Re: [Boost-bugs] [Boost C++ Libraries] #11731: iostreams classes do not support C++11 move semantics

Subject: Re: [Boost-bugs] [Boost C++ Libraries] #11731: iostreams classes do not support C++11 move semantics
From: Boost C++ Libraries (noreply_at_[hidden])
Date: 2017-01-26 06:10:42

#11731: iostreams classes do not support C++11 move semantics
-------------------------------------+-----------------------
  Reporter:  Josh Chia <joshchia@…>  |      Owner:  turkanis
      Type:  Bugs                    |     Status:  new
 Milestone:  To Be Determined        |  Component:  iostreams
   Version:  Boost 1.57.0            |   Severity:  Problem
Resolution:                          |   Keywords:
-------------------------------------+-----------------------

Comment (by ki.stfu@…):

 Hi!

 I faced with the same problem when I tried to move
 `boost::iostreams::stream<>`. Here is my app:
 {{{
 #include <cassert>
 #include <iostream>
 #include <fstream>
 #include <boost/iostreams/stream.hpp>

 class MyDevice {
  public:
   typedef char char_type;
   typedef boost::iostreams::sink_tag category;

   explicit MyDevice(int i) { assert(i == 1); }

   std::streamsize write(const char_type* s, std::streamsize n)
   {
     std::cout << s << '\n';
     return n;
   }
 };

 boost::iostreams::stream<MyDevice> make_stream(int i) {
   return boost::iostreams::stream<MyDevice> (i); // ERROR
 }

 std::ofstream make_ofstream() {
  return std::ofstream ("test.txt", std::ofstream::out);
 }

 int main() {
   auto&& strm = make_stream(1); // ERROR
   strm << "12312313";

   boost::iostreams::stream<MyDevice> strm2(1); // OK
   strm2 << "12312313";

   make_ofstream() << " asdfasdf"; // OK for clang++-3.8 with
 -stdlib=libc++

   return 0;
 }
 }}}

 I found couple classes that prevent compiler from implicitly-declaring
 move constructors. These classes have user-declared copy
 constructor/destructor and because of this reason we have to implement
 move operators by ourselves.
 {{{
 diff --git a/include/boost/iostreams/detail/buffer.hpp
 b/include/boost/iostreams/detail/buffer.hpp
 index 72400f0..5174253 100644
 --- a/include/boost/iostreams/detail/buffer.hpp
 +++ b/include/boost/iostreams/detail/buffer.hpp
 @@ -46,6 +46,7 @@ private:
  public:
      basic_buffer();
      basic_buffer(std::streamsize buffer_size);
 +    basic_buffer(basic_buffer&&) { /* TODO implement move ctor and assign
 op */ }
      ~basic_buffer();
      void resize(std::streamsize buffer_size);
      Ch* begin() const { return buf_; }
 diff --git a/include/boost/iostreams/detail/optional.hpp
 b/include/boost/iostreams/detail/optional.hpp
 index 867dfbd..5067a97 100644
 --- a/include/boost/iostreams/detail/optional.hpp
 +++ b/include/boost/iostreams/detail/optional.hpp
 @@ -49,6 +49,7 @@ public:
      typedef T element_type;
      optional() : initialized_(false) { }
      optional(const T& t) : initialized_(false) { reset(t); }
 +    optional(optional&&) { /* TODO implement move ctor and assign op */ }
      ~optional() { reset(); }
      T& operator*()
      {
 diff --git a/include/boost/iostreams/stream_buffer.hpp
 b/include/boost/iostreams/stream_buffer.hpp
 index dbcb786..f9e54b7 100644
 --- a/include/boost/iostreams/stream_buffer.hpp
 +++ b/include/boost/iostreams/stream_buffer.hpp
 @@ -84,6 +84,7 @@ public:
      BOOST_IOSTREAMS_STREAMBUF_TYPEDEFS(Tr)
  public:
      stream_buffer() { }
 +    stream_buffer(stream_buffer&& that) { /* TODO implement move ctor and
 assign op */ }
      ~stream_buffer()
      {
          try {
 }}}

 Can anyone look into this issue?

-- 
Ticket URL: <https://svn.boost.org/trac/boost/ticket/11731#comment:1>
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