On Mon, Sep 8, 2008 at 1:42 AM, D. Michael McIntyre
<[EMAIL PROTECTED]> wrote:
> On Sunday 07 September 2008, Julie S wrote:
>
>> These are all coded as traditional c style casts.  I don't know much about
>> c++ casting.  The problem is that Qt4 only wants qintxx and quintxx types.
>> So we have to choose one--assuming a traditional cast since the word length
>> is directly linked to the type 4 bytes or 8 bytes.

The "source" and "target" types in the cast don't have to have the
same size, but of course you do (unless you know something particular
about the data involved) have to make sure the target is at least as
big as the source.

In this case, unsigned long can be either 32 or 64 bits depending on
architecture.  On a 32-bit architecture, casting from unsigned long to
quint32 is a "natural" cast without any change of word size, so it
should be preferable (although quint64 is a suitable target as well).
On a 64-bit architecture, casting from unsigned long to quint64 is the
only sensible choice.  So the code is ambiguous.  I guess.

In this case, the target size clearly matters, and the source size is
clearly of some interest because some of the casts are to ints and
others to longs.  So there's some archaeology to be done here.

I'd like to add this particular case (streaming MappedEvent to
QDataStream) to my own task list, if that's OK.  That's partly because
it might be a subtle one, but also because I'm thinking that once DCOP
has been eliminated, we might not need these operators at all anyway.


Chris

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