"Darren New" <dne### [at] sanrrcom> wrote in message 
news:4ae0c668$1@news.povray.org...
> Captain Jack wrote:
>> Wouldn't bit fields do what you're describing?
>
> Only if they're all aligned to byte boundaries, and you know what order 
> the fields are in. I.e., yes, but in no way portably. There's no way to 
> portably (for example) lay a C structure for an IP datagram header onto 
> the header and just use it.

That's true... I know the specification calls for packing the bytes as 
tightly as possible, but there's no standard spec for alignment.

I used to use Borland's Turbo C (v2, IIRC) way back when on DOS machines. I 
remember that it had custom pre-processor directives for controlling byte 
and word alignment, but I'm sure those weren't in any way standard.

I also used to make use of its "asm" keyword which would let me insert x86 
assembler code into the middle of my C code, and I'd often use that to 
squeeze some extra bits out of my memory usage. Contrast that with my 
current job, where we use .NET, and I don't even keep track of what I've 
allocated and deallocated, or how much I've used. I seem to have grown fat 
and lazy on the backs of the developers at Redmond. 8D

> I don't think C handles *any* of that. About the closest it comes is 
> volatile (sort of) and undefined behavior that *often* does what you'd 
> expect when using addresses, unless your memory model is too far different 
> from C's.

But that was what's so great about pure C... nothing lets you shoot yourself 
in the foot with confidence the way C does. <g>

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