On Sunday 18 July 2010 00:38:38 Jonathan M Davis wrote:
> On Saturday 17 July 2010 22:52:21 strtr wrote:
> > I think I'll start subject tagging my posts: [D1/D2]
> > std.stdio in D1 doesn't mention a write function and feeding the writef
> > function an illegal UTF string will result in a UTF exception.
> > With this information, what do you think the output should be?
>
> Well, I certainly think that throwing an exception for bad UTF-8 values
> makes sense, though D2's docs for writef say nothing about exceptions, and
> on my machine, running Linux, they just fail to print anything. Throwing
> an exception would likely have been better.
>
> In any case, I would have expected it to increment stash by 2 on the first
> loop because $ would be valid and would hit both scope(exit) and
> scope(success). After that... That continue makes me awfulling nervous.
> You'd expect the scope statements to be run in reverse order with continue
> and then stash--. However, to run that continue statement would have to
> skip the other scope statements...
>
> I think that we'll have to lower the body of that foreach loop to have any
> clue what's going on here. It should come out to something like this, I
> would think:
>
> const char[] coins = `$�`;
>
> void main()
> {
> writef(`I made `);
> int stash = 0;
> scope(exit) writefln(stash,`.`);
> scope(failure) stash--;
>
> foreach(coin;coins)
> {
> try
> {
> try
> {
> try
> {
> try
> {
> writef(coin);
> }
> catch
> {
> continue;
> throw;
> }
> }
> catch
> {
> stash--;
> throw;
> }
>
> stash++;
> }
> catch
> {
> throw;
> }
> }
> finally
> {
> stash++;
> }
> }
> }
>
>
> That being the case, the exception from writef() will always get eaten by
> the continue because the throw that rethrows the exception would never
> occur. Normally, code like that should result in a compilation error, but
> it might not given that it's the compiler creating the try-catch block. My
> guess is that this is a bug in dmd. It makes no sense to me to allow any
> kind of goto, break, or continue statements in a scope statement's body.
>
> Regardless, that continue would mean that the first stash++ would be
> skipped, but the second would still happen because it's in a finally
> block. That means that each of the 3 bad UTF-8 values which make up the
> euro symbol would each increment stash once. So, the overall result would
> then be 5.
>
> It's possible that I lowered those scope statements incorrectly, but it
> looks to me like that's what the code should be doing. Regardless,
> continue in a scope statement should be an error.
>
> - Jonathan M Davis
Hmm. Well, it seems that throw by itself is not legal D. You have to do
something like
catch(Exception e)
{
throw e;
}
But in any case,
catch(Exception e)
{
continue;
throw e;
}
compiles just fine. That seems to me like it shouldn't though, since then throw
e; is an unreachable statement. In any case, I'll file a bug report on this.
- Jonathan M Davis
