Re: Missing default in switch

[David R Tribble <david at tribble dot com>]

T.E.Dickey wrote:
> 
> In comp.std.c David R Tribble <david@tribble.com> wrote:
> 
>> Some compilers (and some lint programs) allow you to add a special
>> comment where the missing default goes to indicate that the default
>> case is omitted on purpose.
> 
> otoh, if you _do_ supply a 'default:', then some compilers will
> generate more compact code (in addition to not warning about the
> missing case).
> 
> -- that's probably better than a comment...

I agree.  I usually supply a default, even if all it does is a break.

But I don't see how that can lead to more optimized code.  What's the
difference in the code generated for [A] and [B] in:

    /* [A] */
    switch (c)
    {
    case 1:
        stmt1;
    case 2:
        stmt2;
    case 3:
        stmt3;
    }

    /* [B] */
    switch (c)
    {
    case 1:
        stmt1;
    case 2:
        stmt2;
    case 3:
        stmt3;
    default:
        break;
    }

I can't see how the code would be any different after optimization.

-- David R. Tribble, david@tribble.com, http://www.david.tribble.com --