[PLUG] Re: #define for 32 vs 64 bit C program?

[Chip Salzenberg <chip@pobox.com>]

According to Tobias DiPasquale:
> On Monday 26 April 2004 20:04, Chip Salzenberg wrote:
> | Except where it's not.
> 
> Please delineate where, in practice, sizeof( unsigned long) would not be equal 
> to the word size of the platform using an ANSI compliant C compiler.

It's entirely up to the implementor whether to make long and int the
same size, and if they're different, which of them to make the natural
word size of the machine.  These rules may not make much sense to you,
but they're all a compiler writer has to go on.  Assuming that he'll
be "reasonable" doesn't work when he reasons differently.


* The examples I know best, Intel 8088 through 80286, are seldom
remembered these days except in mockery, but the 286 had real memory
protection and was a decent platform for Unix (or, alternatively,
Xenix :-)).  I'm sure you'll agree that 16 bits was the native size
for those machines.  On these pre-386 machines:

   short = int = 16bits
   long = 32bits

Porting code written for VAXen was "fun".

BTW, pointers were all different depending on the memory model, but I
won't bore you with that.  Suffice to say that there's a *reason* why
the ANSI standard says that a function pointer type is not guaranteed
to be castable to *any* type other except another function pointer type.


* I also used several compilers for 8-bit processors; in fact, I once
retargeted a compiler from the Z-80 to the 6809.  Eight-bit compilers
typically followed the same pattern: int=short=16, long=32.


* A reader might infer from this that there wasn't a lot of difference
between an 8086 and an eight-bit processor.  He would be right.  :-P


-- 
Chip Salzenberg               - a.k.a. -               <chip@pobox.com>
"I wanted to play hopscotch with the impenetrable mystery of existence,
    but he stepped in a wormhole and had to go in early."  // MST3K
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