Serialization of multi_index_container is non portable.

[Ilia V. Sochenkov <ivsochenkov@…>]

multi_index_container save and load member-functions use type "std::size_t" to serialize a container's size instead of boost::serialization::collection_size_type. It may cause some problems when portable binary archives are used, because std::size_t has different size in different platforms. boost::serialization::collection_size_type can be treated specially by portable archive implementations: collection_size_type used in the serialization implementation for the standart containers.

[Joaquín M López Muñoz]

(In [55994]) fixed #3365

[Joaquín M López Muñoz]

Ilia, just fixed the problem in changeset

​https://svn.boost.org/trac/boost/changeset/55994

I'd appreciate if you could check everything's OK on your side.

[Hajo Kirchhoff <mailinglists@…>]

The changeset may fix this problem (haven't checked), but line 667 (of this changeset) might cause data truncation under x64 bit and a compiler warning.

    serialization::collection_size_type       s;
    detail::serialization_version<value_type> value_version;
    if(version<1){
      std::size_t sz;
      ar>>serialization::make_nvp("count",sz);
      s=sz;  /***** Error here *****/
    }

With x64 bit compilation (Visual Studio 2008, boost 1.44) collection_size_type is unsigned int (32 Bit), whereas size_t is an unsigned long (64 Bit). The assignment s=sz gets truncated and issues a warning

boost\boost/multi_index_container.hpp(673) : error C4267: 'argument' : conversion from 'size_t' to 'const unsigned int', possible loss of data

Since our project treats this warning as an error, the code does not compile.

The patch here is straightforward: simply cast the result. There is nothing we can do in this case anyway and also it is pretty unlikely that any user in the world will serialise more than 2^{32 items.}

@@ -670,7 +670,7 @@
     if(version<1){
       std::size_t sz;
       ar>>serialization::make_nvp("count",sz);
-      s=sz;
+      s=(serialization::collection_size_type)sz;
     }
     else{
       ar>>serialization::make_nvp("count",s);

[Joaquín M López Muñoz]

Hi Hajo,

Please check whether

​https://svn.boost.org/trac/boost/changeset/75643

solves the issue. Thank you!

[Hajo Kirchhoff <mailinglists@…>]

Hi Joaquin, yes, that should solve the issue. Thanks. And thanks for your work :-) (fixed in 1.49) You can close this ticket again...