Thanks for calling this out - it has been reported as
https://github.com/gwtproject/gwt/issues/9840 (and earlier), and as time
permits I've spent some effort trying to better understand it and fix it.
TL;DR: The code here is harder to read than usual due to some questionable
variable naming choices, but seems rooted in an attempt to optimize by not
running all of the JsInliner on the entire program, resulting in missing
cases like this. I have a patch that appears to fix it (and makes sense
logically), and is just missing some tests to be sure.
Part of the problem here for code that never converges is that the
compiler's "optimization level" tracker believes that "9" is the largest
numbers can get - when counting compiler passes. That is, if you ask for
the max optimization level, that value is "9", and if after 9 passes the
compiler hasn't converged, it will keep going. Some quick testing suggests
that 8-11 passes seems "pretty good as a max", but I think this means the
max should have been 99 (or higher) so that at some point it actually gives
up. No error is required here, just "stop, this is pointless" - and
likewise, no timeout.
There's technically another heuristic that the Java optimization loop uses,
checking if the number of nodes changed/removed is higher than the required
baseline rate:
float nodeChangeRate = stats.getNumMods() / (float) lastNodeCount;
float sizeChangeRate = (lastNodeCount - nodeCount) / (float)
lastNodeCount;
if (nodeChangeRate <= minChangeRate && sizeChangeRate <=
minChangeRate) {
break;
}
https://github.com/gwtproject/gwt/blob/552c72eaa555a521d2e242d277273217704c1ed7/dev/core/src/com/google/gwt/dev/jjs/JavaToJavaScriptCompiler.java#L1440-L1444
Unfortunately, once you've hit "9" as your optimization level, this is
fixed at "any change at all is good, keep going".
Further, even if we did have a slightly higher baseline rate configured,
the JS optimization loop only counts passes, not change rate:
if ((optimizationLevel < OptionOptimize.OPTIMIZE_LEVEL_MAX && counter
> optimizationLevel)
|| !stats.didChange()) {
break;
}
https://github.com/gwtproject/gwt/blob/552c72eaa555a521d2e242d277273217704c1ed7/dev/core/src/com/google/gwt/dev/jjs/JavaToJavaScriptCompiler.java#L1004-L1007
And as it happens, that's where the bug is, in optimizing JS, not Java.
I've mused about adding a timeout option also, something like "whatever
you've gotten done in 30s is good enough, give up", but the use case is a
little weird - impatient devs who still want optimized code, and
nondeterministic (but still correct) output? Seems like a recipe for
frustration, but that's just my two cents.
As part of this and some other optimization pass enhancements, I'm hoping
to improve both how we collect metrics on the compiler performance and how
we debug the work it actually does, so that we can more confidently make
changes in this area, or at least make it easier for users to report what
they're seeing without sharing their entire codebase.
On Wednesday, November 5, 2025 at 1:27:03 PM UTC-6 Michael Joyner wrote:
> Hello all,
>
> I had a recursive setter get created while switching a field’s name.
>
> I ended up with:
>
> public void setSearchTerm(String searchTerm) {
> setSearchTerm(searchTerm);
> }
>
> And the gwtCompile just stops and sits there… (I presume after a very very
> very very long time it would error out?)
>
> Is this a known bug? Feature?
>
> -Mike
> ​
>
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