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Subject: Re: [boost] [Serialization] Bizarre bug
From: Jarl Lindrud (jarl.lindrud_at_[hidden])
Date: 2009-08-07 10:23:18

Robert Ramey <ramey <at>> writes:

> I'm still intrigued as to how such a situation could come up where
> something is saved through a pointer but in another program it isn't.
> I looked at the above link and didn't find this. Basically, my view
> is that anyone tripped up by this error can't be writing anything
> that makes sense anyway. I'm looking for a counter example to
> this.
> Robert Ramey

I don't know this arose originally - there may well have been a situation where
the vector<char> was serialized through a pointer in one program, and
deserialized as a value, in another program. That is indeed an error, although
in this case it does not seem that any exception was thrown to signify the
error (the vector just silently failed to deserialize properly).

On a more fundamental level, I don't understand how this code can *ever* fail:

    std::ostringstream ostr;
    boost::archive::text_oarchive(ostr) & v0;

    std::istringstream istr(ostr.str());
    boost::archive::text_iarchive(istr) & v1;
    bool ok = (v0 == v1);

Here the vector is serialized and deserialized as a value. How is it that
"tracking" or "implementation" settings for a particular type can be affected
by the mere presence of this code

    ar << pVec; // pVec is a vector<char> *

, or this code

    ar >> pVec; // pVec is a vector<char> *

, in a completely different part of the program?

Snippet (2), if it appears in a program without snippet (3) also occurring,
makes the program incorrect, if I understand you correctly. But how is it that
its mere compile-time presence causes the technically correct code in (1) to

And even if snippet (3) is also present somewhere in the program, thus making
the program correct in your view, IIUC the archives produced in (1) will then
have a different format than those produced, when snippets (2) and (3) were
absent. That would imply that archive formats can change silently, through mere
addition of source code, anywhere else in the program. And the format change
wouldn't be noticed until some *other* program tries to read the archives and
fails to do so. Have I understood that correctly?


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