How to use boost::error_info correctly?

Question

I\'m trying to following the examples on this page:

http://www.boost.org/doc/libs/1_40_0/libs/exception/doc/motivation.html

The minute I try the following li

Answer 1

try:

#include <boost/exception/error_info.hpp>
#include <errno.h>

throw file_read_error() << boost::errinfo_errno(errno);

even better:

BOOST_THROW_EXCEPTION(file_read_error() << errinfo_errno(errno));

Your HRESULTErrorInfo example seems correct.

Answer 2

Sam Miller gave me a clue as to what the problem was. I just needed to include:

#include <boost/exception/all.hpp>

Thanks for your answers.

Answer 3

#include <boost/exception/all.hpp>

#include <boost/throw_exception.hpp>

#include <iostream>
#include <stdexcept>
#include <string>

typedef boost::error_info<struct my_tag,std::string> my_tag_error_info;

int
main()
{
    try {
        boost::throw_exception(
                boost::enable_error_info( std::runtime_error( "some error" ) ) 
                << my_tag_error_info("my extra info")
                );
    } catch ( const std::exception& e ) {
        std::cerr << e.what() << std::endl;
        if ( std::string const * extra  = boost::get_error_info<my_tag_error_info>(e) ) {
            std::cout << *extra << std::endl;
        }
    }
}

produces

samm@macmini> ./a.out 
some error
my extra info