Fix #10354 from Juan Alday. As he pointed out, the declaration (in detail/utf8_codecvt_facet.hpp) and definition (in detail/utf8_codecvt_facet.ipp) need to use the same signature. Reapply Marshall Clow's [SVN r81616] and [SVN r81877] from November and December, 2012, as these appear to correctly supply const for the msvc/dinkumware library (since fixed) that used a do_length() first argument. Revert the portion of [SVN r86722] that removed BOOST_CODECVT_DO_LENGTH_CONST from the do_length() signature in utf8_codecvt_facet.ipp so that it stays in sync with utf8_codecvt_facet.hpp. For the same reason, copy the __IBMCPP__ workaround from utf8_codecvt_facet.ipp to utf8_codecvt_facet.hpp. Verified all libraries (filesystem, log, program_options, property_tree, serialization) that use utf8_codecvt_facet passed all tests before, and then after, these changes. Also applied minor edits to the use comments embedded in utf8_codecvt_facet.hpp.

include/boost/detail/utf8_codecvt_facet.hpp

@@ -14,7 +14,7 @@
 /////////1/////////2/////////3/////////4/////////5/////////6/////////7/////////8
 // utf8_codecvt_facet.hpp
 
-// This header defines class utf8_codecvt_facet, derived fro 
+// This header defines class utf8_codecvt_facet, derived from 
 // std::codecvt<wchar_t, char>, which can be used to convert utf8 data in
 // files into wchar_t strings in the application.
 //
@@ -28,12 +28,13 @@
 //   This seems inconvenient, and asking a user to link to an unrevieved 
 //   library is strange. 
 // Until the above points are fixed, a library which wants to use utf8 must:
-// - include this header from one of it's headers or sources
-// - include the corresponding .cpp file from one of the sources
+// - include this header in one of it's headers or sources
+// - include the corresponding boost/detail/utf8_codecvt_facet.ipp file in one
+//   of its sources
 // - before including either file, the library must define
 //   - BOOST_UTF8_BEGIN_NAMESPACE to the namespace declaration that must be used
 //   - BOOST_UTF8_END_NAMESPACE to the code to close the previous namespace
-//   - declaration.
+//     declaration.
 //   - BOOST_UTF8_DECL -- to the code which must be used for all 'exportable'
 //     symbols.
 //
@@ -42,7 +43,7 @@
 //             namespace boost { namespace program_options {
 //    #define BOOST_UTF8_END_NAMESPACE }}
 //    #define BOOST_UTF8_DECL BOOST_PROGRAM_OPTIONS_DECL
-//    #include "../../detail/utf8/utf8_codecvt.cpp"
+//    #include <boost/detail/utf8_codecvt_facet.ipp>
 //
 // Essentially, each library will have its own copy of utf8 code, in
 // different namespaces. 
@@ -92,7 +93,7 @@ namespace std {
 }
 #endif
 
-#if !defined(__MSL_CPP__) && !defined(__LIBCOMO__)
+#if defined(_CPPLIB_VER) && (_CPPLIB_VER < 540)
     #define BOOST_CODECVT_DO_LENGTH_CONST const
 #else
     #define BOOST_CODECVT_DO_LENGTH_CONST
@@ -103,6 +104,14 @@ namespace std {
 
 BOOST_UTF8_BEGIN_NAMESPACE
 
+//----------------------------------------------------------------------------//
+//                                                                            //
+//                          utf8_codecvt_facet                                //
+//                                                                            //
+//            See utf8_codecvt_facet.ipp for the implementation.              //
+//----------------------------------------------------------------------------//
+
+
 struct BOOST_UTF8_DECL utf8_codecvt_facet :
     public std::codecvt<wchar_t, char, std::mbstate_t>  
 {
@@ -178,7 +187,11 @@ protected:
         const char * from,
         const char * from_end, 
         std::size_t max_limit
-    ) const;
+    ) const
+#if BOOST_WORKAROUND(__IBMCPP__, BOOST_TESTED_AT(600))
+    throw()
+#endif
+    ;
 
     // Largest possible value do_length(state,from,from_end,1) could return.
     virtual int do_max_length() const BOOST_NOEXCEPT_OR_NOTHROW {

include/boost/detail/utf8_codecvt_facet.ipp

@@ -171,7 +171,7 @@ std::codecvt_base::result utf8_codecvt_facet::do_out(
 // How many char objects can I process to get <= max_limit
 // wchar_t objects?
 int utf8_codecvt_facet::do_length(
-    const std::mbstate_t &,
+    BOOST_CODECVT_DO_LENGTH_CONST std::mbstate_t &,
     const char * from,
     const char * from_end, 
     std::size_t max_limit