Is this a bug? +goto

[Jonathan M Davis]

On Wednesday, November 7, 2018 1:03:47 PM MST Michelle Long via Digitalmars-
d-learn wrote:
> Don't let their psychobabble fool you. They are wrong and you
> were right from the start.

...

> Case A:
> {
>     if (true) goto X;
>     int x;
> }
> X:
>
>
> Case B:
> {
>     if (true) goto X;
>     {
>        int x;
>     }
> }
> X:
>
>
> These two cases are EXACTLY the same semantically. It's like
> writing A + B and (A + B).

That's not the situation that the OP was describing. If adding braces in a
situation where the braces have no semantic effect has any impact on goto,
then it's a compiler bug. It's adding a new scope that affects the lifetime
of a variable whose declaration is being jumped over by a goto that matters.

I know that you're frustrated, because you've hit a problem with goto in
complex code, and you don't have a simple example that shows the compiler
bug, but the approach that D takes with goto (and any construct that
potentially requires code flow analysis) of avoiding requiring that the
compiler be smart is precisely to reduce the risk of there being cases where
the compiler is going to screw it up in complex code even though it gets it
right in the simple cases. If the language required the compiler to be smart
about such things, we'd have a lot more problems with subtle, hard to track
down compiler bugs in complex code. So, we'd just have _more_ cases where
people would be hitting frustrating bugs like you are.

Regardless, if you want to actually have your problem fixed, you're going to
need to provide a reproducible test case in a bugzilla report, even if it's
large, otherwise no one is going to be able to track it down for you.

Now, a goto-related regression has recently been reported for joiner:

https://issues.dlang.org/show_bug.cgi?id=19213

where some code worked with joiner in 2.081.2 but does not work with 2.082.0
or later, so you may want to test your code with an older compiler release
to see if you've hit a compiler regression. If so, that could be a starting
point for tracking down the problem.

- Jonathan M Davis