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

Subject: Re: [Boost-users] [serialization] Object reference tracking on instances bug?
From: Robert Ramey (ramey_at_[hidden])
Date: 2017-02-07 17:00:46

On 2/7/17 4:20 AM, Robert P wrote:

> 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.

The serialization library does not track object contents, only their 
addresses.

>         I was able to disable object tracking and it works now,

This is the correct solution

>         don't think it should be doing object reference tracking on
>         instance variables.
I think if you spent more time considering this this, you'd change your 
opinion.

Is it because of the template wrapper
>         around vector?
Not relevant

The question is really about what it means to serialize something on the 
stack.  Something like

MyT my_object;

...

// serialize/deserialize my object

Is going to be fine.

But something like

...
for(...)
    MyT my_object;
    ...
    // serialize/deserialize my_object

or worse
MyT::serialize(ar, version) const {
    x = f(*this)
    ar & x;
}

is going to be asking for trouble as we're reusing the same address.  As 
you've discovered. the library provides a work around for this.  But 
when confronted with the need to use it, it should be seen and an 
opportunity to step back and ask oneself: "Is this really what I want to 
do?  Why am I saving the state of something that is changing?"

Robert Ramey