Re: [Boost-users] [serialization]

From: Kevin Wheatley (hxpro_at_[hidden])
Date: 2005-11-14 07:59:03

Daryle Walker wrote:
> 4.  If you're using some sort of (discrimated) union, where only some of the
> members are valid at any time, then you must serialize only the currently
> active ones.  It is IRRESPONSIBLE for you to do otherwise!

As I wrote that particular bit, I'll take the heat for it ... its not
really a discriminated union, I used that as a loose desciption for
what is actually occuring, So that's not Paul's fault :-)

I think the only thing that everybody agrees on here is uninitialised
variables are bad...

I'm more interested in knowing I could do the following...

lets say I archive an object using binary archives ... everything goes
back and forth no problems, switching to text archives I'd expect the
same behaviour more or less, so ideally if the value of my unitialised
int happens to be 42, then when I get it back it should still be 42
when its read back in, this is fine, but if the value goes outside of
the range say when its not an int but a bool, then we have a problem.
The simple 1 line assert appears to detect the condition that occurs
on read back, which is that the serialization library cannot read back
things it *successfully wrote* as far as the calling code is able to
detect.

It chooses to write a bool in the form of "0" or "1", so if it writes
"205" (the value we actually found when we inspected our text archive)
we could see it wasn't a valid value and quickly fixed our code's
problem, it would have been nicer, in this case, if could have spotted
that the archive althought appearing to have been written without
error, was in fact 'corrupt'. My approach to this would be a data
paranoia mode which verifies the conversion will convert back on
loading that doesn't trigger an assert, but throws an exception, but
clearly thats more work than an assert in this case.

Which ever way we no longer have the problem

Kevin - I am not a number, I am a free NaN...

-- 
| Kevin Wheatley, Cinesite (Europe) Ltd | Nobody thinks this      |
| Senior Technology                     | My employer for certain |
| And Network Systems Architect         | Not even myself         |