Re: [boost] [serialization] use of unsigned int instead of size_type

From: David Abrahams (dave_at_[hidden])
Date: 2006-02-11 17:33:37

Kim Barrett <kab_at_[hidden]> writes:

> At 11:52 AM -0800 2/11/06, Robert Ramey wrote:
>>David Abrahams wrote:
>>  > IMO the size_type change should be considered a bugfix, as it was not
>>>  possible to portably serialize collections
>>
>>of over 4 G objects
>
> Strictly speaking, of any size. 

Right.  Unsigned int isn't required to be more than 16 bits, and there
*are* compilers where it is a 16 bit number.

> And changing the type of the count from
> "unsigned int" to std::size_t would actually be worse, in a practical
> sense. The representation size (how many bits of data will appear in the
> archive) must be the same on all platforms.
>
> sizeof(unsigned int) is commonly 4 on 32bit platforms
> sizeof(unsigned int) is (I think) commonly 4 on 64bit platforms
> sizeof(std::size_t) is commonly 4 on 32bit platforms
> sizeof(std::size_t) is commonly 8 on 64bit platforms
>
> (I'm knowingly and intentionally ignoring DSP's and the like in the above).
>
> The count should be some type that has a fixed (up to byte-order issues)
> representation, i.e. something like uint64_t.

Or a variable-length representation, which is what I *think* Matthias
chose.

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