Re: [Boost-users] [serialization]

From: David Abrahams (dave_at_[hidden])
Date: 2005-11-10 11:18:27

Nigel Rantor <wiggly_at_[hidden]> writes:

> Robert Ramey wrote:
>> Paul Giaccone wrote:
>> 
>>>For booleans, though, a value of other than 0 or 1 means it has not
>>>been initialised, and perhaps this should throw an exception on
>>>writing to the archive rather than on reading from it.
>> 
>> 
>> Hmmm, I'm not sure about this.  Do we know for a fact that a bool
>> variable will always contain 1 or 0?  I've never seen code trap on
>> an un-initialized bool.  It seems that even an uninitialized bool
>> corresponds to true or false.
>
> No, bools won't always contain 1 or 0, like other types their value is 
> be undefined if they have not been initialised, depending upon where 
> they have been declared.

An uninitialized bool doesn't have a value you can read without
causing undefined behavior.  So for all intents and purposes it
doesn't have a value.  

> <caveat>
> C++ isn't my day job...I just use it for fun things...
> </caveat>
>
> When bools are used in logical operations they are converted to 
> integers

Can you cite the standard on that one?  I'm pretty sure that it's the
other way around: when integers are used in logical operations they
are converted to bools.

> , so depending on what your bool happens to contain before 
> initialisation it could evaluate to either true or false.

Or it could crash your computer.

>> Perhaps part of the problem is that I used 0 and 1 for bool variable
>> in order to not included english strings "true" and "false" in text files
>> and to save space.
>> 
>> I'll think about this.
>
> My two proposals would be the one that encourages pragmatism and the 
> other that encourages correctness.
>
> Pragmatic:
>
> Well, how about simply treating anything other than 1 as false? 

I don't know what 1 has to do with anything.  The values of a bool
are true and false.  1 is an int.

-- 
Dave Abrahams
Boost Consulting
www.boost-consulting.com