Re: [Boost-bugs] [Boost C++ Libraries] #4090: Macroses BOOST_PP_SEQ_FOR_EACH_*R are not reenterable

Subject: Re: [Boost-bugs] [Boost C++ Libraries] #4090: Macroses BOOST_PP_SEQ_FOR_EACH_*R are not reenterable
From: Boost C++ Libraries (noreply_at_[hidden])
Date: 2015-05-17 22:53:43

#4090: Macroses BOOST_PP_SEQ_FOR_EACH_*R are not reenterable
-------------------------------+---------------------------
  Reporter:  Andrey <andry@…>  |      Owner:  no-maintainer
      Type:  Bugs              |     Status:  new
 Milestone:                    |  Component:  preprocessor
   Version:  Boost 1.39.0      |   Severity:  Problem
Resolution:                    |   Keywords:
-------------------------------+---------------------------

Comment (by eldiener):

 First off you are not using BOOST_PP_SEQ_FOR_EACH but
 BOOST_PP_SEQ_FOR_EACH_I. BOOST_PP_SEQ_FOR_EACH_I is not re-entrant to
 BOOST_PP_SEQ_FOR_EACH_I, for obvious reasons ( you are calling back to the
 same macro in the expansion of a macro and the C++ preprocessor is not re-
 entrant in that way ). BOOST_PP_SEQ_FOR_EACH_I is not re-entrant to
 BOOST_PP_SEQ_FOR_EACH_I_R, which is what you are doing above, because both
 share the same code for the internal BOOST_PP_FOR invocation as far as the
 pred, op, and macro code is concerned.

 The documentation for BOOST_PP_SEQ_FOR_EACH_I_R says that "It reenters
 BOOST_PP_FOR with maximum efficiency". That does not mean that it itself
 can be called from BOOST_PP_SEQ_FOR_EACH_I. It can't for the reason stated
 above.

-- 
Ticket URL: <https://svn.boost.org/trac/boost/ticket/4090#comment:1>
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