Re: [Boost-users] [multi_index] Serialization problem withmulti_indexcontainer

From: Joaquín Mª López Muñoz (joaquin_at_[hidden])
Date: 2006-04-03 10:56:28

John Reid ha escrito:

> Hi,
>
> I had some problems serializing/deserializing a multi_index container.
> I've tried a work around of copying the container into a vector and
> serializing/deserializing this (which works). Does anyone know the
> conditions under which serialization of multi_index containers do not
> work? My guess is my operator< may not satisfy the requirements although
> it has stood up to all the testing I have been able to do so far.
>
> I am using VS2005 with boost 1_33_1.
>
> FYI I'm getting an archive exception from this code in ordered_index.hpp:
>    void rearranger(node_type* position,node_type *x)
>    {

[...]

>    }

Hello John, from your description looks like loading is failing because
your operator< is not *serialization-compatible*, as required in

http://www.boost.org/libs/multi_index/doc/reference/ord_indices.html#serialization

Serialization-compatibility formal definition is given at:

http://boost.org/libs/multi_index/doc/reference/multi_index_container.html#serialization

What this means is, if you've got elements a,b and its corresponding
deserialized equivalents a',b', then a<b must yield the same value
(true or false) as a'<b' --assuming it is operator< that is used for sorting
the index, which is the case if identity<element> is the key and
the default sorting criterion is used.

You can very easily spot the place where serialization-compatibility
of operator< is determined to not hold by placing a breakpoint where
the exception is thrown (line 1083 of ordered_index.hpp) and inspecting
the values of arguments position and x. Please report your findings back
or insist on me if you need further help. Good luck,

Joaquín M López Muñoz
Telefónica, Investigación y Desarrollo