Don't use _FPOSOFF on VC++14 on up.

Author: eldiener

include/boost/iostreams/detail/config/fpos.hpp

@@ -22,10 +22,19 @@
 # pragma once
 #endif
 
+#include <boost/config.hpp>
+
 # if (defined(_YVALS) || defined(_CPPLIB_VER)) && !defined(__SGI_STL_PORT) && \
      !defined(_STLPORT_VERSION) && !defined(__QNX__)
      /**/
 #  define BOOST_IOSTREAMS_HAS_DINKUMWARE_FPOS
+
+#if defined(BOOST_MSVC) && BOOST_MSVC >= 1900
+#define BOOST_IOSTREAMS_FPOSOFF(fp) ((long long)(fp))
+#else
+#define BOOST_IOSTREAMS_FPOSOFF(fp) _FPOSOFF(fp)
+#endif
+
 # endif
 
 #endif // #ifndef BOOST_IOSTREAMS_DETAIL_CONFIG_FPOS_HPP_INCLUDED

include/boost/iostreams/positioning.hpp

@@ -75,7 +75,7 @@ inline stream_offset position_to_offset(std::streampos pos) { return pos; }
 // Dinkumware version. The value of _Myoff cannot be extracted directly, but can
 // be calculated as the difference between the result of converting the 
 // std::fpos to a std::streamoff and the result of converting the member _Fpos
-// to a long. The latter operation is accomplished with the macro _FPOSOFF, 
+// to a long. The latter operation is accomplished with the macro BOOST_IOSTREAMS_FPOSOFF,
 // which works correctly on platforms where std::fpos_t is an integral type and 
 // platforms where it is a struct
 
@@ -85,7 +85,7 @@ inline stream_offset fpos_t_to_offset(std::fpos_t pos)
 #  if defined(_POSIX_) || (_INTEGRAL_MAX_BITS >= 64) || defined(__IBMCPP__)
     return pos;
 #  else
-    return _FPOSOFF(pos);
+    return BOOST_IOSTREAMS_FPOSOFF(pos);
 #  endif
 }
 
@@ -104,7 +104,7 @@ inline stream_offset position_to_offset(std::streampos pos)
     return fpos_t_to_offset(streampos_to_fpos_t(pos)) +
         static_cast<stream_offset>(
             static_cast<std::streamoff>(pos) -
-            _FPOSOFF(streampos_to_fpos_t(pos))
+            BOOST_IOSTREAMS_FPOSOFF(streampos_to_fpos_t(pos))
         );
 }