Re: [Boost-bugs] [Boost C++ Libraries] #4421: fix for #4400

Subject: Re: [Boost-bugs] [Boost C++ Libraries] #4421: fix for #4400
From: Boost C++ Libraries (noreply_at_[hidden])
Date: 2010-08-30 16:05:26

#4421: fix for #4400
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  Reporter:  Wolf Lammen <ookami1@…>       |       Owner:  no-maintainer
      Type:  Patches                       |      Status:  new          
 Milestone:  Boost 1.44.0                  |   Component:  preprocessor 
   Version:  Boost 1.44.0                  |    Severity:  Problem      
Resolution:                                |    Keywords:               
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Comment (by ookami1@…):

 Replying to [comment:3 steven_watanabe]:
 > Never mind.  I missed the changes to split.hpp.  However, I'm not sure
 that n ## seq is legal if seq is empty.

 You are right here, this will not work, when an empty sequence (actually
 it will not be exactly empty, but BOOST_PP_EMPTY instead) is submitted.
 Fortunately, you will never call BOOST_PP_SEQ_REPLACE with an empty
 sequence. And calls to BOOST_PP_REST_N or BOOST_PP_FIRST_N with empty
 sequences are considered illegal as well, according to the documentation.
 So the problem reduces to a possibly internal usage of the latter macros,
 exploiting the fact, that they internally appended a (nil) to sequences.
 If I remember right, I already checked on that condition, but I am a bit
 unsure right now, so I will do it again.

 If it turns out to be a problem, the solution seems straightforward: For
 Microwerks (only):

 #define BOOST_PP_SEQ_SPLIT_0_BOOST_PP_EMPTY BOOST_PP_EMPTY, BOOST_PP_EMPTY

 cheers Wolf Lammen

-- 
Ticket URL: <https://svn.boost.org/trac/boost/ticket/4421#comment:6>
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