RFR: 8323664: java/awt/font/JNICheck/FreeTypeScalerJNICheck.java still fails with JNI warning on some Windows configurations [v3]

[Phil Race]

On Wed, 31 Jan 2024 06:12:28 GMT, Christoph Langer <clanger at openjdk.org> wrote:

>> src/java.desktop/windows/native/libawt/windows/awt_Debug.cpp line 158:
>> 
>>> 156:     // be on the safe side and avoid JNI warnings by calling ExceptionCheck
>>> 157:     // an accumulated exception is not cleared
>>> 158:     env->ExceptionCheck();
>> 
>> So, this doesn't actually do anything but avoids JNI warnings, does it?
>> 
>> `AwtDebugSupport::AssertCallback` can be called *at any time*, hence calling JNI functions here is unsafe. Adding `env->ExceptionCheck()` doesn't change anything.
>
> Yes. However, it's "only" in the assertion callback that only exists in debug VMs. And an original exception isn't lost.

Perhaps what we should do here is
if (ExceptionCheck) {
 ExceptionDescribe
 ExceptionClear
}
So someone can "see" [yes, this means it isn't propagated but we've printed it and we have the assert coming up anyway] the text of the original exception, and the debugging code is safe to make the calls it wants.

The alternatives are that the debugging code in the case of ExceptionCheck==TRUE just do what it takes to silence the JNI warnings , assuming that TRUE is never not a possibility, so no real problem, but I don't know see how we can be sure about that for ALL callers of this assert code. (BTW I wonder if the reason the current code didn't do as expected is because ExceptionCheck isn't doing what we expect, but I don't see how), or alternative number 2 is that the debug code simply bails in the face of a pending exception, ie
if (ExceptionCheck) {
   return;
}

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PR Review Comment: https://git.openjdk.org/jdk/pull/17404#discussion_r1483820054