how to convert string to unsigned short using boost lexical cast?

Question

I have a string containing the port, when I try to create a tcp endpoint I need its value in unsigned short

  std::string to_port;
    ....
    boost::lexical_cast<unsigned short>(to_port));

throws an exception bad lexical cast: source type value could not be interpreted as target

Answer 1

The following program works correctly:

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

int main(int argc, const char *argv[])
{
    std::string to_port("8004");
    unsigned short intport = boost::lexical_cast<unsigned short>(to_port);

    std::cout << intport << std::endl;
    std::cout << std::hex << intport << std::endl;
    return 0;
}

But if we modify the first line of main into:

std::string to_port;

We get the exception:

terminate called after throwing an instance of 'boost::exception_detail::clone_impl<boost::exception_detail::error_info_injector<boost::bad_lexical_cast> >'
  what():  bad lexical cast: source type value could not be interpreted as target
Aborted (core dumped)

Which leads to the conclusion that there's something wrong with the parameter you are passing to the lexical_cast.

Can you print the to_port variable to verify its content just before the lexical_cast? Are you sure it is properly initialized and still in-scope when used (e.g., no temporaries involved, no dangling pointers)?