[fpc-pascal]runtime 201 with swapword function
jonas at zeus.ugent.be
Fri Jul 25 16:21:36 CEST 2003
On vrijdag, jul 25, 2003, at 16:22 Europe/Brussels, James Mills wrote:
> Why does the following result in a runtime error ?
> program example;
> THE_PORT = 9999;
> function swapWord(w: Word): Word;
> swapWord := (w SHL 8) OR (w SHR 8);
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.
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