[Boost-bugs] [Boost C++ Libraries] #11286: Code in boost/endian/buffers.hpp violates old C++03 Standard

Subject: [Boost-bugs] [Boost C++ Libraries] #11286: Code in boost/endian/buffers.hpp violates old C++03 Standard
From: Boost C++ Libraries (noreply_at_[hidden])
Date: 2015-05-11 20:06:23

#11286: Code in boost/endian/buffers.hpp violates old C++03 Standard
------------------------------+------------------------
 Reporter:  Sergey.Sprogis@…  |      Owner:  bemandawes
     Type:  Bugs              |     Status:  new
Milestone:  To Be Determined  |  Component:  endian
  Version:  Boost 1.58.0      |   Severity:  Problem
 Keywords:                    |
------------------------------+------------------------
 1. Description of the failure.

  endian/test/endian_in_union_test.cc fails with Oracle Studio C++ compiler
 on Solaris producing bunch of similar error message similar shown below::

  "CC"   -KPIC -DBOOST_ALL_NO_LIB=1 -DNDEBUG -I"../../.." -o
 "../../../bin.v2/libs/endian/test/endian_in_union_test.test/sun/release
 /stdlib-sun-stlport/threading-multi/endian_in_union_test.o"
 "endian_in_union_test.cpp"

 "endian_in_union_test.cpp", line 77: Error: A union member cannot have a
 user-defined assignment operator.

  2. Cause of the failure.

  The failure can be demonstrated with 4 lines small independent t.cpp
 test:

    class endian_buffer {

       endian &endian_buffer = (int val);
    };

    union U { endian_buffer m; };

    CC -c t.cpp

    "t.cc", line 4: Error: A union member cannot have a user-defined
 assignment operator.

   Small test above has been  extracted  and slightly modified from the
 code shown below located under  boost/endian/buffers.hpp

     template <typename T, std::size_t n_bits>

     class endian_buffer< order::big, T, n_bits, align::no >

     {
         ....

         endian_buffer & operator=(T val) BOOST_NOEXCEPT   // Line 358

    C++03 Standard explicitly rejects the use of classes with user-defined
 assignment operators in unions:

    C++2003 9.5 [class.union]p1

    An object of a class with a ... non-trivial copy assignment operator
 (13.5.3, 12.8) cannot be a member of a union.

     In C++11  the code is valid, as a result of apply   "Unrestricted
 Unions" feature.
     But since it is a C++11 feature, it should not  affect C++03
 compilation.

    Seems like g++  has a bug here compiling this code successfully in both
 C++03 and C++11 mode.

-- 
Ticket URL: <https://svn.boost.org/trac/boost/ticket/11286>
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