id	summary	reporter	owner	description	type	status	milestone	component	version	severity	resolution	keywords	cc
6775	"boost::filesystem::path cannot be created from lexical_cast("""")"	Ulrik Mikaelsson <ulrik.mikaelsson@…>	Beman Dawes	"The boost {{{filesystem::path}}} can hold an ""empty"" state, where {{{.string()}}} returns {{{""""}}}. It even has a designated check for this state, {{{empty()}}} This state is useful as a kind of null-value, to turn on or off certain behavior.

However, this state cannot be reached through {{{lexical_cast}}}, the following code will for example end with a {{{boost::bad_lexical_cast}}} error.

{{{
#include <boost/lexical_cast.hpp>
#include <boost/filesystem/path.hpp>
#include <string>

int main() {
  boost::filesystem::path str = boost::lexical_cast<boost::filesystem::path, std::string>("""");
  return 0;
}
}}}

IMO, this is a bug. {{{path}}} clearly has a normal and useful {{{empty()}}} state, which cannot for some reason be reached through {{{lexical_cast}}}. The equivalent test works for {{{std::string}}}, for example, so should not be inherent problem with {{{lexical_cast}}} itself.

One consequence is that {{{path}}} cannot be used as a value-type for {{{program_options}}}, while allowing options with default-values to be turned of using empty values. (I.E. {{{--config-file """"}}})"	Bugs	new	To Be Determined	filesystem	Boost 1.48.0	Problem