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

Subject: Re: [Boost-users] [exception] nested exceptions: lost information?
From: Pascal Z. (pascal_at_[hidden])
Date: 2009-09-26 13:27:49

Emil Dotchevski schrieb:
> By design, boost::copy_exception slices. Its intended use is to obtain
> an exception_ptr without throwing an exception, as in:
> 
> exception_ptr p=copy_exception(foo());
> 
> (the result being that rethrow_exception(p) will throw foo.)
> 
> To copy the current exception in a catch, use
> 
> catch(...)
> {
>   exception_ptr p=current_exception();
> }
> 
> Emil Dotchevski
> Reverge Studios, Inc.
> http://www.revergestudios.com/reblog/index.php?n=ReCode
> 
> On Wed, Sep 23, 2009 at 8:13 AM, Pascal Z. <pascal_at_[hidden]> wrote:
>> 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
>>
>> _______________________________________________
>> Boost-users mailing list
>> Boost-users_at_[hidden]
>> http://lists.boost.org/mailman/listinfo.cgi/boost-users

Thanks, it's working now. =)