id	summary	reporter	owner	description	type	status	milestone	component	version	severity	resolution	keywords	cc
8577	Multiple qi::match calls on the same stream corrupt input data	Vadim Guchenko <yhw@…>	Joel de Guzman	"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 
}}}
"	Bugs	closed	To Be Determined	spirit	Boost Development Trunk	Problem	invalid