Re: [Boost-bugs] [Boost C++ Libraries] #8408: Boost is not compatible with Clang's -Wimplicit-fallthrough diagnostic

Subject: Re: [Boost-bugs] [Boost C++ Libraries] #8408: Boost is not compatible with Clang's -Wimplicit-fallthrough diagnostic
From: Boost C++ Libraries (noreply_at_[hidden])
Date: 2013-04-08 18:31:38

#8408: Boost is not compatible with Clang's -Wimplicit-fallthrough diagnostic
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  Reporter:  Alexander Kornienko <alexfh@…>           |       Owner:  johnmaddock
      Type:  Patches                                  |      Status:  new        
 Milestone:  To Be Determined                         |   Component:  config     
   Version:  Boost Development Trunk                  |    Severity:  Problem    
Resolution:                                           |    Keywords:             
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Comment (by Alexander Kornienko <alexfh@…>):

 Replying to [comment:6 johnmaddock]:
 > >On unsupported compilers (or in non-C++11 mode in Clang) it expands to
 "do {} while(0)", which requires a semicolon as well. This construct was
 meant to look and behave consistently with 'break;' statement, which it
 can be an alternative to in many cases. So requiring a semicolon after it
 seems to be reasonable.
 >
 > "do{}while(0)" generates a "Conditional expression is constant" warning
 on MSVC.
 >
 > Defining to "(void)" might do it, but it wouldn't surprise me if some
 compiler warned about that too in future :-(

 How about a separate define for Clang with C++11, and a separate one for
 MSVC? All others can use "do{}while(0)".

 As an idea for compilers that warn on "do{}while(0)", we could use a
 function call without trailing semicolon:
 {{{
 void boost_fallthrough() {}
 #define BOOST_FALLTHROUGH boost_fallthrough()
 }}}

 Then all implementations will require a trailing semicolon, which will
 help to avoid at least one type of errors in usages of this macro.

-- 
Ticket URL: <https://svn.boost.org/trac/boost/ticket/8408#comment:7>
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