[Boost-bugs] [Boost C++ Libraries] #12941: Ignore return value from BOOST_INTERLOCKED_EXCHANGE

Subject: [Boost-bugs] [Boost C++ Libraries] #12941: Ignore return value from BOOST_INTERLOCKED_EXCHANGE
From: Boost C++ Libraries (noreply_at_[hidden])
Date: 2017-03-30 10:03:51

#12941: Ignore return value from BOOST_INTERLOCKED_EXCHANGE
------------------------------+----------------------
 Reporter:  mattyclarkson@…   |      Owner:  anthonyw
     Type:  Bugs              |     Status:  new
Milestone:  To Be Determined  |  Component:  thread
  Version:  Boost 1.63.0      |   Severity:  Problem
 Keywords:                    |
------------------------------+----------------------
 Warnings are created by MinGW for ignoring the return value in
 `boost::detail::interlocked_read_acquire`:


 {{{
 namespace boost
 {
     namespace detail
     {
         inline long interlocked_read_acquire(long volatile* x)
 BOOST_NOEXCEPT
         {
             return BOOST_INTERLOCKED_COMPARE_EXCHANGE(x,0,0);
         }
         inline void* interlocked_read_acquire(void* volatile* x)
 BOOST_NOEXCEPT
         {
             return BOOST_INTERLOCKED_COMPARE_EXCHANGE_POINTER(x,0,0);
         }
         inline void interlocked_write_release(long volatile* x,long value)
 BOOST_NOEXCEPT
         {
             BOOST_INTERLOCKED_EXCHANGE(x,value);
         }
         inline void interlocked_write_release(void* volatile* x,void*
 value) BOOST_NOEXCEPT
         {
             BOOST_INTERLOCKED_EXCHANGE_POINTER(x,value);
         }
     }
 }
 }}}

 My proposed fix it to cast the return value to `void`:


 {{{
 namespace boost
 {
     namespace detail
     {
         inline long interlocked_read_acquire(long volatile* x)
 BOOST_NOEXCEPT
         {
             return BOOST_INTERLOCKED_COMPARE_EXCHANGE(x,0,0);
         }
         inline void* interlocked_read_acquire(void* volatile* x)
 BOOST_NOEXCEPT
         {
             return BOOST_INTERLOCKED_COMPARE_EXCHANGE_POINTER(x,0,0);
         }
         inline void interlocked_write_release(long volatile* x,long value)
 BOOST_NOEXCEPT
         {
             (void)BOOST_INTERLOCKED_EXCHANGE(x,value);
         }
         inline void interlocked_write_release(void* volatile* x,void*
 value) BOOST_NOEXCEPT
         {
             (void)BOOST_INTERLOCKED_EXCHANGE_POINTER(x,value);
         }
     }
 }
 }}}

 It would also be possible to use `static_cast<void>(...)`:

 {{{
 namespace boost
 {
     namespace detail
     {
         inline long interlocked_read_acquire(long volatile* x)
 BOOST_NOEXCEPT
         {
             return BOOST_INTERLOCKED_COMPARE_EXCHANGE(x,0,0);
         }
         inline void* interlocked_read_acquire(void* volatile* x)
 BOOST_NOEXCEPT
         {
             return BOOST_INTERLOCKED_COMPARE_EXCHANGE_POINTER(x,0,0);
         }
         inline void interlocked_write_release(long volatile* x,long value)
 BOOST_NOEXCEPT
         {
             static_cast<void>(BOOST_INTERLOCKED_EXCHANGE(x,value));
         }
         inline void interlocked_write_release(void* volatile* x,void*
 value) BOOST_NOEXCEPT
         {
 static_cast<void>(BOOST_INTERLOCKED_EXCHANGE_POINTER(x,value));
         }
     }
 }
 }}}

-- 
Ticket URL: <https://svn.boost.org/trac/boost/ticket/12941>
Boost C++ Libraries <http://www.boost.org/>
Boost provides free peer-reviewed portable C++ source libraries.