[Boost-users] Cannot cast from std::string to seastar::sstring.

Subject: [Boost-users] Cannot cast from std::string to seastar::sstring.
From: José Guilherme Vanz (jvanz_at_[hidden])
Date: 2018-09-17 04:48:26

Hi guys,

I'm investigating a [bug](https://github.com/scylladb/scylla/issues/2905) in the Seastar/lexical_cast and I got stuck. Let me introduce what's going on and the further investigation that I did.
The Seastar framework uses the boost program options to parse the command line arguments. But when the user try to pass a command line argument of seastar::sstring (Seastar string type) with a white space, the lib tells us that is invalid value.

Turns out the boost program options call lexical_cast to cast from  std::string to seastar::sstring. This cast is failing. The lexical_cast uses a stream to extract the value from the source, but the operator>> stops in the white space. Making the second validation in the same [line](https://github.com/boostorg/lexical_cast/blob/boost-1.66.0/include/boost/lexical_cast/detail/converter_lexical_streams.hpp#L600) false. Note, there is a [call](https://github.com/boostorg/lexical_cast/blob/boost-1.66.0/include/boost/lexical_cast/detail/converter_lexical_streams.hpp#L597) to unsetf to ensure that the white space will be skipped: stream.unsetf(std::ios::skipws);.

What's am I trying to do is figure out  where the problems live? Is there a bug in boost or is a sstring implemantion problem? Am I missing something?

Thanks!