[Boost-users] [exception] nested exceptions: lost information?

Subject: [Boost-users] [exception] nested exceptions: lost information?
From: Pascal Z. (pascal_at_[hidden])
Date: 2009-09-23 11:13:06

Hello

I'm trying to nest exceptions using boost.Exception, but it seems like 
some information (in this case the message returned via what() ) is lost 
on the way.

#include <iostream>
#include <boost/exception.hpp>

typedef boost::error_info<struct tag_nested_exception, 
boost::exception_ptr> nested_exception;

struct file_open_error : public boost::exception, public std::exception {};

int open_file(const std::string& filename) {
         try {
                 // ...
                 throw std::runtime_error("Some internal error.");
         } catch(const std::exception& error) {
                 throw file_open_error() << 
nested_exception(boost::copy_exception(error));
         }
}

int main(int argc, char* argv[]) {
         try {
                 int file = open_file("foo.txt");
                 file++;

         } catch(const boost::exception& error) {
                 try {
 
boost::rethrow_exception(*boost::get_error_info<nested_exception>(error));
                 } catch(const std::exception& nested) {
                         std::cout << "the nested error is: " << 
nested.what() << std::endl;
                 }
         }
         return 0;
}

I except the output to be "the nested error is: Some internal error." 
but it outputs "the nested error is: std::exception".
What can I do to make it work?

Greetings
Pascal