Re: [Boost-users] [serialization] Object reference tracking on instances bug?

7 Feb 2017

      The code that it's actually contained in is pretty complex, I'll try and
put together a minimal example that produces the behavior if I need to.  It
doesn't seem to do object reference tracking on the initial
serialization/deserialization, but after I have deserialized the class from
XML and then serialized it again it does.

It does serialize the first reference to the object correctly, but later
objects just use the object_id_reference if they were similar to the first
one (even if they contain different data!).  So the first color is
serialized correctly.

The faulty behavior is in that the objects are 1) not references or
pointers, but local instance variables so should not be tracked, 2) contain
unique data and should not be referenced to other objects even if they were
pointers, and 3) do not unserialize correctly, instead resulting in objects
with default values.

Does boost keep a global table of reference tracking values that does not
get reset between serializations? That would possibly explain the problem.

MyColorsObject is an object that contains an array of colors, trying to
give a minimal example.

Expected XML output is something like this:

               <colorsArray>
                    <v>
                        <count>2</count>
                        1
                        <item id="_1">
                            <name>cyan</name>
                            <r>0</r>
                            <g>255</g>
                            <b>255</b>
                            <a>255</a>
                        </item>
                        <item id="_2">
                            <name>magenta</name>
                            <r>255</r>
                            <g>0</g>
                            <b>127</b>
                            <a>255</a>
                        </item>
                    </v>
                </colorsArray>

Actual XML output is something like

               <colorsArray>
                    <v>
                        <count>2</count>
                        1
                        <item>

                        </item>
                        <item>

                        </item>
                    </v>
                </colorsArray>

and looking at the data after deserializing the objects look like:

colorsArray.at(0).name == "";
colorsArray.at(0).r == 0;
colorsArray.at(0).g == 0;
colorsArray.at(0).b == 0;

as they are not being initialized "properly" from the serialized references.

Message: 3
...
Date: Fri, 3 Feb 2017 19:46:26 +0100
From: Raoul Wols 
To: boost-users@lists.boost.org
Subject: Re: [Boost-users] [serialization] Object reference tracking
        on      instances bug?
Message-ID: <0B210433-FF37-47FC-8812-C0428B99E0B2@primef.actor>
Content-Type: text/plain; charset="us-ascii"
Can you give an example of the expected XML output and the actual XML
output?
What is MyColorsObject?
Can you provide a complete minimal example?
--Raoul
...
Op 3 feb. 2017 om 17:27 heeft Robert P  het
volgende geschreven:
In my serialize function I am exporting a class which is a template
wrapper around std:vector.
template <typename E>
class MyArray
{
public:
    vector<E> array;
    ...
template <typename Archive>
    void MyArray::serialize(Archive & ar, const unsigned int version)
    {
        ar & BOOST_SERIALIZATION_NVP(array);
    }
}
When I add unique class instance variables to this array and then
serialize it to XML...
...
MyArray<Color> colorsArray;
Color a;
a.name = "one";
colorsArray.add(a);
Color b;
b.name = "two";
colorsArray.add(b);
...
template <typename Archive>
void MyColorsObject::serialize(Archive & ar, const unsigned int version)
{
    ar & BOOST_SERIALIZATION_NVP(colorsArray);
}
Sometimes the XML comes out using object_id_reference instead of the
unique values, and this then gets improperly unserialized with incorrect
values, i.e. both colors will have "one" as the name.
I was able to disable object tracking and it works now, but I don't
think it should be doing object reference tracking on instance variables.
Is it because of the template wrapper around vector?
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