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On Fri, 25 May 2007, Ton Sieverding wrote:
> Can you please explain me why 'switch statements are a frequent
> source of bugs' ? If the last CASE is a DEFAULT then all possible
> cases are covered. Or am I missing something in the AFL SWITCH
> statement ?
>
> switch ( expression )
> {
> case constant-expression1 : statement;
> case constant-expression2 : statement;
> ...
> case constant-expressionN : statement;
>
> default : statement;
>
> }
>
>
> Ton.
The 'standard' error when using a switch statement in 'C' and presumably
AFL, is forgetting to put 'break;' statements in.
To paraphrase your example (above) so it looks like this:-
switch ( expression )
{
case constant-expression1 : statement1;
case constant-expression2 : statement2;
...
case constant-expressionN : statementN;
default : statement_default;
}
If you leave out the break statements, and
expression==constant_expression1 you will execute statement1 (what you
wanted) AND ALSO statement2 AND ALSO statement3 AND ALSO ... statementN
AND ALSO statement_default.
It's sometimes called the 'fall-through' bug. It's easy to miss, can be
a right pain!
--
Nigel Rowe
rho \N{COMMERCIAL AT} swiftdsl \N{FULL STOP} com \N{FULL STOP} au
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