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<p>Glavo's suggestion is correct. If you want the method handle call
to apply the maximum set of conversions, you should use
`invokeWithArguments`.</p>
<p>The price to pay is that, the further you move away from
`invokeExact` the slower the method call will go (because of the
conversion code than needs to surround the code itself).</p>
<p>Also notice that, with your approach, the method handle wrapping
the function is not static final (it is final, but not static).
This means it is not a true JVM constant. This means your method
handle call will probably not be inlined very well. Wrapping with
a record instead of a plain class might be better because records
fields are trusted. So if you wrap a method handle in a
NativeMethod _record_ and then you stick the record instance in a
static final field somewhere, that _should_ work as expected
(waving hands furiously).<br>
</p>
<p>Anyway, of course all the above doesn't mean you shouldn't do
what you are trying to do - if performance is not a concern for
you then your approach is totally reasonable.</p>
<p>Cheers<br>
Maurizio<br>
</p>
<div class="moz-cite-prefix">On 27/09/2023 10:29, Glavo wrote:<br>
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<blockquote type="cite" cite="mid:CAJL5A3k-EsVPa97JwVxwH=bH18trZyw2OJHGzRLHVshB-4A6CA@mail.gmail.com">
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<div dir="ltr">See MethodHandle::invokeWithArguments.</div>
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<div>Glavo</div>
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<br>
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<div dir="ltr" class="gmail_attr">On Wed, Sep 27, 2023 at
5:14 PM tison <<a href="mailto:wander4096@gmail.com" moz-do-not-send="true" class="moz-txt-link-freetext">wander4096@gmail.com</a>>
wrote:<br>
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<blockquote class="gmail_quote" style="margin:0px 0px 0px
0.8ex;border-left:1px solid rgb(204,204,204);padding-left:1ex">
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<div class="gmail_default" style="font-family:arial,sans-serif">I'm using OpenJDK 21
and prototyping FFM APIs.</div>
<div class="gmail_default" style="font-family:arial,sans-serif"><br>
</div>
<div class="gmail_default" style="font-family:arial,sans-serif">Instead of passing
the MethodHandle returned by linker.downcallHandle here
and there, I'm trying to wrap it into a NativeMethod
class:</div>
<div class="gmail_default" style="font-family:arial,sans-serif"><br>
</div>
<div class="gmail_default" style="font-family:arial,sans-serif">public final class
NativeMethod {<br>
private final String name;<br>
private final FunctionDescriptor descriptor;<br>
private final MethodHandle handle;<br>
</div>
<div class="gmail_default" style="font-family:arial,sans-serif"> public Object
invoke(Object... args) throws Throwable {<br>
return this.handle.invoke(args);<br>
}<br>
}<br>
</div>
<div class="gmail_default" style="font-family:arial,sans-serif"><br>
</div>
<div class="gmail_default" style="font-family:arial,sans-serif">But it seems the
varargs pass through is not quit fluent:</div>
<div class="gmail_default" style="font-family:arial,sans-serif"><br>
</div>
<div class="gmail_default" style="font-family:arial,sans-serif">java.lang.invoke.WrongMethodTypeException:
cannot convert MethodHandle(int)int to (Object[])Object<br>
<br>
at
java.base/java.lang.invoke.MethodHandle.asTypeUncached(MethodHandle.java:903)<br>
at
java.base/java.lang.invoke.MethodHandle.asType(MethodHandle.java:870)<br>
at
java.base/java.lang.invoke.Invokers.checkGenericType(Invokers.java:541)<br>
at
io.montumi.datafusion.core.NativeMethod.invoke(NativeMethod.java:22)<br>
</div>
<div class="gmail_default" style="font-family:arial,sans-serif"><br>
</div>
<div class="gmail_default" style="font-family:arial,sans-serif">While if I public the
handle and call invoke from the handle directly, all the
behavior is expected.</div>
<div class="gmail_default" style="font-family:arial,sans-serif"><br>
</div>
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<div><font face="arial, sans-serif">Best,</font></div>
<div><font face="arial, sans-serif">tison.</font></div>
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