Thanks for reporting - perhaps better for the bug tracker, and indeed we do
this (or something like it) filed already, see
https://github.com/gwtproject/gwt/issues/9840.
Your email title says that this is a compile time infinite loop, but then
the body suggests that it was a runtime error. If it were to be exhibited
at runtime, it would almost certainly be a stackoverflow rather than
looping forever (barring some sort of tail call optimization). The actual
loop that you're seeing is waaay up the stack in
at
com.google.gwt.dev.jjs.JavaToJavaScriptCompiler.optimizeJsLoop(JavaToJavaScriptCompiler.java:1001)
where the compiler decides to optimize until it reaches your optimization
level, or until nothing changes. While SDM stands for "Super Dev Mode", it
can also be understood to mean "Super Draft Mode", so the compiler builds
as quickly and cheaply as possible, letting your app escape with very
little optimization. This means that in SDM, you will not get stuck in this
loop - the optimization loop won't run at all (see one frame up,
shouldOptimize will return false), and you'll instead experience a
stackoverflow at runtime.
I didn't continue investigation of the problem further yet, but the linked
ticket does have some analysis to consider.
On Monday, January 22, 2024 at 8:30:50 AM UTC-6 Paul Robinson wrote:
> I just found an infinite loop while running the GWT compiler.
>
> There was a trivial bug in my code which resulted in an infinite loop at
> *runtime*. This is a method that was calling itself recursively. It was
> inside a generic class, and the method had a single line that was something
> like this:
>
> public class A extends C {
> public static A getA(D d, E e, F f) {
> return getA(d, e, null);
> }
> }
>
> I have been running in dev mode with it like this, but not hitting this
> code so I didn't notice the infinite loop.
>
> Wanting to test GWT 2.11.0, I switched from GWT 2.10.0 and did a full GWT
> compile. The interesting thing is that the GWT compile also hit an infinite
> loop. Or rather, it was apparently infinite. I stopped it after 50 minutes,
> where it would normally complete in about about 90 seconds. I dropped back
> to 2.10.0, and found the same behaviour. So it's not caused by the new
> release.
>
> Fixing the bug in my code meant it then compiled properly (in both 2.11.0
> and 2.10.0).
>
> Is this interesting enough to warrant further investigation? This is code
> inside a large application, so isolating a simple example that demonstrates
> it might not work easily.
>
> FWIW there's a stack trace taken while stuck in the loop, compiling with
> 2.11.0 here: https://pastebin.com/qckpswRD
>
> Paul
>
>
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