Re: Goto skipping declarations
On 04/05/2024 8:38 AM, Jonathan M Davis wrote: In any case, I expect that the compiler is just going dumb here because of the label for some reason, and one or more of the checks that it's supposed to be doing is being missed. It is very simple code. A reverse search over the double linked list for the goto from the label. I looked into it fairly recently as an example of type state analysis D is already designed against.
Re: Goto skipping declarations
On Friday, 3 May 2024 at 20:38:31 UTC, Jonathan M Davis wrote: https://issues.dlang.org/show_bug.cgi?id=24535
Re: Goto skipping declarations
On Friday, May 3, 2024 2:38:31 PM MDT Jonathan M Davis via Digitalmars-d-learn
wrote:
> On Friday, May 3, 2024 1:15:16 PM MDT Ben Jones via Digitalmars-d-learn
wrote:
> > In general, you can't skip a declaration with goto, but it seems
> > to be allowed if the declaration you're skipping is labelled...
> > Is that expected or an accepts invalid bug?
> >
> > https://godbolt.org/z/4qx8Pf6G7
> >
> > ```d
> > void f1(){ //fails with error about skipping a declaration
> >
> > int x;
> > goto Label;
> > int y;
> > Label:
> > int z;
> >
> > }
> >
> > void f2(){ //compiles fine
> >
> > int x;
> > goto Label;
> > Dummy:
> > int y;
> > Label:
> > int z;
> >
> > }
> > ```
>
> It has to be a bug, and taking it a step further shows that. If you print
> out y, you'll get a seemingly random number. E.G. On the first run, I got
>
> 554440803
>
> and on the second I got
>
> 549310547
>
> Presumably, it's a garbage value from whatever happened to be on the stack.
>
> I'm quite sure that the spec doesn't have anything about being allowed to
> skip a declaration just because it has a label on it (honestly, if we _did_
> want that to be the case, the spec would probably be missing it, since it
> tends to fall on the side of having too few details rather than too many),
> but even if it did, the code is clearly doing something that should not be
> happening with initialization without explicitly using = void. So,
> _something_ here would nee to be fixed.
>
> In any case, I expect that the compiler is just going dumb here because of
> the label for some reason, and one or more of the checks that it's supposed
> to be doing is being missed.
Here. I reported it:
https://issues.dlang.org/show_bug.cgi?id=24534
- Jonathan M Davis
Re: Goto skipping declarations
On Friday, May 3, 2024 1:15:16 PM MDT Ben Jones via Digitalmars-d-learn wrote:
> In general, you can't skip a declaration with goto, but it seems
> to be allowed if the declaration you're skipping is labelled...
> Is that expected or an accepts invalid bug?
>
> https://godbolt.org/z/4qx8Pf6G7
>
> ```d
> void f1(){ //fails with error about skipping a declaration
> int x;
> goto Label;
> int y;
> Label:
> int z;
> }
>
> void f2(){ //compiles fine
> int x;
> goto Label;
> Dummy:
> int y;
> Label:
> int z;
> }
> ```
It has to be a bug, and taking it a step further shows that. If you print
out y, you'll get a seemingly random number. E.G. On the first run, I got
554440803
and on the second I got
549310547
Presumably, it's a garbage value from whatever happened to be on the stack.
I'm quite sure that the spec doesn't have anything about being allowed to
skip a declaration just because it has a label on it (honestly, if we _did_
want that to be the case, the spec would probably be missing it, since it
tends to fall on the side of having too few details rather than too many),
but even if it did, the code is clearly doing something that should not be
happening with initialization without explicitly using = void. So,
_something_ here would nee to be fixed.
In any case, I expect that the compiler is just going dumb here because of
the label for some reason, and one or more of the checks that it's supposed
to be doing is being missed.
- Jonathan M Davis
Goto skipping declarations
In general, you can't skip a declaration with goto, but it seems
to be allowed if the declaration you're skipping is labelled...
Is that expected or an accepts invalid bug?
https://godbolt.org/z/4qx8Pf6G7
```d
void f1(){ //fails with error about skipping a declaration
int x;
goto Label;
int y;
Label:
int z;
}
void f2(){ //compiles fine
int x;
goto Label;
Dummy:
int y;
Label:
int z;
}
```
