[fpc-pascal]runtime 201 with swapword function

[James Mills]

On Fri, Jul 25, 2003 at 04:21:36PM +0200, Jonas Maebe wrote:
> 
> On vrijdag, jul 25, 2003, at 16:22 Europe/Brussels, James Mills wrote:
> 
> >Why does the following result in a runtime error ?
> >
> >program example;
> >
> >const
> >	THE_PORT = 9999;
> >
> >function swapWord(w: Word): Word;
> >begin
> >	swapWord := (w SHL 8) OR (w SHR 8);
> >end;
> 
> In Pascal, all calculations are performed using the base type (which is 
> longint in FPC), so if w > 255, then w shl 8 > high(word) and will 
> result in a range check error when assigning to swapWord. Even if we 
> calculated everything using words, you'd still get an overflow error, 
> this time when doing the shl.

How can I correct this ?
This bit of code was taken directly from server.pp in one of the old
2002 mailing threads...

cheers
James

> 
> 
> Jonas
> 
> 
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