protected.C
Modified:
    trunk/gcc/cp/ChangeLog
    trunk/gcc/cp/call.c

[Bug c++/54325] [4.7/4.8 Regression] C++11 uniform initialization syntax for argument-less abstract base class constructor fails

[jason at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=54325

--- Comment #12 from Jason Merrill <jason at gcc dot gnu.org> 2013-01-02 20:56:37 UTC ---
Author: jason
Date: Wed Jan  2 20:56:29 2013
New Revision: 194821

URL: http://gcc.gnu.org/viewcvs?root=gcc&view=rev&rev=194821
Log:
    PR c++/54325
    * call.c (build_new_method_call_1): Don't use build_value_init for
    user-provided default constructors.

Added:
    branches/gcc-4_7-branch/gcc/testsuite/g++.dg/cpp0x/initlist-protected.C
Modified:
    branches/gcc-4_7-branch/gcc/cp/ChangeLog
    branches/gcc-4_7-branch/gcc/cp/call.c

[Bug c++/54325] [4.7/4.8 Regression] C++11 uniform initialization syntax for argument-less abstract base class constructor fails

[jason at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=54325

Jason Merrill <jason at gcc dot gnu.org> changed:

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

--- Comment #13 from Jason Merrill <jason at gcc dot gnu.org> 2013-01-02 21:05:46 UTC ---
Testcase from comment #1 fixed as well.