[Boost-bugs] [Boost C++ Libraries] #8577: Multiple qi::match calls on the same stream corrupt input data

Subject: [Boost-bugs] [Boost C++ Libraries] #8577: Multiple qi::match calls on the same stream corrupt input data
From: Boost C++ Libraries (noreply_at_[hidden])
Date: 2013-05-16 03:12:08

#8577: Multiple qi::match calls on the same stream corrupt input data
---------------------------------------------+------------------------------
 Reporter:  Vadim Guchenko <yhw@…>           |       Owner:  djowel 
     Type:  Bugs                             |      Status:  new    
Milestone:  To Be Determined                 |   Component:  spirit 
  Version:  Boost Development Trunk          |    Severity:  Problem
 Keywords:                                   |  
---------------------------------------------+------------------------------
 qi::match cannot be reliably called multiple times on the same input
 stream. Probably it consumes some characters from the stream to do look-
 ahead but doesn't return them back to the stream on destruction. So it
 only works reliably if it's the last extraction operator for a given
 stream.

 I know there may be problems to return more than one character to a
 stream, so if it's the expected qi::match behavior, it's worth to be
 mentioned in the documentation.

 The following code illustrates the problem:

 {{{
 #include <boost/spirit/include/qi.hpp>
 #include <boost/spirit/include/qi_match.hpp>
 #include <iostream>
 #include <sstream>

 namespace qi = boost::spirit::qi;

 int main() {
     std::istringstream is("11 22 33 44 55 ");
     is >> std::noskipws;
     int n = 0;

     for (int i = 0; i < 5; ++i) {
         is >> qi::match(qi::int_ >> +qi::lit(' '), n);
         assert(is);
         std::cout << n << ' ';
     }
 }
 }}}

 {{{
 Expected output: 11 22 33 44 55
 Actual output:   11 2 3 4 5
 }}}

-- 
Ticket URL: <https://svn.boost.org/trac/boost/ticket/8577>
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